Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Planetary reflectors

reflector
  • Please log in to reply
157 replies to this topic

#1 Snoringbear

Snoringbear

    Vostok 1

  • *****
  • topic starter
  • Posts: 164
  • Joined: 07 Mar 2016
  • Loc: Albuquerque,NM

Posted 28 April 2016 - 06:09 PM

Why don't telescope manufacturers make a high quality 6, 8 or 10 inch F8 reflector anymore?


  • gitane71 and Charlespl like this

#2 SeattleScott

SeattleScott

    Fly Me to the Moon

  • *****
  • Posts: 6,881
  • Joined: 14 Oct 2011

Posted 28 April 2016 - 06:27 PM

Reflectors have the lowest cost per aperture so people who get them are usually looking for something affordable. For the others, there are the high end dobs. Not much available in the US for high quality eq mounted Newtonian scopes since Parks closed up shop, but Europeans have some options. Or Americans can pay for int'l shipping if that is something they want, or order a custom scope from Parallax or someone. Bottom line is there just isn't much demand. The high end stuff is usually custom built so they want you to buy something bigger than 6" so they can make more margin. For the right price, someone will build it. But high end reflectors are normally custom built these days. 

 

Scott



#3 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 23,349
  • Joined: 22 Feb 2010

Posted 28 April 2016 - 06:36 PM

They're not profitable, if they were you'd see as any long newt as you do sct's. 


  • Deep13, vasilas432 and havasman like this

#4 havasman

havasman

    Voyager 1

  • ****-
  • Posts: 10,303
  • Joined: 04 Aug 2013
  • Loc: Dallas, Texas

Posted 28 April 2016 - 06:42 PM

Most folks don't want huge Newts. So there's SCT's. 

In fact I think Meade makes an f8 reflector.

Yep: http://www.meade.com...acf-10-f-8.html

10" f8 reflector


Edited by havasman, 28 April 2016 - 06:47 PM.

  • Sarkikos likes this

#5 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18,935
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 28 April 2016 - 07:15 PM

Most folks don't want huge Newts. So there's SCT's. 

In fact I think Meade makes an f8 reflector.

Yep: http://www.meade.com...acf-10-f-8.html

10" f8 reflector

That is a CAT.

 

I have my 8" F/8.5 Cave out now waiting for it to get dark. Best to buy a used slow Newt if one pops up local.


  • Bomber Bob likes this

#6 havasman

havasman

    Voyager 1

  • ****-
  • Posts: 10,303
  • Joined: 04 Aug 2013
  • Loc: Dallas, Texas

Posted 28 April 2016 - 07:30 PM

The OP made no qualification that only included Newtonian reflectors. Yes, it is.


  • Sarkikos likes this

#7 Jeff Morgan

Jeff Morgan

    Voyager 1

  • *****
  • Posts: 11,525
  • Joined: 28 Sep 2003
  • Loc: Prescott, AZ

Posted 28 April 2016 - 07:55 PM

Why don't telescope manufacturers make a high quality 6, 8 or 10 inch F8 reflector anymore?

 

I think the real answer is where the bulk of observing interest lies - the deep sky. The emphasis is on portability and wide field for a given aperture.

 

Optimizing for planetary performance is a small niche. When margins are small, you'd better be selling to big niche.



#8 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18,935
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 28 April 2016 - 08:08 PM

I reflector to me is a Newt.  


  • Scanning4Comets and mikeDnight like this

#9 The Ardent

The Ardent

    Aurora

  • *****
  • Moderators
  • Posts: 4,679
  • Joined: 24 Oct 2008
  • Loc: Virginia

Posted 28 April 2016 - 08:29 PM

My f/3.5 dob is the best planetary scope I have ever used. It's only part(the main part) of a system of planetary observing. Most of its avantage is aperture. If I had a larger scope then that would be better.
F/ratio is only one variable for planetary observing, and far from the most important.

And to really answer the op, look at the 6" f/10

http://www.teeterste...#!in-stock/ccz0

Or this
http://www.cloudynig...holder-primary/
  • Jon Isaacs and havasman like this

#10 Keith Rivich

Keith Rivich

    Surveyor 1

  • *****
  • Posts: 1,979
  • Joined: 17 Jun 2011
  • Loc: Cypress, Tx

Posted 28 April 2016 - 09:48 PM

Economics 101....they build what sells. 



#11 Jeff Morgan

Jeff Morgan

    Voyager 1

  • *****
  • Posts: 11,525
  • Joined: 28 Sep 2003
  • Loc: Prescott, AZ

Posted 28 April 2016 - 10:30 PM

Life is short. If this is the scope you want, you can build it, and more easily than you think. You can buy the components already finished, make some of them, or even make them all at home. Assembly is pretty easy too.

 

Here are a few great threads on the optimized Newtonian:

 

http://tinyurl.com/mpqcgav
http://tinyurl.com/mpuqco3
http://tinyurl.com/l34h6sv
http://tinyurl.com/m8wc8o4

 

Follow those principles, and the battle is mostly won.


  • Max T and Herr Ointment like this

#12 Cotts

Cotts

    Just Wondering

  • *****
  • Moderators
  • Posts: 9,988
  • Joined: 10 Oct 2005
  • Loc: Madoc, Ontario

Posted 28 April 2016 - 10:38 PM

 6" f/8 newt/dobs  are available for well under $1000 from several manufacturers.  They have tiny central obstructions around 15 - 20% by diameter.  Light, portable.....  They put up 'quality' views..  

 

And here's the thing:  they are often excellent optically and guaranteed to be 100% APOchromatic, something no refractor on Earth can claim....   

 

True story.  I helped to get a surprise birthday scope for a friend few years ago and the selected scope was a 6" f/8 dob from Skywatcher (IIRC but certainly a generic Chinese scope) for about $500.  Later on I visited him with my 1988 AP APO 6" refractor.  The dob kept up, toe to toe with the APO, on planets and double stars.  If it weren't for the diffraction from the spider you couldn't hardly tell the difference between the two scopes.  Both telescopes produced beautiful and identical diffraction patterns at something like 150x or more.... Identical can't-tell-them-apart images.

 

Dave


  • CollinofAlabama, Mr. Marbles, Achernar and 6 others like this

#13 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 81,829
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 29 April 2016 - 04:29 AM

 

 

My f/3.5 dob is the best planetary scope I have ever used. It's only part(the main part) of a system of planetary observing. Most of its avantage is aperture. If I had a larger scope then that would be better.
F/ratio is only one variable for planetary observing, and far from the most important.

 

 

:waytogo:

 

When it comes to performance, aperture is the most important factor, it determines resolution and contrast transfer.  Focal ratio is a minor player.  

 

When it comes to the hassle factor and viewing comfort, focal length is the most important factor.  Aperture is of lesser importance.

 

These days high quality, fast mirrors that cool quickly are available.  Back when, the eyepieces that performed at F/4 and F/5 were not available, high quality fast mirrors were uncommon.  But this is 2016..

 

If one steps back, thinks in a different paradigm, fixed focal length instead of fixed aperture, then it's reasonably clear that a well made a 16 inch F/4 or a 12 inch F/5.3 will provide more detailed an contrastier planetary views than an 8 inch F/8.  There was a time when I owned four scopes, all with focal lengths between 48 inches and 51 inches:  The classic RV-6 at 6 inch F/8.3, an 8 inch F/6 Dob, my 10 inch F/5 Dob and the 12.5 inch F/4.06 Discovery.   

 

At the eyepiece, the 6 inch F/8 provided good views of the planets and double stars but the 12.5 inch F/4.06 showed more detail, more contrast, there was really no contest in which provides the better planetary views.. 

 

Two scopes to consider:

 

Jeff Morgan's 16 inch F/7 with a Zambuto mirror, my 16 inch F/4.42 with a mirror Mike Spooner refigured.  I am sure that Jeff's scope provides slightly/somewhat better planetary views than my scope, it has a smaller secondary and the longer focal ratio does add a small advantage.  

 

But Jeff's scope has a focal length of 112 inches and requires the same ladder I use with my 25 inch F/5.  My 16 inch is a flat foot scope, no ladder, it's an easy setup and still provides excellent views of the planets when the seeing supports it.  I used to haul it around in a Ford Escort station wagon.

 

So now, Jeff has been building a smaller, "No Ladder planetary scope."  I am not sure if it is an 8 inch or a 10 inch but I have to think that if he and I were to compare my no ladder 16 inch to his no ladder 8 or 10 inch, the 16 inch would provide the better views of the planets, split the closer doubles.. And then of course, there's the deep sky.. 

 

That's how I see it.  Aperture is my friend when it comes to providing the good planetary views, a long focal length, it's a hassle.  Don't start out thinking, "What is the best planetary scope with a 12 inch mirror?", think, "What is the best planetary scope with a 70 inch focal length?"

 

The answer you get depends on the question you ask.

 

Just sayin'

 

Jon Isaacs


  • Achernar, KaStern, Sarkikos and 7 others like this

#14 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18,935
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 29 April 2016 - 05:11 AM

 

 

 

My f/3.5 dob is the best planetary scope I have ever used. It's only part(the main part) of a system of planetary observing. Most of its avantage is aperture. If I had a larger scope then that would be better.
F/ratio is only one variable for planetary observing, and far from the most important.

 

 

:waytogo:

 

When it comes to performance, aperture is the most important factor, it determines resolution and contrast transfer.  Focal ratio is a minor player.  

 

When it comes to the hassle factor and viewing comfort, focal length is the most important factor.  Aperture is of lesser importance.

 

These days high quality, fast mirrors that cool quickly are available.  Back when, the eyepieces that performed at F/4 and F/5 were not available, high quality fast mirrors were uncommon.  But this is 2016..

 

If one steps back, thinks in a different paradigm, fixed focal length instead of fixed aperture, then it's reasonably clear that a well made a 16 inch F/4 or a 12 inch F/5.3 will provide more detailed an contrastier planetary views than an 8 inch F/8.  There was a time when I owned four scopes, all with focal lengths between 48 inches and 51 inches:  The classic RV-6 at 6 inch F/8.3, an 8 inch F/6 Dob, my 10 inch F/5 Dob and the 12.5 inch F/4.06 Discovery.   

 

At the eyepiece, the 6 inch F/8 provided good views of the planets and double stars but the 12.5 inch F/4.06 showed more detail, more contrast, there was really no contest in which provides the better planetary views.. 

 

Two scopes to consider:

 

Jeff Morgan's 16 inch F/7 with a Zambuto mirror, my 16 inch F/4.42 with a mirror Mike Spooner refigured.  I am sure that Jeff's scope provides slightly/somewhat better planetary views than my scope, it has a smaller secondary and the longer focal ratio does add a small advantage.  

 

But Jeff's scope has a focal length of 112 inches and requires the same ladder I use with my 25 inch F/5.  My 16 inch is a flat foot scope, no ladder, it's an easy setup and still provides excellent views of the planets when the seeing supports it.  I used to haul it around in a Ford Escort station wagon.

 

So now, Jeff has been building a smaller, "No Ladder planetary scope."  I am not sure if it is an 8 inch or a 10 inch but I have to think that if he and I were to compare my no ladder 16 inch to his no ladder 8 or 10 inch, the 16 inch would provide the better views of the planets, split the closer doubles.. And then of course, there's the deep sky.. 

 

That's how I see it.  Aperture is my friend when it comes to providing the good planetary views, a long focal length, it's a hassle.  Don't start out thinking, "What is the best planetary scope with a 12 inch mirror?", think, "What is the best planetary scope with a 70 inch focal length?"

 

The answer you get depends on the question you ask.

 

Just sayin'

 

Jon Isaacs

 

I would love a 16" F/7 Zambuto. Be perfect for my seeing.



#15 MitchAlsup

MitchAlsup

    Skylab

  • -----
  • Posts: 4,164
  • Joined: 31 Aug 2009

Posted 29 April 2016 - 09:12 AM

But this is 2016..

 

If one steps back, thinks in a different paradigm, fixed focal length instead of fixed aperture, then it's reasonably clear that a well made a 16 inch F/4 or a 12 inch F/5.3 will provide more detailed an contrastier planetary views than an 8 inch F/8.  

 

Don't forget the 20" F/3.


  • Jon Isaacs likes this

#16 Yu Gu

Yu Gu

    Explorer 1

  • *****
  • Posts: 99
  • Joined: 18 Jun 2006

Posted 29 April 2016 - 10:17 AM

Assuming equivalent optical qualify and the following options of equal focal length:

1. a 6" F8

2. a 8" F6

3. a 10" F4.8

4. a 12" F4

5. a 16" F3

 

I would choose option 3 (the least spicy option) as my planetary scope. I've learned my lessons to not go extreme on either direction (I had a 16" F7.2 before...). Somewhere around F5 (IMHO) is the sweet spot for a high-resolution Newtonian if the optical quality is outstanding. 

Gu


  • Mr. Marbles, Sarkikos, Astrojensen and 1 other like this

#17 The Ardent

The Ardent

    Aurora

  • *****
  • Moderators
  • Posts: 4,679
  • Joined: 24 Oct 2008
  • Loc: Virginia

Posted 29 April 2016 - 12:56 PM

The primary makes the telescope , the secondary makes the planetary telescope.

Any pinching , curvature, or misalignment of the secondary will make the primary useless.



#18 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18,935
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 29 April 2016 - 05:50 PM

The primary makes the telescope , the secondary makes the planetary telescope.

Any pinching , curvature, or misalignment of the secondary will make the primary useless.

Mine must be pretty good in my 8" f/8.5 Cave. It was taking a barlowed 4.8mm Nag pretty good.


  • Galicapernistein likes this

#19 Jeff Morgan

Jeff Morgan

    Voyager 1

  • *****
  • Posts: 11,525
  • Joined: 28 Sep 2003
  • Loc: Prescott, AZ

Posted 30 April 2016 - 02:04 AM

 

 

 

My f/3.5 dob is the best planetary scope I have ever used. It's only part(the main part) of a system of planetary observing. Most of its avantage is aperture. If I had a larger scope then that would be better.
F/ratio is only one variable for planetary observing, and far from the most important.

 

 

:waytogo:

 

When it comes to performance, aperture is the most important factor, it determines resolution and contrast transfer.  Focal ratio is a minor player.  

 

When it comes to the hassle factor and viewing comfort, focal length is the most important factor.  Aperture is of lesser importance.

 

These days high quality, fast mirrors that cool quickly are available.  Back when, the eyepieces that performed at F/4 and F/5 were not available, high quality fast mirrors were uncommon.  But this is 2016..

 

If one steps back, thinks in a different paradigm, fixed focal length instead of fixed aperture, then it's reasonably clear that a well made a 16 inch F/4 or a 12 inch F/5.3 will provide more detailed an contrastier planetary views than an 8 inch F/8.  There was a time when I owned four scopes, all with focal lengths between 48 inches and 51 inches:  The classic RV-6 at 6 inch F/8.3, an 8 inch F/6 Dob, my 10 inch F/5 Dob and the 12.5 inch F/4.06 Discovery.   

 

At the eyepiece, the 6 inch F/8 provided good views of the planets and double stars but the 12.5 inch F/4.06 showed more detail, more contrast, there was really no contest in which provides the better planetary views.. 

 

Two scopes to consider:

 

Jeff Morgan's 16 inch F/7 with a Zambuto mirror, my 16 inch F/4.42 with a mirror Mike Spooner refigured.  I am sure that Jeff's scope provides slightly/somewhat better planetary views than my scope, it has a smaller secondary and the longer focal ratio does add a small advantage.  

 

But Jeff's scope has a focal length of 112 inches and requires the same ladder I use with my 25 inch F/5.  My 16 inch is a flat foot scope, no ladder, it's an easy setup and still provides excellent views of the planets when the seeing supports it.  I used to haul it around in a Ford Escort station wagon.

 

So now, Jeff has been building a smaller, "No Ladder planetary scope."  I am not sure if it is an 8 inch or a 10 inch but I have to think that if he and I were to compare my no ladder 16 inch to his no ladder 8 or 10 inch, the 16 inch would provide the better views of the planets, split the closer doubles.. And then of course, there's the deep sky.. 

 

That's how I see it.  Aperture is my friend when it comes to providing the good planetary views, a long focal length, it's a hassle.  Don't start out thinking, "What is the best planetary scope with a 12 inch mirror?", think, "What is the best planetary scope with a 70 inch focal length?"

 

The answer you get depends on the question you ask.

 

Just sayin'

 

Jon Isaacs

 

 

 

Regarding the purpose of my 8” build - it is not to compete with larger scopes (mine or anyone else). The point of that project is to build a scope that is easy to deploy and fast to cool for those “spur of the moment” opportunities. Or, just nights when I don’t have the energy to pull out a large scope.

 

The 8” mirror weighs 3 pounds, vs. 25 pounds of glass for a 16” mirror. And then there is the weight of the scope that houses the mirror: No contest - the 8” wins handily for the purpose it was built.

 

But when you optimize for convenience, there are performance trade-offs.

 

You mention me prominently as if my opinion, preference, or assertions make the long focus Newtonian a great planetary scope. The reality is that History’s long list of famous planetary observers have determined that. They had a choice, and it was not the one you advocate.

 

Perhaps they just weren’t smart enough .....


  • Galicapernistein, Sasa and Bomber Bob like this

#20 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 81,829
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 30 April 2016 - 03:12 AM

 

 

You mention me prominently as if my opinion, preference, or assertions make the long focus Newtonian a great planetary scope. The reality is that History’s long list of famous planetary observers have determined that. They had a choice, and it was not the one you advocate.

Perhaps they just weren’t smart enough .....

 

Jeff:

 

Did the astronomers of yore have access to large aperture, high quality, fast focal ratio mirrors, figured and tested with an interferometer?  Did they have access to the high quality, multi element, multi secton eyepieces with the modern coatings that are well corrected at fast focal ratios, did they have access to coma correctors?  Did they have portable designs so a large aperture scope was practical?

 

I think not.

 

The astronomers of yore also used thick mirrors in crude cells, equatorial mounts, tube scopes, uncoated eyepieces, crude focusers... Are you promoting these because that's how they did it back when?

 

They were plenty smart... They made their decisions based what was available at the time.  

 

Times have changed, we can learn from the past but we live in a different world with different choices. 

 

The reason I mention you prominently is because I am well aware that you and I approach this question in very different ways. It doesn't make sense to me climb a ladder to view through a 16 inch F/7 scope when I could be getting very similar views in a 16 inch F/4.5 scope or as Mitch might say, better views in a 20 inch F/3.5... 

 

Jon Isaacs


  • Sarkikos, dave brock, Astrojensen and 1 other like this

#21 otocycle

otocycle

    Apollo

  • *****
  • Posts: 1,176
  • Joined: 08 Jun 2005

Posted 30 April 2016 - 03:31 AM

I built a 10" f/8 planetary Newtonian specifically for the very favorable 2003 Mars opposition.   Custom Royce mirror, small Protostar diagonal, flocking, DAR mirror cell, JMI focuser, etc.    It was built to do one thing and it did not disappoint, although I did abuse several mounts with it.

 

 

10_Inch_DobEQ.JPG


  • Astrojensen, ATM57, Sasa and 2 others like this

#22 Bomber Bob

Bomber Bob

    Hubble

  • *****
  • Posts: 16,373
  • Joined: 09 Jul 2013
  • Loc: The Swamp, USA

Posted 30 April 2016 - 06:46 AM

I look forward to testing my 12" f/5 Orion Dob on lunar & planetary, and comparing its views with my 6" f/20 Tinsley Cassegrain - twice the aperture & half the focal length vice half the aperture & twice the focal length.  I didn't plan it that way, but I do like the way it worked out.  The Tinsley already outdoes my Edmund 4" f/15 refractor - more detail than I can sketch.  My last "light bucket" was an 8" rich field that I made 30+ years ago that was definitely not a planet killer.



#23 Galicapernistein

Galicapernistein

    Viking 1

  • *****
  • Posts: 575
  • Joined: 24 Sep 2007

Posted 30 April 2016 - 09:50 AM

For the record, deep sky objects DO look better in a slow reflector. Field distortions are reduced, and there is no need to introduce expensive field correctors with even more layers of glass. Additionally, the larger depth of focus makes the scope more comfortable to use over long periods of time, like watching Jupiter for an hour waiting for moments of good seeing. Of course a larger, heavier and more expensive scope will provide better views, but the advantages of a small, optimized scope are obvious to anyone who has had to haul a large dob to a dark sky sight. 


  • CollinofAlabama and KerryInSpace like this

#24 Jeff Morgan

Jeff Morgan

    Voyager 1

  • *****
  • Posts: 11,525
  • Joined: 28 Sep 2003
  • Loc: Prescott, AZ

Posted 30 April 2016 - 11:08 AM

 

 

 

You mention me prominently as if my opinion, preference, or assertions make the long focus Newtonian a great planetary scope. The reality is that History’s long list of famous planetary observers have determined that. They had a choice, and it was not the one you advocate.

Perhaps they just weren’t smart enough .....

 

Jeff:

 

Did the astronomers of yore have access to large aperture, high quality, fast focal ratio mirrors, figured and tested with an interferometer?  Did they have access to the high quality, multi element, multi secton eyepieces with the modern coatings that are well corrected at fast focal ratios, did they have access to coma correctors?  Did they have portable designs so a large aperture scope was practical?

 

I think not.

 

 

I get your desire to skip the ladder, both of us own such scopes.

 

But unlike most of us who can be satisfied with casual observing with whatever scope we have at hand, the famous astronomers of yesteryear would have been highly interested in optimizing their equipment, and not deterred from their passion by a minor inconvenience like a ladder.

 

The question you raise is when would they have been able to utilize your "Super-Newt"?

 

- Focault test, invented 1858. Many other sensitive tests followed soon after. Steep aspheres know as Cassegrains contemporary with the Newtonian, but the Focault test was what made accuracy testing and reliable production of quality figures possible.

 

-  Eyepiece coatings are irrelevant for planetary observing, else there would have been no planetary observing prior to the use of MgFl. But if you insist Lord Rayliegh discovered AR coatings in 1886.

 

- All paraboloids are perfect on axis. Therefore off-axis corrections irrelevant for planetary observing. Scatter is very relevant. True planetary eyepieces invented 1860 (Plossl) or 1880 (Abbe Ortho). According to one eyepiece manufacturer, Plossls are tested down to f/4.

 

- The first clock drive (which allows one to hold the planet in the sweet spot of your super-Newt and thus utilize true planetary designs) was the Dorpat Refractor. The year was 1824.

 

- The coma corrector is irrelevant if you can hold the target centered. But just to humor you, the coma corrector dates back to at least 1935 (the Ross corrector on the Palomar telescope).

 

- Planetary observing does not require travel to dark skies. It could be done from your back yard. It could be done from under a street light. It could be done from downtown Los Angeles. Indeed, for the optimized planetary telescope the best scenario is a fixed installation. Portability is irrelevant.

 

Any more Red Herrings?

 

All the pieces have been there for 80 years. Or possibly 150+ years if you skip the coma corrector.

 

Getting back to History's famous and pioneering planetary observers and their equipment choices ...... apparently none of those Dummies were able to put all the pieces together.


Edited by Jeff Morgan, 30 April 2016 - 11:18 AM.

  • mark cowan and Terra Nova like this

#25 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 81,829
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 30 April 2016 - 11:28 AM

 

But unlike most of us who can be satisfied with casual observing with whatever scope we have at hand, the famous astronomers of yesteryear would have been highly interested in optimizing their equipment, and not deterred from their passion by a minor inconvenience like a ladder.

 

They did optimize their equipment just as we do.  Today we have much better materials, manufacturing and testing protocols, we can take advantage of them if we want.

 

But I disagree that the tools were in place to build high quality fast mirrors.  Large thin blanks of Pyrex were not available, modern coating methods were not available, modern testing methods were not available.  

 

Progress is a step by step process, technologies develop. 

 

You embrace a lot of the modern technologies, thin mirrors, high quality focusers, electronic drives, the dobsonian mount.  These also are part of the technological progress that make large aperture Newtonians practical for the modern amateur...   Back when, how many were using 16 inch mirrors in their equatorial mounts?  

 

I suggest that if the astronomers amateur 75 years ago had access to a 32inch F/3 with a Lockwood mirror and electronic drives, they would have been thrilled and used it for every possible thing.

 

Jon




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: reflector



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics