UPDATE: The LMI User Manual has been updated. (2020Dec20) UPDATE: The 2021A LDT schedule has been released. (2020Dec01) UPDATE: The DeVeny spectrograph is back in operation. (2020Nov06) UPDATE: NIHTS is again available for use. (2020Oct08) UPDATE: The GG495 blocking filter has been replaced in the DeVeny spectrograph. (2020Oct02)
An updated version of the NIHTS User Manual (v1.4 - 2019013) has been released and is available on the LDT Observer Information confluence page. Per the authors, NIHTS User Manual v1.4 adds a description of blind target acquisition using LMI. |
We have looked into quantifying the delay between when a user requests an image with LMI, and when the shutter actually opens. Details can be found in the write up under the LMI link about the shutter delay. The bottom line is that: The exposure times are as recorded to within a few hundredths of a second, based on the star streaks. The shutter throw time in each direction is between roughly 0.1 and 0.2 seconds, meaning that there is also a temporal gradient across all the images. Formal uncertainty on the measured time offsets are an underestimate of the true variation. The shutter throw time alone means the mid-time varies across the frame systematically by at least 0.1second (added as the systematic uncertainty below). The shutter opens 2.05 +/- 0.06 (ran) +/- 0.1 (sys) seconds later than the UTCSTART in the image header. The shutter closes 0.19 +/- 0.06 (ran) +/- 0.1 (sys) seconds earlier than the UTCEND in the image header.
Exposure times should be computed as: Start time = UTCSTART + 2.05sec End time = UTCEND - 0.19sec Mid-time = UTCSTART + 2.05 + EXPTIME/2 or Mid-time = [(UTCSTART + 2.05) + (UTCEND-0.19)] / 2
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The DeVeny Spectrograph Reference and Operations Guide has been updated for the new release of the slitviewing camera GUI application. Version v1.5 (10 July 2018) of the manual is now available on the LDT Observer Information confluence page. |
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