Europa Loc: West Hills, CA

This is a stack of 75, 180 Second exposures with flats and bias. I gave up on the clouds going away, so I went ahead and processed what I had.

M31

(Download)

JimH123 Loc: Morgan Hill, CA

Really good. Did you do something to reduce the core? I normally find that the core is so bright compared the rest of the galaxy.

Europa Loc: West Hills, CA

Thanks Jim, I was trying to keep the star color and keep them from getting too white and bloated. I think this helped keep the core down. I did take a bunch of 15 seconds, but never used them. I'll probably try this one again, as I didn't like how white the stars got.

What I did do for the core, was to take a less stretched layer and used a layer mask for the core.

Europa Loc: West Hills, CA

i do have a question about dotted lines I always get, in the attached there are 3 dotted lines, I assume from not pixels??? Shouldn't these get removed with the bias?

I get them even when I use both darks and bias. Possibly they don't get removed because my guiding isn't good enough ( creating the dotted line) and not getting picked up as sensor noise?

Lines

(Download)

SonnyE Loc: Communist California, USA

I've seen those before in my own meager attempts. I think they are stacking artifacts.

I get around them by doing long exposure one shot color.

Europa Loc: West Hills, CA

Since they are so small I just use the healing brush in PS to get rid of them, must are all red, green or blue.

SonnyE Loc: Communist California, USA

I don't see them in the main photograph.

But I've witnessed them in a stack. That's why I thought they are dribbles from the stacking process.
(And they are symmetrical.) I'm not good enough to remove them.

JimH123 Loc: Morgan Hill, CA

I see them, and they are all similarly curved the same way. What kind of mount were you using. And what focal length? Andromeda is quite large, and needs to be captured at low Power. Using an equatorial mount, I would not expect to see these unless polar alignment was way off. An ALT-AZ type mount could mean field rotation. I tend to think they are not stacking artifacts, but instead, they seem like hot pixels. I tried counting each dot, and I get 30 or so, but they are fuzzy enough that perhaps two dots are in each one? I was wondering if there was one dot for each image stacked? All 3 dotted lines seem to be the same size and same curvature. On any given single image, a stuck pixel is very sharp and defined. If you go back and closely look at just one, do you see a hot, stuck pixel that seems to be where the line is? And on another, does it show movement? If this is from field rotation, then possibly the fuzziness comes from the fact that it is so diluted down with the other images? What stacking SW did you use?

So thinking this through, a stuck pixel always is at the same spot on the sensor, no matter how many images you take. But if the scope is not exactly tracking properly, that stuck pixel will seem to move against the star background. The stacking process keys in on some stars it picks out, or in the case of Nebulosity, that you pick out. The stacking will lock the image so that it appears to not be moving, but that stuck pixel will now show it moving in relation to the now fixed image.

Europa Loc: West Hills, CA

I'm using an EQ mount at 620mm. I stack in Nebulosity4. Also, these images came over a 3 night period. Ill have to go back to the individual images to see if I can detect the possible hot pixel from image to image.

So what you are saying, is because of the tracking, the "marching" hot pixel will not be detected by Nebulosity as a hot pixel, and the bias will not remove it?

Thanks.

JimH123 Loc: Morgan Hill, CA

Yes, that sounds correct. And if you spot erase these pixels in the originals, then you won't see the dotted lines.

JimH123 Loc: Morgan Hill, CA

Here's an idea. Try contacting Craig Stark, the creator of Nebulosity and describe your problem.

http://www.stark-labs.com/help/contact/contact.php

Albuqshutterbug Loc: Albuquerque NM

Artifact or not, that is a really nice stack.
You really have to dig to see the flaws.
Nicely done.

bwana Loc: Bergen, Alberta, Canada

I'm not too sure what you use for alignment/stacking. If you're using ImagesPlus, you can use the Min/Max Exclusion Combine to eliminate/reduce hot pixels. PixInsight also has similar parameters for stacking in its ImageIntegration. Since I never shoot/use bias, dark and flat subs I have to use pre/postprocessing software in this capacity; it (normally) works very well but I still haven't found a way to eliminate thick cloud .

bwa

Europa Loc: West Hills, CA

I've attempted to reduce the star brightness and bring in more color to the stars.

Reduce Stars and Increase Star Color

(Download)

JimH123 Loc: Morgan Hill, CA

Certainly looking good on my cell phone!