Bright Satellites & Resources


This page provides resources for beginners new to visually observing Earth orbiting man-made satellites. Two subscribers to SeeSat-L maintain a group of satellite elements for bright satellites.

100 (or so) Brightest Satellites

Jay Respler created and maintains an element set or elset on T.S. Kelso's web site in the U.S.

These satellites are normally brighter than magnitude 4, two magnitudes brighter than the minimum limit of magnitude 6, the brightness needed in order to be seen with the un-aided eye in clear dark skys. A one magnitude difference corresponds to a factor 2.5 difference in brightness; therefore, a difference of five magnitudes is a factor of 100 difference in brightness. Further discussion on the meaning of "magnitude" values and their relationship can be found in this archived post on SeeSat-L.

The list of satellites in the elset by Jay Respler is reproduced here and is sorted by descending order of inclination. The elset provided by Jay is sorted by ascending order of the satellite's catalog number.

Resources needed to observe satellites

Prediction Services

There are several satellite viewing prediction services on the web.

The Heavens-Above site is a prediction service which includes Jay Respler's "100 (or so) Brightest Satellites", among others. In addition, this service provides predictions for the Iridium series of satellites that provide local flares to observers. If you are a beginning observer you might want to read the Beginner's Observing Guide page.

Please go to the VSO satellite prediction page to find links to other good prediction sites.

Tracking Program

First, you need to obtain a tracking program if you want to generate your own predictions either in tabular or graphical form. There are satellite prediction services on the Internet that will generate predictions in tabular form for a limited number of satellites. But if you want to predict satellites of your own choosing in a format you find more useful, you will need to install a tracking program on your computer. You can find some tracking programs and prediction services links on the Tracking Programs and TLE Resources page and on the Satellite Prediction Software page.

Two Line Elements (TLEs)

There are a few sources on the internet that provide the orbital elements of various types of satellites. You can find some of these resources on the Tracking Program and TLE Resources page.

Information in the TLE

You can find a representative TLE on the Tracking Program and TLE Resources page, with information on some of the individual elements. Some of the information that is helpful to a newcomer is the satellite catalog number, the satellite international designation, the epoch date and the inclination of the satellite.


In order for an observer to view a satellite he or she must be near to or below the Earth latitude that corresponds to the inclination of a given satellite. As an example, if you lived above 70 N or S latitude, (besides probably being cold ;-) you would not be able to observe the International Space Station, which has an inclination of 51.6 degrees. The ISS's most extreme northern or southern track over the Earth never exceeds 51.6 N or S latitude.

Fortunately, most of the satellites in the "50 Brightest Satellites" and "100 (or so) Brightest Satellites" listings have an inclination greater than 70 degrees, thus you could live as far north or south as 80 degrees latitude and observe most of these satellites.

Generally, for satellites having an altitude of 300 km or less, your viewing location can be no greater than 10 degrees in latitude above the corresponding inclination of a given satellite. The higher the altitude of the satellite, the higher the satellite will be above the horizon to an observer.

Magnitude of Brightness Associated with a Satellite

Information on visual magnitude is not included in a satellite's orbital elements; however, some satellite prediction programs include databases of standard magnitude data, enabling them to estimate realistic magnitude based upon range to the observer and phase angle of the satellite for any point of travel above the horizon.

A separate listing of over 1500 satellites and their associated magnitude can be found in a listing called periodically updated by Mike McCants that is used in his Quicksat satellite tracking program. This listing can stand alone.

The "Molczan" magnitude values and the "Quicksat" magnitude values are based on different assumptions and different observations.


The "Molczan" magnitude values are based on 50% illumination; the "Quicksat" values are based on 100% illumination. The difference mathematically is 0.8 magnitude. The "Molczan" magnitudes are 0.8 magnitudes fainter due to this assumption.

The "Molczan" values are based on "mean" magnitudes, while the "Quicksat" values are based on "maximum" magnitudes. Typically (for a cylinder) the "mean" magnitude is about 0.7 magnitudes fainter than the "maximum" magnitude. On average, the cylinder is tilted about 45 degrees relative to the observer compared to its maximum possible attitude.

The sum of the two differences in magnitude is about 1.5 magnitudes. So a typical Cosmos rocket would appear in the Quicksat magnitude file as intrinsic 4.0 and in the Molczan file as intrinsic 5.5 , that is, its value of brightness in magnitude would be dimmer compared to the Quicksat value.


Many of the Molczan magnitudes are derived (mathematically) from the physical dimensions of the object. This magnitude value is denoted by "d". The Molczan magnitudes that are derived from observations are denoted with "v" and were computed by Rainer Kracht based on Russell Eberst's observations.

The Quicksat intrinsic magnitude values were derived from observations by Mike McCants.

Regardless of what magnitude value system you use as a reference, most likely the satellite will not display its brightness at the magnitude value provided in either list except possibly at one point in time during its transit.

Either magnitude value system compares one satellite to another in terms of brightness and only provides a relative comparison, not necessarily an absolute value.

Your actual observed brightness will vary depending upon the actual percentage of illumination, range, elevation and visibility conditions. If the satellite is at a low elevation with the majority of the sunlight falling opposite to the side being viewed and visibility conditions are poor, chances are you will not observe the satellite. It's important that satellites be viewed in the portion of the sky opposite the rising or setting sun in order to see their potential brightness. In other words, view satellites in the western portion of the sky in the morning and in the eastern sky in the evening.

Description of Satellites

Some good resources that describe the function of various satellites are:


Jonathan's Space Report

Mark Wade's Encyclopedia Astronautica

Links to the: VSO Home Page, Observing Guide, Satellite Predictions