from VSSC92

More Variables to Observe using Binoculars

Tony Markham At the last section meeting, it was requested that more variables be added to the section's programme that are suitable for binocular observation, possibly to replace some of the less active binocular variables. The problem is, of course, that there are not many Semi-Regular / Irregular variables not already on the programme that are of suitable brightness and have sufficiently large ranges.

One possibility would be to reinstate some of the dropped Mira type variables back on to the programme, since many of these reach binocular brightness at maximum. However, there are already many variables on the Eclipsing Binary program that are currently neglected by most binocular observers. Many of these variables DO vary by much larger amounts than do many of the Semi-Regular and Irregular variables that most binocular observers follow.

As an indication of what is available, the table below summarises my observations of some of these variables during the summer and autumn of 1996. Although there may be advantages in calculating/looking up the predicted times of eclipses in advance, I usually find it more rewarding to find the eclipses by trial and error. It is worth noting that in some cases the observed magnitudes may be significantly different from the values listed on the charts - not all chart ranges are visual ranges (and different observers may see slightly different values anyway).

StarChart RangeTypePeriod Observed Range
Max ------- Min
EO Aur7.5-8.0BEA4.066d8.1/8.2 (1)
IU Aur8.2-8.9VEB1.811d8.5/8.6 (1)
LY Aur6.7-7.4VEB4.002d6.87.5(2)
ZZ Boo6.6-7.4EA4.99d6.67.5
RS CVn8.0-9.5EA4.80d7.88.9
RZ Cas6.4-7.8EA1.195d6.67.8
TV Cas7.3-8.4EA1.81d7.58.2
TW Cas8.3-9.0VEA1.428d8.6/8.7 (1)
U Cep6.7-9.0EA2.49d6.89.1
GK Cep6.9-7.5EB0.94d7.07.5
U CrB7.7-8.8VEA3.452d7.98.7
TW Dra7.5-9.8EA2.81d(6.8) (1),(3)
AI Dra7.1-8.1EA1.20d7.2/7.5 (1),(4)
BH Dra8.0-8.6EA1.82d7.9 (1)
u Her4.6-5.3EB2.051d4.85.4
EE Peg6.9-7.6EA2.63d6.7 (1)
DM Per7.6-8.4EA2.73d8.1/8.28.5(5)
IQ Per8.0-8.7EA1.74d6.9/7.07.2(6)
IZ Per7.7-8.9EA3.69d7.6/7.7 (1)
RW Tau8.0-11.6EA2.769d8.0(9.5)(7)
HU Tau6.0-6.8EA2.06d5.6/5.76.7
W UMa7.7-8.4EW0.334d7.98.5
TX UMa6.9-8.5EA3.06d6.9 (1)

  1. Not caught in eclipse
  2. Secondary eclipse approx mag 7.3
  3. Comparison star magnitudes (chart 710927) seem too faint - by up to a magnitude ?
  4. Large scatter in estimates at maximum - PA effect ?
  5. Comparison C (listed as mag 7.8 on chart 720409) looks more than half a magnitude fainter. Comparison D (mag 8.6) was used instead.
  6. Chart 721107 refers to nearby companion and gives the combined range as 7.6-8.2
  7. Too faint to be seen at mid eclipse.