Planetary stacking problem - what's causing this?

[billyharris72]

Hi all:

Attached is an image of Jupiter I took last night, my first attempt at stacking a planetary image (I've done a few of the moon, which has generally worked out okay). The image is the best 50% of 2,175 images, recorded over 2 minutes on an Opticstar PX125C. The unsharpened image looks very blurry, but detail begins to emerge fairly quickly with sharpening (the sharpened version here was done in registax, but AutoStackert's own routine produces similar results). Unfortunately, the image is pretty much written off my the weird artefact going on in the centre. Does anyone know what causes this effect and how to avoid it?

Billy.

[mikeonnet]

Hi Billy. I would say it's down to the exposure setting / gain setting on your camera software. I use iCap (Celestron) software and found similar issues. I'm not sure about the software you use but I'm guessing you can manually adjust the exposure time. I would say your virtually bang on but try adjusting it to the next setting. I.E. If it's set to 1/20th of a second try 1/30th for example and look at the live view on screen. OK, it may go slightly darker but the whole planet should then be the same contrast. You can make adjustments to brightness / contrast etc. in post processing.

Funnily enough, I was imaging some Sun spots today (with a solar filter of course) and had the same thing, I just lowered the exposure setting to the next level because I got an overexposed section in the middle of the Sun. I maybe completely wrong but that's what I have found to be the cause.

 

[billyharris72]

Thanks Mike, I was wondering if there might be an exposure issue of some kind. I do seem to remember somewhere reading that for this sort of planetary imaging the video should be quite dim, so I'll try tweaking the gain. The other thing I was thinking might be worth trying was reducing the resolution (and possibly increasing the duration by 30 sec or so) to try to get more subs - that might help in terms of allowing the image to be stretched and sharpened more without introducing too many artefacts.

Billy.