14 replies to this topic

[sjanarth]

I have the following setup for my planetary imaging:

• Celestron Edge HD 11 on Skywatcher EQ6R-pro
• Televue 2.5X Powermate

This combination gives me a focal length of 7000mm at f/25.

• ASI 585MC (primarily for its larger sensor size)

This gives me a resolution of 0.09 "/px with no binning and 0.34 "/px with 4x4 binning.

 

I mostly do all my imaging from our backyard (Bortle 6-7 skies) with Good/OK seeing. 

 

Problem: My images end up being soft (example).

What I've tried so far:

• Dialing in the collimation and focus (get much better visually)
• My workflow is pretty standard - pipp, autostakkert, registax (or pixinsight)

 

Questions:

1. Am I better off not using the powermate (or a 2X instead of the 2.5X)?
2. Should I consider a different camera with a larger pixel size (585 has 2.9micron pixels)?
3. Should I always consider binning 4x4?

Would greatly appreciate any insights as I've run out of ideas trying to get sharper images.

Edited by sjanarth, 06 October 2024 - 10:05 PM.

[Tulloch]

Hi there, you are imaging at too high a focal ratio, you should be aiming for a focal ratio of 5x the pixel size of your camera (in your case, f/15) with no binning. 

 

This (and lots more) information about Planetary AP is in the FAQ at the top of the forum, or linked to below.

https://www.cloudyni...september-2024/

 

Hope this helps,

 

Andrew

[sjanarth]

Thanks, Andrew.

 

I had consulted the FAQ earlier and at f/15 (or even f/10), I still oversample.

 

206.265 * 2.9 / (2800 * 2.5) = 0.09 "/px

206.265 * 2.9 / (2800 * 1.5)  = 0.14 "/px

206.265 * 2.9 / 2800 = 0.21 "/px

 

Ideal pixel scale with OK seeing = 0.67 to 2 "/px

Ideal pixel scale with Good seeing = 0.33 to 1 "/px

 

So, it almost seemed like for this telescope + camera combination, in OK-Good conditions, I must bin?

[Winteria]

Thanks, Andrew.

 

I had consulted the FAQ earlier and at f/15 (or even f/10), I still oversample.

 

206.265 * 2.9 / (2800 * 2.5) = 0.09 "/px

206.265 * 2.9 / (2800 * 1.5)  = 0.14 "/px

206.265 * 2.9 / 2800 = 0.21 "/px

 

Ideal pixel scale with OK seeing = 0.67 to 2 "/px

Ideal pixel scale with Good seeing = 0.33 to 1 "/px

 

So, it almost seemed like for this telescope + camera combination, in OK-Good conditions, I must bin?

That astronomy.tools calculator is only meant for Deep-sky imaging. What Andrew said above is much better advice.

Edited by Winteria, 06 October 2024 - 11:12 PM.

[kennhk]

I have used your similar setup and focal ratio (7000mm F/25 585mc), and it definitely works. Make sure you dial in your collimation perfectly on a star at either a extremely high mag of eyepiece or full imaging train, and try to focus in and out as many times as you can. If the image is still soft, then it would be because of lower altitude (below 1000m) wind or local seeing. High altitude jetstream has a wavy quality to it but is still sharp. 

Did you use a adc or a good barlow, it seems the fringing is the main issue here. Also Imo I find the F/15 focal ratio is way too low and limits detail and depth massively 

Edited by kennhk, 06 October 2024 - 11:18 PM.

[sjanarth]

Got it, then I'll drop the powermate from my imaging train and use the C11 at its native 2800mm @f/10. Thank you.

 

Another related question: I also happen to have an ASI294mc pro which I use for deep sky (sometimes lunar) projects. This one has larger pixels (4.63 microns). I'm wondering if I'd be better off giving up on the 585 and using the 294 with the 2.5X powermate? 

 

C11 + 2.5X powermate + Flip Mirror + ADC + 294mc

C11 + Flip Mirror + ADC + 585mc

 

I'm looking for ways to get shaper images with more details than this recent sample of mine. 

[sjanarth]

I have used your similar setup and focal ratio (7000mm F/25 585mc), and it definitely works. Make sure you dial in your collimation perfectly on a star at either a extremely high mag of eyepiece or full imaging train, and try to focus in and out as many times as you can. If the image is still soft, then it would be because of lower altitude (below 1000m) wind or local seeing. High altitude jetstream has a wavy quality to it but is still sharp. 

Did you use a adc or a good barlow, it seems the fringing is the main issue here. Also Imo I find the F/15 focal ratio is way too low and limits detail and depth massively 

2022-08-13-1952_1-KL-L-Jup_lapl5_ap158_result.jpg

Thats an awesome image, Ken !!!

 

On the ADC, yes, I do use a ZWO ADC (see my full imaging train in my previous post above).

I can't say I'm an expert with ADCs but I do try to get the colors aligned with Fire Capture's ADC tuning tool.

Also, I try to shoot when the objects are at least 30 degrees above the horizon (typically 45-90 degrees).

[Tulloch]

There is a mathematical "proof" of why the "5x rule" works, it's in Sec 6.1 of the FAQ. Anything above this value in anything but excellent seeing is generally considered to be "empty magnification", ie the image is larger but the resolution is the same. Imaging at a focal ratio higher than optimum requires the use of longer exposures (which reduces the number of frames you can capture so the S/N ratio is lower) or requires higher gains (which increases noise so S/N ratio is lower). And you don't get any resolution advantage either.

[yock1960]

I use a similar setup, except that my camera has 3.75 micron pixels and yes, it's more than is recommended. It's a demanding setup, but it works for me. With your smaller pixels...hmmm...and if you're not satisfied, perhaps a change is best.

Steve

[RedLionNJ]

You could always greatly simplify your setup and pick up cam with 2.0 micron pixels - no barlow necessary then.  The asi678mc and its larger siblings are all great choices these days.

 

With typical seeing, you'd be fine with an f-ratio of 3-5x pixel size.  Even then, the 5x would be pushing it, only worthwhile on better than average occasions.

 

One factor I did not see mentioned - about how many frames are you stacking?  Several thousand is recommended in order to overcome noise and allow aggressive sharpening (Registax or WaveSharp).  Too subtle an attempt at sharpening is going to leave soft-looking images.

[sjanarth]

I chose the 585 for its large sensor size making it easier to locate objects. Will pickup a 678 and see how that does.

 

On the stack size, I typically get about 50 fps and shoot for a max of 2mins = 6000 frames and stack about 10-20% = 600 to 1200 frames.

[John Boudreau]

As someone who used a C11 for planetary imaging for about 10 years, I can say that about f/15 sampling would be essentially perfect for a 2.9 micron pixel. With the different cams I used through the years, My C11's sampling was largely in the 14 to 15 arcsecond/pixel range and that worked well.

[nicole2021]

I was using the same setup like yours last year. It is okay when the seeing is good.

 

This year I am using 678mc with ADC and no Barlow, and I did drizzle 1.5x.

And I found the result seems better than 585mc with TV 2.5x.

You don’t need a large sensor for planetary, but one that can give you higher frame rate.

More frames mean more data, but of course it highly depends on the environmental condition.

 

The attached Saturn was taken 2 days ago, 90sec x 11 (40% best frames), captured using FireCapture, and processing using RegiStax 6, WinJUPOS and PS.

Attached Thumbnails

• 

[sjanarth]

OK, now I'm confused about which camera should I choose next.

 

Current: 585mc with 2.9 micron pixels and 11.2mm x 6.3mm, no barlow

Candidate-1: 678mc with 2 micron pixels and 7.68mmx4.32mm, no barlow

Candidate-2: 482mc with 5.8 micron pixels and 11.13mm x 6.26mm, 2.5X Televue and bin 2x2

 

I've had a 462mc before (2.9 micron pixels, 5.6mmx3.2mm) and hated that for its small chip size (makes finding objects harder). 

 

So, I'm not sure if I'm better off getting a 678mc (no barlow, no binning) or the 482mc (2.5X barlow, 2x2 binning) -- looking for suggestions.

[Tulloch]

If you currently have a 585MC, then you don't need another camera, it's an ideal camera for the planets. It's just that 2.5x PM is too much for your system, ideally it should used at f/15.

 

As per Sec 6.1 of the FAQ, simply unscrew the barlow element off a standard 2x barlow and screw it into the camera nosepiece to give you around 1.5x magnification.

 

Andrew

Edited by Tulloch, 08 October 2024 - 10:34 PM.