RASC Hamilton Pentax Astro Tracer

[Gary Bennett]

I would not feel comfortable allowing DSLR camera software, designed for daylight photography, to be smart enough to decide that the faint photons I worked so hard to capture are noise and got deleted.

 

Gary Bennett

 

http://bendun.net/

http://photos.bendun.net/

 

From: astronomers [mailto:astronomers-bounces at hamiltonrasc.ca] On Behalf Of Mark Kaye
Sent: November-30-13 8:38 AM
To: astronomers at hamiltonrasc.ca
Subject: Re: RASC Hamilton Pentax Astro Tracer

 

On 13-11-30 8:28, David Galbraith wrote: 

There's compression and then there's compression. "lossless compression" changes file size without altering pixel-by-pixel raster data. Lossy compression (like JPG) alters the bitmap data to save file space. Some cameras can store data straight to TIFF files. No loss.


   I do not declare to be an expert on digital imaging.  I can only guess that the way a dark raw is compressed and data frames are compressed is enough different that an external dark subtraction is not quite as good as an internal.  I am only the messenger here.  I concede that doing your own dark subtraction is attractive given that we have limited actual dark sky time and that doing internal darks cuts one's imaging time in half.
   It could also be possibly because the dark frame done in the camera is done at pretty much exactly the same conditions, while a dark library is slightly different.  As originally stated, both Terry and Alan conclude that in camera dark subtraction is marginally better.  They do have the experience in this sort of thing to be taken seriously.  But imaging a moving object like a comet, where you have a very limited window for imaging, you are going to be better served by using a dark library.



-- 
   Clear Skies!
               MK
 
http://www3.sympatico.ca/mark.kaye/index.htm
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