Posts Made By: Jeff Young

Technical Innovations finishes the inside of their domes in a dark blue, which I matched to paint the inside of the walls upstairs. Since there's no fire-break in the walls at floor level, some of the paint misted down to the first floor. The effect is nice though: reminds one a bit of twilight.

Dan --

I'm under the impression that the newer Naglers have gone in the other direction: that they've traded off more pincushion for reduced curvature of field.

I, for one, don't notice much curvature on my T6. Then again, my eyes might just be more accomodative than most.

-- Jeff.

We don't get much daylight in the winter at this latitude, so I got out there early to take off the temporary roof. Rather foggy, but not too cold, and the sun's starting to break through....

One day after dome completion, we awoke to a surprise. (We don't get snow very often, and almost never an inch or two on the ground.) Makes for a pretty sight, though.

Here's a picture from two hills away. The bottom version has the observatory cicled in yellow, while the top is untouched. To the right of the observatory is the house, and to the right again is the stable-yard with copper-domed clock tower (which, sadly, we don't own).

-- Jeff.

I ran experiment #1 last night: I taped a paper dew shield around the OTA, extending approx 15" past the corrector. Dew was much better (although not completely) controlled.

Interestingly, the corrector fogged a bit right around the secondary *on the inside*. I was pointing near zenith for some time, so I expect my expelled (humid) breath was rising up through the fan and vent holes into the OTA. I probably should have been running the fan.

Dew last night was heavy, but not super-heavy like the previous time out. So I expect I need a shield and some active ventilation. Now I just need to decide between a metal one and getting Floyd to make me an ABS one....

-- Jeff.

I ran some more tests today. My pier doesn't ring like a bell, but my floor does vibrate like a drum. The hair dryer produces some electrical feedback into my 12V power supply, which is sitting on the floor and makes it vibrate at a resonant frequency. (At least I think it must be resonant -- it fills the whole dome with a humming sound.) Isolating the power supply from the floor removes most of the hum (some remains coming directly from the power supply itself). Given that I'm in a 10' diameter cylinder, that suggests the frequency is more like 90hz, which doesn't make much sense for the hair drier itself, but I suppose a switching power supply could vibrate at almost any frequency.

Sadly, I'm not sure this means anything for my dec drive. Putting my ear to the fork arm, the intermittent hum/vibration is unmistakable (one might even say loud). Putting my ear to the drive base it is quite a bit softer (but still louder than the RA drive, which is right behind my ear). Putting my ear to the pier, it can still be heard, but the sound arriving at my other ear (ie: through the air) is louder.

This, I suppose, is consistent with a vibration being amplified by the dome and/or floor. But if I hug the right fork arm (still with my ear to it), the sound doesn't change any.

Theory 1: Given the vertical dampening (ie: softer as you go down), the pier doesn't sound like the problem.

Theory 2: The dec drive is on the end of the fork, which might make it more susceptable to the 90hz resonance of my floor.

Theory 3: I can't imagine this resonance not being damped by my hugging the arm. (But I'm no sound engineer.)

Theory 4: Even if the vibration were being reinforced, it seems like it's stong enough to produce problems even without the resonant reinforcement.

Any feedback on these theories would be *greatly* appreciated.

-- Jeff.

For planetary and double stars, I'd go with UO orthos.

But I'd also get a wide-field in the 8mm to 12mm range -- a WO UWAN would do well at f/10, or a Nagler T6 if you also want to use it in faster scopes or are concerned about resale value.
You can't do -just- planetary and double stars!

-- Jeff.

All right, someone wants to respond to this. Don't you?

-- Jeff.

Chuck --

I have a 16" f/10 SCT which has almost the exact same focal length as your 14" f/11. I've also gone the Pan/Nagler route.

I use the Panoptics at the longer focal lengths because I find the Naglers somewhat cost-prohibitive. I've got a Panoptic 41 and 27 to cover that end.

I have a Panoptic 19 and Nagler 11 T6 to cover the shorter focal lengths, but I find their eye-relief a bit too short. I'm currently replacing them with 12 and 17mm Nagler T4s. (The T4's have plenty of eyerelief, while the other designs are more focal-length-dependant.)

I originally got Tak LEs for planetary, but I'm replacing them with volcano-top UO orthos. I like the color-free views of the orthos, and they don't fog as readily as the Taks do.

I like to keep things as simple as possible in the dark, so I avoid barlows. Even my variable polarizer bugs me, but I've found it's pretty much required for the planets with 16" of aperture.

If I had to do without one of those, it'd be the 12mm T4. You could get a lot done with the P41, P27, and 17T4.

-- Jeff.