Starship Asterisk*

Northward, Northern, Southward, and Southern are fine for those who already understand what you mean by them, but are likely to befuddle those who don't, and would be ambiguous for those who aren't sure if you're talking about the movement of the Earth's noontime equator relative to the ecliptic or...

Lovely APOD. As others noted when this video was first submitted, the green patches appear to coincide with the tide rolling in. It was suggested that the green patches were from bioluminescent algae churned up by the tide, and reflected onto the clouds. This sounds most plausible. Having said that,...

March Equinox, June Solstice, September Equinox, December Solstice. Unambiguous and requires no knowledge of which direction the Sun appears to be moving or where the Sun appears to be standing still. Indeed they require no knowledge of the Sun. Nor do they add any. I also prefer Northern and South...

geckzilla wrote:Your statement was definitely worded confusingly enough for me to think you meant global warming was as dangerous as education of women.

I agree that it was not written clearly, but that's the way I like my "wild speculation" rants. Sorry for the confusion.

I just realized my minor mistake... It IS the northern hemisphere's autumnal equinox, as well as the southern hemisphere's vernal equinox. It's the Whole Earth's equinox. :oops: You would think that they would have come up with better names by now. These are the preferred terms for we upside-down p...

geckzilla wrote:Just what are you trying to say, here?!

Merely that in many of the wealthier nations of the world, the education of women has proven to be a good way to approach ZPG. Or at least there appears to be a demographic correlation. It certainly sounds reasonable to me.

Yes, after I read the story of van Maanen linked in my last , it dawned on me that my guess was a bad one.

I shall go and sit in the corner for a few days.

[wild speculation] Not that I'm looking forward to it, but the climate change predicted within this century, and beyond, might be the only thing (apart from the widespread education of women, which is strongly correlated with wealth, which is strongly correlated with energy usage [damn it]) which ha...

APOD Robot wrote:the picture demonstrates a stunning range of vision

Indeed, very striking. Evocative of fractals and midnight swims.

I do believe theTönster is right. I also believe theTönster didn't bother to read the previous posts in this topic.

But don't believe me (really don't, I speculate far too much), this article would seem to be more enlightening:

http://en.wikipedia.org/wiki/Adriaan_van_Maanen

At a guess, it is perhaps "Annual Proper Motion in arc seconds" as measured from the centre of M81, not as measured from our sky.

I've never heard of Proper Motion being relative to anything other than the Solar System, but things may have been different in 1921.

Ann, thanks for the link to that CFA article. It has left me thinking that it really is too complicated to try and describe in a few sentences. From now on, I resolve to refrain from such attempts. I have a (distant) background in computational fluid dynamics, and one of the difficulties encountered...

According to the theory of geosynchronous orbits, I should be able to photograph the same portion of sky every sidereal day and re-observe the streak.

Not that I am surprised, but I attempted this last night and failed. Some theory!

I should point out that M81 is 12 Mly away such that 0.1 arcsec ~ 6 lyr. Therefore Adriaan van Maanen was "observing" relativistic orbital proper motions ... In other words, it is only the length of the cyan-coloured arrows that is related to the cyan-coloured scale bar. M81 itself appear...

Neufer, that diagram of concentric, twisted ellipses is also very informative, thanks. And hats off to C.C. Lin and Frank Shu.

Thanks for the education: neufer, Anthony and alter-ego. I especially like the explanation of leading/trailing and front/back. As someone who is inclined towards a mathematical understanding of things, but who is otherwise quite ignorant of how gravitational forces create and maintain spiral galaxie...

Assuming a geosynchronous satellite, my rough (and possibly wrong) calculations would put it at a longitude of E114, oscillating over Western Australia, Indonesia and Hong Kong.

Not sure if that helps, but I hope it does.

Much appreciated.

Oh I'm tired of it. I'm always time travelling. Forwards. At the speed of time. You'd be surprised how dull it can be.

One thing I've overlooked :oops: ... My scope would have been moving westwards at about 15 arcmin per minute. Relative to a fixed Alt/Az, the speed of the object would be closer to 15 arcmin per minute. This increases the probability of it being a geosynchronous satellite. It also increases its nort...

Is there a list of classified satellites or is that not allowed? Maybe on wikileaks ... I've never checked, as I don't like being watched. ... I'm a newbie at this astrophotography hobby, and in the few months since I started taking shots like this (moon size frame and 30s exposure), I must have ta...

Oh, I'd be very surprised if it isn't a satellite. I'm hoping someone can help me identify which one.

To my inexperienced eye, this object seems too fast for geosynchronous orbit and too slow for LEO. That would narrow it down to a MEO (probably).

But which one?

The object appears to be moving predominantly eastwards, meaning that if it is geosynchronous (and I understand correctly) it must be close to its southern extreme on its daily analemma. From my southern hemisphere location, geostationary satellites appear about 4.5 degrees North of the Celestial Eq...

Thanks Chris, but I measure it to be almost 30 arcmin per minute. (The ~30 second gap between streaks was me being lazy and wasting sky time, by setting the camera to take intermediate dark frames and automatically subtracting them from the open frames. Silly me.) (Having said that, it doesn't convi...