[AZ-Observing] Re: Some Mars Figuring (while waiting for clear skies!)...

Greg,
Just to point out the area of a circle is defined as PI*r^2 or pi*(d^2)/4.
Looks like you used the diameter in the formula calling for radius.

I had to look it up myself, been a while for me, too.

Rick 

-----Original Message-----
From: Greg Askins [mailto:gregaskins@xxxxxxx]
Sent: Tuesday, August 26, 2003 6:43 PM
To: EVAC@xxxxxxxxxxxxxxxxx; az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Some Mars Figuring (while waiting for clear
skies!)...


While waiting for the skies to get dark (and hopefully get/stay clear) 
to view Mars this week, I started wondering just how much larger Mars 
is this week than it will be over the next few weeks (as our weather 
here in Phoenix should start to get better). Looking through my recent 
Sky&Telescopes and Astronomy magazines, I was surprised how much 
smaller Mars was depicted by the end of September (even though its 
diamater measurement was still almost 85% of maximum).
With some time on my hands (since the observing here has been difficult 
and doesn't look great tonight during the evening hours), I decided to 
calculate the total viewable size of Mars (its total area) including 
the effect of its upcoming phase. Using the data supplied here by EVAC:
http://www.eastvalleyastronomy.org/EVAC/mars-ephem03.htm
I get a total size of Mars at maximum of 494.214 square arc-seconds (I 
think this is the proper notation). I used this equation: 
(25.11/2)squared X 3.1416 X .998 phase.


Now for the comparisons (% of Max. Size and Total Size -- including 
phase effect):

Maximum (8/27/03):                      (100%)   494.214 sq.arc-secs

One month later 9/27/03:                (69.7%)  344.537 sq.arc-secs

Star party on 10/01/03:         (64.1%)  316.910 sq.arc-secs

Star party on 10/03/03:         (61.3%)  303.127 sq.arc-secs

Star party on 10/10/03:         (52.4%)  258.985 sq.arc-secs

Middle of Oct. 10/15/03:                (46.7%)  230.743 sq.arc-secs


This total size measurement should be important both for astro-imaging 
and for the overall impressiveness of Mars in the eyepiece. Somewhat 
surprisingly, by the end of September, Mars will be at less than 2/3rds 
of it's maximum size tonight -- and before the middle of October will 
be at less than 50% of maximum.

Morale of the story:  pray for some clear skies the next two weeks!

Greg Askins
Chandler, AZ

P.S. If there are mistakes in my math, I apologize -- it's been a while!

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