Sunday, April 30, 2006

Bullhorn Moon

Tonight the Moon appeared next to a naked-eye star that showed up in the camera without any binoculars or telescopes. The star was Alnath, the tip of the upper horn in Taurus the Bull. I saw Alnath with my own eyes 47 minutes after sunset and began taking some photographs.

This first photo is a crop, the camera in zoom mode. Alnath, a 1.6-magnitude star, can be seen by double-clicking on the photo, just above the moon.

With the camera's digital zoom:

Wednesday, April 12, 2006

Tycho series

I often wonder if there's a better way, with the basic equipment I own, to produce a photo that communicates a sense of what it's like to look through a telescope at the moon. I cannot reproduce the clarity without getting a telescope that will automatically track objects as they rise and set. When I watch the moon, it moves. I thought that the photo below, taken this past Sunday (April 9th), got across something of what it's like to watch the moon taking up room in a circular field of view:

I take photos with an Olympus digital, and my constant challenge is to minimize the exposure time. Longer exposures produce blurry pictures of a moving object, and they also make the moon, which is so bright, into a large white blob. The shortest exposure I have available is the flash setting, which is fine, since it adds nothing to the brightness of the moon and only occasionally gets reflected back by the lens of the eyepiece. Often I'll use the zoom function on the camera, which allows less light to come through the aperture; and in those cases I'll turn the flash off in order to use the settings for longer exposures.

A few months ago I started noticing, when photographing planets and stars, that the camera focuses differently than my own eye. The camera "sees" a different picture than I do. On digital cameras, you have the view-screen, where you can see in real time what the camera sees. I notice that a scene which appears crystal clear to my eye if I look directly into the telescope eyepiece looks blurry in the camera's view-screen, and vice versa. The difference is significant when the eyepiece magnifies the view at a low power, for instance 30x magnification. With eyepieces that push the power up to 180x, I notice no difference.

On Sunday I was photographing the moon at lower powers, with flash, no camera zoom, and at a lower exposure than the default for ordinary indoor photos. This low exposure appeared in the view-screen as a paler moon, and I found that it allowed me to freely photograph the bright areas far from the terminator (that is also possible by using higher powers or the camera zoom, both of which allow less light to come through).

I started watching the view-screen of the camera when I held it up to the eyepiece, and I turned the telescope's focus knob until the camera, not my eye, saw the picture clearly. That produced the series of pictures in this post, which all prominently show off the crater Tycho and its rays.

The photos appear as they do in the telescope, turned upside down by the mirrors. As always, click on the photo for a larger version.

I like this one especially:

The large sea right up against the terminator is Mare Humorum. The large crater sitting on the sea's edge is Gassendi. Leading away from Tycho is a parallel set of rays that look like a tunnel or gorge -- or even a canal! When Tycho was formed by an impact about 108 million years ago, ejecta from the blast formed that pair of rays. They lead directly to a crater called Bullialdus, and if you follow that line you eventually hit Kepler, which is visible in the second photo above.

At about 10:30 with relation to Tycho sits a very large crater called Clavius: you can see in this photo why I sometimes called it double-dimpled. The first large crater at about 12:30 is Longomontanus. The dark craters very far back at 11 o'clock, near the terminator, are in the region of the Leibnitz mountains.

You can "drain" the light, or brightness, out of a photo without losing resolution by adjusting the middle dial in Photoshop's "Levels". Doing so also drained the dim color of the original, but it highlighted Tycho's ejecta rays all the more:

Wednesday, April 05, 2006

Pleiades Occultation report

Ben, who reported his experience with the Pleiades occultations in the comments section of this blog, has his own blog and a detailed report here:

NYC Nova Hunter: Pleiades Occultation: Celaeno Graze 1-Apr

See in particular the comments section of that post for a computerized profile of a single mountain on the moon.

Monday, April 03, 2006

Pleiades eclipse gallery has gathered a gallery of very nice photos of this star/moon conjunction on this page.

Saturday, April 01, 2006

Pleiades eclipsed

Through a cloudy sky, I got a few brief glimpses tonight of the Moon passing over the stars of the Pleiades (the Seven Sisters).

This is a snapshot at 7:27 pm New York time, with Alcyone, the brightest of the cluster, only 27 minutes before the moon's dark limb caught up to it and covered it. Very close to the moon, near the lower left of the lunar disk and much dimmer than Alcyone, is a star called Maia.

This shot at 8:34 p.m. captures, going counterclockwise from the star closest to the Moon's limb, Merope, Electra, Taygeta and Maia. Alcyone was then behind the Moon.

Finally, this shot at 8:56 captures Alcyone hanging above the Moon's bright limb like a rocket taking off from the lunar surface, just two minutes after the star reappeared on that side.

Before tonight I had never seen a star at the instant that it "winked" out and got eclipsed, or watched one while it winked back into view. Tonight I did get to see one such event, through murky clouds almost dark enough to obscure it entirely: I saw Atlas, a multiple star and the second-brightest of the pack, wink out behind the Moon's dark limb at 8:39 p.m.

It was a very frustrating night, with the clouds moving all evening over the Moon and leaving a wide open patch of sky in the south, where the Moon was not. Still, I saw a rare sight. The photos above, taken at a magnification of 30, give a blurry representation of a few moments; but the best sight was in the binoculars at 7 p.m., when the Moon had not yet eclipsed the Dipper-shape of the entire Pleiades cluster but had approached so closely that it seemed the stars were wrapping around the lunar ball.

[Post edited on April 6 to brighten photos].