As you may know, people first figured out distances to the stars by measuring parallax shifts coming from the Earth's orbit. You may be wondering, though: given how far away the stars are, just what does this look like?
The first reliable measurements didn't come until the 1830s, over two centuries after the invention of the telescope and long after the discovery of Uranus, all the Messier objects, many faint planetary satellites, and subtle planetary details. As you can imagine, it's a fairly small effect that's difficult to detect. How small? More below the break.
When I haven't had time (or clear skies) to go observing the actual universe, I've been working on some ways to explore the virtual universe. A few years ago, I designed a basic starchart maker for this site that contains the entire Hipparcos catalog, so it could be used to show the sky from any location within a few hundred light years from Earth. I also found a bunch of stellar velocity data a while back, so for the brighter stars at least, I've been able to run simulations in time as well as space.
By creating a whole bunch of related images, I've created a number of animations illustrating various ideas from amateur astronomy, astrophysics, and even human archaeology and history. I'll begin with a short trip (in time, at least) to the Hyades, the closest large open cluster to Earth, right below the break:
I haven't been posting a lot lately, largely because a lot of the really quick updates go on Facebook these days. Despite all this, I've been doing a reasonable amount of observing lately. A few weeks ago I had an especially clear night where I could just see the largest dust lane in M31, the Andromeda Galaxy, in the 12.5" scope from the back yard. That was the first time in quite a while I remember doing that.
Here's an image from three days ago (June 29, 2009). This is a full-sized crop of the original. I've tweaked the image slightly (grayscaling to improve chromatic aberration, and a touch of unsharp masking), but the effects are cosmetic; you can still see the same details in the original. The smallest craters clearly visible near the terminator are less than 10 km across: for example, you can see Hyginus A, at 8 km, and it's clearly more than just a couple of pixels). Not bad for a $250 optical tube and a $250 compact non-DSLR camera. It's definitely better than the first few views of the Moon I got through a $3000 telescope 25 years ago!
It's been a quiet few months thanks to rainy weather here in northern Colorado.
June 29 was the first day in 3 months that I got more than a quick look at the sky. As a result, it was more of a "summer showpiece" sort of night, full of big bright things like the 1st-quarter Moon, globulars like M13 and M3, and bright nebulas like M57 and M27.
Saturn, which I'd hoped to observe more in the spring, is finally on its way out; I saw it briefly, but only very low, with already poor seeing made worse by the altitude. I was hard pressed to see any moons besides Titan and Rhea, and no details on the disk itself.
I did get a few quick photos through the 100mm refractor:
Gliese 581 is back in the news, since it apparently has a medium-sized planet in its habitable zone. We have no way of knowing yet if it actually supports life, but if there are intelligent beings there, and they look in the general direction of Orion, they'll notice that one star is peculiarly radio-noisy:
Finally got a few shots in the 100mm scope (24x telescope magnification, time: 1/100 sec. at f/4.5, approximately 10x zoom on the camera itself). Each of these was reduced in size by a factor of 4, whereas last night's image is a 100% crop. The larger image scale does make it clearer just how thin the crescent really is. Unfortunately, Venus was very low and so the seeing was rather poor; the final image quality isn't a whole lot better than with just the camera itself.
Last night, I spent all my observing time on Saturn with the 12.5" Dob, mostly with a 7mm Nagler (227x). This year, the rings are edge-on or very close to it. At the moment, they have opened up slightly, so I could just barely see the (normally very prominent!) dark space between rings and planet. There was a subtle darkening across the planet where the rings crossed; I'm not entirely sure whether it was ring shadow, a cloud band, or both.