Intrinsic Magnitude Definitions

For historical and philosophical reasons there are two different definitions of "intrinsic magnitude" (or standard magnitude).

In the 1960s, I wrote Quicksat and created the quicksat.mag file for my own use. I chose the standard range of 1000Km for my definition of intrinsic magnitude, but I also chose "full phase" and "brightest likely magnitude" for my definition.

In the days of "bulletin board systems", Ted Molczan created a file of tles on the Canadian Space Society BBS in Toronto. He placed a header line in front of each tle and that header line had a name, size, and standard magnitude. His definition was also for 1000Km range, but he chose the 90 degree phase angle and an "average" magnitude for his definition.

This file was later sent out in emails and archived on some systems to be available using ftp. Then the "Molczan" file was available on my web site. Then Ted passed the full responsibility to me and the "Molczan" file became the "McCants" file on my web site.

So, the mcnames file follows Ted's original standard (see also the separate web page) and the quicksat.mag file follows a different standard.

The differences are: 1) A phase angle definition difference causes Ted's intrinsic magnitude to be about 0.7 magnitudes fainter than a quicksat.mag file intrinsic magnitude. 2) The "average" magnitude also causes Ted's intrinsic magnitude to be about 0.7 magnitudes fainter than Quicksat's "brightest likely magnitude" (best possible object orientation).

So, the actual intrinsic magnitudes should differ by about 1.4 magnitudes between what is in the mcnames file and what is in the quicksat.mag file. Half of that is due to the phase defintion difference, so if a program is compensating for that different definition, the predicted magnitude would be the same. But the other half is a fundamental philosophical difference in definition. So a program should always generate a prediction that is about 0.7 magnitudes fainter using Ted's intrinsic magnitude compared to the quicksat.mag intrinsic magnitude.

See also the mccdesc description.

Philosophical argument: If the observer watches an object for a while and the object changes orientation sufficiently during that time, then the object has a good chance of appearing as bright as the "Quicksat prediction" and that will be about 0.7 magnitudes brighter than the "Molczan prediction". So the observation will "meet the expectation" of the Quicksat prediction and "exceed the expectation" of the Molczan prediction. Thus I prefer the Quicksat prediction because I do not want to be "surprised" that the object is "brighter than predicted". But then I've been using this system for more than a few decades and I'm used to it.