TUB Rotation
The telescope utilization bin (TUB) at the bottom of the 3-m telescope can be rotated. Any instrument mounted at the Cassegrain focus will rotate with the TUB. This is useful for rotating the instrument to a desired position angle on the sky (e.g. aligning the slit of a spectrometer with the mean atmospheric dispersion). Due to mounting contraints of individual instruments, the TUB may not always be able to rotate. Currently the only instrument for which TUB rotation is allowed is the Kast Spectrograph. 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. The program NixiPA assists observers with converting the nixie display into a position angle.NixiePA
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NixiPA is a program that converts the nixie tube readout to a position
angle in degrees East of North, and vice versa.
NixiPA is started from the user account on either gorgon 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. Please note that NixiPA assumes that a 90 degree position angle corresponds with 78.44 nixie readout (this is true for the Kast Spectrograph). If a user supplies their own instrument, there may be an offset. Luckily, the relation between the nixie readout and angle is linear, so once the offset is determined, rotating to the desired position angle should be academic. |
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NixiPA User Interface |
Last modified: Thu Jan 24 10:52:06 PST 2008