Planetary Imaging - Which Barlow?

Find out how to choose a near optimal focal ratio for planetary imaging.
Link to my website on planetary imaging:
planetaryimagingtutorials.com/
Link to the planetary imaging playlist:
kzbin.info/aero/PLdvoDms8MWF7UNvrv-4Bkw3-eibwbLUWh
You can learn more by visiting the Cloudy Nights astronomy forums. Most of what I know I learned there.
cloudynights.com/
They have a forum just for planetary imaging called
Solar System Imaging & Processing
www.cloudynights.com/forum/77-solar-system-imaging-processing/
This post shows the rule of thumb
www.cloudynights.com/topic/413414-planetary-imaging-rule-of-thumb-which-barlow/

[@spacetimewithrobert4438]

This is explanation at it's best!!! You speak crystal clear and SO CALM while breaking down a complicated instrument into its most basic elements. 7/5 video. I just hope no ants were harmed off-screen! Thank you so much, clear skies!

[@vincepalaa]

Really enjoy your videos. The "burning ants" analogy definitely helped a novice like myself. Thanks!

[@vladimirlenin4080]

@Allen Brecken Bruh, you made a second account to reply to your comment. Kinda cringe if I may say so

[@jimshowtovideos]

thanks for taking the time to make these videos, learning a lot.

[@PlanetObservatory]

your videos are among the most helpful on the net. Thanks for making them

[@yveskc1]

Easy to understand and fun to watch. Thank you!

[@LiveSteamMad]

Absolutely excellent tutorial. Clear, and just at the right pace to take it all in, I enjoyed it.

[@gmalekhine1395]

So true!

[@MrGeoffHilton]

Great video, enjoyed and subscribed, most channels assume that you know basic things, glad you explain basics, thanks.

[@bobuk5722]

Ok folks, I've highlighted the Sun danger below but the rest of this series is REALLY useful for beginners. It gives the basics for selecting kit that will make the hobby so much more interesting. Some things are a bit out of date now - references to Web cams for example, but that does not alter the fundamentals that lie behind making the choices. BobUK.

[@cdub1955]

Hello wwgeb, these are great videos...thanks for sharing your knowledge. I am working on imaging with a ZWO ASI 120MC.

[@TheOmanJam]

Great video. Nice explanations.

[@HeyApos]

I am very impressed and thankful getting so much useful information in such a short video. You have quiet impressive teaching skills ,-) And I am very glad, that your series shows up, that understanding how things work outweights heavy and expensive equipment.

[@wellsleland4933]

I guess Im asking randomly but does anyone know a method to log back into an Instagram account?? I somehow forgot the password. I appreciate any assistance you can give me!

[@franklindrake3225]

@Wells Leland instablaster :)

[@wellsleland4933]

@Franklin Drake Thanks for your reply. I found the site through google and I'm in the hacking process atm. I see it takes quite some time so I will get back to you later with my results.

[@wellsleland4933]

@Franklin Drake It worked and I finally got access to my account again. Im so happy! Thank you so much you saved my ass!

[@franklindrake3225]

@Wells Leland Glad I could help xD

[@ChillPlayer]

Very well explained, thank you!

[@MikeK7115]

Really enjoy your videos. I had seen many comments and recommendations from other channels to view yours and I have not been disappointed. I have an older C8 Ultima OTA that I am upgrading to a CGEM mount for the winter viewing season. I also just purchased a Neximage Burst color camera with 3.75 micron pixels, hoping to capture some good images of the planets over the winter. From your recommendation, it looks like a 2x barlow will be appropriate for what I hope to accomplish? Is this right? Anything else that I need to be aware of? Thank you again and keep up the great work.

[@wwgeb]

Your C8 is f/10 so with a 2x Barlow you're at f/20. Using 5 to 7 in the optimal focal ratio formula means you want f/19 to f/26 for your 3.75 micron pixels so you're in range. My 2x Barlow gives me around 2.4x with my C8 and this is also in range. Check out the Solar System Imaging & Processing forum on Cloudy Nights www.cloudynights.com/forum/77-solar-system-imaging-processing/ and my website planetaryimagingtutorials.com/ It will be a few months before Jupiter starts to show up in the morning. Saturn can still be found shortly after sunset for a little while longer. We have to wait about 2 years for another Mars opportunity. If the Burst uses iCap then watch my Using iCap video. Have fun!

[@gmalekhine1395]

Excellent explanation! I own a Cel Edge HD, just bought on Monday! It is amazing!

[@samsen201]

@ 3:22 happened here! I did see smoke out of my celestron 127, when used solar filter at subjective side, and telescope was parked after letting sun to move out of field... Yes it hurts.

[@grkuntzmd]

Very nice explanation. Thanks.

[@GaryMcKinnonUFO]

Thanks for going into helpful detail.

[@ishanr8697]

Thanks, I used your formula to determine that my 6 micron sensor (Sony A7iii that I already own for photography) needs roughly a f-ratio of f/30. My telescope is f/5, so I splashed out on a Televue 5x Barlow which will bring me to f/25. I think I have the equipment to get good images. May need to wait a few months for optimal seeing conditions...

[@Steve_The_Ignorant_Astronomer]

I enjoy your videos a lot but watching what barlow had my head spinning a little. I have the asi294 pro mc camera and I am using a 10in. scope at 6.3. I use a 2x barlow to take images of Jupiter and Saturn but I just cant seem to get it sharp. Should I use a 3 or 4x barlow ? Would that help? If I am figuring right a 3x barlow would get me to a f18.9... What do you think ? Steve

[@wwgeb]

Yes a 3x Barlow would get you to f/18.9 but you want more. The ASI294 has 4.63 micron pixels. 5 to 7 times 4.63 gives f/23 to f/32. To get 23 you need 23/6.3 = 3.5x and to get 32 you need 32/6.3 = 5x. So ideally you would use a 3.5x to 5x Barlow. A 4x Barlow would be much better than a 2x Barlow. When you up it from 2x towards 5x the image will be less sharp on your capture screen but you will get better images after you stack/process them. While capturing it appears that you are getting junk (and you are when seeing is bad) but then surprise happens when you sharpen it. In case you haven't found my website here it is. planetaryimagingtutorials.com/

[@hectoreyesc]

Nice explanation !!!

[@MrCacciad]

hello , many thanks for your videos . they are really great ! I m starting with astrophotography..can you help me to check if I m doing something wrong.. the question I have is related to the barlow selection and binning mode. I m not sure if I m doing the right set up here s my equipment : Telescope : Celestron Nextstar 8 SE de F/10 longueur focale 2032 mm et diamètre 203 mm camera ZWO ASI290MC , caractéristiques Sensor: 1/2.8″ CMOS IMX290/IMX291 Resolution: 2.1Mega Pixels 1936×1096 Pixel Size: 2.9µm using Firecapture ... what barlow should I choose ? according to your video I should use a 1.5x but only have a 3x and 2x. should I buy a 1.5x how should I use the Binning mode ? without any barlow at all ? May thanks for your help in advance.. daniel

[@wwgeb]

I would start without any Barlow. That makes it easier because the field of view is larger which makes it easier to find and center the planet, and the image is brighter which allows for lower gain and/or faster frame rates. After some practice then you can try the 2x Barlow. I don't really have a feel for how useful a 1.5x Barlow would be. After trying no Barlow and 2x Barlow you may have a better idea. I never use binning with FireCapture. I talk about using binning in my video on Using iCap but that is to temporarily increase the field of view for finding and centering the planet, not for capture. FireCapture has an easy way to toggle between max size (1936x1096) and some smaller ROI (640x480 for example) so there is no need for binning.

[@rumple440]

If I have an F/15 scope (ETX-125) and a Neximage 5, should I be good or should I try a focal reducer (since F/11 is optimal for that imager)?

[@wwgeb]

From looking at what people do on Cloudy Nights it seems that the 5 in the optimal focal ratio formula could actually be a 7. If you chip is 2.2 microns then 7*2.2 = 15 so f/15 will possibly be better than f/11. I would try it at f/15 to see how that works.

[@jenslankamp6433]

Very nice video and very helpful, but I do have a question. I have a 6" F5 Newtonian, and would like to use my Dmk21au04.as (640x480) for some mono basic planetary pictures. With a pixelsize of 5.6, that would mean that I need about F25/F30. But I am a little bit careful with using a 5x Barlow for example, because of the seeing. I only have money for 1 barlow, would you still recommend buying a 5x Barlow or go a little bit easy and buy a 3x for example?

[@WarmWeatherGuy]

I would go with the 5x Barlow if your mount has motorized tracking. 5x will give better results than 3x provided you can keep the image centered for 2 to 3 minutes. If you don't have motorized tracking then it will be hard to find and keep the planet in view and a lesser Barlow will give a larger field of view to help in that regard. --- wwgeb

[@jenslankamp6433]

@@WarmWeatherGuy yeah unfortunately I have to follow manually. It is an non motorized CG4 mount, so it would be a wise option to choose the 3x first and whenever I add on a motor I could pick a 5x for example?

[@WarmWeatherGuy]

@@jenslankamp6433 I made a video "Equipment Needed" and starting at 3:42 I talk about mounts. In the video I show where I used a non-motorized CG4 mount. Yeah, I would get the 3x Barlow. Here is the video: planetaryimagingtutorials.com/getting-started/

[@adventuresofanamateurastro804]

Are my calculations correct using my orion skyquest XT10 dobson 1200mm f/4.7 telescope and my ZWO asi224mc 3.74 pixel I should not use a Barlow @ full resolution, but if I use 640x480 res. I can use a 2x Barlow? Thank for time, Drew

[@WarmWeatherGuy]

That is the camera I use now. At 3.75 microns your focal ratio should be between f/19 and f/26. To get that you would need a 4x to 5.5x Barlow no matter which resolution you use. For tiny targets like planets you want to use the smallest resolution you can keep the image in. There is no reason to capture all the dark sky around the planet and you end up with smaller files. Use full resolution to find and center the planet and for the Moon and Sun. There are links in the video description that you may find useful. --- wwgeb

[@lipstick318]

I want to use a 10" Dobsonian Telescope and use a orion 5x 4-element barlow... What kind of image/video results should I get??? Show Me, Please...

[@WarmWeatherGuy]

If you go to this web page planetaryimagingtutorials.com/getting-started/ and scroll down to the Equipment Needed section you will find links to pictures taken with 6" or smaller telescopes. The image size scales linearly with aperture size so your 10" scope will have images twice as large as those taken with a 5" scope. Jupiter will be about this big: www.astrobin.com/346840/B/?nc=user --wwgeb

[@josephmingione8994]

Great video.

[@percytate3292]

What focal length were you using when you recorded your amazing images of Jupiter

[@wwgeb]

Percy Tate I used the NexImage 5 for that picture. That camera has 2.2 micron pixels so the optimal focal ratio is f/11. I used my f/10 C11 without any Barlow so the focal length was 110 inches (2800mm). You can see the animation here: www.astrobin.com/77530/D/

[@percytate3292]

wwgeb OK thanks. Great image by the way. I have been experimenting and purchased an Orion StarShoot 5MP Solar System Colour Camera as this was readily available at my local telescope shop, and is also 2.2 micron. I have currently experimented with 1200, 1800, and 2400mm focal length and you can see how the resolution is improving (Jupiter). I am using a 150mm F8 refractor and a 2X barlow. My next step will be to use my 2.8 X barlow that will give me 3360mm to improve my image size but my results so far using 2400mm are very encouraging. I think I'm hooked.

[@wwgeb]

Percy Tate If your camera has 2.2 micron pixels then your optimal focal ratio if f/11. To get f/11 with an f/8 scope you would need a 1.4x Barlow. If you use a 2.8x Barlow your focal ratio is f/22 and your image will be twice as big and 4 times as dim compared to f/11. You will be getting only 1/4 as many frames for a given time period. It is worth a try but I think a 2.8x Barlow will give worse results. The best way to get a bigger picture is to get a bigger scope. The next best way is to use drizzle. With my 5 inch scope I use drizzle to get a bigger image which makes it easier to see what I'm doing when sharpening. Check out the Solar System Imaging & Processing forum on Cloudy Nights: www.cloudynights.com/forum/77-solar-system-imaging-processing/ They have long running post on imaging Jupiter with a 6" or smaller scope. It is amazing what you can do with a 6" scope. www.cloudynights.com/topic/398608-small-bore-challenge-jupiter-w-6-or-less/

[@percytate3292]

Ok, thanks. My problem is exactly what you said, my Jupiter image is too small at 2400mm to see properly in Registax. I'll follow your link. I have a collection of 6inch refractors as well as an 8 inch refractor.

[@acecastellano9455]

Wich Barlow is better in the Mak127 with asi120mcs Cam? 2,5 Barlow Tele vue or the 3× times Barlow?Greetings from Berlin Germany.

[@wwgeb]

I need to know the pixel size of your camera and the focal ratio of your Mak127. For example, if your pixel size is 3.75 microns then you want your focal ratio to be 5 to 7 times the pixel size so that would be f/19 to f/26. If your scope is f/12 then you would want a Barlow of 19/12 = 1.6x to 26/12 = 2.2x. With these numbers the 2.5x Barlow would be better than the 3x Barlow. A 2x Barlow would be even better. If you haven't found it yet here is my website: planetaryimagingtutorials.com/

[@acecastellano9455]

The Cam Pixel Size is 3,75 ive got the Maksutov 5inch teleskop i Think 3 Time Barlow is Two much, is it right?so i Chose the 2,5 Barlow is that Ok?

[@GaryMcKinnonUFO]

My Barlows have rubber eye pieces, how can i add my astrocam? I think i may need a barlow with no rubber plus a tube to slide the cam into but i'm not surte what thats called, or if it exists!

[@WarmWeatherGuy]

I use this one by Celestron: X-Cel LX 2x Barlow Lens - 1.25"

[@GaryMcKinnonUFO]

@@WarmWeatherGuy Thanks very much :)

[@WellingtonIronman]

I use spacers between my Barlow and camera to adjust from native 3x to 5x and anywhere in between. Its ugly but it works

[@ericmould9515]

Excellent!

[@menschin9854]

question: why would you want an airy disk bigger than one pixel since it makes the image blurrier? and the only reason why you can't burn ants is because the focal point is in your telescope. But as a basic rule: the more light you gather with a telescope (the bigger the diameter) the more photons it bundles at the focal point. and if your focal point is bigger than with the smaller telescope then you just arent in focus. With the best possible apo refractor or with a mirror (absolitely flawless), the focal point could theoretically be the diameter of one photon.

[@MaxArceus]

Since due to atmospheric distortions the 'location' of the detail on the pixelgrid moves around a bit, and you can you trace back some of it using the stacking of several images. You basically gain the extra resolution by sacrificing time. But the sun is not a point, it's a disk, so you'll aways end up with an image spread out over some area, no matter what your focal ratio is.

[@Astrofrank]

The bigger the diameter, the smaller the airy disc, due to diffraction.

[@juangoyenechetube]

What telescope is the one on this video?

[@WarmWeatherGuy]

It is the NexStar 5SE. It is $600 when on sale -- wwgeb www.amazon.com/Celestron-NexStar-5-SE-Telescope/dp/B000GUHOYE/

[@susantalahiry7502]

Awesome!

[@WordofBob]

Zwo asi462 shows 2.9 so *5 is 14.5. My 8" sct is F10. So I'd want a 2x Barlow ??

[@WarmWeatherGuy]

Anywhere between 5 and 7 works for the multiplier so between f/15 and f/20. If you can find a 1.5x Barlow that might be best. My 2x Barlow gives me 2.4x. The amount you get depends on where in the optical train you place it. Explore Scientific Focal Extenders work differently. If you get a 2x focal extender it will always give you 2x no matter what. -- wwgeb

[@ericgillin4319]

wouldn't the solution to all the pixel size this and that, be to use an eyepiece projection camera adapter. that would also fix the problem with high mp dslr cameras

[@WarmWeatherGuy]

I am not sure what you think eyepiece projection can do that a Barlow can't do. Spread the image over too many pixels and the exposure time can be measured in seconds rather than milliseconds and you end up with hundreds of times fewer frames to stack.

[@bluename4]

what would the effect be, if combining a Focal Reducer and a Barlow Lense together?

[@MrLostsync]

Thank you very much, excellent tutorial.

[@kayedsss]

🙏

[@rayr1444]

A barlow does not change the scopes focal length. It reduces the eyepiece focal length.

[@Astrofrank]

It *does* change the focal length of the telescope! That is very helpful, as you can use a version with a T-thread on top as tele converter for a camera which should be used with a telescope.

[@jons2447]

Thank you, "wwgeb"!

[@percytate3292]

Ah Ha, so that is why my Jupiter image is so small as I am running an F5 4" telescope with a 2X barlow. I will need to use my 2.8 X Barlow or a scope with a longer Focal Length

[@dennisgallagher1729]

I think your formula for the Airy disk is incorrect. Your formula is for the radius to the 1st dark rink. So 1.22 should be 2.44 for Airy disk diameter. Nice video though…

[@skye7690]

Televue Powermate

[@riaandewinnaar5040]

Sad about the ants though.

[@AMadScientist]

Aliens teaching their kids about this but saying, "if you want to burn more Earthlings, use the magnifying glass"

[@nettyvoyager6336]

definitely not Garry :P

[@andrewnicolas4839]

Omg - inches - seriously!

[@bobuk5722]

Never mind the telescope, looking at the Sun without certified solar filters can wreck your eyesight. Don't do it. BobUK.

[@Astrofrank]

The problem is also present with a telescope, as you have an eyepiece and the "optics" of your eye. Take a 102/1500 mm refractor, add a 25 mm eyepiece, point the telescope to the sun, focus the image of the sun on a white screen and then place a sheet of paper at the distance where the light beam is smallest. I did this in summer and the paper started burning immediately, without smoking before!

[@BritishBeachcomber]

Please don't burn ants...

[@menschin9854]

question: why would you want an airy disk bigger than one pixel since it makes the image blurrier? and the only reason why you can't burn ants is because the focal point is in your telescope. But as a basic rule: the more light you gather with a telescope (the bigger the diameter) the more photons it bundles at the focal point. and if your focal point is bigger than with the smaller telescope then you just arent in focus. With the best possible apo refractor or with a mirror (absolitely flawless), the focal point could theoretically be the diameter of one photon.