RASC Hamilton Pentax Astro Tracer

[David Galbraith]

Good point Gary!!

Cherish those hard-won photons.

cheers,

- David

________________________________
> From: gary at bendun.net 
> To: astronomers at hamiltonrasc.ca 
> Date: Sat, 30 Nov 2013 08:59:30 -0500 
> Subject: Re: RASC Hamilton Pentax Astro Tracer 
> 
> 
> 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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