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Thread: Lunt LS50 focuser issue

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    Default Lunt LS50 focuser issue



    Some time back I had my original focuser replaced by Lunt with a new one. They sent it to me and had me swap it out. I have been using it for about 4 months, but lately noticed that there was a gap between the focuser and the etalon. I tried to turn the focuser body but it is locked in place, it cannot be turned in either direction (the focus ring works fine it is the body of the focuser). There appears to be no way to remove it without a wrench.
    I contacted Lunt and they said to remove the little screw that holds the diagonal holder tube in place (not the one that holds the diagonal) and then I could turn the focus ring slightly to close the gap. I did that and got the gap to close but now instead of bottoming out at "0" the infocus ends at "3". I can work with that because I usually look in the EP as I focus, but for a $900 scope it should be better than that.

    I have thought about a Borg focuser, I know Lowjiber and others replaced theirs. I have a couple questions about them and then a question about how to remove a stuck focus assembly.

    The Borg says it is a non-rotating focuser - how do you focus is it a push pull sort of focuser rather than rotating a focus ring?

    How would you recommend removing the focuser that is stuck?

    I hate the thought of sending it back to Lunt before winter makes it less pleasant to observe.
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    Default Re: Lunt LS50 focuser issue

    Ben, maybe pose the question in the Solar Viewing & Imaging group ? The guys and girls there may be able to help you straight away, and your question would be more visible to the "specialists" so to speak. Like you said, several members have replaced the stock Lunt 50 focuser. I'm sure they can help.

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    Default Re: Lunt LS50 focuser issue

    Ben, I've heard a couple of stories about the standard Lunt focuser getting stuck and what not. Mine worked ok but I changed it to a Borg to assist focusing for imaging on the advice of others. The Borg works just like the Lunt but is a bit smaller and seems better quality. By 'non rotating' they mean whatever is attached ie. the diagonal, won't rotate when you focus, that's all.

    If you do decide to get a Borg you will also need an adaptor because the threads from the standard focuser are a different size to the Borg. I searched all over for this part and someone advised Starizona as they are aware of the problems with the LS50 focuser. I think they had to get the part made to order and it did take a while.

    My standard focuser just unscrewed with not much effort and with the manufactured part the Borg screwed in nicely.

    Here's a couple of pics showing the Borg in place compared to the Lunt focuser.

    I also need a better phone, the pics are a bit off.

    IMG_20160519_183849_edited.jpgIMG_20160519_183904_edited.jpg
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    Default Re: Lunt LS50 focuser issue

    I see you Borg has a slight gap between the focuser and the etalon, I tried to fix that with my Lunt focuser and instead of zeroing at zero it was zeroing at 6, so I tried to get it back to 0 the closest I could get it was to zero a 3 but then it would focus with any EP. So I tried it again and got it to zero at 6, so 6 is my new 0
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    Default Re: Lunt LS50 focuser issue

    My advice would be to get the Borg!! When I swapped mine out, it was awesome. Much smoother and focused better for AP as well. Well worth it. If you decide to, contact Starizona. They know about the issue.
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    Default Re: Lunt LS50 focuser issue

    Quote Originally Posted by Ben Cartwright SASS View Post
    I see you Borg has a slight gap between the focuser and the etalon, I tried to fix that with my Lunt focuser and instead of zeroing at zero it was zeroing at 6, so I tried to get it back to 0 the closest I could get it was to zero a 3 but then it would focus with any EP. So I tried it again and got it to zero at 6, so 6 is my new 0
    Yes, I only noticed that when I dug it out to photograph it for this thread.

    To be honest, I never really took notice of the numbers on the focuser, I just adjusted it without taking note. I will leave it as it now seems fine for imaging.
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    Default Re: Lunt LS50 focuser issue

    I contacted Lunt about the fact that I cannot remove the focuser and asked what I should do since I don't want to mess up the threads on the Etalon
    Home obs pad has Bortle 7.5-8.0 sky, Lunt LS80DS, LS50DS, Quark Chromosphere
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    Default Re: Lunt LS50 focuser issue

    I replaced three of those junk Lunt 50 focusers before coming to my senses and slam-dunking a Borg on there. (I think I was the first on this forum to do so.)

    Starizona has several of those adapters made-up ahead of time... should be no problem getting one.

    Regards the focuser being "stuck", you can't hurt the etalon. The Lunt focuser simply unscrews in the traditional fashion of "righty tightey, lefty loosey".

    Regarding the "gap" between the focuser and the etalon... big deal in my opinon. No light is going to get in anyway, so no-harm-no-foul.

    As far as where it "zeros"... again, I can't see that it matters. You know what the "travel" is and where the center is, based on that number. Just put it in the center-of-travel; pull the BF out to where you have it "close"; and finish adjusting the focus.

    Once I determine the distance the BF needs to be retracted, I take a wooden paint stick and make a go-no-go gauge. That way, my wife can set up the scope for visual without any hassles (or help from me.).

    I suggest calling Starizona and ordering the Borg focuser and the adapter.



    Clear Skies
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    Default Re: Lunt LS50 focuser issue

    John
    I will try to get the focuser out again. As I tried to turn it the etalon started turning as well. I have a buddy who is like Arnold big time weight lifter, he may be able to turn it.
    Lowjiber and Marcusandrew like this.
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    Default Re: Lunt LS50 focuser issue

    Ben - only just seen this thread from last year - I have exactly the same problem with my Lunt 50 focuser. I've bought a Moonlite to replace the stock helical, but can only unscrew it half way before it jams tight. How did you eventually solve the problem?
    Takahashi FC-100DC, Edge 8, Equinox 80ED, Lunt LS50.

 

 

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