From: gregharp_at_antispamdomain.not
Date: Wed Nov 26 2003 - 15:05:36 EST
Steve,
I'm still hoping to prove to myself that due to the linear response of the
sensor, taking (for example) 75 x 1 minute exposures and adding them up
(simple addition) in sets of five (after calibration and alignment) will
produce effectively the same signal information as 15 x 5 minutes. The 15
resulting images could then be processed in whatever way 15 x 5 minute
exposure of that region would need to be processed (presumably one of the
averaging algorithms such as min/max excluded).
Unfortunately high, thin clouds cut short my imaging session of that part of
the sky on Monday night so I only got 15 usable 60-second exposures. I got
16 more with halos around the brighter stars, which is a real problem since
Alnitak producing a large halo pretty much blows away a good part of IC 434
and NGC 2024.
Of course, I never delete anything so I'll keep those around for whenever I
can get more exposures of the area under dark skies or through a filter.
When I get some time I still need to try and process those 15 into something
I can share as a work in progress.
--Greg
> From: sc02492 [mailto:sc02492_.at._yahoo.com]
[...]
>
> So the strategy is to take many frames at relatively short exposure,
> with subsequent dark frame subtraction (calibration), alignment, and
> stacking to increase the signal to noise ratio. Some argue about how
> short is short, but in general I find that it's better to stack 15 x
> 5 minute, guided exposures compared to 75 x 1 minute, unguided
> exposures (better as defined by capturing the faint stuff and still
> maintaining an acceptable background).
[...]
------------------------ Yahoo! Groups Sponsor ---------------------~-->
Buy Ink Cartridges or Refill Kits for your HP, Epson, Canon or Lexmark
Printer at MyInks.com. Free s/h on orders $50 or more to the US & Canada.
http://www.c1tracking.com/l.asp?cid=5511
http://us.click.yahoo.com/mOAaAA/3exGAA/qnsNAA/N_XolB/TM
---------------------------------------------------------------------~->
Before posting an image to our group please read the space mangement guidelines:
http://groups.yahoo.com/group/digital_astro/files/Photos%20Section%20Space%20Management%20Guidelines
Please check the digital_astro FAQ at:
http://www.szykman.com/Astro/AstroDigiCamFAQ.html
Be sure to visit the digital_astro Gallery and Archive at:
http://velatron.com/dca/gallery
http://velatron.com/dca/archive
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
This archive was generated by hypermail 2.1.7 : Wed Nov 26 2003 - 15:08:17 EST