Hi folks,
I recently started a first long time project with the cygnus wall as target. The night I took my first subs (Ha) was moonless and I got 9 frames of 10 minutes each. Then clouds came in and I have to abort the session. Two days ago, I was able to get some more subs (40 of 10 minutes each) of the target. Because of the full moon, I decided to shoot Ha again. That should be the only filter to use in those conditions. I have a house nearby a small hill and the moon rises behind the hill. So for about two hours, the images were quite contrasty. As the moon climbs up and brightened the night sky badly, the images were really flat which I expected, although I hoped the subs look better.
Yesterday I had a little time and did some tests to integrate the subs in different ways. I processes the first night (without the moon) seperately, the second night (full moon) seperately and then all the subs together without sorting bad ones out (in terms of contrast). I used the Weighted Batch Pre Processing script in PixInsight. All shown images are heavy crops of the same region. What I saw was the following:
1.) First night (moonless)
Here I got a noisy image. This was expected because there was only 90 minutes of integration time. The contrast was quite good, because the subs also had a good contrast.
2.) Second night(full moon)
The master light frame was much cleaner in terms of noise. This was also expected, because the integration time was about 6 hours. Because of the flat subs, the contrast of the master frame was also flat. But it seems, the details of the dust regions were there and the contrast of the master is better than that of the single subs.
3.) All subs together
Then I combined all the subs together. The details in the master frame (8 hours integration time) were really nice and the noise level was negligiable. The contrast is not as good as that from the first night, but was not bad either. The final image was really usable. This image was (also as expected) the best one out of the three. I guess, the weighting part of the script may have done a good job here.
4.) All subs together (contrast enhanced a bit)
I enhanced the contrast of the third image a bit. Of course, the noise is more visible now, but it is no issue.
So why this topic?
I'd like to ask you as experienced (or maybe even not so) astro photographers, how you deal with your own subs. Do you reject the subs with this heavy kind of light pollution caused by the moon, that were perfect in any other way? Do you keep them to stack them into your final image? Are there any other thoughts that I may think about?
I know about the theory. But the final result stacking all the images was surprisingly good. I guess, there is a difference in "what should be done" and "what is really done" by astro photographers.
Thank you, for your opinions.
Clear Skies
Christian
I recently started a first long time project with the cygnus wall as target. The night I took my first subs (Ha) was moonless and I got 9 frames of 10 minutes each. Then clouds came in and I have to abort the session. Two days ago, I was able to get some more subs (40 of 10 minutes each) of the target. Because of the full moon, I decided to shoot Ha again. That should be the only filter to use in those conditions. I have a house nearby a small hill and the moon rises behind the hill. So for about two hours, the images were quite contrasty. As the moon climbs up and brightened the night sky badly, the images were really flat which I expected, although I hoped the subs look better.
Yesterday I had a little time and did some tests to integrate the subs in different ways. I processes the first night (without the moon) seperately, the second night (full moon) seperately and then all the subs together without sorting bad ones out (in terms of contrast). I used the Weighted Batch Pre Processing script in PixInsight. All shown images are heavy crops of the same region. What I saw was the following:
1.) First night (moonless)
Here I got a noisy image. This was expected because there was only 90 minutes of integration time. The contrast was quite good, because the subs also had a good contrast.
2.) Second night(full moon)
The master light frame was much cleaner in terms of noise. This was also expected, because the integration time was about 6 hours. Because of the flat subs, the contrast of the master frame was also flat. But it seems, the details of the dust regions were there and the contrast of the master is better than that of the single subs.
3.) All subs together
Then I combined all the subs together. The details in the master frame (8 hours integration time) were really nice and the noise level was negligiable. The contrast is not as good as that from the first night, but was not bad either. The final image was really usable. This image was (also as expected) the best one out of the three. I guess, the weighting part of the script may have done a good job here.
4.) All subs together (contrast enhanced a bit)
I enhanced the contrast of the third image a bit. Of course, the noise is more visible now, but it is no issue.
So why this topic?
I'd like to ask you as experienced (or maybe even not so) astro photographers, how you deal with your own subs. Do you reject the subs with this heavy kind of light pollution caused by the moon, that were perfect in any other way? Do you keep them to stack them into your final image? Are there any other thoughts that I may think about?
I know about the theory. But the final result stacking all the images was surprisingly good. I guess, there is a difference in "what should be done" and "what is really done" by astro photographers.
Thank you, for your opinions.
Clear Skies
Christian
