NGC 7635 Bubble Nebula

[ianaiken]

Well I think I've sorted out my processing problems with this one.  This is an HaRGB of the Bubble Nebula NGC 7635 taken between the 19th and 29th September 2013 during a rather high full moon with quite a bit of high haze.  Because of this it took quite a lot of subs to get some of the fainter stuff to show up.

Any feedback welcome.

[symesie04]

Looks great. Great detail and colour is great. Nice depth, really stunning. What were the sub details and kit Ian?

[iksose7]

Great looking Bubble, among the best i've seen this year

[ianaiken]

Many thanks for the feedback!

• Ha taken on an Atik 314L+ CCD on a Skywatcher 80 ED DS-Pro Telescope at a focal length of 510mm at f6.4.  55 sub-exposures taken at 1200s each. (18 hours)
• RGB taken with a QHY8L CCD on a Skywatcher 100 ED DS-Pro Telescope at a focal length of 765mm at f7.6.  42 sub -exposures taken at 900s and 15 sub-exposures at 1200s each. (15.5 Hours)
• Scopes are side by side on a pier mounted NEQ6 with an QHY5 OAG on the 80 ED.

Data captured during a full moon pretty much each night and also with a high cloud haze.  Subs were quite noisy and its wasn't dark enough to get great signal so I invested the time to leave the OBS capturing data otherwise I would end up with frankly nothing to show.  I think I may need to capture some more to try to reduce the noise a bit then pick from the best subs.  Ideally it would be nice to push it with two times more data and get around 40 hours for RGB and Ha.  I did capture some O3 but haven't done anything with that yet.  Not bad in my opinion given the conditions and making the best out of having no cloud and no strong wind.

[symesie04]

Thats impressive. 30 minute subs? tracking must be spot on.

[lensman57]

Many thanks for the feedback!

• Ha taken on an Atik 314L+ CCD on a Skywatcher 80 ED DS-Pro Telescope at a focal length of 510mm at f6.4.  55 sub-exposures taken at 1200s each. (18 hours)
• RGB taken with a QHY8L CCD on a Skywatcher 100 ED DS-Pro Telescope at a focal length of 765mm at f7.6.  42 sub -exposures taken at 900s and 15 sub-exposures at 1200s each. (15.5 Hours)
• Scopes are side by side on a pier mounted NEQ6 with an QHY5 OAG on the 80 ED.

Data captured during a full moon pretty much each night and also with a high cloud haze.  Subs were quite noisy and its wasn't dark enough to get great signal so I invested the time to leave the OBS capturing data otherwise I would end up with frankly nothing to show.  I think I may need to capture some more to try to reduce the noise a bit then pick from the best subs.  Ideally it would be nice to push it with two times more data and get around 40 hours for RGB and Ha.  I did capture some O3 but haven't done anything with that yet.  Not bad in my opinion given the conditions and making the best out of having no cloud and no strong wind.

Hi ,

That is looking great, may I ask how you combined the from two different scopes and chip sizes please?

Regards,

A.G

[ianaiken]

1200s = 20 min subs :-)

Tracking is good but 30 mins maybe a bit too much.  It's quite a lot of kit on the NEQ6 (about 17KG).  I had been doing 20 mins on the RGB but because this scope is the secondary the stars were suffering a bit from elongation so I dropped it to 900s.

To combine the subs I processed the RGB and Ha separately.  Then I merged them using PI.  Image scale is very similar being 2.1 arcsec/pixel from the QHY8L with the scope and reducer and 2.6 from the Atik on the 80.

1. Using PixInsight I used RGBWorkingSpace and set the Luminance Coefficients to 1 globally.  This prevents the red changing to pink when mixed with Ha (at least prevents it quite a bit).
2. Using PixInsight I then used StarAlginment process to align the RGB with the Ha (RGB has a much larger frame/resolution so is cropped by doing this).  This resulted in a new RGB image that matched the Ha in terms of alignment. 
3. Using both I then lazily used the script HaRVB-AIP to merge the two setting Ha to be 66% of the red channel and noise it to 3.  There is another method I have experimented with and I want to try in anger which is documented at http://pixinsight.com/tutorials/narrowband/theory/en.html
4. That's it.

Here are sample subs picked at random.

RGB 900s

Ha 1200s

[ianaiken]

For 20 mins I would have expected a lot more data on the Ha, but the moon and haze certainly stopped this.  It will be good to do a comparison on a better night to compare noise levels and see the different in what is captured.

[symesie04]

1200s = 20 min subs :-)

Doh school boy error. 

[Adamar98]

That's fantastic! A very crisp image. Nice one!

[laser_jock99]

Nice effort- would love to have the 'scope time' to try something like this.

[ianaiken]

It's the most scope time I've had all year!  But it's only 18 hours in total elapsed because it's side by side setup.  As a chap on SGL says "As long as it takes".  I think quite a good philosophy.

I've been running through some tutorials for PixInsight to do some noise reduction while the image is still linear so I'm going to have another go at processing this.  Using noise reducion when the image is still linear does yield better results as you seem to get more out of the image.

[andyo]

That is a fantastic capture the detail in the bubble is superb.Interesting about adding ha in pixinsight didn't know there was a script to do this.I have recently started using Atrous to reduce noise in the linear stage and find it achieves better results than doing it when the image has been stretched

[ianaiken]

Hi AndyO - many thanks.  There is good data there and some good detail, but I've found it is so easy to lose it or make a mess in the processing.  I used Atrous today to reduce noise in the linear stage and I can tell you that I was able to bring out the faint stuff without having to use GradientHDRCompression.  But I got a bit carried away with the processing and managed to lose the detail in the bubble... too much hist stretching I think.  Anyway I am going to revisit more slowly and process it again, both the Ha and RGB, using Atrous in the linear stage.  Juan posted in the PI forum a nice tutorial on using it and applying a mask which is basically a stretched version of the image.  Absolutely brilliant.