Tuesday 1 February 2022

Flamsteed Catalogue Anomalies


I use my Fuji XT2 camera to take short 5 second exposures of star fields well away from the galactic plane. I am looking for high latitude novae. I just can’t be bothered to go below magnitude 9.0, there are too many stars to check.

John Flamsteed 1646-1719 produced a catalogue of naked eye stars in the various constellations that were visible to him. I keep coming across anomalies with stars that have Flamsteed numbers (Fl). I sometimes come across stars that are much brighter than the stars around them yet they don’t have a Fl number, they are clearly visible to the naked eye, but were not recorded by Flamsteed. On the other hand there are some Fl stars that are below naked eye visibility yet still have a Fl number!

Either the stars have changed over the past 300 years or were misidentified by him, or his charts were changed by someone after his death. I run all the usual checks through various catalogues to see if there is any data on them. There usually isn’t. This is one example:-

In-between Fl 32 Uma and Fl 35 UMa is an unmarked star which is brighter than both of these stars.

 The star is actually now known as ET Uma, it is an alpha2 Canum Venaticorum type variable. These are magnetic variables whose amplitude is very tiny, usually no more than 0.1 of a magnitude. This is a white A class star. It is listed with a magnitude of 4.9.

This is much brighter than FL32 at magnitude 5.7, also an A class star and Fl 35 at magnitude 6.3 which is of course below naked eye visibility and in theory would not have been seen by Flamsteed yet has a FL number. Fl 35 is an orange K class star.

Does anyone else come across these discrepancies when they check their photographs.

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