Analemma at Ancient Nemea ... #3/11

Brian Tung wrote:

By the way, I'm putting together an animated GIF of the lunar analemma--
a lunalemma, if you like--using PleiadAtlas. It turns out that the time
I chose (early 2000) doesn't produce a very nice shape, so I'm hunting
down a better one that will still fit in one screen. When I do, I'll
put it on my web site, if people are interested.

This is something I looked into as well, for it is an obvious
extension of the (solar) analemma. I would be most interested in seeing
your results, when available, for I would like to pursue a real-live
example at some point.

There are other analemmas people could produce, that don't take anywhere
near a year long, incidentally. A geosynchronous satellite with a modest

My next step in the analemma project is to pursue the imaging at
the equator and to do so in early morning (around 07:30 AM) where we
have the figure-8 basically horizontal with one half of each loop below
the horizon and the other half above the horizon. With respect to
duration, it will require around eight months - 2.5 months for one loop
and four months for the other loop - with a break of about 2.5 months
between sessions. I was looking at potential sites along the equator for
the pursuit of such a project and there around 12-15 candidate countries
and none very appealing.

eccentricity and inclination to the equator will produce at least part of

Using a geosat will be a problem since these beasts are quite dim
in brightness (around 11-12 mag).

a good analemma. One taken during polar winter from within the Arctic
or Antarctic circles would be complete and would make a good composition.

Being someone who hates cold weather, thanks but no thanks! :-)

Anthony.


Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Anthony Ayiomamitis wrote:
This is something I looked into as well, for it is an obvious
extension of the (solar) analemma. I would be most interested in seeing
your results, when available, for I would like to pursue a real-live
example at some point.

OK. The one problem with a live case is that the Moon would be out
in the daytime roughly half the time, and the Sun might interfere.

Using a geosat will be a problem since these beasts are quite dim
in brightness (around 11-12 mag).

I don't think they're quite that dim--not all of them--but it's true
that I haven't seen any brighter than about magnitude 7 or so.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Brian Tung wrote:

Anthony Ayiomamitis wrote:


This is something I looked into as well, for it is an obvious
extension of the (solar) analemma. I would be most interested in seeing
your results, when available, for I would like to pursue a real-live
example at some point.



OK. The one problem with a live case is that the Moon would be out
in the daytime roughly half the time, and the Sun might interfere.

The range in azimuth also is huge and would probably require a 180-deg
fisheye lens. For my analemmas, the greatest range in azimuth is easily
manageable with a 24-35mm lens for both azimuth and altitude.

For the moon, I looked into it last year ... what I thought of doing was
to approach it in reverse by identifying the time closest to early
morning twilight and starting from there. Going on the generalization
that the moon rises by about 52 minutes later each succeeding day, I
should be constructing a "curve" from the top right of my camera's FOV
moving slowly towards the bottom left corner (gross generalization here)
with intervening daily phases in-between being captured on the single frame.

Using a geosat will be a problem since these beasts are quite dim
in brightness (around 11-12 mag).



I don't think they're quite that dim--not all of them--but it's true
that I haven't seen any brighter than about magnitude 7 or so.

The optimal time to view geosats is around the equinoxes when favourable
geometry with the sun gets them down to around 5th magnitude. Otherwise,
they are generally 11th magnitude and dimmer thanks to their orbit at
38000 km.

Anthony.


Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Anthony Ayiomamitis wrote:
The range in azimuth also is huge and would probably require a 180-deg
fisheye lens. For my analemmas, the greatest range in azimuth is easily
manageable with a 24-35mm lens for both azimuth and altitude.

For the lunalemma? No, the range in azimuth is certainly not large.
It's not much more than is required for an ordinary analemma--possibly
less.

The problem is that you have to take your images spaced at regular
intervals of about 24 hours 50-1/2 minutes. Depending on when you
take it, the analemma can be as short as about 37 degrees and as tall
as 47 degrees in declination. I haven't measured the range of right
ascension widths, but I suspect the whole thing will fit into no more
than about 2 or 3 hours of RA, most of the time. Certainly the one I
simulated last night fit in that short space.

As I said, though, half of the images will be daytime, and probably
crescents. It won't be easy, for technical reasons.

The optimal time to view geosats is around the equinoxes when favourable
geometry with the sun gets them down to around 5th magnitude. Otherwise,
they are generally 11th magnitude and dimmer thanks to their orbit at
38000 km.

Ahh, I see.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt