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Focuser Upgrade for my Lunt LS50 H-Alpha scope

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#1 saguaro

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Posted 23 April 2015 - 03:16 PM

I love my Lunt LS50 H-Alpha scope, but I've never been happy with the supplied helical focuser. The focuser drawtube sags with just the weight of the blocking diagonal, and there is some slight back-and-forth "play" in the drawtube. The sag and play can be mitigated by locking the focus knob on the focuser, but it means more fiddling with the focuser than I would like and it's inconvenient to have to lock and unlock the focus knob all the time. Also, due to the sag in the drawtube, the scope's pressure tuning sweet spot is positioned off-center in the field of view (slightly to the lower left of the view). Again, locking the focus knob straightens out the drawtube and helps center the sweet spot, but I find it annoying. When I told Lunt about the focuser issues, they told me the behavior was considered "normal". :)

 

After talking it over with Scott at Starizona, we settled on the Borg 7315 non-rotating Helical Focuser as a replacement. There really wasn't much choice since the scope doesn't have enough back-focus to go to anything like a crayford-style focuser such as a Feathertouch. Starizona made me a custom threaded adapter that allows the Borg focuser to thread into the Lunt scope. Total cost: Borg 7315 focuser $109 and custom threaded adapter $50. Some may consider this to be an extravagant expense, but I am so happy with the Borg focuser that I consider it money well spent.

 

Here are details on the Borg 7315 focuser: http://www.sciencece...s/html/7315.htm

 

It is a very smooth operating focuser, with no play in the drawtube. I immediately noticed that the scope's sweet spot was more centered in the field of view, for both visual and imaging use. No more fiddling with the focus lock! The Borg focuser has the additional advantage of having a slightly shorter light path (just a few millimeters) versus the supplied focuser. I can still focus with my Lunt zoom eyepiece across it's entire zoom range. And as a bonus, the Baader Mark III zoom eyepiece also comes to focus without having to adapt it to use a slightly shorter light path (as I did with the supplied focuser). (See my post here for the Baader zoom modification: http://www.cloudynig...4#entry6476959)

 

The major drawback to the Borg helical focuser is that it is much more of a light-duty focuser than the supplied focuser. With the Lunt zoom, which is a fairly lightweight eyepiece, the focusing action with the Borg is not as smooth as when there is a lighter-weight fixed focal length eyepiece being used. The focuser also operates fairly smoothly with my small Skyris 132m camera mounted to the blocking diagonal. The much heavier Baader zoom eyepiece puts more demands on the Borg focuser, but I love using the Baader zoom so I can live with lifting the eyepiece end of the blocking diagonal a little bit to take some weight off the focuser while I'm focusing.  ;)  I can switch back to the supplied focuser whenever I need to use a heavier accessory, so I'm OK with this.

 

Here is the Borg Helical Focuser 7315 mounted on the scope, with my Skyris 132m camera attached to the blocking filter. To adapt the camera and achieve focus, I use a Starizona T-to-C adapter mated to a 10mm T-thread extension tube.

borg 7315 helical focuser.JPG

 

Starizona has several of the Borg custom threaded adapters for the Borg focuser, so they are available if others are interested in going this route. If you are interested, it's best to ask for Scott.

 

 

 



#2 Markovich

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Posted 24 April 2015 - 01:42 PM

Nice! The focuser is definitely the weak element on an other fine scope. On my Lunt 50, the focuser is sufficiently stiff enough to move the image during focussing. 



#3 Martin Hoyle

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Posted 25 April 2015 - 02:06 PM

It does Look Neat

 

It's All About Location & Owning Your Photons & Some Philosophy & Cosmology for Those of Us with Some Theoretical Physics & Other Twitter Interests  :)

 

Martin



#4 saguaro

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Posted 26 April 2015 - 10:22 AM

To anyone considering this "upgrade", you should know that the Borg focuser has a shorter light path by 5mm versus the Lunt-supplied focuser, but it has the same 10mm of travel. So the focus range with the Borg is from 45mm to 55mm (versus 50mm to 60mm for the supplied focuser.). The shorter light path for the Borg may be beneficial for achieving focus with some eyepieces (such as the Baader Mark III zoom) and perhaps some cameras. If you need an extension to achieve focus, you can always use T-thread spacers to get the extension you need. The eyepiece end of the Borg focuser has T-threads on it, and the Lunt blocking diagonal also uses T-threads on both ends.

 

Here is a photo showing the supplied focuser (removed from the scope) and the replacement Borg focuser attached to the scope for comparison.

 

borg focuser and lunt focuser.JPG

 

Also, before "upgrading" I would encourage anyone who has issues with the supplied focuser to contact Lunt and share your feedback with them. Lunt needs to hear from their customers if they are not happy with the focuser. Perhaps it will encourage Lunt to provide a better focuser with the LS50.


Edited by saguaro, 26 April 2015 - 11:38 AM.


#5 swsantos

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Posted 26 April 2015 - 10:43 PM

The stock focuser has a compression ring which holds the diagonal whereas the Borg has, I believe, two thumbscrews which hold the diagonal. Does that concern you?



#6 saguaro

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Posted 26 April 2015 - 10:58 PM

The stock focuser has a compression ring which holds the diagonal whereas the Borg has, I believe, two thumbscrews which hold the diagonal. Does that concern you?

You're correct - no brass compression ring on the Borg focuser. However, after using the Borg focuser, I can see that it centers the blocking diagonal better than the stock focuser, so no, it doesn't concern me. And since the blocking diagonal is always inserted in the focuser, I have no concerns about any potential marks on the diagonal nosepiece from the thumb screws. Bottom line is that for me, I'm glad I switched to the Borg focuser.

 

Of bigger concern to me is that the Borg focuser is designed to carry less weight than the stock focuser, but I can live with that, since I can always switch back to the supplied focuser if I need to use a heavier accessory.



#7 swsantos

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Posted 27 April 2015 - 08:13 AM

The only three things I would put on in are the Lunt Zoom, Nagler 3-6 Zoom and Meade HD-60 since I do not do imaging is the Borg sufficient for those? The Lunt Zoom is probably the heaviest. I am wondering is the Borg focuser is a worthwhile upgrade for visual use only. As far as the shorter light path is concerned the T threaded ring that comes with the scope can be attached to the T threads on the diagonal to re lengthen the light path. If Starizona created the adapter I wonder if they can make one that restores the light path length? I had to get a spacer ring thinner that the one supplied for the diagonal as it is for all three of those eyepieces to be able to all reach focus given the stock focuser's range.

 

You are right about the diagonal living in the focuser and its good to hear the diagonal is better centered with it than the stock focuser.



#8 saguaro

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Posted 27 April 2015 - 09:30 AM

The only three things I would put on in are the Lunt Zoom, Nagler 3-6 Zoom and Meade HD-60 since I do not do imaging is the Borg sufficient for those? The Lunt Zoom is probably the heaviest. I am wondering is the Borg focuser is a worthwhile upgrade for visual use only. As far as the shorter light path is concerned the T threaded ring that comes with the scope can be attached to the T threads on the diagonal to re lengthen the light path. If Starizona created the adapter I wonder if they can make one that restores the light path length? I had to get a spacer ring thinner that the one supplied for the diagonal as it is for all three of those eyepieces to be able to all reach focus given the stock focuser's range.

 

You are right about the diagonal living in the focuser and its good to hear the diagonal is better centered with it than the stock focuser.

 

Is it a worthwhile upgrade? I guess it depends on how much you like or dislike the stock focuser. I have lived with the stock focuser for about 5 months, and I was prepared to live with its quirks since the scope is otherwise wonderful and I have learned how to "cope" with the finicky focuser. I guess you have to decide for yourself. Perhaps your stock focuser works well enough for your needs if you only use it for visual.

 

Weighing 5.5 ounces, the Lunt zoom is at the limit of the Borg focuser's capacity to turn smoothly. To take off some of the weight of the eyepiece, I use a finger of my left hand to lift the eyepiece end of the diagonal very slightly, and then I can focus smoothly either in or out using my right hand. Alternatively, if I start by racking the focuser out all the way I can then smoothly rack it in to focus with just one hand. Using a shorter fixed focal length eyepiece such as my Televue 10mm smoothie plossl which weighs about 2 ounces, the focuser handles it well. So if you stick with eyepieces less than 5 ounces, the Borg focuser should handle them with no problems.

 

If you need to re-lengthen the light path to match the stock focuser's light path, you can certainly ask Scott at Starizona if they will make you an adapter that incorporates the longer light path, as long as you tell them how long you need the adapter to be and find out how much it will cost. Alternatively, you can simple back the diagonal out of the focuser a few millimeters to get the longer light path you need, and then use the focuser to fine tune your focus (you can do this with the stock focuser as well if you need a few more millimeters of light path). Hope this helps and I'm happy to answer any questions.



#9 nickatnight

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Posted 28 April 2015 - 10:52 PM

The only three things I would put on in are the Lunt Zoom, Nagler 3-6 Zoom and Meade HD-60 since I do not do imaging is the Borg sufficient for those? The Lunt Zoom is probably the heaviest. I am wondering is the Borg focuser is a worthwhile upgrade for visual use only. 

 

Hi swsantos. For visual only, as you're using a couple of zoom eyepieces, here's what I've been doing. I use the Lunt focus to get it roughly in the area of focus, and then use the fine tuning on the zoom eyepiece the get the focus right on the mark. The adjustments to the zoom are so slight, the image scale is pretty much right where I want it anyway. It sure is faster than fudging with fine tuning the Lunt helical focuser.  This doesn't help with fixed eyepieces or imaging though. Then you might want the saguaro upgrade method.



#10 swsantos

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Posted 30 April 2015 - 09:06 AM

Lunt replaced the original focuser for me without any problems as it was not acceptable. The replacement is much better and will probably be fine for me and visual use. Nice to know there are alternatives though should I decide to image of feel I need a better focusing experience.

 

Thanks,



#11 nickatnight

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Posted 02 May 2015 - 03:20 AM

After using the scope a bit more, I'm finding the play in the focuser is increasing. In fact, the play I'm getting exists even with the focus locked; the entire diagonal and outer focus mechanism wiggles a little left and right, so the eyepiece moves left and right when focusing. Very irritating. I examined the focuser, and the threaded inner barrel that the focuser is built off of screws in tight to the rear of the scope, and has no play. But everything built around the threaded inner barrel has play, which includes the compression ring for the diagonal, so the whole rear rocks a little back and forth. I don't see anything I can tighten to fix this. I'll give Lunt a call on Monday and see if I can get a replacement focuser. Seems to me there might be enough demand to get a 3rd party focuser built for this scope.


Edited by nickatnight, 02 May 2015 - 03:21 AM.


#12 swsantos

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Posted 06 May 2015 - 01:46 PM

https://www.cameraco...&cat=381&page=1

 

Here's an aftermarket focuser with a brass compression ring. I wonder if it would carry a heavier load than the Borg and if its an upgrade from the stock focuser?

 

Do you know what  the thread pitch type etc that the stock focuser screws into in case I give it a whirl and need an adapter?


Edited by swsantos, 06 May 2015 - 02:41 PM.


#13 saguaro

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Posted 06 May 2015 - 03:06 PM

https://www.cameraco...&cat=381&page=1

 

Here's an aftermarket focuser with a brass compression ring. I wonder if it would carry a heavier load than the Borg and if its an upgrade from the stock focuser?

 

Do you know what  the thread pitch type etc that the stock focuser screws into in case I give it a whirl and need an adapter?

 

The Arcturus focuser you linked to has some differences from the Lunt-supplied helical focuser. The Arcturus has an optical length of 45-56mm, while the Lunt focuser's optical length (my measurements) are 50mm-60mm. Also, the telescope-side threads on the Arcturus focuser are M31 with .45 pitch. The telescope-side threads on the Lunt-supplied focuser are M35 with .5 pitch (this information I got from Lunt directly). You would still need to get a custom adapter made.

 

The main advantage for me switching to the Borg helical focuser was that Starizona had one in their shop that I could actually look at. I had also looked for other options (as you are doing) but in the end, I decided to go with the Borg because I was able to see it in person, liked it better, and knew going in that it would not be as heavy-duty. There's always a chance that when you buy something without being able to evaluate it in person, you may be trading one set of issues for another. If you decide to order it, make sure you can return it if you find it is no better than the Lunt-supplied one.

 

However, if you are happy with the replacement focuser you got from Lunt, and you use the scope for visual, you'll have to decide if it's worth the extra expense.



#14 swsantos

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Posted 06 May 2015 - 03:33 PM

The "workaround" of having to lock the stock focuser to take up a little slop is probably not enough to get me to try another focuser on faith and the unknowns that go with that. The replacement from Lunt is indeed much better than the original one and I will probably not make a change. Maybe they will produce a better focuser in the future and make it available to us.



#15 nickatnight

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Posted 06 May 2015 - 10:23 PM

After using the scope a bit more, I'm finding the play in the focuser is increasing. In fact, the play I'm getting exists even with the focus locked; the entire diagonal and outer focus mechanism wiggles a little left and right, so the eyepiece moves left and right when focusing. Very irritating. I examined the focuser, and the threaded inner barrel that the focuser is built off of screws in tight to the rear of the scope, and has no play. But everything built around the threaded inner barrel has play, which includes the compression ring for the diagonal, so the whole rear rocks a little back and forth. I don't see anything I can tighten to fix this. I'll give Lunt a call on Monday and see if I can get a replacement focuser. Seems to me there might be enough demand to get a 3rd party focuser built for this scope.

 

Just to follow up on my comments on the focuser, I went to call Lunt around lunch time today and got voicemail. I left no message figuring I'd try back in the afternoon after lunch. In the meantime I had reread some threads on the LS50 focuser, and realized there is a screw hidden under the focus ring if you screw the focus all the way in one direction. That screw was loose, and wiggled in tune with my diagonal play issue. Once tightened back down, most of the play was gone. I'd say 15% remained, which I find acceptable. We'll see have it goes after a few weeks of regular use.


Edited by nickatnight, 06 May 2015 - 10:24 PM.


#16 swsantos

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Posted 07 May 2015 - 09:48 AM

That's exactly what the issue was with my original focuser, except it was defective to the extent that I could not even rack out the focuser enough to access that screw. The replacement they sent me racked out farther enough to expose that screw and tightening it indeed took up most, but not all, of the slop. The extra back focus was nice too. I wonder if there are others out there with focusers that to not rack out enough to tighten that screw.



#17 Markovich

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Posted 07 May 2015 - 11:54 AM

Will check mine tonight after work, kids activities...life..



#18 saguaro

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Posted 07 May 2015 - 05:16 PM

I picked up a replacement for my stock helical focuser at Lunt today. It is a huge improvement over my original focuser. The focusing action is much smoother and not as stiff. Also, there is much less "play" and "sag" in the focuser drawtube. I would encourage anyone who is not happy with their LS50 helical focuser to ask Lunt for a replacement. I still like the Borg replacement focuser better for lighter-duty use with my Skyris 132m camera, but now at least I have a decent stock focuser for use with heavier accessories such as my Baader Mark III zoom eyepiece.



#19 swsantos

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Posted 07 May 2015 - 11:02 PM

Does it have the number scale on it? The replacement they sent me does not. I dont really care about the number scale but would love to know if your replacement is different than mine and if it represents a "fix". My replacement, gotten a few months ago, is better than the original but still requires the focus lock to take up the slop. Does yours?



#20 saguaro

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Posted 08 May 2015 - 08:53 AM

Does it have the number scale on it? The replacement they sent me does not. I dont really care about the number scale but would love to know if your replacement is different than mine and if it represents a "fix". My replacement, gotten a few months ago, is better than the original but still requires the focus lock to take up the slop. Does yours?

 

My replacement stock focuser from Lunt does not represent a "fix". It's just a new focuser, with less slop than the one I've been using for 5 months. I will just have to wait and see if it still works better than my original focuser in 5 months from now. I described the issues I was having with the stock focuser and Lunt told me that the "workaround" is to lock the focus knob. I commented that I didn't like the idea of a "workaround" as the only solution. But that's the way it is and why Lunt can sell the scope at an "affordable" price point. I don't think the number scale makes any difference; my original one and this new one both have a number scale. It might simply be that there is some variation in the quality of how the focusers are made (but that's just a theory). The true test will be in how it performs after a few months of use.

 

I really enjoy using my LS50 despite the finicky focuser. The views I get with the double-stack setup are beautiful, 3D-like, and crisp. I can also get great full-disk images and 1.5x barlow images. Overall, the focuser is an annoyance but not enough to detract from an otherwise fantastic solar scope, in my opinion. Some might say, well, if you want a better focuser, you'll have to upgrade to a larger solar scope. For me, that means saving my pennies for an LS80 double-stack (and a larger mount to put it on). :)



#21 saguaro

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Posted 29 July 2016 - 08:59 AM

A news update!

 

As reported by Cometeer on Solarchat, and others on Stargazer's Lounge, there will shortly be two optional focusers for the LS50 to be offered by Lunt and Moonlite.

 

The Lunt Feather Touch focuser for the LS50 can be found on Lunt's website: https://luntsolarsys...-touch-focuser/

It is a single-speed (coarse focus) focuser, offered for $250. See the specs for details. It appears to offer a bit more in-travel (2mm) than the stock helical focuser, but I need to confirm this with Lunt directly.

 

The Moonlite focuser is not yet on their website https://focuser.com/. According to Cometeer, the Moonlite offering will be available in the next month, and will offer a single-speed focuser for $215 and a dual-speed for $315. Best to contact Moonlite for details.

 

Since my LS50 is serving me well, and since I don't plan to upgrade to a larger solar scope, I will definitely be getting one of these focusers. Not sure which one yet, though I'm leaning toward the Lunt offering if it does in fact offer a bit more in-travel.



#22 Cometeer

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Posted 29 July 2016 - 02:29 PM

A news update!

 

As reported by Cometeer on Solarchat, and others on Stargazer's Lounge, there will shortly be two optional focusers for the LS50 to be offered by Lunt and Moonlite.

 

The Lunt Feather Touch focuser for the LS50 can be found on Lunt's website: https://luntsolarsys...-touch-focuser/

It is a single-speed (coarse focus) focuser, offered for $250. See the specs for details. It appears to offer a bit more in-travel (2mm) than the stock helical focuser, but I need to confirm this with Lunt directly.

 

The Moonlite focuser is not yet on their website https://focuser.com/. According to Cometeer, the Moonlite offering will be available in the next month, and will offer a single-speed focuser for $215 and a dual-speed for $315. Best to contact Moonlite for details.

 

Since my LS50 is serving me well, and since I don't plan to upgrade to a larger solar scope, I will definitely be getting one of these focusers. Not sure which one yet, though I'm leaning toward the Lunt offering if it does in fact offer a bit more in-travel.

 

Cometeer here. Some more info.

 

I called Lunt and I was told that the 48mm of the Feathertouch was a measurement given to them by the folks at Starlight Instruments (Lunt doesn't actually know nor have the focuser, so I'll take Starlight's word for it). I wish Starlight did away with the threads on the drawtube because by doing so, they could further reduce the length of the focuser by another 3-5mm. My stock helical focuser is actually about 51mm since it doesn't thread in all the way into the scope. Your mileage may way.

 

As for the Moonlite, it will be available in all the colors they offer with their larger focusers. I was told by Ron that it will have 0.4" of travel which means it has less out-travel than both the helical and Feathertouch which have 0.6" of travel.

 

From the above info, the Feathertouch will have both more in travel and out travel than the Moonlight. Unfortunately Feathertouch isn't offering a dual speed option.


Edited by Cometeer, 29 July 2016 - 02:31 PM.


#23 swsantos

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Posted 30 July 2016 - 10:53 AM

The description of the Feathertouch on Lunt's website says it has nylon tipped set screws yet the photograph there has a compression ring. I wonder if that Is that an actual photo of the focuser on Lunt's site with the reference to the nylon set screw being an error?


Edited by swsantos, 30 July 2016 - 10:54 AM.


#24 spacetourist

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Posted 30 January 2017 - 01:57 PM

I disassembled my freely rotating/sticky/grindy focuser, a couple of days ago.

Main issues I found:

 

Under the rubber ring, there are 4 tiny grub screws, they were not tight enough and grinded some metal underneath, causing the focuser to freely rotate.

So, those are recommended to tighten up, to avoid similar problem in future.

Bare in mind, those screws seem to be very soft themselves, so, use a high precision flat screwdriver, else you will end up (like me) damaging the the grub screws.

I also added some threadlock in between 2 parts those screws are keeping together, to avoid free rotation in future.

 

Secondly, the screw which get's exposed when the focuser is fully out, it seems to get loose, from in/out movement of the focuser. Once it gets loose, it will also damage the groove it slides in (mine was), causing the focuser to get very sticky.

This is probably, number one issue of the focuser (apart from being cheeply made).

If I was to receive a new one, I'd take that screw out (don't move the focuser if you do), squeeze some grease into that hole, clean the thread with some paper and alcohol, put the threadlock on that screw and screw it back.

 

It's a five minute job, but, surely will extend the life of the stock focuser by far.

 

Good luck!


Edited by spacetourist, 30 January 2017 - 02:02 PM.



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