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Cleaning the primary - 180mm Mak

DIY optics Maksutov catadioptric
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12 replies to this topic

#1 Paradoxdb3

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Posted 07 August 2020 - 07:28 PM

I hope this simple question has a short and simple answer...

Can I unscrew and remove the entire rear cell to gain access to the primary (and secondary from inside the tube) to clean the mirror?

#2 Paradoxdb3

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Posted 07 August 2020 - 07:46 PM

I just found a video on the removal of the corrector plate of a 127mm Mak. This was suggested to get at the primary. I'd still be interested in replies in case there's a better way.

#3 laixiaolue

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Posted 08 August 2020 - 12:46 AM

For most SCT or Mak, the rear cell is glued to the tube. You have no way to remove it.


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#4 luxo II

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Posted 08 August 2020 - 01:18 AM

Depends on the scope. The Intes ones have screws, undo these and the back pulls off. If yours has no screws Iโ€™d guess itโ€™s glued in place which is a no go.

 

If you can remove the corrector itโ€™s possible to wash the primary in-situ - load a hand spray with demineralised water and spray hard aiming at the mirror. Let it all drain out and dry for a day in a warm spot before reassembling.


Edited by luxo II, 08 August 2020 - 01:19 AM.

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#5 Paradoxdb3

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Posted 08 August 2020 - 01:28 AM

There are screws, but I suppose that doesn't mean it's not also glued. I'd better consider this carefully before going down this path. I should note that I can see a spot on the mirror, but it otherwise looks clean until I shine a flashlight down the tube at night. Probably not the best indicator... ๐Ÿ˜‚

Edited by Paradoxdb3, 08 August 2020 - 01:29 AM.


#6 bobhen

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Posted 08 August 2020 - 06:42 AM

I hope this simple question has a short and simple answer...

Can I unscrew and remove the entire rear cell to gain access to the primary (and secondary from inside the tube) to clean the mirror?

YES.

 

Remove the back plate (3 screws). Leave the mirror in the mirror assembly while you clean it. Put the plate back. You might have to re-collimate but it should not be off by much if at all.

 

Bob


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#7 Paradoxdb3

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Posted 08 August 2020 - 01:09 PM

YES.

Remove the back plate (3 screws). Leave the mirror in the mirror assembly while you clean it. Put the plate back. You might have to re-collimate but it should not be off by much if at all.

Bob


Okay, I shall try this. I was hoping that collimating wouldn't be off at all, but I suppose even getting the screw holes lined up there may be a slight shift in the entire cell. Anyway, thank you!

#8 Paradoxdb3

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Posted 08 August 2020 - 07:11 PM

I did it! I took off the front lens first, and cleaned the inside of the meniscus, as well as a quick cleaning of the secondary, which really didn't need much. I marked both the tube and the front cell with tape so that I remembered which way to line up the the lens when I put it back on. The rear cell didn't need markings, as the focuser and finderscope dovetail were my guides. Then I put the front cell back on and removed the rear. I dusted off the mirror and gave it a gentle wipe with a microfiber cloth. Just fogged it up where it needed a little extra. Then I used a vacuum cleaner to suck up any dust particles as I brushed off the mirror with a lens brush. Also vacuumed the inside of the tube and put the rear cell back on. It wasn't all that dirty to begin with, so it's not actually much cleaner now. Of course, shining a flashlight down the tube shows every tiny particle of dust on the mirror. But I'll never get rid of all that. But now I can say that I've done it! And it wasn't even that scary.

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#9 charlesgeiger

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Posted 09 August 2020 - 02:05 AM

Be very careful, if you clean the mirror and miniscus with anything that rubs (like microfiber), you can introduce micro scratches to the surfaces.  Sounds like you were successful.  I have read that many cat scopes do not have protective overcoating on their interior coatings (primary and secondary or spot) so the aluminum can easily come off or be scratched.  Just be careful in the future and read Dr. Clay's mirror cleaning information.

Charlie



#10 Paradoxdb3

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Posted 09 August 2020 - 11:02 AM

Be very careful, if you clean the mirror and miniscus with anything that rubs (like microfiber), you can introduce micro scratches to the surfaces.  Sounds like you were successful.  I have read that many cat scopes do not have protective overcoating on their interior coatings (primary and secondary or spot) so the aluminum can easily come off or be scratched.  Just be careful in the future and read Dr. Clay's mirror cleaning information.

Charlie

 

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#11 Paradoxdb3

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Posted 09 August 2020 - 11:03 AM

I feel like I was successful. The mirror looks better than it did before, anyway.

#12 Peter Besenbruch

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Posted 09 August 2020 - 04:04 PM

I feel like I was successful. The mirror looks better than it did before, anyway.

I like your second picture.


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#13 Paradoxdb3

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Posted 09 August 2020 - 04:54 PM

I like your second picture.


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