A slew or dither pattern file can be used to slew the telescope between targets, dither, change exposure times, change filters & the number of exposures. If a user wishes to simply cycle through a series of filters (without moving the telescope), the input file can be very brief and only include exposure time and filter names. Not all exposure options are allowed in the pattern file, so it is recommended that the user takes one test image with the desired parameters such as binning factor so these values are cached and will be used while the pattern is running.
These pattern files need to be on the observer machines ( dct-obs1
/ dct-obs2
) because they will be input into the LOUI. All of the caveats for creating Observer Target Lists apply here, such as using a basic text editor (e.g., vi or emacs) and avoiding extended character sets. You may transfer your pattern files to the observer machines via USB drive or scp
, as desired, or even create them directly on the observer machine during the observing session.
Format
Slew-dither pattern files must begin with a metadata line (starting with a #) indicating which fields are present in the file. Options include:
The format to follow is below starting with the metadata at the beginning of the document. This particular example is a dither pattern. More info can be found on the Automated Functions page. Appropriate string names for the filters are listed in LMI Filter Information.
#title=false ra=false dec=false exposureTime=true numExposures=true filter=true muRA=false muDec=false epoch=false dRA=false dDec=false rotatorPA=false rotatorFrame=false xi=true eta=true comment=true # 60.0 1 SL-g 0.0 0.0 "Centered SDSSg" 120.0 1 SL-r 0.0 0.0 "Centered SDSSr" 120.0 1 SL-i 0.0 0.0 "Centered SDSSi" 60.0 1 SL-g 15.0 30.0 "dXi,Eta = 15,30 SDSSg" 120.0 1 SL-r 15.0 30.0 "dXi,Eta = 15,30 SDSSr" 120.0 1 SL-i 15.0 30.0 "dXi,Eta = 15,30 SDSSi" 60.0 1 SL-g 33.0 -5.0 "dXi,Eta = 33,-5 SDSSg" 120.0 1 SL-r 33.0 -5.0 "dXi,Eta = 33,-5 SDSSr" 120.0 1 SL-i 33.0 -5.0 "dXi,Eta = 33,-5 SDSSi" 60.0 1 SL-g 0.0 0.0 "Centered SDSSg" 120.0 1 SL-r 0.0 0.0 "Centered SDSSr" 120.0 1 SL-i 0.0 0.0 "Centered SDSSi" 60.0 1 SL-g -30.0 15.0 "dXi,Eta = -30,15 SDSSg" 120.0 1 SL-r -30.0 15.0 "dXi,Eta = -30,15 SDSSr" 120.0 1 SL-i -30.0 15.0 "dXi,Eta = -30,15 SDSSi" 60.0 1 SL-g -5.0 -33.0 "dXi,Eta = -5,-33 SDSSg" 120.0 1 SL-r -5.0 -33.0 "dXi,Eta = -5,-33 SDSSr" 120.0 1 SL-i -5.0 -33.0 "dXi,Eta = -5,-33 SDSSi" 60.0 1 SL-g 0.0 0.0 "Centered SDSSg" 120.0 1 SL-r 0.0 0.0 "Centered SDSSr" 120.0 1 SL-i 0.0 0.0 "Centered SDSSi" |
It may be helpful to end dither scripts with a (0,0) (xi,eta) offset. Otherwise, the last offset values will stay in and alter the pointing of the telescope until explicitly cleared. |