Please help: Problem on frontal lens of Lunt130MT?

[H-Alpha]

Dear all,

Yesterday it was the first day I used my new Lunt130MT on a mount and had the time to inspect it in the sun.

I observed something strange on part of the frontal(?) lens internally, or the lens just behind it (do not know how many pieces of glass are at the front). It looks like humidity? I hoped it would go away the second day, but unfortunately it seems like something permanent.

Please have a look at the photos below. It is obvious by many angles, not all though.

I am quite worried, since I do not know if it is serious or not, so before contacting Lunt and OPT, I would like to have your view on:

1) What could this be?
2) How can it be there, since Lunt are testing the scopes before sending them?
3) Is it serious?

Any advise is very welcome!!!! Please help!

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All the best,
Alexandros

[Bob Yoesle]

Looks like dust. The direct sunlight will show almost any amount of the stuff.

It will not affect anything visually or imaging wise. I would try blowing it off with compressed air or other clean gas - do not use typically computer cleaning compressed gas cans or the like due to risk of chemical contamination.

You can also follow the directions here: https://www.youtube.com/watch?v=JkxbB1rkSGI

Also see here: http://www.company7.com/library/clean.html

It's a "what's worse" scenario - the dust or the risks from cleaning it.

However, if the dust is on the inside surface(s), that's a different issue having to do with quality control and needs to be rectified.

[DeepSolar64]

Alexandros,

Your frontal glass is known as an objective lens, in this case an apochromatic triplet. It corrects for all three primary colors and has three elements with one an ED element and should give you a sharp image with little or no color fringing. Anyway, back to the point.

I can see what appears to be dust. With me dust, and especially pollen is a big problem. It gets on my objectives and eyepieces and builds up quickly since I use my scopes very often. It can be cleaned off carefully with a clean cloth and I often use eyeglass cleaner ( sparingly ) for good results. I use a blower bulb first to blow off loose dust particles since they can scratch the coatings or glass. A little dust or pollen on the glass will not effect your view though. Keep your equipment capped when not in use to keep dust and pollen from getting into the tube and on the back side of the lens as well as the front.

As far as the hazy look your lens has could it be condensation? I see it quite a bit in the summer months on mine. Say you have your house cooled to 68F and it's 90F outside, when you take the scope out a thin film of condensation will often form on the lenses hazing them over. It will sometimes even form on the tube itself though this often goes unnoticed. Given a few minutes the scope will equalize to the air and the condensation will slowly evaporate. The best way to keep this from happening is to keep the telescope capped until it equalizes to the air. It may take just a little longer but it's better for your scope.

The same happens in winter. Bring a cold scope into the warm air and it will quickly dew up. I cap them before I come in.

I take special care of my blocking filters. I'll cap them before going out from a cool house to a hot summer day and let them slowly adjust. Or put an eyepiece in before I go out. You don't want moisture on the blockers. Their soft coating will rust over time and you don't want that! Winter is the same way, cap them before you come in.

If the haziness you have isn't condensation or dust/pollen then you may have a coating issue. That means a return of your scope to Lunt for servicing. But it sure looks like a combination of dust and condensation to me!

Good luck on figuring this out.

James

P.S. Remember too that a large scope takes longer to equalize than a small one. An LS130MT is going to take longer to adjust than an LS60MT. The small scopes have the advantage here. This doesn't only affect condensation on your scope but your view through it!

[Rusted]

Try a 1" wide makeup blusher mop/brush after using the bulb blower.
These are wonderfully soft "mops" which makes watercolour, paint brushes feel like stiff, yard brooms.
They can be washed in diluted dishwashing detergent. Or wiped off on a fresh, moist, lens cleaner tissue.

My objective suffers from dewing [externally and internally] every time I open up after a cool night.
This is despite having a front mounted D-ERF filter.
I fitted dew bands around the back of the objective cell but it is a very slow process to clear the lens from scratch.

A hair drier speeds up the removal of external dew but hardly affects the internal variety.
So I play the the warm air on the main tube and the back of the cell.

Covering the lens helps. So I added thick insulation to a home made lens cap to go over the D-ERF.
But the telescope's main tube is cooling all night in the observatory.
This is despite wrapping the tube in closed cell, camping mattress foam when frosts are due.

Insulation only has value in slowing down temperature changes.
It can't stop it. An upward temperature change causes condensation on cooler objects.
Condensation attracts pollen and dust and can make it stick fast over time.

[H-Alpha]

Dear Bob, James, Chris,

Thank you all for your comments and advice.

My fault that since the beginning I did not make clear that I was not referring to the dust that the sunlight made so apparent in my photos. I can see no dust inside the scope, which is good. I also have to add that despite my hope this does not seem to be a "usual condensation". The surface that this haze occupies does not grow or decrease and also during this time of the year we have some 16 degrees Celcius outside as min (late in the night) and 30 degrees as maximum. BUT the late afternoon that I am using the scope the temperature is about 25 inside and 25-30 outside, so there is not so much difference. Above all, the hazy area is always there even when I check the scope inside the house after 24 hours staying only inside house conditions.

Therefore I am still puzzled regarding this hazy look of part of the lens (moisture? what else?), which is internal. I attach one more photo taken inside away from direct sunlight and I have indicated the hazy area.

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Could this haze/moisture/"permanent condensation" have developed during the scope's trip for USA to Greece?

All the best,
Alexandros

[DeepSolar64]

It should not have a hazy appearance outside of condensation. The lens should be clear.

[H-Alpha]

It should not have a hazy appearance outside of condensation. The lens should be clear.

Thanks a lot James. Since the hazy appearance is steady all hours of the day, either inside the house or outside, that means... it is not condensation and the lens has a problem. Do I understand it right?

Best wishes,
Alexandros

[DeepSolar64]

I would call Lunt Solar Systems. They should be able to tell you a course of action.

[marktownley]

Like others have said, contact Lunt and show them these images.

[Carbon60]

Definitely contact Lunt about this. In the meantime are you able to take a look with a magnifying glass or USB microscope to see if the cloudy patch is composed of condensation droplets, or if it is more of a film-like substance deposited on the lens, or damaged coating?

If it IS condensation, then maybe gently warming the objective lens with a hair dryer might evaporate the droplets.

Stu.

[MalVeauX]

Hi,

Definitely contact Lunt and send them a picture or two of this via email.

If it doesn't go away with heat from a hair dryer, then its not typical condensation, as noted above by Stu. I keep a hair dryer in my observatory because I always have to heat up my glass quickly to get rid of the condensation from my high humidity and large temperature deltas. So I see this commonly but it's usually the whole lens, not a section (and certainly not off center).

It could be a form of outgassing possibly. Strange that it's in that one location only. But this is probable that it's a residue from outgassing or similar and its effecting an area secondary to coatings, but ultimately is just deposit where the gas and water vapor was and evaporated and left a deposit of a typical of chemical in there that was the source of outgassing. So this may be something Lunt simply needs to handle. This is normal, it's not that it wasn't checked, it can happen when a scope is exposed to really high temperatures (this is common when shipping in trucks that are 140F+ or sitting in a super hot warhouse) or really cold temperatures and experience a large temperature delta with stagnant no-flow air (such as sitting for a period of time with large temp deltas).

I've opened up all my lenses (take out the retaining ring, the lenses will slide out) just being mindful of the spacer positions and order and direction of the lenses because I clean them a few times a year. If you're comfortable with that, you could open it open and see what that is between the lenses and where exactly it is. There's air gaps between the glass, so there's always room for something to happen between there. Constant exposure to sunlight ensures fungus doesn't take up home there (despite 100% always having fungus spores present just waiting to have water and darkness to activate). So this is why I clean mine fairly often, being in Florida, as fungus is my biggest threat with the humidity.

Best is to contact Lunt and see what they say. They will handle it. They have good support.

Very best,

[eroel]

Alexandros:
The best and safest move is to contact Lunt.
I think that it is fungus residues from a water vapor situation, I have had that phenomena many times with several refractor objectives that I have taken apart and cleaned the lenses (I was an amateur telecope maker that made lenses, mirrors, so had the means to take apart and test optics).
Best wishes.
Eric.

[H-Alpha]

Really thank you all, James, Mark, Stuart, Marty and Eric!
I have contacted Lunt one day after this post and wait for their answer.

@Stuart: Thnaks a lot for the idea I will have a closer look and will try macrophoto on it. May upload it if interesting for you and the other folks to inspect.
@Marty and Eric: Wow, are you opening and cleaning your refractors! Good to know that it can be done by an amateur, although you guys may be more profesionals than professionals... ;-) Anyway, you give me hope that it can be sorted in one way or another. Let's see what Lunt will say. At my level of experience I would not dare to open the scope and remove lenses... How to be certain that they will be parallel and homocentric when I re-install them... Apart the risk of accident...

Thank you once more!
Alexandros

[MalVeauX]

How to be certain that they will be parallel and homocentric when I re-install them... Apart the risk of accident...

Hi,

It's really just anxiety of not having done it. Once you do it, you'll think its simple. There's really nothing to mess up. Between the lenses there are spacers. They are not free floating. But they're the only thing to keep in mind when cleaning or moving things, so that you don't move or remove a spacer. The spacers produce a specific air gap between the lenses, that is needed. Other than that, the only other thing is orientation of the lenses. Usually they're marked on the sides to show which direction they should orient. I mark mine with black sharpie with arrows for direction. That's literally it. There's nothing else in there. The lenses sit in that cell with a single compression ring holding them down, maybe one or two rubber gaskets. Nothing fancy to it. They just sit in there and are held with pressure from a threaded ring. Practice on a cheap achromatic doublet (ie, a 50mm finder scope, seriously, take it apart and just see how they stack and are there, it will help, it's the same thing) and it will ease your nerves.

You'll want to be comfortable cleaning your stuff yourself anyways over time. That's a forever scope. You don't want to ship things like that around (and certainly don't ever ship your etalon if you don't have to, if it decontacts, you're in a world of hurt). Practice on something you don't care about to get some experience with disassembly, assembly, spacers, etc, and you'll be quite comfortable taking apart some basic refractor glass. Have fun with it!

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Now, recontacting an etalon pair.... that's something a little more difficult and nerve wracking!

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Very best,

[eroel]

Alexandros:
Just like Marty says, one gets used to clean optics (lenses and mirrors), specially if you are careful and use the proper cleaners and mark all your moves.
Telescope making experience helps, because you usually have a testing bench, Foucault tester, spherometer, micrometers, ronchi gratings, master flats, collimators, etc...
When you have these, you can even readjust the lens elements to improve rendition of the system.
One learns this, when you live far from the optical makers and when you don´t have a reliable shipping system and customs.
Best wishes.
Eric.

[H-Alpha]

Dear Marty and Eric,

Thnaks a lot. What you describe is certainly the path to follow in the near future. It will be even more fun to feel safe to enter deeply in my scopes and instruments. Nevertheless, As Marty wrote, I will have to experiment with a cheap scope first (that I do not have right now), in order to gain confidence and some experience.

In case Lunt propose me to fix it myself, so that the scope does not travel back to the US, or if the problem is not 'urgent' to resolve right now, I will certainly come back to you for step by step help..., if you can kindly be available.

All the best,
Alexandros

[marktownley]

Let us know what Lunt say...

[DeepSolar64]

I have taken apart air-spaced doublets in achromats before and cleaned them successfully. I would be terrified to get into my etalons!