Jupiter Occultation of 45 Cap

Date: 2009-08-04
Time: 3:24 UT
Location: Snellville, GA
Telescope: Dob 10-in f/4.5 and also stopped down to 3.5-in f/13
Magnification: 114x
Objects: Jupiter, Europa and 45 Cap
Seeing: 4 (1--4)
Atmosphere: Humid, slight clouds. Clear around Jupiter during observing.

45 Cap and Europa had already emerged when I began observing. Europa was barely separated from the limb. Here are some (badly typed) posts from Twitter.

with Dob 10 f/4.5 Europa is just off the limb 2009-08-04 03:24:59 UT

Now four obj following. Closest is maybe 1/6 Jup diameter from Jup and right on the equator. 2009-08-04 03:47:41 UT

Europa was clearly separated and visible. The occulatation was actually over when Jupiter rose since the emergence time of 45 Cap was really 1:00 UT. I was confused by the S&T article and thought it emerged at 2:39 but that was the Io emergence time.

Here's a “sketch” made with MS Paint at 2009-08-04 12:48 UT, some hours later.

Seeing = 4 (1--4). Excellent belt detail. 2009-08-04 04:02:00 UT

Seeing was quite good after the telescope settled down. I observed with and without the aperture mask. I was going to try out the Pickering scale on a star, something I think I used to do many, many years ago, but forgot to do that as I was putting the telescope up.

there is a daek feature in the NEB that extends to the following side. 2009-08-04 04:03:03 UT

(More bad typing. daek = dark). Near the central meridian (CM) was a dark spot in the North Equatorial Belt and it looked like it was part of a dark feature that extended from the CM to the eastern side. I've represented it roughly in the above sketch.

I'm using a hand truck to move the telescope around. The problem is the telescope ground board and box are long enough that the whole thing wants to tip forward when trying to rock it back on the hand truck. My current solution is a piece of very strong string/cord looped from one brass handle, around the hand truck, to the other brass handle, and then wrapped a few times around the top of the handle where my hand is. That's enough to keep the telescope from tipping forward.

I Saw the Impact Site

Date: 2009-07-24
Time: 02:11 UT
Location: Snellville, GA
Telescope: 10-in f/4.5 Dobsonian, stopped down off-axis to 3.5-in f/15
Magnification: 110x
Object: Jupiter and impact site
Seeing: 4 (0--4)
Atmosphere: Moderate clouds passing over Jupiter.

Again, I'm adding this entry after the fact. Here are my live tweets. (Tweet times are EDT).

Jupiter I can see the impact site. It is tiny and intense black. It comes and goes in the seeing.10:11 PM Jul 23rd

jupiter I am literally observing through passing clouds. The planet is fading in and out.10:13 PM Jul 23rd

Jupiter and the Asteroid Impact Site

Date: 2009-07-22
Time: 04:33 UT
Location: Snellville, GA
Telescope: 10-in Dobsonian f/4.5
Magnifications: 44x, 110x
Object: Jupiter
Seeing (scale 0--4) Started out at 1 and worked it's way up to 3.
Atmosphere: Light clouds. Cool air for the summer.

I'm entering these notes nearly two days after the observations.

I started observing before the telescope had come to temperature. Also Jupiter was quite low in the East so, from at least those two factors, the seeing was quite terrible. The four Galilean moons were dancing sparklers and it was very difficult to see any detail on the planet other than the main belts.

I'll include the tweets I made at the time.

Observing Jupiter. 10-in f/5.4 Dob, 110x. Seeing is terrible, 1 (0--4). SEB and GEB easy but no GRS or impact site.12:33 AM Jul 22nd .

As the planet rose higher and the telescope settled down, the viewing was much better. I was easily able to see the North Equatorial Belt and the North Temperate Belt (NTeB). The South Equatorial Belt (SEB) was also easily divided into it's two parts.

Seeing is better, 3. Tel has settled down and planet is higher. NEB a d belt just north easy. Still no GRS or impact.12:47 AM Jul 22nd

I couldn't see the GRS, Great Red Spot (hollow), at all though it may have rotated to the limb at the time.

As the seeing improved, the four moons became tiny disks. One was leading (Io) and three following (Ganymede, Europa and Callisto from west to east away from Jupiter). The identification is based on Sky and Telescope's moon Javascript program.

For much of the time I used the 3.5-in aperture stop which makes my Newtonian an f/15 unobstructed off-axis telescope. Most observing was done at 110x.

By 5:00 UT thin clouds covered the planet but I continued to observe through them. They mainly just attenuated the brightness.

I was never able to resolve the impact site. It should have been there but at this magnitude, with the seeing and maybe my eyes, I couldn't resolve it. I could see a lot of belt detail and could see the belts including the dark higher latitude belts in the South.

I can see excellent belt detail but no impact site visible in North. Maybe it's smeared?1:01 AM Jul 22nd

Well I don't see it. The SEB appears split in two. I can see the faint belt N of the NEB. But no impact site.1:19 AM Jul 22nd

I stopped observing sometime around 5:19 UT.

Reference: Sky and Telescope Jupiter Observing Guide