[Aavso-photometry] GMRT Campaign Update

[Brad Walter]

Captured about 4.5 hours of V data last night for 70 Vir using a
restricted aperture on a 10" cassegrain variant fitted with an ST7E
NABG. That got me to 7 second exposures for around 20,000 ADUs. I used a
76mm off-center hole as the restriction. The restricted aperture caused
some "bloating" of the bright object star similar to the effect of a
poor seeing night with an unrestricted telescope.  The flats for this
configuration also showed significant off-center vignetting that results
from the restriction. The flats should correct for it but since the
intensity variation over the surface of the chip is 5 to 6 times as
great as with an unrestricted aperture, I expect it to cause some
reduction in accuracy.

Has anyone experimented with an annular ring restriction rather than an
off center hole? The vanes to hold the center of the inner obstruction
of the annulus in place could be made to line up with the secondary
holder vanes to mitigate any additional spiking.  

-----Original Message-----
From: aavso-photometry-bounces at mira.aavso.org
[mailto:aavso-photometry-bounces at mira.aavso.org] On Behalf Of Aaron
Price
Sent: Tuesday, March 15, 2005 1:50 PM
To: aavso-photometry at aavso.org
Subject: [Aavso-photometry] GMRT Campaign Update


   Well it seems like this campaign was asking just a little too much
with too little lead time. We only have 2 people submitting data on one
of the targets.  Thanks to CTX and JJI for stepping up to the plate!
They both have scored lots of brownie points and respect. These are
challenging objects and it is nice to see people push their own envelope
and doing what is needed to get the job done.

   I have made light curves of their 3 nights of data and placed them
here:
                               http://www.aavso.org/news/gmrt.shtml

  It's not to late to help out! If anyone has a chance, please observe
as much as possible unil 13:30 UT on the 17th. 70 Vir seems to be the
object of choice so make that one your first priority.

  Good luck!

-- 
Aaron
_______________________________________________
Aavso-photometry mailing list
Aavso-photometry at mira.aavso.org
http://www.aavso.org/mailman/listinfo/aavso-photometry