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Gliese 581

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:

Crescent Venus, again

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.

Crescent Venus

Just a quickie tonight: Venus is approaching conjunction:

(FZ28, ISO 100, 1/100 sec, f/4.4, full optical zoom of 18x)

If I get a chance to slap the camera on the 100mm scope in the next few days, I will, but Venus is rapidly heading away from the evening sky.


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.

Geek Out!

By request of a friend on Facebook, my entry for Hug an Engineer Day, inspired by the ThinkGeek "Pop Quiz Math Clock", is now outside the Facebook zone:

12.5" Dob out of hibernation and hunting Herschels

I finally took the 12.5" Dobsonian for a spin the evening of March 3, after several months of using only the 100mm refractor (mostly as an astrophotography platform). Since it doesn't have a drive, the Dob's not much use for astrophotos, except of really big, bright things like the Moon:

First quarter moon. 12.5" reflector, 57x, FZ28 1/125 sec at f/4.5

First quarter moon, with a little extra zoom (about 4x) on the camera itself. 12.5" reflector, 57x, FZ28 1/60 sec at f/4.5

More after the break.

Comet C/2007 N3 (Lulin)

A quick image of Comet Lulin from tonight (Feb. 27, 2009):

No, it hasn't pulled a Shoemaker-Levy 9 on us; it's moving so quickly that registering images against the stars leads to multiple comet images. (8 images, ISO 800, 30 seconds each)


This time (Feb. 12), I tried taking a larger number (15-18) of shots just piggybacking the camera at full zoom (18x). At maximum aperture at this zoom, the lens has a clear aperture of about 20mm, so it behaves like a (very!) small 18x telescope. 20mm isn't a lot, but combine it with an exposure equivalent to 3 or 4 minutes, and you can pick up quite a bit. Here's M35, 14 exposures (best 80% of 18 actually processed) of 10 seconds each, ISO 800:

It's not quite as detailed as the digiscoped version I posted a couple of weeks ago, but it's not dramatically inferior either. You can just make out the small cluster NGC 2158. On objects like this, I may try slightly longer exposures (maybe 15-20 seconds) in the future to pick up some additional detail.

Additional images after the break (all using the same stacking and exposure parameters as M35). As usual, I've post-processed these significantly to help bring out fainter stars, and cropped the most interesting portions.

Updates: Tycho-2 database

The Distant Worlds Star Mapper can now use the Tycho-2 catalog for many of its charts. Prepared from the same mission that created the Hipparcos catalog, the Tycho-2 catalog has almost 20 times as many stars as the Hipparcos catalog -- over 2.5 million, including 99% of all stars to magnitude +11, and 90% to magnitude +11.5. Since the core of the Mapper's database was originally the Hipparcos catalog, there is clearly a huge difference. Here are some examples:

M6 + M7, old catalog (to about magnitude +8.5 with occasional fainter stars):

M6 + M7, Tycho-2 version (here limited to magnitude 10, so this is still only a fraction of the stars it can show):

Additional samples after the break.

Latest round of astrophotos

A few more astrophotos, all taken with the FZ28 afocally (through the eyepiece) using the 100mm refractor and a 28mm RKE eyepiece. For all the deep sky objects, I stacked multiple short exposures, using the very handy free tool Deep Sky Stacker, and subtracted dark frames and bias frames to improve contrast. Additionally, I post-processed these to improve contrast overall: this makes an especially big difference on star clusters, where it's often possible to get the background almost black while still clearly showing very faint stars. For reasonably bright deep-sky objects, it doesn't take a particularly long exposure to get interesting results. It works out that a total of 2-4 minutes (corresponding to 8-16 15-second exposures) is often enough. Finally, most of these are resized from the original images, which are much larger.

My favorite is this one of M35 (nine 15 second exposures at ISO 400). If you look closely you can see the small cluster NGC 2158 in the lower right. After tweaking the contrast a bit I was able to resolve a half-dozen or so faint stars in that cluster, which is certainly more than I've ever done visually with this 100mm refractor. In fact, I'm not sure I've ever seen NGC 2158 at all with the 100mm, at least from my somewhat light-polluted backyard. The cluster shows up even better in the raw TIFF file I get after stacking, where there's a faint sprinkling of stars across the cluster background. The whole thing looks rather like the view in a 10" scope I used to have.


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