Processing mars & pleiades data
Posted 04 March 2021 - 10:44 AM
I feel like I'm washing out the star colours in stretching (Mars isn't quite as orange as I'd expect. BUT the originals have a very orange hue to them due to light pollution. I'm thinking that might be the reason. ie. I'm taking out the colour of mars while leveling out the colours)?
And it appears as though stacking creates an overlapping planet Mars.. My imaging is far from perfect so the surrounding stars aren't perfectly round either, but the direction is completely different. As if the stars are elongated from the center of the image out, whereas the mars duplicate is at a 90° angle compared to that. It's as if there's 2 overlapping planets in the image. For now the only plausible cause I can think of is the apparent motion of mars compared to the background stars.. But I was out shooting for maybe 2 hours, is that enough for mars to have moved so much?
Anyways here's the original stacked image:
And what I got out of it.
As you can see the light pollution wreaked havoc in the images.. I'm thinking they are a bit overexposed for processing, bu that's what I got to work with. yesterday was a no go weather-wise, and tonight and tomorrow won't be either..I'm not completely dissapointed though, there is some faint nebulosity visible around the seven sisters!
- MJB likes this
Posted 04 March 2021 - 11:20 AM
Yeah, you probably see Mars moving. When I shot Venus with M45, I had to throw out half of my images due to an elongation of Venus when stacking. I had to find a happy median which was about 20 minutes total integration, and there was still some elongation but not enough to notice with the glare of Venus.
Edit: Going to try my hand at Mars and M45 on Saturday night if the weather forecast holds. Have a 200mm lens coming for the D5300 tomorrow. Fingers crossed for clear skies.
Edited by Hypoxic, 04 March 2021 - 11:32 AM.
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Posted 04 March 2021 - 11:42 AM
Here's a quick processing of your raw stack... I probably stretched it more than the data supports, but I'm personally not bothered by seeing a bit of noise. You have a lot of good stuff going on in this data!
This was processed in Astro Pixel Processor, Starnet++, and GIMP.
Light pollution removal
Star color calibration
Save as 16-bit TIFF both a highly stretched for the background and a low stretch for the stars and planet.
Starnet++ on the background to remove stars
Open the starless background
Open the starry low-stretch version as layer.
Place the low-stretch layer on top, set blending mode to "lighten only"
Clone stamp the dust mote in the top right corner out of existence.
Make new layer of background, place on top, gaussian blur of 2.5 pixels, set blending mode to "lighten only." This helps smooth some of the background noise.
Hide star layer, make new layer from visible.
Curves tool on the new layer to darken the background, repeat until finished.
Show star layer, boost saturation of stars.
I did have to crop out some lighter colored rings around the outside of the image... are you calibrating with flats?
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Posted 04 March 2021 - 11:44 AM
Yeah, nice result - you did indeed get some nebulosity. I got a few 60 second exposures with an Olympus OM-D M4/3 camera with a 75mm lens (the only thing I had that would get both Mars and M45 in the field). I got 3 60-second shots but haven't tried stacking. Light pollution was pretty heavy for me too in the middle of the city, but I was glad for some clear sky in any case. Here's a single frame:
Posted 04 March 2021 - 12:44 PM
Both Mars and the stars in the Pleiades are so bright, it takes some care not to blow them out. My solution (in the city with light pollution) was 10-second exposures at ISO 200. Here is a 10-second, unprocessed (apart from cropping and resizing) exposure but at ISO 800 that has indeed saturated Mars and the cores of the seven sisters. (Chromatic aberration is very evident.) SMC Pentax-M 200mm f/4 lens at f/5.4 on a Pentax K-3II. This is from March 2. I only got 15 minutes worth before clouds rolled in, so no chance of capturing any nebulosity in the “full” stack.
Edited by Alen K, 04 March 2021 - 12:46 PM.
Posted 04 March 2021 - 01:46 PM
Mars doesn't move fast but it does move. I ended up using only 40 minutes out of nearly 3 hours of data. Beyond that, Mars became a thick line with round ends, rather than a circle, even though the surrounding stars were well aligned. It might work to process it like you would a comet.
Posted 04 March 2021 - 02:31 PM
And I only realized Mars moving about it's own orbit around the sun would make it move against the starry background. I never gave that any consideration as I was shooting, and to be fair I didn't think it would be such an issue.
Posted 04 March 2021 - 03:15 PM