Friday, March 08, 2013

will we see it?

Razvan sent a question to the RASC Toronto Centre Yahoo!Group list. Asked if the comet would be visible from the DDO on Saturday night.

I waited a bit. No one else replied. So I jumped in. Said the odds were against us seeing C/2011 L4 Pan-STARRS. But I hoped I was wrong. Shared some facts (for people in south-west Ontario).

People just north of the equator are starting to see it, just barely.

On March 9 and 10, the comet will be left and slightly up from the Sun. In bright day-lit sky. Very near the Sun, about 15 degrees away. "Down in the muck," near the horizon, at about 5 degrees elevation. And probably behind the trees! Around magnitude 1.2 (according to SkyTools Pro 3). At very high atmospheric extinction levels. I.e. looking through a lot of air. At 6:15 PM tomorrow, one would see it through the equivalent of 6 atmospheres, which makes the magnitude drop to 3.1. The tail of the comet, aiming away from the Sun, tomorrow will also be nearly horizontal, making it tough to see. Approx. times for Saturday 9 March: Sun set - 6:20 PM; C/2011 L4 Pan-STARRS set - 7:00 PM; astronomical twilight ends - 7:51 PM.

On Mar 12 and 13, a young Moon will be in the area. That might help one spot the comet.

On Mar 15 and 16, the comet will be almost directly above the Sun. It might be much easier to see it against a darker sky. And the tail should be pointing up then, vertical, away from the Sun. However, the brightness will have decreased.

A rule of thumb is that the faintest comet you can see is about 3 magnitudes brighter than the faintest star you can see.

I reminded people that the fantastic photos we're seeing are taken with long exposures. 5 seconds or more. That coaxes out the detail.

I also shared, based on visibility calculations in SkyTools, that it would likely not be visible in binoculars tomorrow. One would need at least a 3" to 4" telescope...

Not great news, at this stage.

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