Yerkes 24-inch README

The Telescope:
The Yerkes Observatory 24-inch reflector telescope was installed designed and 
manufactured at that observatory and installed in 1901.  Although it has a clear 
aperture of 23.5-inches (60-cm), it was originally named the “two-foot reflector” 
which later became the “24-inch telescope.”  The telescope has an effective focal 
length of 93-inch (235-cm), giving a scale of 87"/mm.  The geographical location 
was:  longitude = 88° 33’ W, latitude = 42° 34’ N.  The telescope is described by 
Ritchey in Astrophys. J., 14, 217, 1901.

The Plates
Over 25,000 direct plates were taken with the Yerkes 24-inch reflector from its 
installation in 1901 to its decommissioning in 1969.  There are several series of 
plate numbers.  The Ry series has about 80 plates taken by G. Ritchey 1901 - 1904 
and numbered Ry-1 to Ry-69.  The R series has about 5830 plates taken by various 
observers (including Hubble) 1901 - 1952 and numbered R-1 to R-5828; some are 
objective prism or objective grating plates.  The van Biesbroeck [vB] series has 
about about 11,500 plates taken 1922 - 1963 taken mainly by G. van Biesbroeck; 
these plates are not yet cataloged. Also not cataloged is a short series of plates 
of Messier objects taken in 1957.

The Plates
Plates are 3¼ x 4¼-inch in size.  Ritchey’s early description of the telescope  
mentions 8 x 10-inch plates but none have been located.    

The Logbooks
There are four log books that cover the initial part of the plate collection. 
Book 1 contains plates 1 (1901-07-23) through 1951 (1907-08-20). Book 2 contains 
plates 1952 (1907-08-20) through 3519 (1916-12-13).  Book 3 contains plates 3520 
(1916-12-14) through 4631 (1923-05-23). Book 4 contains plates 4631a (1923-05-23) 
through 5829 (1952-02-25).  The four log books are at the University of Chicago.  
They have been scanned and the scans are available on-line. 

The Searchable files
There are two csv files that can be viewed or downloaded to search for plates 
of interest.  The “Full.csv” file gives list the plates by plate number. The 
“By-Dec.csv” file is the Full file sorted by decreasing declination which allows 
a quicker way to see if the collection contains plates of interest.  An Additional-
Notes.csv file provides any detailed notes on a plates from the log books not 
included in the Full.csv file. Any cell that is blank indicates there is no 
information available or it has yet to be calculated (for example, time of mid-
exposure when start and end times are known)  
   
Description of the columns of the csv files
Record number - Record number in the catalog
Plate series - Yerkes 24-inch Ry series (first) and R series
Plate number - number in the series
Date - The date the plate was exposed as recorded. Some listed in double-day format. 
Object - The target field or object of the exposure. Some plates have multiple fields
RA - Right ascension of the plate center 
Dec - Declination of the plate center 
Length of exposure -  Exposure length (in minutes unless otherwise noted)
Exposure Start - Start of the exposure as recorded 
Exposure Mid - Mid-time of the exposure (if recorded or calculated)
Exposure End - End of the exposure (when recorded)
Time type -  Type of time uses (usually CST)
Emulsion + Filter - Emulsion type and filter used (if any)
Plate dimensions - physical size of the plates, in inches
Observer - Recorded observer (see list below)
Location -  Location of plate when this catalog was prepared: Yerkes plate vault or 
     University of Chicago 
Notes - Notes recorded in the log book.  Longer notes are in the Additional-Notes 
     file

Observer list (not all codes are identified. Not all are entered in csv file)  
J.A., Bigelow, Bidelman, O.C. Collins, A. Farnsworth = F?, Garrett, Gingrich, 
Greenstein = FCG? = G?, Gushee = VMG = G, Harris, Hendrich, Hubble, F.C. Jordan, 
A. H. Joy = AHJ, Justin ? = J?, Keenan, Kragdahl, Lee, Thorton Page = TLP, 
Parkhurst = Park = P, Parsons = Ps?, Pettit = Pwt = Pt, Pv, F. Ross, Seyfert, 
Sharpless, Slocum = Slo, Struve = Sigma, H. T. Stetson = HTS, van Biesbroeck = vB, 
H.R. Vanderlinden = vL, A. van Maanen, Truman,, Wickham, EW, Williamson, 
Yamamoto = Yam = Ya = Y 
 
Created:  2022 October 12