Oh and I also forgot to say that I'm not sure what Bob May looked
at.  But I don't think he looked at the Foucault images very closely
because they don't look like good spheres to me.  I can see there is
some correction in there.

Bob?

Dale Eason

-- In atm_free@yahoogroups.com, "Mitchell" <Funnybone101@...> wrote:
>
> I'd normally consider that mirror to be a decent
> > sphere tho at this point.
>
> Why does everyone keep saying it is a sphere? It was already
confirmed
> to be at least 1/4 Wave and since then I have only done things to
> parabolize it more.
>
> Mitch
>

Others have talked about a brighter LED.  Here is were to get one
cheap.  I get mine at Walgreen Drug.  From time to time they have a
special on keychain LED flash lights from a company called Club LED.
They cost $2 and have super bright LED's in them that run directly
from 3 volts (2 AA batteries.) They come with 2 mercury cell batteries
that are worth more than the $2.  The have them in blue, red, green,
and white LEDs.  The red ones make good night vision flash lights.

Dale Eason

Hi Mitchell:

Hey, that's better!  Looks pretty good with the edge a little
undercorrected is all; nice diffraction ring - I wouldn't worry about
it too much. Of course you can see the bumps too, but what the heck
(it's a 6" f/6.5?) this mirror will work really well once you get it
in the scope.

Mark


--- In atm_free@yahoogroups.com, "Mitchell" <Funnybone101@...> wrote:
>
>      OKAY I need to get a few things clear.
>
> 1. I had the Ronchi's mislabeled before, they are right now. It is
> indeed a parabola.
>
> 2. I took 6 new Foucualt pictures, 2 second exposures. I know they
> still seem dark but 3 seconds was too much IMO. They are in my
folder.
>
> 3. Some show the 70% zone so-so, others are just images showing the
> roughness.
>
> What do you think?
>
> Mitch
>

Well I got an ATM Meeting tonight so I'll let you know tomorrow
the scoop on my mirror.

Thanks for your unrelenting help in my project!

Mitch

I looked at one photo from June 4th of a green Ronchi test image.
I enlarged the image 2x, increased contrast and brightness to
bring the green to near peak and then sharpened the image twice
to get some sharper lines.  All this was done with the Irfamview
imaging program.  I saw that the hooks led outward by a little
bit and the inward hooks were just starting.  I didn't lay a
straightedge against the screen but the lines did look quite
straight.  I wouldn't think that there would be any more than
about 0.010" difference between the near edge and the center from
what I saw.  Unfortunately I didn't save the image so I can't
show it here and now.
As to the Foucault images, I just glanced at them and really
don't remember them at all.  The Ronchi image was more to what I
was looking at as I was interested in answering the TDE question.
I guess that my thinking of the surface being pretty much
spherical is due to the Ronchi test not being a good indicator of
when a mirror is parabolized properly but rather just indicating
when the shape is pretty much a smooth curve rather than a bunch
of zones going every which way.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

Hi Mark:

I just tracked this down for a different forum discussing the quality
control in Chinese factories and why couldn't their computerized
systems do any better... The answer of course is that the mirrors
come from their peasantized systems.

The thread on the ATM List Archives starts here:

http://astro.umsystem.edu/atm/ARCHIVES/APR04/msg00039.html]ATM List
Archives Posting

I was the one who first suggested they were using a handheld Ronchi
tester for optical evaluation, but nobody took a sample of what was
in the "fan" device... ;)

Best,
Mark Cowan
Salem, OR


--- In atm_free@yahoogroups.com, Mark Holm <mdholm@...> wrote:
>
> I remember, on atmlist.net I think it was, a description of
inspectors
> in Chinese factories turning out mirrors for mass market Newtonians
> using hand held testers.
>
> --
> Mark Holm
> mdholm@...
>

Does anyone know exactly how the Protostar Secondary Holders are
able to fit differen't size tubes? I can't seem to figure out how they
adjust and I was just curious before I ordered a 4-vane one.

BTW, at the ATM meeting we made my mirror worse :)

Pitch too hard + high edge = edge got higher.

Might just go back to spherical, always good to know how to do that.

Once you can go from spherical to a parabola in your sleep you know
all you need to ;)

Mitch

----- Original Message -----

From: Mitchell

To: atm_free@yahoogroups.com

Sent: Thursday, June 08, 2006 1:32 PM

Subject: [atm_free] Spider

Does anyone know exactly how the Protostar Secondary Holders are
able to fit differen't size tubes? I can't seem to figure out how they
adjust and I was just curious before I ordered a 4-vane one.

BTW, at the ATM meeting we made my mirror worse :)

Pitch too hard + high edge = edge got higher.

Might just go back to spherical, always good to know how to do that.

Once you can go from spherical to a parabola in your sleep you know
all you need to ;)

Mitch

--- In atm_free@yahoogroups.com, "tony gondola" <acgna@...> wrote:
>
> They don't. When you order from ProtoStar you'll need to give them
the tube ID and wall thickness and they will make the spider to match.
>
> Tony


Ahh, ok thanks. I'll order it as soon as i built the upper OTA and get
the measurements.

Mitch

-----Original Message-----
From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of Mitchell
Sent: Thursday, June 08, 2006 1:32 PM
To: atm_free@yahoogroups.com
Subject: [atm_free] Spider

Does anyone know exactly how the Protostar Secondary Holders are
able to fit differen't size tubes? I can't seem to figure out how they
adjust and I was just curious before I ordered a 4-vane one.

BTW, at the ATM meeting we made my mirror worse :)

Pitch too hard + high edge = edge got higher.

Might just go back to spherical, always good to know how to do that.

Once you can go from spherical to a parabola in your sleep you know
all you need to ;)

Mitch

How do you know that parabola is the best possible shape?   What if you want a hyperbola?  Do you think it is any easier or harder to make a hyperbola or ellipse instead of a parabola?

 

(intended as an "educational" question only)

 

. . . Richard

 

-----Original Message-----
From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of Mitchell
Sent: Thursday, June 08, 2006 1:32 PM
To: atm_free@yahoogroups.com
Subject: [atm_free] Spider

Does anyone know exactly how the Protostar Secondary Holders are
able to fit differen't size tubes? I can't seem to figure out how they
adjust and I was just curious before I ordered a 4-vane one.

BTW, at the ATM meeting we made my mirror worse :)

Pitch too hard + high edge = edge got higher.

Might just go back to spherical, always good to know how to do that.

Once you can go from spherical to a parabola in your sleep you know
all you need to ;)

Mitch

Can the secondary holder on a 4-vane spider by Protostar be
rotated in any direction. In their pictures it points the diagonal
inbetween two vanes but since i'm using a square upper OTA I need to
be able to point it parallel to a vane.

Thanks,

Mitch

Sometime the spider is mounted at the corners of the square upper
OTA.  That can be the stronger location.  Check the drawings in Tex
2nd addition for an example.

Dale Eason

--- In atm_free@yahoogroups.com, "Mitchell" <Funnybone101@...> wrote:
>
>      Can the secondary holder on a 4-vane spider by Protostar be
> rotated in any direction. In their pictures it points the diagonal
> inbetween two vanes but since i'm using a square upper OTA I need to
> be able to point it parallel to a vane.
>
> Thanks,
>
> Mitch
>

--- In atm_free@yahoogroups.com, "Dale Eason" <atmpob@...> wrote:
>
> Sometime the spider is mounted at the corners of the square upper
> OTA.  That can be the stronger location.  Check the drawings in Tex
> 2nd addition for an example.
>
> Dale Eason

True but the vanes will have to be longer. It may jump up to the next
size they sell then. I want to keep is simple.

Mitch

----- Original Message -----

From: Mitchell

To: atm_free@yahoogroups.com

Sent: Sunday, June 11, 2006 7:17 PM

Subject: [atm_free] Re: Spider

Can the secondary holder on a 4-vane spider by Protostar be
rotated in any direction. In their pictures it points the diagonal
inbetween two vanes but since i'm using a square upper OTA I need to
be able to point it parallel to a vane.

Thanks,

Mitch

----- Original Message -----

From: Mitchell

To: atm_free@yahoogroups.com

Sent: Monday, June 12, 2006 5:09 AM

Subject: [atm_free] Re: Spider

--- In atm_free@yahoogroups.com, "Dale Eason" <atmpob@...> wrote:
>
> Sometime the spider is mounted at the corners of the square upper
> OTA. That can be the stronger location. Check the drawings in Tex
> 2nd addition for an example.
>
> Dale Eason

True but the vanes will have to be longer. It may jump up to the next
size they sell then. I want to keep is simple.

Mitch

Hi,

I have some blanks that I would like to get get curve generation done.
Does anyone have that capability and can do it for a reasonable cost? I
have 3 6" blanks and 3 7" blanks that I would like done.

Thanks

Robert

Actually, curve generation for that small of a glass isn't hard.
Just take a piece of metal and start grinding with it and some 80
grit and you'll have a curve in two hours or so.  I use pipe end
caps for doing the curve generation    It should take you about 2
hours to grind a 6" mirror to F5 if you're diligent about it.  If
you've got several that need to be done, making up a simple
spherometer to measure the sag of each of the mirrors will help
make them all the same depth for a start.
A much larger mirror, in the 15" and up range, it could be easier
to have a deep curve generated but not so much in the smaller
mirrors.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

It look like and other one I see somewhere on the web

he take a pipe and a 4.5 '' grinder whit diamont weel  and only balance
everything over the blanck

be carafuul of the glass particule  make it in a box of metal of some kind
whit cover

jack 47'n71'O



Actually, curve generation for that small of a glass isn't hard.
Just take a piece of metal and start grinding with it and some 80
grit and you'll have a curve in two hours or so.  I use pipe end
caps for doing the curve generation    It should take you about 2
hours to grind a 6" mirror to F5 if you're diligent about it.  If
you've got several that need to be done, making up a simple
spherometer to measure the sag of each of the mirrors will help
make them all the same depth for a start.
A much larger mirror, in the 15" and up range, it could be easier
to have a deep curve generated but not so much in the smaller
mirrors.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.





Yahoo! Groups Links

Yep, look at the size of the blank that the guy is grinding with
the diamond tool and you'll see that it is quite large.  Large
mirrors do need to have a lot of material removed and diamond
wheels, while they aren't all that cheap, do make the glass
removal quick for such large quantities.  For smaller mirrors,
such expenses really aren't worth the effort or money unless
you're doing commercial production of the mirrors.  For one or a
few mirrors, the older technique of hand grinding will do fine as
it really doesn't take that much time.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

Well then I guess my lazyness was showing. Anyway it seems that I
already have the first 6" blank close to F5. That is my target. I also
think I will concede that at this size it is quick enough to take the
glass off by hand.

Robert
--- In atm_free@yahoogroups.com, "Bob May" <bobmay@...> wrote:
>
> Yep, look at the size of the blank that the guy is grinding with
> the diamond tool and you'll see that it is quite large.  Large
> mirrors do need to have a lot of material removed and diamond
> wheels, while they aren't all that cheap, do make the glass
> removal quick for such large quantities.  For smaller mirrors,
> such expenses really aren't worth the effort or money unless
> you're doing commercial production of the mirrors.  For one or a
> few mirrors, the older technique of hand grinding will do fine as
> it really doesn't take that much time.
> Bob May
> bobmay at nethere.com
> http: slash /nav.to slash bobmay
> http: slash /bobmay dot astronomy.net
> Replace the obvious words with the proper character.
>

I've mentioned this before. If you are aquainted with, even casualy, a
mason or block-layer or cement cutter you can often obtain a used
diamond blade in the 14 to 16" size. Most of the time for free. I paid
$1.00 for my 24" and larger blades. Watch garage sales; in the last
year I've bought an air driven tile trimmer with a 5" diamond blade
mounted (for $3.00 and I can use it underwater) and two 8" diamond
blades in new condition (one was brand new) for 50 cents each.
It makes for inexpensive curve generation. Do it yourself.
talquence
PS  It's a rarer but sometimes core-saws (4 to 12" range) are available
too and they can be cut down to make a cup tool for positive meniscus
generation.

I untehrstand your point is ok

I said I have X6 of each size
and it is for give him and other technique you experience is probaly the
beat old method

jack 47'N71'O



Yep, look at the size of the blank that the guy is grinding with
the diamond tool and you'll see that it is quite large.  Large
mirrors do need to have a lot of material removed and diamond
wheels, while they aren't all that cheap, do make the glass
removal quick for such large quantities.  For smaller mirrors,
such expenses really aren't worth the effort or money unless
you're doing commercial production of the mirrors.  For one or a
few mirrors, the older technique of hand grinding will do fine as
it really doesn't take that much time.
Bob May
bobmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.





Yahoo! Groups Links

Ricardo,

> Hi, anyone knows a software that uses a  picture of the mirror under a focault
test as input and calculates the mirror  radius where the shadows null ? I know
James Lerch made something about that,  but coudnīt make contact.

Dale Eason's program NullFinder is located in
Files/NullFinder/nullfinder.zip in the hope page for this group.  This
will allow you to accomplish Foucault readings from images.

--
Steve Koehler

----- Original Message -----

From: Ricardo Dunna

To: atm_free@yahoogroups.com

Sent: Thursday, June 15, 2006 7:58 AM

Subject: [atm_free] Semi automated focault

Hi, anyone knows a software that uses a picture of the mirror under a focault test as input and calculates the mirror radius where the shadows null ? I know James Lerch made something about that, but coudnīt make contact.

 

With my eyes going bad and with new techniques for parabolizing appearing, I canīt do the measurements with the precision I want. My idea is to take "n" pictures of the mirror under test at "n" knife edge positions and use an Excel worksheet to calculate the zone radius of each picture via an external .dll function call.

 

Regards

Ricardo Dunna

http://hps.infolink.com.br/rdunna/