Subject: Recent changes to Drift Scan Camera Operations


Submitted: Mon, 5 Feb 1996 15:16:34 -0700

Message number: 19 (previous: 18, next: 20 up: Index)

Karen Gloria wrote the following in last night's observing log, and it
seemed appropriate to post it to this wider distribution:


I'm including some detailed notes on the DSC here because this
information is important to anyone planning to use it.

The DSC:
I acquired a new instrument block and tested the new TCC and MC
drift-scanning code.

The orientation of the DSC chip is EAST on the RIGHT, NORTH on the
BOTTOM (on the SCROLLING DISPLAY).  The orientation is north on the
top, east on the right in IRAF displays (ximtool, saoimage).

TCC instrument offsets: A +X offset moves the star to the RIGHT.  A +Y
offset moves the star to the BOTTOM (on the SCROLLING DISPLAY).  When
the object rotation is 0, a +X offset will move the TELESCOPE WEST
(star moves toward the east side of the display).  A +Y inst offset
will move the TELESCOPE SOUTH (star moves toward the north side of the

REMARK instrument offsets:  A +X instrument offset issued through the
Remark interface moves the star to the LEFT (the TELESCOPE moves EAST
if the object rotation is 0).  A +Y offset moves the star to the
TOP (the TELESCOPE moves NORTH if the object rotation is 0).

Rotation:  A + rotation issued through the TCC will rotate the FIELD
CLOCKWISE on the scrolling display (counter-clockwise on an IRAF

Drift-scanning:  To drift scan, issue an offset of 0,-y  (i.e. drift
northward).  I tested Russ Owen's new TCC driftscanning commands.
They work just fine.  These TCC commands are:

TRACK/SCANVELOCITY=(VX,VY)  The velocities are in units of degrees/sec
and should correspond to the fractions of siderial rate that the
camera uses (i.e. 0.0016667 deg/sec for 0.4 siderial rate).  This
command will drift along a great circle.

OFFSET ARC=N (where N is a value in units of degrees).  If you want ot
drift along a small circle, issue this command before the
track/scanvelocity command.  It will offset the telescope onto a small
circle parallel to the great circle it would have drifted on (this is
hard to describe without a diagram).

I tested both of these commands and the drift scans came out very good
- all round star images.

I also tested Brian Yanny's new MC drift-scanning commands.  These
also worked fine.  They are:

offset vx vy drift   (vx and vy are in units of DEGREES/HOUR)  If you
want to drift scan at 0.4 siderial rate, for example, use:

offset 0 -6.0 drift   (6.0 = 0.4 siderial in degrees/hr)

offset 0 0 drift   stops the drift

I tested this and the drift scans came out just fine.

DSC operation:

I ran into a few small problems with this-

the commands displayLast and getLast don't work (this is mentioned in
the documentation.)  I wasn't able to get an saoimage window open on

If you get error messages about the murmur server not running when you
start up, exit to the unix prompt and type
ps -ef | grep mur
to see if the two murmur processes are running.  If they aren't, type
dscRun start_mursrvr  (then type dscRun)  - This is ommited from the
current version of the documentation.

The runAutoFocusSequence command doesn't write the frame to your data
area, so after it finishes type:

saveFiles group start finish directory   (insert your group name, the
sequence # of the first frame you want, the sequence # of the
last frame you want, your data directory path)

The killCameraShell command doesn't work.  To kill the control shell
when you are done, use:


then type quit (or exit).

The error "timing active" cropped up a few times, preventing me from
taking any exposures.  Reseting the VME crate clears the problem.

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