Focuser upgrade for my Lunt LS50 H-Alpha Scope

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Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

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 Tucker at Starizona in Tucson, Arizona, 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).

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
borg 7315 helical focuser.JPG (109.73 KiB) Viewed 12941 times
Starizona has several of the Borg-to-Lunt LS50 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.


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

My photo gallery: http://www.astrobin.com/users/robinandcurtis/
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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by swisswalter »

Hi Robin

that is a neat setup


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by marktownley »

A ingenious piece of modding there!


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

Thanks Mark and Walter!


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

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.

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

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.
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borg focuser and lunt focuser.JPG
borg focuser and lunt focuser.JPG (147.59 KiB) Viewed 12884 times


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

My photo gallery: http://www.astrobin.com/users/robinandcurtis/
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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by solarchat »

well, the market demanded an entry level, visual only scope for around 7 hundred dollars.

The LS50 certainly beats any competition under $1000 the way it is sold. If they put a real focuser on it like a Crayford or whatever, everyone would be complaining that it is too expensive.


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

solarchat wrote:well, the market demanded an entry level, visual only scope for around 7 hundred dollars.

The LS50 certainly beats any competition under $1000 the way it is sold. If they put a real focuser on it like a Crayford or whatever, everyone would be complaining that it is too expensive.
I'm not expecting a Crayford; I'm just expecting the focuser that comes with the scope to work without the "sag" or "play", both of which I and others have experienced with the supplied helical focuser.

I think it's perfectly reasonable to expect the helical focuser that comes with the LS50 to work well and not detract from an otherwise enjoyable scope.


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

My photo gallery: http://www.astrobin.com/users/robinandcurtis/
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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

Somone on Cloudy Nights (where I have a similar thread on this topic) asked me: 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 the stock focuser works well enough for your needs if you only use it for visual.

I think if you are going to do imaging, and have a small chip camera (like my Skyris 132m, which has a chip size of 3.6mm by 4.8mm), the stock focuser might be more of an issue. As I mentioned in my first post here, with camera attached, trying to center the solar disk in the tuning sweet spot is a bit finicky because when the drawtube is not locked in place with the focus knob, the drawtube sags, which puts the sweet spot closer to the edge of my camera's frame. What I do is with the focus knob unlocked, I use my mount's slow motion controls to move the solar disk until I've located the sweet spot (which can be detected by turning up the gain). The solar disk may at this point be only partially in the frame. Then I tighten the focus knob to lock and straighten the drawtube, to see where the sweet spot moves to, which is usually more centered in the frame. I then move the solar disk to that location, which usually puts the full disk back in the frame. I then loosen the focus lock again, fine-tune focus and then lock the focus knob and now I have the solar disk in the frame and the sweet spot centered on it and focus dialed in. Here's a screenshot of how it looks in FireCapture after I've done this:
tuning.jpg
tuning.jpg (75.02 KiB) Viewed 12845 times
I've been able to achieve good images using the stock focuser, but it does take extra fiddling. If you use a camera with a larger chip size, it may not require as much fiddling. With the Borg focuser which has virtually no sag in its drawtube, the sweet spot is already centered enough in the frame that I don't have to do any fiddling. It's a pleasure to use in that respect.

My Skyris 132m camera weighs about 4 ounces with the T-to-C adapter I use to attach it to the scope. The Borg focuser focuses smoothly with it and thus can handle the weight. However, weighing 5.5 ounces, the Lunt zoom eyepiece 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 or cameras less than 5 ounces, the Borg focuser should handle them with no problems.

If you need to re-lengthen the light path of the Borg focuser by 5mm to match the stock focuser's light path, Scott at Starizona may be able to make you a Borg-to-Lunt 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 also do this with the stock focuser if you need a few more millimeters of light path). Hope this helps.


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

My photo gallery: http://www.astrobin.com/users/robinandcurtis/
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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

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 and binoviewer.

I will just have to wait and see if the Lunt replacement focuser 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. It may be possible 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). :-)


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

My photo gallery: http://www.astrobin.com/users/robinandcurtis/
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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

In case anyone is interested, the thread size at the rear of the LS50 telescope tube (where the helical focuser attaches) is M35x0.5. I got this information directly from Lunt.

Also, I have heard (don't ask me how I know) that Lunt may be offering an optional "upgraded" focuser for the LS50, if they can achieve a reasonable price point for it. Timeframe may be by the end of this year.


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by marktownley »

Useful to know! Thanks for the additional info :)


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by Cometeer »

If any one is interested, Lunt is releasing a faethertouch for the LS50: https://luntsolarsystems.com/product/1- ... focuser-2/

Unfortunately it's only single speed. Moonlite will be releasing one too in around the next month and that one will be dual speed.


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

Great news! I wonder if the Feathertouch focuser allows the same or more inward focus travel as the stock helical focuser. Guess I'll have to ask Lunt.


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

My photo gallery: http://www.astrobin.com/users/robinandcurtis/
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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by Cometeer »

As for the Moonlite:

(quote)
"There is no room to make it have any shorter profile in a crayford
design. Sorry, we would if we could- but the design will not allow it.
We gave it a little over .4" of travel and the same exact racked in
profile as the stock focuser.
Price for the new Moonlite mini 1 1/4" crayford is $215 for a single
rate or $315 for the dual rate. All colors are available.
Plus it can be automated with our motor systems if customers need to."

It will be ready in around 2-3 weeks.


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by Cometeer »

saguaro wrote:Great news! I wonder if the Feathertouch focuser allows the same or more inward focus travel as the stock helical focuser. Guess I'll have to ask Lunt.
Let me know what they say.


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

Thanks for the Moonlite focuser info! It will be awesome to have two choices!

According to the info from Moonlite: the Moonlite will have about 10mm of focus travel, with the same racked-in distance as the stock helical focuser. By my measurements, the stock helical focuser also has 10mm of travel.

According to the info on the new focuser from Lunt: https://luntsolarsystems.com/product/1- ... h-focuser/
the Lunt focuser has a "minimum focus height of 48mm". This is just a couple millimeters shorter than the stock helical focuser height of 50mm (by my measurements). And the range of the Lunt focuser is listed as 15mm, so provides a bit more outward travel than the stock helical focuser (10mm by my measurements) as well as the Moonlite.


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by Cometeer »

Didn't know that the Feathertouch was shorter than the stock helical. I'm going to go with the Feathetouch since it has more backfocus and that extra 2mm of in travel is pretty crucial to me.


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by saguaro »

I would confirm directly with Lunt before buying if you will in fact get an extra 2mm of in travel versus the stock helical focuser.


Lunt 50mm H-Alpha telescope with B600 blocking filter and LS50c (compact double-stack module)
Skyris 132m camera

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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by marktownley »

This is great news! Makes the Lunt 50 an attractively priced and modular scope that folk can improve over time. Good stuff!


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by Live_Steam_Mad »

Cometeer wrote: Thu Jul 28, 2016 6:24 pm As for the Moonlite:

(quote)
"There is no room to make it have any shorter profile in a crayford
design. Sorry, we would if we could- but the design will not allow it.
We gave it a little over .4" of travel and the same exact racked in
profile as the stock focuser.
Price for the new Moonlite mini 1 1/4" crayford is $215 for a single
rate or $315 for the dual rate. All colors are available.
Plus it can be automated with our motor systems if customers need to."

It will be ready in around 2-3 weeks.
Able to be motorised? Not according to their own website under their "CM-Lunt-50" product, it says "CM mini only comes in the color red as shown. No motor option is available" ;-

https://focuser.com/products.php

...I've sent an e-mail to Moonlite to show them this discrepancy here versus their website and asking for clarification.

If the Moonlite or Feathertouch (and stock focuser) all cannot have a motorised focuser option then that is a rediculous situation IMHO. There must be some way of having a decent quality motorised focuser on the LS50, surely?

Regards,

Alistair G.


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by Live_Steam_Mad »

Ron at Moonlite wrote back to me quickly and said ;-

"Yes, the CM mini lunt 50 focuser can use our High res stepper motor with
mini V2 controller.

The bracket to mount the motor is a custom machined to allow the motor
to bolt up to the Moonlite Mini lunt 50 focuser. It is fabricated by
request only- not a stock item or listed on the web site.

Custom motor mounts are $100 ( any size/ shape). Plus customers would
need to purchase the High res stepper motor with mini V2 controller for
$440. Total cost would be $540 plus shipping for a motor setup.

If you need a Moonlite Lunt 50 focuser as well, then please add either
$340 for the dual rate version, or we can install just a regular knob (
single rate version) on the right side for only $240.

Total cost would be--

Qty1 Moonlite Lunt 50 focuser $240
Qty1 high res stepper motor with mini V2 controller $440
Qty1 Custom machined bracket system $100
------------------------------------------------------
$780 plus shipping

We can automate just about any axis, even pressure tuners with a 2 axis
system.
Here is a look at the motor options and controllers for basic focus
automation.
http://focuser.com/motorfocus.php#jump2

Here is a look at a custom 2 axis unit ( 2 stepper motors) controlling
both focus and the tuner on a SolarMax 60 scope. See attached photo --
not 2 motors are required and a Dual port DRO display controller to run
both axis.

We can even make custom 3 axis focusers for automating ---Focus,
Rotation, and tuner. But they use the big / heavy LiteCrawler LC25
format platform and cost $3000 for a 3 axis setup. They can get large
and expensive when adding more axis to automate.

https://www.youtube.com/watch?v=azcv1b6u3jo

Thanks
Ron
Moonlite
www.focuser.com"

...now that was wonderful for me to hear. Hope it helps others. I was just about to order a Lunt 50 last night but then I read on CN forums of several people who have had no surface details through Lunts, including one guy who has had 6 Lunt scopes and filters! So I am unsure how to proceed. I only ever looked though a Lunt 80 Pt SS and it had lots of good contrast detail (looked like iron filings on a yellow /orange ball). Oh well at least there is now a motorised focuser upgrade and remote control pressure tuning available for the Lunt, for casting/imaging with. The PST for example doesn't have these options.

Regards,
A.G.


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Re: Focuser upgrade for my Lunt LS50 H-Alpha Scope

Post by Live_Steam_Mad »

Found out that Starlight do a motorised dual speed Feathertouch focuser for the LS50 ;-

https://stargazerslounge.com/topic/2503 ... nt=3265721

I just got my own LS50 and it's a wonderful scope, plenty of surface and Prominance detail ;-

https://stargazerslounge.com/topic/2883 ... nt=3265493

Regards,

Alistair G.


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