Aftermarket v's Factory supplied mirrors

Part of a response (by Jan Owen) to one of my earlier post (1.25' v's
2" accessories) was:

I have completely refurbished this scope over the years, adding top
quality mirror cells, exquisite mirrors (primary by Mike Spooner,
certified secondary by Antares).

Is it common for experienced astronomers to change out their perfectly
good "stock" mirrors with "after-market" mirrors strictly for higher
performance? Jan states "top quality... exquisite mirrors." Are
Spooner mirrors better than stock mirrors or just good substitutes when
replacements are necessary; as was her situation?

E.g. swapping a perfectly good Rochester Quadrajet carburetor with a
Holly 750, or, a stock Fender pick-up with a Texas special... Just
curious...

Errol
NOLA

Is it common for experienced astronomers to change out their perfectly
good "stock" mirrors with "after-market" mirrors strictly for higher
performance? Jan states "top quality... exquisite mirrors." Are
Spooner mirrors better than stock mirrors or just good substitutes when
replacements are necessary; as was her situation?

Almost certainly better, but would you know the difference? Maybe you
would, or would at some point in the future, and maybe you woudn't. Maybe
you don't care and just want something of high quality because you like high
quality stuff.

Anyway, tonight is looking pretty good (finally), and my sons and a couple
of friends and I are going to do a bit of observing and not worry about
equipment.

Dennis

Starboard wrote:
Part of a response (by Jan Owen) to one of my earlier post (1.25' v's
2" accessories) was:


I have completely refurbished this scope over the years, adding top
quality mirror cells, exquisite mirrors (primary by Mike Spooner,
certified secondary by Antares).


Is it common for experienced astronomers to change out their perfectly
good "stock" mirrors with "after-market" mirrors strictly for higher
performance?

It may depend on the quality of the rest of the scope. It might make
sense to upgrade the elements of an otherwise premium Dob, but likely
would not for a more basic scope (e.g, Orion XT-10).

Phil

I've read that some folks grind their own mirrors. How successful are
they? I understanding that some folks are talented, but can a
commercial grade mirror be made without the use of "very expensive"
machinery? Have you looked through a scope with (a) home-made
mirror(s)? Or. is it something that one does for the pure sport of it?
It seems like quite and undertaking.

In fact, I thinking of putting it off a while.

Some might be inclined to make a fire by striking two stones together..
It's not terribly efficient in our age of advance pyrodynamics (oh,
the flair to create new words upon demand), but, still, there must be a
certain feeling of achievement in doing it..

JC

Errol
NOLA

I've read that some folks grind their own mirrors. How successful are
they? I understanding that some folks are talented, but can a
commercial grade mirror be made without the use of "very expensive"
machinery? Have you looked through a scope with (a) home-made
mirror(s)? Or. is it something that one does for the pure sport of it?
It seems like quite and undertaking.

Homemade mirrors can be awful, good, excellent, etc. We have three homemade
mirrors that
are very good to excellent, and one not so good (astigmatism). For us and
some of our firiends, making mirrors is an important part of amateur
astronomy. For others, mirror making is a one time thing. And for many
others, it is not of interest. However, I find the Foucault test simply
amazing and beautiful, and encourage everyone in our club to take a look at
least once.

In fact, I thinking of putting it off a while.


Why not buy a scope and start grinding a mirror - this way you will not have
to put off observing until your homemade scope is complete!

Dennis

Dennis,

Thanks. I do have a scope on order. I couldn't resist asking about the
homemade mirror. Definitely fascinating that one can actually make a
usable spherical or parabolic mirror.

I'm reading this link on foucault testing now.
http://www.jlc.net/~force5/Astro/ATM...ultTester.html

I hope to meet some astronomers in my area with similar interest.

Errol
NOLA

Starboard wrote:
Dennis,

Thanks. I do have a scope on order. I couldn't resist asking about the
homemade mirror. Definitely fascinating that one can actually make a
usable spherical or parabolic mirror.

I'm reading this link on foucault testing now.
http://www.jlc.net/~force5/Astro/ATM...ultTester.html

I hope to meet some astronomers in my area with similar interest.


One forum on the topic of ATM is he

http://www.cloudynights.com/ubbthrea...at/0/Board/atm

When I was a lad, most backyard telescopes were homemade. In high
school one of my friends had a 6 inch newtonian (his mirror) on a pier
in his backyard (in a Portland, OR suburb). He went on in life to
become an astrophysisist/astronomer and an investigator for HEAO and
Chandra.

My hobby at the time was amateur radio, and I became an EE. Ironically
we met later in life, because I was involved in design of the two
observatories he had experiments on.

Our friend the class politician became a lawyer, and came to no good end :-)

Phil

Starboard wrote:
Or. is it something that one does for the pure sport of it?

I had the sort-lived but very intriguing idea that I could teach myself
about optics well enough to slowly, carefully, grind my own lenses and
make a 6 or 7 inch semi-apochromatic refractor.

I started looking through a lens design book and it quickly began to
look nearly impossible to hand grind and match the lenses without having
a lot of expensive tools and testing devices. I only have the standard
assortment of Craftsman house tools.

If RC or TB or anyone who knows about this firsthand is reading this and
would comment...is it impossible or nearly so to hand grind an
apochromatic lens? What is the minimum of tools and testing equipment
needed?

I made a 6in reflector for Astronomy 101 in college and that was a lot
of fun. My professor was Dr. Walker Baker, who enjoyed teaching inmates
(prisoners) Astronomy in his spare time. He always commented that he
couldn't figure out exactly how they managed to cheat on his tests, but
a group of them always had the same answers. Then he showed graphs of
our performance compared to the inmates. To give you a better idea of
his sense of humor...he had a bumper sticker that read "Eschew
Obfuscation".

--
Clear Skies,
Paul Murphy

(remove gemini to email me)

Many really good scopes have mirrors made by am.astronomers. That's why I
run a small ATM list.



The mirror in my Babylon 8 was made by such a person, not me but someone
else.


--

The Lone Sidewalk Astronomer of Rosamond
Telescope Buyers FAQ
http://home.inreach.com/starlord
Astronomy Net Online Gift Shop
http://www.cafepress.com/astronomy_net
In Garden Online Gift Shop
http://www.cafepress.com/ingarden
Blast Off Online Gift Shop
http://www.cafepress.com/starlords




"Starboard" wrote in message
oups.com...
I've read that some folks grind their own mirrors. How successful are
they? I understanding that some folks are talented, but can a
commercial grade mirror be made without the use of "very expensive"
machinery? Have you looked through a scope with (a) home-made
mirror(s)? Or. is it something that one does for the pure sport of it?
It seems like quite and undertaking.

In fact, I thinking of putting it off a while.

Some might be inclined to make a fire by striking two stones together..
It's not terribly efficient in our age of advance pyrodynamics (oh,
the flair to create new words upon demand), but, still, there must be a
certain feeling of achievement in doing it..

JC

Errol
NOLA

Phil Wheeler wrote:

It may depend on the quality of the rest of the scope. It might make
sense to upgrade the elements of an otherwise premium Dob, but likely
would not for a more basic scope (e.g, Orion XT-10).

However, if one had the ambition to construct a high quality telescope
while also observing in the meantime, a "basic scope" gradually morphed
into that HQ scope might make sense provided one went into the process
recognizing that nothing would actually remain of the original scope(1).

(1) After replacing ALL components while producing the HQ scope, one
could reassemble the original "basic scope" and donate it to an
appropriate home.