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Carbon

Lightbridge 12 base project

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Hello.... Here are some build photos of the new base I'm currently working on for my Lightbridge 12.

I'm using 1" hardwood plywood throughout.

I added leveling feet to make leveling easier when using setting circles where a level base is critical for its accuracy. This sure beats getting down on my hands and knees to use shims to level the base.

The ground board is only 18" in diameter, plus a couple of inches for the ears for the leveling feet. This is much smaller than the stock ground board diameter of over 22". Actually, the new azimuth bearing contact diameter will be larger than stock.

The altitude bearings are 24" in diameter, roughly 1.7x the OTA diameter. Hopefully, I won't be needing counterweights when switching from light to heavy eye pieces. I also moved the scope's center point of gravity slightly higher for better balance.

The base will be painted white to match the scope.

I'll be posting more photos as I near completion.

Thanks for looking!

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Great job so far, that looks like it will be a massive improvement on the standard groundboard/rocker assembly.

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I really like the look of this. It will be good to see how it develops.

Dave

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very cool project. quite a unique design too. those large alt bearings will work like a dream compared with the standard teacup sized ones.

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Thats looking great - a major improvement over the stock Lightbridge base :smiley:

very cool project. quite a unique design too. those large alt bearings will work like a dream compared with the standard teacup sized ones.

Thats a good point. All the classic dobs designs seemed to have these large alt bearings and yet the chinese decided to go with very small ones with their dobs. The Lightbridge design has at least used slightly larger "mag wheel" style ones but even those are half the diameter of the primary or less. I guess it's a compromise to ease mass production but not a good one :undecided:

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very true John. but the production of a circular (or half circular) large alt bearing (even in the same materials as the rest of the base) would be far easier, cheaper and work better too.

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very true John. but the production of a circular (or half circular) large alt bearing (even in the same materials as the rest of the base) would be far easier, cheaper and work better too.

Still, at least improving them gives us something to do and discuss when it's cloudy !

They say all mass produced dobs are a "work in progress" out of the box which is quite true I reckon :smiley:

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:smiley: being able to mod things and work on them is one of the (many) reasons I only have dobs.

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Looking good! Looks like it could topple over though but I'm sure you've done the maths :D

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Looks good! I was doodling designs myself this weekend, think I'll put it on hold till I see how yours turns out! Where did you source your feet from please?

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Thank you all, for your replies so far. Yeah, I agree, dobs are so much more fun to tinker with. :)

As far as stability, the ground feet are spaced at least 18" apart from one another, and in combination with a relatively small 12" mirror I'm certain stability will not be an issue. I've seen larger custom dobs will even smaller foot prints.

And as for the choice of altitude bearing size I opted for the larger end of the scale. A couple of ATM sites recommended up to 1.8X the diameter of the OTA. I went with 24" diameter which is roughly 1.7x the diameter of my OTA.

I ordered the leveling feet and steel knobs from here:

http://carrlane.com/catalog/index.cfm/27025071F0B221118070C1C512D020609090C0015482013180B041D1E173C3B2853524455

George

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the black painted finish looks good. how was it applied and what sort of paint? I presume sprayed?

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the black painted finish looks good. how was it applied and what sort of paint? I presume sprayed?

Thanks. I used dark gray primer and flat black paint, both in spray cans.

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Here's a size comparison between my old modified/downsized stock base and my new base.

Although I trimmed bits and pieces from the stock base to make it quite a bit smaller and lighter the new plywood base is by far much lighter and more compact.

A cutout will be made at the front of the base for the azimuth setting circle.

P1060867.jpg

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Thanks!

I made a cut out at the front of the base for the azimuth setting circle. I also started applying thin coats of white primer to the base. The base will end up with gloss white paint to match the rest of the scope.

P1060869.jpg

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I decided to just stick with the stock Lightbridge az bearing for the time being as I found a 1/2" OD / 3/8" ID bronze bushing to fit it perfectly.

I also drew directly on the board degree circle lines in 5 degree increments (plenty enough for me) and will later freehand the numerals using the same Sharpie marker.

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Really looks the part! Love the picture of your beautifully crafted design next to the drab Meade effort.

Really nice job

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Thanks!

The ground board is now finished. When I find a suitable degree circle file with large bold numbers (for my old eyes) I will print it and paste it on the ground board. I like to be able to just glance down to see the azimuth reading from my eye piece position without having to squat down each time.

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Really nice work!! I am looking forward to seeing the whole base assembled with scope onboard.

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Thanks!

Well, a day after spending a couple of hours drawing the setting circle on the ground board a member over at CN gave me a setting circle file that seemed to be exactly what I was looking for so I had a two copies printed at the local printer. It now looks like I will be using them.

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The base is done! :)

I'll be working on finish mounting the altitude bearing assembly on the lower tube assembly of my Lightbridge this weekend.

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That's a handsome job, very nice looking setting circle......and the base is not bad. :grin: :grin:

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