Marks on the inside of my corrector glass

[Belcher]

Hi. I have noticed a few marks on the inside of my corrector glass on the end of my LX200. I guess it could be early stages of mould. Do I need to worry about this? Is this a DIY remove and clean job, or does it need to go to telescope hospital for surgery?

I also have 2 noticeable bits of something on the primary mirror near the outer edge. They look about the size of a couple of fleas. Leave them be?

Thanks.

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[E621Keith]

If it is fungus, I'd treat it immediately. However, I've not strip a SCT so I will let someone else make the suggestion as to whether you should DIY or send it off.

In the future, I'd keep the scope in a dry box.

[Plantins]

Removal of the corrector retaining ring then the corrector plate on a SCT is an easy process.

On your LX200... Position the OTA so it's slightly pointing upwards so that the corrector plate can't fall forwards once the ring is removed. Once the retaining ring is removed (normally about eight screws), and usually on Meade SCT's you can see the corrector plate and scope are marked with a small line of tipex. This is done so that once the corrector plate is removed it can then go back and aligned in the same position that it was removed. If it isn't marked then mark it yourself so you know the correct position. It doesn't matter marking the corrector on the edge as it's hidden when the retaining ring is re-fitted.

Once removed I would delicatley try both corrector plate and primary mirror with a soft lens pen to try remove the deposits. If stubborn I would tend to leave the primary mirror as it won't affect your views. Only attempt to clean the primary if you think it's going to start affecting the mirror coatings. If the corrector plate is stubborn just clean the affected area with diluted IPA or Baader Wonder Fluid and pure cotton wool pads. Once the solution has been applied wipe off with a clean pad so it doesn't leave a residue. Then replace the corrector plate & ring.

Sometimes the corrector plate can stick to the housing, just be careful when trying to remove it.

Hope this helps.

[E621Keith]

I just want to add, unlike dust and other dirt, fungus can eat into the coating. Once this happens it cannot be reversed, and the resale value of that OTA will be affected.

I found Baader wonder fluid much more effective in removing fungus than Eclipse (pure IPA).

[orion61]

If you strain blue Windex through a coffee filter and use multiple white kleenex in radial strokes, (dont use circular motion) it will clean well. Useing clean cotton gloves helps keeping finger prints off the glass.

[Belcher]

Thanks chaps. I have ordered some Baadar fluid and the cloth that you can also buy with it. I'll give it a "careful" go

[Belcher]

Once again, thanks people. I have just carefully removed and cleaned the corrector plate and also blew off the bits of crud of the primary. I don't think it was fungus, it just looked like a bit of grease or something. It's all come up gleaming. The secondary mirror was a bit dusty so I just carefully dusted over it with a lens brush.

Have also received my DSi II (thanks to ScubaMike). Trouble is, the weather is rubbish and all I can see is clouds. So a clean scope, a new camera, and nowhere to look