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'Alopeke & Zorro Overheads

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Each target must include an acquisition, and every group of speckle targets within 15 degrees and/or every hour must include a point source standard. A photometric standard must be included once/night when doing photometry.

Acquisition overheads associated with setting up on each new target include time for slewing the telescope, configuring the guiding, and centering the target. These sum to ~5 minutes for targets with V<12 and ~6 minutes for targets with V>12.

Point source standards (bright stars known to be single) will be observed at each sky location with a minimum of one per hour. These take ~10 minutes (including acquisition overheads) and must be included in time requests. Groups of science targets closer than ~15 degrees may share point source standards.

Programs wishing to do photometry must include 10 minutes (including acquisition overheads) per night per photometric calibrator (wide binaries).

Filter changes add ~1 minute of overhead.

Observation Overheads
Action Overhead (min)
Acquisition (V<12) 5
Acquisition (V>12) 6
Point Source Standard 10
Photometric Standard 10

Readout and file-write overheads are 6-8% when using the 256 or 512 ROI in speckle mode, and a single set of 60ms x 1000 images (1 minute of open-shutter) will take 64-65 seconds to complete.

Speckle Readout Overheads
ROI Integration Overhead Total Time
256 x 256 1000 x 60ms 6% 64s
512 x 512 8% 65s

Wide-field (full-frame) overheads depend on how many images are saved in each FITS file. Saving 100 full-frame images per file incurs an overhead of ~0.03s / image and saving 500 full-frame images per file (the maximum for full-frame, producing a 1GB file) incurs an overhead of ~0.02s / image.

Gemini Observatory Participants