[vsnet-chat 4818] Re: V4739 Sgr field measures

[aah@nofs.navy.mil]

Berto Monard wrote:
>A real pity that Arne's telescope will scratch some part of
>the structure when trying to measure this field...
  The 1.0m has a hard limit around -31Dec, and a soft limit
at -27.5Dec.  I will on occasion override the soft limit when an
important observation is to be made, but never override the
hard limit.  This is an old telescope with lots of mercury
around, and you don't want to push anything outside of its
normal operating conditions.
  In addition, -30Dec is at airmass 2.7 when transiting at
Flagstaff.  This is again into a questionable range when trying
to determine extinction and second-order color effects.  I don't
trust my photometry very well for such observations!  It is
far better if someone in the southern hemisphere took up the
challenge to obtain field photometry for fields south of, say,
-25Dec.  I'm surprised that Kilmarten et al. haven't published
any comparison stars for the recent southern novae; they certainly
have been obtaining filtered photometry.
Arne

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