Seeking thin crescents
There is a possibility for us in Colorado this month to break some thin crescent observing records that Peter mentioned in his blog last January. Inspired by that prospect (or maybe temporary insanity), I got up about 4:30 am this morning, packed up the notebook, binoculars, and camera and headed off to a parking area east of Louisville’s Monarch High School to see if I could spot the waning crescent. I started scanning the horizon at 5:40 with 10×50 binoculars but wasn’t able to see it until 6:03 am, only 20 minutes before sunrise. Only a thin patch was visible, maybe 10 arc minutes long. At first I thought it was just a small jet contrail as contrast between it and the background was better than expected. Also the azimuth was to the south (right) of sunrise point. I had figured earlier it would be to the north (left). A quick check with sky chart software confirmed that the position was correct and I’d been searching mostly in the wrong direction earlier.
I changed my position so that the limb of a distant tree was just below the crescent to see if I could see it without the binoculars. I was able to see a small light point that matched with the binocular position. I switched between binoculars view and no binoculars several times to check. I was only able to spot the faint patch only twice out of 5 or so tries though, so it was at the muddy edge of visibility.
I also shot a number of images of the horizon with a Canon Xti but used too wide an angle. I suspect high magnification is needed to increase contrast between the bright twilight and the scarcely brighter thin crescent. Sky was mostly clear, no wind, temperature was 47° F, transparency excellent, turbulence fair or better.
Unfortunately, weather is turning rainy for a few days here, so the prospects for seeing the new crescent Tuesday evening and breaking the crescent moon bracket interval aren’t looking good.
Update April 17
The skies cleared late in the afternoon, so I packed up the cameras, scopes, and other equipment and set up at a trail head on Davidson Mesa just off nearby McCaslin Blvd. Unfortunately there was a band of clouds over the mountains to the west which was in exactly the wrong place. It was clear to the south, north, and overhead. Maybe next year..