Sky & Telescope - October 2020 - 40

Artificial Satellites
the 0h line of R.A. intersects the CE - the First Point of Aries.
In the early evening, this zone will be near the eastern horizon. At around 1 a.m. (daylight-saving time) it'll be roughly
due south, and at dawn near the western horizon.

Geosat Flare Visibility
Latitude

Autumn Peak

Spring Peak

Displacement*

+70°

Oct. 13

February 28

8.5° S

+60°

Oct. 12

March 1

8.0° S

+50°

Oct. 10

March 3

7.3° S

+40°

Oct. 7

March 6

6.3° S

+30°

Oct. 4

March 9

5.0° S

+20°

Oct. 1

March 12

3.5° S

+10°

Sept. 27

March 16

1.8° S

Eclipse zone: No flares visible

-10°

Sept. 19

March 24

1.8° N

-20°

Sept. 15

March 28

3.5° N

-30°

Sept. 12

April 1

5.0° N

-40°

Sept. 9

April 4

6.3° N

-50°

Sept. 6

April 7

7.3° N

-60°

Sept. 4

April 9

8.0° N

-70°

Sept. 3

April 10

8.5° N

*Displacement refers to north or south offset of the flare zone from the celestial
equator for the listed latitude.

„ STEVE DAUBERT is a retired research scientist and author.
His most recent book is Between the Rocks and the Stars.
FURTHER READING:
For flare predictions tailored to your location go to:
calsky.com/?geosat
To see an interactive representation of Earth-orbiting satellites
(including geosats): http://stuffin.space
A complete list of geosats is found here:
satsig.net/sslist.htm

S STREAKS AND GEOSATS This photo was captured with a camera on a tripod. Diurnal rotation causes the stars to trail across the field, but geostationary satellites register as points of light since, by definition, their positions are fixed with respect to Earth's surface.

40

OCTOBER 2 02 0 * SK Y & TELESCOPE

BOB KING

0°

Another way to visualize the situation is to imagine that
the anti-solar point is a searchlight beam moving along the
string of satellites, illuminating one geosat (or several) at a
time as it slowly sweeps from west to east during the course
of the night. It's worth bearing in mind that the calculated
flare point is, to some extent, only a guide to where you
should look. Several factors working together can displace
where a flare will brighten to visibility. The flares must
appear along a track parallel to the celestial equator since
that's where geosats orbit, but their solar panels aren't all
aligned toward the Sun in exactly the same way, so the flare
location can deviate by 15° east or west of the calculated
position. That's why we observe flares in a "zone" rather than
at a single spot.
During flare season, the passing display of geosats creates
an incomparable vista. It's a spectacle that provides a good
reason to host an all-night, flare-watching star party.



http://www.calsky.com/?geosat http://www.stuffin.space http://www.satsig.net/sslist.htm

Sky & Telescope - October 2020

Table of Contents for the Digital Edition of Sky & Telescope - October 2020

Contents
Sky & Telescope - October 2020 - Cover1
Sky & Telescope - October 2020 - Cover2
Sky & Telescope - October 2020 - 1
Sky & Telescope - October 2020 - Contents
Sky & Telescope - October 2020 - 3
Sky & Telescope - October 2020 - 4
Sky & Telescope - October 2020 - 5
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