[vsnet-chat 2492] Re: ST6 - IR Blocking Filter

[aah@nofs.navy.mil]

Stan,
  Give us your optical system, please.  Any focal reducer?
What is the level of the effect?  Can you close off the
front end of the telescope and see if the effect remains?
Is it a function of exposure length or sky illumination?
  Remember, I-band is not infrared.  At K (2.2microns),
the thermal contribution from telescope and sky is just
starting to become important (which is why there is a
K-short filter defined, to cut this effect down by a
factor of 2), but for anything shorter than this, you
have to work hard to see any ground-based thermal radiation.
Arne

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