User's Guide to the Crossley Telescope


Table of Contents


Introduction
Dome
General
Ground Level
Mezzanine
Dome and Platform
Telescope
General
Balance
Head Rotation
Finder
Motions
Dec Tangent Arm
Position Indicators
Mirror Cover
Reversal
Dome Slit
Access Ports
RA Drive Preload
Operating Limits
New Telescope Drive

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The Telescope: Limits

  1. Zenith distance: < 75 degrees to avoid tipping mirror.
  2. Relative humidity: close the dome at 95% RH or earlier if necessary to exclude any and all moisture from the dome. In particular be alert for sudden and unexpected fog formation and do not leave the vicinity of the dome if it's open without being very alert for any sudden change in the weather. If you can see moisture in your flashlight beam, or if wooden surfaces and papers get wet; close!
  3. Wind: no explicit limit, but when leaves and twigs start blowing in perhaps you're pressing too hard. Usually before that happens, the tube will shake too much for reliable observations anyway.
  4. Airbourne Particles/Ash: Enclosures must be closed if airborne particles (e.g. ash from forest fires) are deemed a threat to the optics. A particle counter resides inside the Shane enclosure and measures particles 0.3 microns in size and 0.5 microns in size. The particle counter responds to outside changes, even when the enclosure is closed. The following threshold values (adopted 2013-08-05) apply (even when the Shane enclosure is closed):

    0.3 micron 0.5 micron
    Warning 12000 800
    Closure 17000 1000
    Particle counts must remain consistently below the closure thresholds for at least 30 minutes before (re-)opening enclosure can be considered.

    If in doubt, contact the Shane telescope operator (9-5952).