Answer by LUNT re: Hazy area on front internal lens of 130MT

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Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by H-Alpha »

Dear all,

I have recently posted a message regarding a hazy area that is visible permanently on one of the internal front lenses of my Lunt130MT. I recently bought and received that scope from Lunt through OPT and I obsreved the hazy area since the first day I took it out in the sunlight. The hazy area never changed since, in shape or are covered or anyhow. Photos are available in the older post here:

viewtopic.php?p=294029#p294029

Some people who kindly answered that message asked me to post the answer by Lunt. Here is what I got:

"Thank you for your email. We also appreciate the photos that you have included. We have not received reports of this haze in previous shipments to customers. We believe perhaps in shipment this occured due to possible temperature changes while in transit. Although, we are not entirely sure. As you mention the haze appears to be internal you can access the objective by removing the dew shield. Once removed you can unthread the objective to access the internal surface for cleaning. To clean it you can use isopropyl alcohol applied to a plain white tissue or lens paper. If you have access to methanol that is great as well. That is what we use here at the factory. I hope this is helpful! Please let me know if you have any other questions".

The scope is fully funcional and you have seen some results posted here. I now have 3 options, I think:

1) Ask to send back the scope to be fixed and receive it with the lens properly cleaned or replaced.
(Apart the time and pain it will take and all the efforts of all kind,the risk in this case is that after it has been cleaned, it will have to travel again from the USA to Greece, and due to temperature differences, the problem could appear again)

2) To try to open the scope and to clean the lens after asking more detailed instructions by Lunt and also ask to know what will happen in case of any further problem... How I will be covered in that case.
(It is my first refractor and with zero previous experience and not even available youtube tutorials - I didn't find any, at least not for Lunt scopes -, it looks pretty scary to open such an expensive scope. From another point of view, I would like to start feeling more confortable with opening and cleaning my scope, but isn't a bit too early?)

3) Do nothing, and live with the problem, as long as I see no effect on image quality

I would like to kindly ask your advice, ideas and views. What would you have done in my place?

I tried just to remove the dew shield as Lunt proposed, but did not even find how this can be done... I suppose the next steps should be even more difficult and may need special tools? Knowing nothing (did not even now that the dew shile was retractable until two days ago, and if useful during daylight observation...) I originally hoped that the frontal filter would go away with the dew shield and I would have direct access to the haze problem...

Therefore, if anyone here has opened a Lunt of this type before, and could give me an idea on how exactly I could reach the lens with the haze step by step, it would be a great help to understand if I can take the risk or not.

People here have already kindly given me basic istructions on how to deal with cleaning refractor lenses, but aparently at my zero level of experience, I need specific details for this Lunt scope (that I will ask from Lunt anyway, after reading your comments).

Marty wrote "It's really just anxiety of not having done it. Once you do it, you'll think its simple" and together with other very helpful details proposed to get experience with a cheap refractor. He (and Eric who also supported his view) are absolutely right, but I have no other refractot at the moment...

Thanks a lot in advance for any comment you would like to make!

Best wishes,
Alexandros
Last edited by H-Alpha on Sun Jun 06, 2021 12:41 am, edited 1 time in total.


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Re: Dilema re: Hazy area on new Lunt's front internal lens

Post by DeepSolar64 »

Maybe you could call Lunt and have them walk you through it. Or they could at least tell you how it's done in detail.


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by Montana »

You sound just like me, I know exactly how you feel. Astronomy people always talk about just do this and just do that, but when it is very expensive it is not so simple. These things make me freak out. However, the folks on here are very good and some have even done videos so you can follow it step by step. I would never have taken my PST apart without the help here. However, I still found it extremely stressful. But not make folks have a 130 compared to a PST ;)

Do you know of any experienced telescope technicians in your area who could help you? The best place for help is a local astronomy club as there will always be some old chap who has built telescopes all his life and will have the tools. The correct tools make all the difference.

Good luck :)

Alexandra


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by marktownley »

Hi Alexandros.

If it was me it would be disassembled, but, if this is something you are not comfortable then it is not a realistic solution for you. Like Alexandra says, maybe there is a local astro society with suitably experienced person who is happy taking scopes apart.

Have you tried applying some heat (hair dryer on cool setting) to see if it 'evaporates? Don't apply high heat.

Mark


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by H-Alpha »

Thank you all James, Alexandra and Mark, for reading this long post and offering help through advice!

@James: I will certainly!
@Alexandra: Very useful idea! Trying to figure out how the dew shield could come out, I realized that perhaps special tools are used. I will call a local vendor/service who is very friendly (unfortunately at a distant town) to ask about tools and nice persons/experienced amateur astronomers in Athens that could help.
@Mark: I did not apply heat so far. I may be wrong, but thought that given that this is not on the first lens, but the second some mm behind, a hair-drier may not be able to create higher heat than the sun is already creating during captures. Am I wrong?

Best wishes,
Alexandros


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by MalVeauX »

H-Alpha wrote: Sat Jun 05, 2021 2:05 am
1) Ask to send back the scope to be fixed and receive it with the lens properly cleaned or replaced.
(Apart the time and pain it will take and all the efforts of all kind,the risk in this case is that after it has been cleaned, it will have to travel again from the USA to Greece, and due to temperature differences, the problem could appear again)

2) To try to open the scope and to clean the lens after asking more detailed instructions by Lunt and also ask to know what will happen in case of any further problem... How I will be covered in that case.
(It is my first refractor and with zero previous experience and not even available youtube tutorials - I didn't find any, at least not for Lunt scopes -, it looks pretty scary to open such an expensive scope. From another point of view, I would like to start feeling more confortable with opening and cleaning my scope, but isn't a bit too early?)

3) Do nothing, and live with the problem, as long as I see no effect on image quality

I would like to kindly ask your advice, ideas and views. What would you have done in my place?

I tried just to remove the dew shield as Lunt proposed, but did not even find how this can be done... I suppose the next steps should be even more difficult and may need special tools? Knowing nothing (did not even now that the dew shile was retractable until two days ago, and if useful during daylight observation...) I originally hoped that the frontal filter would go away with the dew shield and I would have direct access to the haze problem...

Therefore, if anyone here has opened a Lunt of this type before, and could give me an idea on how exactly I could reach the lens with the haze step by step, it would be a great help to understand if I can take the risk or not.

People here have already kindly given me basic istructions on how to deal with cleaning refractor lenses, but aparently at my zero level of experience, I need specific details for this Lunt scope (that I will ask from Lunt anyway, after reading your comments).
Hi,

Shipping it back and forth, risks the same thing happening both times. As mentioned in your previous thread and this thread, this happens commonly with big temperature deltas. It's fine though and easy to clean. It's just apprehension of not having done it before. I highly recommend you dissemble a cheaper smaller refractor, like a guidescope or something, to get a comfort level.

Personally I would just clean it myself. It's not easy to damage these optics. The coatings are very robust. The glass is robust. The only things you can do wrong really is put a horrible chemical on it (but you were told which chemicals to use) and assembling it incorrectly (as in putting the lenses in the wrong order or face direction relative to each other). That's really it, short of dropping things down a well. These big hunks of thick glass are not fragile. If you wear glasses, I bet you touch and rub them all day. These are much bigger, thicker, even more robust. They're not something to get too worried about. Again, its apprehension from not having done it before. After you do it once or twice, you'll wonder why you were concerned at all in the first place. Refractor optics are dead simple.

Take off the dew shield completely as they instructed.

The holding cell is at the end of the tube there, it should unthread (counter clock wise) and open up. There will be a rubber gasket likely under the threaded ring that is holding them down. Remove it. Use gloves, and hold the glass in place, then simply turn it all upside down, while holding it, and the lenses will gently lower out of the cell. Pay close attention to the order and direction of the 3 elements and any spacers. It's very helpful to mark the sides (1, 2, 3; and arrows of the face towards the sun so you know which direction they face and in what order). Use the chemicals Lunt told you and use cotton balls or cotton wipes to clean. Gentle dabbing will do it. Air dry. Rokkit blow off debris after dry. Clean as any other lens would be cleaned if you see smudges or oils, etc.

Reassemble in same order and facing as originally was. Using gloves, hold the objective stack in your hand with the towards-the-sun facing in your palm of your hand. With your hand hand, lower the holding cell of the tube down onto the stack gently. Raise the lenses up into the cell with your gloved fingers until they touch the back of the cell. While holding the lenses, gently turn the scope over so the cell is facing up now, so the lenses will sit in the cell to gravity. Ensure they are flat and that any spacers are where they should be. Put the rubber gasket back around the edge of the lenses. Thread back down the threaded retaining ring, slowly. You can gently shake the lens cell a bit to settle any movement or see any movement of anything not flat or held up anywhere. Thread down the ring until the lenses do not move. Give it a little shake to see if anything is free floating still. Gently thread down a little tighter. Do not over tighten.

Check collimation on an artificial star (point light source) or real star at your convenience.

Very best,


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by marktownley »

H-Alpha wrote: Sun Jun 06, 2021 2:54 pm @Mark: I did not apply heat so far. I may be wrong, but thought that given that this is not on the first lens, but the second some mm behind, a hair-drier may not be able to create higher heat than the sun is already creating during captures. Am I wrong?
Try the hair dryer on low heat, it may take a while. The sun won't heat the glass when its pointing at it, the glass is transparent to the suns rays ;)


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by krakatoa1883 »

Be very careful in dismantling that kind of objective. Lenses in triplets are usually held on the optical axis by means of radial screws on the the cell that push on the lens edges, check if this is the case by removing the dew shield. If yes, you will need to loose these screws before to remove the lenses. The problem here is that triplets are extremely sensitive to any lateral shift of the lenses, if not properly reassembled with all the three axes exactly aligned the objective will show coma and astigmatism at the center of the field which will degrade images.

You will need an artificial star to check lens positions and to adjust them accordingly, it would be impossible to do this while looking at the sky. My suggestion: with the tube in horizontal position just fix the first and the rear lenses with their screws then try to reach collimation by shifting the central lens. Remember when a screw is tightened the opposite (radially) shall be loosened.


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by RodAstro »

Hi Alexandros

Looking at the scope, pictures on the internet, and Lunt,s explanation for dismantling I have a feeling it is easier than you think.
Firstly the black ring on the back of the dew cap needs unscrewing, it does have two small holes in it for a tool but you should be able to unscrew it by pushing the dew cap fully forward against its stop and holding the black ring tight with the tube whilst pushing it against the stop, then unscrew the dew cap counter clockwise from the black ring.

Once you have the dew cap off you will find the stop for the ring is actually the lens cell holding the lenses. If this is the case DO NOT remove the lenses from the cell (I don't think Lunt would ever advise you to do that unless you are very good with optics) Just unscrew the whole lens cell counter clockwise from the telescope tube keeping all the lenses in place in the cell.

You can now clean the rear lens element as Lunt say.

Then just screw the lens cell back onto the tube being carful not to cross thread it and everything will go back to its original alignment.
Nothing has to be very tight, just hand tight.

A good tool for getting grip whilst holding things like the black ring is one of the sticky rubber mats used to stop your cell phone from sliding around on your car dash board, two are even better one in each hand, they give you lots of grip. They are soft so should not mark the finish.

I would clean this mark off as over time it will damage the lens coatings no matter how hard they are.

When you look at the job you have to do all it is like is removing two (very large) focuser extension tubes and refitting them and we all do that no problem.

I hope this helps with confidence and the job in hand.

Cheers Rod


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by H-Alpha »

Thank you very much Marty, Mark, Raf, Rod, for your precious comments, advice and views!
Your detailed posts are like a encyclopedia on the subject to help me move step by step carefully (or not to move if a risky obstacle is foreseen).

Tomorrow I will contact also Lunt again, being equipped with all the knowledge you passed to me and after their new answer and also after enjoying the scope the next three sunny weeks before I leave for some expeditions offshore, I will attempt to reach the haze and repair it.

Thank you all once more!

Best wishes,
Alexandros


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by thesmiths »

Hi Alexandros, there is also the option of dealing with the European distributor based in Germany. Within the EU, it would be easier to ship things. I have met with the European distributor at AstroFest in London and they seem very knowledgeable. I have taken apart many telescopes myself but even I would be hesitant to do so with such a big and expensive one.

If there are big astronomy trade shows in Athens, you could even make an appointment to meet them there and bring your telescope so they can look at it in person and do some maintenance on the spot.

Otherwise, I would recommend the course of action suggested by Mark and use heat to drive out condensation. (Fungus typically has a particular cobweb-like appearance and also takes a long time to develop so I doubt if it's fungus.) Perhaps a better way to heat the telescope is to cover the telescope in some heavy dark cloth and leave it to sit all day in the warm Greek sunshine. The should heat the whole telescope up uniformly and get it to a good temperature. You should probably leave the lens cap off to encourage moisture to escape and remove any equipment at the back since there is no need to heat that.

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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by RodAstro »

Hi Alexandros

I feel a bit silly now to not think of this, of course it is the modular scope so you can remove the rear end of the scope to just the tube.
And as suggested let any moisture evaporate, I would imagine any moisture has already gone by now and left a residue, maybe salt if it came by sea, or some oil from manufacturing grease.
To clean this off you could work from the focuser end using wood pole with cotton wool covered in a cleaning cloth and taped on, you really need two of these one sprayed with isopropyl alcohol to gently clean and the pole to just dry the isopropyl.
The only thing I would be careful of, is if there is any manufacturing particles inside, normally aluminium from thread cutting, if you get these on your cloth they could scratch the lens.

One question is it Lunt USA you have contacted or was it a Lunt dealer you bought the scope from?

Cheers Rod


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by H-Alpha »

Thank you very much(!!!) Douglas and Rod for your further practical and detailed advice!
The 'advanced heating method' makes it much easier, and if this does not work, reaching the lens from behind is another option.
I am not sure if I can reach the dirty lens, though; or if another lens will be between me and the dirty lens. Will see...

@Douglas: There are no big astro-shows in Athens :-( and the only dealer (representing Bresser as well) is in a town in the north of Greece. If I cannot manage anything myself, I may have to visit them. It will be my last option to make this distant (for Greece's scale ;-) ) trip.

@Rod: Since the beginning (before the purchase) I was contacting Lunt USA. I purchased the scope from OPT (USA), since Lunt are not selling scopes in Europe directly (but through Bresser Germany, who have unreasonable prices...; I could never have been able to buy it from them). OPT never answered my email. Even during the purchase they had some difficulty to answer emails, so I had called them a couple of time.

Many, many thanks once more and best wishes,
Alexandros

PS: Will let you know how things went at the end... :-)


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by minhlead »

MalVeauX wrote: Sun Jun 06, 2021 3:22 pm
H-Alpha wrote: Sat Jun 05, 2021 2:05 am
1) Ask to send back the scope to be fixed and receive it with the lens properly cleaned or replaced.
(Apart the time and pain it will take and all the efforts of all kind,the risk in this case is that after it has been cleaned, it will have to travel again from the USA to Greece, and due to temperature differences, the problem could appear again)

2) To try to open the scope and to clean the lens after asking more detailed instructions by Lunt and also ask to know what will happen in case of any further problem... How I will be covered in that case.
(It is my first refractor and with zero previous experience and not even available youtube tutorials - I didn't find any, at least not for Lunt scopes -, it looks pretty scary to open such an expensive scope. From another point of view, I would like to start feeling more confortable with opening and cleaning my scope, but isn't a bit too early?)

3) Do nothing, and live with the problem, as long as I see no effect on image quality

I would like to kindly ask your advice, ideas and views. What would you have done in my place?

I tried just to remove the dew shield as Lunt proposed, but did not even find how this can be done... I suppose the next steps should be even more difficult and may need special tools? Knowing nothing (did not even now that the dew shile was retractable until two days ago, and if useful during daylight observation...) I originally hoped that the frontal filter would go away with the dew shield and I would have direct access to the haze problem...

Therefore, if anyone here has opened a Lunt of this type before, and could give me an idea on how exactly I could reach the lens with the haze step by step, it would be a great help to understand if I can take the risk or not.

People here have already kindly given me basic istructions on how to deal with cleaning refractor lenses, but aparently at my zero level of experience, I need specific details for this Lunt scope (that I will ask from Lunt anyway, after reading your comments).
Hi,

Shipping it back and forth, risks the same thing happening both times. As mentioned in your previous thread and this thread, this happens commonly with big temperature deltas. It's fine though and easy to clean. It's just apprehension of not having done it before. I highly recommend you dissemble a cheaper smaller refractor, like a guidescope or something, to get a comfort level.

Personally I would just clean it myself. It's not easy to damage these optics. The coatings are very robust. The glass is robust. The only things you can do wrong really is put a horrible chemical on it (but you were told which chemicals to use) and assembling it incorrectly (as in putting the lenses in the wrong order or face direction relative to each other). That's really it, short of dropping things down a well. These big hunks of thick glass are not fragile. If you wear glasses, I bet you touch and rub them all day. These are much bigger, thicker, even more robust. They're not something to get too worried about. Again, its apprehension from not having done it before. After you do it once or twice, you'll wonder why you were concerned at all in the first place. Refractor optics are dead simple.

Take off the dew shield completely as they instructed.

The holding cell is at the end of the tube there, it should unthread (counter clock wise) and open up. There will be a rubber gasket likely under the threaded ring that is holding them down. Remove it. Use gloves, and hold the glass in place, then simply turn it all upside down, while holding it, and the lenses will gently lower out of the cell. Pay close attention to the order and direction of the 3 elements and any spacers. It's very helpful to mark the sides (1, 2, 3; and arrows of the face towards the sun so you know which direction they face and in what order). Use the chemicals Lunt told you and use cotton balls or cotton wipes to clean. Gentle dabbing will do it. Air dry. Rokkit blow off debris after dry. Clean as any other lens would be cleaned if you see smudges or oils, etc.

Reassemble in same order and facing as originally was. Using gloves, hold the objective stack in your hand with the towards-the-sun facing in your palm of your hand. With your hand hand, lower the holding cell of the tube down onto the stack gently. Raise the lenses up into the cell with your gloved fingers until they touch the back of the cell. While holding the lenses, gently turn the scope over so the cell is facing up now, so the lenses will sit in the cell to gravity. Ensure they are flat and that any spacers are where they should be. Put the rubber gasket back around the edge of the lenses. Thread back down the threaded retaining ring, slowly. You can gently shake the lens cell a bit to settle any movement or see any movement of anything not flat or held up anywhere. Thread down the ring until the lenses do not move. Give it a little shake to see if anything is free floating still. Gently thread down a little tighter. Do not over tighten.

Check collimation on an artificial star (point light source) or real star at your convenience.

Very best,
Thanks for the very detailed guid, Marty. But wouldn't opening and cleaning the optics messes up the collimation of the lens? I have cleaned my doublet and reassembled it without problem but a triplet would be very hard to recollimate if its off is it not?


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by DeepSolar64 »

Perhaps a better way to heat the telescope is to cover the telescope in some heavy dark cloth and leave it to sit all day in the warm Greek sunshine. The should heat the whole telescope up uniformly and get it to a good temperature. You should probably leave the lens cap off to encourage moisture to escape and remove any equipment at the back since there is no need to heat that._thesmiths

How about putting it in a closed up car when the sun is out!


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Re: Answer by LUNT re: Hazy area on front internal lens of 130MT

Post by MalVeauX »

minhlead wrote: Wed Jun 09, 2021 3:58 am
Thanks for the very detailed guid, Marty. But wouldn't opening and cleaning the optics messes up the collimation of the lens? I have cleaned my doublet and reassembled it without problem but a triplet would be very hard to recollimate if its off is it not?
Hi,

Could it mess up collimation? Sure. But that applies to all optics if you do anything with them internally. Wiping a mirror can throw off collimation. But odds are, it won't, with a refractor. It's pretty difficult to throw off collimation on a refractor unless something is not returned to its original placement, like a spacer, or a lens not seated fully, or something on the spacer (grain of sand, etc). But cleaned refractor optics, even triplets, assembled and returned to the holding cell is more likely to be still collimated unless they're not seated fully or if the cell itself moved (like those collimatable lens holding cells with push/pull bolts). I wouldn't worry too much about this. Clean a few and reassemble, even a triplet, and it will be fine. It's not like the lenses have to be clocked or rotated exactly, etc. That doesn't matter. Just placement in the cell with appropriate orientation and no induced tilt or lack of space due to not cleaning or the spacer moving or having increased thickness, etc. The biggest issues are usually simply putting them back together in the cell the way they came out. There's always tolernace on the lenses in the cell to wiggle a bit, but as long as all the lenses are stacked, and the whole stack moves a tiny bit in the cell, it's likely going to stay well collimated. You check on an artifcial star or real star, and if it's off, just loosen the holding cell and just ensure the lenses are fully seated and not tilted bodged on a side thread or something in the cell.

Just my experience with fracs though, I'm comfortable with them. They're pretty robust with this stuff. Newtonians and SCT are far more fussy in my opinion.

Very best,


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