Telescope Reviews: Comet C/2007 W1 (Boattini)

Comet C/2007 W1 (Boattini) 7-17-2008 10:35UT, mag. 7.0+-0.5, Dia. 12', DC=0 to 3, no tail or coma detail seen under poor Moon washed sky

I went to Little Mtn. (111W long, 40N lat) Utah east of Salt Lake City last night (7-17-2008 4:25 MDT | 10:25 UT) to try to catch a glimpse of Comet C/2007 W1 (Boattini).

It was near full Moon, so I tried for a brief observing window between 10:25UT and 10:40UT in which the Moon was blocked by Little Mtn. low in the south-west-western sky but before the advance of the end of astronomical twilight. The comet was low in the east at altitude in a Moon washed, heavy aserol polluted sky at altitude 27 deg. An NELM of 3.7 was defined by the twin tail stars of Tau - chi and omi Tau - and gam Cet in the Cetus circlet.

Using 8x35mm binoculars (2.5 deg TFOV), the comet was not visible at its suspected region about 2 degrees northeast of Cetus circlet star lambda Cet. Because of the washed out sky conditions, a pair of 20x70mm (1.5 deg TFOV) was tried and quickly resolved comet Boattini midway between mag 8.1 HD18973 and mag 8.0 HD19137.

Because of the sky conditions, little or no detail could be seen in the 12 arcminute coma - yielding a degree of condensation DC=0 to DC=3. Visibility was improved by cupped the hands around the eyepieces inorder to exclude stray light. Again, because of the sky conditions, no tail was visible.

Brightness was estimated with low precision at mag 7.0 +- 0.5. There were few useful reference stars within 2 degrees of the comet. Using the In-Out method, the comet appeared midway in brightness between mag 8.0 HD 19137 and mag 5.9 HD 18700 and mag. 6.0 HD 19698.

The best estimated optimal magnification to view this comet is 40x. Due to time limitations I did not set up a small refractor but stuck with the binos.

I was glad to catch a brief glimpse of this intriguing visitor under a quiet sky and briefing cool mountain summer air. Comet C/2007 W1 (Boattini) was interesting to me because of its unusual orbital path as it passed the Earth. The comet skirting just below the ecliptic but perpendicular to Earth's orbital path between the Earth and Sun. It is now on its outbound leg.

It is problematic whether using this early-morning Moon-setting window will work over the next few days. The third quarter Moon will become progressively dimmer, but the Moon will come closer to the comet over the next week. The third quarter Moon will pass a few degrees away from Boattini on 7-26. Hopefully, the comet will not dim substantially as the visibility situation improves through the new Moon on August 1st. On the morning of Aug. 1, the comet will be next to pi Ari.

- Canopus56