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Celestron SCT cleaning

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#1 Raiders

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Posted 26 May 2020 - 09:13 PM

Looking for product and process to clean the front glass of the SCT. Curious since this glass is a lot larger than an eyepiece. Looks like water spots. I don’t want to make it worse by cleaning front glass w/o the knowledge of the process.

#2 Michael_Swanson

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Posted 26 May 2020 - 09:19 PM

Here is my process:

https://www.nexstars...OpticsGlass.htm

 

And if you feel the need to clean the inside surface of the corrector plate:

https://www.nexstars...ctorRemoval.htm

 

Best regards,
Mike Swanson
https://www.NexStarSite.com


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#3 Tulloch

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Posted 26 May 2020 - 10:17 PM

I used this method - I couldn't get the Kodak Photo-Flo solution, but seems to work fine without it...

 

http://arksky.org/asoclean.htm

 

Andrew


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#4 JerseyBoy

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Posted 27 May 2020 - 07:26 AM

I have spots on the inside of the corrector plate which are showing up on photos (can get rid with flat frames but worried it might be mould and eat the coating or etch the glass), so having read numerous articles and watched numerous videos on the process, I've ordered some distilled water and Isopropyl Alcohol 99.9% Pure.



#5 JerseyBoy

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Posted 27 May 2020 - 07:29 AM

Here is my process:

https://www.nexstars...OpticsGlass.htm

 

And if you feel the need to clean the inside surface of the corrector plate:

https://www.nexstars...ctorRemoval.htm

 

Best regards,
Mike Swanson
https://www.NexStarSite.com

 

Hi Mike,

 

Why do people remove the glass, rather than remove the whole frame from the tube? I would have thought it less dangerous and more accurate for replacement to take the frame off?



#6 mclewis1

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Posted 27 May 2020 - 08:03 AM

Bolts holding the corrector cell to the tube often have nuts on the inside. You also run the risk of getting the cell wedged a bit when you replace it (bad for optics alignment). Many folks however do report that removing and replacing the cell from the tube has gone very well with everything going back into place well.


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#7 JerseyBoy

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Posted 27 May 2020 - 08:27 AM

Thanks Mark. I can see there could be pitfalls then. But to me it seems easier than trying to centralise and perfectly replace the glass. Screws/bolts on the cell should go back to the position they were in before, i.e. the tolerance should be very close so long as you put the same screw/bolt back in the same hole, so very little chance of not getting it back to the position it was before taking it off.

 

I suppose if there are nuts on the inside and you get the cell off, you'd just have to take the glass out anyway (which you were going to do) and put the cell back on, so not a big issue, just a bit more time. If you undo a screw/bolt and the nut on the inside starts going round in circles, you just take the glass out anyway, and tighten the screw/bolt up again

 

What makes me wonder is all the padding around and in front of the glass, getting it all back accurately, when you might just be able to take the cell off and leave the padding alone.


Edited by JerseyBoy, 27 May 2020 - 08:28 AM.


#8 Raiders

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Posted 27 May 2020 - 11:01 AM

Can automotive microfiber cloths be used instead of tissues

#9 mclewis1

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Posted 27 May 2020 - 11:36 AM

Can automotive microfiber cloths be used instead of tissues

The material isn't the issue ... the guideline is more to use single use wipes. Never reusing a wipe means there's no chance of grit being carried by the wipe over the optic.

 

Yes I know microfibre cloths are included with pairs of glasses and many binoculars, but in general with any fine optical surface you don't want to use a reusable wipe, just a one time one.



#10 Tulloch

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Posted 27 May 2020 - 04:30 PM

The material isn't the issue ... the guideline is more to use single use wipes. Never reusing a wipe means there's no chance of grit being carried by the wipe over the optic.

 

Yes I know microfibre cloths are included with pairs of glasses and many binoculars, but in general with any fine optical surface you don't want to use a reusable wipe, just a one time one.

I think the theory here is, Telescope optics are expensive - tissues 'aint. lol.gif 


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#11 Michael_Swanson

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Posted 27 May 2020 - 10:46 PM

The material isn't the issue ... the guideline is more to use single use wipes. Never reusing a wipe means there's no chance of grit being carried by the wipe over the optic.

 

Yes I know microfibre cloths are included with pairs of glasses and many binoculars, but in general with any fine optical surface you don't want to use a reusable wipe, just a one time one.

Also, microfiber cloths are not very absorbent so you will end up with streaks.

 

Best regards,
Mike Swanson
https://www.NexStarSite.com



#12 JerseyBoy

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Posted 28 May 2020 - 06:18 AM

And the videos I've watched you dab, you don't rub. Dabbing picks up the dirt/contamination, whereas rubbing drags it (eeeek, just the thought of it!!) across the optical surface. Look at any crystal glass in the light for micro-scratches, then translate that to your telescope optical train.


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#13 ZS1RA

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Posted 31 May 2020 - 04:31 PM

Looking for product and process to clean the front glass of the SCT. Curious since this glass is a lot larger than an eyepiece. Looks like water spots. I don’t want to make it worse by cleaning front glass w/o the knowledge of the process.

I only use this method, link below. Willie is a fellow countryman who works at the Southern African Large Telescope (SALT) in Sutherland, South Africa. His method is the same used on all the large telescopes, used for research, on the precinct.

 

The most difficult part of the process is to stop yourself from turning the cotton wool balls over for a second wipe and wiping before the dabbing and washing is complete. I use about 3 drops of dishwashing liquid in about 5 liters of water.
 

I know there are experts who recommend using tissue but I won’t. As a youngster we used tissue paper to polish aluminum bit on our motor cycles. Worked a treat because it’s abrasive, I’m told it the microscopic bits of wood pulp that makes it perfect for polishing. However, I’m no expert but I would not use tissue.

 

You will be amazed at the results and your mirror will not have a single streak after you are done.

https://m.youtube.co...66yIuD3cMk&t=8s


Edited by ZS1RA, 31 May 2020 - 04:32 PM.

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#14 JerseyBoy

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Posted 01 June 2020 - 03:38 AM

ZS1RA that's one of the many videos I watched.

 

I've gone for Isopopyl Alcohol (50ml from Aquathree.co.uk) and Pure Distilled Water (1107ml from Aquis Labs via Karowi on  Amazon.co.uk) to make a 60/40 mix, to ensure no residue after cleaning, as per https://www.cloudyni...plate-cleaning/


Edited by JerseyBoy, 01 June 2020 - 03:39 AM.

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