Wednesday, January 1, 2014

Chasing Skinny Crescents!

Earlier in the week, Sky and Telescope magazine told us of a New Year's Day observing challenge - from the western US, it was possible to spot a very young moon, well under 24 hours after new moon.  It favored us as this time of the year, the ecliptic (path the moon, sun and planets follow), is nearly vertical in the western sky, the moon is near perigee so it appears to move faster, and the timing was right since new moon was at 4:14am Mountain Standard time earlier in the day.  The difficult part was picking it out of the bright twilight shortly after sunset, so a mountain location for clearest skies were perhaps called for...  Hey, it was a holiday, and it was a beautiful New Year's Day, so why not go for a little drive and go for it!

In addition to the skinny crescent of the moon, Venus is nose-diving towards inferior conjunction in a few days (11 January), and would be less than 8 degrees from the moon.  Trying to image the small crescent like we did in Rocky Point last week would be tough because of its low elevation, so again, with the day off, I went after it as the planet transited high in the sky! According to the planet information in Heavens-Above, it would pass due south about 40 degrees high at 1330, so set up the William Optics 11cm APO to try to find it. Binoculars helped to sweep it up, but it was tougher than I thought, since it was only 15 degrees from the sun. I never saw it visually, but once in the scope it was easy. It was still bright enough that I had to use 1/2000 second exposure (a single exposure shown here), and it still might have been overexposed. That is why the sky looks pretty dark, but it is a good shot of the skinny crescent as it passes between us and the sun. The crescent was also easily seen in binoculars, but you only have another couple days to spot it!

About an hour before sunset, Melinda and I
jumped in the van with a couple scopes and cameras and headed to the Mount Lemmon Highway, to the Babad Do'ag (Bad Dog to its sacrilegious friends) lookout.  From this vantage point the sun would set just south of Kitt Peak National Observatory across the Tucson valley, and with any luck, the moon would also be near the silhouette of the Observatory!  I set up a sturdy tripod and  used a little Meade 80mm F/6 (480mm focal length) for some shooting, as well as the 70-200 zoom.  Melinda spotted Venus before sunset, but as the minutes ticked away, I was worried we wouldn't spot the little lunar crescent in the still-bright sky...  Finally, with minutes left before I figured we might as well pack up, I spotted it in 10X44 binoculars!  It was just to the right of Kitt Peak, and barely as high as the top of the mountain!  After I pointed it out to her, Melinda swept it up too and I spent the next few minutes shooting a little mosaic with the Meade, and also catching it with the zoom with Venus in the frame (1/4 second, F/6.3 @90mm focal length, ISO 200).  It was tough to spot, I don't think there was a chance to see it naked eye, but the little elevation we got off the first 3 miles of the Mount Lemmon Highway likely helped.  Looking at it in Photoshop, it was even tough to see in the wide frame without zooming in, so I inserted a magnified, enhanced sub frame to show it better.  It is much easier to see in the 4-frame Meade mosaic with longer exposure (1 second, F/6, ISO 200) and slightly darker sky.  It is visible way on the right edge of the frame, so make sure it is on your screen if you load the full-size image...

In the end, looking at the time stamp, corrected to proper time, we spotted the moon at 1806 local time when the moon was 13h52m old (after new).  Likely a new record for me, though I'm not sure I've ever gone out looking for young moons before.  It was fun - any excuse to get under a clear sky!

1 comment:

The Wheel said...

Happy New Year Dean and Melinda!

Jan and I went to top of the ridge and got a view as well.

What fun!

Here's my report: