The Astronomy Nexus

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.

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.

I recently got a digiscoping adapter for my small scope (100mm f/6 refractor) and camera (Panasonic Lumix FZ28), so now I can take pictures through the scope itself. The adapter just holds the camera in place right next to the eyepiece, making long exposures practical. I've found that with my particular camera, telescope, and eyepieces, the images do vignette noticeably, so this is most useful at low powers or for small objects where the narrow field of view doesn't matter so much. I took all of these shots with a 28mm Edmund RKE (21x), which has the largest eye relief and least vignetting of all my eyepieces. In most cases I used little to no zoom on the camera itself (between 1x and 2x), but in one case I used just over 10x.

Here's my favorite image so far: the central portion of the Orion Nebula (M42).

And I have a few more below:

I recently got a superzoom compact camera (a Panasonic Lumix FZ28) for all-purpose, mostly casual photography. Since it's a compact with a fixed lens, it's not really possible to do conventional (e.g. prime focus) imaging with it. Additionally, like most compacts, it has a fairly small sensor, so getting it to work well in low-light conditions is a challenge (let's just say that I had to take a crash course in "Manual" mode, right from the start). Despite all this, it has worked surprisingly well for piggyback shots using my 100mm equatorially mounted refractor as a platform.

The large maximum zoom (18 x) helps a great deal. Many well-known deep-sky objects show significant detail at this magnification. Additionally, compared to many other superzoom compacts, the FZ-28 has a fairly wide aperture (f/4.4) at full zoom, which comes in very handy. Star clusters, in particular, turn out well: I routinely find 11th, and sometimes 12th, magnitude stars on medium-length exposures (around 15 seconds) at full zoom and low (100-200) ISO. This compares favorably with the view in the 100mm scope itself at low to medium power.

Here are some images that came out fairly well. In each case I cropped the most interesting portion a bit, shrank the image as a whole, and adjusted the brightness and contrast slightly.

This is the Orion Nebula at full zoom, using just the camera's own lens.

I know, this place has been almost dead for months. Unfortunately, life has intervened a lot lately -- however, I expect to be doing a lot more observing the next few months. In the meantime, I updated everything to the current version of the CMS I use. Yeah, I know -- the theme is an ugly default theme. I'm working on it.

I've added a few new features to the site.

Distant Worlds Star Mapper: There are several new enhancements. Major ones include:

a: Chart settings

1. Show R.A. and dec. lines: For locations near the Earth (within 32 light years), you can toggle a grid of equatorial (right ascension and declination) coordinate lines on or off.
2. Show constellation boundaries: Also for locations near the Earth, you can toggle constellation boundaries on or off. These are the official boundaries you see in star atlases.
3. Abbreviate Bayer/Flamsteed designations: Choosing this option will remove the constellation abbreviation from any label that has a Bayer (Greek) letter or a Flamsteed number. For example, α Dra would become simply α and 61 Cyg would become 61. This is best used with constellation boundaries, so it's clear which constellation the abbreviated labels apply to.
4. Show all Bayer designations: Choosing this option will override the usual magnitude display limit and force all stars on the chart with a Bayer or Flamsteed label to display it, regardless of magnitude. The magnitude display limit will still apply to stars with a different designation, such as a proper name or a catalog number such as Hipparcos or Gliese numbers.

   Selecting all 4 of the options above will produce a view very similar to a chart out of a major star atlas.

5. Identify Sunlike stars: This will place a small yellow cross around every star that meets the primary criteria for the Encyclopedia of Suns: spectral type V, luminosity 0.1 to 3.0 times solar, and no obvious spectral peculiarities. As usual, hover your mouse pointer over the star to get additional details.

Additional features after the break:

Expected tonight: a lunar eclipse. Actually seen: your basic, unlovely nebular occultation, at least from my back yard. In fact, for much of the night it wasn't obvious that anything unusual was going on, except through the occasional break in the clouds. Fortunately, one member of my local astro club, Brian Kimball, did get a nice picture through some light clouds.

(h/t Bad Astronomer)

17th to 3rd magnitude in less than 24 hours!

I've made a few more changes to the Distant Worlds Star Mapper. The big ones are:

• Most stars now show single Greek letters instead of the English names for the letters (e.g. α instead of "Alpha", and π instead of "Pi"). This should make the chart labels less cluttered.
• The pop-up details for individual stars show more information, including proper name, catalog designations, spectral tyes, and absolute magnitudes.
• The charts now include the standard constellation boundaries. These only appear for locations reasonably close to the Sun (within about 15 light years), because at large distances the Earthly constellation names and boundaries are pretty meaningless.

I've updated the software behind the site overnight. One big change: you don't need to register to post or view comments. However, every comment field has a captcha (one of those distorted-text-in-an-image thingies) as an anti-spam defense.

Oh yeah, I know -- the current theme could use some work. The old one I had isn't compatible with the site update. I'll probably have a somewhat nicer-looking version up in the next week or so.