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Re: Mars occultation or close approach tonight
From: Russell D. Sampson
Date: 2023 Jan 31, 12:25 -0500
From: Russell D. Sampson
Date: 2023 Jan 31, 12:25 -0500
Frank:
Sorry, that ratio should be 30:1 since the Earth rotates about 15-degrees per hour, while the moon's apparent angular orbital rate is about 0.5-degrees per hour ... 15:0.5 or 30:1.
Russ
On Tue, Jan 31, 2023 at 12:17 PM Russell Sampson <rsampson314@gmail.com> wrote:
FrankInteresting problem. I was watching the moon approaching Mars last night too but was interrupted by clouds and sleep.Four things come to mind regarding the apparent slowness of the moon; 1) apogee/perigee and Kepler’s laws (apogee on February 4), 2) parallax due to the spinning Earth angular rotation rate vs angular orbital rate of moon (15:1) which is at maximum when moon is at meridian, 3) measurement uncertainty of visual observations possibly due to the gibbous phase and 4) moon near a node so moon is approaching Mars at an angle to the ecliptic and thus its component of motion along ecliptic is at a minimum (ascending node January 28).Such a fun and complex problem.Russell SampsonSent from my iPhoneOn Jan 30, 2023, at 23:31, Frank Reed <NoReply_FrankReed@fer3.com> wrote:Anyone watching?? I checked at 6:00pm (Eastern US time)... At that time, the distance from Mars to the center of the Moon was just about 2.5° by visual estimate, counting Moon diameters. And now, at 11:00pm (EST), it's about 1°. Hmm... five hours elapsed, but the distance has changed by only 1.5°. We know that lunar distances change at a rate of just about 0.5° --that's one average apparent lunar diameter in one hour. Not even close! So what's going on?? Why is the lunar distance changing at the "wrong" rate?
Frank Reed
PS: The image of Mars is just for fun!File:
