Is the mirror dead 10inch Meade LX200 SCT

[looking up (Steve)]

Hello chaps
I was looking over an old scope the other day getting ready to give it a corrector and mirror cleaning due to some old mould on mirror.
I gave it a nice light cleaning with dish washing liquid and distilled water and cotton buds. Took an image looked fine then I looked again at another angle and was amazed what i saw.
Is this mirror stuffed with scratches or is it just the UHTC coatings.
First image looks fine

Your comments would be appreciated.

Thanks in advance cheers Steve

[Dave882 (David)]

Hi Steve
I reckon there’s still hope for that mirror. I’d be extremely surprised if all of those markings are scratches- it looks more like marks from the cleaning.
There’s a good thread recently here on IIS that covers a number of cleaning techniques for mirrors. With marks on a sct primary, a 10” you might still need to disassemble the rear of the scope to access and do a proper clean. I would use some proper lense cleaning fluid, and a soft cloth, or cotton cleaning wipes that do not leave any swirls or sleeks.

[iborg (Philip)]

Hi Steve


I recently cleaned an Meade 8" SCT. After the first go, I also had plenty of marks somewhat similar. I wound up using very dilute dishwashing liquid in tap water, rinsed off with tap water, then distilled water. Eventually came up nicely. Oh, and cotton balls, plenty of them.


I removed then corrector plate to access the main mirror. Now I have to check the collimation. If it's, out I'll fit the Bob's knobs that I've had for years now.





Philip

[Stefan Buda]

I agree with Philip and David. What you see there is just cleaning residue.
It would be very difficult to properly clean the mirror without removing it completely from the assembly.

[wayne anderson (Wayne)]

Cleaning SCT mirror on Meade LX200 with Internal wash bay

I needed to clean the primary mirror of the 12" LX200 but did not want to remove the primary mirror so I made this water proof internal wash bay for cleaning the mirror using a sheet by of 0.5mm thick plastic. It takes around 20 minutes to make and install the wash bay and 5 minutes to wash the primary mirror, it was easy and worked very well. (see the photos attached)

After very carefully marking the corrector position remove the corrector

1. Measure the circumference of the primary mirror using a strip of paper or cardboard and mark a point, you don't want it too tight to slide past the primary mirror so add 3mm to the length.

2. Measure the circumference of the inside of the corrector housing at the end of the front of the OTA tube using a strip of paper or cardboard and mark a point, you don't want it too tight to slide past the opening so remove 3mm from the length.

3. Measure the distance from the primary mirror edge and the corrector housing.

4. Due to the primary mirror being larger than the corrector housing you will need to mark the plastic sheet from a central line to form a slightly conical shape, then add 100mm to the front to allow water to flow out of the OTA and add 50mm to the back to allow the wash bay to slide past the primary mirror to the rear cell. Also add a 10mm tab down one side to allow the sheet to be attached together with gaffa tape.

5. Carefully slide the internal wash bay through the corrector assembly and past the primary mirror

6. Do a similar procedure to make a tube to cover the baffle tube and attach to baffle using gaffa tape.

7. Place the OTA in a slightly downward position with a bucket on the ground at the front and carefully use a large syringe to wash the mirror with cleaning solution or mild pure soapy water then with another large syringe carefully wash the mirror with pure water and allow to completely dry then carefully remove the internal wash bay and replace the corrector to its original position.

[iborg (Philip)]

Hi


I wish I had thought of the wash bay idea!


Philip

[Sunfish (Ray)]

Watch a professional clean:

https://youtu.be/e66yIuD3cMk
Watch "How to strip and clean the optics of a SCT (Schmidt-Cassegrain Telescope)" on YouTube

Maybe dishwashing liquid was a bit too much and left smears.


Willy also has a great video on how coating of the mirrors is done.