Actually, a question on this data. What caused the FITS masters to have a mean background ADU value of .01? Is this a result of the way PI produces masters or the data being previously stretched?
Put another way, why has the pedestal value been blown away? Post calibration, what were the values of the subs? Were there any subs with a value below zero? A no point should this occur. If it does, you need to back track to find the root cause. This is the reason why all FITS apps add a pedestal value (typically 100 counts) to stop FITS becoming negative.
Actually, a question on this data. What caused the FITS masters to have a mean background ADU value of .01? Is this a result of the way PI produces masters or the data being previously stretched?
Put another way, why has the pedestal value been blown away? Post calibration, what were the values of the subs? Were there any subs with a value below zero? A no point should this occur. If it does, you need to back track to find the root cause. This is the reason why all FITS apps add a pedestal value (typically 100 counts) to stop FITS becoming negative.
Jase,
A pedestal isn't needed after calibration has been done and the data has been converted to 32-bit floating point.
Unfortunately, the FITS spec doesn't specify a standard range for floating point data values. PI uses a range 0..1 Other packages use different values. You can tell PI to use a different range when reading "foreign" FITS files.
I suspect the reason for using a pedestal with integer FITS files is actually to prevent underflow from generating large positive values when using 16-bit unsigned data. That would be more of a problem than a small negative value.
But it's a long time since I wrangled bits for a living, so maybe others know better than me
Apart from combining the colours and lum in CCDStack, it was processed entirely in PS CS5.1, using 2 actions and a little levels and curves. Nothing else except a double 50% Lum layered in luminosity to bring it out a bit.
Here's my next version Lee. As I said above, I misread your post and assumed you only had a synthetic luminance from your RGB data, so my previous attempt was based only on your RGB data. I used pretty much the same processing in this one. And of course one of the good things about PI is that you can save your work as a project, so when you reload the next day all the stuff you did before (images, history) is still there to be further processed. No lost work.
Differences were:
-- A deconvolution on your (real) luminance
--LRGBCombination with the real luminance rather than the synthetic one (which I still used as a mask)
--Some sharpening with AtrousWaveletTransform.
--Noise reduction withTVGDenoise
--Upped the saturation a bit with CurvesTransformation
--The odd Histogram tweak here and there.
All up this has been an interesting thread. I learned a couple of new tricks from PI Guru Rick's workflow above.
Geoff
Nice one, thanks Geoff! I'd never actually noticed the save project feature before. That's going to be really handy in future.
Quote:
Originally Posted by LewisM
Had a crack at it thanks Lee.
Apart from combining the colours and lum in CCDStack, it was processed entirely in PS CS5.1, using 2 actions and a little levels and curves. Nothing else except a double 50% Lum layered in luminosity to bring it out a bit.
Great work Lewis, kept the noise down well and with a really simple approach. For those using PS, do you mind sharing what actions you used (assuming these are commercially, or otherwise freely available actions).
Did the combine in CCDStack, with intial stretching done there also. Saved as 16bit TIFFS, including the Lum, and moved it to PS.
In PS, I initially selected the stars (Focal Pointe action), then played a bit with contrast, colour balance and saturation. Then I ran a mean saturation enhancement action (will find out later what it is called), removed all the green, and did a small masked sharpen (the stars already masked, so was easy) - something like a 15% sharpen only. Enhanced the contrast a little again selectivelly, and boosted the blue some. I forgot to enhance the H-a reds, but you can still see them. Ran an EXTREMELLY light tonal Contrast to bring out the dust lanes some more.
Black clipped the Lum slightly, layered 2 copies on top, reduced opacity to 50% each, layered in Luminosity (makes it pop, and darkens the background somewhat). Ran a very light denoise with Imagenomic's nose reduction filter
All in all, about 15 minute work.
I think most of what I did is covered with Annie's Actions, but I usually do it manually myself (more control over result)
