LRS2 Position Angle and Fiber Layout

The LRS2-B and LRS2-R IFU feeds are located 100" from each other in the direction 90 degrees from the altitude line at center of track. The short axes of the 12"x6" LRS2-B & LRS2-R IFUs are in the direction of the parallactic angle at center of track.

It is not possible at this time to specify an offset angle.

We have a script available to overlay the LRS2 IFU footprint on a PanSTARRS image for a given coordinate on the sky: https://github.com/sjanowiecki/HET_lrs2_finder.

Or you can use the older lrs2rho cgi script to determine the orientation of LRS2 on the sky for any coordinates. 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 below for the LRS2 fiber layout information.

The image below show the layout of the LRS2 fiber bundles among the VIRUS units at the HET focus.

  • Central part of the HET focal surface looking at the fiber feeds mounted in the input head mount plate (IHMP). A number of VIRUS IFUs are seen along with the feeds for LRS2-B and LRS2-R and the fiber feed for HPF. The BIB (boresight imaging bundle) is a small field imaging fiber bundle that defines a location on the IHMP so that the IHMP and the ACAM can be tied together and checked. The seat for the future HRS-2 feed is also indicated.

  • The LRS2 IFUs have 6” x 12” format oriented as shown

  • Parallactic angle (Tracker Y axis) is up in this figure, as indicated by the dark orange arrow; it is perpendicular to the long axis of the LRS2 IFUs

  • The orange square indicates the field of view of the acquisition camera (ACAM) which is fed by a pick-off mirror that can be deployed in front of the IHMP.

  • LRS2-B input head is mounted in IHMP slot 056 and the feed for LRS2-R in 066

To help the PI understand our setups and also to understand the results they get from the LRS2 we have provided (below) a list of X,Y pixel coordinates corresponding to the LRS2-B and LRS2-R IFU positions on the Acquisition Camera (ACQ or ACM or ACAM). These coordinates may be useful for the advanced user who wants to compare the ACQ camera setup images taken during the acquisition of their target.
Each time that the ACQ camera/mirror or the IHMP are moved the relationship between the LRS2 IFU positions and the ACQ camera changes slightly. The following table contains the X,Y coordinates and the dates of validity.

Date effective
As of 2 Nov 2023
735.96, 210.01
731.65, 578.92
As of 13 Aug 2022
734.97, 212.33
729.15, 581.53
As of 15 Mar 2022
740.6, 215.5
735.6, 584.6
As of 2 Nov 2020
740.81, 215.92
736.32, 584.43
As of 11 Jul 2019
738.6, 211.6
739.7, 577.3
As of 2 Apr 2019
737.7, 212.0
740.3, 577.5
As of 28 Sep 2018
735.5, 212.6
737.9, 581.7
As of 27 Jul 2018
731.6, 212.0
734.5, 582.0
As of 10 Dec 2017
735, 210
740, 577
As of 6 Oct 2017
741.8, 213.3
744.5, 581.5
As of 10 Aug 2017
734.7, 211.5
738.1, 580.2
As of 14 May 2017
728.0, 205.5
731.5, 574.0
As of 12 Apr 2017
729.4, 206.9
732.2, 576.6
As of 3 Mar 2017
723.8, 201.6
726.0, 571.6
As of 21 Oct 2016
723.8, 201.6
726.0, 571.6
As of 2 Apr 2016
709.7, 183.2
729.4, 550.4
As of 27 Feb 2016
723, 246
721, 612
As of 15 Jan 2016
732, 219
730, 585

Last updated: Fri, 29 Dec 2023 11:12:18 +0000 stevenj


The Telescope

Technical Overview

Object Observability


Non-sidereal observations



LRS2 Summary

LRS2 Details

LRS2 Fiber Layout and Position Angle

LRS2 Throughput

LRS2 Observing details


VIRUS - Summary

VIRUS - Setting up on targets

VIRUS - Misc details

VIRUS - Throughput and sensitivity

VIRUS - low surface brightness sensitivity

VIRUS - Dithers, IFUs, Tiling

VIRUS - Tiling observations

Habitable Zone Planet Finder (HPF)

HPF Details

HPF Setting up on targets

HPF Throughput and Exposure Meter

HPF Data Reductions

HRS-2 (in development)

HRS-2 Summary

HRS-2 Details

HRS-2 configurations

HRS-2 exposure meter

HRS-2 Position Angle and Fiber layout

HRS-2 Throughput

Old Instruments

HRS - old

LRS - old

MRS - old

Program Preparation

Web Management System