Atik 314L+ First Light - Crescent Nebula HaRGB

[Steve789]

So I've taken the plunge and bought a used Atik 314L+, manual filter wheel and a set of LRGB filters. Against all odds and seemingly disproving the theory linking new kit with cloud cover I was blessed with clear skies immediately after taking delivery of my new CCD.

The crescent nebula seemed a good target as the moon was still around and it gave me a chance to try the Astronomik Ha 12nm filter I'd bought earlier but hadn't really used.

I had to throw out a few of my Ha subs as I hadn't tightened the locking screw on the focuser enough and the focus shifted during the beginning of the session. Evidently the CCD and filter wheel assembly is a bit heavier than my DSLR.

I've spent the last few weeks learning PixInsight (which I love) so used it process this image. Somehow this has resulted in my crescent nebula having a pink/purple tint to it instead of the usual orange/red colour I see in other people's images. While I quite like my version I'd like to know why I haven't got the usual colour balance. The RGB data alone gives the same colours so it has nothing to do with the Ha data which I used as a luminance layer. Also the focus looks a bit soft despite using a Bahtinov mask and throwing out the earlier unfocused shots.

Ha - 13x600 sec

R,G & B - 3x420 sec 2x2 bin

All criticism welcome.

[Astroboffin]

No criticism at all, superb image

Well done

AB

[toxic]

very good image thumbs up

[MattJenko]

How does the histogram look in PI - did you use the ColorCalibration tool at the linear stage and are all the channels balanced? If so then you can use the ColorSaturation process to tone down the purples. The purple comes from a lack of Green, so I am wondering if you went to town on SCNR or there was something amiss with the Green data?

I have the 414 so the same sized chip and I find that using bin 2x2 gave me really blocky images, even with a 1x1 Luminance, so I don't bother any more. I would also not necessarily use Ha as a Lum, but as a boost to the Red channel, but to fair, that Ha data does look nice and crisp. Another thing I have started doing is quick sets of 1 min subs for RGB stars to overlay if the star colour is saturated out, as in the case with yours.

This is all criticism of what is a very fine and detailed image - that 314 is a proper camera!

[lensman57]

Excellent first light. To add the Ha in PI you can use the NBRGB script. I usually import the RGB and Ha data into PS after processing in PI and then split the channels of the RGB highlighting the R only and then paste Ha on to the R channel. Ha can then again be added to the final image as L but the percentage should be a lot less than 100. A star mask is also used to protect the stars and the background to prevent everything from going purple and magenta.

In Pi you can also do this using pixel math if you are up to it.

Regards,

A.G

[Steve789]

Thanks for the comments everyone. I've been amazed at what PixInsight can do and I'll definitely be purchasing it when my trial runs out. It is a massive learning curve and at the moment I'm right at the bottom of that curve! I've been following some of the workflow examples at http://lightvortexastronomy.blogspot.co.uk/ which have served as a great introduction to the software.

I'm pretty sure I did the color calibration at the linear stage, here's the histogram

I applied SCNR once with the default settings (because it was in one of the workflows I was following not because I knew what I was doing!).

[MattJenko]

If you put the stacked files on dropbox or somewhere accessbile, I will have a play rather than guess if you want.

[Davey-T]

Nice image, I have an Atik 314L and it has different sensitivity in R,G & B so have to adjust images accordingly, got it written down somewhere in one of my many notebooks but can't find it ATM.

Dave

[glowingturnip]

i don't usually use SNCR nowadays - if you've done a good DBE and background neutralisation and colour calibration, then you probably won't need to do an SNCR, and in this case it probably has added to your magenta  - your green curve is definitely off to the left

[Steve789]

Thanks for all the suggestions, I'll have a go at processing it again when I have time.

MattJenko, that's a kind offer but this being only the first time I've tried processing images with my new set-up I'll have a go myself, thanks.

[lensman57]

Thanks for the comments everyone. I've been amazed at what PixInsight can do and I'll definitely be purchasing it when my trial runs out. It is a massive learning curve and at the moment I'm right at the bottom of that curve! I've been following some of the workflow examples at http://lightvortexastronomy.blogspot.co.uk/ which have served as a great introduction to the software.

I'm pretty sure I did the color calibration at the linear stage, here's the histogram

crescent_Hist.jpg

I applied SCNR once with the default settings (because it was in one of the workflows I was following not because I knew what I was doing!).

Use the Histogram transformation and pick out the red channel, move the middle slider to the right ever so slightly and apply the instance and then judge the result. You should really aim to have the left side of the curves intersecting and the peaks lined up. This will not apply if you are in the middle of a large Ha rich nebula, the Ha will inevitably dominate. you should also be very careful how and when to apply SCNR and by how much. The default setting is a little too strong at times.

A.G

[ollypenrice]

This is a classic case of mono CCD giving a geat result straight off. 

I'm not a fan of global processing in PI but clearly it can be done and this is good. When Ha goes into luminance it does give a pink-purple caste and since Ha isn't luminance, but deep red, I prefer to combine it as such in Ps Red channel. But this has worked well. Who cares?

On SCNR, I use it on every natural colour image I ever take, without fail. I don't make any claims about this, it's just an observation.

Great start and I guess you're pretty pleased. You should be.

Olly

[gingergeek]

Excellent work Steve, you should be rightly proud

[nightster]

Congrats on a beauty. More mono converts every day. More unbelievable amateur images every moon cycle.

[Astrosurf]

Cracking image!

Alexxx