Difference between revisions of "October 25, 2004"

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    <tr><td><div align="center" class="main_sm">Image Credit: [mailto:gibbidomine@libero.it Raffaello Lena] and Cristian Fattinnanzi, Fabio Lottero and KC Pau
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<tr><td><div align="center" class="main_sm">Image Credit: [mailto:gibbidomine@libero.it Raffaello Lena] and Cristian Fattinnanzi, Fabio Lottero and KC Pau
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<p align="center"><b>Modeling Domes</b></p>
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<p align="center"><b>Modeling Domes</b></p>
<p align="left">Domes are one of the most difficult types of lunar objects to study quantitatively. Craters can have their diameters and depths measured fairly directly, but domes are such low and gently sloped features that it is very difficult to measure accurately their shadow lengths to derive topographic information. Members of the Geological Lunar Research Group have developed another way to approach this problem. They have mathematically investigated the relationship between how an ideal hemispherical dome's shadow length (R) varies with solar elevation and with its diameter (D) and height (H) ratio. The bottom part of the illustration shows the computed shadow lengths for various dome D/H ratios (and resulting slopes) against increasing solar elevation (alpha). The graph passes the common sense test - it shows that steep domes (D/H = 10) cast longer shadows and cast them at higher sun angles than low angle domes (D/H = 80). With this table you can estimate (or measure) which D/H value most matches a real dome. For the example of Milichius Pi (in the small excerpt from a KC Pau image taken when the sun was 1.2 degrees above Pi), the best fit is for D/H = 40, yielding a dome slope of 2.9 degrees and a height of about 200 m.</p>
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<p align="left">Domes are one of the most difficult types of lunar objects to study quantitatively. Craters can have their diameters and depths measured fairly directly, but domes are such low and gently sloped features that it is very difficult to measure accurately their shadow lengths to derive topographic information. Members of the Geological Lunar Research Group have developed another way to approach this problem. They have mathematically investigated the relationship between how an ideal hemispherical dome's shadow length (R) varies with solar elevation and with its diameter (D) and height (H) ratio. The bottom part of the illustration shows the computed shadow lengths for various dome D/H ratios (and resulting slopes) against increasing solar elevation (alpha). The graph passes the common sense test - it shows that steep domes (D/H = 10) cast longer shadows and cast them at higher sun angles than low angle domes (D/H = 80). With this table you can estimate (or measure) which D/H value most matches a real dome. For the example of Milichius Pi (in the small excerpt from a KC Pau image taken when the sun was 1.2 degrees above Pi), the best fit is for D/H = 40, yielding a dome slope of 2.9 degrees and a height of about 200 m.</p>
<blockquote><p align="right">&#8212; [mailto:chuck@observingthesky.org Chuck Wood]</blockquote>
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<blockquote><p align="right">&#8212; [mailto:tychocrater@yahoo.com Chuck Wood]</blockquote>
 
<p align="left"><p><b>Related Links:</b><br>
 
<p align="left"><p><b>Related Links:</b><br>
 
[http://www.glrgroup.org/news/18.htm GLR Group]
 
[http://www.glrgroup.org/news/18.htm GLR Group]
 
<br>[http://www.glrgroup.org/domes/artificialdome.htm Lunar Domes and Artificial Domes: Two Tools for Lunar Observers (also published in <i>Selenology</i> vol 23 n.2; 2004)]
 
<br>[http://www.glrgroup.org/domes/artificialdome.htm Lunar Domes and Artificial Domes: Two Tools for Lunar Observers (also published in <i>Selenology</i> vol 23 n.2; 2004)]
 
<p align="left"><b>Tomorrow's LPOD: </b> Eclipse Preview</p>
 
<p align="left"><b>Tomorrow's LPOD: </b> Eclipse Preview</p>
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<p align="center" class="main_titles"><b>Author &amp; Editor:</b><br>  
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<p align="center" class="main_titles"><b>Author &amp; Editor:</b><br>  
[mailto:chuck@observingthesky.org Charles A. Wood]</p>
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[mailto:tychocrater@yahoo.com Charles A. Wood]</p>
<p align="center" class="main_titles"><b>Technical Consultant:</b><br>
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<p align="center" class="main_titles"><b>Technical Consultant:</b><br>
[mailto:anthony@perseus.gr Anthony Ayiomamitis]</p>
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[mailto:anthony@perseus.gr Anthony Ayiomamitis]</p>
<p align="center" class="main_titles"><b>Contact Translator:</b><br>
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<p align="center" class="main_titles"><b>Contact Translator:</b><br>
[mailto:pablolonnie@yahoo.com.mx" class="one Pablo Lonnie Pacheco Railey]  (Es)<br>
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[mailto:pablolonnie@yahoo.com.mx" class="one Pablo Lonnie Pacheco Railey]  (Es)<br>
[mailto:chlegrand@free.fr" class="one Christian Legrand] (Fr)</p>
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[mailto:chlegrand@free.fr" class="one Christian Legrand] (Fr)</p>
<p align="center" class="main_titles"><b>[mailto:webuser@observingthesky.org Contact Webmaster]</b></p>
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<p align="center" class="main_titles"><b>[mailto:webuser@observingthesky.org Contact Webmaster]</b></p>
<p align="center" class="main_titles"><b>A service of:</b><br>
+
<p align="center" class="main_titles"><b>A service of:</b><br>
[http://www.observingthesky.org/" class="one ObservingTheSky.Org]</p>
+
[http://www.observingthesky.org/" class="one ObservingTheSky.Org]</p>
<p align="center" class="main_titles"><b>Visit these other PODs:</b> <br>
+
<p align="center" class="main_titles"><b>Visit these other PODs:</b> <br>
[http://antwrp.gsfc.nasa.gov/apod/astropix.html" class="one Astronomy] | [http://www.msss.com/" class="one Mars] | [http://epod.usra.edu/" class="one Earth]</p>
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[http://antwrp.gsfc.nasa.gov/apod/astropix.html" class="one Astronomy] | [http://www.msss.com/" class="one Mars] | [http://epod.usra.edu/" class="one Earth]</p>
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<p>&nbsp;</p>
 
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===COMMENTS?===  
 
===COMMENTS?===  
 
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Revision as of 18:26, 4 January 2015

Modeling Domes

<nobr>Modeling Domes</nobr>

<img src="archive/2004/10/images/LPOD-2004-10-25.jpeg" border="0">

Image Credit: Raffaello Lena and Cristian Fattinnanzi, Fabio Lottero and KC Pau


Modeling Domes

Domes are one of the most difficult types of lunar objects to study quantitatively. Craters can have their diameters and depths measured fairly directly, but domes are such low and gently sloped features that it is very difficult to measure accurately their shadow lengths to derive topographic information. Members of the Geological Lunar Research Group have developed another way to approach this problem. They have mathematically investigated the relationship between how an ideal hemispherical dome's shadow length (R) varies with solar elevation and with its diameter (D) and height (H) ratio. The bottom part of the illustration shows the computed shadow lengths for various dome D/H ratios (and resulting slopes) against increasing solar elevation (alpha). The graph passes the common sense test - it shows that steep domes (D/H = 10) cast longer shadows and cast them at higher sun angles than low angle domes (D/H = 80). With this table you can estimate (or measure) which D/H value most matches a real dome. For the example of Milichius Pi (in the small excerpt from a KC Pau image taken when the sun was 1.2 degrees above Pi), the best fit is for D/H = 40, yielding a dome slope of 2.9 degrees and a height of about 200 m.

Chuck Wood

Related Links:
GLR Group
Lunar Domes and Artificial Domes: Two Tools for Lunar Observers (also published in Selenology vol 23 n.2; 2004)

Tomorrow's LPOD: Eclipse Preview



Author & Editor:
Charles A. Wood

Technical Consultant:
Anthony Ayiomamitis

Contact Translator:
" class="one Pablo Lonnie Pacheco Railey (Es)
" class="one Christian Legrand (Fr)

Contact Webmaster

A service of:
" class="one ObservingTheSky.Org

Visit these other PODs:
" class="one Astronomy | " class="one Mars | " class="one Earth

 


COMMENTS?

Click on this icon File:PostIcon.jpg at the upper right to post a comment.