Telescope Reviews: unusual use for binoculars

The Clarke Belt, also known as the geostationary belt, is the orbital region directly above the Earth's equator at a height of about 22,400 miles (35,800 km). It's named after Arthur C. Clarke, who first proposed the idea of putting satellites up there, where they could in effect stand still above a spot on the equator. I found the equation for figuring the declination on the following page, and there's more about it in the "next in thread" reply by "b_gimle":

http://www.satobs.org/seesat/Oct-2005/0167.html

I'm not trig-fluent, but maybe someone else can help on the formula. If you know the aiming point from your location to a DirecTV (or DBS or Intelsat or Telstar or Nimiq or Anik or Galaxy or Echostar or Hotbird or Astra, etc.) satellite, that will tell you the declination of the geostationary belt from your location.

Given that the satellites are at about 00:00, -5 (plus or minus 30 minutes of RA, with other footnotes) at shadow entry, there's a nice asterism, a rectangle whose southern two stars are 30 and 33 Piscium, and as seen from here they go north of those stars. On good evenings, from here the first ones become visible around there when that asterism is between 15 and 20 degrees above the horizon. As the asterism progresses through the sky, different ones become visible in that general area. One footnote is that the exact RA and Dec spot of eclipse entry moves to the west in RA and Dec. (I don't mean the sidereal motion of the Earth's shadow through the night sky; it's actually some sort of extra effect due to spherical geometry and/or the curved edge of the Earth's shadow, or something. Having a program that will show you where the Earth's shadow is would be helpful.)

The solar panels of the satellites in general are aimed at the center of the Earth, not the Sun (though of course they are sunwards facing). You need to know that if you try to figure out the Sun-satellite-observer geometry.

Another footnote is that this effect seems to be most pronounced when, as seen from the satellites, the observer is as near as can be to the Earth's limb. So, for example, there is a group that is near our meridian, and I have never managed to see those with my smaller binoculars. But earlier in the evening, in the east-southeast, the ones there tend to get much brighter. (The ones that brighten three hours early violate this "rule".)

Talking about them being light pollution, several months or a year or two ago on a different forum, a minor-planet observer called galaxies the "vermin of the sky" because they interfere with trying to do astrometry of minor planets. That was of course an allusion to whomever it was who called asteroids the "vermin of the skies". So to some extent it kind of depends on your perspective what is a target and what is interference. Maybe a comparable thing could be the Moon. Before I got into frequent night-sky watching, I thought the Moon was very pretty and always liked seeing it. Then I learned that in fact the Moon is very bad for trying to see deep-space objects and other faint things in the night sky!

I'm not sure what else to tell. Once you have spotted a few, you get the hang of it. It's easiest when they are near a star of comparable brightness, because the motion of the star passing them is obvious. Of course it happens at just about the speed of a minute hand moving on a clock face, so you have to have a tolerance for very slow action.

Most of the year, geostationary satellites are magnitude +11 or +12 or fainter and so pretty much only get in the way of people trying to image objects at their declination.

The following page has explantion of and a link to a "calculator" that is intended to help spot these satellites:

http://www.satobs.org/seesat/Sep-2006/0029.html

Here's an article with more information about observing geostationary satelites in general:

http://www.satobs.org/geosats.html

Although this is definitely a binocular observing activity, I guess that I should take non-binocular questions about it via private message.

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Ed Cannon - Austin, Texas, USA

As of 23 August 2008 - Celestron Skymaster 12x60