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Re: Precomputed lunar distances
From: Frank Reed
Date: 2005 Apr 19, 19:44 EDT
From: Frank Reed
Date: 2005 Apr 19, 19:44 EDT
Bill you wrote:
"In fact that is not what raised a red flag for me. I had drilled
down too
far and done a scatter graph with Excel, so every or hundredth or thousandth
was magnified."
far and done a scatter graph with Excel, so every or hundredth or thousandth
was magnified."
Yeah, I wondered if that was part of the problem. Remember, if your input
data is accurate to the nearest tenth of a minute of arc, generally you should
quote your output data to the nearest tenth as well. Anything beyond that is
just random garbage.
And:
"Now that you mention it, I recall a discussion about bodies
of equal observed altitude and the 0.6' minute figure."
of equal observed altitude and the 0.6' minute figure."
Only around 37 degrees separation. Try out those equations from my last
post. When the altitudes are exactly the same, the refraction correction to the
distance in minutes of arc is
1.9*(1-cos(D))/sin(D).
You wrote:
"I apologize to the you and the list for rehashing a subject that was
apparently covered in October."
"I apologize to the you and the list for rehashing a subject that was
apparently covered in October."
You take that back! :-) There is absolutely nothing wrong with
discussing the same topic after a few months off.
And:
"Regarding my question, "Another hypothetical scenario. If I take the
same
two stars, calculate true separation of 34d 27.7', they have identical Hc's
of 1d 36.8', and hypothetical refraction is -88d, what separation might I
expect to measure with a sextant?"
two stars, calculate true separation of 34d 27.7', they have identical Hc's
of 1d 36.8', and hypothetical refraction is -88d, what separation might I
expect to measure with a sextant?"
I didn't respond to this before because I cannot for the life of me figure
out what you're getting at. If you have two stars with an unrefracted distance
of 34 deg 27.7' and you observe them down at 1.5 degrees altitude, then the
measured distance will be very close to 34d 27.7'. What's this "-88d"
number?
-FER
http://www.HistoricalAtlas.com/lunars
-FER
http://www.HistoricalAtlas.com/lunars