NGC6888 Crescent Nebula DSLR

[cloudbuster]

My first crescent nebula....not nearly enough subs, as had to leave early as girlfriend taken ill. left gear with Andy, and accidentally ran a red light on way home! (girlfriend fine now). Here's the details of the pic:

Peasedown St John 25.5.12

skywatcher 200pds 8"

Canon 40d

CLS light pollution filter

800 asa

7 subs 12 1/2 min

30 flats 1/60 tv mode (flat field panel...thanks to Andy!)

8 darks 12 min

40 bias 1/8000th sec

stacked in DSS

Processed in Pixinsight

did actually image this subject a few nights earlier, but need Andy's help...yet again....to merge the images. Thanks for looking, and please add comments, suggestions etc.

cheers

bob

[cloudbuster]

ps. should add that this is only a rough stretch...no DBE yet....toooo tired!

[swag72]

That looks good for starters. As you know you need some DBE magic I'll not remind you!

Also, not sure how things work with your scope, but do you use a reducer / coma thingie? I ask as the stars at the corners are moving towards the middle, especially top right and left. I wonder what you can do with your setup to combat that? Of course, you could always crop them out!!!

[Gina]

Great image for a small amount of data and just a quick process - looking good

[JohnC64]

Nice and crisp there Couldbuster. You are also getting some of the background Ha coming out there too. My image of the Crescent had 5 minute subs but your 12.5 minute subs do bring out the fainter detail.

John

[ollypenrice]

It certainly is good despite the interruption!

I'm surprized that you have so much residual vignetting after flats and suspect they are not working for some reason. Yes, DBE will do it but it shouldn't be necessary.

Olly

[Quatermass]

Looking great I really struggled with my short subs on this one needed my guiding system set up to really do it justice.

[AndyUK]

Hi Bob - It's a very good image for so few subs, but the depth with the 12.5 min subs certainly shows through (and good focus too !).

I must admit, coma aside (you know about that), I too was surprised about the vignetting, but I have to hold my hand up for taking the flats... However, they were taken at about 40% full well capacity, so they should have been okay . I'm a bit bemused... Maybe you can send me a copy of a single raw flat and a single raw sub so that I can have a quick look...? And I can talk you through multi-session stacking later...

[cloudbuster]

thanks guys and gals...and especially andy. i too am surprised by the vignetting...i checked the graph on the camera, and the spike seemed a little over to the right for the flats....not sure how far i can get away with. with andys help, i'm gonna re-stack this image with data from a previous night...not too worried at this stage...cygnus is well up and i have time to put things right.

cheers

bob

[angusb1]

Nice work Bob, focus is bang on. When you restack it are you going to use the same flats or do you have some others you can use?

[cloudbuster]

Hi again all

Just added an extra bit of data from a later session. still only a rough stretch, with cropping.

hope u like!

cheers

bob

[Gina]

Oh yes, that's better

[AndyUK]

I agree - It certainly proves the value of adding more data (and the additional data / restack's removed the gradient too ).