[vsnet-chat 1316] sequences

[aah@nofs.navy.mil]

  Our monsoon, in its last hurrah, took out our firewall and internal
network with several well-placed lightning strikes.  Therefore,
our internet connection has been broken for the past week.  If
anyone has been trying to get in contact with me, I would appreciate
it if you would resend your message.
  As mentioned a couple of weeks ago, I made the offer of performing
'service observing' to determine sequences in requested variable
star fields during my September and October observing runs.  Six
observers took advantage of that offer, and sent me requests on
24 fields.  I have now obtained photometry in all of those fields,
along with two VSNET fields that sounded interesting: Var63 Peg,
suggested by Dr. Antipin as a new UG-type variable, and Kato's faint
object in Triangulum, which he suggested might be a dwarf nova.
The photometry will be posted on
      http://ftp.nofs.navy.mil/pub/outgoing/aah/sequence
in the next day or so, with one file per field.  There will be a
readme.1st file also that includes file format details and any
limitations for the photometry.  I am also re-processing the
two-dozen sequences I did earlier this year as a pilot study for
the AAVSO, and will post those results in the same directory.
  Note that these files are not 'sequences' in the strictest sense.
They are the output from an automated photometry system, and so
reflect the position, magnitude and color of *every* detected star
within my 11arcmin field of view.  Each observer needs to parse
the list for his star and pick out a smaller subset of stars to
present to the community as the 'visual sequence' for the field.
I strongly suggest a format such as that used by Bruce Sumner in
his recent postings for RY Ser and V1089 Sgr on vsnet-chat, with
the addition of error columns for V and (B-V).
  Sequence photometry is not difficult for those with at least two
filters, a CCD camera, and photometric skies.  I will post on
     http://vsnet.flagstaff.az.us/~ccdir/tutorial.html
a short article on how I approached the problem for these two-dozen
fields.  This might be used as a 'cookbook' for those new to
all-sky photometry.  As Kato and Skiff have mentioned, there are
several other methods that can be used with reasonable results,
especially for those cases where only a few hours/night are
photometric and sequences are desparately needed.  I would really
like to see a few observers get interested in performing this
service to the community, especially if they are in the southern
hemisphere.  While initiatives such as the AAVSO chart revision
project will eventually create sequences around the stars in
their respective lists, there are always new discoveries (new
novae, SNe, CV candidates, etc.) for which continuing sequence
photometry is necessary.  I am willing to help anyone who wishes
to get involved -- just drop me a line.
  My October run still has a few slots for sequences, if any other
observers have special requests.  The constraints are similar:
magnitude range fainter than V=12 (Tycho covers everything
brighter than this), RA range from 19 to 07 hours,
any declination north of -30.  I would prefer a detailed submission,
including star name, coordinates, variable type, requested magnitude
range for the sequence, and any notes that might help me identify
the field, select positioning (like bright stars to avoid), choose
filters (mostly I use B&V for creating visual sequences, but you
might want BVRI or even UBVRI for other projects), etc.  The more
information you give me, the more likely it is that your sequence
request will be included!
Arne
--------------------------------------------------------------------
Arne Henden                               Instruments/software/CCDs
US Naval Observatory Flagstaff Station    Cepheids/photometry/IR
P.O. Box 1149                             http://ftp.nofs.navy.mil  
Flagstaff, AZ 86002-1149                  Voice: (520)779-5132
aah@nofs.navy.mil                         FAX:   (520)774-3626

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