Mirror upgrades

[Doink]

Greetings all....

I have an 8" Orion reflector that I am going to disassemble and flock. I
noticed Orion's mirrors are 87% reflective. Should I put new mirrors in
when I flock? I love the scope and don't mind spending some $$$ on it. Can
anyone recomment mirror source?

And, 1-100 with 100 being huge, how much difference would a quality 97%
reflectivity mirror make? Is this worth the cost and effort?

Regards,

Doink!

[Greg Campbell]

Doink wrote:


Howda!


First off, there is more to a coating's quality than reflectivity.
Variations in coating's thickness and/or smoothness can adversely affect
the scope's performance. The thicker the aluminum layer, the more
reflective the surface will be. Many coating houses offer standard
(~88%) silvering as well as a 'super' (or whatever they choose to call
it) finish that it good for ~95%. This thicker coating is also
somewhat more succeptable to the aforementioned surface irregularities....

The 7% reflectivity gain you will get with a 'super' would be barely
visible, and then only IF you happned to have two otherwise identical
scopes available for back-to-back comparison. In the real world,
atmospheric conditions and other variables vastly outweigh the slight
brightness increase a super-dooper mirror will fetch.

The mirror's shape is at least as important than the coating. Are you a
member of a club? If so ask for help (or google the simple proceedure)
in performing a 'star test' on your scope. With any luck, someone in
the club will also have a knife edge or focault tester laying about and
will be willing to do a more comprehensive surface test. If your mirror
has problems, there are several businesses that will re-figure it for
you. (Many of them will do a cheap/free figure test.)


If you decide to go ahead with either/both services, I can personally
reccomend Steve Swayze and Spectrum Coatings (I got their 'enhanced'
aluminizing.). My old 10" Blue-Tube Coulter was transformed by a
refigure and re-silvering. (Replacing the Flintstonian secondary 'beam'
with a real spider, and other tweaks didn't hurt either! My scope is
still butt-ugly, but it works VERY nicely - for a puny 10" )

http://www.europa.com/~swayze/
http://www.spectrum-coatings.com/


If the old surface is knackered, 80. If in near-new condition, 10~25,
depending on the surface quality of the OEM aluminum.


Unless your current coating is degrading, or the optics need help, I'd
save the $100+ for a new eyepiece or a mounting upgrade. Also, poor
seeing and light polution will degrade any scope. If you don't use it
at a good observing site, your $$$ will be largely wasted.

Even with clean air and darks skies, a 30$ cooling fan installation will
do far more for your viewing.... http://www.fpi-protostar.com/bgreer/

-Greg



Ouch

[Doink]

Thanks Greg. My thought was since I was going to flock the tube, I might as
well deal with the mirrors.

Doink

"Greg Campbell" <nospam@null.net> wrote in message
news:HCawc.17473$lL1.11692@fed1read03...
I
Can

[Reef1969]

If you love the scope I would leave it as is. The 97%? coating may not make
much of a difference. Not confirmed, but may may do more harm than good by
recoating the mirror if it does not need it.

Clear Skies
Richard

[Greg Campbell]

Doink wrote:


Yea, it would be a good time to evaluate the glass. Check mechanical
alignment of the spider, focuser, and mirror holder while you're at it.

There's nothing like good flocking! Back when I did the mirrors, I
spent my waiting time reworking the tube and mount. Since I'm terribly
cheap, and flocking paper is spendy, I decided to glue $2 worth of ~1/4"
pumice gravel to the tube guts. The resulting increased image contrast
was probably offset by the zillion or so visual cortex neurons that bit
the dust due to contact cement and spray paint solvent inhalation.
(Stick your head in a 12" tube and cut loose with a jumbo can of
ultra-flat-black spray paint... Forget limiting sales to minors, it's us
'adults' that will kill ourselves with the stuff!) =:q

-Greg

[Dennis Woos]

> I have an 8" Orion reflector that I am going to disassemble and flock. I
Can

If you "love the scope", then why do you think that you need a new
mirror(s)? Do you mean primary or secondary, or both? In either case, the
figure of the mirrors is much more important than the 87%-97% coating issue.

If you are talking about the primary, then I would forget about 97% vs. 87%.
From what I understand you most probably won't want to spend what a good 97%
coating costs, and even if you did the difference would not be significant -
do the math. On the other hand, if the primary mirror is no good then
getting another one might make sense. If you do a web search you will find
a number of firms selling top-quality 8" mirrors (e.g. Royce). Of course, I
would make sure that the mirror is in fact bad before buying another one.

If you are concerned about the secondary, then you could get a known
top-quality one for a reasonable amount (e.g. Protostar). Again though,
unless the secondary you have is bad I doubt you will see a difference. On
the other hand, a very good secondary is not that expensive, so if you want
to try one go for it.

Dennis

[Matthew D. Mills]

Doink,
Why not have your mirror recoated with Beral instead of buying a new mirror
or upgrade your secondary.

Be carefull with flocking your OTA. I prepared my dob tube per ProtoStar
directions and the paper fell off and stuck to my mirror and ruined the
coatings. I emailed the company and they never responded.
Clear skies,
Matt Mills

[Paul Lawler]

"Matthew D. Mills" <mills@charter.net> wrote in message
news:10c6slsq8bboi50@corp.supernews.com...
mirror

Where does one get a mirror recoated with Beral?

[Reef1969]

Where does one get a mirror recoated with Beral?

Clausing does the Beral coating. I still fail to see the need if there is
nothing wrong with the coatings on the mirror. There are plenty of things in
this hobby to spend excess cash on instead of replacing perfectly good
components to for the sake of doing it. Stripping coatings does not do any
good to the mirror's surface.

Clear Skies
Richard

[Jan Owen]

--
To reply, remove the "z" if one appears in my address
"Paul Lawler" <stargazer@kilolaniDOT.net> wrote in message
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http://www.clausing.com/

They're in Skokie, Ill.