How to Use Bulletin 73
The AAVSO Bulletin is essential in planning your observing schedule each month. It contains predicted dates of maxima and minima of long period variables in a schematic representation and shows when a variable will be brighter than magnitude 11.0 or fainter than magnitude 13.5.
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). Secondly, check the Bulletin (reading the introductory page first!) to find out which observable long period variable stars will be at the appropriate brightness for your equipment.
Example: Table I indicates that in the month of January 2010, from 2 hours after sunset until midnight, stars between 1 hour and 9 hours of right ascension are observable. Turn to page 2 of the Bulletin and look at the possibilities. If you have a 2.5-inch telescope which has a limiting magnitude of 10 to 11, the + signs on page 2 under January show that the stars 0003-39 V Scl, 0004+51 SS Cas, 0010+46 X And, 0010-32 S Scl, 0017+55 T Cas, 0018-62 S Tuc, 0025-46 T Phe, 0040+47 U Cas, 0046+33 RR And, 0049+58 W Cas, 0125+02 R Psc, and 0152+54 U Per will be brighter than magnitude 11 during this month and so they would be good candidates for observing with a small telescope.
During the same month, with the same telescope, do not observe 0019-09 S Cet, 0044-35 X Scl, 0047+46A RV Cas, 0054-75 U Tuc, 0106-30 U Scl, 0109+40 U And, 0110+41A UZ And, 0112+72 S Cas, or 0112+08 S Psc, since these stars will be fainter than 13.5, as the - signs indicate,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.
After the star name, one or two symbols may appear. These symbols indicate differing levels of need of observation. However, caution should be used in observing these stars, as many of them are very difficult to observe or have poor charts (these charts are being improved as quickly as possible). One symbol indicates that, while CCDV or multicolor photometry exists for the star, visual observations are needed. Often these stars need visual data in the brighter section of the light curve - magnitude 12 and brighter - as the instrumental photometry is covering the fainter portion of the light curve. The symbols and their meanings are:
# - needs more observations & - needs more observations urgently @ - needs more observations very urgently % - has fair to excellent CCDV or multicolor photometry, but more visual observations are needed (usually more visual observations are needed very urgently)
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.