Serial Numbers

Serial numbers for the Standard Questar, Field Model, Duplex, and Questar Seven all contain sequential production numbers beginning with the first units the company produced. The sequencing of those production numbers for the Standard and Duplex Questars began at 50, the early version of the Field Model at 1, the modern Field Model at 101, and the Questar Seven at 51.^[1]

The leading number in serial numbers for both Standard Questars (except the earliest examples) and Duplex Questars also indicate the last digit of the year in which a unit was built. For instance, Questar #2-1267 was produced in 1962. And since production numbers for Standard Questars began at 50, #2-1267 was the 1,218th example off the production line. Field Model serial numbers are typically made up only of an “F-” followed by a sequential production number. Serial numbers for Questar Seven units most often indicate a letter representing mirror substrate (“P” for “Pyrex,” for example), the digit “7,” and a production number. Neither Field Models nor Questar Sevens have any indication of manufacture year indicated in their serial numbers.^[2]

The company also included indications of other features in serial numbers. For more information, see “Questar Serial Number Systems” on the company’s website.

Using data from two spreadsheets (“Questar Information Database” and “Questar by Year,”^[3] both now available on the Questar Users Group on Groups.io), sales listings, and other sources, I have compiled the following tables which indicate the median production number of known serial numbers for any given year. To determine the year of manufacture for a Questar telescope, locate the production number in the table that is in the vicinity of that for the telescope on hand. For the decade and specific year in which that example was built, refer to the row and column headers.

Standard and Duplex Questar

Field Model

Questar Seven

Please note that there are holes in the data available to me. Where there is no production number for a given year, I derive it by doing math using the production numbers before and after the year without a number. Derived values appear in grey and are approximate.

Production numbers do not always follow in perfect sequence from one year to the next. One sometimes finds a Questar built at the end of a certain year that has a production number greater than other production numbers whose serial numbers indicate those other examples were built the following year. For instance, the “Questar Information Database” on the Questar Users Group (formerly on Yahoo Groups and now on Groups.io) lists Standard Questar #4-5877-BB, an instrument with broadband coatings that was built toward the end of 1974, and #5-5858, which was built with standard coatings around the beginning of 1975 but serialed with an earlier production number.^[4]

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Notes

¹ Jim Perkins, email message to author, August 26, 2020; Questar Corporation, “Questar Serial Number Systems,” n.d., https://www.questarcorporation.com/start.htm, accessed January 21, 2021.

² Questar Corporation, “Questar Serial Number Systems,” n.d., https://www.questarcorporation.com/start.htm, accessed January 21, 2021.

³ “Q_Inventory_083115b.xls” (unpublished manuscript, August 31, 2015), spreadsheet, https://groups.yahoo.com/neo/groups/Questar/files/Questar%20Information%20Database/, accessed October 15, 2019; Ralph Foss, “Questar by year.xls” (unpublished manuscript, February 7, 2014), spreadsheet, https://groups.yahoo.com/neo/groups/Questar/files/Questar%20Historical%20Prices%20and%20more/, accessed October 15, 2019.

⁴ “Q_Inventory_083115b.xls” (unpublished manuscript, August 31, 2015), spreadsheet, https://groups.yahoo.com/neo/groups/Questar/files/Questar%20Information%20Database/, accessed October 15, 2019.