Observatory Teething Problems

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.

Hi Jeff,
I would say that a dew shield made from the sleeping bag foam ground pad would help a lot. It would help by holding the heat and making a drier air dam in front of the corrector. I did this with my NS8GPS and it helped a lot.
For the lights. Get some tail lamp lens repair tape (Translucent Red Tape) , available at an automotive store and apply it over the lights.
You could use a EP heater strap for the laser.
As for the Blue Snowball, yup, it is Blue all right! Looks a bit like Uranus or Neptune. 8)

Attached Image:

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.

Regarding the corrector fogging - you definitely need to use a dew shield in combination with a heater. I use a Dew Buster heater controller and they state that use of a dew shield is mandatory for good results.
I made my own dew shield using a sheet of "refletix" (not sure of the spelling) insulation which is like heavy duty bubble pack sheeting that has a shiny silver coating on both sides. I got mine at Home Depot. On the inside is black felt attached with spray adhesive.
Anacortes sells one made from this material from Just-Cheney Ent. I didn't see one specifically for the 16" SCT, but they could probably make one for you if you don't want to do it yourself.
I use mine with the Dew Buster on a 8" SCT in the Seattle area which is notoriously damp and it works great.
Dave