OOPS! Flocked Paper Adhesive Meets Primary

I recently added flocked paper to the inside of my 8" Newt that has a
self adhesive backing. Pulling out my scope yesterday to get it setup
for a viewing session I discovered one of the strips of flocked paper
had come off from the inside of the tube and landed on my primary. I
had to remove the primary from the tube to get at it, and at that point
discovered that I came up on the loosing side of the 50/50 chance of it
landing fuzzy side down. I was able to gently remove it, but it was
without a doubt actually stuck to the mirror in a patch about 1 x 2
inches smack in the center of the 'working portion' of the mirror,
it may have been there weeks. Some small black specs where left behind
but they where small and I was not terribly concerned as the mirror
looked visually clear and undamaged. I setup for my observing night and
the scope appeared to perform ok, though from the get go I was battling
a constant fight with heavy dew so it was hard to do any really
thorough validation. After getting the scope back in the house the
primary was well fogged up and that's when I noticed a VERY visible
difference in the moisture pattern on the mirror in the area that the
flocking paper had landed on.

Questions/Opinions needed on the following:

+ Is the fact that the moisture pattern was different indicative of
coating damage even though the mirror when dry appears ok?

+ Is there a easy way to validate the coding that removes the other
scope and environment variables that is easy to do?

+ Do I clean it with the standard soaking and rinsing method just to
see if it makes an improvement (in 5+ years I have never cleaned this
mirror)?

+ If it does come down to recoating - What does that typically cost for
a basic f/5 8" mirror?



Thanks in advance!

~derek

On Tue, 27 Sep 2005 22:00:48 -0700, derek wrote:



Questions/Opinions needed on the following:

+ Is the fact that the moisture pattern was different indicative of
coating damage even though the mirror when dry appears ok?

Anything that remains on the mirror will affect the moisture pattern, as
it will change the time it takes for the affected portion to reach
dewpoint. Even dust will leave a pattern. No sweat. (no pun)

+ Is there a easy way to validate the coding that removes the other
scope and environment variables that is easy to do?

+ Do I clean it with the standard soaking and rinsing method just to see
if it makes an improvement (in 5+ years I have never cleaned this
mirror)?

You could try that, and if it fails, use straight ethanol (alcohol from
a pharmacy--not rubbing alcohol if you can avoid it). If that fails,
escalate. Acetone. Do it outside. Or you could use USP Ether if you can
lay your hands on some. No sparks or smoking. Could go boom.
I'm pretty certain that should get it clean.

+ If it does come down to recoating - What does that typically cost for
a basic f/5 8" mirror?

About $35, where I take mine (San Carlos, CA)

Thing to remember, is that it isn't really going to make a noticeable
difference from an observer's point of view if you have completely removed
the coating for a couple of square inches. Just don't be tempted to do
any rubbing on the mirror or you will find yourself back at the coater's
getting a new one. (which isn't a bad idea, anyway). Have you held a
flashlight behind your mirror at night and looked for holes in the coating?

Good luck and don't sweat the little stuff.

Uncle Bob

Uncle Bob wrote:
On Tue, 27 Sep 2005 22:00:48 -0700, derek wrote:
You could try that, and if it fails, use straight ethanol (alcohol from
a pharmacy--not rubbing alcohol if you can avoid it). If that fails,
escalate. Acetone. Do it outside. Or you could use USP Ether if you can
lay your hands on some. No sparks or smoking. Could go boom.
I'm pretty certain that should get it clean.

I would start with lacquer thinner to disolve the adhesive, although it
might take a couple of wettings to fully disolve the gunk; and then
rinse with acetone. I have not found the typical alcohols very useful
in attacking adhesives--however lacquer thinner is often the thinning
adgent for the "contact cements" and will deal with them in short
order.

And yes, do it outside; if you can find one of appropriate size, a
large bucket will hold the fumes and allow the lacquer thinner time to
do its job without getting evaporated away. Expect it to take 20
minutes or so.

You shold not even need to touch the optical surface to remove the gunk.

If you have some of the flocking material available, you could try out these
cleaning agents first on a piece of window glass. That will help you
determine which one would work on the adhesive. Won't show you what effect
they might have on your coatings...

Jim


wrote in message
ups.com...

Uncle Bob wrote:
On Tue, 27 Sep 2005 22:00:48 -0700, derek wrote:
You could try that, and if it fails, use straight ethanol (alcohol from
a pharmacy--not rubbing alcohol if you can avoid it). If that fails,
escalate. Acetone. Do it outside. Or you could use USP Ether if you can
lay your hands on some. No sparks or smoking. Could go boom.
I'm pretty certain that should get it clean.

I would start with lacquer thinner to disolve the adhesive, although it
might take a couple of wettings to fully disolve the gunk; and then
rinse with acetone. I have not found the typical alcohols very useful
in attacking adhesives--however lacquer thinner is often the thinning
adgent for the "contact cements" and will deal with them in short
order.

And yes, do it outside; if you can find one of appropriate size, a
large bucket will hold the fumes and allow the lacquer thinner time to
do its job without getting evaporated away. Expect it to take 20
minutes or so.

You shold not even need to touch the optical surface to remove the gunk.

The adhesive has cleaned the mirror of dewing sites so you were seeing the
difference between the general condition of the mirror vs the really clean
part of the mirror.
I've found that flocking paper reallly doesn't do that good of a job for
darkening the background of the FOV as well as making a good set of baffles
for the telescope. Use NEWT2.5 to find where the baffles should be placed
and how many you will need. I'll also note that baffles won't fall to the
primary and damage it.

--
Why do penguins walk so far to get to their nesting grounds?

I've found that flocking paper reallly doesn't do that good of a job for
darkening the background of the FOV as well as making a good set of
baffles
for the telescope. Use NEWT2.5 to find where the baffles should be placed
and how many you will need. I'll also note that baffles won't fall to the
primary and damage it.

How do baffles affect tube currents?

Dennis