From: Milton Aupperle <milton@outcastsoft.com>

Date: January 23, 2009 2:23:09 PM MST

To: Astro_IIDC@yahoogroups.com

Subject: Re: [Astro_IIDC] Re: Stupid questions?

Hi Jesse;

One thing to consider is that the light loss is equal to difference in the square of the pixel dimensions.

So if one CCD has 5.6 micron pixels and another has 3.5 micron pixels, then the light capturing difference is (5.6*5.6) / (3.5*3.5) = 2.56 times. So to get the same image brightness with the 3.5 micron CCD as you will withy a 5.6 micron CCD, you need to expose the CCD for 2.56 times as long.

See these messages

http://tech.groups.yahoo.com/group/Astro_IIDC/message/623

http://tech.groups.yahoo.com/group/Astro_IIDC/message/2073

http://tech.groups.yahoo.com/group/Astro_IIDC/message/734

for more details on this and other topics.

HTH..

Milton Aupperle

On 23-Jan-09, at 1:57 PM, Jesse Ohlsson wrote:

Milton, sorry to ask stuff that was asked before.  I do appreciate the summary.

I'll be going with a mono 31AF03.AS from the Imaging Source.  I found the pixel size is 0.8

the pixel size on the 640x480 camera, and also it's the same size as on the 1280x960

camera.  My 7" Mak with a 2700mm focal length is never going to give wide fields for DSOs,

so I don't think I'll need the bigger chip that the 1/2" CCD offers.

Thanks for your advice.