2MASS North Focus Test Results for 980916 UT

One set of one-degree-long focus scans were obtained on the night of 980916 UT at the 2MASS North facility at Mt. Hopkins. This test was the fourth of several iterative tests to recheck telescope focus and collimation at the start of post-summer shutdown.

One focus runs (Run 9) was obtained in a similar fashion to those obtained on 980914n and 980915n (Runs 1-8):

Run 9 (scans 001-007) -- Secondary adjusted to be 8mm east (?) and 1mm south (?) of position at start of 980914n. Seven scans taken at focus settings of +2115 to +2415 microns in steps of 50 microns.

The raw data for the focus test scans were processed during the 24hr QA/Tape validation processing at IPAC on 980916 (PDT) using 2MAPPS v2.0x. From what I can read into the log, there were some clouds around when these test scans were taken, and I'm not sure how good the seeing really was.

The composite psf images are shown in the figure below. The three rows show, respectively, the J, H and K_s images. Scan number is shown in each J image.

The table below lists the scan, focus setting, telescope and head ring temperatures reported in the parameter files for each scan. Also listed are the second image moment ratios(*rat), seeing shapes (*sh), and fractional encircled energy parameters (PFRAC) derived for each of the focus test scans.

scn focus Tel_T Rng_T Jrat Hrat Krat Jsh Hsh Ksh Jpfrc Hpfrc Kpfrc

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Run 9:

001 +2115 19.2 17.9 1.014 1.025 1.111 1.428 1.381 1.385 0.3170 0.2799 0.2694

002 +2165 19.2 17.9 1.010 1.030 1.157 1.305 1.281 1.259 0.4079 0.4117 0.4101

003 +2216 19.2 17.9 1.013 1.034 1.186 1.141 1.098 1.071 0.5392 0.5817 0.5987

004 +2267 19.1 17.8 1.007 1.029 1.084 1.145 1.103 1.076 0.5055 0.5882 0.5988

005 +2315 19.1 17.9 0.993 1.002 0.969 1.200 1.147 1.113 0.4460 0.5296 0.5277

006 +2365 19.1 17.9 0.982 0.987 0.920 1.472 1.405 1.315 0.3022 0.3443 0.3645

007 +2416 19.1 17.8 0.908 0.947 0.816 1.510 1.440 1.375 0.2630 0.2778 0.3024

The figure below shows second image moment ratio, seeing shape, and PFRAC plotted as a function of focus setting for scans 001-007. J data are plotted in blue, H in green and K_s in red.

D. Kirkpatrick - IPAC

Last update - 16 September 1998