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[RCC] How can I improve my Planet images?

26 Jul, 2020 10:15
Hi all,

I'm starting with planet astrophotography and I'd like any feedback or suggestion to help me make progress.

These are two examples of my results until now:

- Jupiter and Europa transit:
- Saturn in opposition:

I feel there is a lot of space for improvement, but I don't know exactly where to put the focus first: acquisition, processing, equipment?

For instance, my equipment is a Skywatcher Mak 180/2700 with HEQ5 and ZWO ASI 120MC-S camera. Visually I see neat and clear images of Jupiter or Saturn, however, through camera (using the ASIStudio ASICap software) I don't get focused AVI videos. Also when I try to focus there are a lot of vibrations, I suppose that is normal and it could be reduced with another kind of focuser, maybe a motorized one (any suggestion will be very welcomed).

Regarding my process flow what I'm trying is the following:
1. Open video (between 30-60 seconds) in Autostakkert 3, analyze it, select between 30-45 % of best frames, select "Place AP grid" and stack the frames.
2. Open the previous resulting image in Registax 6 and apply the following changes:
    a. Play with wavelets in an artistic way following my personal tastes and denoising if I think the wavelet change introduced too much noise.
    b. Flip x axis (because I think the Maksutov mirrors horizontally).
    c.  Try to align RGB when I note there is too much misalignment (normally I note that in the Jupiter moons).
    d. Strech the histogram when I see a tail without light.

I feel the process is very basic and should be improved, but I don't know if I should start improving the acquisition and after that focus in the processing flow.

Thank you!
27 Jul, 2020 09:22
Hola Rafael,

Actually, my experience with imaging planets is not worth mentioning but anyway:

1. Focusing
Poor seeing and low altitude makes it hard to focus, indeed. Please try and increase exposure and gain until you see the moons or a nearby star. Focus until the moons are smallest (this may help you save the expense for an additional focuser). Then adjust exposure and gain for the planet. For the ASI120MC-S a maximum gain of 40 was so far a good compromise for me in terms of noise.

2. Video
In order not to smear the image as a result of the planet's fast axial rotation, I take about 90-second videos selecting a small ROI, say 640 x 480 pixels or even less to obtain a high fps, hence as many frames as possible. Since most of the frames won't be good, I have Autostakkert stack about the best 10%. In most cases I get 400 to 500 (more or less) "good" frames. Please also try 1.5x Drizzle and set align points manually in Autostakkert.

3. Processing
Autostakkert can do the RGB alignment for you after stacking. Many rely on an ADC, such as ZWO's, to get all colors to a correct angle. I never used one though. Wavelet in Registax is a great choice. When the image looks good and not too sharp you can load it in Photoshop or GIMP for final touches using Level, Curves and Color Balance, if need be. A light Gaussian blur helps remove residual noise compromising a bit of sharpness.

The safest advice I have is to image only when the planet is near culmination while seeing is good, also considering the native focal length of your scope which does not allow for short exposures.

You may receive lots of (better) recommendations from other fellow AP'ers :-)

28 Jul, 2020 10:37
Thank you very much, Robert!

You have given me some advices I'm looking forward to try in my next sessions.

Regarding the processing flow, perhaps it is a crazy idea, but I was thinking about something will really help me a lot, and maybe other newbies like me, would be to compare my own results with what can be reached by people with more experience working from the same video source. I'm thinking in a kind of dedicated forum topic alike this Request Constructive Critique or a challenge of processing, where given an AVI all participants provide their processing results.

29 Jul, 2020 06:45
You are welcome Rafael, de nada!
This could end up in a truly good idea, some kind of "image pool", but since AVI and SER files can occupy a few gigabytes they should not burden Astrobin's server(s). However, a pool of a few unprocessed image stacks for anyone to download and "play" with is certainly feasible.
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