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Date: 16 Aug 2006 22:23:33
From: canopus56
Subject: How to prepare a blank for planetary sketching with a terminator
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http://members.csolutions.net/fisherka/astronote/plan/skblnk/SketchPlanetBlanks.html
This is to announce a webpage that discusses the procedure for drafting
the position of a terminator on a blank for planetary sketching either
using a common Microsoft Windows tool (MS-Paint) and a Microsoft Office
tool (MS Picture Manager) and by hand. The sketch blanks approximate
the outline of the body and terminator that will be seen in a direct
view eyepiece of a telescope tracking on an equatorial mount and where
a reticule is used to indicate the direction to the celestial north
pole (NCP). The terminator is pre-drafted based on a target observing
date and time from ephemeris data.
The hand-drawing method updpates a procedure after Sidgwick, J.B. 1971.
Observational Astronomy for Amateurs. Dover. pp. 121-124.
One problem I had with this project was finding the correct
mathematical formula to approximate the ellipsis of the terminator
using the radius of circle after Sidgwick's method. If any math types
out there have any suggestions for improving the following lookup table
it would be appreciated. See -
http://members.csolutions.net/fisherka/astronote/plan/skblnk/SketchPlanetBlanks.html#TerminatorRadiiTable
This is an amateur webdoc. Corrections to any errors are welcomed and
appreciated.
- Canopus56
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Date: 17 Aug 2006 16:38:51
From: canopus56
Subject: Re: How to prepare a blank for planetary sketching with a terminator
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canopus56 wrote:
> http://members.csolutions.net/fisherka/astronote/plan/skblnk/SketchPlanetBlanks.html
<snip all >
I have updated this site also showing how to draw an oriented equator
for a planet or the Sun using drawing a solar sketch blank as an
example.
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Date: 17 Aug 2006 10:26:28
From: oriel36
Subject: Re: How to prepare a blank for planetary sketching with a terminator
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The rate of change in orbital orientation of the Earth is consistent
with Keplerian geometry and motion,what you call the 'terminator' is a
ill-considered and childish phrasing of the demarcation between direct
radiation and the orbital sdaow which does not receive radiation.
It is vital to get this right for climatological purposes
notwithstanding that almost all here are astrophotographers,there may
be at least one person with a grasp of the issues involved as orbital
orientation passes over axial orientation in generating climate norms
first and hemispherical weather patterns as an extension.
Keep things local for goodness sake and drop the silly notion of a
variable tilting Earth to the Sun for it shows that you have no
appreciation for the power output of our parent star -
http://upload.wikimedia.org/wikipedia/en/a/a3/Seasonearth.png
If there is some perverse satisfaction in keeping the Earth fixed to
Polaris and allowing it to vary its tilt against the Sun,it shows just
how poor the situation is with climate studies must be.The chances are
that few have the neccessary intelligence to detach themselves from
celestial sphere geometry and approach the matter locally using the
Earth's independent axial and orbital motions and orientations.
Terminator indeed !
canopus56 wrote:
> http://members.csolutions.net/fisherka/astronote/plan/skblnk/SketchPlanetBlanks.html
>
> This is to announce a webpage that discusses the procedure for drafting
> the position of a terminator on a blank for planetary sketching either
> using a common Microsoft Windows tool (MS-Paint) and a Microsoft Office
> tool (MS Picture Manager) and by hand. The sketch blanks approximate
> the outline of the body and terminator that will be seen in a direct
> view eyepiece of a telescope tracking on an equatorial mount and where
> a reticule is used to indicate the direction to the celestial north
> pole (NCP). The terminator is pre-drafted based on a target observing
> date and time from ephemeris data.
>
> The hand-drawing method updpates a procedure after Sidgwick, J.B. 1971.
> Observational Astronomy for Amateurs. Dover. pp. 121-124.
>
> One problem I had with this project was finding the correct
> mathematical formula to approximate the ellipsis of the terminator
> using the radius of circle after Sidgwick's method. If any math types
> out there have any suggestions for improving the following lookup table
> it would be appreciated. See -
>
> http://members.csolutions.net/fisherka/astronote/plan/skblnk/SketchPlanetBlanks.html#TerminatorRadiiTable
>
> This is an amateur webdoc. Corrections to any errors are welcomed and
> appreciated.
>
> - Canopus56
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