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Collimating refractor

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#1 dron2015

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Posted 21 October 2019 - 08:11 PM

Dear fellow astronomers,

 

May I have quite a newbie question?

 

My main caliber has got some dust on the inner side of the objective recently (do not ask) and recently has got new focuser. it seems that I will have to remove the lens cell, clean it and when assemble back. so the scope surely will lose its collimation. Previously, I have not performed such an art. So, here are my questions:

 

1. What tools exactly do I need to have to collimate my refractor?  I have read a couple of CN topics re collimating refractors, including "adventures in Refractor Collimation", so I have a feeling that I have high level understanding (in general) of the steps to undertake. But what would be the best options for the tools? Reasonably priced - not sure if I want to go such great instruments as Howie Glatter mostly due to its high prices - for me it is (hopefully) going to be one time procedure, so do not want to expense a lot of funds, unless, you advise against this approach.

1.1. Laser collimator to ensure that focuser is aligned.  Which exactly?

1.2. Cheshire collimating tool, to fine tune the objective. Which exactly?

1.3 something else?

Or it is not a good idea for a newbie to explore this route and better to seek for help at local astronomy association experts?

 

2. Also, how do you remove the dust in between of the lenses in the cell? I am not going to disassemble the cell, but since the dust somehow appeared there - perhaps it is possible to remove? vacuuming or vice verse purging the compressed air? if the latter - what is the device? how exactly to do so? it is the masterpiece by LZOS (air spaced triplet).

 

Many thanks in advance!

 

collimating.jpg

 

 

Best,

Andrey



#2 Kunama

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Posted 21 October 2019 - 08:26 PM

Dear fellow astronomers,

 

May I have quite a newbie question?

 

My main caliber has got some dust on the inner side of the objective recently (do not ask) and recently has got new focuser. it seems that I will have to remove the lens cell, clean it and when assemble back. so the scope surely will lose its collimation. Previously, I have not performed such an art. So, here are my questions:

 

1. What tools exactly do I need to have to collimate my refractor?  I have read a couple of CN topics re collimating refractors, including "adventures in Refractor Collimation", so I have a feeling that I have high level understanding (in general) of the steps to undertake. But what would be the best options for the tools? Reasonably priced - not sure if I want to go such great instruments as Howie Glatter mostly due to its high prices - for me it is (hopefully) going to be one time procedure, so do not want to expense a lot of funds, unless, you advise against this approach.

1.1. Laser collimator to ensure that focuser is aligned.  Which exactly?

1.2. Cheshire collimating tool, to fine tune the objective. Which exactly?

1.3 something else?

Or it is not a good idea for a newbie to explore this route and better to seek for help at local astronomy association experts?

 

2. Also, how do you remove the dust in between of the lenses in the cell? I am not going to disassemble the cell, but since the dust somehow appeared there - perhaps it is possible to remove? vacuuming or vice verse purging the compressed air? if the latter - what is the device? how exactly to do so? it is the masterpiece by LZOS (air spaced triplet).

 

Many thanks in advance!

 

attachicon.gif collimating.jpg

 

 

Best,

Andrey

Andrey, 

I have just been through this today, it all depends on which model, which cell  etc.

With the TMB-LZOS 152 the cell unscrews from the countercell that allows you to clean the front of G1 and rear of G3 element.  There is no way for getting into the cell to do any other cleaning without disturbing not only the collimation of the cell but also the alignment of the lenses.  Are you sure the dust is within the lens elements?

 

I checked the collimation today before and after cell removal and saw no change.

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#3 dron2015

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Posted 21 October 2019 - 08:45 PM

Dear Matt,

 

Thanks much! Mine ilooks the same with S/N quite close to that of you lens! smile.gif

 

However, I do not see the pull and push screws on yours.. I see the thread on yours! hmmm perhaps mine is a bit different in the cell structure.

 

i thought that I saw small holes in the cell sealed with smthng white - to let the air move in and out and no dew accumulates, will have a look again!

 

Best,

Andrey


Edited by dron2015, 21 October 2019 - 09:12 PM.


#4 Jeff B

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Posted 21 October 2019 - 08:48 PM

You have the right tools in mind but like Matt said, leave the inner dust alone.  Also being a newbie, shining a bright light into the objective and viewing off axis WILL show some debris so I have to ask, how "bad" is it?  A few specks?  Even a couple of dozen specs, while annoying, will not affect the performance of the lens. 

 

Regarding the laser to use, just make sure that when you put the laser snugly in the eyepiece holder, shine it on a wall and then rotate the laser, the beam on the wall stays put and does not "orbit".  If it does, the laser itself is not collimated.  Get one that is.  Also what scope is it and does it have lens cell and focuser collimation features?

 

Jeff


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#5 Jeff B

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Posted 21 October 2019 - 08:50 PM

Dear Matt,

 

Thanks much! Mine ilooks the same with S/N quite close to that of you lens! smile.gif

 

However, I do not see the pull and push screws on yours.. hmmm perhaps mine is a bit different in the cell structure.

 

i thought that I saw small holes in the cell sealed with smthng white - to let the air move in and out and no dew accumulates, will have a look again!

 

Best,

Andrey

Leave those alone!!!

 

Those are the radial screws that center the lens elements!!

 

Jeff


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#6 dron2015

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Posted 21 October 2019 - 08:51 PM

Thanks much, Jeff!

 

the inner part has some than a couple of dozens frown.gif

 

regarding the “small holes” - thanks much Jeff for warning!

 

Best,

Andrey


Edited by dron2015, 21 October 2019 - 08:52 PM.


#7 Jeff B

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Posted 21 October 2019 - 08:58 PM

Thanks much, Jeff!

 

the inner part has some than a couple of dozens frown.gif

 

Best,

Andrey

That's too bad. 

 

If you are in the EU contact Markus Ludes at APM for service.  Well, even if you are not in the EU, contact him.  There will a good sized fee but he's a good guy, will do a good job for you and if it is a 152mm F7.9 LZOS triplet, the charge will be well worth it..  I have had several APM/TMB LZOS triplets and they were all truly excellent lenses.  

 

Jeff


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