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Supplemental focuser for an LX200 that I don't own

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#1 aeajr

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Posted 21 July 2019 - 09:13 AM

I have the privledge of using an LX200 GPS 14" at the Custer Observatory.  I use this mostly for outreach at the Observatory.   

 

The systems uses a typical SCT course focusing knob.  Fine focus is provided by a motor driven system that is operated by the hand set.   I really dislike this personally and it makes it had for me to allow people to focus as they come through the line to look at Saturn or whatever.

 

I am looking for something like a helical focuser that I can put into the diagonal that would allow easy fine focus by turning the focuser, or the eyepiece that is locked into this helical focuser.

 

Having it available for 2" eyepieces would be nice, but if it only worked with 1.25" that would be acceptible. 

 

Any suggestions?  I would prefer to keep this as far under $100 as possible as I don't own the scope.   This is strictly for the benefit and convenience of the public.



#2 Migwan

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Posted 21 July 2019 - 09:30 AM

Hey Ed, something like this might be what you want.  It's sold, but you could put in a want ad.  With explanation of why, you may well find one.    Think you want to put it between diagonal and visual back.  Luck be with you.  jd

 

Forgot the link.


Edited by Migwan, 21 July 2019 - 09:31 AM.


#3 aeajr

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Posted 21 July 2019 - 10:28 AM

Would that slip into the current diagonal?  I don't own this scope so I can't modify it in any way.  

 

What i have found is this, which looks like it should work but the discussion has been about Dobs, not SCTs. But I can't think of why it would not work. 

https://www.cloudyni...-speed-focuser/



#4 decep

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Posted 21 July 2019 - 12:33 PM

I own and use a GSO 2-speed SCT Crayford focuser with my 12" LX200.  It screws directly into the SCT visual back.  You can then use the focuser in the SCT for your "macro" focus and then just deal with the Crayford for your fine focus.

 

For $100 (maybe a little less) you could get a new single speed GSO crayford focuser.  For ~$130, a dual speed focuser could be had.  Both of these options will have 1.5" of focuser travel.

 

The only warning I have for you is if you utilize a Peterson EyeOpener.  I am not sure the EyeOpener is compatible with the SCT Crayford focuser (I have not tried the combination).  If you have the EyeOpener, you might have to revert back to the standard visual back.

 

 


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#5 aeajr

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Posted 21 July 2019 - 12:48 PM

I own and use a GSO 2-speed SCT Crayford focuser with my 12" LX200.  It screws directly into the SCT visual back.  You can then use the focuser in the SCT for your "macro" focus and then just deal with the Crayford for your fine focus.

 

For $100 (maybe a little less) you could get a new single speed GSO crayford focuser.  For ~$130, a dual speed focuser could be had.  Both of these options will have 1.5" of focuser travel.

 

The only warning I have for you is if you utilize a Peterson EyeOpener.  I am not sure the EyeOpener is compatible with the SCT Crayford focuser (I have not tried the combination).  If you have the EyeOpener, you might have to revert back to the standard visual back.

Thanks.

 

For clarification, this is strictly for visual use, if that matters.

 

So I would remove the current electronic micro focuser an put it aside and replace it with one of these?

 

Is this what you are talking about?  I could not find it on Astronmics.

https://agenaastro.c...-telescope.html

 

According to the notes at AA:

 

The 2" focuser barrel features a brass compression ring and can accept standard 2" refractor-type diagonals and other 2" accessories (Note that the use of this focuser converts your telescope's rear SCT thread to a 2" visual back. As a result you will not be able to use an SCT-type diagonal with this focuser; you will need a refractor-type diagonal instead). Also included is a 1.25"-2" adapter with brass compression rings and threads to accept standard 2" filters. This deluxe model features a 360-degree rotatable ring that allows you to orient the focuser (and hence your diagonal/eyepiece) to the most comfortable viewing position.

 

Please note that some larger Meade and Celestron SCTs (11" and larger) have a larger 3.25" rear thread, so please make sure that you have an adapter that reduces that larger thread to the smaller 2" SCT thread. If you have a standard 1.25" SCT visual back, all you need to do is unscrew the visual back and screw on the SCT Crayford focuser in its place.  The focuser is shipped in a foam-fitted box.

 

 

So, I would have to replace the diagonal as well, if I read this properly.  And likely would need some kind of adapter for the back of the 14" LX200 to make this work.   Does that make sense?  

 

I have no experience with SCTs and this looks to be way beyond my $50 budget to enhance someone else's telescope.   If I did this, likely I would have to get permission to do the modification. 

 

 

 

I don't know what a Peterson eyeopener is or what is does so I doubt it is involved. 



#6 decep

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Posted 21 July 2019 - 01:38 PM

Take a look at Figure 6 on page 13 of the LX200 GPS manual:  https://www.meade.co...al-size-1-5-mb/

 

The SCT Crayford focuser screws directly to rear cell adapter (A).  You can gen put your diagonal directly into the Crayford focuser.  It actually removes quite a bit from the optical train.  smile.gif

 

The Peterson EyeOpener is a replacement for the rear cell adapter (A) which has a larger opening so the microfocuser © attaches directly to the rear cell without the (B) adapter.  Some revisions of LX200 12"+ start vignette with 2" eyepieces above 40-50mm.  The Meade 56mm super plossl is specifically mentioned.  https://petersonengi....com/eyeopener/


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#7 aeajr

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Posted 21 July 2019 - 02:04 PM

Thanks.  I will keep this in mind as an option. 




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