[vsnet-alert 12825] Re: SDSS J133941.11+484727.5: superhumps evolving?

[Taichi Kato]

Re: SDSS J133941.11+484727.5: superhumps evolving?

   Dear all observers,

   In addition to Ohshima-san's report, we have received observations
from Roger Pickard, Tim Crawford and Bart Staels.
However, it has turned out that this kind of bright object in a rather
sparse field is more difficult than observers would assume, and there
have been much inconsistencies between observers.  My impression is
that half observations do not satisfy the quality for analysis.

   Please keep in mind:

  (1) Even if the object is sufficiently bright, the use of a very faint
comparison star (2-3 mag fainter) ruins the expected high S/N and
makes it impossible to detect low-amplitude early superhumps.
Please use 10-11 mag comparison stars.

  (2) If your regular set-up is unfiltered photometry, the use of
filtered photometry would cause calibration difficulties, such as
flat-fielding or different dust patterns etc.
Please take good flat-fielding for the filter you currently use,
and check images if there are unexpected noise patterns.

  (3) There are sometimes sporadic patterns of brightening or fading,
which appear to be artificial.  Please confirm that there are no
dust patterns or hot/cold pixels after proper calibration, and confirm
any of objects or comparisons is not saturated.

   And unavoidably, observations should start at high air-mass.
This further complicates the problem, and try your best skill to
get the best result!