Posts Made By: Jeff Young

Visual train: Tak Cassegrain focuser (with rotator), Vixen 2" occular adapter (much shorter than Tak), AP MaxBright.

With this setup, my 9T1, 12 & 17T4s, and 32Mk80 all come to focus. A 22T4 or 31T5 (TV's most back-focus-consumptive eyepieces) might not.

-- Jeff

Scribing a centerline for the AP600EGTO mounting holes. (It was later discovered that these holes were at the wrong radius. More on that later....)

So I centered a 3-jaw chuck on the rotary table...

All the above was done in Ireland, where I have my shop and observatory. But the Mewlon (and mount) are in Colorado where we spend a month each summer.

Of course, arriving in Colorado I discover that I've made holes to fit the AP900, not the AP600.

Next, I discover that there aren't any machine shops in Summit County, CO. (My tools there consist of a dime-store tool kit in a blow-molded plastic case.) I figure if I'm going to drive to Denver I might as well go the back way to Colorado Springs, so I call up Paul at Van Slyke Instruments and he says "sure, come on down".

Here's the finished adapter (with a second set of holes) mounted on the AP600EGTO.

Hans --

The Dilworth uses a set of relay lenses to transmit the light cone outside the telescope. Otherwise, with the short focal ratio, the focal plane would be inside the telescope.

I don't know anything about Takahashi's example, however.

-- Jeff.

Going back a bit farther, I got a couple of short nights in a row at the beginning of October:

The 2nd showed mediocre seeing and transparency. First up was a sketch of the Cat's Eye prompted by a thread on CloudyNights. (Well, first up was about 40 minutes of vacuuming dead flies from my observatory, but I assume you all don't want to hear about that.)

NGC6543 Cat's Eye 2 Oct 2008, 22:40UT; Pickering 5, NELM 5.5, SQM 20.5
16" APM Mak-Cass, AP1200GTO

Like many planetaries, this one looks completely different in the eyepiece from photos. I wasn't able to make out any of the internal shells, but several of them condense to show a brighter crescent to the NNE somewhat surrounding the central star. There are also wisps of much dimmer material, most prominently to the SW and NE.

I then spent about an hour trying to see Gyulbudaghian's Nebula (actually a Herbig-Haro object). I don't know why I keep at it -- this was my fourth attempt with no luck.

Next up was Stephan's Quintet, but I wasn't able to make out anything beyond the two brighter components. It was then that I discovered that I didn't have my dew heater cranked up enough, and the center of my corrector was a bit fogged so I called it a night.

Monday showed considerably better seeing and marginally better transparency. I returned to the Cat's Eye first, but even in Pickering 7 I was unable to resolve any of the internal shells. So I went back to Stephan's Quintet.

HCG92 Stephan's Quintet 3 Oct 2008, 21:10UT; Pickering 7, NELM 5.5, SQM 20.6
16" APM Mak-Cass, AP1200GTO

The pairing at the center showed itself first, with a fairly obviuos bi-polar nature, but poor condensation. The more elongated member to the SE was also fairly easy, with a more marked condesation. These members were somewhere between direct and averted-only, but from there it got much more difficult.

I originally sketched the SW member as a star, but study of it at 450x revealed that it never resolved as tightly as other field stars of similar magnitude. It is very dim, with a semi-stellar core.

The NE component nearly alluded me. No condensation what-so-ever, quite small and considerably dimmer than the others. Not holdable in averted-vision, but there perhaps 50% of the time, and easily re-acquired once I had found it a couple of times.

A chart of the field would have helped greatly here, but I still don't trust myself not to have averted imagination, so I don't like to bring charts out.

With reasonable success on Stephan's, I thought I'd see how many of NGC7331's fleas I could find.

NGC7331 3 Oct 2008, 21:45UT; Pickering 7, NELM 5.5, SQM 20.6
16" APM Mak-Cass, AP1200GTO

NGC7331 is quite bright with a well-condensed, elongated core. The brightest and most extended flea to the ENE shows itself first; the other two I captured have semi-stellar cores and took 450x to differentiate from dim field stars.

Well-pleased with how that went I tackled one more.

NGC7332 and NGC7339 3 Oct 2008, 22:10UT; Pickering 7, NELM 5.5, SQM 20.6
16" APM Mak-Cass, AP1200GTO

NGC7332 slightly brighter than 7331, but 7339 considerably dimmer. 7332 shows a well-condensed core while 7339 shows no core at all. Both of similar size and proportions, with 7332 perhaps being a bit more pinched at either end.

Cheers,
-- Jeff.

Thanks Warren and Gerald!

I too wouldn't mind seeing a sketching forum. The one on CloudyNights sees quite a bit of action.

Cheers,
-- Jeff.

M96

#2

Thanks, Tom and Randall!

-- Jeff.