Topics

End of an era?


Roland Christen
 

Hi Astronuts,

Today I finished the last of the 10" F14.5 Maks, which will go to whoever is on our list. This is the last of my hand figured Maks that I plan to make of this size and focal length in production. It used to be that there was much more visual astronomy than there is today, probably because imaging was hard in the film days and for the first couple of years when we had small chips to do electronic imaging. Nowadays it is impossible to get visual views that remotely resemble what you can do with a few thousand bucks worth of electronic equipment.

That said, here is my last production Mak, aimed at a far distant telephone pole insulator which has a glint of sunshine that shows up as an artificial star. With a 5mm SPL ocular (737x) I see a tight high contrast Airy disc at focus. For those who don't know what that is - an Airy disc is the smallest resolvable spot from a distant point source that can be seen in any telescope. For a 10" it's approximately 4.5 arc seconds, and is surrounded by a few faint diffraction rings. With a scope like this I once saw the Sirius Pup in the Florida Keys when the separation was a mere 4 arc seconds.

Business end of the mighty Mak


Let there be light and minimal obstruction


The little Stowaway couldn't help hitching a ride on it's big sister


Pete Lardizabal
 

WOW! Simply beautiful!

More rare than hens teeth...

😎

Pete

On Jul 31, 2020, at 6:17 PM, Roland Christen via groups.io <chris1011@...> wrote:


Hi Astronuts,

Today I finished the last of the 10" F14.5 Maks, which will go to whoever is on our list. This is the last of my hand figured Maks that I plan to make of this size and focal length in production. It used to be that there was much more visual astronomy than there is today, probably because imaging was hard in the film days and for the first couple of years when we had small chips to do electronic imaging. Nowadays it is impossible to get visual views that remotely resemble what you can do with a few thousand bucks worth of electronic equipment.

That said, here is my last production Mak, aimed at a far distant telephone pole insulator which has a glint of sunshine that shows up as an artificial star. With a 5mm SPL ocular (737x) I see a tight high contrast Airy disc at focus. For those who don't know what that is - an Airy disc is the smallest resolvable spot from a distant point source that can be seen in any telescope. For a 10" it's approximately 4.5 arc seconds, and is surrounded by a few faint diffraction rings. With a scope like this I once saw the Sirius Pup in the Florida Keys when the separation was a mere 4 arc seconds.

<dummyfile.0.part>
Business end of the mighty Mak


<dummyfile.1.part>
Let there be light and minimal obstruction


<dummyfile.2.part>
The little Stowaway couldn't help hitching a ride on it's big sister


Stewart Valentine
 

Wish that was me. Alas it is not...............

On Fri, Jul 31, 2020 at 4:32 PM Pete Lardizabal <p14@...> wrote:
WOW! Simply beautiful!

More rare than hens teeth...

😎

Pete

On Jul 31, 2020, at 6:17 PM, Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:


Hi Astronuts,

Today I finished the last of the 10" F14.5 Maks, which will go to whoever is on our list. This is the last of my hand figured Maks that I plan to make of this size and focal length in production. It used to be that there was much more visual astronomy than there is today, probably because imaging was hard in the film days and for the first couple of years when we had small chips to do electronic imaging. Nowadays it is impossible to get visual views that remotely resemble what you can do with a few thousand bucks worth of electronic equipment.

That said, here is my last production Mak, aimed at a far distant telephone pole insulator which has a glint of sunshine that shows up as an artificial star. With a 5mm SPL ocular (737x) I see a tight high contrast Airy disc at focus. For those who don't know what that is - an Airy disc is the smallest resolvable spot from a distant point source that can be seen in any telescope. For a 10" it's approximately 4.5 arc seconds, and is surrounded by a few faint diffraction rings. With a scope like this I once saw the Sirius Pup in the Florida Keys when the separation was a mere 4 arc seconds.

<dummyfile.0.part>
Business end of the mighty Mak


<dummyfile.1.part>
Let there be light and minimal obstruction


<dummyfile.2.part>
The little Stowaway couldn't help hitching a ride on it's big sister


Alan Friedman
 

Bravo Rolando and congratulations on this milestone. This scope will join its sisters and continue to dazzle stargazers around the world for years to come.

Alan




On Jul 31, 2020, at 3:16 PM, Roland Christen via groups.io <chris1011@...> wrote:


Hi Astronuts,

Today I finished the last of the 10" F14.5 Maks, which will go to whoever is on our list. This is the last of my hand figured Maks that I plan to make of this size and focal length in production. It used to be that there was much more visual astronomy than there is today, probably because imaging was hard in the film days and for the first couple of years when we had small chips to do electronic imaging. Nowadays it is impossible to get visual views that remotely resemble what you can do with a few thousand bucks worth of electronic equipment.

That said, here is my last production Mak, aimed at a far distant telephone pole insulator which has a glint of sunshine that shows up as an artificial star. With a 5mm SPL ocular (737x) I see a tight high contrast Airy disc at focus. For those who don't know what that is - an Airy disc is the smallest resolvable spot from a distant point source that can be seen in any telescope. For a 10" it's approximately 4.5 arc seconds, and is surrounded by a few faint diffraction rings. With a scope like this I once saw the Sirius Pup in the Florida Keys when the separation was a mere 4 arc seconds.

<dummyfile.0.part>
Business end of the mighty Mak


<dummyfile.1.part>
Let there be light and minimal obstruction


<dummyfile.2.part>
The little Stowaway couldn't help hitching a ride on it's big sister


Alan
 

Roland,

The Mak and the little Stowaway, what a sweet combination!

Clear skies, Alan

On 7/31/2020 6:16 PM, Roland Christen via groups.io wrote:
Hi Astronuts,

Today I finished the last of the 10" F14.5 Maks, which will go to whoever is on our list. This is the last of my hand figured Maks that I plan to make of this size and focal length in production. It used to be that there was much more visual astronomy than there is today, probably because imaging was hard in the film days and for the first couple of years when we had small chips to do electronic imaging. Nowadays it is impossible to get visual views that remotely resemble what you can do with a few thousand bucks worth of electronic equipment.

That said, here is my last production Mak, aimed at a far distant telephone pole insulator which has a glint of sunshine that shows up as an artificial star. With a 5mm SPL ocular (737x) I see a tight high contrast Airy disc at focus. For those who don't know what that is - an Airy disc is the smallest resolvable spot from a distant point source that can be seen in any telescope. For a 10" it's approximately 4.5 arc seconds, and is surrounded by a few faint diffraction rings. With a scope like this I once saw the Sirius Pup in the Florida Keys when the separation was a mere 4 arc seconds.

Business end of the mighty Mak


Let there be light and minimal obstruction


The little Stowaway couldn't help hitching a ride on it's big sister


Jay Freeman
 

Roland wrote ...

It used to be that there was much more visual astronomy than there is today, probably because imaging was hard in the film days and for the first couple of years when we had small chips to do electronic imaging. Nowadays it is impossible to get visual views that remotely resemble what you can do with a few thousand bucks worth of electronic equipment. 

All true about the quality of electronically obtained images, but there is another side to the coin: I have had a fairly high-tech career -- PhD in physics, tail end of the Apollo program, a couple of artificial intelligence labs, Sun Microsystems Lab, and SpaceX -- even a little image processing, for that matter. Rather early on, I made a conscience decision to keep my hobbies low-tech, for diversity and for better relaxation. Thus I have deliberately avoided anything resembling imaging -- my astronomy, at least as an amateur, has always been strictly visual. Surely there are others who think the way I do?

Now that I have retired, I have added a little technology into the mix: Besides visual astronomy, cats, roses and guitar playing, I have been building a few guitar amplifiers. But the vacuum-tube stuff involved is so old that it is basically steampunk, so I'm not sure it counts ...

BTW, Roland, what are you using for an eyepiece turret on that AP-10?

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


Terri Zittritsch
 

Roland, in reading your post, it seemed like you have concluded that production of these beautiful scopes is no longer warranted due to the accessibility of imaging.    When I first decided to invest in some astro Physics equipment, the first thing you notice is that almost nothing is available to buy, and/or even available for backorder (getting on a list).     Did you see a real drop in people wanting to get on the list for the 10", and therefore some time ago stopped accepting new back orders?    

I know that while I love refractors for their pinpoint stars, my next favorite scopes are the folded light class... you get such a huge bang for the buck in a portable package!    At outreach events here in Vermont, I frequently hear that I have the best views through my little 8" Meade ACF, and while the general public may not know all of what to look for, I find the images pleasing as well.   I guess if I want one of your beauties, I'll have to watch on the second hand market now.

Terri


Roland Christen
 

That is one made by Telescope Engineering Company.

Rolando



-----Original Message-----
From: Jay Freeman via groups.io <Jay_Reynolds_Freeman@...>
To: main@ap-ug.groups.io
Sent: Fri, Jul 31, 2020 5:59 pm
Subject: Re: [ap-ug] End of an era?

Roland wrote ...

It used to be that there was much more visual astronomy than there is today, probably because imaging was hard in the film days and for the first couple of years when we had small chips to do electronic imaging. Nowadays it is impossible to get visual views that remotely resemble what you can do with a few thousand bucks worth of electronic equipment. 

All true about the quality of electronically obtained images, but there is another side to the coin: I have had a fairly high-tech career -- PhD in physics, tail end of the Apollo program, a couple of artificial intelligence labs, Sun Microsystems Lab, and SpaceX -- even a little image processing, for that matter. Rather early on, I made a conscience decision to keep my hobbies low-tech, for diversity and for better relaxation. Thus I have deliberately avoided anything resembling imaging -- my astronomy, at least as an amateur, has always been strictly visual. Surely there are others who think the way I do?

Now that I have retired, I have added a little technology into the mix: Besides visual astronomy, cats, roses and guitar playing, I have been building a few guitar amplifiers. But the vacuum-tube stuff involved is so old that it is basically steampunk, so I'm not sure it counts ...

BTW, Roland, what are you using for an eyepiece turret on that AP-10?

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


Roland Christen
 

First, there are tons of SCTs coming from China now that it is impractical to make a hand figured folded optic. People call them superb although tests show consistently that they are barely 1/4 wave. I have never seen a truly superb one. However, even at just 1/4 wave, they are capable of making truly great digital images using "Lucky Imaging" techniques, with video cameras, where resolution is high and contrast can be boosted to show fleeting detail. You can get a 14" scope for the price of a hand figured 6" Mak.

The Maksutov Cassegrain optical system has an inherent 5th order spherical defect that requires hand correction. They can be made cheaply if you allow all surfaces to be spherical and have a largish central obstruction and allow 1/3 to 1/4 wave of spherical error. The smaller the obstruction is, the worse the 5th order becomes. Doing hand correcting on the 10" mirror of our Maks takes 5 to 15 hours of careful hand work. Figuring cycle can be as little as 15 seconds at a time, followed by 10 - 15 minutes of testing on the interferometer. There are very few people who have the patience and knowledge to do this task.

Getting the correction down to the level of 1/10 wave P-V is not trivial, but results in superb contrast visually. The eyeball cannot artificially turn up the contrast, and if the optic is corrected to only 1/3 - 1/4 wave, the contrast drops in half. Add to that a large central obstruction and the contrast drops even more.

The requirement for a superb visual instrument is different than for an imaging instrument. Superb visual scopes require a higher level of correction. Most of that knowledge is lost now that electronic imaging is so advanced. The cost in time, knowledge and treasure is high.

Rolando



-----Original Message-----
From: Terri Zittritsch <theresamarie11@...>
To: main@ap-ug.groups.io
Sent: Sat, Aug 1, 2020 7:54 am
Subject: Re: [ap-ug] End of an era?

Roland, in reading your post, it seemed like you have concluded that production of these beautiful scopes is no longer warranted due to the accessibility of imaging.    When I first decided to invest in some astro Physics equipment, the first thing you notice is that almost nothing is available to buy, and/or even available for backorder (getting on a list).     Did you see a real drop in people wanting to get on the list for the 10", and therefore some time ago stopped accepting new back orders?    

I know that while I love refractors for their pinpoint stars, my next favorite scopes are the folded light class... you get such a huge bang for the buck in a portable package!    At outreach events here in Vermont, I frequently hear that I have the best views through my little 8" Meade ACF, and while the general public may not know all of what to look for, I find the images pleasing as well.   I guess if I want one of your beauties, I'll have to watch on the second hand market now.

Terri


Harley Davidson
 

Thanks for that Roland. Very interesting information. Would never guess it took that many hours of hand figuring.

tony

On 8/1/2020 10:59 AM, Roland Christen via groups.io wrote:
First, there are tons of SCTs coming from China now that it is impractical to make a hand figured folded optic. People call them superb although tests show consistently that they are barely 1/4 wave. I have never seen a truly superb one. However, even at just 1/4 wave, they are capable of making truly great digital images using "Lucky Imaging" techniques, with video cameras, where resolution is high and contrast can be boosted to show fleeting detail. You can get a 14" scope for the price of a hand figured 6" Mak.

The Maksutov Cassegrain optical system has an inherent 5th order spherical defect that requires hand correction. They can be made cheaply if you allow all surfaces to be spherical and have a largish central obstruction and allow 1/3 to 1/4 wave of spherical error. The smaller the obstruction is, the worse the 5th order becomes. Doing hand correcting on the 10" mirror of our Maks takes 5 to 15 hours of careful hand work. Figuring cycle can be as little as 15 seconds at a time, followed by 10 - 15 minutes of testing on the interferometer. There are very few people who have the patience and knowledge to do this task.

Getting the correction down to the level of 1/10 wave P-V is not trivial, but results in superb contrast visually. The eyeball cannot artificially turn up the contrast, and if the optic is corrected to only 1/3 - 1/4 wave, the contrast drops in half. Add to that a large central obstruction and the contrast drops even more.

The requirement for a superb visual instrument is different than for an imaging instrument. Superb visual scopes require a higher level of correction. Most of that knowledge is lost now that electronic imaging is so advanced. The cost in time, knowledge and treasure is high.

Rolando



-----Original Message-----
From: Terri Zittritsch <theresamarie11@...>
To: main@ap-ug.groups.io
Sent: Sat, Aug 1, 2020 7:54 am
Subject: Re: [ap-ug] End of an era?

Roland, in reading your post, it seemed like you have concluded that production of these beautiful scopes is no longer warranted due to the accessibility of imaging.    When I first decided to invest in some astro Physics equipment, the first thing you notice is that almost nothing is available to buy, and/or even available for backorder (getting on a list).     Did you see a real drop in people wanting to get on the list for the 10", and therefore some time ago stopped accepting new back orders?    

I know that while I love refractors for their pinpoint stars, my next favorite scopes are the folded light class... you get such a huge bang for the buck in a portable package!    At outreach events here in Vermont, I frequently hear that I have the best views through my little 8" Meade ACF, and while the general public may not know all of what to look for, I find the images pleasing as well.   I guess if I want one of your beauties, I'll have to watch on the second hand market now.

Terri


Roland Christen
 

Yes, for this particular design that's what it takes just to do the final step. That does not count the grinding and polishing of the mirror surface along with the front corrector lens. The corrector lens of course has two spherical surfaces, but they must be carefully polished to match their test plates to 1/10 wave also.

For this last production run we used a carbon fiber tube which reduces weight and makes the focus point more stable. That, and the use of a fused quartz mirror, also increases the cost but allows the optic to remain at a high performance level during changing temperatures.

Rolando

-----Original Message-----
From: Harley Davidson <astrocnc@...>
To: main@ap-ug.groups.io
Sent: Sat, Aug 1, 2020 11:02 am
Subject: Re: [ap-ug] End of an era?

Thanks for that Roland. Very interesting information. Would never guess it took that many hours of hand figuring.

tony

On 8/1/2020 10:59 AM, Roland Christen via groups.io wrote:
First, there are tons of SCTs coming from China now that it is impractical to make a hand figured folded optic. People call them superb although tests show consistently that they are barely 1/4 wave. I have never seen a truly superb one. However, even at just 1/4 wave, they are capable of making truly great digital images using "Lucky Imaging" techniques, with video cameras, where resolution is high and contrast can be boosted to show fleeting detail. You can get a 14" scope for the price of a hand figured 6" Mak.

The Maksutov Cassegrain optical system has an inherent 5th order spherical defect that requires hand correction. They can be made cheaply if you allow all surfaces to be spherical and have a largish central obstruction and allow 1/3 to 1/4 wave of spherical error. The smaller the obstruction is, the worse the 5th order becomes. Doing hand correcting on the 10" mirror of our Maks takes 5 to 15 hours of careful hand work. Figuring cycle can be as little as 15 seconds at a time, followed by 10 - 15 minutes of testing on the interferometer. There are very few people who have the patience and knowledge to do this task.

Getting the correction down to the level of 1/10 wave P-V is not trivial, but results in superb contrast visually. The eyeball cannot artificially turn up the contrast, and if the optic is corrected to only 1/3 - 1/4 wave, the contrast drops in half. Add to that a large central obstruction and the contrast drops even more.

The requirement for a superb visual instrument is different than for an imaging instrument. Superb visual scopes require a higher level of correction. Most of that knowledge is lost now that electronic imaging is so advanced. The cost in time, knowledge and treasure is high.

Rolando



-----Original Message-----
From: Terri Zittritsch <theresamarie11@...>
To: main@ap-ug.groups.io
Sent: Sat, Aug 1, 2020 7:54 am
Subject: Re: [ap-ug] End of an era?

Roland, in reading your post, it seemed like you have concluded that production of these beautiful scopes is no longer warranted due to the accessibility of imaging.    When I first decided to invest in some astro Physics equipment, the first thing you notice is that almost nothing is available to buy, and/or even available for backorder (getting on a list).     Did you see a real drop in people wanting to get on the list for the 10", and therefore some time ago stopped accepting new back orders?    

I know that while I love refractors for their pinpoint stars, my next favorite scopes are the folded light class... you get such a huge bang for the buck in a portable package!    At outreach events here in Vermont, I frequently hear that I have the best views through my little 8" Meade ACF, and while the general public may not know all of what to look for, I find the images pleasing as well.   I guess if I want one of your beauties, I'll have to watch on the second hand market now.

Terri


Pete Lardizabal
 

Roland,

I so enjoy these discussions giving us a peak of some of the effort behind these marvelous works. I’m always torn whether or not to view with an eyepiece or capture images with the DSLR. Birds, planets, star fields and dare I say the ISS are so enjoyable to view with my AP refractors. 

😎

Pete

On Aug 1, 2020, at 12:16 PM, Roland Christen via groups.io <chris1011@...> wrote:


Yes, for this particular design that's what it takes just to do the final step. That does not count the grinding and polishing of the mirror surface along with the front corrector lens. The corrector lens of course has two spherical surfaces, but they must be carefully polished to match their test plates to 1/10 wave also.

For this last production run we used a carbon fiber tube which reduces weight and makes the focus point more stable. That, and the use of a fused quartz mirror, also increases the cost but allows the optic to remain at a high performance level during changing temperatures.

Rolando

-----Original Message-----
From: Harley Davidson <astrocnc@...>
To: main@ap-ug.groups.io
Sent: Sat, Aug 1, 2020 11:02 am
Subject: Re: [ap-ug] End of an era?

Thanks for that Roland. Very interesting information. Would never guess it took that many hours of hand figuring.

tony

On 8/1/2020 10:59 AM, Roland Christen via groups.io wrote:
First, there are tons of SCTs coming from China now that it is impractical to make a hand figured folded optic. People call them superb although tests show consistently that they are barely 1/4 wave. I have never seen a truly superb one. However, even at just 1/4 wave, they are capable of making truly great digital images using "Lucky Imaging" techniques, with video cameras, where resolution is high and contrast can be boosted to show fleeting detail. You can get a 14" scope for the price of a hand figured 6" Mak.

The Maksutov Cassegrain optical system has an inherent 5th order spherical defect that requires hand correction. They can be made cheaply if you allow all surfaces to be spherical and have a largish central obstruction and allow 1/3 to 1/4 wave of spherical error. The smaller the obstruction is, the worse the 5th order becomes. Doing hand correcting on the 10" mirror of our Maks takes 5 to 15 hours of careful hand work. Figuring cycle can be as little as 15 seconds at a time, followed by 10 - 15 minutes of testing on the interferometer. There are very few people who have the patience and knowledge to do this task.

Getting the correction down to the level of 1/10 wave P-V is not trivial, but results in superb contrast visually. The eyeball cannot artificially turn up the contrast, and if the optic is corrected to only 1/3 - 1/4 wave, the contrast drops in half. Add to that a large central obstruction and the contrast drops even more.

The requirement for a superb visual instrument is different than for an imaging instrument. Superb visual scopes require a higher level of correction. Most of that knowledge is lost now that electronic imaging is so advanced. The cost in time, knowledge and treasure is high.

Rolando



-----Original Message-----
From: Terri Zittritsch <theresamarie11@...>
To: main@ap-ug.groups.io
Sent: Sat, Aug 1, 2020 7:54 am
Subject: Re: [ap-ug] End of an era?

Roland, in reading your post, it seemed like you have concluded that production of these beautiful scopes is no longer warranted due to the accessibility of imaging.    When I first decided to invest in some astro Physics equipment, the first thing you notice is that almost nothing is available to buy, and/or even available for backorder (getting on a list).     Did you see a real drop in people wanting to get on the list for the 10", and therefore some time ago stopped accepting new back orders?    

I know that while I love refractors for their pinpoint stars, my next favorite scopes are the folded light class... you get such a huge bang for the buck in a portable package!    At outreach events here in Vermont, I frequently hear that I have the best views through my little 8" Meade ACF, and while the general public may not know all of what to look for, I find the images pleasing as well.   I guess if I want one of your beauties, I'll have to watch on the second hand market now.

Terri


myrussellm
 

Roland

Congratulations the fortunate owner will enjoy for many years.

There is nothing to beat visual observing as it is capturing the moment for your delight and later memory. I recall the most awe inspiring moment was a Solar eclipse at the space launch facility in the China desert. Hundreds of chattering people but when totality occurred there was not a sound even the wind died. You cannot capture those moments digitally.

Still love good seeing through my AP130 and AP178 although it takes a little longer to brave the cool nights.

Cheers

Mike


Chet Myslinski <leavmys@...>
 

I think there is an exception to " nowadays it is impossible to get visual views that remotely resemble ..."  Visual observing of the moon can equal and usually exceed  imaging - in my experience.


Scott Mortimer
 

>>Thus I have deliberately avoided anything resembling imaging -- my astronomy, at least as an amateur, has always been strictly visual. Surely there are others who think the way I do?

yes Jay, amen, you're describing me as well.  After many years working in IT the last thing I want to do in my free time is get behind another LCD screen and keyboard.  Roaming the cosmos with my 6" refractor is another way of experiencing the beauty of the natural world, like hiking through wilderness.  The image quality of the apo is the closest to peering out the window of a spaceship. 

I prefer paper charts and leave my computer at home.   Seeking out the best observing locations brings me to the more wild, remote places as well.  Maybe visual observing is more of a visceral thrill-of-the-moment versus the satisfaction of building something. 

Visual observing still seems popular, maybe it's just my club but I see most people starting off with dobsonians or alt-az mounted refractors.   It's interesting that apo refractors have become so dominant vs. high-end Maks, maybe it's the low-power RFT abilities of apos that people like?   A 7" apo is about the same weight as a 10" Mak.  Difficult choice!  the apo gives up some aperture but excels at wide-field views in addition to high power.

-Scott


Terri Zittritsch
 

On Sat, Aug 1, 2020 at 10:59 AM, Roland Christen wrote:
First, there are tons of SCTs coming from China now that it is impractical to make a hand figured folded optic. People call them superb although tests show consistently that they are barely 1/4 wave. I have never seen a truly superb one. However, even at just 1/4 wave, they are capable of making truly great digital images using "Lucky Imaging" techniques, with video cameras, where resolution is high and contrast can be boosted to show fleeting detail. You can get a 14" scope for the price of a hand figured 6" Mak.
 
The Maksutov Cassegrain optical system has an inherent 5th order spherical defect that requires hand correction. They can be made cheaply if you allow all surfaces to be spherical and have a largish central obstruction and allow 1/3 to 1/4 wave of spherical error. The smaller the obstruction is, the worse the 5th order becomes. Doing hand correcting on the 10" mirror of our Maks takes 5 to 15 hours of careful hand work. Figuring cycle can be as little as 15 seconds at a time, followed by 10 - 15 minutes of testing on the interferometer. There are very few people who have the patience and knowledge to do this task.
 
Getting the correction down to the level of 1/10 wave P-V is not trivial, but results in superb contrast visually. The eyeball cannot artificially turn up the contrast, and if the optic is corrected to only 1/3 - 1/4 wave, the contrast drops in half. Add to that a large central obstruction and the contrast drops even more.
 
The requirement for a superb visual instrument is different than for an imaging instrument. Superb visual scopes require a higher level of correction. Most of that knowledge is lost now that electronic imaging is so advanced. The cost in time, knowledge and treasure is high.
 
Rolando

Hi Rolando,
I think there is still a large contingent of amateur astronomers who are visual-only and have no interest in going 'electronic'.   Most of the visual-only observers in our club are very much 'minimalists'.    They'll typically use a big dob (big is relative of course).  The Mak is a pretty specialized telescope, at F12-F15, typically for planets, double stars (I think).    I had a 6" Mak some years ago and ended up selling it.      I think there will always be a market for the kind of quality you deliver, and I think you see it from your long waiting lists for your refractors, when there are lots of other cheaper choices out there.  Has A-P ever considered making an SCT, a more general purpose folded light telescope?

Terri

 


Zubair Khan
 

Excuse my ignorance but I’m wondering what the difference in that telescope vs. my Celestron Evolution 9.25 SCT (https://www.celestron.com/products/nexstar-evolution-925-telescope) is. I can get some pretty amazing views through it. Am I missing out on something even better?

- Zubair

On Aug 2, 2020, at 6:07 PM, Terri Zittritsch <theresamarie11@...> wrote:

On Sat, Aug 1, 2020 at 10:59 AM, Roland Christen wrote:
First, there are tons of SCTs coming from China now that it is impractical to make a hand figured folded optic. People call them superb although tests show consistently that they are barely 1/4 wave. I have never seen a truly superb one. However, even at just 1/4 wave, they are capable of making truly great digital images using "Lucky Imaging" techniques, with video cameras, where resolution is high and contrast can be boosted to show fleeting detail. You can get a 14" scope for the price of a hand figured 6" Mak.
 
The Maksutov Cassegrain optical system has an inherent 5th order spherical defect that requires hand correction. They can be made cheaply if you allow all surfaces to be spherical and have a largish central obstruction and allow 1/3 to 1/4 wave of spherical error. The smaller the obstruction is, the worse the 5th order becomes. Doing hand correcting on the 10" mirror of our Maks takes 5 to 15 hours of careful hand work. Figuring cycle can be as little as 15 seconds at a time, followed by 10 - 15 minutes of testing on the interferometer. There are very few people who have the patience and knowledge to do this task.
 
Getting the correction down to the level of 1/10 wave P-V is not trivial, but results in superb contrast visually. The eyeball cannot artificially turn up the contrast, and if the optic is corrected to only 1/3 - 1/4 wave, the contrast drops in half. Add to that a large central obstruction and the contrast drops even more.
 
The requirement for a superb visual instrument is different than for an imaging instrument. Superb visual scopes require a higher level of correction. Most of that knowledge is lost now that electronic imaging is so advanced. The cost in time, knowledge and treasure is high.
 
Rolando

Hi Rolando,
I think there is still a large contingent of amateur astronomers who are visual-only and have no interest in going 'electronic'.   Most of the visual-only observers in our club are very much 'minimalists'.    They'll typically use a big dob (big is relative of course).  The Mak is a pretty specialized telescope, at F12-F15, typically for planets, double stars (I think).    I had a 6" Mak some years ago and ended up selling it.      I think there will always be a market for the kind of quality you deliver, and I think you see it from your long waiting lists for your refractors, when there are lots of other cheaper choices out there.  Has A-P ever considered making an SCT, a more general purpose folded light telescope?

Terri

 


Frank Crowder
 

I have never posted, but I enjoy reading everyone’s adventures.

I would like to add my voice to the visual advocates. There are many things that provided me moments of joy. I will never forget the first time that I looked at Saturn using my Stowaway and a 6mm Brandon. The sharpness of the bands was inspiring. The first glimpse of the Orion Nebula in the winter, m81, Jupiter, are obviously others.

I have tried astrophotography and find that I do not have the partience to spend 20 hours on a single photo, Maybe this will change when I retiree. To those of you that have mastered the craft, I admire you and enjoy the things that you share here. However, I will always enjoy the instant gratification provided by my gtx and “grab and go”stowaway.

Thanks to everyone at AP.

Frank Crowder


Elenillor
 

Zubair,
 

I will take a stab at trying to explain the difference in views between the Mak-Cass and the standard Schmidt-Cass. Simply my observations with no attempt to justify it or explain why with MTF curves and other technical reasons. 

 

What one prefers and values at the eyepiece is subjective. Some like low wide fields, some like faint objects, others like high resolution ... .

 

At star parties most people remark, unprompted, how they like the bright clear views through my AP130 vs the standard Schmidt-Cass or Newtonian scopes that are setup nearby. No doubt some of it is do to the fact the AP130 looks like what a telescope "should be' but the other part is the 'clarity' of the view even if the absolute resolution is not as great as in the other scopes. That is why 'refractor like' as a common qualitative term for 'clean crisp' views.

 

The Mak-Cass presents 'refractor like' views, none of the Schmidt-Cass scopes I have observed with have. Not to say I have not had great views though many when well aligned and cooled down. Sorry to say at star parties more often than not those two conditions are not met.

 

I tend to think of 'refractor like' as having high "dynamic range" to miss-use a camera sensor term. That is the ability to clearly see the subtle shading on Saturn and Mars.  High contrast would be the ball of Saturn against the black sky or seeing the Cassini division as a dark line. "Dynamic range" shows up as seeing the subtle small scale shading all over the surface of the moon and lots of faint pinpricks of light in star fields..The lack of any kind of veiling or graying of the background. 

 

Does it matter?  It is an aesthetic issue and does for me.


Scott Mortimer
 

>>Excuse my ignorance but I’m wondering what the difference in that telescope vs. my Celestron Evolution 9.25 SCT (https://www.celestron.com/products/nexstar-evolution-925-telescope) is. I can get some pretty amazing views through it. Am I missing out on something even better?

It sounds like you're having fun and not missing out on anything!  I've had a lot of good views through SCT's and enjoy the big aperture compared to refractors.  This Mak is like anything else, you spend more money, you get a better machine.   I can give a crude layperson's understanding of what makes this one special.

The Mak-Cass design has a smaller secondary obstruction than SCT's for better contrast.  Also the optical design produces less aberrations in the FOV.  So the views are sharper & you see more detail in objects.  AP scopes have more precise optics - better quality mirrors & lenses - than mass-produced scopes.   So even for the same design they would produce better images.

Even with these advantages, these 10" AP Maks are especially coveted because they are permanently aligned with no user collimation needed!  And the design has certain properties that apparently handle cool-down and temperature change better than prior designs from other companies.   So you get "refractor-like" performance in a larger aperture & smaller tube.

-Scott