Re: Occultation of Saturn

Pete Lawrence wrote:
On Sat, 3 Mar 2007 13:21:54 -0000, "Dave Smith"
<dave@xxxxxxxxxxxxxxxxxxxx> wrote:

I have compared the third picture
http://www.graviton.demon.co.uk/images/emerged_2270s.jpg
available from the page:
http://www.graviton.demon.co.uk/planets.htm

with the composite one done by Pete:

http://www.digitalsky.org.uk/occultations/occultation-composite-single_800.jpg

You can see what I mean at:
http://freenet-homepage.de/AiTI-IT/Astronomy/LunarOccultationOfSaturn_2007-03-02.jpg

How does it come, that the moon surface appears so different?

Am I missing something here?

Claudio Grondi
Hi Claudio

That is very interesting. I strongly suspect that the difference in Moon position is due to the difference in location between Maldon, Essex where I took my picture and Selsey where Pete took his. Pete I believe, from his location did not see Saturn totally disappear whereas from Maldon it disappeared for nearly half an hour. Even though the relative position of Saturn compared with the Moon will not be great, as it is a grazing or near grazing event then the position on the Moon's surface where it appears and reappears will be quite sensitive to location. E.g. For Pete in Selsey there is only one position on the Moon's surface where Saturn will be at its closest. From Maldon the entry position and exit position were quite different.

Well spotted.

This is what it did for me...

http://www.digitalsky.org.uk/occultations/occultation-composite-3.jpg


Thank you both Pete and Dave for your response.

Now I know what I was missing and some more:

- first I haven't took the position on Earth from which the shots were made into consideration - I made a comparison between two different perspectives what was just not appropriate.
- the next problem I have run into is, that I have not looked at the time at which the pictures were made I have compared - Pete's was made at 2:52 and Dave's at 2:59 - I just assumed, that same position of Saturn in relation to the Moon means, that the pictures were taken at the same time ...

Now, after I got aware what was wrong with my comparison, I realized, that in fact I should know about such effects from what I know about solar eclipse events. I have to admit, that I am very surprised, that the effect could be so significant already for so small differences of locations within England as between Selsey (West Sussex) and Maldon (Essex), so I assume, that most of the effect was caused by the 7 minutes time difference between the shots and not by the difference in locations.

I suppose I have to dig much deeper into it in order to get a better feeling for such things, as I have to admit, that my intuition still resist to accept the given explanation.
Could it be, that the same piece of surface of the moon can look very different on different pictures depending on some other factors I am still not aware of?

What I have learned from this lesson?

Pictures of objects in relation to the Moon should contain beside the date, time also the exact location from which the picture was made in order to be useful for comparison purposes.

I expect, that this is exceptional to pictures involving the Moon, as I suppose, that the position on Earth from which a picture was made doesn't have a significant effect on pictures of solar system planets (and their moons) even if there is maybe a very slight effect on their position relative to the stars.

I have googled for 3D models of solar system helping me to adjust my intuitive expectations to the reality, but the best I came up with yet is the magnification feature in Stellarium. This helps much, but it does not show enough Moon surface details (yes, I was able to watch the occultation of Saturn in Stellarium).
Is it possible to have a much more detailed Moon surface in Stellarium and if yes how can this be achieved?

Claudio Grondi
.

Relevant Pages

  • Re: revisiting Apollo
    ... Tim listen, I have watched the documentary with interest along with my ... that the moon footage shown to the world as real was in fact hoaxed on ... Are you suggesting the CBC ... Moon landing pictures which inspired the world, ...
    (sci.astro)
  • Re: Moon pix - what are these streaks ?
    ... experience make the pictures blurry. ... not blending with the curvature of the moon. ... Sony digital that produces rather objectionable artifacts anywhere there ... If you are using your camera's "digital zoom" to get ...
    (rec.photo.digital)
  • Re: Query for Brad Guth
    ... island of NASA's Apollo moon looked like. ... pictures of the Moon with shutter speed at normal day time rates -- ... of blue light in it, and video camers can pick that up. ...
    (sci.space.history)
  • Re: How do I create a mosaic image?
    ... >Thanks Pete and Norbert. ... >have the problem of the moon drifting across the screen slowly. ... rough alignment will be fine. ... The closer to perfection you get the ...
    (uk.sci.astronomy)
  • Re: Who wanted the moondog?
    ... >>Pete Lawrence Wrote: ... >>> moondogs. ... it passes the time waiting ... > need the Moon out of the way. ...
    (uk.sci.astronomy)