NGC7000 from Rother Valley DSC

[JonH]

NGC7000 taken at Rother Valley DSC

14 x 5min subs
Equinox ED80
NEQ6 with EQMOD
QHY5 on Startravel 80
Modified Canon 450D with CLS filter

Stacked in Iris and Processed in Photoshop
I had a lot of trouble getting DSS to stack this image despite trying countless times, eventually gave up and did it with Iris, not as easy to use but the results I find are much more reliable. Think I will stick to Iris for stacking from now on!

I'm not sure how this will look, on my rather old laptop I'm pretty happy with it but on my TV it might as well be a totally different image! Looks far too red and most of the detail has vanished! So as for how it is going to look to everyone else I haven't a clue....



Bigger version here:
http://farm9.staticflickr.com/8177/8068635711_557fc05fc4_k.jpg

[mickw]

You've  got a good result there Jon

I do think it looks a bit too bright though

[JonH]

On my work computer it looks to red too, looks like i'm going to have to redo it!

[MarkS]

You've got some good data there Jon.  Once you've cured your "red" problem it'll look really good.

The problem you had with DSS was possibly related to the huge number of stars in the image.  That is also sometimes a problem with IRIS: "Too many stars".  If you ever get that message, just use the command setfindstar to increase the number of standard deviations used as the threshold for detecting stars.   I find "setfindstar 15" (or even 20 instead of the default 7) works pretty well in a star filled image like that one.

Mark

[JonH]

Funny you should say that, because I had that exact problem with Iris when trying to use global matching! But I didn't know how to clanged the threshold so just used the three matching zone instead.
Thanks Mark, that should help me for next time. In fact might even re-stack this now!

[Carole]

It's looking good Jon, to change the brightness and tone the red down you don't need to re-stack, just tone it down in photoshop.  Or, go back to your unprocessed stack (I assume you have kept it), and try the processing again.  Also don't forget to hang on to the white point in curves when stretching the nebula so you don't stretch the stars as well.

Carole

[MarkS]

Since you're using IRIS anyway, you could do some or all of the post-stack processing in IRIS.  But if you must use Photoshop then do yourself a favour and at least use the IRIS (asinh) colour stretch before exporting it to Photoshop.  It'll make a huge difference to your star colours. 

[JonH]

The only reason I want to re-stack is because there is something odd still going on with the stars along the top that I want to remove. Possibly being caused by not turning off the auto rotate feature on the camera and half the subs being the other way round, I might also try staking doing a stack of each half of the subs and then see if they will align better manually. But haven't a clue how to do that yet!

I don't have to use photoshop at all, I want to use whatever will give me the best results and can figure out how to use really, I only just started getting to grips with photoshop in the last few days.
If there is anything I can do that will make it easier or better than I will try it, I am liking Iris so far for stacking as it has given me much better results than DSS but haven't tried to do any other processing with it yet.

[The Thing]

My last few deep sky images were done entirely in Iris. I don't have Photoshop and don't miss it, I suspect I would spend hours tweaking setings and trying esoteric techniques instead of getting a result. I use Gimp or Irfanview for final little tweaks if needed e.g gamma though I could do this in Iris as well.

[JonH]

I need to put some proper time in to figuring out Iris, unfortunately time is something I am quite short of lately though!

[RobertM]

Jon,

That's a really excellent result for a DSLR !  I would agree that it's a bit too bright and that has also had the effect of making the stars a bit large which detracts a bit from the nebulosity (in my eyes anyway).  In any case it's a great capture for that many subs.

Robert

[JonH]

Ok then, I have spent a few hours having another shot at this, but using my TV rather than the laptop screen in an attempt to get the brightness and red levels right, but there is a chance I have gone too far the other direction now?...
You'll have to bear with me, I'm getting there slowly!



Larger version:
http://farm9.staticflickr.com/8312/8071308730_4dcaf1b486_k.jpg

[RobertM]

No I don't think you've gone to far at all, in fact I think it's miles better.  The stars are smaller and the image has more of the other colours showing in the nebula.  Don't forget that it isn't just the red Ha light in the nebula that you recorded but Hb and OIII (mainly) as well.  You've also brought out much more detail and are probably near the limit of what those subs can give,

Overall I think it's a really excellent reprocess.

Robert

[JonH]

Thanks Robert, I'm pretty happy with it. I can't help but wonder how much more detail there would be had I not used the CLS filter though! But that's all part of the learning curve.
What's bizarre is on my laptop it looks mostly grey! From now on think I will stick to using the TV for processing as this confirms my old laptop screen just isn't up to the job!

[RobertM]

Yes I think the CLS is overkill, something like a IDAS LPS-P2 or Baader Neodymium may be better for darker skies.