Subject: Guider performance last night

From: Eric Deutsch

Submitted: Thu, 12 Oct 95 13:31:04 -0700

Message number: 6 (previous: 5, next: 7 up: Index)

Slightly modified and reposted to apo35-dis:

For those interested in the 3.5m Guider performance, I'd like to expand
a little on last night's nightly log:

Don Hoard was observing radial velocities of a close binary with DIS in
high-res mode.  Since he was to be sitting on one object for a long
time, this made for an ideal guiding test.

After slewing to the object, we rotated to an InstAng=+30 in order to
put a suitable guide star (whose position was known to be appropriate
before observations began) in the Guider field of view.  The object was
a 14.1 magnitude HST GSC star.  Because the DIS instrument block
appears not to be correct, some jockeying was required to get the
target in the slit and the guide star in the Guider FOV.  With the red
filter we got 77,000 counts in 10 seconds.  Guiding was started and
continued for 3 hours and 40 minutes.  Guiding was halted at that point
when the target reached 3.3 airmasses, although the Guider was still
working fine.  The flux level of the 5-minute spectra obtained over the
3:40 hours indicates that the star stayed in the slit the whole time.

Note that while we were close to full moon, sky background was
minimal.  I measured a S/N for the star (before guiding began) of
~150.  With dark subtraction, it would be ~230.  Again, from the image
before guiding began, the star had 77,000 total counts, and a FWHM of
1.75'' and a peak of 3900 counts (10 second exposure).  The time interval
between the close and open of the shutter during guiding appears to be
3 seconds.

I do believe that this was the first guided science observation.

Before routine guiding can begin, problems with the DIS instrument block
and the Guider filter wheel must be resolved.

I haven't finished analyzing the logged data yet; I should have more after
that is done.  It will be posted at
where all the other current information I have is stored.


Eric Deutsch                             email:
Department of Astronomy                                Voice: (206) 616-2788
University of Washington                                 FAX: (206) 685-0403
Box 351580                      WWW:
Seattle, WA  98195-1580                  Physics/Astronomy Bldg., Room B356F
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