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AAVSO Bulletin 79 for 2016 - Letter to Observers

Letter to Users of 2016 Bulletin

                                                                                                                                                        February 2016

Dear Observers,

Thank you very much for your observations of AAVSO Bulletin long period variables - each observation is extremely precious. If you have not observed any of these stars, I urge you to add some of them to your program.

I know there are many astronomical objects competing for your observing time, especially for users of moderate- to large-sized telescopes and CCDs, but please don't ignore the AAVSO Bulletin stars! 73% of the Bulletin stars received fewer than 100 observations last year. These stars all need better coverage, particularly around minimum. Some of the Bulletin stars have minima no-one has ever seen. If we are to determine dates of minimum accurately, we need to know how these light curves look throughout their cycle, including around minimum. When you browse through the light curves (use the Light Curve Generator link in the Bulletin table), look for ones with sparse or no coverage and choose one or two of these to follow through minimum for at least a few cycles if you can. You can also determine which Bulletin stars are most in need of observations by clicking on the "Bulletin 79 in order of need" link on the Bulletin 79 webpage - this file lists the Bulletin stars in order of the number of observations received last year and gives that number (from 4 to 1639). Also, essentially all of the far-southern stars need more observations.

The current version of the AAVSO Bulletin provides a flexible resource that you can customize to serve your observing and research needs. In my 2012 Letter to Observers I gave the history of the AAVSO Bulletin, showing how it is has evolved over the decades.

In Bulletin 79, only those stars with an AAVSO mean curve have been included; the stars in earlier Bulletins indicated with an asterisk (*) as having no mean curve have not been included. The number of stars was reduced partly in order to help focus your observing energies on those long period variables we feel very strongly must continue to be observed on a regular basis. Some of the removed stars will be added back to the Bulletin as mean curves are determined for them.

The semiregular variable V Boo demonstrated double-maxima behavior, similar to R Cen and R Nor, for several years. In 2014, it became too irregular to accurately determine, and so predict, maxima and minima, and it was omitted from Bulletin 78. V Boo is now more regular and no longer demonstrating double-maxima behavior, so it has been included in Bulletin 79 and appears in the main table.

The Bulletin stars have decades - some, well over a century - of ongoing data provided by you and your colleagues, and continued continuity is essential to the researchers who will be analyzing these stars in the decades to come. Take a look at the table of AAVSO maxima and minima dates from 1900 through 2015 (click on the "T" link in the Bulletin table) and see the unique history you already are or can be part of. Many thanks to each of you for your valuable astronomical contributions. We look forward to continuing to receive your observations!

Good observing,

Elizabeth O. Waagen
Senior Technical Assistant

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484