From: "Steve Bryson" <stevebeam@yahoo.com>

Date: November 23, 2005 1:33:37 AM MST

To: Astro_IIDC@yahoogroups.com

Subject: Resolution vs. sensitivity


Hello everyone - I'm still working on choosing my next camera.  Based on Alan's pictures 

I'm not inclined to pay the higher prices of the PGR cameras, but I can't decide on which 

imaging source  camera.  I understand that we might want to give sensitivity a priority, but 

it's hard for me to let go of increased resolution.  What do you think of following analysis 

of the DMK 640x480 vs 1024x768 cameras?


DMK 21A/BF04 (640x480): pixel size 5.6 microns, pixel area 31.36

DMK 31A/BF03 (1024x768): pixel size 4.65 microns, pixel area 21.62

area of 640x480 pixel/area of 1024x768 pixel = 1.45


So each pixel of the 640x480 camera captures 1.45 times more light, so (assuming 

everything's linear) the 1024x768 camera will require exposures about 45% longer for the 

same image.  This is a little less than half a stop.  This impression I get in this newsgroup 

is that these cameras have much higher gain than the fire-i, so a half-stop doesn't sound 

to me like a big deal.  Therefore I'm inclining towards the higher resolution.  The 

difference for the 640x480 flea is much larger, however.


Also (as Tim points out) the larger chip of the 1024x768 camera gives a larger field of 

view which makes finding objects easier.  This is a serious consideration with my 

motorized dob mount, where simply changing the filter in the filter wheel can knock Mars 

out of the field of view (very frustrating).  


On the other hand I do not expect to ever get better resolution than Alan with his 

640x480 camera.  


Any thoughts would be appreciated

Steve