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--- dithered_exposures [2019/07/29 15:43]
davner removed
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-The note below is kindly provided by Christopher Willmer.
-Prime allows obtaining dithered exposures through scripts, which is
-absolutely critical in the case of exposures in R, I, SDSS r, i and z
-(e.g. Cool, 2007, ApJS, 169,21) where fringing is a problem.
-As an example, R. Cool combined from 12 to 42 z band exposures obtained
-during the course of each night to create a "fringing" correction master.
-By scripting much of the book-keeping is reduced.
-In the case described here, a series of "N" dithers, each separated by 60"
-is calculated using a circular pattern. The total amplitude in Ra and Dec is
-arc minutes, about 10% of the areal coverage of a single 90Prime CCD
-(area 23 arc min x 23 arc min).
-) The observing scripts were generated using a Fortran programme (dither.f),
-for which a central coordinate, image type, object name and list of filters
-are given. In the code I use 10 dithers for SDSS u and g and 20
-for SDSS r, i and z. The programme generates an output file
-"pg_z_dither_script" which is then
-fed into a perl script (dither_to_dos.pl) that will translate the
-LINUX/UNIX carriage return control into DOS carriage return + linefeed.
-For each file is does:
-perl -p -e 's/\n/\r\n/' < unixfile.txt > winfile.txt
-) The scripts then need to arrive at the 90prime bokccd computer somehow.
-I copied the files to bok:
-scp *scr*txt primefocus@bok.as.arizona.edu:/data/primefocus/cnaw/
-and then on bokccd fired cygwin and
-scp primefocus@bok.as.arizona.edu:/data/primefocus/cnaw/\*scr\*txt .
-(not the most straightforward way but works, a USB port is also available)
-These must then be copied using windows into directory:
-c:\AzCam\System\90Prime\ObservingScripts
-The final scripts MUST have the .txt suffix, otherwise the windows machine
-will not understand the file.
-) Running the script
-When the script is run, the telescope is moved to the new position and
-it will wait until the "moving" flag from the telescope is turned off, and
-waits for an additional 0.1 sec to start the integration (M. Lesser, private
-Communication, 2012-01-15).
-To carry out dithered exposures with 90 Prime one uses on AzCam the command
-Run Observe scriptname #_of_times
-where #_of_times will be the number of times this script should be run.
-This is what a line in a script looks like:
-obs 150.0 object 'T2900' 1 u 090348.00 +173427.0 2000.0
-obs - is the script command
-- exposure time
-object - image type (OBJECT, ZERO, FLAT)
-'T2900' - object name; quotes REQUIRED !!
-- number of exposures at this position
-u - filter
-.00 - RA (HMS) with _ONLY_ two decimal digits!!
-+173427.0 - DEC (DMS) with 1 decimal digit precision
-.0 - EPOCH

MOON

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