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The Fox News article Arizona city played critical role in moon exploration history covers several interesting activities that took place in Arizona in preparation for the Apollo Moon landings.

It shows the telescope (shown below) and mentions that it was used to draw lunar maps.

There is more information about this telescope here and here as mentioned in this answer.

Question: Why does this Lowell Observatory telescope have so many knobs? What do they all do? Is it possible to identify the function of all of the annotated controls and devices on this complicated-looking telescope?

I've added some numbers to facilitate discussion. There is also a chain going between the locations of #4 and #5, though I don't know exactly what it couples.

click images for full size viewing

a Lowell Observatory telescope, annotated

above: Lowell Observatory telescope used by scientists who collaborated with artists to map out the moon for Apollo astronauts (Fox News) Source

below: Screenshot from July 9, 2019 Fox News video NASA lunar legacy in the Arizona desert

a Lowell Observatory telescope

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Here is part of a drawing from the Lowell Observatory booklet "100 Years of Good Seeing: The History of the 24-Inch Clark Telescope" (22 MB (i.e. large file warning) PDF):

Lower half of 24-inch refractor

Dial 6 is the right ascension clock. Without closely watching observatory staff operate the telescope, the rest is speculation:

Being near dial 6 and linked by chains, knobs 4, 5, and 7 are probably for adjustments in right ascension. Knob 5 could be a clutch to disengage for slewing and engage for sidereal tracking.

One of knobs 1-3 is for an iris near the objective, to limit chromatic aberration by reducing the aperture. The other two knobs are probably for adjustments in declination; again one may be a clutch.

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I contacted Dr. Danielle Adams, Deputy Director for Marketing and Communications at the Lowell Observatory. She was kind enough to reply, and generously provided the following (lightly edited for formatting):

I spoke with one of our senior educators about the Clark knobs. The numbers below correspond to the numbers in the image posted in Why does this Lowell Observatory telescope have so many knobs? What do they all do?

  1. Slow motion control for adjusting Right Ascension (east-west movements) while the Right Ascension clutch (3) is locked down.
  2. Iris control that allows us to control the effective aperture of the telescope. There is an adjustable aperture that can be adjusted from 24" (wide open) to 6".
  3. Right Ascension clutch that when tightened prevents the telescope from being moved by pushing, allowing the telescope drive to operate.
  4. and 7. Slow motion controls for adjusting declination (north-south movements) while the Declination clutch (5) is locked down. The two controls are linked with bicycle chain so when one moves, so does the other. This allows operation of the control from either side of the viewing position.
  5. Declination clutch that when tightened prevents the telescope from being moved by pushing, allowing the telescope drive to operate.
  6. Sidereal clock that permits astronomers to point their telescopes to a given celestial object more easily.The sidereal day is about 4 minutes shorter than the 24 hour solar day. This is due to the fact that the Earth revolves around the Sun while it rotates about its axis.
  7. see (4)

enter image description here

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