Differences

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--- on_sky_testing [2025/11/06 19:37] – holtz
+++ on_sky_testing [2025/11/21 15:46] (current) – holtz
@@ Line 1: / Line 1: @@
+====November 2025====
+Enclosure box installed 11/18-29. Required taking ferrule out to run through box, so location of traces, etc. changed. Installed 4 temperature sensors inside the box. Cleaned up room and put spare parts on shelf and in drawers.  Installed pass-thrus for cables on FPUs. Connected big dome fan to outlet #10.
+Spectrograph refocussed.
 ====Guiding tests====
@@ Line 15: / Line 21: @@
 {{:test:throughput.png?direct&400}}
-Clearly, there is some variation in the throughput, which is expected because of variations in transparency and also variations in seeing, leading to different fiber losses at the focal plane. However, the exposures with iodine are clearly significantly lower than those without iodine by a factor of roughly 2-3 (we've been using 2.5x the exposure time for iodine, and you can see in the middle panel that this roughly brings observed fluxes to be the same); i.e., iodine throughput is  ~40% of the non-iodine throughput.
+Clearly, there is some variation in the throughput, which is expected because of variations in transparency and also variations in seeing, leading to different fiber losses at the focal plane. However, the exposures with iodine (+ symbols) are clearly significantly lower than those without iodine (squares) by a factor of roughly 2-3 (we've been using 2.5x the exposure time for iodine, and you can see in the middle panel that this roughly brings observed fluxes to be the same); i.e., iodine throughput is  ~40% of the non-iodine throughput.
+The horizontal lines represent throughput achieved at the Tenerife SONG node for several different stars (median of many observations), I believe through iodinec cell, from some paper....
 ===Stellar profiles with and without iodine===
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 ===Image quality with iodine cell===
-The following image shows a focus sweep of a star with the iodine cell in place. Compared with similar images without the iodine cell, the core is blurrier, but there is also some very asymmetrical light outside of the core of the image.
+The following images shows a focus sweep of a star with the iodine cell in place (at two contrasts). Compared with similar images without the iodine cell, the core is blurrier, but there is also some very asymmetrical light outside of the core of the image.
-{{:test:iodine.png?direct&400}}
+{{:test:iodinerun.png?direct&400}}
+{{:test:iodinerun_contrast.png?direct&400}}
-The following images show coarse focus run with and without iodine cell in place.
+The following images show coarse focus run with and without iodine cell in place. Aberration is clearly present with the iodine cell.
 {{:test:iodine_coarse.png?direct&400}}
@@ Line 46: / Line 55: @@
 To look at the overall throughput of the iodine cell in a different way, we looked at flat fields taken with and without the iodine cell. The ratio of these is shown in the following plot.
-{{:test:flatratio.png?direct&400}}
+{{:test:iodineflat.png?direct&400}}
+This suggests an overall throughput of 75% or less, under the assumption that the same amount of calibration light is incident on the fiber; our calibration spot is 200 microns in size for a 50 micron hole, and we have adjusted the iodine cell so that the hole is in almost the same location when the cell is in place, but it is not exact, although we think it is close enough that roughly the same amount of flux should be going down the hole.
-This suggests an overall throughput of 75%
+Interestingly, the iodine data here was taken after the iodine cell heaters had been turned off for 12 hours, with the cell around 13 C, but iodine absorption is still present!