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Is it possible to upgrade the focuser in my Meade 8" ACF?

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11 replies to this topic

#1 Ballyhoo

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Posted 10 November 2019 - 05:14 PM

I notice when doing imaging it loses focus rather easily.

 

It is the LXD75 model.


Edited by Ballyhoo, 10 November 2019 - 05:15 PM.


#2 scadvice

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Posted 10 November 2019 - 05:56 PM

It might be easier to answer if we knew which OTA.. Whoops!  I see you did in the title.ohmy.gif

 

Sorry, I have no knowledge about that scope...


Edited by scadvice, 10 November 2019 - 06:10 PM.


#3 Jesus Munoz

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Posted 10 November 2019 - 10:10 PM

Maybe an external focuser solves your problem.  How often is "rather easily"?

 

Regards



#4 laixiaolue

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Posted 10 November 2019 - 10:42 PM

Did you try the mirror lock?



#5 bbqediguana

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Posted 11 November 2019 - 07:11 AM

Did you try the mirror lock?

I don't think the LXD75 has a mirror lock - I think that's just on 10" and higher LX200's.



#6 bbqediguana

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Posted 11 November 2019 - 07:19 AM

I notice when doing imaging it loses focus rather easily.

It is the LXD75 model.

Can you describe what you mean by losing focus rather easily? Does this happen visually as well?

The focusing mechanism is pretty simple - the primary mirror slides up and down on the baffle tube - it has a little arm out it's right side (when viewed from behind), and the focuser knob is attached to that arm with essentially a bolt. As you turn the focuser knob, it turns the bolt which moves the mirror like a nut on a bolt.

So, there could be something loose in the focuser mechanism. I installed a Peterson EZ Focus kit on my 8" Meade to make the focusing smoother and more accurate - the instructions show how to take apart the focuser:

Otherwise, you could consider using an external focuser like a GSO Crayford focuser:

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

It might be good to try and determine why your scope is losing focus - is it the focusing mechanism? Is it the primary mirror shifting on the baffle tube? Is it a loose secondary mirror?

I hope this helps.
Thanks!

Rick

Edited by bbqediguana, 11 November 2019 - 05:08 PM.


#7 Bill Barlow

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Posted 11 November 2019 - 10:20 AM

You could purchase a Meade upgrade focuser kit from Peterson Engineering.  I installed one on my LX85 OTA and it completely eliminated any focus/image shift.  Only costs about $30.

 

Bill


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#8 Winks

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Posted 11 November 2019 - 11:26 AM

I put a Moonlite focuser on mine. Excellent upgrade.  Also, the 8" F/10 has mirror locks.


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#9 Ballyhoo

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Posted 11 November 2019 - 01:30 PM

Lots of great ideas above. It loses focus after an hour or two of imaging. For example I left it alone the other night, it was imaging the Horse head, then as it got early in the morning I had it switch over to Bodes using SGP ( I was not there to see it though) and all of bodes was OOF. Maybe what I would really need is auto-focus, but on this old OTA, such a mechanism would cost more than the worth of the OTA. 



#10 Whichwayisnorth

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Posted 11 November 2019 - 01:49 PM

That could be because your OTA changed its focus point as the temperatures changed.  Both the mirror and the tube itself expand and contract as the temps change.  This is why many auto focusers have temperature compensation and you can set a focus position based on the current temperature.  No way around your problem (as described) except adding an external focuser and having it refocus every so often and also based on temperature changes.

 

I like Moonlite focusers for this.  CSL 2.5"  with 3.25" mount and you can get it in Meade Blue.


Edited by Whichwayisnorth, 11 November 2019 - 01:51 PM.

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#11 bbqediguana

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Posted 11 November 2019 - 05:15 PM

ATTENTION MODERATOR

ATTENTION JIM T aka Viking 1

You have posted a link to a copyrighted document. PLEASE remove this link from this posting and remove the document from the web.

Pete Peterson
Peterson Engineering

 

[EDIT - mystery solved! Jim is the guy hosting the PDF of the instructions. I've emailed Jim asking him to take it down and I've cc'd Pete on that email. Hopefully that will take care of this whole situation.]

 

[EDIT 2 - situation resolved! I reached out to the owner of the site (an astronomer named Jim!) and he took the PDF down and we let Pete know. It's all good in the hood!]

 

Hi Pete,

I apologize for that. I didn’t realize the instructions to your product could not be publicly posted. I have removed the link but I cannot take down the content as I don’t host it. I just linked to an existing PDF on the web. You should contact whomever owns karmalimbo.com as they host the PDF.

Also, here’s a tip: use the “notify moderator” button instead of “shouting” in the thread. Or you could have PM’d me directly.

Again, sorry about posting that link.

Thanks!

Rick


Edited by bbqediguana, 12 November 2019 - 07:22 AM.

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#12 carolinaskies

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Posted 11 November 2019 - 06:11 PM

Hi Pete,

I apologize for that. I didn’t realize the instructions to your product could not be publicly posted. I have removed the link but I cannot take down the content as I don’t host it. I just linked to an existing PDF on the web. You should contact whomever owns karmalimbo.com as they host the PDF.

Also, here’s a tip: use the “notify moderator” button instead of “shouting” in the thread. Or you could have PM’d me directly.

Again, sorry about posting that link.

Thanks!

Rick

I'm sure PE would make such documentation available for anyone who has their upgrades with a simple call/email.  
I have a 16yr old 10" SCT newly acquired which has a few PE add-ons.  I'd hate to not have access to documentation for reference as necessary. 


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