Investigation of the William A. Rhodes i6-in. Gregarian Reflector at
Phoenix, Arizona on 13 July I960
1. Telescope
The primary mirror, figured by J. W. Pecker, la reported (by Pecker) to have
a 1/20 wave paraboloidal surface. The focal length is 51 laches. The ellipsoidal
secondary 4s placed approximately 17 inches behind the prime focus and returns
the beam to a secondary focus three inches in back of the primary mirror. The
amplification ratio is about A.9 yielding aa effective focal length of 259 inches,
or an effective focal ratio ef f 16. The secondary mirror is approximately one-
third of the diameter of the primary and the obstructing cell would be somewhat larger.
2. Xaspection
Jupiter and Saturn were observed at an hour angle of about 2-3 hours beat.
The seeing ranged from 2 to possibly 5 with an average of about 2 or 3.
The mount is highly prone to vibratlea, especially ia declination, and large
amplitude oscillations can be set up by merely tapping the eyepiece with a finger.
The difficulty probably is a result of a poor method used in providing for a
declination Clamp. The vibration problem appears sufficiently severe to prevent
direct image photography with a focal plane shutter.
The motor used ia the right ascension drive does not have synchronous control.
Rate is established by a Variac. The first reduction of angular rate from the
motor is provided by a two-gear chain drive. The final reduction is provided by
a wire of adjustable tension that passes around a cylinder, connected to the last
gear, to a wheel of 72-inch radias Centered on the polar axis. The drive suffers
considerably from backlash and appears to be undarpowered, especially so If
additional equipment were to be attached.
Telescopes; Telescopes and optics--Design and construction; Mirrors; Jupiter (Planet); Saturn (Planet); Scientific apparatus and instruments
Relevant Names
J. W. Fecker (Firm)
Digital Publisher
New Mexico State University Library
Collection
NMSU Department of Astronomy: Clyde W. Tombaugh Papers
Digital Identifier
Ms0407pp104021_0010001.tif
Source
Scan produced from physical item held by the NMSU Library Archives & Special Collections Department
Type
Text
Format
image/tiff
Language
eng
OCR
Investigation of the William A. Rhodes i6-in. Gregarian Reflector at
Phoenix, Arizona on 13 July I960
1. Telescope
The primary mirror, figured by J. W. Pecker, la reported (by Pecker) to have
a 1/20 wave paraboloidal surface. The focal length is 51 laches. The ellipsoidal
secondary 4s placed approximately 17 inches behind the prime focus and returns
the beam to a secondary focus three inches in back of the primary mirror. The
amplification ratio is about A.9 yielding aa effective focal length of 259 inches,
or an effective focal ratio ef f 16. The secondary mirror is approximately one-
third of the diameter of the primary and the obstructing cell would be somewhat larger.
2. Xaspection
Jupiter and Saturn were observed at an hour angle of about 2-3 hours beat.
The seeing ranged from 2 to possibly 5 with an average of about 2 or 3.
The mount is highly prone to vibratlea, especially ia declination, and large
amplitude oscillations can be set up by merely tapping the eyepiece with a finger.
The difficulty probably is a result of a poor method used in providing for a
declination Clamp. The vibration problem appears sufficiently severe to prevent
direct image photography with a focal plane shutter.
The motor used ia the right ascension drive does not have synchronous control.
Rate is established by a Variac. The first reduction of angular rate from the
motor is provided by a two-gear chain drive. The final reduction is provided by
a wire of adjustable tension that passes around a cylinder, connected to the last
gear, to a wheel of 72-inch radias Centered on the polar axis. The drive suffers
considerably from backlash and appears to be undarpowered, especially so If
additional equipment were to be attached.
