IC 4628 - The Prawn Nebula

batema (Mark) · #1 06-06-2010, 12:08 PM

Hi,

I thought I would have a crack a this object so using a QHY-9 through a William Optics Flt 110 guided with PHD and stacked Luminence and colours seperately in DSS. I then processed the stacked Lum to a happy point then aligned the colours in Photoshop manually in channels then processed colours. Layered the colour on top of the lum and then aligned these two using Luminosity and then colour.

!2 x 10 Min Lum with 6 x 5 Min RGB with darks but no flats at -20c.

My real question for showing this is after I alight the RGB image over the Lum and the centre stars are aligned if I go towards the outside of the image the stars no longer are aligned. Is this due to me not have a field flattener or is this field rotation or something else. I have included some screen shots of the centre and outside edges to show this.

Thanks,

Mark

bmitchell82 (Brendan) · #2 07-06-2010, 03:44 AM

it doesn't look like you have a field flattener. its kind of essential with a larger format CCD/CMOS sensor. keep it up your doing well.

multiweb (Marc) · #3 07-06-2010, 07:34 AM

Nice shot Mark. Looks like you have a bit of camera tilt but the focus, tracking and details are very good. Don't skimp on the flat fielding though. It will make a world of difference. Good work.

jjjnettie (Jeanette) · #4 07-06-2010, 09:47 AM

Nice one Mark.

It was, in Paul's words, a "Suimin" weekend. Between us all we were shooting Chickens and Prawns.

(well.....it sounded funny at the time)

batema (Mark) · #5 07-06-2010, 06:12 PM

It is funny JJJ. I would have loved to be there. Next time.

Hagar (Doug) · #6 07-06-2010, 06:23 PM

Hi Mark, I have had the same problems with separating colours after stacking and combining. You may find it is a combination of camera tilt in the focuser and also a registration problem due to field rotation. I found the requirement for a very good polar alignment and a very good reistration alignment program made a great difference. CCD Stack give the greatest flexibility in registration and alignment I have seen in quite a few software packages.

The incorporation of these two items returned me quite good results but as always, at a cost.