Howdy,
I have a Lunt 60mm pressure tuned Solar Scope. Lunt sent me 2 packets each containing 2x32mm & 2x34mm orings and grease.
I'm unsure which rings to use to replace mine in the pressure tuner.
Any help/instruction here would be appreciated.
Hi Peter,
I'm afraid I can't help you with the oring replacement, but am interested in the reason you are replacing them.
I also have a 60mm pressure tuned Lunt, and for the last few months have not been able to see any detail, either surface, or prominences.
I know the sun is super quiet, but I see images on this forum showing prominences which I think should be visual, but nothing seen.
When I start to observe, I always unscrew the tuner to equalise pressure, then as I turn it in, the tuner gradually becomes firmer to turn. I take this as an indication that the inside pressure is increasing. But there is no change to the detail through the eyepiece.
cheers Phil
Hi Peter,
I'm afraid I can't help you with the oring replacement, but am interested in the reason you are replacing them.
I also have a 60mm pressure tuned Lunt, and for the last few months have not been able to see any detail, either surface, or prominences.
I know the sun is super quiet, but I see images on this forum showing prominences which I think should be visual, but nothing seen.
When I start to observe, I always unscrew the tuner to equalise pressure, then as I turn it in, the tuner gradually becomes firmer to turn. I take this as an indication that the inside pressure is increasing. But there is no change to the detail through the eyepiece.
cheers Phil
Hi Phil,
Pretty much the same with mine at the moment.
In saying that we have crappy smokey skies here on the Gold Coast since I bought it (and Sol min) so I am not too concerned at no real detail visually at the moment. As I bought mine 2nd hand recently, the scope, being around 5-6 years old and not knowing the state of the o rings I decided to change them and re-grease.
I bought a Lunt zoom eyepiece through Bintel and Lunt were very kind in throwing in a set of o rings (well, 2 sets and that's my dilemma 32mm or 34mm) under warranty! Wow what a great company, but I knew that years ago when I worked at Sirius Optics selling them.
The Lunt website shows that the o rings do in fact over time need replacement to bring out that nice detail again on the Sun and that makes your comment "for the last few months" interesting i.e. I assume it was good before? So maybe an o ring change may help? But I may also need to wait until some rain clears the crappy skies.
Would be interesting to hear form other Lunt owners on their current visual experience with a pressure tuned scope and under what skies.
Will keep you posted on the 32/34mm o rings and how they work. Merlin the magicians I need here hehe!
Being Lunt's oldest Oz dealer, it's been a while since I did last this job...but...if memory serves...
Remove the pressure turning cylinder cap from the central threaded section.
The location of the old rings should become apparent. Remove them.
I'd clean up the inner cap and central threaded section with a microfibre cloth soaked in isopropyl.
Fit the new rings.
Lightly re-grease.
Re-assemble.
Merry Christmas.
Thanks Peter certainly helpful.
Which rings do I use? The 32mm or 34mm they sent me (2 of each in separate packs) or is it remove old ones and just overlay new ones to determine?
I wondered if one ring might be 32mm and the other 34. If so then I have a spare set I could send to Phil?
Thanks again and a Merry Christmas to you!
Thanks Peter certainly helpful.
Which rings do I use? The 32mm or 34mm they sent me or is it remove old ones and just overlay new ones to determine?
I wondered if one ring might be 32mm and the other 34? If so then I have a spare set I could send to Phil?
Thanks again and a Merry Christmas to you!
Sorry, as I said, it's been a while since I had one in pieces.
You should be able to determine the location and sizing from the existing rings...take note of the orientation, i.e. don't mix up their positions.
P.S.
Pressure tuned etalons work by increasing the pressure, hence refractive index of the air between the etalon plates. O-ring wear will cause the inner chamber to drift back to ambient pressure, hence go "off band" as air slowly leaks from the chamber.
Last edited by Peter Ward; 22-12-2019 at 06:54 PM.
I think, Peter Ward has indicated there are multiple o-rings of both sizes which you will be able to replace if you carefully note the size and position of each as you remove them.
He seems to indicate it's not a difficult process if you're careful. Take pics on your phone as you go. Make sure you have a ruler ready to measure each as you remove it.
Good luck. I'm sure you'll be fine. Worst case...send it to Peter Ward! He seems a good chappy.
Thanks all for your input here.
Faye from Lunt sent me the following very handy information.
"We send 2 sizes of o-rings as we have found that there can be some variation in the PT module. It can be very slight but some units will benefit from using the larger o-rings. This would be determined by the seal you get from the smaller set. If you feel it could be tighter then you can employ the larger o-rings.
You can also do a progression on the plunger and use both sizes. If you would like to do this here's how. Install the smaller ring on the outer groove of the plunger and the larger ring on the inner groove of the plunger. I have attached an image just in case. The grease can be applied directly to the o-ring."
I took these images as I worked with Lunt instructions.
An eyeball/ruler measurement of the old orings to compare to the new orings was of no real value.
The old red "outer oring" appeared slightly larger in diameter than the new black 34mm oring supplied, likely from stretching but still of no value to compare.
The old red "inner oring" showed what looked like a split line, the result that became immediately obvious as it was removed.
The old red "inner oring" was definitely thicker than the old red "outer oring"
I have used option 3 from Lunt and put the black 32mm oring on the "outer groove" and the 34mm on the "inner groove".
Is there a difference when I screw the pressure tuner cap onto the brass tube, well yes, I think I can feel a difference but the real test will come I guess when I get to try it out, possibly this Friday due to weather.
What am I expecting to see? Dunno will let you know!
I am about to embark on o-ring replacement in my pressure-tuned LS60.
I have an o-ring kit which covers the 32 & 34mm sizes.
But I am not sure what type of grease to use. Was the grease provided to you by Lunt identified in any way?
The grease used should have two qualities - it should not liquify at higher temperatures, and it should not emit vapours which might form a coating on the etalon surfaces.
If your grease is not labelled I will send an enquiry to Bintel (where I bought the scope), or Lunt.
cheers Phil
I recently e-mailed Lunt in Arizona to enquire as to the correct grease to use for the PT tube as wasn’t able to find details from anywhere, anyway they sent a reply stating that I should contact Bresser in Europe which I found an odd reply to receive back from the "manufacturer". I did this and within 5 minutes of sending my enquiry I received a reply and it is called Lubritech Lagermeister WHS2002 which is a Lithium soap based grease, they also said that anything with similar properties will do as doesn't have to be exact make. Grateful to Wolfgang Quere at Bresser for that reply, it’s been like find out a state secret
I am about to embark on o-ring replacement in my pressure-tuned LS60.
I have an o-ring kit which covers the 32 & 34mm sizes.
But I am not sure what type of grease to use. Was the grease provided to you by Lunt identified in any way?
The grease used should have two qualities - it should not liquify at higher temperatures, and it should not emit vapours which might form a coating on the etalon surfaces.
If your grease is not labelled I will send an enquiry to Bintel (where I bought the scope), or Lunt.
cheers Phil
Hi Phil,
I did receive a very small amount of grease in a double sealed bag. It appears clear but with no identification sorry.
I ended up using both 34mm orings. But haven't used yet as been too busy over Xmas.
Would appreciate knowing what you find out.
Been trying find an Oz supplier of the Largermeister grease mentioned in Merlins post.
Regards
Peter
I recently e-mailed Lunt in Arizona to enquire as to the correct grease to use for the PT tube as wasn’t able to find details from anywhere, anyway they sent a reply stating that I should contact Bresser in Europe which I found an odd reply to receive back from the "manufacturer". I did this and within 5 minutes of sending my enquiry I received a reply and it is called Lubritech Lagermeister WHS2002 which is a Lithium soap based grease, they also said that anything with similar properties will do as doesn't have to be exact make. Grateful to Wolfgang Quere at Bresser for that reply, it’s been like find out a state secret
ken
Wow, indeed Ken that is like finding out a state secret.. I enquired mid last year with Lunt as I was just looking to relube the o-rings in the solar scope I'd purchased secondhand... Lunt just stated that I should purchase their O-ring replacement kit & they would supply some grease... repeated requests for what grease to use was just met with silence...
So, any idea where one can purchase this (or something with similar properties) in Australia? I'd still like to regrease my O-rings though replacing them might also be in order too...
I managed to track the grease mentioned in your post.
It is manufactured by Fusch (Germany), and is sold in Australia by Bursons.
I went in to the local Darwin Bursons store and have ordered a 500gm cartridge, which should arrive in a week or so. It's expensive at $52, but I prefer to use the recommended product.
I reckon it will be useful for other purposes as well.
I replaced both the o-rings with the larger 34mm rings (instead of the 32mm) and used the small amount of grease supplied by Lunt.
Wow, first real use today and saw some pleasing views along with a nice little Sunspot, happy days!
After much reading of user reviews it seems the replacing of the pressure tuning o-rings/regreasing is a part of regular maintenance (every few years I guess) if you want the scope performing at its best.
Also a BIG thanks to PhilTAs who has sourced the grease needed and is sending me enough to do many years of re-greasing.
