Here is my first effort at combining 18 x 30 sec images of NGC5139 using a Pentax *istDS Digital SLR at the prime focus of my Vixen 4 inch refractor. The 30 sec images were captured from my back yard in light polluted Brisbane and I am quite impressed with how the DSLR performed. The mount was just tracking with no autoguiding.
I also tried NGC5128 (Centaurus A) but only managed to squeeze off two images before clouds rolled in, so I cannot compare the performance of the Pentax on fuzzy stuff as opposed to in-your-face monster sized mega-bright globulars. The image is cropped about 1/8 of the original full frame.
Thanks for the complements. The images were captured in RAW mode (a native Pentax mode) and then I converted them to 8 bit tif's with the proprietary Pentax Photo Lab software. I used ImagePlus, (see http://www.mlunsold.com/ ), to align and then combine the images, followed by a default DDP in ImagePlus.
The stacking and DDP really makes this image, when compared to any one of the original, unprocessed 30 sec exposures, which look quite dull and washed out in comparison.
The sensitivity was ISO1600, manual focus, 30 sec exposures with the Pentax taking automatic, in-camera dark frames for each exposure. I forgot to take flat fields, but I don't think I needed them in the end.
Here is one of the 30 second, full frame, unprocessed images as a comparison. All I have done is convert it from RAW to tif to jpg at 50% quality and resampled it to 800x534.
I purchased the full version when it was Release 1.7 and now I think I am on 2.10. I've only dabbled with it so far, as historically I have used MIRA AP and Corel PhotoPaint for processing ccd images with my SBIG ST7E.
However, ImagePlus looks as if it has huge potential although it is heavily biased towards the Canon and Nikon DSLRs rather than the Pentax family.
Boy there are so many of programs out there, its hard to decide which ones to use, which ones are value for money and which ones are beginner programs, you know the ones with training wheels.
Congratulations on that capture fantastic really.
Now if you had said after three years practice I have produced this that would be something but first go ..mate brillant.
I must say comparing the results pre processed gives me hope.. All my images look sortta like the unprocessed shot.. so I live for the day I can work the sofeware as an expert.
alex
I've had over 3 years practice with my SBIG ST7E CCD camera. Although the ST7E is only B&W, what I have learned about image processing was very helpful in then using my Pentax DSLR. Apart from good polar alignment, good tracking and good focus, my best results have come from stacking lots of images and using the various image processing programs to display the image data to its best. The Omega Centauri image really jumped out of the screen after the stacking and DDP (Digital Data Processing) function in ImagePlus.
Keep on capturing and stacking Alex, the various images you have posted in this forum are great efforts and definitely results to be proud of.
CA - bugger, I thought that was nebulosity!!!!! I just resampled down to 1200 x 800 followed by a 50% jpeg compression. File size = 94k. It's not as good as the full res version but looks nice "hanging in space".
Cheers
Dennis
PS - did you receive the Qld Astrofest 2003 article and 3 batches of photos?
Stunning stuff Denis. I'm most impressed with you focus and tracking. You got it spot-on there. Keep it up.
Don't worrt about the CA.!! I never actually saw it until Mike pointed it out . Too busy starring into the heart of the glob..
Cheers
Thanks for the complements from across the pond in NZ. I had a peek at your website - just awesome; really enjoyed my tour of your great images, equipment and home made stuff.
Thanks for your comments Dennis! I've still got a wee way to go, but getting there!
I need to update the equipment pages, as I've got a bit of new stuff. Thanks for the prompting.
Cheers
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Dennis. Brilliant, literally 
What did you use to combine the images and what ISO speed?
. Too busy starring into the heart of the glob.. 
