------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 3174 2016 Jun 04 12.08UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK Backup: gmh@wdcc1.bnsc.rl.ac.uk WORLD WIDE WEB http://www.theastronomer.org ------------------------------------------------------------------- CH CYGNI: B AND V PHOTOMETRY Elizabeth Waagen, AAVSO, reports on their special notice 417 the following: Dr. Margarita Karovska (Harvard-Smithosonian Center for Astrophysics) is urgently requesting B and V photometry of the symbiotic variable CH Cyg from now until at least the end of August. Observations made twice a week are sufficient; time series observations are not needed. Spectroscopy would also be very welcome and appreciated. The AAVSO has had a campaign on CH Cyg for Dr. Karovska ongoing for the past several years (links below). However, Dr. Karovska is making this urgent request now because the most recent AAVSO observations show that the B light curve is declining considerably more rapidly than the V, and it is extremely important to follow this activity. Both B and V are needed to keep track of the relative rates of dimming. Until the campaign launched by the AAVSO at Dr. Karovska's request a few years ago, there was little coverage of CH Cyg in B, so its complex long term behaviour in that band is not well known. Thus, obtaining solid coverage in B (and in V for correlation) is vital. Visual observations have been valuable throughout this campaign and visual observers are encouraged to continue their observations. Information on the CH Cyg campaign may be found in: AAVSO Alert Notice 454 (https://www.aavso.org/aavso-alert-notice-454) and AAVSO Special Notices #267, #268, #294, and #320 (https://www.aavso.org/aavso-special-notice-267, -268, -294, -320). Please report observations to the AAVSO International Database as CH CYG and also send monthly to Gary Poyner for the TA column. Please ensure the filter used is quoted for each result. Charts are available on the BAAVSS website as well as AAVSO. Coordinates: RA 19 24 33.07 Dec. +50 14 29.1 (J2000.0) This campaign is being followed on the AAVSO Observing Campaigns page (https://www.aavso.org/observing-campaigns). Guy M Hurst