Getting Started

Last Updated -- 6 Feb. 1999

Why

Comet hunting improves ones skill at navigating the night sky and provides a wide variety of objects to observe. It also gives one a purpose to observe regularly. You can make a contribution to science by providing the professionals with early notification of new comets. It is a very competitive field as other comet hunters test their skills against yours in a race to be the first to be the first to spot a new comet. And finally, there is an immense feeling of satisfaction to be gained from devising a strategy, sticking to it achieving your goal!

Attitude

Attitude is everything! Comet hunting involves some skill, a little luck and a lot of patience. Don't expect to find a comet after a few hours of sweeping. Long term statistics show that it takes 400 hours to find your first comet and 200 for every comet thereafter. Although you might be lucky, you should start with the attitude that it will be a long haul and it may take many months or even years to find a comet. Enjoy the process of locating and identifying objects as this is what you'll be doing most of the time. It is also important to realize that despite your enthusiasm and hard work, others will find comets while you are hunting. These setbacks are disappointing and should be expected. The local weather won't always cooperate when its time for another sweep, so luck does play its part. But most of all, remember that you can't find a comet from your bed! There is a comet out there with your name on it but only if you make it your job to find it!

Equipment

Surprisingly, almost any telescope will do. Last century's comet hunters used long focus refractors to successfully search the sky. Today, most comet hunters prefer short focus scopes due to their wide Field of View (FOV) which enables them to sweep more of the sky in a shorter time. A short focus 8" Newtonian with a large FOV is considered by many to be the best type of instrument. Smaller scopes do not have the light gathering power and larger ones become too cumbersome to transport to a dark sky location and have a more limited FOV. Large aperture binoculars can also be used as Hyakutake and more recently, Utsunomiya have shown. They used monster 25x150 binoculars. Even small aperture binoculars will work; David Seargent found several comets using 11x65s.

Location

It is possible to hunt from a moderately light polluted suburban backyard but objects fainter than about 9th magnitude are difficult to pick up while sweeping. For better contrast, a dark sky site is required. However, as most visual comet discoveries are 10th magnitude or brighter any location that will show diffuse objects down to this magnitude will suffice.

When

Avoid the moon and twilight. Search the evening sky after twilight ends and when the moon is in the morning sky. Conversely, search the sky before morning twilight starts and the moon is in the evening sky.

Method

There are many approaches depending on your equipment and time. For large FOV Alt-Az mounted scopes, one might sweep the sky in azimuth, then adjust the scope in altitude by about half the diameter of the FOV and return to the starting point by sweeping in the reverse direction. Alt-Az mounts provide comfortable sweeping near the poles and horizon unlike equatorial mounts.

However, equatorial mounts can be used to sweep the sky in sections or blocks of RA/Dec and their Setting Circles can be used to quickly find the coordinates of suspect objects. This is a good approach for scopes with smaller FOVs.

Whatever the method, its most important to be thorough. If you leave too little overlap or sweep too fast, you might miss an object (and it is not a nice feeling hearing that someone else found a comet in the same piece of sky that you thought you had swept  :-(

Verification

As suspicious objects are found, they need to be checked against a chart. Knowing the sky will be an advantage here, as you can not afford to waste much time going through charts. Sky Atlas 2000 will show almost all objects visible in an 8" scope from a dark sky.
Often there are not enough faint stars plotted on it, especially in crowded areas with many galaxies. In this case, you need another atlas (or custom chart) which shows stars down to magnitude 11 or fainter. You could create your own using a planetarium style program, or invest in a Herald-Bobroff AstroAtlas, Uranometria, or Millenium star-atlas. Be careful, as some Deep Sky Objects (DSO) are not plotted on all atlases, and sometimes they are plotted at the wrong coordinates.

If the object is not a DSO, you may have found a "known" comet or faint periodic comet in outburst. They can be ruled out using an ephemeris which shows the coordinates of all known comets. These are available from Greg Bryant's bimonthly Comet Tales publication, or David Seargent's Perihelion magazine. The most current information is available from the IAU's Web site at http://cfa-www.harvard.edu/cfa/ps/Headlines.html and should be considered as the authoritative source.

Having ruled out DSOs and known comets, make an eyepiece drawing. If it is a comet, it will move. Make a drawing of the FOV using a low power and high power eyepiece. Include as many faint stars as possible and note the object's alignment with the field stars. Be as accurate as possible because you will need to report its position and direction/rate of motion. This can be tricky if its not near any stars, so practice beforehand on known comets to get a feel for their appearance and rate of motion. If you can not detect motion be very skeptical and do not report it yet. Wait for the next night to confirm its motion. 95% of reports received by the IAU from "unknown" observers turn out to be false alarms. Make sure you are not embarrassed by "crying wolf" before you are certain of your facts.

Reporting

The preferred medium is e-mail although fax and/or phone can be used in an emergency. The IAU also provides a "Discovery Form" that can be filled in via their Web page. You will need to provide the following details; e-mail the information to cbat@cfa.harvard.edu

What next?

If this is your first comet discovery, expect skepticism from the IAU. As stated earlier, 95% of new discoveries from unknown observers are incorrect. Once the IAU receives your message they will contact several observers to confirm your discovery. This may take anywhere from a few hours to a few days, depending on whether the comet is visible from both hemispheres and local weather conditions. Once confirmed, the comet is assigned a designation based upon the year and half month of discovery. An announcement circular is issued to report the comet to the astronomical community. After a few more days, once sufficient accurate positions have been received to compute an orbit, the comet is named.
 

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