Obtaining an observatory code should be a goal set by anyone who is interested in building their own permanent observatory or those who plan to observe celestial objects from the same location every viewing session. The observatory code is almost a necessity when submitting astrometry or producing photometry of minor planets for publication. Too, while the field of astrometry does require very technical information on equipment, software, and knowledge, the following information only highlights the very basic information and equipment needed to obtain an observatory code. More detailed information can be found on the IAU/MPC Website.
Purpose for an Observatory Code
The primary purpose for obtaining an observatory code is to record specific details about an observing site and the types of instruments used within a specific observatory. This information is used to assist in calculating any celestial measurements produced from the specific observatory.
The observatory code will not only tell the Minor Planet Center (where most data is published), or others the observatories location or what equipment is in use, it will “announce” to many worldwide astronomical centers and stations that there is an active observatory at this particular location if follow-up observations of minor planets or other objects are needed.
The Telescope – Refracting and Reflecting
The standard telescopes consist of refractors (which use a lens) and reflectors (which use mirrors). While refractors usually produce a “sharper” image, reflectors are normally chosen because they provide more “light-gathering” power for the price. Either of these will work to obtain an observatory code and they are only limited by the amount of funds the user wishes to spend.
The telescope mount is the most important factor to take into consideration when purchasing the telescope. The mount should be capable of guiding on an object for a period of time usually no less than 30 seconds and the mount should be VERY sturdy! As with the type of telescope used, the better mounts can be costly.
The “go-to” telescope works very well for slewing to targets and, if purchasing a new telescope, this should be taken into consideration. Some well known telescope companies are Meade, RCOS, Celestron, and Orion.
The Charged Coupled Device (CCD)
A lot of technical details can be brought into consideration when discussing CCD imagers. In a nutshell, the CCD is basically a high-tech digital camera that is capable of collecting photons and converting them into electrical pulses, which are generated into an image on a computer monitor. The CCD is also capable of taking long exposures which allows more photons to be collected from the light source, allowing the system to record fainter objects (which is highly desired in this field). Research based CCD imagers come in a variety of types and styles with the most common probably being the SBIG (Santa Barbra Instruments Group) CCD cameras and the Apogee CCD cameras.
Software:
The software used will be determined according to the likings of the person who will be performing the astrometry. A few examples of Astrometry software are: MPO Canopus, Astrometrica, CCDSoft, and MaximDL. This particular software analyzes the images acquired from the CCD and “matches” the images to a known star chart. Since positions are known of the stars within the field, it is then possible to use the images as a “grid” to measure any objects that may be in the field of view. The software basically calculates the stars in a field, and “aligns” the image with the stars from a digital star chart.
Which Minor Planets to Observe?
The Minor Planet Center requires that you observe a number of “low-numbered” minor planets (such as those numbered 400 - 40,000) each on pairs of nearby nights and try to observe objects of various magnitudes. It is recommended that at least 3 minor planets be observed over a period of 2 nights to produce good results – with at least three observations from each object covering a period of at least an hour per object. Also keep in mind, the objects should be well within the limits of your equipment.
Target asteroids can be found in nearly any planetarium program capable of loading asteroids and comets. Planetarium programs such as TheSky, Cartes du Ciel, and many others are capable of generating a good set of targets to image. The MPChecker, which is found on the Minor Planet Center website, is also a great tool that can be used to search for targets within a specific area of the sky!
Imaging the Objects
The position of the target object should be determined and centered within the field of view – software should be capable of doing this. Since minor planets appear “star like” and often blend in with the stars, it can be difficult to determine that the target object is in the field of view. It is very irritating to spend an hour or more imaging an area only to find that the object is just outside the FOV! But, by spending a little time learning how to operate the telescope, CCD, and software, this issue can be easily overcome.
The Astrometry
Once the images have been acquired by the CCD and saved to the user’s computer, astrometry can be obtained from the minor planets and readied for submission to the Minor Planet Center. The images must first be reduced by the software to allow them to be measured. Once the data reduction has been completed, the computer mouse is used to simply “point-and-click” on the objects to obtain the positions of the object. The software will automatically save these positions and generate astrometry from the objects. Below is a sample of astrometry produced from asteroid G3243 which was obtained from Observatory H68, Red Barn Observatory.
G3243 KC2010 03 20.05934 06 21 10.09 -12 53 46.2 17.8 V H68
G3243 KC2010 03 20.06309 06 21 10.74 -12 53 35.3 17.7 V H68
G3243 KC2010 03 20.06686 06 21 11.43 -12 53 24.5 17.4 V H68
Once the required amount of astrometry has been collected, it is then e-mailed to the Minor Planet Center for reviewing. If acceptable, they will contact the observatory operator via e-mail assigning the new Observatory Code.
References:
International Astronomical Union, Minor Planet Center
Astrometry and Celestial Mechanics, SAO
MPC-H68, Red Barn Observatory
Brian Warner, Minor Planet Observer
Steve Farmer - Steve Farmer Jr. is an individual of many interests and hobbies. When not spending time with his wife and four children, he is an employee ...
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