AAVSO Bulletin 74 for 2011 - How to Use the Bulletin

The AAVSO Bulletin is essential in planning your observing schedule each month. It contains predicted dates of maxima and minima of long period variables, and shows when a variable will be rising to maximum, fading from maximum, brighter than magnitude 11.0, and fainter than magnitude 13.5. The period covered is January 2011 through February 2012. You can access the Bulletin in the following ways:

Fixed format:

• schematic file (.pdf) covering the entire sky for the entire 14 months the Bulletin covers;
• text file covering the entire sky for all 14 months containing the information in comma-separated format (.CSV) suitable for loading into a spreadsheet;
• text file (CSV) sorted in order of increasing number of observations; replaces Stars in Need of Observations lists included with earlier Bulletins

Customizable options:
Using the Bulletin Generator, you can customize the Bulletin to suit your observing/research needs. You can select:

• all stars, a specific star, or a list of stars;
• the whole year or a single month;
• all constellations or a particular constellation;
• the whole sky or a range of Right Ascension and/or Declination;
• in the schematic html file, the colors used to signify whether a star is brighter than visual magnitude 11.0 or fainter than 13.5.

On the line for a given star, you can click on the link to the AAVSO Light Curve Generator to see the star's recent behavior, to the International Variable Star Index (VSX) to see astronomical information on the star, or to the table of AAVSO observed maxima and minima for the star. The N field (number of observations during calendar year 2010) tells you if a star is well covered or needs more observations.

The first step in planning your monthly observing schedule is to determine which part of the sky you will be able to see (see Table I below). Second, choose how you will look at the Bulletin according to the options above. Check the Bulletin file you have created or downloaded to find out which observable long period variable stars will be at the appropriate brightness for your equipment.

As an example, choose the schematic file (.pdf) of the entire sky for the entire 14 months the Bulletin covers. Table I below indicates that in the month of January 2011, from 2 hours after sunset until midnight, stars between 1 hour and 9 hours of right ascension are observable. Look at the first page or two of the Bulletin .pdf to see a sample of the possibilities.

The word 'rising' means that the star is brightening towards maximum; 'fading' means it is fading from maximum. The number gives the approximate date on which the star should be at maximum or minimum.

If you have a 2.5-inch telescope which has a limiting magnitude of 10 to 11, the white boxes under January show that the stars T CAS, X SCL, W CAS, U TUC, UZ AND, and several other stars will be brighter than magnitude 11.0 during this month and so they would be good candidates for observing with a small telescope.

With the same telescope, under January, the dark gray boxes show that SV AND, S TUC, S CET, Y CEP, U CAS, and several other stars will be fainter than magnitude 13.5, and will be below the limit of a small telescope.

If you have a large-aperture telescope (6-inch or more) or a charge-coupled device (CCD), please observe faint magnitude stars, and in particular faint minima, since observers with smaller-aperture equipment can adequately cover the brighter stars.

A well-scheduled program making use of the AAVSO Bulletin will increase the value of your astronomical contribution, as well as heighten the efficiency and enjoyment of your observing.