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GoTo mount for classic OTA - Help!

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#1 Jimmy2K63

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Posted 01 May 2009 - 08:11 AM

I am considering the purchase of a GoTo mount for my Cave 10" f/5 OTA. I've considered adding GoTo to my existing Astrola mount as well, but I sure like the idea of a whole new mount with a simple hand controller and a tripod for portability....such as the CG-5. :-)

Or perhaps a simple GoTo Dobsonian mount would suffice as well. At this point, the important thing is the ability to slew and allow visual astronomy to be performed with it. The original Astrola mount is extremely stable and completely amazing as an observatory mount, but that's not what I am after.

I'd like to hear what others have done with larger newtonians and GoTo and help get pointed in the right direction - no pun intended.

#2 tim53

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Posted 01 May 2009 - 08:23 AM

I would think that the Cave OTA would crush a cg-5 into the dust! :grin:

With a full-thickness mirror and fiberglass tube, it's nothing like the lightweight OTAs that Celestron and others put on those mounts - which are underkill themselves, IMHO.

You might look at a Sidereal Technology goto servo kit for the Astrola mount. You can do it yourself for about $800, or pay to have it done by someone like Lenord Stage at gototelescopes.com. I think his website even has a pic of a converted Cave mount.

Please don't make a dob out of a Cave. Somehow that seems wrong to me (seriously, do what you want, I'm just ranting! ;))

-Tim.

#3 Jimmy2K63

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Posted 01 May 2009 - 08:29 AM

Thanks Tim. I did email Leonard and am waiting to hear from him STILL. For the price of converting it, I can buy a GoTo portable scope.

Still would be nice to have these optics on a GoTo mount. At least I know what the OTA is capable of. No I don't want to make this into a Dob, but if I could get a Dob mount for this OTA I could still also use it on the GEM at home, the Dob out on "the road."

#4 Charlie Hein

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Posted 01 May 2009 - 08:35 AM

Would installing DSC's be an opption here? It's not Go-to but you would be able to locate objects easily.

#5 tim53

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Posted 01 May 2009 - 08:58 AM

you can also do quite well with the stock setting circles. Most people don't even think of this option.

Cheap, too!

-Tim.

#6 Quintessence

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Posted 01 May 2009 - 09:03 AM

I agree with Charlie. I think a good DSC installation is a practical idea that will not destroy the character of the original mount and telescope -- and will allow you to find just as many objects with essentially the same speed and ease of a GOTO mount, probably with more reliability, less maintenance, less noise, and less cost. To me, this is a no-brainer.

#7 Jimmy2K63

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Posted 01 May 2009 - 09:10 AM

Setting circles are only accurate if the scope is precisely polar aligned are they not? That's not real practical for a portable usage situation. Do the DSC's allow you to "compensate" for a lack of precise polar alignment?

#8 tim53

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Posted 01 May 2009 - 09:49 AM

You can do pretty well by pointing the OTA to 90 degs declination and adjusting the mount to put Polaris in line with the OTA by just sighting up the tube at the star. I used to do this with my old Optical Craftsmen Discoverer mount (which has much smaller setting circles than the cave), and objects were always in the finder field of view when I used the setting circles.

-Tim.

#9 Quintessence

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Posted 01 May 2009 - 11:50 AM

With two-star alignment, DSC units compensate for poor polar alignment. As far as pointing is concerned, GOTO mounts have no advantage over DSC aiming. Pointing accuracy is generally a function of factors like orthogonality of the axes, precession in the axes, sag in the mechanical structures, encoder resolution, concentricity of the encoders with respect to the axes, and other such geometric issues.

#10 jgraham

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Posted 01 May 2009 - 08:06 PM

It can be done, but I suspect the weight would be a problem. If you're going to try this be sure the weight of your telescope is within the weight limits of the mount. This is my homebuilt 8" f/6 Newtonian on my LXD75. I also built a lightweight 10" f/5.6 specifically for this mount, but I haven't tried it yet; it just looks to big for the mount.

Attached Files



#11 Project Galileo

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Posted 01 May 2009 - 09:24 PM

Cool rig.

#12 Chris Curran

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Posted 02 May 2009 - 05:42 AM

Jimmy,

As many have mentioned, the least expensive route you can take is to upgrade the electronics on your current mount. However, if you're planning up buying a new mount, a CG5 won't do it. I have a 10" f/6. On the Tak EM-200 mount it is barely usable for visual use. It works, but is wobbly:

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When I slap it on the 1200, it's quite usable:

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Big newts like big mounts. You're probably better off just upgrading your current mount, unless you're ready to fork out some serious cash...






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