Posts Made By: Jeff Young

Jato (over cloudy-nights way) started a "Frapper" group for private observatories. Basically, it's a bulletin-board-type thing that allows folks to put push-pins in a worldwide map along with a pic and some text. You can zoom in an out, pan around, and display either a map or a satellite picture. Pretty neat, actually.

Anyway, see: http://www.risingconcepts.com/frapper/observatories.

-- Jeff.

Mike --

The other day I had my SCT out at a public event. A boy came up and wanted to take a look, but the eyepiece was a little too high. So I angled it to the left for him. At which point the weight of the eyepiece caused the barrel of my WO diagonal to unscrew until the eyepiece was pointing directly down.

Now, I don't know if the eyepiece would have fallen out without a safety undercut, but my dislike of them was somewhat tempered by this event.

I now always angle the diagonal clockwise (so the weight tries to screw the barrel in farther). I've also noted that with a little wear on the compression ring, the undercuts seem to catch less often. You might even want to sand or file the corners of your brass (or copper) compression rings a bit. It's too bad the manufacturers don't make them a bit rounded.

-- Jeff.

Even though my dec drive is still flawed (tracking produces vibration), I've been able to make some use of my 16" LX200GPS and observatory at less than 200x magnification (where the vibration is barely noticible).

See http://www.astromart.com/forums/viewpost.asp?forum_post_id=381632 for the observatory construction and pics of the scope.

Anyhoo, I've got some issues:

1) I've got a serious dew problem. With the heater strap cranked to full, I get about 1/2 hour before the corrector fogs. A minute or so with the hair-drier clears it, after which the 1/2 hour clock starts ticking again.

I've considered adding a second strap, but I'm concerned I'll overheat the corrector and end up with thermals coming off it.

I've also considered a dew shield (I use one to good effect on my 8" LX200GPS), but the dome slot should be shielding the corrector plate from most of the sky, so I'm not sure how much it will help. (And the 16" ones aren't cheap.)

2) I've got a bunch of indicator lights that are too bright. These include the LX200GPS front-panel light, the dew controller lights, and my 12V power supply light. (The front-panel light can be turned off, but I'd rather know the scope was on.)

Anyone tried painting them with nail polish or something to dim them?

3) The wide stance of my Kendrick Ultimate III observing chair works great in the field; not so great in the observatory. I keep bumping a leg when rotating the dome, and then the seat rattles down to the bottom. What I'd really like is a pneumatic stool on wheels, but I've never seen one with 20" (or so) of vertical travel. Anyone else?

4) I still need to figure out a way to heat my green laser pointer. It worked fine last night at 4°C, whereas I had problems a few nights ago at 2°C. So at least I know at what point the crystal gives up now.

Then again, now that I'm parking my scope (and don't need to align each session), the only thing I need it for is when I'm wondering where something I'm viewing is with respect to the naked eye view.

5) One last thing: through 16" of aperture, the blue snowball is barely (but noticeably), well, blue. 8)

-- Jeff.

The other night I had a dew problem. Noticed the hair drier emitted a nasty buzz when used on low, but worked fine on high. I've been fighting a vibration problem in my SCT's dec drive, so I thought maybe the hair drier was giving me a clue, and it had something to do with the 100m of wire coming out from the house. Re-booted the scope on a battery, but it didn't help.

So I'm back out there today during the day stripping the dec drive down (again). I brought a fan-forced heater out with me, and noticed that when I set it on the floor, it also produced a nasty buzzing. Perhaps a harmonic frequency of my 10' diameter timber studded, timber floored, 10' fiberglass dome observatory? Something around 50hz, perhaps?

Here's a wild idea. Is there any chance that the vibration in my dec drive (while tracking, particularly bad around the north celestial pole) is a result of the motor producing a bit of 50hz vibration, which is then amplified by the harmonics? Could they really amplify it that much (Polaris get stretched into an 8" dumbell when the motor buzzes)? The buzzing the motor produces is, with vague recollection, similar to the pitch of the hair-drier (and heater).

Or am I clutching at straws here?

Thanks,
-- Jeff.

I've got an SCT currently mounted on a pier which is slightly off level (perhaps 1/8" over the top plate's 16" diameter). I've got an LX200GPS on it, which doesn't really care if its level or not, so it hasn't been a problem.

But I'm considering getting a wedge for a polar mounting. Given that the wedges are adjustable along two perpendicular axes, I should be able to point directly toward the celestial pole even starting from slightly off-level right?

-- Jeff.

I've read that a good deal of one's ability to detect faint fuzzies lies in the brain's (and eye's) processing of the image "bits" one is getting. Evidently, the more receptors you can get involved, the easier the brain has it, so larger exit pupils help.

At a given exit pupil size, does a larger AFOV help? That is, are the off-axis rays at the edge of the exit pupil more steeply angled, and therefore covering a larger percentage of the retina, or is the retinal coverage entirely a funcion of exit pupil (and your eye's focus distance)?

-- Jeff.

Meet my Lemon Mark I: big aperture attached to a buzzy dec motor that intermittently ruins the views....

My FC100 rides piggyback on a 16" SCT, so it's used mostly for low power, wide field work.

I recently got an AP Convertible Barlow for the SCT, but I find I keep using it with the Tak as well (it's handy for estimating seeing -- since you can actually see the diffraction pattern -- and I've found myself looking at some targets at higher powers in both the SCT and the Tak).

In fact, I've been using the Tak enough at high power that I'm tired of swapping the one barlow around. The problem is that the Tak won't reach focus with the AP barlow after the 2" diagonal; I have to put it before the diagonal, which requires quite a bit more assembly/dissassembly every time I want to move it.

I don't think I'd be looking to spend a whole bunch of coin on a second barlow, though, so I'll probably be looking for a 1.25" to use with my UO orthos (rather than a second 2" unit). Will a 1.25" unit (such as a UO Klee or TV 3X) come to focus in the Tak (after a 2" diagonal), or do I need to go with a Powermate?

Thanks,
-- Jeff.

I tallied up my observations in AstroPlanner for the last year (there was a huge fall-off after the first 4, so I included all of them):

17T4 .... 45 observations
26T5 .... 29 observations
12T4 .... 19 observations
Pan41 .. 12 observations

16" f/10 SCT.

I've recently started using a DeepSky filter with the Pan41 to counteract the gray sky produced by my local light pollution, so I expect it to fare slightly better going forward (although it's still annoyingly big and heavy).

-- Jeff.

I could swear I used to get an email notification whenever I received a private message.

But I don't anymore.

Is there some setting I need to change (I looked around but I couldn't find one), or does the system no longer do this, or do I have a faulty memory (and it never did do it)?

Thanks,
-- Jeff.