Occultation of Saturn

I am surprised that there aren't loads of reports on this event today. I
know much of the country was outside the occultation range. In spite of the
earlier cloud it was perfectly clear here in Essex. I have posted some pics
on the planet page of my website (see sig below).
They were taken with a Canon 20Da at prime focus of a Vixen VC200L.

--
Dave Smith
http://www.graviton.demon.co.uk

Dave Smith wrote:
I am surprised that there aren't loads of reports on this event today. I
know much of the country was outside the occultation range. In spite of the
earlier cloud it was perfectly clear here in Essex. I have posted some pics
on the planet page of my website (see sig below).
They were taken with a Canon 20Da at prime focus of a Vixen VC200L.


I have compared the third picture
http://www.graviton.demon.co.uk/imag...rged_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/occulta...single_800.jpg

You can see what I mean at:
http://freenet-homepage.de/AiTI-IT/A...2007-03-02.jpg

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

Am I missing something here?

Claudio Grondi

I happen to like the digital composed results of the following image,
whereas your terrific image is perhaps more true to life, it simply needs
some tender loving PhotoShop in order to crank up the overall contrast.
http://www.digitalsky.org.uk/occulta...ite-single_800.
jpg

Your more natural image of having obtained the moon and Saturn in the very
same FOV exposure is what actually shows best, that one of the sufficient
specks that should have been in the absolutely crystal clear and otherwise
black NASA/Apollo sky, as obtained by an unfiltered EVA Kodak moment, should
have been entirely capable of having included a look-see at having recorded
Saturn.
-
Brad Guth

I have compared the third picture
http://www.graviton.demon.co.uk/imag...rged_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/occulta...single_800.jpg

You can see what I mean at:
http://freenet-homepage.de/AiTI-IT/A...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.

Dave

On Sat, 3 Mar 2007 13:21:54 -0000, "Dave Smith"
wrote:


I have compared the third picture
http://www.graviton.demon.co.uk/imag...rged_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/occulta...single_800.jpg

You can see what I mean at:
http://freenet-homepage.de/AiTI-IT/A...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/occulta...omposite-3.jpg


--
Pete
http://www.digitalsky.org.uk

Pete Lawrence wrote:
On Sat, 3 Mar 2007 13:21:54 -0000, "Dave Smith"
wrote:

I have compared the third picture
http://www.graviton.demon.co.uk/imag...rged_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/occulta...single_800.jpg

You can see what I mean at:
http://freenet-homepage.de/AiTI-IT/A...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/occulta...omposite-3.jpg


Thank you both Pete and Dave for your response.

Now I know what I was missing and some mo

- 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

Also, there's an exposure issue, I suspect. The moon is very
bright.

Pete's image is stunning, but once I read that it was a composite,
I'm afraid some of the magic and awe evaporated. Unless I'm misunderstanding
something and getting the wrong end of the stick, which is entirely
possible.

I'd like to be enlightened as to the nature of the "composite".

Nice work, nevertheless!

While I'm here, since I seldom post here, I was lucky enough on the 6th
of Feb, to see Mercury for the first time. It made me very happy! I've
wanted to see it for ages!


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.livejournal.com/userinfo.bml?user=fleetie

Claudio Grondi wrote:

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
After checking the postings to another (German) astronomy group I found
today a hint to another free astronomy software program called Celestia:
http://www.shatters.net/celestia/

Celestia helps to get better intuitive feeling for the Solar System and
yes, it shows that changing the position when near the Earth has an
impact on the Moon position in relation to other solar system objects
and the stars. The navigation in Celestia is somehow contrary to my
intuitive expectation and I have still a hard time to get it to show me
what I would like to see, so I have started to dream about getting the
features of both Stellarium and Celestia into one software package ...

By the way: I had today an excellent view on the total Lunar Eclipse and
was watching the Moon through binoculars from out of a window and the
Stellarium simulation on the PC in parallel both showing the same
picture. Stellarium is an incredible nice piece of software !!! Thanks
to all who contributed to it and made it available for free.

Claudio Grondi