120MM f4.3 Scope that Saved me $2600+

There is a big secret in the astrophotography world. That is, with a mono camera because you are photographing only one wavelength of light at a time, chromatic aberrations do not matter. What this does is greatly simplifies the design of the scope and it also allows you to save a lot of cash. This has not been taken about much so I am putting it out there now. Maybe some of you who have wanted to jump into the wonderful world of mono cameras and narrowband imaging can now justify the cost of such an endeavor. Oh and the bigger you go with an achromat. The more you save. I can see myself trying to buy a 150mm achromat next. Also with he speed of this scope there is really no scope out there that I could upgrade to. Save for finding scopes with maybe different focal lengths for different sizes of objects.

[@AntonioPena1]

Thanks for taking the time to break the cost and the logic used, make sense for people like me starting to think on saving some pesos on this expensive hobby. Thanks.

[@keithfischer8493]

What an awesome premise and value case. Thanks!!

[@TheNarrowbandChannel]

Thanks Keith!

[@jiffijoff9780]

Very helpful advice there, thanks for sharing. BTW, love the hat 😊😇👍

[@TheNarrowbandChannel]

Thanks so much!

[@GarnettLeary]

Very good logic here. I totally agree especially with robotic focusing. If a person can afford it perhaps an apo doublet is the middle road to this thinking. You can drop the SHO and get reasonable OSC broadband. Very good video and a subject definitely needing to be dispelled.

[@TheNarrowbandChannel]

Absolutely!

[@TheStevecas9860]

Very interesting thank you for that information!

[@CosmicSandcastles]

very informative, Thank you!!!

[@TheNarrowbandChannel]

Glad you enjoyed it!

[@massimofrattini5473]

GREAT...thank you!

[@enbi1352]

Grazie mille, I have an achro that I was about to sell and after this video I will try your suggestion. Ciao

[@ProcessedDigitally]

Good Shots

[@enidrajm]

New sub here. Thanks for this video and I appreciate the viewpoint on astrophotography you share through your channel. In another video, you mentioned the controversy surrounding the telescope formerly known as the Radian Raptor. I was a newbie when it came out and fell prey to the marketing. I'm still smarting about it, but I'm dealing with it by cultivating better technical know-how in my gear selection as I progress in this art. Recently, I concluded something similar to what you talk about in your video. In my case, I'm working with the SVBONY SV503 80ED with a 0.8x reducer/flattener. Though it's an achromatic telescope, I'm finding the results quite nice relative to the cost and focal length. I'll start integrating some of the pimping you've recommended.

[@TheNarrowbandChannel]

Awesome Miguel. Fee free to send me some links to some images. I have been curious about how that exact combo could work.

[@michaelklemm-abraham7298]

Dear Miguel. SV503 seems to be a great scope. If you use a mono camera even with RGB filters you probably won't see any bloated stars or chromatic aberation if you refocus on each filter (which will be necessary anyway). Though I have to say those are not typical achromatic telescopes (I think they are downplayed a bit) since they use ED glass. In earlier days people used to speak about semi-apo. This has been completely lost nowerdays. Many ED telescopes today rather should be put in this semi-apo designation no matter if they call them achromatic or apochromatic (simply because things are not just black and white). Anyway. have fun with your scope.

[@Luftbubblan]

Looks great. Been thinking about that my self but havnt dared to try. I will def pickup a cheap scope to try now :D Do you think it matters how "narrow" the filters are? My current setup have 6.5nm.

[@TheNarrowbandChannel]

I was using a f6 achro with a 0.85x filed flatter reducer to get me to f5.1 and with 7 and 8.5nm filters it worked great. So I think your 6.5nm will work just fine. Faster the achro is the narrow your filters should be. Course the lower cost of the scope means you can now afford those narrower filters.

[@ballage2023]

at first I thought, wow this russian guy has flawless english, no accent at all...then I realized you are from the USA :D Great content! keep it up!

[@TheNarrowbandChannel]

Haha its a Chinese hat ;)

[@Robin-Visser]

This channel deserves so much better. More subscriptions. Post your links on cloudy nights and SGL

[@TheNarrowbandChannel]

I am on Cloudy Nights. Actually did post it there. Got a lot of likes in two minutes then someone deleted it. Not sure why. What is SGL?

[@Robin-Visser]

@@TheNarrowbandChannel stargazerslounge. My previous message was deleted

[@jeancharbonneau2206]

Genius, I put my AR152 back to work. Thanks

[@skipfranzese5667]

Great video and solid point! I shoot narrowband and I have rgb filters. If I were to go this route for a longer focal length for say galaxies and will be shooting rgb with my asi294mm camera will the concept be the same, will it work? Thanks in advance, Skip

[@TheNarrowbandChannel]

Chromatic adorations are always lower with longer f ratios. So I think it should work for you provided you're working at at least f7 or slower. Don't forget a field flatter. I had decent success at f5.1 I think the results would be a lot better at f7 or slower though.

[@skipfranzese5667]

@@TheNarrowbandChannel thank you

[@jean-clauderoussil6830]

I love your hat!!!

[@TheNarrowbandChannel]

Tank you!

[@natem7440]

I have a short tube 80 with upgraded 2 inch focuser. I only have a DSLR right now - but would be really curious to try this with the ST80. If i got a ASI533 or ASI1600 i guess i should be ok with 1.25" filters?

[@TheNarrowbandChannel]

With the 533 those filters will work. The 1600 though the scope may be to fast for them.

[@dougcooper4917]

Great Video. Very Technical For A Beginner. Not Understanding Your Information. Thank You.

[@BlueTrane2028]

If you're new to telescopes and astronomy in general, I think it's best to just observe the night sky visually. I've yet to break into "real" astrophotography, only a cell phone pic here and there through an eyepiece. I've been an avid observer for about the last 5 years, and only now am I really starting to hear the siren's call to take photos.

[@dougcooper4917]

@@BlueTrane2028 Thank you for your advice.

[@WhittleAstro]

Great idea, how are you finding it after all this time? Tempted to try also. I run a 1600MM Pro and run narrowband. Also added a green and blue filter to go for almost RGB with Ha as red. With limited clear sky here in the north of the UK tempted to give you method a shot and change from a SW 72ED to a 102 achro for 40% more light.

[@TheNarrowbandChannel]

I am quite happy with it still. It is faster and lets me collect data in shorter periods. Sometimes i can get two filters done each night. I have tried a slower f5.2 with filters amd results were ok. If it had been a slower f6 would look better for broadband stuff.

[@TheNarrowbandChannel]

You will just need to find a matching focal reducer/flatener.

[@WhittleAstro]

Thanks for taking the time to reply, much appreciated! Strange how not many others seem to do this… guess once you have already spent a lot on glass you don’t want to be told there are other ways :-)

[@WhittleAstro]

Finnaly the weather cleared up over here in the UK and I got together a Skywatcher 102 achro and 0.8 reducer. Took a night to get some spacing sorted but…. The one basic Ha image I have so far isn’t to bad :-) I can clearly tell the light gathering difference between the 72ED with flattner (not reducer) and the 102 with the .8 reducer. Just over a stop extra light.

[@rickmoore4776]

zwo 120 camera used $75.00 ... 120 celestron scope used $100.00..filter $20.00.. Celestron AVX mount used $600.00.. so I spent around $700.00 for my setup. compared to almost $6.000...

[@michaelklemm-abraham7298]

I use an doublet ED Scope (Skywatcher 80ED) for deep sky but with flattener(reducer I am still at slow 510 mm of focal length. I often thought about just using an fast achromat with reducer/flattener and my trusty ASI1600MM it never happened. Big problem is not the achromat (the SV48P with 90 mm lens and 500 mm focal length seems to be a great scope) but finding a matching flattener/reducer. For ED scopes and Apos they are available but I is harder to find one for an achromat. I am curious to be honest how you found one for yours.

[@TheNarrowbandChannel]

I already had a reducer for a scope and when I purchased this scope I just gave it a try. It was a gamble to buy. There are generic focal reducers and flatters that are designed for a FL and aperture range. They usually have a little less quality though. The Focal Reducer I paired with mine was an exact match in FL just the Aperture was a little different.

[@michaelklemm-abraham7298]

@@TheNarrowbandChannel With some "universal" flatteners I've just read that field curvature is mainly dependent on focal length and you can adjust it for different focal length by adjusting working distance of the flattener (shorter focal length, longer working distance). So even if your result isn't quite perfect you may be able to get decent results by adjusting the sensor/flattener distance. teleskop-austria.at/bild/LFF-universal-1.jpg for example is a universal flattener that shows correct working distance to focal length on its barrel. So I have to say thank you for the information. I might never have found this good piece of information without you.

[@DeMorcan]

May I ask a question and it probably only applies to me. I have an Off Axis 130 in a carbon fiber 8" tube so there is no cool down time I used to shot beside a friend who had an AP-130 years ago. I also had an MN5" f6 for wide angles. I did not have them remirrored because after my cancer and chemo damage I cannot handle of the tripod and counter weights. Is there a lightweight solution I could use? I would like to sell these to get something lighter, but no of no one who is even interested in astrophotography. I have done the Messiers and the had a start on the Herschel 400. But now I just want to photograph anything again.

[@TheNarrowbandChannel]

You could easily sell it on cloudynights.com

[@DeMorcan]

I forgot them. Last time I went there my articles were in the archives. Thank you.

[@DSOImager]

Just last night I was looking at some of my early pictures taken with a stock dslr and my first telescope, the Orion st80 and thinking.. this really wasn't so bad, lol... Doing something like this might be a fun experiment. The focuser is garbage though.. probably similar to the one that's on your 120.

[@TheNarrowbandChannel]

I bet it is the same focuser.

[@BlueTrane2028]

@@TheNarrowbandChannel the ST80s focuser is 1.25" only but the same in design. GSO does make a 2" for it, but they're super hard to find right now. I have an ST80 setup with it. I have not yet jumped into astrophotography, but your narrow band mono idea to cut local light pollution sounds like a wonderful thing to try, and between my 80, 102 and 120mm achros, all with nice dual speed 2" focusers, seems like I have ready made options for different sizes of objects... Just need the filters and the camera. I already have a suitable mount (Sirius EQG).

[@TheNarrowbandChannel]

@@BlueTrane2028 Just start with one filter. The Ha filter. Get good at taking photos with that. They are BW but will blow you mind with details. Then later on get an Oiii to do two color imaging. Then lastly do Sii for the full three channels of color. By then you will be proficient enough to tackle the challenge of all three filters.

[@k-d-n]

But what I don't understand, is why is it necessary to use both a mono camera AND a narrowband filter? Wouldn't you overcome the shortcomings of an achromat, just by shooting in mono with an RGB filter? Thank you for the video btw. I just bought the SVBONY 102mm F/7 ED Doublet Refractor, and are planning to use it with my ZWO 1600 GT.

[@TheNarrowbandChannel]

You could do RGB. My own scope though is pretty fast so had to stick with narrowband which is really not a handicap in the city. Faster scopes have more chromatic adorations than slower ones do.

[@michaelklemm-abraham7298]

A classical Fraunhofer achromat like described in the video (made of crown and flint glass) can have very strong chromatic aberation (depending on the focal ratio). With an f/10 achromat it probably won't be an issue to shoot RGB with a mono camera. f/8 is rare for achromatic telescopes but it might work but for a fast f/5 telescope the bandwith of the RGB filters will be too big. Those telescopes are designed to focus not the colors (red light for example can be multiple wavelengths) but specific wavelengths in one spot. All other will deviate a bit. With a achromat deviation can be quite big, for an apochromat deviation is negligible. So your possibilities are always limited to those deviation (determined by focal ratio and glass types). I hope this answers your question in a little more detail.

[@cliveroberts415]

That is good to know but you could always buy a newt, no CA

[@TheNarrowbandChannel]

I do have a newt as well. I use it for galaxy season. Will be switching over to it soon. A lot of people do not like newts became of collimating. However I think coloration is easy with some practice.

[@qx3V45p]

What focal reducer did you use with your 127 Acro? Stars good to the edge of a 4/3 sensor or no? I hear that OTA is quite flat without a FF. Please share with fellow NB achro imager :)

[@TheNarrowbandChannel]

Its the Skywatcher 0.85 focal reducer for their 80ED. Also the Orion one for their clone the 80D works fine too. I have both they are exactly the same.

[@TheNarrowbandChannel]

Also awesome to meet another Achro Narrowband imager. More people need to know that you can do this.

[@qx3V45p]

@@TheNarrowbandChannel Thanks for the response my friend as there's not much info on these acros, especially OTA and FF/FR combo's that work well. ATM I'm testing a 152mm/f5.9 @ .8x reduction (3nm SHO) and works quite well. OTA Just needs a good collimation which I'll perform when the moon comes around! Too much fun gobbling up data while it's dark!

[@TheNarrowbandChannel]

@@qx3V45p I hear ya. And what tools do you use to climate and ache?

[@qx3V45p]

@@TheNarrowbandChannel Did you mean what do I use 'to collimation an Achro'? :) If so, A laser and a Cheshire eyepiece is what I use.

[@mikem9246]

A guy holding a telescope while it is snowing is the most Pennsylvania astronomy thing that I can imagine. :)

[@TheNarrowbandChannel]

Ya seams like we get more cold weather and snow then I remember in the old days. The lens I was using renders the snow very well though. I was surprised by that.

[@BlueTrane2028]

@@TheNarrowbandChannel I'm smack up against Philadelphia. Figure it's worth trying a setup like this under Bortle 8/9?

[@TheNarrowbandChannel]

@@BlueTrane2028 Absolutely. The latest set of filters that I just got are 3.5nm and they block light solution by a factor of 150x. I know plenty of photographers doing it in the city.

[@sneakerset]

Those I-Star achromats sell quick (used). Thanks !

[@TheNarrowbandChannel]

I had no idea that company existed. Thanks, I bet it would be fun to make a 8in achromatic. Would need a larger mount for sure though.

[@mikem9246]

Theres a couple of reviews on the new IStar 140mm f/6.5 on Cloudy Nights right now. Its a ton of telescope for the price.

[@TheNarrowbandChannel]

@@mikem9246 I have not read it yet but did see the article. But probably will later today. Thanks for sharing. One that is on my list to perhaps try next year is the 150mm Achromat which Celestron and Skywatcher sell. Its an f5 as well. I could use the same focuser on it too.

[@sjpp71]

@@TheNarrowbandChannelNice video, great idea, thanks for sharing. That gives me the perfect excuse to get the 120mm achro I've always wanted. As far as I know, the 150mm achro offered be celestron, skywatcher and others is f8, isn't it, not f5, so warning, is kind of a big bazooka! Clear skies, enjoy the winter!

[@donorastrophoto]

Or buy a Sky-watcher 130PDS, which, even with coma corrector costs about 500. Then you can shoot both narrowband and RGB. ;)

[@TheNarrowbandChannel]

Newtonians are really underrated. I use one too. Huge bang for buck.

[@screwyouyoutube5493]

I agree, between all of my scopes, RC, Newt and APO the Newtonian provides the sharpest and fastest best results with my 2600mm

[@thugg_nuggets]

What’s the scope 👀

[@TheNarrowbandChannel]

I will put a full breakdown of the parts I used in the description later today. This scope was the Orion ST 120.

[@T0ly113]

I don't think DSS can do any rescaling at all, so be aware

[@TheNarrowbandChannel]

DSS can. However it sucks. Try ASTAP. Free and way better.

[@astrophoto_andy3335]

Why did this never occur to me!!! I really love your channel and content!

[@TheNarrowbandChannel]

Thanks. I try to cover things that other channel miss. Does not get me tons of views but its still good stuff. :)

[@davidemancini7853]

Good idea but got to take flats 3 or 4 time

[@TheNarrowbandChannel]

This is another one of those things though that software has automated. Flats today are a single button push and then they are done even if I Have 8 filters. Plus I keep my gear clean so flats are something I do only every 3-5 months.

[@davidemancini7853]

@@TheNarrowbandChannel you have to do flat every time the focus change.

[@TheNarrowbandChannel]

@@davidemancini7853 Infinity is the same point each night. But every filter, par focal or not, will have a different point of focus. You should not be taking flats every night. There are much better ways to use your time :)

[@testboga5991]

And now take the next step: use a reflector, forget about chromatic abberations completely.

[@TheNarrowbandChannel]

Actually going to put this scope back together soon. You will see some content about it soon too.

[@MrTyroneweaver]

Coming home from the golf course the other day I shot a magpie with an FX Maverick compact and recorded it on a Go Pro side shot Air rifles are a lot like astronomy gear. The advances in the last couple of years is amazing.