Observing report from Little Compton - 22 Sep 05

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Observing report from Little Compton - 22 Sep 05

Postby Pete » Fri Sep 23, 2005 7:23 pm

Observing report from Little Compton – 22 Sep 05

Last night looked like it would be the last chance for observing before a prolonged period of cloud and crud. It was going to be a brief session as moonrise was at 21:00 and a cold front was not too distant and coming in fast. Bob Magnuson had the same thoughts, so we met at his dark site in Little Compton.

Bob had his 15” Dob and I set up my 12” GPS. Unfortunately the wind was about 20 knots from the SW and was picking up a LOT of moisture from the wave tops. Not a night for the dew shield, and with a breeze like that I didn’t think the dew heater would do much good either. For a while there were some clouds to the N and W that were reflecting sunlight, and the site wasn’t really dark. But after a while it darkened up to what Bob thought might have been the best sky of the year.

This is going to be a very short night. I left Barrington at 18:30 hrs and arrived at the site an hour later. So rather than using the reticuled eyepiece I just center the two alignment stars in the Nagler 31 and roll. A check on M15 shows the globe to be exactly centered. But I’m not looking at globulars tonight – I’m hunting asteroids. So my M15 check takes a view of about ½ second.

19:45 Venus has been brilliant in the W, but by the time the scope is set up it’s only 5° above the horizon and deep in the crud. I view it briefly – or at least the half that’s visible. No detail.

19:48 – 20:09 hrs. Asteroid 986 Amelia is only 13.8 magnitude and is 34° below the ecliptic. That puts it only 13° above the edge of the ocean, and down in the blowing spray. Even with the 9mm in the 12” I can’t see below 13.2 magnitude, so I give up on this one plus another very nearby 13.8 mag asteroid I’d planned on observing.

22 Sep 05; 20:25 hrs. 426 Hippo is a 13.3 mag minor planet 134 km in size. I’ve got it in the 12” at 179X by first star hopping up from an 11th mag double to the SE while using 97X. I had to go up to 179X to sort out Hippo from nearby stars of 12.7 and 13.7 magnitude. Hippo has a heliocentric orbit of 3.2 AU and it is presently 2.3 AU from Earth.

22 Sep 05; 20:30 hrs. 372 Palma is an 11.7 mag asteroid 195 km in size. I’ve got it almost immediately in the 12” at 98X as it lies in a N-S chain of 11th mag stars anchored by a 9th mag star in the S. Palma orbits our sun at 3.0 AU and it is currently 2.0 AU from Earth.

22 Sep 05; 20:33 hrs. 437 Rhodia is only 14 km in size but it shines at 12.2 magnitude due to its relative closeness. It’s closeness also makes it a relatively “fast mover.” I’ve got it in the 12” at 98X after star hopping down from an 8.8 mag star to the N. Rhodia orbits the sun at 1.83 AU and is only .87 AU from Earth at this time.

22 Sep 05; 20:41 hrs. 417 Suevia is a dim 14.0 mag asteroid 43 km in size. It lies midway in a chain of stars running anchored in the NW by an 8th mag star and running SE. Starting viewing thru the 12” at 98X, I increase magnification to 179X, 254X and 339X without seeing Suevia. But then I go back to viewing in the 12mm Nagler (254X) and eventually I’ve got it along with a 13.8 mag star less than 1’ to the ENE. Suevia orbits Sol at 3.1 AU and it’s now 2.2 AU from Earth.

22 Sep 05; 20:44 hrs. 101 Helena is a 10.9 mag minor planet 68 km in size. I’ve got it quickly in the 12” at 98X thanks to a line of 3 closely spaced 10th mag stars just 10’ to the E. And I’ve also got nearby 13.4 and 13.7 mag stars. Helena orbits Sol at 2.2 AU and is presently 1.3 AU from Earth.

22 Sep 05; 20:46 hrs. 123 Brunhild is a 12.4 mag asteroid 50 km in size. There’s a unique grouping of three 10th mag stars about 6’ to the N, and a 9th mag star only 1’ to the N, so I’ve got it rather quickly in the 12” at 98X. These bright stars aren’t really bright and after another few minutes I’ll discover that the scope is badly dewed up. Brunhild orbits 2.6 AU from Sol, and is now 1.6 AU from Earth.

22 Sep 05: 20:52 hrs. 156 Xanthippe (who names these anyway?) is a 13.1 mag asteroid 126 km in size. I’ve got it in the 12” at 98X, but need to go to 179X to view two 13.9 mag stars in the immediate vicinity so as to insure that it is indeed Xanthippe I’m viewing and not something else. Xanthippe orbits Sol at 3.1 AU and is now 2.1 AU from Earth.

22 Sep 05; 20:59 hrs. 686 Gersuind is a bright 12.0 mag asteroid high in the sky. I’ve got it at 98X in the 12” by star hopping down from an 8th mag star in the NW of my fov. And I’ve got nearby confirmation stars of 13.6 and 13.9 magnitude by increasing the magnification to 179X (Nagler 17mm). Gersuind is 44 km in size. It orbits Sol at 2.0 AU and is presently 1.0 AU from Earth.

21:03 hrs. I was about to take another shot at my first missed asteroid of the night when I happened to check out my corrector plate and found it to be as wet as everything else around us. Neither of Bob nor I had noticed the moisture buildup on our optics as our last objects were relatively bright. But with the wind blowing we suspected that it was more salt water than fresh.

We checked out a couple of objects thru Bob's big Dob and in spite of the heavy dew they still looked great. You lose a couple of magnitudes with dew, but when you're working with a 15" primary I guess you've got aperture to spare.

The moon was starting to rise and we’d both just finished our observing lists, so we packed up and just visually enjoyed the stars for a bit. Seeing M31 naked eye is a rare thing along the eastern seaboard.

Conclusions & lessons learned:

• This morning I inspected the corrector plate and found it to be dry but pretty crudded up, confirming my suspicion that there was more than a little salt water in last night’s air. Bob and I both make it a practice to clean optics after viewing at the coast on a windy night. It’s a small price to pay for the use of our oasis of darkness.

If this were anything but a scope I’d be tempted to use a hose. I made up my normal cleaning solution of 91% isopropyl alcohol mixed 60/40 with distilled water. After turning on the A/C to dry out the air I applied the solution liberally to the corrector plate with a torn-up cotton ball and then wiped it off with several more torn-up cotton balls.

Because of the salt on the glass the first cleaning wasn’t enough. It never is for some reason. You get the heavy stuff the first time and it looks nice the second time.

Usually I don’t clean my corrector for 6 to 12 months at a time, but salt spray probably doesn’t enhance the coatings. And it’s hard to see through. Cleaning with my procedure does take a bit of time. Perhaps using a hose would be quicker after all……..

• I’d been in a rush to get rolling and my night’s list was a bit shorter than usual. But the night was shorter than usual anyway, and we did get in an hour of really great observing.

• The 25 mile drive back to Barrington was traffic free and took 46 minutes. The drive down took a full hour. Not a bad price to pay for a site where you can see details of the milky way from the southern horizon all the way through the zenith and to Cassiopeia. It’s not as dark as Arunah Hill, but it is relatively close by. And you’ve gotta love that
-1° southern horizon.

Pete 23 Sep 05
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