I suspect I have a telescope disaster!

[Peter Drew]

The rotational position of the secondary is very important in this design and difficult to rectify if altered due to dismantling, the main reason I would prefer to remove the entire cell. After marking carefully the location of this item.    😀 

[Gina]

5 minutes ago, Tomatobro said:

Try taking advantage of the different expansion rates of the steel screws and the aluminium holder. Hold a soldering iron on the head of the screw to warm it up then try to loosen the screw.

Yes, I was wondering that - shouldn't heat the glass much.

[Rusted]

It's not enough to try and keep a closed space dry. The metal parts are subject to thermal inertia.
Which means masses of condensation every time the temperature rises quickly and the metal lags behind.
The same holds true with thick glass in an OTA of course.
My refractor objectives get misted up inside after a cold night when I open up early to the warm sunshine.
Even though I cover them with protective saucepan lids overnight they don't offer any "insulation."

[wimvb]

Interesting.

23 minutes ago, Rusted said:

Even though I cover them with protective saucepan lids overnight they don't offer any "insulation." 

I would love to see a picture of this solution.

I bought a car seat heater pad similar to those in the link, for my mount last year, but I may just turn it into a scope blanket.

https://www.bazaargadgets.com/se/2-sittplatser-universal-kolfiber-uppvarmd-satesvarmare-12v-pads-2-dial.html

(not in English, but I think you get the idea)

[Rusted]

1 hour ago, wimvb said:

Interesting.

I would love to see a picture of this solution.

I bought a car seat heater pad similar to those in the link, for my mount last year, but I may just turn it into a scope blanket.

https://www.bazaargadgets.com/se/2-sittplatser-universal-kolfiber-uppvarmd-satesvarmare-12v-pads-2-dial.html

(not in English, but I think you get the idea)

Thanks for the suggestion.

A hair drier might be cheaper, save electricity bills and need only used when necessary.

 

[JamesF]

The issue of seized screw removal remind me that I need some small diameter left-handed drill bits.  I must make a note to have a search for some.

James

[DaveS]

That's a real sickener Gina, hopefully the damage looks worse than it is.

Given my natural caution in such matters I'd echo what others have said and remove the whole corrector assembly after marking its position. dismantling further might end up in losing the alignment.

[Stu]

1 hour ago, Rusted said:

Thanks for the suggestion.

A hair drier might be cheaper, save electricity bills and need only used when necessary.

Isn't the point to be able to apply low level heat over a long period to prevent the formation of dew? I keep dew strips wrapped around my mount and scope on low power when left under cover for any length and it successfully keeps the dew off. A sensible precaution for not much cost.

[Alien 13]

How are all your other scopes Gina? I fear the same environment would have attacked them too.

Alan

[Gina]

Most of my others are indoors and fine.  There is one other in the warm room though I must check.

[DaveS]

Where are your cameras and filter wheels kept? Those Astrodons are worth more than the MN190.

[Gina]

All indoors.  Safe and sound.

Just been out to the observatory and the other scope, a refractor, is fine.  Also, managed to bring the MN190 indoors to work on and now getting my breath - that scope is heavy.

[MarsG76]

Aaarghhh that's what nightmares are made of!!! That's terrible.. I suspect that fungus started to grow due to moisture getting in side from being stored in a damp observatory. Try keeping it open in sunlight or a UV light source, that kills the spores and might improve it without needing to open up... Otherwise  i presume that you can remove then front corrector/meniscus but I recommend to mark its orientation much like with a SCT and clean it with isopropyl alcohol and distilled water.

Good luck.

Edited July 2, 2019 by MarsG76

[ngwillym]

18 hours ago, StarDodger said:

I Have a full list of them if you need..

Can you post the list here please - was also thinking of the same thing

Thanks in advance

Neil

[JamesF]

Just now, ngwillym said:

Can you post the list here please - was also thinking of the same thing

Thanks in advance

Neil

Could well be a useful list for some people, so probably a new thread in the mounts area would be better than posting in this one.

James

[Gina]

Have taken the focuser unit off the scope and the hole is big enough to get my hand in and I can reach all or the inside of the lens.  I have IPA that I could try on the surface.  I have felt the bad patches and they are rough.

[MarsG76]

5 minutes ago, Gina said:

Have taken the focuser unit off the scope and the hole is big enough to get my hand in and I can reach all or the inside of the lens.  I have IPA that I could try on the surface.  I have felt the bad patches and they are rough.

Yeah, sounds like dead fungal growth.... careful not to scratch the glass... perhaps moisten it first....

[Gina]

Tried a slightly moist tissue and the patches can be removed.  PHEW!!

[DaveS]

21 minutes ago, Gina said:

All indoors.  Safe and sound.

Just been out to the observatory and the other scope, a refractor, is fine.  Also, managed to bring the MN190 indoors to work on and now getting my breath - that scope is heavy.

Good that the other kit is safe and sound, was a bit worried

7 minutes ago, Gina said:

Have taken the focuser unit off the scope and the hole is big enough to get my hand in and I can reach all or the inside of the lens.  I have IPA that I could try on the surface.  I have felt the bad patches and they are rough.

That doesn't sound good. Sounds to me like a growth on the surface, rather than just a discolouration. I'd have the whole front off so you can have a good look at it under angled lighting,

[DaveS]

2 minutes ago, Gina said:

Tried a slightly moist tissue and the patches can be removed.  PHEW!!

Sounding more hopeful. Good luck.

[geoflewis]

Just now, Gina said:

Tried a slightly moist tissue and the patches can be removed.  PHEW!!

I've been following this thread with interest and wishes for a positive outcome Gina. It sounds like you are making good progress, so I hope that continues 🤞. Geof

[Gina]

5 minutes ago, DaveS said:

That doesn't sound good. Sounds to me like a growth on the surface, rather than just a discolouration. I'd have the whole front off so you can have a good look at it under angled lighting,

The muck comes off easily.  I was going to take the whole cell off but still can't budge the screws.  I think cleaning by access though the focuser hole will be sufficient though.

[Nigella Bryant]

I've a 12inch newtononian and sometimes even the main mirror fogs up so I've installed a fan which keeps everything OK. Glad you're getting thing's sorted and seems able to be sorted. 

[Gina]

Well, it's not quite what I would call perfect, with a slight smearing but it's tons better than before.

Edited July 2, 2019 by Gina

[Gina]

Got it a bit better but I think it needs a lint free cotton cloth and distilled water.  Or maybe Baader Wonder Fluid and cloth.