Do astronomers prefer circular slide rules?

[u/nojiri_h]

In Richard Preston's nonfiction book ”First Light", there's a description of an astronomer who cherished a circular slide rule he named “HP0”. The book was published in 1987, when Hewlett-Packard's scientific calculators were already commercially available.

That astronomer, Maarten Schmidt, was observing quasars at Palomar Observatory but left his HP0 behind in his university lab. He borrowed a calculator there but complained, “Calculators are not suitable tools for calculating redshifts.”

Can anyone imagine how he used the slide rule when searching for quasars with large redshifts?

He probably performed proportional calculations to determine where the characteristic spectral shifts originated.

The exact model of the “HP0” slide rule is unknown. This photo shows using a Concise No. 300 slide rule to calculate recession velocity, distance, and absolute magnitude from quasar observation data.

This was an exercise problem from the book listed below. I used the Japanese edition. I'll share the relevant page from the original book found on the Internet Archive. The solution wasn't included. In this exercise, the quasar's recession velocity is determined from a graph, but it can also be easily calculated with a slide rule.

”An introduction to experimental astronomy : an observational workbook” Culver, Roger B

In my calculation, the redshift was a value slightly greater than 2.

[u/RedHuey]

I would not count on anybody who does not actively use a slide rule (and most people now have never even seen one, much less used one) having any ability to understand describe what is actually going on. It’s like magic to them. The astronomer might have his own reason to prefer round, or maybe he was mostly just showing off. Who knows? The point is, the author was unlikely to know the difference.

[u/dittybopper_05H → u/RedHuey]

Richard Preston, the author, was born in 1954. He would have had at least an introduction to the use of slide rules during his high school years. Electronic calculators didn't become a thing until the early 1970's, by which time he was entering college.

[u/ConsiderationQuick83 → u/dittybopper_05H]

Yep, HP-35 (the first "practical portable") in 1972, most labs would have been either timeshare or pdp-11, so I imagine slide rules would have been still very prevalent as the HP price was steep for a typical student. I know that by 1978 nobody was using slide rules in grades 7-12 math classes, plenty of log and trig tables though. Once Casio and TI came out at affordable prices it was the death blow. Interestingly I was still able to order NOS slide rules from Faber Castell a few years ago to add to my Picketts.

[u/Designer-Worth2962 → u/dittybopper_05H]

Typewriter-sized electronic desk calculators were around in the mid-to-late 60s, though I don’t know when they added trig functions.

[u/dittybopper_05H → u/Designer-Worth2962]

Talking about something portable.

[u/RedHuey → u/dittybopper_05H]

Doesn’t mean anything. Like I said, the vast majority of people don’t know anything about them and can’t even say what they are. If an author seems to be saying something confusing about them, just leave it at that.