Selecting Variable Star Targets

By now, you should feel comfortable with your growing knowledge regarding variable stars and you will probably have little difficulty selecting the variable stars that you wish to begin observing. If I'm wrong and you still feel a bit unsure of yourself, let me help a little. When selecting a variable star that will be suitable for observation, consider these thoughts: Which stars are visible during the current season? How hard do I want to hunt for a variable star? Are there charts available for the stars that I wish to observe? Is there somewhere that

I can check my estimates? How often will I be able to get out and observe?

Your first concern should probably be the season. Searching during the month of July for a star that rises in December will be disappointing ... if you're normal. An understanding of which constellations are visible during the various seasons will help you in this regard. A good star atlas is also recommended. Looking for a star positioned at declination -75° while standing in your backyard in Alberta will bring to light the need to understand the celestial coordinate system. Not all stars are visible to all observers standing on the surface of the Earth. That's why observers in Australia, New Zealand, or South Africa observe some stars that are not visible to observers in England, Belgium, Germany or the USA. Of course, depending upon your location, there are many stars that are visible to both southern and northern hemisphere observers during different seasons. For northern observers, Orion is a winter constellation while southern observers know the "Hunter" as a summer constellation.

Along the same line of thought, understanding the limitations of your equipment will allow you to forego the frustration of searching for a 14T0 cataclysmic variable using a 6-inch telescope. Pursuing faint stars with an instrument of insufficient size is fruitless. Anyway, there is no need to feel you must observe the faintest stars. There are thousands of brighter, poorly studied variables awaiting your scrutiny. Regardless of the size of your observing instrument, you will have access to more stars than you can study in a lifetime.

Think about how hard you want to work at finding a variable too. This may sound a bit confusing but some variables are easy to find while others are more difficult to find. It should be obvious that bright stars are easier to see than fainter ones, but you should also consider stars embedded in dense star fields, variables visible only during outburst, stars visible at the extreme viewing limits of your equipment, or supernovae that look like field stars. These are just a few examples of when variable stars can be difficult to locate. If you want an example, experiment with the challenges of observing the variable stars embedded within the Orion nebula or the open clusters found around the constellations of Scorpius and Sagittarius.

Have you considered variable stars for which no chart exists? With over 36,000 variable stars identified within the GCVS alone, and sundry new ones being found each year, you will find many without any chart available. These variables are poorly studied stars and little information, including charts and comparison stars, will be found. Of course it's easier, safer, and quicker to stick with the well-studied variables stars; however, much enjoyment can be found if you leave the well traveled road. I think Robert Frost said it best,

Two roads diverged in a wood, and I -I took the one less traveled by, And that has made all the difference.

After making your first few estimates as to the brightness of a variable star, you will begin to question your accuracy. It's human nature to doubt and, anyway, you should be concerned with errors and make every effort to ensure that your estimate is as accurate as possible. No one wants to record errors, and reporting gross inaccuracies is embarrassing. Doubt is the Universe's way of reminding you to check your work. The Variable Star Network (VSNET), provides nightly observation reports for hundreds of variable stars showing what other observers around the world are estimating. When you first begin, you should be practicing on well-known stars and by doing so you will have no trouble finding the latest observation reports for hundreds, perhaps thousands, of well-known variable stars with which you can compare your estimates. As you develop experience, you'll find less need to check and see what others are reporting. Eventually, your confidence will be such that, in your opinion, only your estimate is correct; everyone else is a little bit off.

Begin to understand the time commitment required for observing variable stars. When you first start observing variable stars it will be effortless to make time to get out under the night sky and observe. You'll have superhuman strength, you will be indefatigable, dawn to dusk observing will seem effortless, cold air will be refreshing, going to work after a 90-minute nap will be an acceptable trade. A couple of weeks later, reality intrudes. Develop a sustainable effort, one that keeps you interested but doesn't lead to an impossible undertaking. Remember, the stars will be there for years to come. Perhaps longer.

With these thoughts in mind, you are ready to begin to make some serious plans. It's time to prepare a list of targets and march boldly into the darkness, seize the night and observe variable stars!

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