International Comet Quarterly

Special ICQ Observing Project

The ICQ organized a project to intensely observe about a dozen comets during June 2003-February 2004. The project (announced in the April 2003 issue of the ICQ) was aimed at CCD photometry, in which about a week was chosen around new moon each month during which observers were asked to observe the specific comets every possible night using a variety of photometric-aperture sizes, exposure times, instruments, and (if possible) filters. We collected much good new data, all of which have been either already published or are being prepared for publication. These data will be used in analyses to correlate brightness data obtained through different means and to establish standard recommendations for the future acquisition of such data. But because comets move and vary in brightness, it is useful to look at observations of other extended objects that do not vary in brightness (galaxies, nebulae, star clusters) to look for issues that correlate directly to the photometry of comets in a more controlled manner.

We now ask observers to extend this project through the end of 2009 to observe 29 specially chosen deep-sky objects (announced in the January 2004 issue; initially listed in previous issues: ICQ 16, 129 and 25, 57). Both CCD and visual observations are encouraged from experienced observers (i.e., preferably from those who have previously made brightness estimates of ten or more comets). These data should be reported in the full 129-column format for CCD data, or in the full 80-column format for visual data, for publication in the ICQ, the intention being to collect a large amount of data so that important information can be learned about how integrated magnitudes of celestial objects are obtained, and the contribution of biases by the use of different CCD methods and procedures; when comets are bright enough, visual photometry is also encouraged. While it is strongly encouraged that observers acquire photometry when the objects are as high in their night sky as possible (and without moonlight), it might also be useful (if time permits) to also produce photometry obtained of some objects when the altitude above the local horizon is under 10-15 degrees, with corrections for atmospheric extinction via the standard ICQ model to perform tests of this model. Since one knows the "true" brightness of these deep-sky objects from their measured brightness at high altitude, the standard extinction model *should* produce values near that "true" magnitude level when applied to observed magnitudes at low altitudes.

The deep-sky objects that we are asking observers to do photometry on were specially chosen as having morphologies that are somewhat similar to those of comets: NGC 221 = M32; NGC 936; NGC 1068 = M77; NGC 1952 = M1; NGC 2068; NGC 3031; NGC 3344; NGC 3485; NGC 3623 = M65; NGC 3627; NGC 3640; NGC 4147; NGC 4374 = M84; NGC 4406 = M86; NGC 4486 = M87; NGC 4594 = M104; NGC 4649 = M60; NGC 5024; NGC 5236 = M83; NGC 5272 = M3; NGC 6356; NGC 6384; NGC 6426; NGC 6712; NGC 6760; NGC 6781; NGC 6934; NGC 7078 = M15; and UGC 5373. We ask that observers only contribute data on these 29 objects, not on other deep-sky objects. Observers should report the deep-sky object's full NGC or UGC designation in the normal designation columns for comets in the full ICQ format (80 characters per record for visual data; 129 characters for CCD data), and it is advised that descriptive notes be included (as these will be published in the ICQ along with properly tabulated photometry of deep-sky objects), wherein the observer should include a position for each and every deep-sky object observed so that the identity can be double-checked before publication.


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