User's Guide to the Kast Double Spectrograph


Table of Contents


Introduction
Quick Reference
Hardware Overview
Common Path
Blue Side
Red Side
Detector Characteristics
Software
Kast Controller
Data Taking System
Position Angle
Arc and Flat-field Lamps
Diagonal Mirror
Kast Focus
Eventsounds
Telescope Offset
Setup and Observing Hints
Setup Procedures
Observing Hints
Calibration Lamp Spectra
Exposure Time Calculator

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Position Angle

The TUB can be rotated to position Kast's slit at any desired angle. A nixie tube display in the 3-m telescope control room is the most accurate display of the TUB rotation. However, the nixie tubes display a voltage reading of the encoder pot, rather than the position angle in degrees East of North. Two programs exist to assist observers in both calculating the mean angle of atmospheric dispersion and converting position angle into nixie values.

Please note that the NIXIE readout is no longer used, so NixiPA is no longer needed for the operation of Kast.

PA | NixiPA


PA

NOTE: Parallactic angle is now (as of Dec 2013) calculated within the Coords program. However, there may be instances when the PA program is still useful for calculating the parallactic angle. For more information, refer to the documentation for Coords.

PA is a program that calculates the mean atmospheric dispersion (parallactic angle) for a given exposure time and position of the telescope. PA is started from the user account on gouda, karnak, or shard computers by typing pa at an xterm prompt.

You will then be prompted for the following information:

Enter starting HA (hh.hh, hh:mm, or hh mm):
Enter starting Dec (dd.dd, dd:mm, or dd mm):
Length of Exposure (sec):

The average position angle and nixie readout will be displayed. This information can then be given to the Telescope Operator so that he/she can rotate the TUB to the proper position.

Example:

Enter starting HA (hh.hh, hh:mm, or  hh mm): 2:34
Enter starting Dec (dd.dd, dd:mm, or  dd mm): 15:37
Length of Exposure (sec): 1200

Starting HA = 2.57      Dec = 15.62     Time = 1200 seconds

PA (average) = 231 (or 51)      Airmass (average) = 1.35
Nixie readout = 201.0 (or 44.4)


NixiPA

NixiPA is a program that converts the nixie tube readout to a position angle in degrees East of North, and vice versa.

Please note that the NIXIE display is no longer used, so this software is no longer needed for the operation of Kast.

NixiPA is started from the user account on either gouda or karnak by typing nixipa.

To convert from position angle to nixie reading, enter the position angle and click "PA to NIXIE" or hit the Enter key. The corresponding nixie reading will be both displayed in the NIXIE Reading entry box and on the simulated nixie tubes.

To convert from nixie reading to position angle, enter the nixie reading in its entry box and click "NIXIE to PA" or hit the Enter key. The corresponding position angle (in degrees East of North) will be displayed in the Position Angle entry box.

Nixie readout limits to the rotation of the TUB are also displayed for reference.

The "Quit" button exits NixiPA.

NixiPA User Interface


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Last modified: Thu Dec 12 10:20:10 PST 2013