LRS2 Position Angle and Fiber Layout
The LRS2-B and LRS2-R are located 100" from each other in the direction 90 degrees from the altitude line at center of track. The short axis of the 12"x6" LRS2 IFU are in the direction of the paralactic angle at center of track.
It is not possible at this time to specify an offset angle.
You can use the lrs2rho cgi script to determine the altitude line and the current parallactic angle and thus the angle of the LRS2 IFU on the sky.
You can find more about the parallactic angle and how it is related to the DEC and optimal Az by looking at the HET Object Observability pages.
The World Coordinate System (WCS) has generally been determined although we continue to improve this. Please see the WCS page. for information on the WCS for the HET and see LRS2 fiber layout page for information about how to place the LRS2 foot print (using ds9 regions files) onto the acquisition setup images.
The image below show the layout of the LRS2 fiber bundles among the VIRUS units above the corrector.
To help the PI understand our setups and also to understand the results they get from the LRS2 we have provided time stamped regions files which can be used along with setup images (called ACM image) to view the position of the IFU. The the example image below we have displayed both the LRS2-R (in red) and LRS2-B (in blue) region files on a ACM setup image from an observation of a bright star in LRS2-R.
Each time that the ACM or the IHMP are moved the relationship between the LRS2 IFU and the ACM position moves. The following table contains the regions files and the date in which those were installed or valid.-regions
These regions files can be loaded into ds9 under the "Region" pull down menu and selecting "Load Regions..." or on the command line with -regions
Last updated: Sat, 13 Apr 2019 21:51:08 -0500 stevenj