Stuart M

I feel rather embarassed to tell this story but I guess we all make mistakes
and if it stops anyone else from making the same one then it will be worth
it.

<Deep breath>

I am the owner of a 9.25 inch SCT. A rather nice and expensive (for me)
piece of equipment.

I haven't been using it much in the last couple of years, since moving into
a flat, so it's been packed away. I also used to own a boat, and when I
bought it, there was a sealed tub of something called "Moisture Trap" in the
bilge. "Must be silica gel" thinks I. "Great, I'll use this for keeping my
telescope nice and dry in storage". So I put some in a couple of film
cannisters (with a few pinholes in) and put one in my eyepiece case and one
in my telescope box. The telscope was also wrapped in a dustbin bag for safe
measure and the bag was sealed at the top with duct tape. There were no
holes in this bag.

A few months later, I opened my eyepiece case and found that there was fluid
inside, all soaked down through the foam. The film cannister just had a
gloopy mess inside. It had attracted enough water to dissolve itself and
then some! Luckily, the way the case was placed, this mess hadn't come into
contact with any eyepieces so I took them all out, removed the foam from the
case and put it in the washing machine.
Now, onto the scope itself. I opened the box, removed the scope, opened the
black bag and found approx half a pint of water in the bottom (this is no
exageration). My scope was having a bath!
Anyhoo, I took out the scope and found that water had got inside so I
removed the corrector plate (quite a task in itself), wiped it out and dried
it and was happy that I had got it clean. I put it away.

After washing and drying out the foam, I put it back in the case and closed
the case. I thought it better not to put my eyepieces in just in case. I
left it on the spare bed. A couple of days later, there was a large wet
patch on the bed! This "Moisture Trap" is incredible stuff. I think it was
possibly made by Satan. I just cant get rid of it. I decided it was best to
throw away the case.

Today, I took out the scope again and found that the screws holding my
corrector plate in have all corroded. One has broken off in its hole and I
cant get the broken end out. I tried drilling it out but only succeeded in
drilling through to the side of it!
Their are also a few drops of water inside the scope again......

I have taken the ring off the end of the scope (the bit that the corrector
screws into) and have washed it thoroughly. I guess my next step is to get
someone to either get this screw out or drill and tap a new hole next to it.

I wonder now if I will ever get this scope aligned and working properly
again. I have marked everthing up so it should be a simple matter to rebuild
it. If not, I'm sure someone will be happy to charge me a fortune to do it.

One more thing. Someone on here was asking about cheap places for silicon
gel about a year ago. I nearly offered you some of this!

Stuart

Jo

In news:33dj33F3u31r8U1@individual.net,
Stuart M <dfdgh@fghf.cvgd> typed:
>
>
> One more thing. Someone on here was asking about cheap places for
> silicon gel about a year ago. I nearly offered you some of this!
>
That was me.

From your description it was almost certainly sodium hydroxide...caustic
soda. This is a deliquescent solid that will keep on absorbing water, then
it will dissolve in its own juices, then the concentrated corrosive solution
will continue to absorb water and increase in volume. It also dissolves skin
quite effectively and can be used to remove the flesh from bones to make
cool skeletons. In the home it can be used to unblock drains.

It is a strong alkali and so you might be able to neutralise the remains of
your telescope and prevent further damage using a dilute acid such as
vinegar, lemon juice or Cola followed by lots of water to neutralise the
stuff before attempting a proper cleanup.

Good luck.

Jo

Martin Brown

Stuart M wrote:

> I feel rather embarassed to tell this story but I guess we all make mistakes
> and if it stops anyone else from making the same one then it will be worth
> it.

All is not lost. You probably used something like anhydrous calcium
chloride with a few gungy organics in to prevent it clagging into big
lumps and keep it as granules. This sort of mix is sold as a generic
cheap and relatively harmless dehumidifier.
>
> <Deep breath>
>
> I am the owner of a 9.25 inch SCT. A rather nice and expensive (for me)
> piece of equipment.
>
> I haven't been using it much in the last couple of years, since moving into
> a flat, so it's been packed away. I also used to own a boat, and when I
> bought it, there was a sealed tub of something called "Moisture Trap" in the
> bilge. "Must be silica gel" thinks I.

Never assume anything. Always test it first. Silica gel stays solid. And
at least until the thought police got onto it was slightly pink when
damp and a nice shade of blue when anhydrous (cobalt doped - now banned
due to miniscule carcinogenic risk).

> A few months later, I opened my eyepiece case and found that there was fluid
> inside, all soaked down through the foam. The film cannister just had a
> gloopy mess inside. It had attracted enough water to dissolve itself and
> then some! Luckily, the way the case was placed, this mess hadn't come into
> contact with any eyepieces so I took them all out, removed the foam from the
> case and put it in the washing machine.

So far so good.

> Now, onto the scope itself. I opened the box, removed the scope, opened the
> black bag and found approx half a pint of water in the bottom (this is no
> exageration). My scope was having a bath!
> Anyhoo, I took out the scope and found that water had got inside so I
> removed the corrector plate (quite a task in itself), wiped it out and dried
> it and was happy that I had got it clean. I put it away.

You will need to wash it extensively. And if it is open cell foam (or
aged closed cell foam with lots of broken walls) you may never get rid
of it entirely.

> After washing and drying out the foam, I put it back in the case and closed
> the case. I thought it better not to put my eyepieces in just in case. I
> left it on the spare bed. A couple of days later, there was a large wet
> patch on the bed! This "Moisture Trap" is incredible stuff. I think it was
> possibly made by Satan. I just cant get rid of it. I decided it was best to
> throw away the case.

It should wash out. Dilute sodium bicarbonate should work as an
antidote. But be sure to wash it off all metal or optical surfaces
afterwards. You will end up with some chalk and table salt.
>
> Today, I took out the scope again and found that the screws holding my
> corrector plate in have all corroded. One has broken off in its hole and I
> cant get the broken end out. I tried drilling it out but only succeeded in
> drilling through to the side of it!
> Their are also a few drops of water inside the scope again......

The chloride component is corrosive so you need to get all contaminated
parts clean asap. Careful washing with clean water will be needed and
plenty of time in a nice dry atmosphere to get all the water out of the
works. Tapwater OK for first couple of goes. Final wash with
distilled/deionised water.

Screws can be drilled out but only as a last resort and by someone with
decent machine tools.

> I have taken the ring off the end of the scope (the bit that the corrector
> screws into) and have washed it thoroughly. I guess my next step is to get
> someone to either get this screw out or drill and tap a new hole next to it.
>
> I wonder now if I will ever get this scope aligned and working properly
> again. I have marked everthing up so it should be a simple matter to rebuild
> it. If not, I'm sure someone will be happy to charge me a fortune to do it.

It can probably be done. Try looking up your local model engineering
society to try and find someone with the right gear to redrill and tap
the front corrector plate.

Regards,
Martin Brown

Jonathan Silverlight

In message <33dta3F40lm3hU1@individual.net>, Jo
<j0anna.drake.removethis@ntlworld.com> writes
>In news:33dj33F3u31r8U1@individual.net,
>Stuart M <dfdgh@fghf.cvgd> typed:
>>
>>
>> One more thing. Someone on here was asking about cheap places for
>> silicon gel about a year ago. I nearly offered you some of this!
>>
>That was me.
>
>From your description it was almost certainly sodium hydroxide...caustic
>soda.

Just to reassure Stuart, I've never heard of sodium hydroxide being used
as a drying agent - there are many safer materials. Corrections
welcomed, of course.
My first guess when I read his account was that it was anhydrous sodium
sulfate, but calcium chloride makes more sense and will dissolve into a
puddle in its own juice as soon as your back is turned!
BTW, silica gel, at least the blue self-indicating type, is under a
cloud at the moment because the indicator (cobalt chloride) is a
suspected carcinogen.
Nice to see my day job is useful!

chris.b@mail.dk

It never rains but it pours:

There are such things as screw extractors (usually referred to as stud
extractors). Used by mechanics and engineers to remove rusted-in
screws. These extractors are slow tapered left handed screws of
hardened steel. One bores a hole into the screw that it is desired to
remove and then the stud extractor inserted and rotated backwards.
Anticlockwise. The left hand screw thread of the extractor bites into
the hole in the corroded screw and (in theory) will unscrew the poorly
screw. Cheap, probably Chinese made versions of stud extractors exist.
Even seen in supermarkets! I would hesitate to use one of these.

One has only one chance before the corroded screw is virtually
destroyed while still clinging for its life to its threaded hole.
Unfortunately the common mechanics/engineeriing practice of heating
with a gas torch cannot be tried. Easing or penetrating oil might help
the problem and might not. Unfortunately your clumsy attempt at
drilling out the screw probably leaves you in the hands of a
professional. With luck it might be a 2 minute job. Or it might not.

The question is which professional to aproach. Given the circumstances
I would probably suggest asking a skilled antique clock repairer if
they can manage the job. They are used to removing screws that have
seen the blunt screwdrivers, penknives and assorted other useless tools
in the unsteady hands of botchers and clock owners over several
centuries. The problem is finding a skilled and well equipped
clockmaker. You might approach the BHI (British Horological Institute)
for a local member. They may even be listed on their website.

For future reference I would suggest that holes to be drilled in
corroded screws should start dead centre with a maximum 1.5-2mm drill
then opened out in 1mm steps. A perfectly central, very sharp, center
punch tapped very lightly will aid the start of the first hole
position. It should be checked with a magnifying glass and "moved" back
to a central position again if necessary. And well before a high speed
drill is brought anywhere near the job.

What a shame the manufacturers of certain popular American telescopes
haven't yet heard of stainless steel screws. A few pence (or cents)
difference would probably have made your task of removal so much
easier.

Chris.B

Alan

"Jonathan Silverlight" <jsilverlight@spam.merseia.fsnet.co.uk.invalid> wrote
in message news:ezvDdsGUbc0BFw$c@merseia.fsnet.co.uk...
> In message <33dta3F40lm3hU1@individual.net>, Jo
> <j0anna.drake.removethis@ntlworld.com> writes
>>In news:33dj33F3u31r8U1@individual.net,
>>Stuart M <dfdgh@fghf.cvgd> typed:
>>>
>>>
>>> One more thing. Someone on here was asking about cheap places for
>>> silicon gel about a year ago. I nearly offered you some of this!
>>>
>>That was me.
>>
>>From your description it was almost certainly sodium hydroxide...caustic
>>soda.
>
> Just to reassure Stuart, I've never heard of sodium hydroxide being used
> as a drying agent - there are many safer materials. Corrections welcomed,
> of course.
> My first guess when I read his account was that it was anhydrous sodium
> sulfate, but calcium chloride makes more sense and will dissolve into a
> puddle in its own juice as soon as your back is turned!
> BTW, silica gel, at least the blue self-indicating type, is under a cloud
> at the moment because the indicator (cobalt chloride) is a suspected
> carcinogen.
> Nice to see my day job is useful!

Crumbs ..... I remember my parents had a novelty ceramic ornament that was
covered in cobalt chloride (think it was a dog which supposedly showed when
it was going to rain........) and I'm sure my childhood chemistry set (about
30 years ago) had me making such things by dissolving the stuff in water and
soaking filter paper in it and letting it dry.

Jonathan Silverlight

In message <t9kAd.3529$sY2.512@newsfe4-gui.ntli.net>, Alan
<nospam@spamless.com> writes
>
>"Jonathan Silverlight" <jsilverlight@spam.merseia.fsnet.co.uk.invalid> wrote
>in message news:ezvDdsGUbc0BFw$c@merseia.fsnet.co.uk...
>> In message <33dta3F40lm3hU1@individual.net>, Jo
>> <j0anna.drake.removethis@ntlworld.com> writes
>>>In news:33dj33F3u31r8U1@individual.net,
>>>Stuart M <dfdgh@fghf.cvgd> typed:
>>>>
>>>>
>>>> One more thing. Someone on here was asking about cheap places for
>>>> silicon gel about a year ago. I nearly offered you some of this!
>>>>
>>>That was me.
>>>
>>>From your description it was almost certainly sodium hydroxide...caustic
>>>soda.
>>
>> Just to reassure Stuart, I've never heard of sodium hydroxide being used
>> as a drying agent - there are many safer materials. Corrections welcomed,
>> of course.
>> My first guess when I read his account was that it was anhydrous sodium
>> sulfate, but calcium chloride makes more sense and will dissolve into a
>> puddle in its own juice as soon as your back is turned!
>> BTW, silica gel, at least the blue self-indicating type, is under a cloud
>> at the moment because the indicator (cobalt chloride) is a suspected
>> carcinogen.
>> Nice to see my day job is useful!
>
>Crumbs ..... I remember my parents had a novelty ceramic ornament that was
>covered in cobalt chloride (think it was a dog which supposedly showed when
>it was going to rain........) and I'm sure my childhood chemistry set (about
>30 years ago) had me making such things by dissolving the stuff in water and
>soaking filter paper in it and letting it dry.
>
>

That takes me back! I'm fairly sure my parents had the same sort of
thing. Probably worth a bit now, if it's not too hideous. But don't
worry about it. The cancer bogeyman is just that, in most cases. I would
happily use self-indicating silica gel if I needed it, being careful not
to get any dust on me - or breathe it.
The cancer bogeyman is just that, in most cases.

Stuart M

Just like to thank you all for your help. I'm amazed how many chemists are
in this group!

I have spent most of the evening washing, soaking and rinsing various parts
of the scope. I have now given it (and a cut on my hand, ouch) a lemon juice
bath. Its now rinsing again.
I tried putting the screws back and they are very hard to screw in. I think
the holes are a bit corroded. I think I will need to send it away for
re-tapping of the screwholes and to remove the broken screw.
I have taken the entire tube off now. I want to make sure I clean it
properly this time.
I only hope that none of this stuff has got behind the mirror and into the
focuser. I should probably have a look but am not too keen on removing that
lot. I'll have to do some research and see how difficult this would be.
I have been thinking about who to send this off to. I do remember that a
member of this group does engineering work so I might ask for a quote from
him. If anyone has any recommendations I would be grateful.

Thanks again for all you help.

Stuart

..
"Stuart M" <dfdgh@fghf.cvgd> wrote in message
news:33dj33F3u31r8U1@individual.net...
>I feel rather embarassed to tell this story but I guess we all make
>mistakes and if it stops anyone else from making the same one then it will
>be worth it.
>
> <Deep breath>
>
> I am the owner of a 9.25 inch SCT. A rather nice and expensive (for me)
> piece of equipment.
>
> I haven't been using it much in the last couple of years, since moving
> into a flat, so it's been packed away. I also used to own a boat, and when
> I bought it, there was a sealed tub of something called "Moisture Trap" in
> the bilge. "Must be silica gel" thinks I. "Great, I'll use this for
> keeping my telescope nice and dry in storage". So I put some in a couple
> of film cannisters (with a few pinholes in) and put one in my eyepiece
> case and one in my telescope box. The telscope was also wrapped in a
> dustbin bag for safe measure and the bag was sealed at the top with duct
> tape. There were no holes in this bag.
>
> A few months later, I opened my eyepiece case and found that there was
> fluid inside, all soaked down through the foam. The film cannister just
> had a gloopy mess inside. It had attracted enough water to dissolve itself
> and then some! Luckily, the way the case was placed, this mess hadn't come
> into contact with any eyepieces so I took them all out, removed the foam
> from the case and put it in the washing machine.
> Now, onto the scope itself. I opened the box, removed the scope, opened
> the black bag and found approx half a pint of water in the bottom (this is
> no exageration). My scope was having a bath!
> Anyhoo, I took out the scope and found that water had got inside so I
> removed the corrector plate (quite a task in itself), wiped it out and
> dried it and was happy that I had got it clean. I put it away.
>
> After washing and drying out the foam, I put it back in the case and
> closed the case. I thought it better not to put my eyepieces in just in
> case. I left it on the spare bed. A couple of days later, there was a
> large wet patch on the bed! This "Moisture Trap" is incredible stuff. I
> think it was possibly made by Satan. I just cant get rid of it. I decided
> it was best to throw away the case.
>
> Today, I took out the scope again and found that the screws holding my
> corrector plate in have all corroded. One has broken off in its hole and I
> cant get the broken end out. I tried drilling it out but only succeeded in
> drilling through to the side of it!
> Their are also a few drops of water inside the scope again......
>
> I have taken the ring off the end of the scope (the bit that the corrector
> screws into) and have washed it thoroughly. I guess my next step is to get
> someone to either get this screw out or drill and tap a new hole next to
> it.
>
> I wonder now if I will ever get this scope aligned and working properly
> again. I have marked everthing up so it should be a simple matter to
> rebuild it. If not, I'm sure someone will be happy to charge me a fortune
> to do it.
>
> One more thing. Someone on here was asking about cheap places for silicon
> gel about a year ago. I nearly offered you some of this!
>
> Stuart
>
>

ChrisH

On Tue, 28 Dec 2004 23:14:50 -0000, "Stuart M" <dfdgh@fghf.cvgd>
wrote:

>Just like to thank you all for your help. I'm amazed how many chemists are
>in this group!
>
>I have spent most of the evening washing, soaking and rinsing various parts
>of the scope. I have now given it (and a cut on my hand, ouch) a lemon juice
>bath. Its now rinsing again.
>I tried putting the screws back and they are very hard to screw in. I think
>the holes are a bit corroded. I think I will need to send it away for
>re-tapping of the screwholes and to remove the broken screw.
>I have taken the entire tube off now. I want to make sure I clean it
>properly this time.
>I only hope that none of this stuff has got behind the mirror and into the
>focuser. I should probably have a look but am not too keen on removing that
>lot. I'll have to do some research and see how difficult this would be.
>I have been thinking about who to send this off to. I do remember that a
>member of this group does engineering work so I might ask for a quote from
>him. If anyone has any recommendations I would be grateful.
>
>Thanks again for all you help.
>
>Stuart
>

I can let you have some stainless screws as replacements for the
price of postage (check - should be #6x32 american thread, or about
5/32 if you meaure them). The length I'm not sure of for Celestron but
these are OK for Meade. They are cap-head rather than dome-headed, but
they don't rust :-))
Be careful not to over-tighten them, not much more than finger tight
is about right. The idea is to hold the corrector in place without
distorting it. I hope you marked the orientation of the secondary and
corrector with respect to the tube when you removed it.

ChrisH

Martin Frey

"Alan" <nospam@spamless.com> wrote:

>Crumbs ..... I remember my parents had a novelty ceramic ornament that was
>covered in cobalt chloride (think it was a dog which supposedly showed when
>it was going to rain........) and I'm sure my childhood chemistry set (about
>30 years ago) had me making such things by dissolving the stuff in water and
>soaking filter paper in it and letting it dry.

Alan - don't worry. By modern safety standards everybody over 50 has
been dead for at least 10 years.

Cheers

Martin

--
Martin Frey
http://www.hadastro.org.uk
N 51 02 E 0 47

Stuart M

"ChrisH" <chrish@noeasynetspam.co.uk.inavlid> wrote in message
news:e5r3t0h9uhpvn5ebhdiveuj1p5ftcg1vui@4ax.com...
> I can let you have some stainless screws as replacements for the
> price of postage (check - should be #6x32 american thread, or about
> 5/32 if you meaure them). The length I'm not sure of for Celestron but
> these are OK for Meade. They are cap-head rather than dome-headed, but
> they don't rust :-))
> Be careful not to over-tighten them, not much more than finger tight
> is about right. The idea is to hold the corrector in place without
> distorting it. I hope you marked the orientation of the secondary and
> corrector with respect to the tube when you removed it.

Hello Chris,

Thats very generous of you, thanks.

Im not sure what those numbers relate to exactly but the screws are about
12mm long, 2mm wide and the thread is approx 0.5mm across. I could mail you
one of them if you like.
I use a precision driver so they dont get too tight. They were tight this
time but only because they were corroded into their holes.
I did mark the orientation but the corrector was so hard to remove, I think
the secondary holder may have rotated a bit. What a bloody nightmare this
is. Oh well, it has been nice to get inside it at last! I always wanted to
really.

I've sent you an email.

Regards,

Stuart.

Stuart M

"Stuart M" <dfdgh@fghf.cvgd> wrote in message
news:33ef32F3voalpU1@individual.net...
>
> "ChrisH" <chrish@noeasynetspam.co.uk.inavlid> wrote in message
> news:e5r3t0h9uhpvn5ebhdiveuj1p5ftcg1vui@4ax.com...
>> I can let you have some stainless screws as replacements for the
>> price of postage (check - should be #6x32 american thread, or about
>> 5/32 if you meaure them). The length I'm not sure of for Celestron but
>> these are OK for Meade. They are cap-head rather than dome-headed, but
>> they don't rust :-))
>> Be careful not to over-tighten them, not much more than finger tight
>> is about right. The idea is to hold the corrector in place without
>> distorting it. I hope you marked the orientation of the secondary and
>> corrector with respect to the tube when you removed it.
>
> Hello Chris,
>
> Thats very generous of you, thanks.
>
> Im not sure what those numbers relate to exactly but the screws are about
> 12mm long, 2mm wide and the thread is approx 0.5mm across. I could mail
> you one of them if you like.
> I use a precision driver so they dont get too tight. They were tight this
> time but only because they were corroded into their holes.

Ive just read through this thread again and Im not sure if Ive been
misunderstood. The screws arent rusted, they were just stuck in their holes.
I think the metal of the corrector mount has reacted with this stuff and
corroded inside the screw hole. (Im just guessing really). Did you think the
screws had rusted?

Stephen Tonkin

Jonathan Silverlight <jsilverlight@spam.merseia.fsnet.co.uk.invalid>
wrote:
>(cobalt chloride) is a suspected carcinogen.

Anyone else remember having this stuff in the "Chemistry Set"? Didn't
taste as bad as the copper sulphate <g>. (Apparently all stuff in
Merkinese chemistry sets now has to be food grade!)

Best,
Stephen

Remove footfrommouth to reply

--
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +
+ Stephen Tonkin | ATM Resources; Astro-Tutorials; Astro Books +
+ (N51.162 E0.995) | <http://astunit.com> +
+ + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +

chris.b@mail.dk

Alan - don't worry. By modern safety standards everybody over 50 has
been dead for at least 10 years.

Martin


Confirmation at last! I suppose I had guessed as much when all my hair
fell out and I couldn't look at myself in the mirror..
Can I start going "Woooo woooo wooo" and clanking invisible chains at
my neighbours now?
*
Chris.B Late, as always.

Dave Fawthrop

On Tue, 28 Dec 2004 20:16:52 -0000, "Jo"
<j0anna.drake.removethis@ntlworld.com> wrote:

| In news:33dj33F3u31r8U1@individual.net,
| Stuart M <dfdgh@fghf.cvgd> typed:
| >
| >
| > One more thing. Someone on here was asking about cheap places for
| > silicon gel about a year ago. I nearly offered you some of this!
| >
| That was me.
|
| From your description it was almost certainly sodium hydroxide...caustic
| soda. This is a deliquescent solid that will keep on absorbing water, then
| it will dissolve in its own juices, then the concentrated corrosive solution
| will continue to absorb water and increase in volume. It also dissolves skin
| quite effectively and can be used to remove the flesh from bones to make
| cool skeletons. In the home it can be used to unblock drains.
|
| It is a strong alkali and so you might be able to neutralise the remains of
| your telescope and prevent further damage using a dilute acid such as
| vinegar, lemon juice or Cola followed by lots of water to neutralise the
| stuff before attempting a proper cleanup.

This will be difficult because the alkali followed by the mild acid will
get into any screw thread, tiny crack or crevice, and continue working
there. Strip the telescope as far as you are able, and happy that you can
get it back together again. Stripping lenses is *not* a good idea. Others
more experience will be able to advise what can be stripped and what can
not.

--
Dave Fawthrop <dave@hyphenologist.co.uk>
Subscribe to uk.net.news.announce. A low volume *civilised* newsgroup
with only the essential information about what is happening in the uk.*
newsgroups, Request For Discussions (RFDs) Call For Votes (CFVs) etc.

Jonathan Silverlight

In message <pb3WtNJfrl0BFwrL@astunit.com>, Stephen Tonkin
<news05footfrommouth@astunit.com> writes
>Jonathan Silverlight <jsilverlight@spam.merseia.fsnet.co.uk.invalid>
>wrote:
>>(cobalt chloride) is a suspected carcinogen.
>
>Anyone else remember having this stuff in the "Chemistry Set"? Didn't
>taste as bad as the copper sulphate <g>.

They put that "do not eat" label on the little bags of silica gel for a
reason, you know :-) But looking through the Merck Index, it's amazing
how many chemicals are described as "bitter tasting", or similar.

ChrisH

On Wed, 29 Dec 2004 01:42:36 -0000, "Stuart M" <dfdgh@fghf.cvgd>
wrote:

>
>Ive just read through this thread again and Im not sure if Ive been
>misunderstood. The screws arent rusted, they were just stuck in their holes.
>I think the metal of the corrector mount has reacted with this stuff and
>corroded inside the screw hole. (Im just guessing really). Did you think the
>screws had rusted?
>

Yes I thought the screws were rusted! The metal it screws into is
probably aluminium (I think, I've not pulled a 9.25 Celestron apart)
so I guess it could have experienced electrolytic corrosion. If there
has been too much loss of metal around the threads they can be tapped
out to the next size metric thread. If it has occured there you really
need to check behind the primary mirror for possible damage to the
focussing mechanism.

ChrisH

StuartM

..
"ChrisH" <chrish@noeasynetspam.co.uk.inavlid> wrote in message
news:le45t0tj68gvjpmp43p50dbdqlag9bgnkj@4ax.com...
> On Wed, 29 Dec 2004 01:42:36 -0000, "Stuart M" <dfdgh@fghf.cvgd>
> wrote:
>
>>
>>Ive just read through this thread again and Im not sure if Ive been
>>misunderstood. The screws arent rusted, they were just stuck in their
>>holes.
>>I think the metal of the corrector mount has reacted with this stuff and
>>corroded inside the screw hole. (Im just guessing really). Did you think
>>the
>>screws had rusted?
>>
>
> Yes I thought the screws were rusted! The metal it screws into is
> probably aluminium (I think, I've not pulled a 9.25 Celestron apart)
> so I guess it could have experienced electrolytic corrosion. If there
> has been too much loss of metal around the threads they can be tapped
> out to the next size metric thread. If it has occured there you really
> need to check behind the primary mirror for possible damage to the
> focussing mechanism.

Hi Chris,

I think I know what has happened now. On closer examination of the screws, I
noticed that there is some dark substance blocking the threads. I cleaned
this out with my fingernail and put the screw back in. It comes out gunked
up again but after repeating this a few times its clear and screws in ok. My
theory is that the calcium chloride has dissolved some of the paint and its
got into the threads (only another guess really).

I have taken the primary out and it looks undamaged behind but this morning
it had got damp again (I'd left the whole assembly under a black bag to keep
out dust) so it looks like the back cast needs a bath also.

Does anyone know what type of grease should be used on the tube as it will
need replacing after its bath?


Stuart

Grimble Gromble

"Jonathan Silverlight" <jsilverlight@spam.merseia.fsnet.co.uk.invalid> wrote
in message newszDOdXFkTc0BFw4S@merseia.fsnet.co.uk...
> In message <TbjAd.1209$uY6.670@newsfe3-win.ntli.net>, Grimble Gromble
> <grimble.gromble@virgin.net> writes
>>Although pretty nasty stuff in itself, I gather that phosphorous
>>pentachloride is sometimes used to remove water vapour (very effectively).
>>It has a negligible vapour pressure itself, locks up the water tight, and
>>doesn't leave a mess (when it's all reacted it just sits there). I gather
>>you can make a very good vacuum by introducing the stuff into to a vessel
>>whose air has been displaced with steam. Of course, don't take my word for
>>this. Any of this.
>
> I think you mean phosphorus pentoxide. Phosphorus pentachloride is
> described as "extremely hazardous"
> <http://www.cbwinfo.com/Chemical/Precursors/p36.html> and is a
> chlorinating agent in chemistry.
> Phosphorus pentoxide is hazardous and I wouldn't use it if anything else
> would do.

Thanks, Jonathan. You are quite right. Phosphorous pentoxide it is. Why
aren't we allowed to play with chemicals (let alone dangerous ones) anymore?
Heaven knows they put enough of them in the air we breath, the food we eat
and the water we drink.
Grim

Grimble Gromble

"Martin Frey" <martinfrey@snipclara.co.uk> wrote in message
news:mls3t05k95ala7d12bfmceascortbgvegm@4ax.com...
> "Alan" <nospam@spamless.com> wrote:
>
>>Crumbs ..... I remember my parents had a novelty ceramic ornament that was
>>covered in cobalt chloride (think it was a dog which supposedly showed
>>when
>>it was going to rain........) and I'm sure my childhood chemistry set
>>(about
>>30 years ago) had me making such things by dissolving the stuff in water
>>and
>>soaking filter paper in it and letting it dry.
>
> Alan - don't worry. By modern safety standards everybody over 50 has
> been dead for at least 10 years.

It's just one piece of bad news after another. It now appears I missed the
deadline (oops - no pun intended) by just one year.
Grim

Fleetie

"Stephen Tonkin" <news05footfrommouth@astunit.com> wrote
> Jonathan Silverlight <jsilverlight@spam.merseia.fsnet.co.uk.invalid> wrote:
>>(cobalt chloride) is a suspected carcinogen.
>
> Anyone else remember having this stuff in the "Chemistry Set"? Didn't taste as bad as the copper sulphate <g>. (Apparently all
> stuff in Merkinese chemistry sets now has to be food grade!)

That stuff was cool! Blue when dry and pink when damp. My mum also had
some kind of sonament with a circle of stuff that looked like felt,
that had clearly been impregnated with it. It was supposed to tell you
something about the weather, IIRC. I'd totally forgotten about that! I
wonder whether she still has it.


Martin
--
M.A.Poyser Tel.: 07967 110890
Manchester, U.K. http://www.fleetie.demon.co.uk

Jo

In news:8nt4t05ohlg32dhhcvd2r65mpsdoc7pkku@4ax.com,
Dave Fawthrop <hyphen@hyphenologist.co.uk> typed:
>> It is a strong alkali and so you might be able to neutralise the
>> remains of your telescope and prevent further damage using a dilute
>> acid such as vinegar, lemon juice or Cola followed by lots of water
>> to neutralise the stuff before attempting a proper cleanup.
>
> This will be difficult because the alkali followed by the mild acid
> will get into any screw thread, tiny crack or crevice, and continue
> working there. Strip the telescope as far as you are able, and
> happy that you can get it back together again. Stripping lenses is
> *not* a good idea. Others more experience will be able to advise
> what can be stripped and what can not.
>
Yes, I was suggesting neutralisation as a first step before a proper
cleanup. In the event, as others have suggested, it is more likely to be
calcium chloride The weak acids I suggested would serve to remove some of
the corrosion products prior to a thorough cleanup, including dismantling,
removal of screws and lots of water.

Jo

Stuart M

"Jo" <j0anna.drake.removethis@ntlworld.com> wrote in message
news:33fmnuF3rv292U1@individual.net...
> In news:8nt4t05ohlg32dhhcvd2r65mpsdoc7pkku@4ax.com,
> Dave Fawthrop <hyphen@hyphenologist.co.uk> typed:
>>> It is a strong alkali and so you might be able to neutralise the
>>> remains of your telescope and prevent further damage using a dilute
>>> acid such as vinegar, lemon juice or Cola followed by lots of water
>>> to neutralise the stuff before attempting a proper cleanup.
>>
>> This will be difficult because the alkali followed by the mild acid
>> will get into any screw thread, tiny crack or crevice, and continue
>> working there. Strip the telescope as far as you are able, and
>> happy that you can get it back together again. Stripping lenses is
>> *not* a good idea. Others more experience will be able to advise
>> what can be stripped and what can not.
>>
> Yes, I was suggesting neutralisation as a first step before a proper
> cleanup. In the event, as others have suggested, it is more likely to be
> calcium chloride The weak acids I suggested would serve to remove some of
> the corrosion products prior to a thorough cleanup, including dismantling,
> removal of screws and lots of water.
>

I have stripped it right down and its all in the bath for the third time. I
want this done properly this time.
You are right, it is calcium chloride.
Now I just need to get that screw removed.

Stuart M

<chris.b@mail.dk> wrote in message
news:1104267286.894449.96680@f14g2000cwb.googlegro ups.com...
> It never rains but it pours:
>
> There are such things as screw extractors (usually referred to as stud
> extractors). Used by mechanics and engineers to remove rusted-in
> screws. These extractors are slow tapered left handed screws of
> hardened steel. One bores a hole into the screw that it is desired to
> remove and then the stud extractor inserted and rotated backwards.
> Anticlockwise. The left hand screw thread of the extractor bites into
> the hole in the corroded screw and (in theory) will unscrew the poorly
> screw. Cheap, probably Chinese made versions of stud extractors exist.
> Even seen in supermarkets! I would hesitate to use one of these.
>
> One has only one chance before the corroded screw is virtually
> destroyed while still clinging for its life to its threaded hole.
> Unfortunately the common mechanics/engineeriing practice of heating
> with a gas torch cannot be tried. Easing or penetrating oil might help
> the problem and might not. Unfortunately your clumsy attempt at
> drilling out the screw probably leaves you in the hands of a
> professional. With luck it might be a 2 minute job. Or it might not.
>
> The question is which professional to aproach. Given the circumstances
> I would probably suggest asking a skilled antique clock repairer if
> they can manage the job. They are used to removing screws that have
> seen the blunt screwdrivers, penknives and assorted other useless tools
> in the unsteady hands of botchers and clock owners over several
> centuries. The problem is finding a skilled and well equipped
> clockmaker. You might approach the BHI (British Horological Institute)
> for a local member. They may even be listed on their website.
>
> For future reference I would suggest that holes to be drilled in
> corroded screws should start dead centre with a maximum 1.5-2mm drill
> then opened out in 1mm steps. A perfectly central, very sharp, center
> punch tapped very lightly will aid the start of the first hole
> position. It should be checked with a magnifying glass and "moved" back
> to a central position again if necessary. And well before a high speed
> drill is brought anywhere near the job.

Thank you Chris for that advice. I think I have used one of those extractors
before; I have a vague memory of them.

By the way, you missed out plyers as "useless tools" for getting out screws
(which is what I used!)

Regards,

Stuart

chris.b@mail.dk

Philistine! ;-)

Whatever works without further damage is okay. Until you reach a point
of no return and the damn screw is still sitting there, grinning back
at you while a customer is waiting expectantly and impatiently for
perfection at a pittance, on his priceless 17th century family
heirloom. :-)

Chris.B

Stuart M

<chris.b@mail.dk> wrote in message
news:1104339065.367806.242650@z14g2000cwz.googlegr oups.com...
> Philistine! ;-)
>
> Whatever works without further damage is okay. Until you reach a point
> of no return and the damn screw is still sitting there, grinning back
> at you while a customer is waiting expectantly and impatiently for
> perfection at a pittance, on his priceless 17th century family
> heirloom. :-)


Damn, I thought I was going mad when I saw that screw grin at me! It also
told me to burn things.....

Roger Smith

In message <33fkhjF3uog7fU1@individual.net>, StuartM <xxx@xxxxx.xxx>
wrote
>I have taken the primary out and it looks undamaged behind but this morning
>it had got damp again (I'd left the whole assembly under a black bag to keep
>out dust) so it looks like the back cast needs a bath also.

Pardon me for joining in here as I really only have an opinion not
expertise.

With polythene like substances any dampness in the air and object
wrapped inside is trapped there.

It sounds like you need to look at using something more porous than bin
liner to keep the scope in at the budget end really tight weave fabric
would keep out dust but allow the passage of moisture (unfortunately
both ways) a more expensive solution would be to use "Goretex" or
equivalent which allows the passage moisture only outwards.

--
Roger
52:54:41N
01:30:05W
Orion 127mm Maksutov.

Fleetie

>With polythene like substances any dampness in the air and object wrapped inside is trapped there.

Do you write instruction manuals?

Tim Auton

Roger Smith <roger@escore.demon.co.uk> wrote:
[wet scope]
>It sounds like you need to look at using something more porous than bin
>liner to keep the scope in at the budget end really tight weave fabric
>would keep out dust but allow the passage of moisture (unfortunately
>both ways) a more expensive solution would be to use "Goretex" or
>equivalent which allows the passage moisture only outwards.

Does Gore-Tex really do that? I thought it just allowed passage of
water vapour but not liquid water.


Tim
--
This is not my signature.

Roger Smith

In message <doGAd.133$Vc2.66@newsfe4-gui.ntli.net>, Fleetie
<fleetie@fleetie.demon.co.uk> wrote
>>With polythene like substances any dampness in the air and object
>>wrapped inside is trapped there.
>
>Do you write instruction manuals?
>
No, actually I don't normally right anything when this drunk.
--
Roger
52:54:41N
01:30:05W
Orion 127mm Maksutov.