200mm Lens Shootout for Astrophotography

Will the new Askar Astro Camera Lens (ACL) 200mm f/4 APO dethrone my beloved Canon 200mm f/2.8 L ii? You will have to watch to find out! Get the Askar ACL200 from Agena here: tinyurl.com/askar200
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Links to other stuff mentioned in video:
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Canon 200mm f/2.8 L II: amzn.to/3BSzjEf
Lens Collar for Canon 200: amzn.to/2YYjrly
Astromechanics EF Lens Controller: astromechanics.org/ascom.html
Deep Sky Dad AF3S Askar Dovetail Kit: deepskydad.com/autofocuser/as...
Filter Step-down Rings (for stopping down without diffraction patterns): amzn.to/3pfqDUL
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Affiliate programs disclosure:
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I am a member of the High Point Scientific, Astrobin, OPT, AgenaAstro, eBay, and Amazon affiliate programs. Product links in my video descriptions are typically affiliate links, which means, at no extra cost to you, I will make a commission if you click them and purchase something. I also have working relationships with the following companies/brands to receive products to test: High Point Scientific, QHYCCD, Venus Optics, Astrogear.net, Night Sky Camera, Hunt's Photo & Video. I do not review products for money and any brand deals will be fully disclosed. If you have any questions about any of this, please get in touch.

[@paulsirens7259]

The best endorsement for this product was your purchase of it, much respect for your knowledge :)

[@douglassmith1215]

It's worth mentioning that there are two kinds of chromatic aberration (CA): axial CA and transverse CA. Axial CA causes red to focus at a further distance than blue. This causes the red fringes around the bright stars at the centre of the frame. Transverse CA causes red light to be deflected more than blue light and therefore leads to the red fringe on the outside of stars near the edge of the frame. Both of these can occur at the same time and in principle both can be fixed with monochrome imaging. For axial CA, you refocus for each colour. For transverse CA you need to geometrically rescale each colour (i.e. shrink the red image with respect to blue) in order to bring them into alignment. This transformation can be tricky to do the first time but then should remain constant for each lens.

[@michaelkent7333]

Can the transformation be done automatically in pixinsight?

[@dztrbdgod]

Is it possible to do automatically?

[@douglassmith1215]

@@dztrbdgod I'm not aware of an automatic way, but perhaps a program exists for this. Maybe as an add on for an existing astronomy software program. Worth looking into.

[@afryhover]

Outstanding video Nico. The Askar seems like a great value with its special Astro “mods”. Dovetail, guide scope mount, coarse and fine focus and the filter adapter! That’s awesome. I want one. Also, I’ve been a very happy customer of Agena Astro for years! Well done. Cheers Nico!

[@joseantonioalvarez3296]

Very interesting, fantastic explanation and clarifying pictures thanks for the video.

[@johnd5244]

I just started looking at that lens yesterday. I like the price value and ability to change it to other camera systems as I have both Canon and a Nikon Z6II. Thanks for the tip on step down rings. Can’t wait for a follow up review on this lens

[@victormultanen1981]

such a cool review! I appreciate your effort.

[@patlopez2093]

Your explanations and rationale are very clear and well articulated. Thank you!

[@jacobperzan6544]

Regarding autofocus, something else to consider is that some astro software allow your canon ILC to run the autofocus routine similar to the autofocus adapter, thus eliminating the need for an external electronic focuser. Something worth considering if you're doing both regular & astro photography.

[@RayGarza-sr3zj]

Fantastic lunchtime viewing. Much to think about especially on the focusers mentioned for each lens.

[@Martincohenphoto]

Thanks Nico - so clear and to the point!

[@justindame]

Nico, I also have the Canon 200mm and love it. But this is very interesting. I will say one thing that I do not like about the canon is lack of simple options to mount accessories to the Canon. The addition of the guide scope shoe is amazing on this lens. Wish they had this a while ago! Great video as always, hope all is well my friend.

[@ShevillMathers]

Thank you for sharing your comparisons between bothering optics. Like you mentioned, I also have Canon lenses along with the separate focuser unit-(very handy) for the reasons mentioned. I bought my Askar 200 f/4 with the ZWO electronic focuser mount kit, which is a great addition and available as a standard option. I plan to use this kit on a Sky Watcher az got mount, with various ZWO cameras and other cameras- should make a nice portable go-to rig. Greetings from Tasmania Australia.😁🇦🇺🦘

[@CuivTheLazyGeek]

Thanks for this Nico! Excellent video! Your Askar sample was definitely much better than mine, which is now being sent back for examination/repair :)

[@NebulaPhotos]

I saw that, hope they can repair or replace for you!

[@peterlaubscher3989]

Many thanks, great video and review. Confession: I stick my Baader filters to the back of my EFS lenses with Press-stick - it works after a fashion.

[@michael.a.covington]

Very useful! I also have an Askar 200/4 and really like it.

[@AstroQuest1]

Nice review Nico. If I did not already own the Canon 200mm f/2.8 I would consider the Askar, however, I don't think it is enough better to make that change. - Cheers Kurt

[@adityakinjawadekar562]

Nice video Nico!

[@mouseylikesnuts6437]

Loving your videos; very down to earth, informative and easy to watch. I feel the need to pick you up on one point made in this video about "bad vignetting" from adding a 2" filter to the front of the Canon 200mm F2.8L using stepping rings. Owning a 5D MKiv in a BortIe 7 area I have been forced to do this as EOS clip-in filters aren't an option. I used a cheap(ish) Castell 2" UHC filter, the holder being quite thick. To my surprise at F4 the vignetting was really nothing to be concerned about on this lens. It was worse on the 100mm macro! Am not sure how or if I can post a link to a light frame here but I will try if anyone is interested. Keep up the great work and clear skies!

[@alanalain4884]

Hi Nico... Great video as always. (And so many hours of great learning content that I wanted to dip in and joined your "Seagul" Patreon). You create such an enthusiastic and helpful content for beginners and advanced alike, even taking the time to try to answer many questions when it's so time consuming, thank you, and hats off to you. I had a quick question if you have the time. I was wondering, now 2 years later thiis video and seeing that you have the Redcat51 for some time, would you say that the Redcat IQ is better than the Askar's ? Or the Askar having a stong point over the RedCat, aside of weight, and wider, adjustable aperture ? Thanks if you have any insight... (although seeing your Redcat rigging video might tend to give an answer on that, but not sure... ) Also, and this is a weight consideration for small trackers, do you see any advantage on the RedCat coming with the 210mm dovetail vs the 110 mm they had at first, when used with small trackers (Skyguider pro and alike) ? For this longer dovetail makes the whole like 4 or 5 Oz heavier, when the RedCat51 seems already heavier than any lens with that focal length (even the bieffy Canon 70-200 f/2.8 at almost a pound less). Cheers, and clear skies...

[@carlosrojasrodriguez930]

Wow! 91k subscribers. The astro community id growing at an exponential rate! Lol congrats

[@prabhakarrao4922]

Absolutely amazing comparison. Unfortunately my copy of the Canon 200mm has really bad purple fringing in Astro shots which is a great pity as it is quite satisfactory as a landscape lens during the day.

[@derikhaggard4666]

I think it would be interesting to have a shootout between this Askar and the TPO/Askar 180mm f4.5 triplet apo.

[@samologin8038]

I have owned ACL 200 for a few months. I have obviously received a bad copy that suffered from astigmatism on the right part of the frame. I have used it for a while to know if I want a new copy of this lens or not. And I have decided not to, as before sending it back to the retailer it happened for the second time that I was not able to remove the filter and it looked as I will need to send it back with my Triad Ultra inside! The reason is that thread of the back filter adapter is constructed in a way that it is sensitive to temperature changes. If you gently screw it when warm, you will need Hercules strength to remove it when cold. So I decided to give WO RedCat a try, as about 200mm is really a good focal length and there are not that many options among telescopes.

[@astrolux3603]

Great video , the best comparison would be the Askar 180mm version (half price of the 200) , might be interesting ?

[@jacobperzan6544]

Thoughts on using the skywatcher evoguide 50dx with the Starizona EvoFF v2 field flattener as filling a similar role to these lenses/ a Redcat? FPL-53 doublet and with the FF it should be good up to APS-C image sensor. At $400 it seems interesting.

[@Neanderthal75]

I have the EvoED50 and starizona FF and it's excellent, but the focuser leaves a lot to be desired. Also the 50ED is 50mm at F4.6-- so the Askar is 60mm aperture so sharpness/clarity might be better on the Askar. Also I haven't tried the 50ED with a APS-C sensor, neither with a full frame. I suspect there would be more vignetting with both, since even with the ASI533, I was seeing vignette in the corners and that's a 1"x1" sensor. Also the SW 50ED needs a 42 to 48mm adapter ring if you gonna use 2" filter in the imaging train (or you use 2" spacers) , my camera came with one that adds zero distance so I use that one. Also, there is no way to attach a guide camera to this "guide camera", so it's up to being clever with either a 3D printer or piggy back the telescope with another telescope or similar. Another minus, there is no way to rotate the camera, once you attach it to the FF. You either rotate the whole thing in the holding rings, or don't rotate or you buy a rotator and implement it in the backspacing between the camera and flattener. On the plus side, the telescope is cheap, but it's an APO and produces no chromatic aberration whatsoever so the lens are excellent qualitty (FPL-53) and will produce sharp/pinpoint stars at 225mm (with the asi533 -ASTAP reported 250mm) So, my 2 cents about the pluses and minuses regarding the SW 50ED

[@TeamGamingSWE]

Considering getting the 180mm version of the askar. Very cheap scope but seems like it performs good.

[@UnderDriven17]

With the Canon lens a teleconverter can be added to increase focal length. Since your Canon lens already has some CA it would be magnified by the teleconverter, so it probably wouldn't be very useful. Is it possible to add a Barlow lens or a Tele Vue Powermate to the Askar? If so, how does it affect optical performance?

[@88mixture88]

Good advice if you have a deep pocket. In my case, I'm a bottom dweller and use lesser expensive items. For now I'm happy with the old Canon FD 200mm f2.8 lens that is manual focus. It's best paired to m34 cameras because the lens adapter doesn't have a lens corrector. Unfortunately the FD lens adapters to DSLR cameras have a lens correcter that adds color and spherical aberrations. There is a slight color aberration with that Canon lens but I can reduce that in GIMP. This lens can be bought in eBay at a fraction of the cost of the above mentioned lenses.

[@michael.a.covington]

Three very affordable 200-mm lenses that adapt well to DSLRs are the Pentax Takumar 200/4, Olympus Zuiko 200/4, and (uncommon but good) Olympus Zuiko 200/5 (very lightweight, good to use on star trackers). But I agree with the video -- the Askar 200/4 is excellent and beats the Canon 200/2.8. Both of them are leagues ahead of the Nikon 180/2.8, in my experience.

[@AndreasHoecker]

@@michael.a.covington I also use the takumar 200 f4. As well as the 135mm F2.5.

[@magicbeans6153]

Tair 3 lens....

[@christopherbaker8621]

I really like the focus locks and 2" filter option.

[@NebulaPhotos]

Yep, 2" filters option is really nice. I get tired of clip-ins as they lock you into a particular type of camera. And the focus locks are also a really nice touch.

[@timliscum2861]

ya the 2" filter option is everything.. but I already have a spacecat 51 so cant justify it........ yet lol

[@victorpablo4636]

Given a choice between this Askar 200mm f4 and their 230mm fma or 300 fra, which do you recommend? Thanks for your reviews!

[@Jcorban08]

Thanks for the very helpful and informative video! Does c.a. disappear, or greatly reduced, with narrowband?

[@NebulaPhotos]

Greatly reduced, it may still lightly effect star shape, but I've never found it to be annoying like with broadband.

[@BikerInAHat]

Was going to buy and see up at Agena Astroproducts the ACL200 is discontinued but a new version is due in Sept!

[@beachbum9869]

I am new to astro photography.. I am just working on my setup. I have been looking at 200 mm lenses. With your experience and knowledge base, in your opinion would this be a good lens to start off with. I am still trying to figure out which camera to use. I am looking at the 6D Mark ii and the Z6 ii. Astrophotography is something I have wanted to do since I was in High School many years ago. Any, great video i always enjoy and learn from you. Thanks. Have fun, stay safe and stay healthy. Clear skies

[@NebulaPhotos]

Pretty good start. You could save on weight and $ with the Rokinon 135 f/2. It being faster is also good if you'll start with just tripod based astrophotography

[@CkelOneProd]

What is better for you? a lens like the Askar or a 60/360ED for a Star adventurer set up? Thanks for this review its always good to know differences between stuff 😊👍

[@NebulaPhotos]

I'd go for the 200, 360 is doable on a tracker, but a bit of a pain (I needed extra counterweight and very good polar alignment to make it work)

[@danielm4703]

Hi Nico - did you come up with a mounting solution for the Askar lens? I have one on the way and I'm concerned about how I'll be able to attach my USB hub and Pegasus powerbox to it. The guide scope will go in the shoe on top but I don't know where to put my other accessories. I only have a Vixen saddle for my mount right now so using a big Losmandy plate isn't an option.

[@NebulaPhotos]

Yeah, get a longer vixen plate and a vixen saddle and mount the Pegasus and USB hub to the saddle attach it on the front (under slung). See my Pleiades battle with Cuiv. I show it in the first few minutes.

[@N4GW]

I hope you do a video of actual photos of nebulas with the scope

[@flyingmedic]

Nico or any other person that can answer my question. I have a canon 70 to 200mm F4 lens. Is there any point in me buying a redcat 51 at 250mm?

[@patrickpat5277]

Need to know if for a beginner like me, to have better results, on a Canon DSLR camera (not modified), using a Canon 200mm or Askar or Samsung 135mm in comparison to use a little Apo telescope (66mm or 72mm) to be mounted on the Star Adventurer. So is it better the photografic tele zoom or the little apo telescope in your opinion?

[@NebulaPhotos]

Any of those could be good. Do you have a star tracker?

[@barfoo100]

Re autofocus on the canon lens, does it work with ascom DSLR driver to your EOS-Ra? It does with KStars/Ekos/Indi driving an EOS-R.

[@derikhaggard4666]

Glad I'm not the only one with bad CA issues in the Canon 200mm.

[@eugeniosegabinazzi9880]

Great video! I can't understand how it is possible to get chromatic aberration with a mono camera on the canon lens: if you focus properly every time you put the filter for each channel (RGB or astro narrowband filters) there is no way you get halos on stars. If that happens it means that the lens cannot reach infinity focus on red (not possible)! The inability of the optics to focus all three colors on a bayer matrix at once becomes irrelevant once you properly focus with mono+filters, right?

[@NebulaPhotos]

I wish it were true but this is an incorrect notion. Chromatic abberation results in a bloated spot size on the stars for certain wavelengths AT BEST FOCUS, so you still get fringing with mono and RGB filters. The idea that chromatic abberation disappears with mono and we can just buy very cheap achromats is something I hear over and over again on the internet that is just not true unfortunately.

[@eugeniosegabinazzi9880]

@@NebulaPhotos thanks for the clarification! :)

[@marcelomunoz84]

Excellent video like all the above. I have a query, I have tried to take a photo with the Askar 200 and a Canon EOS R camera, but it was impossible since the shutter does not work. Is there any solution?

[@NebulaPhotos]

Yes, go to the menu and find custom function 5 menu (orange) and change 'release shutter w/o lens' to ON

[@marcelomunoz84]

@@NebulaPhotos I went through the whole menu and didn't see it, I feel like a fool. Thank you.

[@DJBastor]

nice video. i got the 200mm canon lens too. What is that black bracket for it

[@NebulaPhotos]

Vello (3rd party) lens collar: amzn.to/2YYjrly It's not the best, but the Canon one is 3x the price

[@johnnoble1967]

Great video Nico. Just wondered if you have tried the Canon at f 2.8 with 7 nm filters I had good results a few years ago with a 12 nm Ha but just tried with my ASI6200 and a 7 nm ZWO Ha and it captures almost no nebulously. I’ll be trying it stepped down next but wondered if you’d seen anything similar?

[@NebulaPhotos]

Must be the quality of the filter and how the bandpass is centered, whether or not it is flat top, etc. I ve used 3nm Astrodon filters at f/2.8 a ton with my Canon 200mm and had no issue. Astrodon says they will work well down to f/3. There are a lot of factors with narrowband filters beyond just the bandpass width, but unfortunately the only filters I've found to be truly superior have a price to match.

[@johnnoble1967]

@@NebulaPhotos Thanks for the quick reply that is good to know - I'll have to decide stop down or buy new filters!!! Any thoughts on the Baader fast filters vs Astrodon?

[@NebulaPhotos]

@@johnnoble1967 No thoughts as I haven't used the Baader fast filters. If I remember correctly, Cuiv (another astro youtuber) tried them and had issues with his set.

[@astrophotographysometimes2303]

You mentioned that there is an internal iris with a number of aperture blades. Do all lenses have internal irises? I never see diffraction spikes with my lens, I use a EF 70-300mm f/4-5.6 IS II USM lens. Am I doing something wrong?

[@NebulaPhotos]

Yes, but should have been clearer there. Lenses are designed such that if you shoot wide open (f/4 in your case) you will see no diffraction spikes. It's only when you start stopping down that the iris extends into the light path and creates the spikes

[@tasaki12]

quick question once again. can you put an efw on the acl???

[@439956]

@Nebula Photos , Nick correct me if I'm wrong but you could just run the RAWs from the Canon lens through something like LightRoom and just use the Lens Correction function to just remove all chromatic aberrations from images , I mean that should be something like 5-6 clicks worth of work since the Canon lens is recognized by Light Room and it knows how to correct it ; EDIT: Granted LightRoom will not export it back to raw (doh!) but it can export it as something like TIF which would also speed up stacking if you're using DSS

[@NebulaPhotos]

As soon as you open a raw file in Adobe Camera Raw or lightroom you are applying a non-linear transformation that makes proper calibration (Darks and Flats) impossible. Doesn't matter that you can save as tiff as that tiff is stretched by the raw converter and all linearity of the data is lost. I can run the chromatic abberation lens correction tool after stacking with Camera Raw Filter, but it subtly destroys data by filling in something that isn't really there because the fringing around the stars is baked in to the original data. I still do it, but if you really care about star shape and the stars being as pretty as possible not having CA in the first place goes a long way.

[@mastersox4408]

yeah you can just first stack the raw files and then edit and remove the chromatic aberration

[@439956]

@@NebulaPhotos Thanks Nico! I was so focused on the aberration part that I didn't stop to think what happens if you open them that way. Always done it after stacking but never thought about what would happen to the data if done before stacking. Cheers man, thanks for the wisdom nugget!

[@GulliNL]

Thanks for this review! I have a Canon 70-200 2.8 IS USM II as I am a daytime photographer. Have you ever tried this (type of) lens for Astrophotography? I realize it wont't be as sharp as a prime lens, certainly around 200mm, but still, it's the best lens I own right now. Any thoughts?

[@NebulaPhotos]

That is one of the best zoom lenses for astrophotography out there. I think it's one of the few that is nearly as sharp and well-corrected as a prime at 200 from the samples I've seen. Definitely try it, and let me know!

[@calimark7448]

@@NebulaPhotos This is the lens that I'm using right now. It's pretty good at 200mm, but getting the thing in focus is a real pain... Also CA at the corners... not so bad on my ASI2600MC as on the 5DMk3 that I started on. The full frame does you no favors as the corners of the Canon lens are really bad at full frame. Clear skies for you all.

[@gregerianne3880]

Great video - and product review, Nico. Love this lens, but I have an APS-C Canon and I don't think this would be great for astrophotography with that type of camera (at an effective focal length of 320mm) . Do you agree, or do you think the lens would work okay on some DSOs with an APS-C?

[@mif1118]

APS-C together with a 200mm lens will work fine for a lot of DSOs.

[@gregerianne3880]

@@mif1118 Thanks so much! I appreciate the input and the info.

[@hbmike47]

@@gregerianne3880 It depends entirely on what mount you are using, your seeing conditions and if you are using guiding. For unguided wide field astrophotography the Rokinon 135 with an APS-C sensor is a good match for use with a simple star tracker and at 216 mm is about the same effective focal length as this lens with a full frame camera. You may find that at 320 mm you need to be much more careful about precise polar alignment and may find that you need to limit exposure times. A good experiment to see the effect is to use the typical Canon kit zoom lens (75 -200) that you may already have at hand or can borrow and see how the tracking performance is at various focal lengths with your mount and tripod or the limits you reach with exposure time before making the decision about a prime lens purchase. The advantage of these fast prime lenses is only in how they compensate for lack of exposure time afforded by lightweight portable tracking mounts rather than a small yet fully featured equatorial mount. The answer to your question lies really with "what do you want to do?" . If you backpack and want a portable system that you can take with you the answer is different than if you want to car camp and can take more equipment and have more power available to run it and that is different still than if you want something that you will use in your backyard and not transport. Then there is another question. Do you want a system that you also use for daytime photography or is it dedicated to astronomy? I think Nico touches on that in this comparison.

[@gregerianne3880]

@@hbmike47 All great thoughts, Mike. I don't have a Canon kit zoom, but I may be able to borrow one. That's a really good idea. For right now at least, my primary interest is in night/astrophotography. Terrific food for thought here. Thanks so much!

[@scottrk4930]

Hi Nico . How is the Askar connected to your Canon DSLR ? Do you order it with a Canon Adaptor or do we need the Astromechanics EF Controller ? This could get very expensive quickly ./SRK

[@NebulaPhotos]

Hi Scott, not the Astromechanics is only for dedicated astronomy cameras. For my Canon DSLR, I just use a normal 48mm -> EOS T adapter like this: www.highpointscientific.com/apertura-48mm-canon-eos-t-ring-adapter-eos48

[@eurekasavoirscience4687]

Thank

[@deltacx1059]

3:32 than again f/2.4 is super hard for dedicated twlescopes so id say its pretty good

[@hbmike47]

Hi Nico, Interesting review and an interesting spot in the spectrum of useful optics for astronomy. Kinda nice cozy arrangement you have with Agena Astroproducts to have this review of the new version of the ACL200 appearing on their website as a video in with the group of pictures in the product description. I'm sure you appreciate the additional traffic it may bring to your KZbin Channel. Your disclosure failed to mention that your review is being used for marketing purposes by Agena and ASKAR and that it's presence as an embedded link drives additional traffic to your KZbin channel to your benefit. You only mentioned that they "loaned you the lens" for review, and that you "purchased the lens" after reviewing it but without revealing any discounts they may have provided as incentives. Please be aware that your loyal following here on KZbin notices such things. ok... no more jackels 😁

[@NebulaPhotos]

Hi Mike, Here is how I approach product reviews on my KZbin channel: kzbin.info/www/bejne/iKexY5dvrLGFaas If a company I'd potentially like to work with doesn't agree to that review policy, I won't work with them. As regards to Agena embedding the video on their website, anyone can do that. Embedding is 'on' for all my videos and all my videos are licensed under a CC BY license. For this video alone, I can see several websites have embedded it including an article on fstoppers.com. In the end, views from sources external to KZbin make up less than 1% of my views so don't make much difference to the success of my channel. The main reason I choose to work with Agena, High Point, OPT, QHY, Hunts, etc. is the access to loaner equipment for review. In this case, I did like the lens, so after reviewing it, I bought the copy I had from Agena as mentioned in the video. If you have any questions or concerns about my review policy, you are welcome to leave them here in the comments or email me at nicocarver at Gmail dot Com. Cheers, Nico

[@hbmike47]

@@NebulaPhotos Thanks for linking your policy. That helps a lot. I recently read a review of the lens on Cloudy Nights by Michael Covington. He did not use a full frame camera in his review. I linked your video in a comment. :) Your detailed discussion and examples of both corner and central image quality at wide open and reduced apertures is especially relevant. It's an interesting product in that it fits right next to the fast compact refractor products in focal length. With its weight it pushes the limits of tracker mounts and further blurs the point when telescope optics might be a better choice. Askar seems to be headed towards competing in the AP oriented compact refractor market.

[@brettatton]

I just went looking the EF 200mm F/2.8 II USM lens is discontinued.

[@CatchWMarcello]

Does it makes sense to you to buy this lens and shoot only from the tripod without startracker ?

[@NebulaPhotos]

Probably not. From a fixed tripod, I'd rather have the Canon at f/2.8 or my Rokinon 135 f/2 due to their faster wide open aperture.

[@Talalpro_1]

I have a question did you ever use the background telescope the 12-14-16 inch dob Also I wanna see a vid about it like astrophotography or anything

[@NebulaPhotos]

Hello, Yes, it's just a 10", but still a bear to get down the stairs. I do have a few ideas for videos with it. I used to use it a lot more when I lived on the first floor of a house, now that I'm on the third floor, it doesn't get as much use because I'm lazy. :)

[@Talalpro_1]

@@NebulaPhotos Lol I bet it’s heavy when moving it down stairs or upstairs I feel ya Almost every astrophotographer is lazy like me lol Anyways Looking forward for the future vids! Clear skies!

[@claudiogoncalves1985]

​@@NebulaPhotos maybe you shoud includ some pulleys and rope in your equipament.

[@progshark]

Regarding step down rings. I use them with an EF300MM f4. When shooting flats do I need to shoot them with the rings on?

[@NebulaPhotos]

Yes, definitely

[@progshark]

I've used them for 5 sessions and shot flats after removing them each time. I wonder if that caused my issue with white balance stacking the second night of subs on IC1396. Oh well. Thanks.

[@NebulaPhotos]

Not sure, but the goal with flats is to keep your optical train intact and exactly as you had it when you shot your lights. So never remove any lens hoods, dew shields, step down rings, filters, etc.

[@overhang88]

Hi Nico, what are you thoughts on this focal length in terms of under-sampling? Thank you, Abdul.

[@NebulaPhotos]

Under-sampling is not a major concern of mine. I have been shooting with camera lenses for a long time where 3-6+"/px is common and I enjoy getting these wide fields of view quickly. If the close-ups on the stars I showed in this video looked unacceptable to you than go for a longer focal length as you aren't going to get much better at 200mm. I also enjoy making mosaics at a more traditional 1.6"/px (450mm f.l.), and these take much longer to complete. For me, they are just different parts of the hobby, and more about technique than a 'right way' or 'wrong way' of doing something. My 2 cents, Nico

[@overhang88]

@@NebulaPhotos Thank you for taking the time to get back to me with such a thoughtful reply. I have not shot at such short focal lengths so appreciate hearing your 2 cents on the topic! p.s. the stars look perfectly acceptable to me, perhaps all just a case of preference.

[@saisaketh23]

Lol i am second.... yes 200mm is quite a good focal length for some decent astrophotos

[@TheOpticalFreak]

Die you use a full frame, crop frame, or micro 4/3 sensor!?

[@FOXUNE_]

I have a Russian Jupiter 21m 200mm f/4 lens. Do you think it will be suitable for astrophotography? Or is it better to buy something better?

[@NebulaPhotos]

No clue, I recently bought a 300mm TAIR soviet lens that show a lot of promise, so I would definitely suggest try your Jupiter on the stars before buying anything new. :)

[@FOXUNE_]

@Денис Ковалев thank you!!

[@NebulaPhotos]

Yes, I plan to, but it might be a few months as I have a backlog of videos to finish

[@AndreasHoecker]

@@NebulaPhotos looking forward to this.

[@MickyMouseLimited]

Can you use software to correct the chromatic aberration.?

[@NebulaPhotos]

To some degree yes, but it's not perfect. The easiest method to try is the 'de-fringe' sliders in Adobe Camera Raw filter.

[@gregerianne3880]

I was wondering if you've ever tried a catadioptric camera lens for astrophotography. Their smaller size and lighter weight, as well as the ability to get to a high focal length, seems to solve a couple of problems for those of us using limited-payload capacity star trackers. Don't see any reviews by astrophotographers, though, and I'm wondering why. Thanks!

[@NebulaPhotos]

I haven't. They are sort of in a weird spot for me since at 500 or 600mm focal length and slow f/ratio you'd need very good tracking like that offered by a sturdy equatorial mount, but if you have a good EQ mount why not just get a telescope which will have better performance on the stars than a mirror lens.

[@gregerianne3880]

@@NebulaPhotos Excellent points, especially regarding the telescope instead. I found some comments at B&H Photo about photographers who've used these, and apart from them being a little soft, having 'bubble-bokah' (Wha?!) in some cases and being slow (and fixed), I didn't see anyone commenting about their use with astrophotography. So, I'll definitely pass on those. Thanks so much for the input!

[@hbmike47]

@@gregerianne3880 Bubble-bokah - the effect of the secondary mirror being a central obstruction when you have light sources that are out of focus. The central obstruction causes a 'donut' or ring shaped effect.. ala 'bubble' on light sources that are out of focus. Bokah refers to the out of focus 'blurry' part of a photographic image ahead or behind the subject focus plane. That characteristic of the mirror system is of little concern to when shooting images of stars at infinity focus. The advantage of mirror based optical systems are freedom from CA and larger apertures at reduced size, weight and cost than comparable refractive optics although mirror optics have their own issues. I agree with Nico that once you are at these longer focal lengths you need a good equatorial mount and at that point would get better performance from a telescope purpose built for astronomy rather than optical systems designed for general photography. Mirror and refractive optics both have their strengths. I'd hesitate to characterize one as better than another, but rather that they are simply different and choice depends on which is better suited for the intended application.

[@ShevillMathers]

@@NebulaPhotos My experience with catadioptric lenses has been disappointing, very slow and severe vignetting, also not as sharp as I would have hoped. Greetings from Tasmania Australia 😁🇦🇺🦘

[@galbanese7329]

Great Video, thank you! At 200 mm, how do either of these lenses compare to the William Optics Redcat?

[@NebulaPhotos]

I've never used the Redcat, but it's slightly more 'telescope-like' than these with a fixed aperture of f/4.9, meaning it has no internal iris. Other than that and the slightly longer reach (250mm), I think they are pretty comparable. I'll probably get a Redcat eventually to test, but from what I've seen looks like a winner.

[@MrPixelspin]

I wanted to ask exactly the same question! I've tested my RA with the RF 70-200 and while I do get pretty decent results there are enough drawbacks to be looking for something else. The Redcat is high on that list and the Askar 200mm f/4 has now joined that list.

[@galbanese7329]

@@NebulaPhotos Thank you. Sorry about asking about the Redcat before I got to the end of the video where you addressed that.... I just picked a redcat (my early Christmas present :- )....lol) I am going to give it a first light/test run this week if the cloud gods will cooperate....

[@NebulaPhotos]

@@galbanese7329 Ha, no problem at all! Enjoy your redcat, I think it's a great choice!

[@galbanese7329]

@@NebulaPhotos Thanks, I purchased it to open up my field of view from my WO GT 81. I am hoping to get some great wide field photos with it. Astrophotography is really a deep black hole...that we keep pouring money into....lol

[@tankivulture148]

I recently bought a EQM 35 PRO cos of your suggestion in the astro setups video. Pointing is far off than I thought, it's basically always out of my frame (85mm in APS-C). And tracking... I was very hopeful that it would be like yours but, not even close. 30s is as far as I got sharp, I repeat, with a 85mm lens. I think, since it's my first mount, is that I messed up polar alignment (for 1 week in a row I would say). I see in my polar scope a very bright star, that would make me set my latitude wrong to get it right in the aim clock whatever it is, so even if it seem to be Polaris, it may be not. So I tried other stars that was almost in the centre of the circle or near, which I used to align. Neither of them gave me better results than the brightest star. Any suggestions to improve my tracking since you used that mount and you got it to work (and you're also way more experienced than me)

[@NebulaPhotos]

Hello, I'm not sure from your comment if you have polar alignment figured out. That is step one as everything follows from there. You need a good PA both for good tracking and for good pointing. For the pointing (go to) issue there have been some good ideas to try in the comments like doing a factory reset of the hand controller and also updating its firmware. For tracking, other than polar alignment, make sure you are balanced properly in both axes, and that everything is tightened up on the mount.

[@tankivulture148]

@@NebulaPhotos Thank you for your answer, I probably pointing towards the wrong star: I see fainter stars and a brighter star pointing my tripod to north, The brightest star, which presumably is Polaris, requires me to lower my latitude to ~45, my latitude is almost 46, but maybe it's the mount that is not that precise/calibrated? Even if I don't think so. Balancing and leveling on point. How much do you think I can get with an 85mm lens if I do a good polar alignment in terms of exposure time? And for when I get a 600mm lens, without guiding, do you think I can get at least 30 seconds if I do everything properly? Thank you for your help!

[@fernandoapausa4931]

Try with a laser pointer through the intro scope to check which star it is actually pointing to. Polaris is clearly the brightest in its surroundings. Also, you can check / fine tune your correct polar alignment with PHD2 drift alignment tool or with NINA 3-point polar alignment plug-in routine

[@tankivulture148]

@@fernandoapausa4931 If I had the possibility to buy a guide cam I would use this tool, but thank you anyways

[@NebulaPhotos]

@@tankivulture148 Yes, sounds like the latitude marking is off. Install a planetarium app on your phone and look at how the constellation should be positioned to confirm you are looking at polaris, then carefully align it to the right point on the circle. Use PolarFinder Pro app (Android) or PS Align Pro (iOS) to know the correct position for your location at the exact time/date you are doing it. With a good polar alignment, level, balance, you should be able to do 3 minutes at 85mm and 30 seconds at 600mm unguided with this mount. Keep at it!

[@indysbike3014]

I was looking for a dedicated apo doublet telescope at around 200mm but apparently that doesn't exist. 420mm was the shortest focal length I could find.

[@NebulaPhotos]

Lots of options at 360mm for APO doublets actually. I have the Astro-tech AT60ED f/6 and can recommend it. High Point makes their own version of the same scope: Apertura 60ED. And William Optics makes a version too. You can get the scope with either a 1x flattener or a 0.8x flattener/reducer that brings it down to 288mm f.l. Still have to review that scope some time, but I'm using it in a lot of my early videos.

[@jimboandthejetset1]

Might be a daft question, but the F numbers are confusing me, here! The Askar lens is F/4, whilst the Canon is F/2.8; doesn’t that mean that the Canon lens will always allow a lot more light in for astrophotography?

[@NebulaPhotos]

The Canon is f/2.8 with the internal Iris 'wide open', but many will stop that iris down to an aperture of f/4 in which case the Canon and Askar are letting in the same amount of light. But yes the Canon can do a brighter aperture of f/2.8 which I do acknowledge could be an advantage depending on your imaging style a couple times in the video

[@TR6Telos]

My Minolta 200mm 2.8 is shaking in its boots about the cold nights It will shortly see!

[@kirostar12]

It seems to me that the Canon has much better light transmission even at the same F number compared to the Askar also in terms of cleaner and sharper photos. Not to mention that it is faster and can be used during the day. The winner here is Canon without a doubt.

[@KTMAstroAdventure]

Hey Nico, i have got the same canon lens but i am struggling to find the ring to attach the lens to the dovetail. Where did you find it? thanks

[@NebulaPhotos]

amzn.to/3peDqqw Vello Tripod Collar A. It's actually really low quality for $50, but the official Canon one is $150! so I accept the low quality of the Vello. I'm only on my second one after 8 years. (The screw that locks it became stripped on the first one from too much use and cross-threading at night)

[@KTMAstroAdventure]

@@NebulaPhotos i tell you the solution i found: i attached my aspc canon camera with a proprer screw to the dovetail. everything is pretty balanced because the hood gently touch the dovetail like a sort of support making everything quite stable.

[@NebulaPhotos]

Yep, I've done the same at times and it works very well with this lens. I still prefer the collar so I can rotate the field. By screwing the camera to the dovetail you are 'locked in' on rotation angle. For many scenes at 200mm, that might be fine, but you lose out on some creativity in the planning stage when you don't have field rotation as a variable.

[@KTMAstroAdventure]

@@NebulaPhotos you are defitely right, i am planning to get the askar, so i can solve the problem once for all! I also have a 135 f2, so i keep a kens for potrait, which i love!

[@christopherbaker8621]

@@NebulaPhotos do you still have the first one? Is it possible to remove the thumb screw and buy a bolt 1 size bigger and tap the hole for the new bigger bolt?

[@kishoret3230]

Pls make astrophotography with point and shoot camera pls pls pls

[@colintraveller]

Standard Bridge .../ DSLR models ???

[@Vasiliyterkin628]

здравствуйте. я не смог в толк взять, а именно с зеркальными камерами nikon возможно использовать этот обьектив? спасибо

[@NebulaPhotos]

Yes

[@Vasiliyterkin628]

@@NebulaPhotos Спасибо. А то разрываюсь между новым телескопом или объективом хорошим. У самого есть телескопом Максутов-Кассерген 90/1000 и фото такие плохие получаются. Новый телескоп смысла нет брать за такую же цену, если есть возможность взять такой хороший объектив. Спасибо ещё раз.

[@nicedward7544]

The ef 200 is notorious for CA at longer focus distance. It is an amazing lens for general purpose for photography but definitely wouldn't be my pick for Astro. The samyang 135 mf is much better suited for Astro although not 200mm. It pretty much should be apo designated. That askar looks nice

[@JOlsson01]

If you're using the Canon lens, you don't need to auto focus because he lens will be focused on infinity and there is a mark on the barrel of the lens to indicate that. You can't turn the manual focus ring any further than infinity.

[@newforestobservatory9322]

Clearly you have not actually tried to do this.

[@JOlsson01]

@@newforestobservatory9322 I’ve done landscape photography for over 20 years. When attached to a camera, the lens has a minimum focus distance and infinity. In older lenses the focus distances will be engraved on the lens barrel. The furthest focusing distance is dependent upon the focal length. When you point a camera with an autofocus lens, the adjustment is the focus of the lens being moved to infinity. When doing astrophotographers, you can turn off the autofocus and manually set the lens to infinity. The infinity symbol is found on almost all lenses.

[@newforestobservatory9322]

@@JOlsson01 Oh dear - you really don't have a clue about astrophotography do you? Better stick to the landscape photography - it's much easier :)

[@JOlsson01]

@@newforestobservatory9322 Would you like me to post you some links so you can better understand the subject?

[@Thefuror38500]

@@JOlsson01 Infinity symbol is not precise enough to reach critical focus on stars. May be okay for landscape and such, but star will definitely be off. Even when in focus, temperature change can rip it off. Better way is to use a bathinov mask, or even better, analyse and minimize FWMH live with a software

[@1Sinep1]

Can someone explain me how much the image is altered when shooting at f2.8 compared to f4 with the canon lens?

[@AndreasHoecker]

@2.8 you will get some color fringing on the stars.

[@1Sinep1]

@@AndreasHoecker thanks for the response , is this all over the image or only in the corners? and how is sharpness affected from center to the edge at f2.8?

[@AndreasHoecker]

@@1Sinep1 this depends on the lens.

[@1Sinep1]

@@AndreasHoecker any idea or experience with the 200mm L USM II from this video?

[@AndreasHoecker]

@@1Sinep1 nope. Ask Nico

[@simrisks]

Does anybody have experience of this lens with 4/3" imaging cameras. Got back focus at 56 mm (added 1mm for filter as is traditional) and it is sadly too much. Anybody worked the numbers on this? Save me a few nights of pain!!

[@NebulaPhotos]

Adding 1mm for filter thickness is ONLY if your filters are 3mm thick. What filters are you using? You should be adding 1/3 filter thickness to the back focus calculation. What are you seeing to know it's a backfocus issue?

[@simrisks]

@@NebulaPhotos it's sharp stars in middle with progressive trailing sizes as you reach edge of frame, looks like field rotation, but it's shot on EQ mount. I have zwo filters unmounted (7nm) which I zwo suggest 1mm added to backfocus on Thier documentation. So ideally I need to measure a filter and adjust my spacings, I doubt they are 3mm thick, likely 1-2mm. Thank you.

[@keithhanssen7413]

👍🏻👍🏻

[@corybolton7462]

Dang it I was saving for a redcat51 now I have another option to not make my mind up about lol

[@NebulaPhotos]

The redcat is definitely a solid option. I've never used one, but I know lots of people who are very happy with theirs and making nice images.

[@corybolton7462]

@@NebulaPhotos it would be a great video to do a under $1000 lens/scope comparison/shootout. Maybe even sprinkle some cheaper options for comparison also. Your videos have been a great help in getting started thank you, and clear skies!

[@Leinadcpr]

Hello Nico: How can I reach you privately?

[@NebulaPhotos]

Nicocarver at Gmail dot com

[@hanimehrez9423]

Chromatic aberration can easily be removed using photoshop, pixinsight and other software apps.

[@nastasedr]

There is only one problem when you compare the lenses one is at f4 and the other at f2.8. At f2.8 fringing is more likely. Then in the second image both lenses are at f4 and guess what, no fringing.

[@andrefialho9504]

👌🏼🇵🇹

[@ahmedwaddah9391]

Wish the Askar was lighter 😁 Spaghetti Nebula huh interesting

[@dedskin1]

i dont think you are correct about aperture stop down rings , those are telescope things becase telescope has simple optics and you can use it , now a LENS does not have Aperture blades in front does it now , it doesnt , aperture blades are in optic center and that is where they have to be , put them anywhere else and you wont get Aperture effects you will just get darkening So what you are doing is shading the aperture blades the F number remains the same and you can test this and you will see that i am correct .In other words you will lose the diffraction spikes or shade them a bit but you wont get sharper image or focus change and depth of field etc..

[@NebulaPhotos]

I've tested them extensively with lenses so I am speaking with practical not theoretical knowlwdge. Stopping down with internal Iris vs. Stopping down with external step down rings has the same effect in terms of sharpening up the image and controlling abberations. There are two differences: 1. More pronounced vignetting with the step down rings. As you noted these will darken the corners, while stopping down internally has the opposite effect (less vignetting). In my experience, the vignetting is still correctable with flat fielding. 2. Stopping down internally gives diffraction pattern because the iris is not perfectly round. Stopping down with rings, the stars stay round because the rings are perfectly round.

[@dedskin1]

@@NebulaPhotos no you didnt test it my friend otherwise you would see . Stepped down lens has Deeper focus , its called Depth of field , just test it you will see you can block or shade 90% of the lens Depth of field wont increase wont change . Thats for F ratio. Now sharpness . Aperture Blades are set in the Optic center , behind the front element because their job is to cut of light at strongest angles sent by the front element and leave shallower angle light to pass , the shallower the angle the less aberration the light encounters .And you are left with sharper image . So what you are doing with Blades is removing worst light first leaving better light to pass . In order to filter this light that way you have to be behind the lens generating the light obviously This is why no lens has Blades in front , its useless that way . Send a laser in to the lens , it wont come out , it will be scattered going everywhere and this proves you that even if you make a pin hole in front of the lens , nothing changes far as optics goes . Telescope Eyepieces also have this they have step down rings to improve optics and those are also put in optical center behind the first lens , you can put rings on it externally if you want it will change nothing . Now Astronomers are sometimes confused by this , because in Newtonian telescope design you can indeed block the light and change F ratio , you can put Blades in front of the lens so to say and it will work . But that is because Newtonian design , has 1 optical surface and its a mirror , and you can block light hitting the outer parts of that mirror by shading the Aperture , so it works , but not in a complex lens or any lens . What you are doing is Sacrificing Brightness for less Spikes , but you can never remove it all , even if you make a pin hole in front of the lens you will still have Diffraction Spikes because some light will still hit those blades because front element scatters light , bends it that is its job . So if it works for you by all means do it , but forget any optical Change , there is no change, its still F4 lens , still same sharpness , same focus , same depth of focus same resolution , just less Diffraction Spikes because of partially shaded blades , that is all .

[@NebulaPhotos]

I don't know why you think I'd lie about testing it. I'll work on a video to show you test results with images, showing the effects of using the internal Iris vs. step down rings. To be clear, I understand what you mean that due to the complex lens design it may not be accurate to say I am changing the focal ratio, but in terms of just the effect on the stars you are very wrong to think the only thing that happens is the photo gets darker. Using step down rings can clearly improve star shape and sharpness in the exact same way that stopping down with the iris does. I only test these lenses at night at infinity focus. I have no claim that step down rings will change depth of field as I have never tested that and you are probably right there. Of course, a telescope only focuses at infinity. Cheers, Nico

[@newforestobservatory9322]

The Askar only has a 50mm aperture, whereas the Canon has a 72mm aperture. Chromatic aberration on the Canon is easily dealt with in Photoshop - but of course it is better if it isn't there in the first place.

[@astrogerard2022]

Goodbye Canon lens. LOL

[@davedev5427]

Meh. You stated the obvious. Nothing new here. Frankly I’m not impressed with either lens due to the terrible distortion.

[@NebulaPhotos]

Do you have a better recommendation at 200mm f.l.?

[@newforestobservatory9322]

If you use the Canon 200mm at f#3.8 with a 56mm filter on the front the stars are good across the whole FOV of an APS-C size sensor. Any chromatic aberration is easily sorted in Photoshop.

[@gy9326]

First

[@Duphe]

why are you dressed like my religion teacher?