[ap-gto] [ap-ug] Life after the Stowaway


Dean S
 

I have the first 12” newt that AGO made several years ago.  After a couple modifications and improvements, by them, it is an outstanding fast astrograph.   He only made a few of these, and a couple 10” too.  Costs to make these correctly is high.  Very high.  Which is probably why he stopped after a couple years.   Mine is a keeper, as long as I have an observatory to keep it in.  

I’m sure if AP made one it would be world class, but at a huge cost.  

Dean
 


On Jan 18, 2022, at 10:52 PM, Roland Christen via groups.io <chris1011@...> wrote:



You know what? Back in the day we used to make mirrors out of Pyrex because it has fairly low expansion coefficient. That means the mirror's figure would not change as the temperature dropped. If you really wanted to drop some coin on a mirror blank, you went for quartz which had a fraction of the expansion of Pyrex. Plate glass was considered bogus because it will not hold a decent figure when the temperature drops (as it does in most places).

What do we have nowadays? Well, those cheap and cheerful Asian imports use borosilicate crown (BK7 equivalent), which has the same expansion coefficient as cheap plate glass. And people are joyful as bunny rabbits in a carrot patch. I can't compete with that because people just don't know stuff any more, like what we knew back in the days of Sky&Tel with their "Gleanings for Amateurs" series. Heck, you could probably sell plastic mirrors now and claim 0.99 Strehl. I'm betting someone is already working on that as we speak.
Smile

For me, I like quartz optics in a reflector. Would not make them any other way. Quartz holds its shape even when the mirror is very thin and light weight. My 17" Quartz Cassegrain astrograph has a mirror that is only 12.5mm thick at the edges. I can hold it up in my right hand. It sheds heat so fast that it basically does not have any cooldown time. I also have  10" and 12" quartz Mak-Cass astrographs that work the same way. They have thin mirrors that shed heat quickly and are ready to use in minutes. On a typical winter day the temperature can drop from 38F to 4F in a matter of 2 hours. Focus doesn't change in these quartz-carbon fiber scopes. The problem is the expectations of amateurs to have large aperture optics at near zero cost. For that to happen you can forget getting it made in the USA. A raw quartz blank costs more than a complete finished Newtonian with a cheap and cheerful import mount thrown in for good measure (well I'm maybe stretching it a bit).

Celestron and Meade pretty much put the kabosh on anything Cassegrain. Fact is they use plate glass optics and aluminum tubes, which together pretty much insures that you are constantly fiddling with the focus knob. Plus you have those nice heat plumes that run up the baffle tubes. Do people know that's happening? Do they really care? Probably not because they got them brand new and shiny at ridiculously low cost. And somehow they can make them work, although I'm completely baffled how they manage it.

Rolando

-----Original Message-----
From: ROBERT WYNNE <robert-wynne@...>
To: chris1011@...
Sent: Tue, Jan 18, 2022 8:08 pm
Subject: Re: [ap-ug] Life after the Stowaway

I think because we all believe you probably have access to superior blanks and provide the best mirror figuring in the world. Plus, Newtonians are relatively inexpensive to manufacture but A-P as imatter stand could set its own price on Newtonians and still have the highest gross margins in the business. Unless competing projects, space and machining time is a concern. I wonder if manufacturing Newtonians would be a good introduction to the craft for new employees. -Best, Robert
On 01/18/2022 8:19 AM chris1011@... wrote:


You can buy Newtonians at a dime a dozen out of Asia. Why would I want to compete with that? Stuck out tongue winking eye

Rolando


-----Original Message-----
From: ROBERT WYNNE <robert-wynne@...>
To: main@ap-ug.groups.io; Arun Hegde <arun.k.hegde@...>
Sent: Mon, Jan 17, 2022 7:17 pm
Subject: Re: [ap-ug] Life after the Stowaway

I'll second that vote. The little I know about lens figuring a Newtonian is a relatively fast mirror to figure. I have three old Newtonians and they are all good performers but not all are compatible with my Televues. The inexpensive eyepieces that originally came with the scope are very poor except for the bargain lot of 6 I got with an old 10" Trekerscope. They were all marked Orthoscope and made at a time when Leland Barnes was the head optician for Coast. I sometimes use the Barnes eyepieces in preference to the Televiews due the sharp high contrast images. End of the lottery. I must be the luckiest person alive. My Stowaway arrived the first week of January. -Best, Robert
On 01/17/2022 7:59 AM Arun Hegde <arun.k.hegde@...> wrote:


If AP is taking requests or we are voting, mine would be for a fast Newtonian that works without complaint in cold temperatures.


dvjbaja
 

Reissue the Mach 1. Build it, and they will come.  Yuri over at TEC seems to be producing the larger refractors now.  He's also exploring a 100mm binoscope.      

Unistellar and Stalina are doing the. 
 first gen all in ones.  I see that category about to be copied by the Chinese.  

J





Sent via the Samsung Galaxy Note9, an AT&T 5G Evolution capable smartphone


Roland Christen
 

If you want a really high quality mirror, Lockwood is the place to go. Not cheap but very high quality. He can make mirrors as large as you want (30", 40" +).

Rolando

-----Original Message-----
From: Dean S <dean@...>
To: main@ap-ug.groups.io
Sent: Wed, Jan 19, 2022 8:08 am
Subject: Re: [ap-gto] [ap-ug] Life after the Stowaway

I have the first 12” newt that AGO made several years ago.  After a couple modifications and improvements, by them, it is an outstanding fast astrograph.   He only made a few of these, and a couple 10” too.  Costs to make these correctly is high.  Very high.  Which is probably why he stopped after a couple years.   Mine is a keeper, as long as I have an observatory to keep it in.  

I’m sure if AP made one it would be world class, but at a huge cost.  

Dean
 


On Jan 18, 2022, at 10:52 PM, Roland Christen via groups.io <chris1011@...> wrote:



You know what? Back in the day we used to make mirrors out of Pyrex because it has fairly low expansion coefficient. That means the mirror's figure would not change as the temperature dropped. If you really wanted to drop some coin on a mirror blank, you went for quartz which had a fraction of the expansion of Pyrex. Plate glass was considered bogus because it will not hold a decent figure when the temperature drops (as it does in most places).

What do we have nowadays? Well, those cheap and cheerful Asian imports use borosilicate crown (BK7 equivalent), which has the same expansion coefficient as cheap plate glass. And people are joyful as bunny rabbits in a carrot patch. I can't compete with that because people just don't know stuff any more, like what we knew back in the days of Sky&Tel with their "Gleanings for Amateurs" series. Heck, you could probably sell plastic mirrors now and claim 0.99 Strehl. I'm betting someone is already working on that as we speak.
Smile

For me, I like quartz optics in a reflector. Would not make them any other way. Quartz holds its shape even when the mirror is very thin and light weight. My 17" Quartz Cassegrain astrograph has a mirror that is only 12.5mm thick at the edges. I can hold it up in my right hand. It sheds heat so fast that it basically does not have any cooldown time. I also have  10" and 12" quartz Mak-Cass astrographs that work the same way. They have thin mirrors that shed heat quickly and are ready to use in minutes. On a typical winter day the temperature can drop from 38F to 4F in a matter of 2 hours. Focus doesn't change in these quartz-carbon fiber scopes. The problem is the expectations of amateurs to have large aperture optics at near zero cost. For that to happen you can forget getting it made in the USA. A raw quartz blank costs more than a complete finished Newtonian with a cheap and cheerful import mount thrown in for good measure (well I'm maybe stretching it a bit).

Celestron and Meade pretty much put the kabosh on anything Cassegrain. Fact is they use plate glass optics and aluminum tubes, which together pretty much insures that you are constantly fiddling with the focus knob. Plus you have those nice heat plumes that run up the baffle tubes. Do people know that's happening? Do they really care? Probably not because they got them brand new and shiny at ridiculously low cost. And somehow they can make them work, although I'm completely baffled how they manage it.

Rolando

-----Original Message-----
From: ROBERT WYNNE <robert-wynne@...>
To: chris1011@...
Sent: Tue, Jan 18, 2022 8:08 pm
Subject: Re: [ap-ug] Life after the Stowaway

I think because we all believe you probably have access to superior blanks and provide the best mirror figuring in the world. Plus, Newtonians are relatively inexpensive to manufacture but A-P as imatter stand could set its own price on Newtonians and still have the highest gross margins in the business. Unless competing projects, space and machining time is a concern. I wonder if manufacturing Newtonians would be a good introduction to the craft for new employees. -Best, Robert
On 01/18/2022 8:19 AM chris1011@... wrote:


You can buy Newtonians at a dime a dozen out of Asia. Why would I want to compete with that? Stuck out tongue winking eye

Rolando


-----Original Message-----
From: ROBERT WYNNE <robert-wynne@...>
To: main@ap-ug.groups.io; Arun Hegde <arun.k.hegde@...>
Sent: Mon, Jan 17, 2022 7:17 pm
Subject: Re: [ap-ug] Life after the Stowaway

I'll second that vote. The little I know about lens figuring a Newtonian is a relatively fast mirror to figure. I have three old Newtonians and they are all good performers but not all are compatible with my Televues. The inexpensive eyepieces that originally came with the scope are very poor except for the bargain lot of 6 I got with an old 10" Trekerscope. They were all marked Orthoscope and made at a time when Leland Barnes was the head optician for Coast. I sometimes use the Barnes eyepieces in preference to the Televiews due the sharp high contrast images. End of the lottery. I must be the luckiest person alive. My Stowaway arrived the first week of January. -Best, Robert
On 01/17/2022 7:59 AM Arun Hegde <arun.k.hegde@...> wrote:


If AP is taking requests or we are voting, mine would be for a fast Newtonian that works without complaint in cold temperatures.


Dean S
 

Dave at AG Optical use Terry Ostahowski for his astrograph mirrors.  Mine is quartz and very stable.  If I wanted bigger and faster then I agree that Mike Lockwood is the guy.  


On Jan 19, 2022, at 11:00 AM, Roland Christen via groups.io <chris1011@...> wrote:


If you want a really high quality mirror, Lockwood is the place to go. Not cheap but very high quality. He can make mirrors as large as you want (30", 40" +).

Rolando

-----Original Message-----
From: Dean S <dean@...>
To: main@ap-ug.groups.io
Sent: Wed, Jan 19, 2022 8:08 am
Subject: Re: [ap-gto] [ap-ug] Life after the Stowaway

I have the first 12” newt that AGO made several years ago.  After a couple modifications and improvements, by them, it is an outstanding fast astrograph.   He only made a few of these, and a couple 10” too.  Costs to make these correctly is high.  Very high.  Which is probably why he stopped after a couple years.   Mine is a keeper, as long as I have an observatory to keep it in.  

I’m sure if AP made one it would be world class, but at a huge cost.  

Dean
 


On Jan 18, 2022, at 10:52 PM, Roland Christen via groups.io <chris1011@...> wrote:



You know what? Back in the day we used to make mirrors out of Pyrex because it has fairly low expansion coefficient. That means the mirror's figure would not change as the temperature dropped. If you really wanted to drop some coin on a mirror blank, you went for quartz which had a fraction of the expansion of Pyrex. Plate glass was considered bogus because it will not hold a decent figure when the temperature drops (as it does in most places).

What do we have nowadays? Well, those cheap and cheerful Asian imports use borosilicate crown (BK7 equivalent), which has the same expansion coefficient as cheap plate glass. And people are joyful as bunny rabbits in a carrot patch. I can't compete with that because people just don't know stuff any more, like what we knew back in the days of Sky&Tel with their "Gleanings for Amateurs" series. Heck, you could probably sell plastic mirrors now and claim 0.99 Strehl. I'm betting someone is already working on that as we speak.
Smile

For me, I like quartz optics in a reflector. Would not make them any other way. Quartz holds its shape even when the mirror is very thin and light weight. My 17" Quartz Cassegrain astrograph has a mirror that is only 12.5mm thick at the edges. I can hold it up in my right hand. It sheds heat so fast that it basically does not have any cooldown time. I also have  10" and 12" quartz Mak-Cass astrographs that work the same way. They have thin mirrors that shed heat quickly and are ready to use in minutes. On a typical winter day the temperature can drop from 38F to 4F in a matter of 2 hours. Focus doesn't change in these quartz-carbon fiber scopes. The problem is the expectations of amateurs to have large aperture optics at near zero cost. For that to happen you can forget getting it made in the USA. A raw quartz blank costs more than a complete finished Newtonian with a cheap and cheerful import mount thrown in for good measure (well I'm maybe stretching it a bit).

Celestron and Meade pretty much put the kabosh on anything Cassegrain. Fact is they use plate glass optics and aluminum tubes, which together pretty much insures that you are constantly fiddling with the focus knob. Plus you have those nice heat plumes that run up the baffle tubes. Do people know that's happening? Do they really care? Probably not because they got them brand new and shiny at ridiculously low cost. And somehow they can make them work, although I'm completely baffled how they manage it.

Rolando

-----Original Message-----
From: ROBERT WYNNE <robert-wynne@...>
To: chris1011@...
Sent: Tue, Jan 18, 2022 8:08 pm
Subject: Re: [ap-ug] Life after the Stowaway

I think because we all believe you probably have access to superior blanks and provide the best mirror figuring in the world. Plus, Newtonians are relatively inexpensive to manufacture but A-P as imatter stand could set its own price on Newtonians and still have the highest gross margins in the business. Unless competing projects, space and machining time is a concern. I wonder if manufacturing Newtonians would be a good introduction to the craft for new employees. -Best, Robert
On 01/18/2022 8:19 AM chris1011@... wrote:


You can buy Newtonians at a dime a dozen out of Asia. Why would I want to compete with that? Stuck out tongue winking eye

Rolando


-----Original Message-----
From: ROBERT WYNNE <robert-wynne@...>
To: main@ap-ug.groups.io; Arun Hegde <arun.k.hegde@...>
Sent: Mon, Jan 17, 2022 7:17 pm
Subject: Re: [ap-ug] Life after the Stowaway

I'll second that vote. The little I know about lens figuring a Newtonian is a relatively fast mirror to figure. I have three old Newtonians and they are all good performers but not all are compatible with my Televues. The inexpensive eyepieces that originally came with the scope are very poor except for the bargain lot of 6 I got with an old 10" Trekerscope. They were all marked Orthoscope and made at a time when Leland Barnes was the head optician for Coast. I sometimes use the Barnes eyepieces in preference to the Televiews due the sharp high contrast images. End of the lottery. I must be the luckiest person alive. My Stowaway arrived the first week of January. -Best, Robert
On 01/17/2022 7:59 AM Arun Hegde <arun.k.hegde@...> wrote:


If AP is taking requests or we are voting, mine would be for a fast Newtonian that works without complaint in cold temperatures.


Barry Megdal
 

Don’t forget Carl Zambuto – he has stopped making mirrors as large as those Mike Lockwood does, but I have one of his 24” mirrors in a Starmaster Dob, and the image quality is truly spectacular.

 

  • Barry

 

Dr. Barry Megdal

 

President

Shb Instruments, Inc.

19215 Parthenia St.  Suite A

Northridge, CA 91324

www.shbinstruments.com

(818) 773-2000

bmegdal@...

 

Faculty (retired)

Dept. of Electrical Engineering

Caltech

 


Dean S
 

Is there any special consideration given when making a mirror for visual vs  imaging use?  Not counting F ratio.

 

My 18” Zambuto is awesome as expected.  I also have a 12” mirror made by Terry Osthowski  that was originally for an astrograph but I put it in a dob and it also is excellent.

 

 

 

From: main@ap-ug.groups.io [mailto:main@ap-ug.groups.io] On Behalf Of Barry Megdal
Sent: Wednesday, January 19, 2022 6:10 PM
To: main@ap-ug.groups.io
Subject: Re: [ap-gto] [ap-ug] Life after the Stowaway

 

Don’t forget Carl Zambuto – he has stopped making mirrors as large as those Mike Lockwood does, but I have one of his 24” mirrors in a Starmaster Dob, and the image quality is truly spectacular.

 

  • Barry

 

Dr. Barry Megdal

 

President

Shb Instruments, Inc.

19215 Parthenia St.  Suite A

Northridge, CA 91324

www.shbinstruments.com

(818) 773-2000

bmegdal@...

 

Faculty (retired)

Dept. of Electrical Engineering

Caltech

 




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ROBERT WYNNE
 

I'm out on a limb here but I don't think so. -Best, Robert

On 01/19/2022 4:12 PM Dean S <dean@...> wrote:


Is there any special consideration given when making a mirror for visual vs  imaging use?  Not counting F ratio.

 

My 18” Zambuto is awesome as expected.  I also have a 12” mirror made by Terry Osthowski  that was originally for an astrograph but I put it in a dob and it also is excellent.

 

 

 

From: main@ap-ug.groups.io [mailto:main@ap-ug.groups.io] On Behalf Of Barry Megdal
Sent: Wednesday, January 19, 2022 6:10 PM
To: main@ap-ug.groups.io
Subject: Re: [ap-gto] [ap-ug] Life after the Stowaway


Don’t forget Carl Zambuto – he has stopped making mirrors as large as those Mike Lockwood does, but I have one of his 24” mirrors in a Starmaster Dob, and the image quality is truly spectacular.


  • Barry


Dr. Barry Megdal


President

Shb Instruments, Inc.

19215 Parthenia St.  Suite A

Northridge, CA 91324

www.shbinstruments.com

(818) 773-2000

bmegdal@...


Faculty (retired)

Dept. of Electrical Engineering

Caltech






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This email has been checked for viruses by Avast antivirus software.
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Roland Christen
 

Depends what the mirror is used in:

For a Newtonian there is only one way to figure the surface. It has to be a parabola.
For a Classical Cass it also has to be a parabola but the secondary has to be a hyperbola.
For a Dall-Kirkham it can be anything from 50% to 75% of a parabola, depending on the amount of coma that can be tolerated.
For a CDK (Corrected Dall-Kirkham) it's around 70% with a spherical primary.
For a Maksutov, both mirrors can be spheres, but the primary will have a 5th order correction if you want better than 1/4 wave.
For a spot Mak, the primary mirror will have an ellipsoid with some 5th order thrown in - a rather more complicated surface if you want better than 1/4 wave.

And that's just a partial list, there are many variations that can be used depending on what the final goal is.

Rolando

-----Original Message-----
From: Dean S <dean@...>
To: main@ap-ug.groups.io
Sent: Wed, Jan 19, 2022 6:12 pm
Subject: Re: [ap-gto] [ap-ug] Life after the Stowaway

Is there any special consideration given when making a mirror for visual vs  imaging use?  Not counting F ratio.
 
My 18” Zambuto is awesome as expected.  I also have a 12” mirror made by Terry Osthowski  that was originally for an astrograph but I put it in a dob and it also is excellent.
 
 
 
From: main@ap-ug.groups.io [mailto:main@ap-ug.groups.io] On Behalf Of Barry Megdal
Sent: Wednesday, January 19, 2022 6:10 PM
To: main@ap-ug.groups.io
Subject: Re: [ap-gto] [ap-ug] Life after the Stowaway
 
Don’t forget Carl Zambuto – he has stopped making mirrors as large as those Mike Lockwood does, but I have one of his 24” mirrors in a Starmaster Dob, and the image quality is truly spectacular.
 
  • Barry
 
Dr. Barry Megdal
 
President
Shb Instruments, Inc.
19215 Parthenia St.  Suite A
Northridge, CA 91324
(818) 773-2000
 
Faculty (retired)
Dept. of Electrical Engineering
Caltech
 



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Jay Freeman
 

There is of course one special problem with reflectors ...

https://xkcd.com/1791/

I still want my Starfire plush toy! Real Starfires are too cold and angular to cuddle.

-- Jay Reynolds Freeman
---------------------
Jay_Reynolds_Freeman@mac.com
http://JayReynoldsFreeman.com (personal web site)


ROBERT WYNNE
 

There's there is no difference among the lot so far as fabrication for observation vs. imaging? -Best, Robert

On 01/19/2022 5:04 PM Roland Christen via groups.io <chris1011@...> wrote:


Depends what the mirror is used in:

For a Newtonian there is only one way to figure the surface. It has to be a parabola.
For a Classical Cass it also has to be a parabola but the secondary has to be a hyperbola.
For a Dall-Kirkham it can be anything from 50% to 75% of a parabola, depending on the amount of coma that can be tolerated.
For a CDK (Corrected Dall-Kirkham) it's around 70% with a spherical primary.
For a Maksutov, both mirrors can be spheres, but the primary will have a 5th order correction if you want better than 1/4 wave.
For a spot Mak, the primary mirror will have an ellipsoid with some 5th order thrown in - a rather more complicated surface if you want better than 1/4 wave.

And that's just a partial list, there are many variations that can be used depending on what the final goal is.

Rolando

-----Original Message-----
From: Dean S <dean@...>
To: main@ap-ug.groups.io
Sent: Wed, Jan 19, 2022 6:12 pm
Subject: Re: [ap-gto] [ap-ug] Life after the Stowaway

Is there any special consideration given when making a mirror for visual vs  imaging use?  Not counting F ratio.
 
My 18” Zambuto is awesome as expected.  I also have a 12” mirror made by Terry Osthowski  that was originally for an astrograph but I put it in a dob and it also is excellent.
 
 
 
From: main@ap-ug.groups.io [mailto:main@ap-ug.groups.io] On Behalf Of Barry Megdal
Sent: Wednesday, January 19, 2022 6:10 PM
To: main@ap-ug.groups.io
Subject: Re: [ap-gto] [ap-ug] Life after the Stowaway

Don’t forget Carl Zambuto – he has stopped making mirrors as large as those Mike Lockwood does, but I have one of his 24” mirrors in a Starmaster Dob, and the image quality is truly spectacular.

  • Barry

Dr. Barry Megdal

President
Shb Instruments, Inc.
19215 Parthenia St.  Suite A
Northridge, CA 91324
(818) 773-2000

Faculty (retired)
Dept. of Electrical Engineering
Caltech





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This email has been checked for viruses by Avast antivirus software.
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