Yerkes 7-inch Schmidt (Series YS7)

The Telescope:
The Yerkes Observatory 7-inch f/4 Schmidt telescope was installed in the auxiliary south building on the Observatory campus about 1977 or perhaps earlier.  It had a measured clear aperture of 6.93-inch (17.6-cm).  The recorded focal length is 71.6 cm giving a scale of 288''/mm. The geographic location is: longitude = 88° 33’ 21'' W, latitude = 42° 34’ 10'' N.

The Plates
The logbook lists 186 plates taken with this telescope in the period 1976-1997.  The early plates are 2.25 x 2.25-inch (57 x 57-mm) in size, while most of the later ones are 2 x 2-inch (25 x 25 mm). The area of sky exposed on a plate is about 50 x 50-mm giving a field of view of 4 x 4 degrees. Plates S-172 to S-183 were taken by George Corso (GC) and his collaborators.  They were purchased by them and removed from the Yerkes archive for their use sometime in the 1990s (e-mail communication from Corso, February 2011).  The plate listing includes three plates taken in 1973 - 1974 that are in envelopes labeled "7-inch Schmidt" but are not in any logbook.

The Logbook
The plates are recorded in the 7-inch Schmidt logbook. While the plates are numbered consecutively, the first twenty-six taken in 1977 by Oravecz were denoted MO-1 to MO-26. Plates taken in 1981 or later were denoted as S-27 to S-186.  The logbook is at  
the University of Chicago.  It has been scanned and the scans are available on-line.

The Searchable files
There is a “7-inch-Schmidt.csv” file that can be viewed or downloaded to search for plates of interest.  The file lists the plates by plate number.  Any cell in the csv file that is blank indicates there is no information available or it has yet to be calculated (for example, a time of mid-exposure when the start time and end time are known).

Description of the columns of the csv file:
Rcd - Record number in this catalog
Series - Yerkes 7-inch Schmidt (YS7 assigned; MO or S numbers)
Plate No - Identifying number of the plate
Date - The date the plate was exposed as recorded.  Many dates are listed in double-day format
Object - The target field or object of the exposure 
RA - Right ascension of the plate center (most 1950 equinox, some 1975) 
Dec - Declination of the plate center (most 1950 equinox, some 1975) rounded to nearest minute
Exp (min) -  Exposure length (in minutes unless otherwise noted)
Start - Start time of the exposure (when recorded)
Mid - Mid-time of the exposure (if recorded or calculated)
End - End time of the exposure (when recorded)
Time type -  Type of time used (usually UT)
Plate type (emulsion)  - Emulsion type (Kodak)
Filter - Filter type (if any)
Plate size (inches) - Physical size of the plate (in inches)
Observer - Recorded observer (see list below)
Location - Location of plate when this catalogue was prepared: Yerkes = in Yerkes plate vault.  Blank indicates that plate not in vault but it is believed it was not discarded.
HA at end - Hour angle at end of exposure (can be used to determine time of exposure)
Notes - Notes recorded in the log book. 

Observers:  
JWB = John W. Briggs 
ARC = Arnab Rai Chaudhuri 
GC = George Corso (and collaborators)  
KC = Kyle Cudworth 
AJ = Andy Jankovics
SM = Steven Majewski
MO = Mike Oravecz 
DP = Daniel Petersen  
JS = John Smetanka 
CMT = Charlie Telesco

File updated:   2024 September 17 (AF)