…continuedMining Hipparcos's Buried Treasure
A Few Observing Tips
The techniques for making visual magnitude estimates are not very demanding. (For more detailed information, see "The Lure of Variable Stars.") Since the stars on our list are 7th to 9th magnitude, they can all be seen in a good pair of binoculars. But if a star is within a couple of magnitudes of the limit for a particular instrument, it can be seen clearly only by "averted vision" directing your gaze a little to one side.
Try to select comparison stars that bracket the variable star in brightness, differ from it by less than 0.5 magnitude, and have a similar color. The colors on our charts are an excellent guide for they, like the magnitudes of the comparison stars, are derived from Tycho photometry of the Hipparcos mission. The colors are more vivid than those you will see at night. By convention, comparison-star magnitudes are indicated to tenths with the decimal point omitted. Thus, a star labeled "79" is magnitude 7.9 visually.