The Skyhound's Guide to Finding Comets
For SkyTools Users
SkyTools users will discover that finding comets isn't all that difficult because many of the questions that arise are answered by the program. The custom telescope finder chart will be a big help. SkyTools will only display comets on the chart that are bright enough to be visible in your scope under your observing conditions. The coma diameter and tail position is drawn for you as it will appear in your eyepiece.
The first thing a SkyTools user will need to do is download the latest comet orbital elements and coma diameters by downloading the latest "current comets" observing list. This observing list contains the brighter comets and current data. The latest orbital elements are imported to the supplemental comet database along with each object. The latest sizes and magnitudes are also included.
Once you have an observing list, use the Observation Planner to find out which comets are observable from your location and when the optimum time to observe them is.
Select your custom telescope finder chart as the default. Now right click on the comet in the observing list and select either view or print chart. Now all you have to do is use the chart at the appointed time.
Begin by positively identifying the field in the eyepiece. Look for a round fuzzy object. Make sure you are dark adapted, in a relaxed position, and try to keep both eyes open. If close to your limiting magnitude you may have to use averted vision. Look just to one side of the comet's predicted location. Sometimes gently moving the scope can bring it out.
Try using higher magnifications as this usually makes the comet appear more easily visible because of the increase in contrast. Be carefult not to usee too much, however. If you spread the light over more than 1/4 of the field of view it may be difficult to detect. Note that if you use the chart at a time that is different from the one marked, the comet will not be exactly at the location plotted. In some cases comets can move significantly in only a few minutes.
Remember that you are looking for something similar to a round, fuzzy galaxy. If the comet is near your limiting magnitude or your sky is not completely dark, you may only see a bright center. If there is no bright central concentration, you may not see anything at all under these conditions.
SkyTools draws the diameter of the comet's coma as a circle unless it is too small on the chart to show it clearly. In this case a square symbol of a fixed size is drawn instead.
The line that SkyTools draws coming out of the comet tells you the direction of the ion tail. Keep in mind that the tail is usually invisible for most faint telescopic comets unless you are using large aperture. Even then, a tail will probably not be present. It's always a good idea to look for one, though! You should take a long look at the comet even if you saw it on the previous night. Comets can change their appearance quickly.
Keep in mind that the length of the tail line tells you only the degree of geometric forshortening. If the line is ten times the radius of the coma circle you are seeing the tail at a right angle. This is probably your best shot at seeing it. If the line is very short or invisible the tail is pointing toward or away from us, making it very difficult to see.
Good luck, and good hunting!
Skyhound's Guide to Comets
Skyhound's Guide to Finding Comets
Astronomical Headlines (IAU)