Wednesday, September 24, 2008

Frustrating Skies: Neptune At 50mm

Last year about this time I posted about observing Neptune through my 60mm refractor—Starhopping Through Capricornus To Neptune

That was a pretty cool thing for me, one of my favorite astronomy memories of all time. Neptune is—in classic Sagan-speak—billions of miles away. It’s the farthest thing in the solar system I’m ever going to see. And for my 60mm refractor it completed the planets: Mercury, Venus, Mars, Jupiter, Saturn, Uranus and Neptune.

However, last year I wasn’t able to observe Neptune through my 50mm binoculars. I tried, more than once, but never could see it. Neptune would complete the planets for my binoculars, too.

However—again—last year I was handholding my binoculars. Since then I bought a tripod adaptor for my binoculars and the difference can be amazing. I wrote about the difference observing the Beehive through tripod-mounted binoculars in Mars Almost In The Beehive.

So, since this is such a perfect time of year for observing Capricornus—Endings And Beginnings—I decided to spend time in Capricornus but only with my 50mm binoculars on their tripod.

Sky & Telescope has a PDF finder chart available online for Uranus and Neptune. It’s not a very good chart, but if you have a reasonably good star atlas, the chart should be enough.

Right now Neptune is at magnitude 7.8 in eastern Capricornus, just north of where I observed it last year. The distinctive three field stars above Delta Capricorni are about magnitude 5.5. There are two dimmer field stars just west of 42 Capricorni that are magnitude 8 or 9.

Since I’ve gotten the tripod adaptor for my binoculars I’ve casually looked through Capricornus, without looking for Neptune, and on good nights I’ve been able to see those dim field stars at magnitude 8 or 9.

So with my tripod mounted binoculars I should be able to see Neptune. (In fact, I may have glanced past it without knowing it when I’ve scanned through Capricornus.)

But the skies here south of Chicago haven’t been cooperating.

We’ve had a few clear nights recently, but it’s been a strange kind of clear. Bright stars—Arcturus, Vega, the planet Jupiter—have been easy to see. But high, thin clouds or low, thin haze have been blocking out dimmer stars.

Looking through Capricornus with my tripod mounted binoculars I easily find Alpha and Beta Capricorni. I can scan east easily enough and find Delta. But catching the distinctive three field stars 42, 44 and 45 Capricorni has been the limit of what I can see. And they’ve been tough.

So—damn it!—I’m pretty darn close to seeing Neptune through my binoculars.

I can see where Neptune is.

But I haven’t seen Neptune yet at 50mm.

This has become my Autumn project.

I’m doing my part. I’m trying. Now Nature has to do Her part and clear away these darn high clouds and low haze.

I’ll report back after a really clear night.

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