The following graphs summarze useful information for AAVSO members interested in observing blazars on the AAVSO Blazar Program list.

BLAZAR LIST

The list of AAVSO Blazar Program objects will number ~50.  Charts are available for ~8, so far.  Here's a brief summary of information on the list of charted blazars.

      AAVSO   Common     RA RA RA  Dec  Dec    RA     Dec  Approx  Mo
      Name    Name       hh mm ss  deg   '   deg.fr deg.fr   Mv     #

    1 0216+42 3C 66A      2 22 40   43   2.1  35.67  43.04  14.7  10.91
    2 0732+17 PKS0732+17  7 38  7   17  42.3 114.53  17.71  16.7   1.54
    3 1058+38 Mark 421   11  4 27   38  12.5 166.11  38.21  13     3.26
    4 1216+28 W Com      12 21 32   28  14.0 185.38  28.23  14.7   3.91
    5 1253-05 3C 279     12 56 11   -5 -47.3 194.05  -5.79  16     4.20
    6 1650+39 Mark 501   16 53 52   39  45.6 253.47  39.76  13.5   6.18
    7 2153-30 PKS2155-30 21 58 52  -30 -13.5 329.72 -30.23  12.9   8.72
    8 2158+41 BL Lac     22  2 43   42  16.6 330.68  42.28  14.8   8.76
    9 2342+51 2342+514   23 47  5   51  42.3 356.77  51.71  15.6   9.63

The last column ("Mo #") is the month value for midnight transit, and is explained in the next section.

MIDNIGHT TRANIST DATES

Figure 1.  Midnight transit dates for the blazar list.

For example, BL Lac tranits at midnight each year on August 23 (month value 8.76).  The way to use this graph is to ask "What blazars can be best observed in October?"  To find out, convert October 15 to a month value of 10.5, then imagine drawing a horizontal line that intersects the left side at 10.5. For this example, the answer is "3C 66A," which transits at midnight in late October.

APPROXIMATE MAGNITUDES

The next graph is a tentative plot of approximate V-filter magnitudes for the charted blazars.

Figure 2.  Approximate V-magnitudes.

OBSERVING NOTES

Note that 0732+17 has a nearby bright star that could easily contaminate the photometry "signal circle area" or "reference annulus area."  I recommend (not yet the AAVSO position) using a smallest-possible signal circle radius, a large middle gap width, and a large reference annulus width that is completely away from the nearby star - as the following figure illustrates (terminology is defined below).

Figure 3.  Zoom and crop of 0732+17 (center of annulus pattern) showing suggested photometry annulus set for avoiding influence of bright nearby star.  The nearby star is 5.4 "arc to the west and has Mv = 15.5 (versus the blazar Mv = 16.67 at the time of this image).  FOV = 1.84x1.64 'arc, north up, east left.  RGA = 36a (see definitions, below).

The photometry annulus pattern depicted can be used for most (but not all) of the reference stars in the AAVSO chart for 0732+17.

The following blazars (in the above list) deserve a similar caution in annulus choice due to nearby stars:  1058+38 (Mark 421), 2158+41 (BL Lac), and 2342+51.

A more difficult problem is posed by blazars whose galactic emission is bright enough to affect the blazar magnitude measurement.  The following blazars (in the above list) should be dealt with very cautiosuly due to their galactic emission:  1058+38 (Mark421) and 1650+39 (Mark 501).
 

DEFINITIONS

    signal circle area = pixels within area of the innermost circle containing the object of interest
    gap annulus area = pixels within the middle annulus (ignored by the photometry calculations)
    reference annulus area = pixels in the outer annulus used for establishing a background level (subtracted from the signal circle pixel counts before intensity is calculated)
    RGA = set of 3 numbers defining the annulus pattern; R = radius of signal circle, G = gap annulus width, A = reference annulus width.
                (RGA is a set of 3 single-digit hexadecimal numbers; e.g., RGA=36a means R = 3 pixels, G = 6 pixels and A = 10 pixels)
                Note:  This is my persoanl terminology, and is not recognized by AAVSO.

This site opened:  September 12, 2003.  Last Update:  September 27, 2003