Thread: SBig ST8300
View Single Post
  #62  
Old 04-11-2009, 06:52 AM
jase (Jason)
Registered User

jase is offline
 
Join Date: Sep 2006
Location: Melbourne, Victoria
Posts: 3,916
Frank, this is not a factor of blooming, but the dynamic range. Once the pixel wells reach their saturation on an ABG chip, the electrons bleed which stops the electronic charge spilling into surrounding pixels. The point here is that once the pixel wells are saturated and hit the 65k ADU limit (assuming 16bit AD conversion), you've lost data. Small dim stars are fine, but the large bright ones will place a bigger footprint on the chip, i.e. the star edges will also become saturated with time as can the general glow or halo. This coupled to the small pixel size (oversampled) will result in the bloating appearance.

Alex, yes, imaging through narrowband filters will reduce the impact given they cut a stars continuum energy. It doesn't solely negate the problem of limited well depth however. It will vastly depend what is in the FoV. Narrowband would lend its self to going longer. 3nm is as narrow as they come so as you suggest, you'll probably be able to 1200s subs, you'll need to experiment. Try a few scenes with bright stars to determine your limits in this configuration.
Reply With Quote