Retrograde Mars - the scale (APOD 11 May 2008)

[henk21cm]

The scale of todays picture is large, it is a wide field image. It spans from RA 4h till 8h30m and form δ 45 till 15° i.e. from right top to left bottom.

1. The bright star in the top of the image is Capella, α Aurigae. The bright star near the rightmost part of the retrogade loop is Elnath, β Aurigae.
2. The bright star in the left bottom corner is Procyon, α Canis minoris.
3. The red star bottom, middle of the image is Betelgeuse, α Orionis, the blue star slightly to the right of Beteulgeuse is Bellatrix, γ Orionis.
4. The red star, utmost right, center height of the image, under the start of Mars' trail is Aldebaran, α Tauri.
5. Left side of the image, 2/3 of the height of the image are of course Castor (top) and Pollux (lower), α and β Geminorum, as described in yesterdays APOD.
6. Between in the start of Mars' path and under center part of the retrogade loop the Crab nebula must be hidden somewhere. Also known as Messiers M1, it must have been the brightest nebulae in the sky, but i have never seen it with my own eyes, with binoculars or a small telescope.

[Case]

The Crab Nebula is almost invisible in the image, just four faint pixels.
(The red oval shape indicates the position, not the size.)

[apodman]

The crab nebula has a great name, and its picture is familiar from all the books. So there is a temptation to go look at it. But beginning observers, people with small telescopes, and the majority of us who live with light pollution should observe easier objects first lest we become discouraged. That's my experience, anyway. As I recall, it is not even a "fuzzy object", more like "wispy".

A number of years ago, there was some sort of movement to get street lights and other city lights to face down to light the earth, not up to face the sky. By my unscientific survey of my locale, there are downward-shielded street lights here and there but no overall improvement. Somebody needs to beat the drum more persistently on this one.

[orin stepanek]

The retrograde from 2 years ago made a little different pattern in the sky! More of a Z pattern. This one is more of a loop.

http://apod.nasa.gov/apod/ap060422.html

http://apod.nasa.gov/apod/ap080511.html

Evidently the planets are aligned a little different in the ecliptic plane from year to year. Though I don't know if this of and significance.
Orin

[Indigo_Sunrise]

That's a really cool observation - thanks for pointing that out! 8)

[iamlucky13]

The planets all have slightly different tilts, but even without that, the orbits are out of sync. I suppose the difference is related to what point the planets are in the orbits at the various points in the analema...when they on the "upward" part of their travels versus "downward."

I don't think it's any major significance, but it was a very good catch on your part. I remember that picture now that you point it out.

[orin stepanek]

I wonder if there is a pattern after a few cycles or if the retrograde looks different each and every time that the Earth catches and passes Mars? Maybe I can find some older retrograde pictures.
Orin

[bystander]

APOD: 2003 Dec 16 - Retrograde Mars

[orin stepanek]

APOD: 2003 Dec 16 - Retrograde Mars

Thanks bystander! I found this animation that I thought was interesting. I shows how retrograde works. 8) http://www.lasalle.edu/~smithsc/Astrono ... ograd.html
Orin