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computorizing a 16" Meade Lightbridge

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#1 Ettu

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Posted 23 January 2013 - 12:22 PM

I'm considering computerizing my Meade 16" lightbridge. I have a perfectly fuctional LX200 classic platform that I'd like to adapt/convert to the task. I'm afraid though that with the classic's unramped start/stop slew to target, even the slowest slew speed will still be too much for the mass of that scope. Has anyone done this? Any thoughts?

Thanks,
Keith
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http://www.willowber...et/keithnk_m42/

#2 Starman1

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Posted 23 January 2013 - 09:07 PM

The lightbridge is heavier than, larger in diameter than the 16" SCT, and will probably not clear the base.
As far as computerizing is concerned, it's far easier to contact JMI, who makes a fully computerized kit for the LB scopes.

#3 Ettu

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Posted 24 January 2013 - 01:41 AM

Hi Don,
You're right about easier (JMI's offerings, and their upcoming GPS version too) but they cost money, and I've got a fully computerized Alt/Az GoTo set up that's been collecting dust un-used for 4-5 years now. And a 16" LB that doesn't have it, but could use it.

I see the Meade LX200 classic platform (minus the OTA) goes for $400-$500, which could go toward a JMI, but it's winter, everything is setting inside here where it's warm, and nothing ventured, nothing gained.

#4 Starman1

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Posted 24 January 2013 - 02:09 AM

Hi Don,
You're right about easier (JMI's offerings, and their upcoming GPS version too) but they cost money, and I've got a fully computerized Alt/Az GoTo set up that's been collecting dust un-used for 4-5 years now. And a 16" LB that doesn't have it, but could use it.

I see the Meade LX200 classic platform (minus the OTA) goes for $400-$500, which could go toward a JMI, but it's winter, everything is setting inside here where it's warm, and nothing ventured, nothing gained.

Huh?
The tripod plus mount plus fork arms for a 16" LX200 (minus OTA) should be in the thousands, not hundreds.
You are talking about un-forking a 16" SCT and mounting a 16" LB in the fork arms aren't you?

#5 Ettu

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Posted 24 January 2013 - 09:00 PM

Ahh... I see that the way I stated things should have been better. I knew what I meant, but I did not lay out the situation properly.

The LX200 classic platform that I want to adapt to a new use, is from a 10" classic.

Now I understand too what you were talking about. Thanks for recognizing the situation.

Fwiw, there's a fellow I've been speaking to who currently operates a 50lb load at a 14" moment with this platform. That gives me some reason to consider my proposal might work. But there's more doubt than surety in my mind that it will. So, I was wondering if anyone here actually has tried something like this? There are difficulties, but perhaps someone has actually worked the problem in 3D and living color.

At this point, I've decided to set up an adjustable load bar and scale up to (if it gets that far) the proposion.

Keith

#6 Achernar

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Posted 24 January 2013 - 10:41 PM

Are you looking to add digital setting circles or are you wanting to add a GOTO capability. If all you want is assistance finding objects, then I would look at getting a set of digital setting circles. If you want to go beyond that, there are options that would at the very least add tracking to the mix.

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#7 Starman1

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Posted 25 January 2013 - 01:26 AM

Ahh... I see that the way I stated things should have been better. I knew what I meant, but I did not lay out the situation properly.

The LX200 classic platform that I want to adapt to a new use, is from a 10" classic.

Now I understand too what you were talking about. Thanks for recognizing the situation.

Fwiw, there's a fellow I've been speaking to who currently operates a 50lb load at a 14" moment with this platform. That gives me some reason to consider my proposal might work. But there's more doubt than surety in my mind that it will. So, I was wondering if anyone here actually has tried something like this? There are difficulties, but perhaps someone has actually worked the problem in 3D and living color.

At this point, I've decided to set up an adjustable load bar and scale up to (if it gets that far) the proportions.

Keith

OK.
Well put it this way: Even if you re-manufactured the fork arms to accept the much wider width of the 16" LB, there is no way the mirror box would clear the base and there is no way the mount could handle the weight. Period. No reason to even day-dream about this one. You would need at least the tripod and mount of the 14" LX200 to begin to handle the weight of the OTA and even them the scope wouldn't clear the base without lengthening the arms. AND, the eyepiece height would require a BIG ladder to reach it.
Not even the slightest bit practical.

The JMI system is the cheapest way to make a 16" LB a Go-To scope.

However, you really only need to use a computer to find things, and you could add Digital setting Circles to enable the scope to find any object. With a little ingenuity, this could be done for ~$500. And if you want tracking, the JMI Train'N'Track or an equatorial platform under the scope.

Yes, all of these options cost money, but a pittance compared to putting the scope on another mount or in a new housing that's already Go-To.

#8 Jon Isaacs

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Posted 25 January 2013 - 01:23 PM

Fwiw, there's a fellow I've been speaking to who currently operates a 50lb load at a 14" moment with this platform.



Which "moment" are your referring to?

The 16 inch Lightbridge OTA weighs 74 lbs and is approximately 6 feet in length. That's a lot of inertia.

It might be possible to adapt the drives and electronics from a LX-200 to a 16 inch Lightbridge and make it work but the actual mount itself is not robust enough or of a proper size to be capable of handling a tube that large.

Is that what you are wondering about, removing the drives and mounting them to a 16 inch Lightbridge??

Jon

#9 Ettu

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Posted 26 January 2013 - 12:48 AM

Hi Jon
Yes, that's what I have in mind.
As you said it is over 70 lbs. On the mirror side I get about 60 lbs 16" from the fulcrum point, and about 18 lbs (with EP and finder) 48" on the spider end. Pretty close to a 1/3 ratio by length and load

So, I removed the fork arms and bolted on a 6' load bar horizontally, divided 1 to 3, to the base, and loaded the ends in a ballanced way at 32, 52, 72, and 96 lbs. It started, swung, and stopped without incident. PROVISO: I didn't try any slew speed above the lowest, #2, which incidentally is the same as the "Find" speed. The mA indicator spikes to a little over 1/2 at the beginning and end of each move, and at 52 lbs and above, the whole sheebang rocks within the limits of the backlash and dampens to rest btwn 3-5 cycles. At less than slew rate #2 or "find" (guide & center) the unit handled all the weights the same as empty (12 lbs) balanced load bar.

Once on target, I am confident now that it'll handle the LB 16" with ease. I'm not at all satisfied that my worries are over using the GoTo capability.

Any thoughts on keeping the alt/az GoTo capability but eliminating the risk of damage?

Keith

#10 Jon Isaacs

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Posted 27 January 2013 - 08:40 AM

I am assuming you are planning on using the stock base and somehow bolting the drives to the base. You could use a toothed belt to to take some of the shock.

One issue with using old LX-200 mounts for a project like this is that they are obsolete and when the circuit board or the hand controller fail repair/replacement becomes a big problem. You will have a lot of time and energy invested.

Jon

#11 Ettu

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Posted 27 January 2013 - 11:03 AM

Hi Jon,
Thank you for the suggestion. Yes, I too am concerned about the torque on the gear, which is transfered to the worm and its mount. The mount of the worm is the weak spot, and if it breaks, it's a big problem. The obsolete nature of the classic is a potential problem, but only if this whole project is very successful! THEN if something breaks or fails it'll be a problem. For now from my point of view, I'm having fun tinkering and testing, and as a bonus, so far, so good.

One thought to reduce the stress of an azimuth move is to have the OTA upright. Which also avoids the OTA hitting something, or me hitting it during a move. It turns out that will be pretty easy to make possible. I've already tackled the altitude adaptation, about which I've cut and pasted from another forum to below. I hope the format translates ok. I'm going to tackle the azimuth next.

--- In LX200@yahoogroups.com, "keithnk_m42" wrote:
I decided to tackle the altitude control next, to see how and if that was going to work. It all fell into place surprisingly well.

I bolted a 3/8" pin to and sticking out from the center of the aluminum casting of the LB16. (that is attached to the OTA and supports it in the wood side saddle). The LX200's OTA arm already has a 3/8" hole in its center, so it slipped onto the pin. The centers of rotation were now lined up. After that it was a matter of connecting the LX200" OTA arm to the casting of the LB, and the fork arm itself to the frame of the LB's wooden side. Testing was next.

The testing went pretty well. It handles the OTA easily through slew rate #2. According to the mA lights, it draws about 200 mA at rate #2. One nice thing, and compared to my earlier Azimuth test, this time I could see the worm and gear and how they reacted to the load. And yes it is a load to start and stop at #2, but imo the motor, worm, and gear don't flex any more than a fully loaded SCT (camera, focuser, guide scope, guide CCD, counterweights, dew sheild) at full speed.

The guide or tracking rate did not work as well. I left the friction fit between the LB's aluminum castings and the saddles they set in. Although the scope moves well at other speeds, at tracking rate, in some parts of the sky, it can't over come the initial friction to get going, and stalls. This was true when pointing south, where the altitude moves are the slowest. When pointing in the E or W it tracked along okay. The nice thing about the friction, is that it eliminates the backlash bounce.

Keith

#12 neotesla

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Posted 27 January 2013 - 12:00 PM

Why not this as a consideration...

http://stellarcat.co...servocatjr.html

#13 Ettu

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Posted 22 April 2013 - 11:12 PM

Okay, After some encouraging capacity testing, I went ahead and adapted the parts from a deforked LX200 Classic to computerize a Meade 16" Lightbridge dob. It works quite well. Some pictures of how I did it probably describe it best,
http://www.willowber...et/keithnk_m42/
Click on the appropriate thumbnail in the "My Stuff & A Frame" section.
I still use an old web page editor, so some people tell me they have to click on "compatability view" in their browser for the web page to display proberly.
But I am really pleased.
It is really nice to be able to Go To celestial objects, and have it track without having to be tended.
I've used and tested it now for a half dozen nights, and I love it. It's going with me to the TSP this upcoming week. I'll be staying at the Ft Davis Tx state park though rather than on the TSP grounds. It'll get a work out.

Keith (Ettu)

#14 sn1987a

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Posted 24 April 2013 - 01:26 AM

Why not this as a consideration...

http://stellarcat.co...servocatjr.html


Yep thats the way I went, just ordered from Gary and Jean, should arrive any day now. Installation will be fun. I totally modified my 16 Lightbridge. New Suchting mirror, rebuilt mount, feathertouch focuser, protostar secondary ect. Cost is $1500 for the StellarCat but well worth it as the StellarCat is very good especially hooked up with Argo Navis, theres no going back. :D

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