Beginner's Observing Guide

Introduction

Perhaps youíve seen those points of light (some steady; some flashing) in the late evening or early morning hours with your naked eye while looking at the night sky. Some appear to be moving relatively fast, while others are relatively slow. If you observe the night sky with binoculars or a telescope then youíve probably seen the same thing quickly crossing your field of view.

This page will quickly get you started on predicting when you can see these objects with your naked eye (or binoculars) and be fairly certain what satellite you are viewing.

Why you can see earth orbiting satellites

Satellites are visible when the sky is dark and the satellite is able to reflect sunlight back to the observer. These conditions generally occur up to about 45 minutes before sunrise (before the sky becomes too light) and 45 minutes after sunset. Most satellites are not visible all night long. Sooner or later the earthís shadow prevents sunlight from illuminating the satellite. This is particularly true for the lower orbiting satellites which enter the earthís shadow earlier than higher orbiting satellites.

Even though the satellite is in sunlight, to the observer it may only be partially illuminated depending where in the sky it is located with respect to the sun and the observer. Just as the moon goes through lighted phases, so do satellites but in a much faster manner as they transit the sky during a pass. Because of the distance involved and the small size of the satellite you will not be able to resolve the phase of the illumination, only the intensity of the reflected light.

Of course some satellites are bigger than others and have much better reflective surfaces. The bigger and more reflective the satellite happens to be the more light can be reflected and the brighter the satellite will be to the observer.

Regardless how bright the satellite may be, you need clear, and relatively dark skies to observe them. If because of light pollution you can only see the brightest stars and planets, then you will only be able to see the brightest satellites and there arenít many of those.

Tools

The best resource on the Internet for predicting observations for low earth orbiting satellites is Chris Peatís Heavens-Above site. Without running your own prediction software, you can predict the brightest (easiest) satellites to observe to the dimmer (more difficult) satellites. The great thing is if the satellite is observable for your period of interest it will be predicted and you wonít waste time trying to predict satellites that are not observable for the period of time in question because they are either too low in the sky or the sky is not dark enough.

Terms


Having delayed your start with all of the above information, please now go to the

Heavens-Above site


to get some satellite observing predictions. Happy Viewing!

Be sure to share your first observation results with other observers on SeeSat-L .


Supplemental Information

Below is a list of some satellites a beginning observer may find interesting to observe because of their visual characteristics. The Heavens-Above site allows you to search for these satellites by entering either their common NAME, US STRATEGIC COMMAND or INTERNATIONAL LAUNCH designators.

USStrat   International
Command   launch desig.       NAME                     COMMENTS
-----        ------        -----------    ------------------------------------
20580        90037A        HST            generally +3 magnitude, may flare
21147        91017A        Lacrosse 2     +3 magnitude, reddish
21701        91063B        UARS           +3 magnitude, reddish brown
22823        93061A        Spot 3         tumbling, may provide (-)mag. flashes
24836        97030A        Iridium 914    tumbling, may provide (-)mag. flashes
24842        97030G        Iridium 911    tumbling, may provide (-)mag. flashes
24871        97034C        Iridium 920    tumbling, may provide (-)mag. flashes
25017        97064A        Lacrosse 3     +3 magnitude, reddish
25063        97074A        TRMM           +2.5 magnitude
25105        97082B        Iridium 24     tumbling, may provide (-)mag. flashes
25320        98026B        Iridium 71     tumbling, may provide (-)mag. flashes
25544        98067A        ISS            very bright (zero mag.)
25861        99039B        Okean-0r       +2.5 mag. flasher
26040        99072A        Cosmos2367     +2.5 mag.
26070        00006B        Cosmos2369r    +2.5 mag.
26354        00023A        Cosmos2370     +2.5 mag.
26473        00047A        Lacrosse 4     +3 mag., reddish
26474        00047B        Lacrosse 4r    +3 mag.
28646        05016A        Lacrosse 5     +2 mag
28647        05016B        Lacrosse 5r    +3 mag.

Related Links

Celestial Coordinates

Visual Satellite Observer's Magnitude system of brightness

Visual Satellite Observer's some Bright Satellites

Visual Satellite Observer's Catch a Flaring/Glinting Iridium satellite

SeeSat-L FAQ

Astronomical Society of South Australia


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