Jim Mosher - June 5

Comments from Jim Mosher, June 5, 2007

Regarding your new The-Moon Wiki I also had some comments, but didn't
quite know what to do with them.

Jim - Thanks for your comments! I decided to add a page for discussions like this.

Here they are in somewhat random order:

1. It would be nice to have a single place on the internet where one
could go for current and reliable information about lunar features.

2. In an ideal world, one would be able to get to that place through
the IAU Gazetteer.

3. But the world is not ideal.

4. I am not entirely sure how the new effort is intended to differ from
the excellent and comprehensive collection of articles on lunar
features in the Wikipedia at:

http://en.wikipedia.org/wiki/Category:Geological_features_on_the_Moon

or from the less extensive (Italian language) UAI effort at:

http://www.planetmoon.org/formazioni.htm

I'm not impressed by most crater descriptions anywhere. Frankly, hardly anyone looks at craters with an informed geologic perspective. There are a number of selenographers who could do a better job than me, but they don't choose to spend their time this way! The descriptions in Wikipedia are often simply geographic location info of the sort that used to appear in Moon books. I want to encourage interpretations that explain rather than describe. My poor Italian doesn't allow me to evaluate he UAI site but it doesn't seem to have much info for each crater.

Addition June 6: The Hitchhiker's Guide to the Moon is an earlier effort to build a description of the Moon based on contributions from multiple observers: http://www.shallowsky.com/moon/hitchhiker.html

5. Having multiple sites offering similar information from different
viewpoints might seem good, but it can be confusing; especially if the
information is contradictory and one is not sure which, if any, is the
most current and correct.

I hope that if folks see my name they will have some confidence in what is here.

6. Also, maintaining any one of these is a huge effort, and divides the
attention of those who might want to contribute.

Yes, I have already been questioning the wisdom of starting this wiki! But if nothing else I see it as a place for me to place the notes about various features that I have scattered over various notebooks and Word files and that I add to almost everyday. This may become just my personal repository of various bits of lunar info.

7. A major problem with all the web compilations (and most lunar
books), is that it is difficult or impossible to determine where the
information is coming from. For example, most give (without saying so)
the current official IAU positions of the features, but those values
are often not correct to the implied 0.1 degree accuracy. And 0.1
degree (3 km) accuracy is not sufficient for unambiguous identification
of some of the tinier features named on the Topophotomaps. See, for
example, my example of Alphonsus at:

http://www.flickr.com/photos/ltvt/530675622/

But if one substitutes a more accurate position (2.8W/13.5S) for the
IAU one (3.2W/13.7S), how is the reader to know why the values on one
page differ from those given on another?

Yes, I measured positions of thousands of crater positions in the 60s and early 70s, but I too have noticed that there are some errors in the positions (and diameters) in the IAU catalog. I don't have the energy and interest to address this problem again, but you have demonstrated that serious amateurs using LTVT can determine accurate dimensions and positions!

8. Similarly, values for depths and central peaks are generally given
without any clear description of what they mean or where they came
from. Of the two, central peak heights are less ambiguous (at least
when the crater has a level floor); but there seem to be several
sources, most unreliable. For example, the Wikipedia gives the height
of the central peak in Alphonsus as 1.5 km:

http://en.wikipedia.org/wiki/Alphonsus_(crater)

while your new The-Moon Wiki puts it at 2 km. Neither of these seems
correct to me, and they both seem to be contradicted by the photo used
to illustrate The-Moon Wiki page. See what I think is a correct
measurement at:

http://www.flickr.com/photos/ltvt/530675606/

But if one gave a new shadow-based measurement, how would the reader
know if it is reliable or not?

My value of 2.0 comes from measures I made on Lunar Orbiter prints 35 years ago. I have confidence in them, but am concerned that the Alphonsus peak height may be wrong. In general, the reader doesn't have the info needed to decide. I discussed this in an LPOD and Kurt Fisher has done a great job in reviewing all available topographic measurements in the recent Selenology Today.

9. As to crater depths, I have never quite understood how it is
possible to assign a single number to a complex crater, encompassing
both the height of the rim above the surrounding terrain, and of the
floor relative to that, and the innumerable variations of each (for
example, the east wall of Alphonsus alone, from its shadows, would seem
to vary by more than 1000 m). But I suppose some number is better than
none. Would it be helpful to list the rim height and the rim-to-floor
heights separately; and, where possible, to give the range of each?

For most purposes a single estimate of depth is quite useful. For example, the depth vs diameter relations that Ralph Baldwin, Dick Pike and I have derived helped prove the impact origin of craters. Usually the attempt is made to determine the maximum depth, not the average. Pike did determine average depths from 8 measures on LTOS. Very few people measure rim hts above the surroundings because the hts are small and require very low Sun angles. Dick Pike has collected the best data set for rim hts.

10. A possible web solution to this problem of accountability would be
to turn each piece of numerical information into a hyperlink to a page
explaining where the number came from (or it could be followed by a
footnote like symbol making the link). For example, crater depths
taken from Arthur et al. could all link to a page describing that
article. If the Arthur et al. value were later replaced with a
different one, the new value could link to a page describing the new
source...

Yes, that would be good, but I am too old to spend my time doing that! I want to get as much of my understanding recorded, someone else can deal with the numbers.

11. If another compilation of lunar facts and figures is really
necessary, then regarding The-Moon Wiki specifically:

a. I have not looked in any detail into how the Wiki pages are
written, but it would probably be possible to automatically populate
the initial fields for each feature with the standard IAU information,
with a link to the LPOD Photo Gallery search, and possibly with the
descriptions from Elger. This would avoid misspellings and typos such
as Giordano Bruno --> Giodano Bruno. Would you like help with this?

Yes, when I inputted Bruno I mispelled, and then corrected his name. Unfortunately, everything I do about the Moon is in the evening, after a full day at work. I would be very happy if you could find a way to import data directly into these pages. That sort of computer manipulations is not one of my strengths! Wikispaces does have a capability to link directly to an image on another website, but I haven't seen a way to extract data from a spreadheet.

b. It is not yet clear how you intend to handle the satellite
features. The Wikipedia model, with all the secondary features listed
in a table (which could I suppose link to more detailed sub-pages about
any) seems like a good one; but this doesn't seem to be a part of the
current The-Moon Wiki template. Building some facility for including
secondary features in the template in a uniform way seems quite
important.

Secondary features are secondary and I'm not worried about them right now. Some are interesting and I would describe them in the section where the main crater is described.

c. It would be helpful to translate Elger's English units to metric
and to transpose his outdated convention for east vs. west. Again,
this could probably be automated.

Time, time, time

d. As interesting (historically) as Elger's descriptions may be, his
quantitative information is most likely outdated, incomplete or
misleading; and falls in the category of confusingly contradictory
information mentioned above. Personally, I like the Wikipedia's effort
(at least in theory) to retain only the most current and accurate
numbers and interpretations they know of. But then I like being able
to see what Elger knew...

I like the historic approach. He was a very skilled observer, and often there are not better descriptions of features.

e. The preceding comment notwithstanding, if a historical perspective
is desired, the GLR believes that Wilkins and Moore's /The Moon/ may be
in the public domain (at least as far as its former publishers are
concerned) -- see the notes at the end of:

http://www.glrgroup.org/papers/13.htm

If true, their commentaries might be even more interesting than
Elger's, and could be scanned in without any great difficulty by OCR.
But again, giving too much space to imprecise data and antiquated
interpretations may lessen the impact of the pages.

Interesting about W&M The Moon being in public domain - I hope someone digitizes it and places it online. I don't believe there is much of value in the descriptions in that book, except the historical perspective.

f. It is unclear to me (and probably to most others) how the editing
process for The-Moon Wiki is supposed to work. I assume the proposed
changes are passed through a moderator, rather than allowing items to
be changed willy-nilly by anyone who thinks they have something better.
Are possible errors or inaccuracies supposed to be aired in the
Discussion area for each page? Perhaps a little more introduction
explaining how it works would be helpful.

===Yes, more explanations are needed. But I have only been working on this 3 dyas so have a lot yet to do!
I am not yet comfortable about changes make by anyone. That is why I require registration before allowing folks to make changes. But some malicious person could come and erase everything... The discussion area is availalbe - in Wikipedia there is much useful information there.===

g. When making reference to articles in NASA Ads/Abs, the most concise
syntax I know is:

http://adsabs.harvard.edu/abs/1978JHA.....9..155W

That brings up the page with the abstract and the links to the full
text in various formats; but, of course, even this can be hidden in a
hypertext link so that only a user-friendly name is displayed.

Thanks!

---
 
  These are just some random thoughts. The-Moon Wiki is a very ambitious
  project and I wish you the best of luck with it!
 
  Yours,
 
  Jim
 
 

Thanks, Jim. I know it won't be finished, but - like life - the process may be fun!