Factors that Impact the Visibility of a Comet
Comets orbit around in space in reasonably predictable fashion. Prior to stargazing software, the tracking of a particular comet meant you had study the astronomy publications to find the various published comet positions. These positions, known as an ephemeris would give you the comet positions so that you could mark them down onto a star chart.
Unfortunately, these co-ordinates are given with gaps of 5 days between each position. This does lead to quite a bit of guesswork on the part of the stargazer, who has to do a certain amount of second-guessing exactly where the comet will appear in the sky. When plotting the path of a comet, you have to remember that the time given for these positions are given in 0h Universal Time. So any variation on time zone, or even for viewing at night has to be factored in. Otherwise you will miss the comet completely.
All is not lost though, because technology is now here to give you a helping hand. Computer stargazing software can be programmed to calculate the path of an expected comet once you feed in the available information. The software will even allow you to print out the comet’s path through your viewing area, complete with the optimum viewing time. In fact, a number of software programs are pre-programmed to include the more popular comets.
Once you have plotted the path of your comet, and the best time to see it, you still have to find it in the sky. Comets are usually quite small, and of low contrast, and even with the most precise plotting, can be difficult to see against the night sky. You don’t need a massively high-powered telescope to view comets. The brighter ones can be viewed perfectly well through a good quality pair of binoculars. Sadly for the comet hunter, most comets are faint, small, and not very comet looking.
To view the more common comets, or for the more serious comet hunter, you will need a good telescope to do the job. You need to look for something that will give you good contrast between the comet and the background sky.
You will probably have problems viewing comets from an area with bad light pollution, as unfortunately, comets can look quite faint. They don’t even always show a good tail. In fact, most comets are only a little smudge in the sky, which can only be seen using averted vision. Averted vision is when you don’t look directly at the object, but use your peripheral vision. This makes faint objects a bit more easily seen.
A good starry night, with little or no light pollution makes ideal conditions for viewing comets. Even with precise co-ordinates and a perfect viewing night, you may still be unable to find the more common comet. So be prepared to hunt around the sky a bit, and don’t be disappointed if you can’t see it. You will probably have more luck with the next scheduled comet.