(Viewed 1,315 times)

[Chicago Astronomer - Astro Joe]

I have posted this question from the General Comments area by Chicago Astronomer Grady from Texas.

Pertaining to his mystery satellite observation, It's a good question to ponder over...

---------------

Joe,
I'm curious about one thing in particular. You've seen nights when the Moon appeared closer... when it appeared abnormally larger right? If memory serves me correctly this is caused by atmospheric magnification (feel free to clarify). Perhaps one of the satellites which were listed as dimmer in magnitude were magnified by this freak magnification factor? What is your opinion of this? I sort of feel strongly that this might be the case.

Regards,
Grady


Grady,

Yes, I have noticed the phenomenon as well. A number of factors play into this, and I'm sure our resident Lunar expert, Chicago Astronomer Curt will chime in on this.

The moon, as it orbits the Earth, physically moves closer or farther at times in it's elliptical travel. The moon is about 12% larger at perigee than at apogee, and combined with atmospheric conditions, which at times act like a large magnifying glass, can appear larger than normal.

Also...we all have seen the moon tremendously large when rising over the horizon. It is thought that this is a optical illusion, as we compare the surrounding terrain to the moon, and therefore makes it appear huge. Astronomers state the if you measure the diameter of the moon at the horizon and later at zeneith, the size would be the same. I have not tried that yet, but it's quite interesting.

Now, would this apply to the mystery satellite that you observed? I don't think so. As the object travels quite rapidly across the sky, as satellites do, it would probably waver in magnitude, giving the impression that it were larger, if atmospheric conditions were a factor.

Perhaps an alien craft from Alpha Centuri....

[Rocketman]

Thanks Joe. That's some good information.

I have retracked everything again today, and It can only be less than a handful of satellites. Perhap I just thought it was brighter.

#29 I'll just leave NYI. It adds a little mystery to the log file anyway

[Centaur]

The atmosphere does not magnify the Moon. The effect is an optical illusion. On average, the Moon actually has a greater apparent angular diameter when high in the sky than when near the horizon. However, the Moon does appear noticeably larger at perigee than apogee. Although this is primarily due to its eccentric (off-centered) orbit and has very little to do with its ellipticity (ovalness). I illustrate this effect in my monthly calendar that Joe reproduces at the bottom of this website. If you look carefully, you will see that the size of my lunar images varies over the month. I have no idea what phenomenon is being referred to here regarding a satellite.