Comet ISON - Time Sensitive Message!!!

[HenryC]

If you're an early riser, and its clear tomorrow, you might be able to catch a glimpse of Comet ISON (it was discovered by the International Space Observation Network) tomorrow morning.  These instructions are good for a few days, because the comet is moving slowly across the stars as it falls towards the sun.

Find out when first light is at dawn at your location, you'll only have a brief time between the comet's highest point in the sky and before the sky starts to lighten up and washes everything out.

Go to this website

http://aa.usno.navy.mil/data/docs/celnavtable.php

Enter your latitude and longitude (look up the nearest big town's lat-lon on the web if you don't know your coordinates).

Enter the date (18 Nov, 2013), and the Universal Time (UT) of 'first-light' (an hour or two before actual sunrise). First light here in S Florida is about 6 AM EST, or 1100 UT.

Universal Time is five hours added to your time if you are in the Eastern Time Zone; add six if you live in Central, seven in Mountain, and eight in Pacific. Push the "Get Data" button, the calculator will do its magic.

Scroll down the columns marked Hc and Zn in "Almanac Data"  for the star Spica (ISON will be very close to Spica tomorrow morning, and in the same general area for the next few days. It will be low in the SE.

When I do this for my location, Fort Lauderdale, (Lat 26d 12', Lon 80d  12') at 6 AM EST my time (1100 UT) it shows Spica (and the nearby comet) will be at altitude 21d 13.6' above the horizon, and an azimuth (compass bearing) of 115.3 d.  At that moment, the sun will be 9d 40.9' BELOW the horizon, so the sky should still be dark enough to see the comet.

The comet will be a fuzzy spot barely visible to the naked eye if its clear and the sky is dark.  It should be easy in binoculars.

Remember, comets don't flash across the sky like meteors, they rise every day and move slowly amongst the stars, only a few degrees each day, so if its cloudy tomorrow you still have a few days before it gets too close to the sun to see. 

In a week or so ISON will plunge towards the sun, passing within one solar diameter of the solar surface.  If it survives the heat and doesn't boil away (comets are just big snowballs and evaporate easily near the sun) we will have another chance to see it in December as it pivots around the sun and its orbit carries it back out towards deep space.

Comets are very common, there are several of these visitors every year, but most don't pass near enough to both earth and sun to be easily visible without a telescope.  But when they do, they can be absolutely spectacular sights.  When skies were dark and people were often up before daybreak, our ancestors were often terrified by the passage of a bright one.   Maybe this year we'll ger lucky


Good luck.