Gemini Retrofit kit

[chuckscap (Chuck)]

Hi, after a long hiatus I'm finally having a concrete pier poured with anchor bolts for my vintage Parallax HD mount I bought on Cloudy Nights classifieds. My plan is to use it in non-goto mode for a month or so and get the polar alignment down using the drift method, then to install the Gemini retrofit kit I bought several years ago from Losmandy. Has anyone installed one of these. It doesn't look bad, I just want to know if there are any things I should look out for (limits, etc.) Here's a picture of the mount pier sitting on my deck (which obviously wasn't stable enough).

http://i247.photobucket.com/albums/g..._250_Small.jpg

http://i247.photobucket.com/albums/g...50_2_Small.jpg

Thanks! It's so good to get back in astronomy again, had health issues, better now ...

[wasyoungonce (Brendan)]

Hi Chuck, I'm assuming the kit is a Gemini 1 version? If so you'll need to replace the battery before use.

Looks like you have Losmandy motors on the mount already? I don't remember seeing a Parallax mounts in the Gemini menu but you can custom set divider ratios etc. The mount you have looks a lot like a MI-250...maybe it has similar gear ratios?

A good resource for Gemini users is the Yahoo Gemini forum and the Yahoo GEMINI ASCOM forum.

The Gemini ASCOM driver is particularly important, you can control your mount and back up all your Gemini settings ...and more via computer.

Hope the above helps, post back on your progress.

[chuckscap (Chuck)]

Thanks here's the scoop on my older Parallax HD 150:

"Parallax Model HD 150, Includes digital setting circles with JMI NGC-Max computer. Drive is Losmandy digital with hand controller(with all features typical of Losmandy mounts that use the same drive controller). Mount features tapered Timken roller bearings, 7.5" diameter 359 tooth gears with mating 440 stainless steel worms on both axes, conical housings, 1.5" shafts, adjustable clutch tension on both axes, and detachable stainless counterweight shaft with multiple stainless steel counterweights with brass inserts, 6" diameter Porter slip ring setting circles on both axes. Payload rating-120lbs. Weight: 68lbs, and breaks down into 40lb dec axis with platform and 28lb RA axis. Counterweight shaft is 10lbs. Photographic payload capacity 120 lbs"

Here's the section of the Gemini manual that piqued my interest.
"1.3.1 Gemini Supports Custom Mounts

In addition to support for Losmandy and Mountain Instruments mounts, Gemini L4 now

supports custom mounts. The user can setup the main parameters of his mount: the gear

ratios and direction of spur gear and worm gear and the servo motor encoder resolution.

The step resolution can reach from 0.1 arcsec per step (servo motor encoder tick) up to

2.5 arcsec/step. Resolutions can be set independently for RA and Dec. axes.

With this new feature, Gemini can be retrofitted to many German Equatorial Mounts, for

example mounts with 359:1 Byers gears, Vixen or Astrophysics mounts. Existing servo

motor/encoder combinations can often be used, eliminating the need for mechanical

adapting the Gemini motor assembly, although custom cables will be necessary."

I'll definitely take your advice on the ASCOM driver, I want to be able to park this and maintain my goto ability when I power up and also save any mount modeling I do. I have a Mewlon 250 with ED in baffle corrector and I haven't looked through it in 3 years. Hopefully next weekend, I'm having a concrete pier poured on Tuesday so the mount will be set up permanently.

[wasyoungonce (Brendan)]

Fantastic mount....good to see good older mounts getting the care and use they deserve!

Since you have a Gemini digital drive....I would guess you already have a gear train that will be easily configurable to the Gemini...meaning bolting on the Gemini servo motors and setting the gear divisors.

Just one thing...try to identify what Gemini version you have as some of the older versions need a opto isolator (or relay interface) for the autoguider input signals from modern guiders and older Sbig guiders.

Gemini 1's also have some little quirks (as all systems do), things like the DTG is different (see bottom of this page) amongst other things.

As you are probably aware the Gemini 2 is released and the Gemini 1 is superseded but despite this it is still a very capable system. Learning the Gemini 1 can be a real exercise in "what the" but after awhile it will make sense and you will see why the system and menu's are designed in the manner they re put. How can I put it..."You'll make sense of the madness..."

Nice scope as well