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Coronado Solarmax II 60 internal etalon tuner problem

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I purchased this scope in clean used condition way back in October'16.  I didn't try before purchase - it was autumn and I collected in the evening and it looked immaculate.  Due to other commitments, hopeless weather and bad timing my first determined effort to use it was just last weekend, I sat with it from 11am through to 6:30pm with 25mm & 12mm cemax EPs and then my astro camera with various exposures/gains...each time the same plain disk (+ one sunspot) with no variation whatsoever. Focus was sharp though.

I read up about how the tuning is supposed to work and armed with the knowledge that my tuning lever had never felt anything but buttery smooth and free with no resistance whatsoever in the CCW direction I eventually took a look inside it.  I discovered the pin affixed into the colimation lens (I assume that's what it is) that should apply pressure to the etalon when the richview tuner lever is moved CCW was slack in its hole hence no pressure was being applied to the etalon regardless of tuner rotation., the screw/pin was prodruding a few mm out of the back of the collimating lens which makes me think the tuner cell at some point must have been screwed past the point wehere you could actually insert the tuning lever into the threaded holes.  With the tuner cell removed there was little resistance from the pin when I touched it with my finger.   The glass around the edge of the pin hole is tatty too, yet no minute fragments/debris was anywhere to be seen.

So....does anyone have any pictures of what their tuner looks like inside and specifically how this pin is supposed to stay put?  This looks like an interference fit as there is nothing mechanically holding it in place, I'd kind of expect a compression fit or maybe a conical hole/conical head given how this pin is expected to push without falling thorugh the hole but maybe that's me overengineering this or some 'protection' against cracking the etalon at the expense of this ruining this part. 

Any info/pics appreciated.

Best Regards!




Edited by sonneyboy

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So applying a thin smear of jb-weld epoxy carefully around the inside of the centre hole in the collimation glass using a sharpened matchstick (being careful not to get any on the lens surfaces) and re-seating the pin and leaving it 24hrs to cure inevitably failed, it held for a very short while but once more it began to push through the lens again with little effort as I tested the tuner, a rare sunny day almost wasted. 

Next I crafted a temporary replacement flanged pin from the end of a wooden kitchen spoon handle using a small file and my cordless drill as a lathe...a 'beta' version think I'll call I for now.  The beta pin is a gentle push fit into the collimation glass (see pics) and the flange prevents it pushing through completely.   (See below)

IMAG0511.thumb.jpg.7dd0edff10b950e3a0e91dde7af6b386.jpg   IMAG0509.thumb.jpg.47c09ae54178b19766f1287f781c7c6e.jpg

However when I tried the scope again I didn't get a whole lot of success, there seemed to be a subtle difference to the brightness of the view when I moved the tuner lever back and forth but no still detail at all.  The etalon looks ok (I'm no expert but it doesn't appear to be decontacted and now I know the tuner is finally applying some pressure to it I'm gonna temporarily rule this component out of the equation.  I headed back to Google.  

The view through the eyepiece I have to admit has never seemed all that bright but having nothing to compare it to means it's difficult to be certain if that is how it should be, my makeshift pin is a tad wider than the original and this might dim the view (maybe a little?) but its still narrower than the silver centre spot on the etalon so hopefully it's not playing a major role here.  The last few days of testing had always made me think the view was a little miserable regardless of the absence of detail and not all that easy on the eye due to being dull.  This got me wondering if the reason for the broken tuner was due to somebody over-tightening the tuner trying to compensate for a bad blocking filter/ITF, trying to see the detail it might have once provided them.   The BF10 diagonal looks in good shape to my untrained eye, the finishes on both optics looked nice and shiny and so I'd ruled that out days ago.  However this is the only BF I've ever seen up close and personal and now I think I was wrong.  Reading that the ITF rusts on the inside I unscrewed the holder...


The pic above I think shows it has rusted a fair amount, almost all over its surface in fact (hard to see on the pics but in the centre there is a hint of the original colour).  I'll be looking to source a replacement glass from Beloptik and hopefully wont find anything else wrong with this scope!

In the mean time I'd still like to know how the original centre pin should be held in place in the collimation lens - anyone know?

It's all an (expensive) learning curve!

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An update...I fitted the replacement ITF which arrived yesterday that I'd ordered from Beloptik. It took less than 5 days to ship from Germany to the UK. It was a straight replacement of the original ITF taking 5 mins to swap.  The image is very bright now and the scope is much more pleasurable to look through.

After a little tuning (still using my crude etalon wooden tuner pin) I began to see subtle surface detail, having never seen any detail before through this scope (or any other h-alpha scope for that matter) this was very welcome and captivating. I could see proms and surface detail when I tuned back and forth. Using a 12mm EP it worked great - it's a full disk image presented to the eye and so it takes some concentration and perseverance to pick up on such small details but the longer I looked the easier it became to see them. I'm sure experience and time behind the ep will make this easier in future - and a blackout cover over my head would help keep my eyes accustomed to the view.

I hooked up my camera to see if I could capture something from this momentous occasion. I'm a complete amateur always learning on the fly so forgive the hopeless exposure settings and camera noise in the pics, i'll sure i'll get there eventually. I'm hopeful I can get better results, this was first light for this now 'working' setup.


(Camera is a dmk41au02)

I still need some answers on the Etalon tuning pin which should improve tuning but at least this scope is now moving in the right direction.


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I am not familiar with this arrangement but it seems bizarre that a metal fixing is inserted into a glass optical surface with no rubber gasket or similar. I suspect it's been fiddled with previously. 

Maybe @Peter Drew or @Merlin66 can help?

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I'd send it to a coronado service and repair place. I don't have a coronado but I did buy a second-hand lunt 60mm supposedly in good condition,  when it arrived by post I inspected it and the blue UV/IR filter was failing. Foggy and two round marks on the edge. I sent it away for service and repair which only cost £30. Some people who sell second hand telescopes have no scruples.  Hope you get it sorted.

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It could be that the seller rather than having "no scruples" was unaware of the problem... not every user inspects the blocking filter assembly regularly and would appreciate or understand what they are looking at.

I would recommend to all purchasers of solar equipment that they request an image of the ITF filter element prior to commitment.



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The rusted BF filter didn't overly concern me as it seems very common and would have occurred anyway at some point in my ownership, it looked great to my untrained eye from the outside.  There is the chance the seller didn't know about it I guess - especially if it had been stored for a while and was OK on a previous outing, I'll never know on that one.   

However, the tuner problem is perhaps where scruples come in to play - the seller described the scope as working perfectly which was not the case and could never be, it was entirely off-band and impossible to tune due to the fault.  He must have know this was a problem - or he had never any luck with it himself (despite saying it was in perfect condition) and just sold it on to the next wide-eyed sucker with cash on the hip and a hunger to see the Sun in h-alpha!

This boils down to two things, 1) I didn't fully research the item I was purchasing (I watched and read reviews but to be fair none mentioned rusty BF filters or broken/missing internal components), 2) I didn't have a field test. 

Lessons learned!


I'm still practising with this setup, I'm still getting a section of horizontal noise from somewhere, still much to learn.  This was from 14th July '18.



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