Easier Lunt pressure tuning suggestions?

[Richbandit]

Long time lurker, but this is my first actual post on SGL so please be gentle!  I'm after any advice or recommendations please ....

With night time imaging opportunities becoming increasingly more unpredictable here in UK in recent times (clouds, rain, more rain ....), last year I decided to get a Lunt LS60MT and try my hand at some solar imaging.  Logic - double my chances of doing some imaging, option of day or night (or both?)!

Anyway, on to the reason for my request.  The arthritis in my wrists/thumbs is slowly getting worse and I'm finding that because it's naturally pretty stiff anyway turning the Lunt's pressure tuning knob is now becoming very awkward and even painful at times.  Not to mention the image jumping all over my laptop screen whilst attempting to tune it!

So to save my aching wrists I've searched around for any unique approaches to 'automating' the knob operation and I've seen the two main suspects regularly discussed - i) remote pressure regulation , either using Lunt's own PC-USB controller (now unobtainable?) or an equivalent DIY solution, or ii) mechanical means using gears/belts, stepper motor, etc.  The latter might be an option for me to consider, not too sure about the former.

Hence I would very much appreciate if any of you more experienced users out there might have any other sensible (and practical!) ideas I could consider trying?  I need to set up from scratch for each session, so whatever method really needs to be unobtrusive or removable I guess.

Many thanks and appreciate your time, and I'm intrigued to see what responses I may get (keep it clean!).

[Steve Ward]

Welcome to the forum ... 🌞

There's a thread running on this very subject over on the Cloudy Nights forum , but it's not particularly helpful as everyone's looking but there's no immediate solution I could see other than the Lunt unit may be available again in the autumn of this year , at $1520.00 ... !

 

https://www.cloudynights.com/topic/568875-is-there-a-remote-pressure-tuning-device-for-lunt-scopes/#entry13449297

[Richbandit]

Hi Steve,

Thanks for your response - yes, I've seen that thread on CN forum and, as you say, no other solutions forthcoming from that, really.  Not sure I'll be able to justify the cost of the Lunt controller, if/when it is released, at what is effectively half the cost of my 'scope itself ...

I'll keep searching and hoping.  You never know, some entrepreneurial bod might get the Lunt unit when it's available and 'reverse engineer' it into a DIY option for us all!!

As an aside, I now recall that I have indeed previously posted a few times on SGL, but it was a few years ago and regards a totally different topic ...

[Rusted]

Reducing the pressure adjustment problem down to the absolute simplest level:

A friction cap with a large [say] 4"/10cm? wheel/disk attached. To increase the torque available might be the very simplest option.
The Lunt drum is about 55mm in diameter. So 55/100 = a reduction of only about half the effort required. Worth trying? I am really not sure.

Simply reducing the considerable physical effort required might actually minimize the image wobbles.
Only hands-on testing would confirm this.

A friction cap for the Lunt drum adjuster with [say] pencil sized levers [capstan style] to apply the effort manually.
This would reduce the physical effort required but might not alter the risk of image wobbles.

I rushed off to find my unused 60MT and quickly discovered the severe strain on my own strong, but aging, hands.

Any geared motor system would need a considerable gear reduction ratio to work smoothly against the considerable torque required.
This is no simple lash-up! Not like adding R&P focuser movement with a Skywatcher motor. Or tuning to a PST etalon. Done both.

In fact I imagine a worm/wheel gear might be a much better approach. This could be incorporated for manual adjustment.
With the worm mounted on an extended shaft. Brought back to a manual adjustment wheel near the eyepiece.
Lots of gear ratios are possible but there might be an optimum for reduced manual effort without time consuming winding.
Availability of suitable commercial worm/worm-wheels? Dunno.

All these ideas are off the top of my head without deep analysis of effort:ease of use ratios.
Do not underestimate the remarkable effort required to turn the Lunt pressure drum! Grr? 😠

 

[Richbandit]

Hi Rusted,

Many thanks for your thoughts and suggestions.  I'm pleased to see it's not just me that appreciates the effort required to turn this thing!

I've also been coming to the conclusion that probably the best way might be for some form of gearing system to provide the amount of necessary torque if done correctly.  Easier to construct as well (gears/wheels/pulleys/shafts/whatever) so more suited for 'kitchen table DIY' than messing around with pressure systems and valves, etc.

But I hadn't considered a manual configuration rather than an 'automated' (i.e. motor driven) one - could well be some merit in that, and I thank you for placing that idea in my head!  As I'm only imaging, I'd fallen down the rabbit hole of thinking this operation should/could be automated in some fashion, because of course I'm trying to look at my laptop screen, under cover, whilst doing the adjustment on the 'scope .....

I like your idea of a worm on a shaft turning a larger gear attached to the knob, I'll pursue options for that ... I guess I'd need a method of temporarily disengaging the worm from the gear if larger knob movement ever needed (removal in order to 'burp' the pressure chamber, for example).  Also, the only complication I can foresee with such a worm/gear arrangement is that it wouldn't allow for any in/out movement of the knob on its thread, as it's turned; even a very small turning of the knob would presumably move the gears out of optimum alignment.  Then again, if the knob is positioned as close as possible to 'on band' to start with, then any subsequent movement for final adjustment should (in theory!) be minimal.

I've seen one posted solution using 3D printed gears, etc. (albeit this was for a motor driven arrangement), and that gear ratio was about 8:1.  But that's using a small stepper motor, so as you say a ratio of, say, 2:1 might be all that's needed for easier manual operation.

I must say I've somewhat staggered that, given the entrepreneurial nature of us amateur astronomers, a simple (and cheap!) solution for this issue hasn't been bottomed out ages ago, considering how long Lunt have been providing the PT system to the market.

Hmmm - all good food for thought, though!  Thanks!  Now, where did I leave those arthritis gloves ...... 🤔

[Steve Ward]

Frequenting an airgun forum as I do just made me think that one of these might well help make the tuning easier , they work very well on rifle 'scopes ... ☺️

 

 

[Steve Ward]

https://www.veals.co.uk/product/breakaway-nylon-coasters/

As they come in packs of two you could use two of the locking nuts on one of the clamps (or more if you buy a couple of pairs) 

This would double or treble the length of the lever giving an even greater assistance leverage-wise.

Edited May 15 by Steve Ward

[Rusted]

Genius!

[Steve Ward]

I wouldn't go that far Chris ... 

I should have remembered them when I read the CN thread ages ago ... 

I hope the idea works though , I've never had the pleasure of struggling with a pressure tuner so it's hard to imagine the stiffness of them and how much torque is needed.

But if it's a choice between a six month wait plus $1500 and £4.20 plus postage I know which one I'd be trying first .... 😄

Edited May 16 by Steve Ward

[Rusted]

These clamps aren't readily available over here. Certainly not by the 'Breakaway' name.
One shooting shop has given them a special name and are selling them at £12 equivalent each.
I wonder if a tropical hardwood, presentation box, with plush lining, is part of the deal. 😏

[Steve Ward]

That's a pain.

I'd be more than happy to get some off e-bay and post them to you.

[Richbandit]

What a shout!!!!  Brilliant!!

Many thanks Steve, that's a very interesting option worth pursuing for sure.

As it happens, I know of Veals - personally I have no use for their products myself (don't fish and don't shoot!), but my company (before I retired) installed some security equipment in their premises in Bristol and I attended there on a number of occasions.  I live in Chepstow, so could even pop around there myself to obtain some!

In the meantime, I had actually thought about trying out a similar test - I have a rubber strap wrench, which works on a similar principle and is adjustable (PATTERSON MEDICAL Baby Boa Strap Wrench - Colour May Vary : Amazon.co.uk: DIY & Tools) but haven't tried it as I wasn't sure if it would be a viable option (not strong enough, too flexible)?  However, it certainly warrants using it for a 'proof of concept' test, on the basis that your item would be a much stronger attachment and so presumably more stable with less movement.  So if my wrench shows an improvement, it augers well for then trying out your version ...

I'm on it!  Will report back in due course!

Thanks again to you both for your interest .....

[Steve Ward]

2 minutes ago, Richbandit said:

What a shout!!!!  Brilliant!!

Many thanks Steve, that's a very interesting option worth pursuing for sure.

I'm on it!  Will report back in due course!

Thanks again to you both for your interest .....

You're very welcome.

Looking forward to hearing how they perform on the tuner , as I said to Chris it's hard for me to judge the effort needed as I've not used one myself.

Fingers crossed I was going to say , but that's probably highly inappropriate given the reason for your initial post ... 

[Richbandit]

Guys,

I haven't forgotten this - I'm still planning to conduct a test for this sometime over the next few days .... sorry for the delay, weather's not particularly playing ball over this way at the moment!  Whenever I get a reasonable break in between the clouds I'll set up outside and test the principle using my strap wrench in the first instance and, if successful, I'll consider getting one of those reel coasters to try ....

I want to fully set up outside as normal, as opposed to doing a 'dry run' indoors, so that I can view my laptop screen in exactly the same way as I normally do, with an image of Sun on it.  This way, I'll be able to make a more accurate comparison with 'strap on' vs 'strap off' (that sounds like it could be the title of a rather dubious, and possibly illegal, video concerning a particular type of film genre!! 🫢).  Ahem!

[Richbandit]

Would you believe it, 5 minutes after my last post the clouds abated somewhat and I could actually (sort of!) see the Sun!  So I'm set up outside .....

Truly dreadful seeing (Sharpcap's seeing monitor shows 2.5 seeing, which is really, really bad!!!) with lots of hazy cloud, but that doesn't matter as I'm not intending to get any great images today.  I should also qualify that I'm using a Skywatcher Solarquest mount + tripod, so of course that's very light and 'twitchy' anyway.  It's also susceptible to movement in the head gears so it tends to move slightly sideways anyway under any very slight strain.  Not ideal normally, but for a comparatively lightweight 'scope, etc. and fast frame rate it's not an issue to worry about and generally works well.

Placed my strap wrench around the pressure knob, and I can confirm that using that as an extended lever makes a HUGE difference to the ease of operation!!!  Wrench is about 150mm long, so that provides a good moment of inertia.

Turning the knob inwards (increase pressure) requires considerably more force anyway of course, but using the wrench made this task very easy once the initial 'release of threads' (if you see what I mean) had been achieved.  The 'scope still 'wobbles' to some extent, but nowhere near as bad as before - but I found that literally one finger of my spare hand gently held against the side of the diagonal to prevent the sideways movement was enough to hold the Sun's position steadily enough on my laptop screen.  Some slight wobbling inevitable, but at least the Sun was staying sort of centrally now and in view!

Meanwhile, turning anti-clockwise (releasing pressure) was soooo eeaaasssyyyyy ...... smooth as silk, no discernible wobble at all.  None.  Nada. 

After a few trial runs, I found the best method was to initially wind the knob inwards and go past the perceived 'sweet' spot (I used Sharpcap's histogram and looked for the lowest reading, then went past this slightly).  Then, reversed my wrench and started to 'back off' the knob anti-clockwise until moving back to what I perceived to be the best optimum setting.

So there we are - it looks like the basic principle is sound, well spotted Steve!  I'll now go ahead and obtain some of those 'throw levers' from Veals and I'll report back my findings once I'm able to test those out ....

Onwards and upwards!

[Richbandit]

Some photos of my test arrangement ...

[Rusted]

That's a bit posh! Royal purple!

[Richbandit]

Well, one needs to try one's best, don't you know!! 😉

[Rusted]

On 16/05/2024 at 09:03, Steve Ward said:

That's a pain.

I'd be more than happy to get some off e-bay and post them to you.

Please don't. The Danish post office will want £20 equivalent standard charge for clearing customs.

Plus 25% VAT on the stated value of the goods. Brexit? Brokesit!  🙄

[Richbandit]

Chris,

I note this company in Dublin supplies them as well - Online Fishing Shop | Henry's Tackle Shop | Breakaway Nylon Coasters (henrystackleshop.com)

So presumably you won't need to pay any excess duties, etc. as Ireland is still in EU?  I guess postage might be a little more, but shouldn't be too bad?

[Rusted]

Thank you both.

I'll keep searching for a local source. It seems very unlikely that they aren't available locally.
They may have a particular name [in Danish] which triggers sales websites.
Fortunately they are very light. So postage shouldn't be a problem.
€21.60 for two bags of two units from Ireland.

Edited May 17 by Rusted
additional info

[Richbandit]

I see they're also available on Amazon as well - do they have a Danish branch, for local supplies and deliveries?

[Rusted]

Thanks. There is an Amazon branch in Germany.

No Breakaway coasters.

Edited May 17 by Rusted

[Richbandit]

Well Guys, it seems like 'we have the technology' .......

Decided to order the 'coaster clips' on-line with Veals, for delivery.  Postage was £2.50 - it would have cost me that to start my car up and make it to the end of the road!!  Ordered yesterday at mid-day and, with amazing efficiency, they were delivered today, also around mid-day.  What service!

So here's an explanation of my process with some accompanying photos - excuse the long post, as there's a number of steps + the photos!

Here's the item(s), as received, 2 per pack:

I then disassembled one of them - unscrew knob and the nylon tie section easily pulled out:

I then determined that the thread inside the knob is actually M10.  As it happens, I had some short M10 threaded rods left over from a house building project a couple of years ago.  And they measured 140mm in length, close enough to by strap wrench as tested - sorted!  But, when the knob is screwed up tight there's no appreciable thread left available within the knob itself to screw the rod into, due to the length of that 'guide flange' protruding out.  Solution - cut the flange down a little to allow more threads inside the knob to be available (I've cleaned the cut end up since taking this photo!):

Assembled the clamp onto the PT knob and cut off the excess straps, flush with the (cut down) flange.  Excuse the out of focus photo, but you get the idea ...

 I then removed, released the knob and pushed the straps through a short distance and cut them off a bit shorter (as explained in Steve's video).  I actually cut 5 'threads' off each strap.  Then reassembled and fitted onto the PT knob again:

I then screwed the rod into the clamp knob, to test .... AND IT WORKS AS PLANNED!:

Realising that this rough and ready threaded rod might not be the most comfortable thing to grab hold of, I went back to my shed in search of something to cover it with.  Aha!  Some 15mm 'Speedfit' water supply pipe had the perfect internal diameter to enable it to be screwed onto the rod!  Measured and cut to size, screwed onto the rod (the rod threads happily cut their way along the inside of the plastic pipe - a little stiff going, so I used a 'mole' grip to assist).

Then, would you believe it (of course!), it started to rain, so I decamped into our wash room ...... here's the rod + plastic pipe cover, fitted:

I can then remove the threaded rod section, leaving the clamp still tightly in place:

Aligning the clamp in this orientation allows me to still comfortably close the lid of the 'scopes carry case (it's about the same excess protrusion as the 'scopes tube clamp).  The PT was orientated where I'd left it from my last session, so hopefully it shouldn't be too far off the optimum setting and thereby require only minor adjustment to bring it back on band next time out.  I hope!:

And the lid closes, for storage, no problem:

 

So, there you have it!

It fits, and seems to work in principle as planned.  I'll test it out for real whenever we get a clear day with some sun (tomorrow doesn't look too bad, I think) and let you know the outcome.  Further to my test using my 'strap wrench' I have no reason to doubt that this sturdier solution should be able to do the job nicely.  We'll see ....

 

[Richbandit]

It's amazing, there's an unusual shiny thing in the sky today, surrounded by lots of blue stuff ...... 😃

So, time to test out the 'gizmo' for real ...

Here's the photos:

Damn, that wall needs repainting - I knew there was something I needed to do ....

So there you have it!

It worked flawlessly as planned.  I had feared that where the threaded rod (steel) is screwed into the clamp knob (plastic) would be a weak point, possibly susceptible to flexing, or even breaking?  But it seems to be fine, I guess the sort of movements and forces applied to it are pretty smooth anyway.  Time will tell how well it lasts!

One point of note, for anyone else considering this 'hack' - in cutting down the clamp's protruding flange and then cutting down the straps to suit, this naturally leaves fewer threads available for the knob to grip on when it's tightened.  I managed to get the knob to jump the threads on one occasion - but, to be fair, I was trying to screw it down a bit too tightly than necessary at that point!  For normal tightening, it's fine and seems to be rock solid.

I mention this because I made sure I only cut the flange down enough, and no more, to enable some of the knob's internal threads to be visible and accessible when fitted, so it would provide some purchase for the threaded rod when screwed in.  In other words, be careful - cut too little off and you may not have any threads available to fit the threaded rod; cut too much off and the knob might not be able to tighten effectively!  The off-cut piece is in the bin now, but as I recall it was around 5mm or so - looks like I chose wisely .....

As an aside, I had an unrelated issue whilst conducting this testing as well, which was a heart-stopper!!  The eagle-eyed among you may notice from the photos that since my previous posts I've now replaced the stock saddle with an ADM dual type (the version that's properly designed for the Solarquest!).  Fitting it, no problem - but as you can see in the photos the dovetail bar I'm using is one of those with a groove down each side.  This groove is located almost exactly where edges of the saddle jaws need to grip - it was a gnat's what'sname away from not working and I wasn't overly happy about it.  However, once I'd tightened it down it seemed to be gripping OK - note to self, get another dovetail soon!

I took a couple of SS image sequences in the process of testing out the 'gizmo' and all seemed well.  I then decided to fit my double stack unit to see how that would work and, as I was screwing this onto the front of the 'scope the dovetail jumped out of the saddle and the 'scope decided to make a break for it and dive towards the floor! 😬  Luckily, I was holding/supporting the body of the 'scope whilst I was doing this so by instinct alone I was able to immediately catch it before it had dropped too far.  Phew!!!!!  Brown trousers time, I can tell you!!  So, another note to self - DEFINITELY GET ANOTHER DOVETAIL SOON!!

Have fun!