AAVSO Bulletin 75 for 2012 - Letter to Observers

Letter to Users of 2012 Bulletin and Some AAVSO Bulletin History

                                                                                                                                     February 2012

Dear Observers,

The major changes made to the AAVSO Bulletin last year in content, format, and methods of access were very well received and are preserved in this year's Bulletin. This latest version of the AAVSO Bulletin provides a flexible resource that you can customize to serve your observing and research needs.

This year's Bulletin being numbered 75 would seem to indicate that the Bulletin has been in existence for 75 years. However, it is actually both older and younger than 75 years! In 1931, Dr. Harlow Shapley, Director of Harvard College Observatory (HCO), transferred the responsibility of producing and publishing the bi-monthly predictions of long period variable extrema to the AAVSO. These "AAVSO Bulletins" were not numbered. AAVSO Bulletins were also issued to disseminate other types of information, e.g., the compiled outburst statistics on SS Aur. The bi-monthly lists were not predicted dates but rather lists indicating which stars would be brighter than magnitude 8.0, between 8.0 and 10.0, 10.0 - 12.0, 12.0 - 14.0, and fainter than 14.0. The annual list of predicted dates of extrema were continued in the Harvard Circular until 1934, when the AAVSO began publishing them in the Circular format; these annual Bulletins were not numbered, either.

The numbering of the AAVSO Bulletin began when the AAVSO left HCO at the end of 1953, with the annual predictions for 1954 labeled "Bulletin No. 1". However, these numbered Bulletins still sometimes contained other material, including information on members and activities - more the type of information now published in the AAVSO Newsletter. A small revision to the format appeared with Bulletin 8 (predictions for 1955). By 1961 the bi-monthly lists of brightness levels had been discontinued. The first list of stars in need of more observations appeared with Bulletin 26 (predictions for 1964).

Issued in 1964, Bulletin 27 contained predictions of approximate brightnesses of the Bulletin stars based on their mean curves. These predictions were presented as a table of the number of days from maximum/minimum when each star would be brighter than magnitude 11.0 or fainter than 13.5. This table was to be used in conjunction with the annual predictions of maxima/minima dates. As the Bulletin 27 table was cumbersome to use, a graphical representation of its minima information was issued with Bulletin 29 (predictions for 1966); Bulletin 29-A indicated graphically when a star would be fainter than 13.5 and approximately when it would reach minimum.

With Bulletin 32 (predictions for 1969), the maxima information was also being presented graphically as for minima in the document Bulletin 32-B. By Bulletin 41 (predictions for 1978) A and B had been combined into Bulletin 41-A+B, in subsequent years called the Bulletin Supplement. With Bulletin 48 (predictions for 1985) the list of printed dates was discontinued and the AAVSO Bulletin was presented as the graphical representation, but with the actual dates incorporated so the Bulletin presented date and magnitude range information for the extrema. Except for cosmetic changes, this format remained unchanged until the revisions of 2011 as seen in Bulletin 74.

In Bulletin 75, 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.

I know there are many astronomical objects competing for your observing time, especially for users of moderate- to large-sized telescopes and CCDs. However, I urge you not to neglect the AAVSO Bulletin stars! There are still numerous stars in need of better coverage, particularly around minimum - even stars whose behavior at minimum no-one has ever seen. If we are to determine dates of minimum accurately, we need to know how these light curves look 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 will be going where no-one has gone before!

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 2011 (use the link in the Bulletin table) and see the unique history you 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