M101 LHaRGB 30 Hours

[HunterHarling]

Finally I have finished this image! This is officially my longest ever integration, also my first galaxy image that I have added hydrogen alpha to.

Edge HD 800

Asi1600mm pro

Zwo LRGB HA filters

10hrs luminescence, 15hrs RGB, and 5hrs Ha. Processed in Pixinsight.

As always, comments and advice welcome.

Thanks for looking.

[wimvb]

Excellent image! Also an example of "you can never have too much data". What single frame exposure times did you use? I can imagine that 30 hours with an ASI can fill up a good part of even a large hard drive.

[HunterHarling]

Thanks, Wim!

I used 3min exposures for luminescence, 4min exposures for RGB, and 5min exposures for Ha.

I don't know how much of the hard drive this image took up, but the computer is a bit slower now?

[wimvb]

3 hours ago, HunterHarling said:

Thanks, Wim!

I used 3min exposures for luminescence, 4min exposures for RGB, and 5min exposures for Ha.

I don't know how much of the hard drive this image took up, but the computer is a bit slower now?

I get that to 485 frames. At 32 MB each, that's 15.5 GB of raw data. A lot more I guess, once PixInsight has calibrated them. That's a big chunk of hard drive for this project.

[Allinthehead]

Very nice image. Can i ask how you applied the Ha?

[HunterHarling]

32 minutes ago, Allinthehead said:

Very nice image. Can i ask how you applied the Ha?

I masked the datk parts of the ha image and stretched only the bright parts. Then I black clipped the dark parts to black, and added the ha to the red channel.

 

Think it is too red in the center?

[Allinthehead]

37 minutes ago, HunterHarling said:

I masked the datk parts of the ha image and stretched only the bright parts. Then I black clipped the dark parts to black, and added the ha to the red channel.

 

Think it is too red in the center?

Thanks. Maybe a little pink in the center. I'm not sure how this galaxy should look as i've never imaged it. A quick google showed this Link

[HunterHarling]

Here's with updated color:

2 hours ago, Allinthehead said:

A quick google showed this Link

If only I had a space telescope...

[wimvb]

3 hours ago, HunterHarling said:

I masked the datk parts of the ha image and stretched only the bright parts. Then I black clipped the dark parts to black, and added the ha to the red channel.

 

Think it is too red in the center?

There is a nb-rgb script in PixInsight that can give quite decent results. There's also a tutorial on lightvortexastronomy which describes a good method. I would be careful using masks while stretching and avoid clipping data.

That being noted, your image looks good, so your method must have worked.

[gorann]

I really like this image, with a lot of detail and nice Ha regions standing out!

If I should have some comments I also think it is a bit too pink, even in the last version. The big star to the left looks a bit odd, possibly being affected by some optical shortcommings  (the halo being squarish in shape and with colour artefacts) so maybe just get rid of it by cropping the image, which would also move the galaxy towards the centre. Just a thought....

[HunterHarling]

2 hours ago, gorann said:

I really like this image, with a lot of detail and nice Ha regions standing out!

 

If I should have some comments I also think it is a bit too pink, even in the last version. The big star to the left looks a bit odd, possibly being affected by some optical shortcommings  (the halo being squarish in shape and with colour artefacts) so maybe just get rid of it by cropping the image, which would also move the galaxy towards the centre. Just a thought....

 

Thanks.

The asi1600 dose not have anti reflective glass in front of the sensor, so all bright stars have strange diffraction around them. A shame because it is such a great camera, but I guss everything can't be perfect...

I believe the pink is from the Ha, I'm going to try to suppress it in processing so expect an updated version.

[HunterHarling]

Here's version 3:

[wimvb]

7 hours ago, gorann said:

The big star to the left looks a bit odd, possibly being affected by some optical shortcommings  (the halo being squarish in shape and with colour artefacts

That's caused by diffraction and possibly reflections from the microlenses. It's difficult to avoid. There are a few methods in PixInsight for halo removal, but I've never used them. And afaIk, most are for removal of round reflections.

Maybe one method here:

http://pixinsight.com.ar/en/processing-examples.html

[gorann]

In PS these halos can at least be suppressed easily using curves selectively. First check the sky background lightness with the picker. In this image it was about 30/30/30. Then anchor the curve from 30 and below. Then bring down the brightness above that point (but less in the brightest part of the histogram so the star will still shine). Then use the brush tool on the curves mask and only apply the curves selectively to the stars with halos. This was a 5 min job (but maybe a bit quick and drity - but works as a demonstration).