Alert Notice 540: Secondary eclipse of b Persei is underway

March 10, 2016: Further to AAVSO Alert Notice 537, the anticipated secondary eclipse of b Per is underway, according to information from campaign astronomer Dr. Donald F. Collins. Dr. Collins writes:

"[The secondary eclipse of b Persei is underway. The forum post I made the evening of March 9-10 UT includes] the light curve of b Persei that shows the drastic dip in brightness tonight.  Looks like its still going down at 0300 UT.  The downward drop is observed by Paul Benni (BPAD) and me (CDK) by shooting between the clouds.  I'm almost totally socked in and b Per is setting behind my building. Hope the western observers can take it up from here.

"Keep on shooting, we should have a couple of more days of in-and-out of eclipse! We expect several ingress and egress events for the duration, and a single eclipse could last less than 24 hours. Wide world coverage is needed. Keep shooting this week even if it means shooting between the clouds on a partly cloudy night!"

The...plot [below and on the observing campaign forum thread highlighted below] shows the eclipse data to date.

Image provided by Dr. Donald Collins

b Persei (HIP 20070, SAO 29531, HR 1324, HD 26961) is located at the following coordinates (J2000):

R.A. 04 18 14.62  Dec. +50 17 43.8

High-resolution time-series observations in V should continue at least one week after the eclipse is over and b Per has returned to maximum.

It is recommended to use the star HIP 20156 (SAO 39457, HR 1330, HD 27084; the star labeled '55') on the AAVSO finder chart at 5.456 V as the comparison star. For a check star HIP 20370 (J2000 RA, dec = 04 19 13.24, +50 02 55.30) may be used if the observer's field of view is about one degree. This star is not in the AAVSO sequence. Any other AAVSO sequence stars may be used as check stars if available in the observer's field of view. Charts with a comparison star sequence for b Per may be created using the AAVSO Variable Star Plotter (VSP).

Please see Alert Notice 537 for instructions for CCD observers and for details of this campaign.

Please send observations in AAVSO format directly to as well as to the AAVSO. Please use the name "b PER" when submitting observations to the AAVSO International Database.

This observing campaign is being discussed under the thread "b Persei campaign" in the Campaigns & Observation Reports forum at

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.


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