IC1396 - HST palette (final part)

[Paramount]

Hi
I was lucky with the weather last night as, despite the forecast being for cloud it stayed clear long enough to get 3 hours of SII data to go with the Ha and OIII I had already got from previous nights. This is the first colour image where I have used full calibration which were as follows
16 bias frames
10x20 minute dark frames
16 dark subtracted flat field frames per filter with an average ADU count of 42-45,000
All the frames were calibrated and then stacked using sigma clip in Maxim DL. I colour combined in Maxim using a weighting of 7:1:3 for SII:Ha:OIII before gamma stretching and saving to 16 bit tiff.
In photoshop I did one aggressive curves stretch followed by a milder curves stretch with levels adjustments in between
Any gradient was taken care of with gradient xterminator
Several small contrast curves adjustments with levels in between to bring out more detail
To get the colours out better I used selective colour and finally I cropped the image to remove stacking artefacts
I estimated that the total processing time including calibration was about 2.5 hours
It was taken over 3 nights in June and July with a Takahashi FSQ106ED at f5, Starlight Xpress SXVF H36 autoguided by a SX Lodestar and OAG on a Paramount ME with 2 second guiding exposures with dithering invoked
Exposures were 12x20 minutes for Ha, 9x20 minutes for OIII, 9x20 minutes for SII with 5nm narrow band filters
Previous versions of this subject with different equipment can be see on the Nebulae and Nebulae 2 page in the image gallery of my website http://www.imagingtheheavens.co.uk

There is a full size high resolution version at the following link, it is over 11mb in size so it may take a while to download but I think it is worth the wait
http://www.pbase.com/imaging_the_hea...mage/126203748

Thanks for looking and following the progress on this image
Best wishes and clear skies
Gordon

http://www.imagingtheheavens.co.uk/u...396hst1000.jpg

[David Fitz-Henr]

Great result Gordon! I'm no expert on narrowband images, but to me it looks like you have achieved a good balance of colours there, and lots of good detail as well!
When you say you have dithering invoked, what software do you use for that? Does it automatically stop guiding, slew the scope a few arcseconds, compute where the guide star should now be (rather than have to re-select a guidestar) and then restart guiding?

[Paramount]

Originally Posted by David Fitz-Henr

Great result Gordon! I'm no expert on narrowband images, but to me it looks like you have achieved a good balance of colours there, and lots of good detail as well!
When you say you have dithering invoked, what software do you use for that? Does it automatically stop guiding, slew the scope a few arcseconds, compute where the guide star should now be (rather than have to re-select a guidestar) and then restart guiding?

Hi David
Thanks for the comments, dithering is part of the software within Maxim DL and it allows the guide camera to "dither" the mount in between each exposure from the main imaging camera where the guide camera moves the mount a small number of pixels in a randaom direction, the guide camera then resettles itself on the guide star and carries on guiding, it is important to set a delay between each of the main exposures in order for this to take place otherwise you may get a blurring of stars
Best wishes
Gordon

[CoolhandJo (Paul)]

very nice image. Colours are vibrant and stars pin point.