Questar should have made a 5" Mak-Cass

On Mon, 14 Mar 2016 07:02:58 -0700 (PDT), wrote:

On Sunday, March 13, 2016 at 3:01:02 PM UTC-4, Chris L Peterson wrote:

There is no concept of "functions reasonably well". A designer creates
formal specifications for performance, and then adds whatever surfaces
are required to meet those specs. It doesn't matter whether the parts
are removable or not.

If one "designs" a Dall-Kirkham to "meet specs" by adding a coma corrector of some sort to it, -without- modifying the normal figure of either the primary or secondary, one can remove the corrector and still have a practical telescope. Even with the corrector, the scope was NOT a catadioptric.

With the corrector it is a catadioptric design. Without, it isn't.
There's something seriously screwed up with your concept of optical
design in that you include both "design" and "meet specs" in scare
quotes.

On Monday, March 14, 2016 at 10:21:57 AM UTC-4, peterson wrote:

Well, I guess nobody will ever buy a telescope from Snell Optics: "Our
Promise: It Functions Reasonably Well".

Lame comment.

On Monday, March 14, 2016 at 10:23:56 AM UTC-4, Chris L Peterson wrote:
On Mon, 14 Mar 2016 07:02:58 -0700 (PDT), wsnell01 wrote:

On Sunday, March 13, 2016 at 3:01:02 PM UTC-4, Chris L Peterson wrote:

There is no concept of "functions reasonably well". A designer creates
formal specifications for performance, and then adds whatever surfaces
are required to meet those specs. It doesn't matter whether the parts
are removable or not.

If one "designs" a Dall-Kirkham to "meet specs" by adding a coma corrector of some sort to it, -without- modifying the normal figure of either the primary or secondary, one can remove the corrector and still have a practical telescope. Even with the corrector, the scope was NOT a catadioptric.

With the corrector it is a catadioptric design. Without, it isn't.

Incorrect. That telescope is not catadioptric even with the lenses.

On Monday, March 14, 2016 at 8:21:57 AM UTC-6, Chris L Peterson wrote:
On Mon, 14 Mar 2016 05:42:38 -0700 (PDT), wrote:
On Sunday, March 13, 2016 at 3:01:02 PM UTC-4, Chris L Peterson wrote:

There is no concept of "functions reasonably well".

Nonsense! There are plenty of scopes that function reasonably well. Even a few very expensive scopes can be said to function reasonably well.

Well, I guess nobody will ever buy a telescope from Snell Optics: "Our
Promise: It Functions Reasonably Well".

The sort of response I would make is, instead, a thumpingly literal one.

Yes, telescopes exist that function reasonably well. However, their existence does not in any way refute Peterson's claim, which was not that telescopes that function reasonably well do not exist, but that such categories as "functions reasonably well" or "functions quite well indeed" and so on do not exist as formally-defined concepts within the science of optics.

John Savard

On Monday, March 14, 2016 at 2:03:34 PM UTC-4, Quadibloc wrote:
On Monday, March 14, 2016 at 8:21:57 AM UTC-6, Chris L Peterson wrote:
On Mon, 14 Mar 2016 05:42:38 -0700 (PDT), wsnell01 wrote:
On Sunday, March 13, 2016 at 3:01:02 PM UTC-4, Chris L Peterson wrote:

There is no concept of "functions reasonably well".

Nonsense! There are plenty of scopes that function reasonably well. Even a few very expensive scopes can be said to function reasonably well.

Well, I guess nobody will ever buy a telescope from Snell Optics: "Our
Promise: It Functions Reasonably Well".

The sort of response I would make is, instead, a thumpingly literal one.

Yes, telescopes exist that function reasonably well. However, their existence does not in any way refute Peterson's claim, which was not that telescopes that function reasonably well do not exist, but that such categories as "functions reasonably well" or "functions quite well indeed" and so on do not exist as formally-defined concepts within the science of optics.

A Newtonian with or without a coma corrector can be said to function reasonably well, whereas a Modified Dall-Kirkham (cat) without its correctors most likely would not be said to function reasonably well, AEBE. It's how the reflector performs in the absence of correctors that is crucial as to whether the instrument call be called a catadioptric WITH a corrector. THAT is the distinction that has generally been understood.

On Mon, 14 Mar 2016 08:52:53 -0700 (PDT), wrote:

If one "designs" a Dall-Kirkham to "meet specs" by adding a coma corrector of some sort to it, -without- modifying the normal figure of either the primary or secondary, one can remove the corrector and still have a practical telescope. Even with the corrector, the scope was NOT a catadioptric.

With the corrector it is a catadioptric design. Without, it isn't.

Incorrect. That telescope is not catadioptric even with the lenses.

The clearest indication that you live down there in Teabagistan is not
only are you obviously ignorant, but you take pride in your ignorance
are relish demonstrating it.

On Monday, March 14, 2016 at 3:38:49 PM UTC-5, Chris L Peterson wrote:
On Mon, 14 Mar 2016 08:52:53 -0700 (PDT), wrote:

If one "designs" a Dall-Kirkham to "meet specs" by adding a coma corrector of some sort to it, -without- modifying the normal figure of either the primary or secondary, one can remove the corrector and still have a practical telescope. Even with the corrector, the scope was NOT a catadioptric.

With the corrector it is a catadioptric design. Without, it isn't.

Incorrect. That telescope is not catadioptric even with the lenses.

The clearest indication that you live down there in Teabagistan is not
only are you obviously ignorant, but you take pride in your ignorance
are relish demonstrating it.

I think you should tone it down. A difference of opinion is not ignorance. Right now we don't have an infallible standard that everyone agrees to. Similar fights erupted over what is an apochromat, a semi-apo, and what is a planet, whether Pluto was one or not.

On Mon, 14 Mar 2016 13:47:10 -0700 (PDT), SlurpieMcDoublegulp
wrote:

On Monday, March 14, 2016 at 3:38:49 PM UTC-5, Chris L Peterson wrote:
On Mon, 14 Mar 2016 08:52:53 -0700 (PDT), wrote:

If one "designs" a Dall-Kirkham to "meet specs" by adding a coma corrector of some sort to it, -without- modifying the normal figure of either the primary or secondary, one can remove the corrector and still have a practical telescope. Even with the corrector, the scope was NOT a catadioptric.

With the corrector it is a catadioptric design. Without, it isn't.

Incorrect. That telescope is not catadioptric even with the lenses.

The clearest indication that you live down there in Teabagistan is not
only are you obviously ignorant, but you take pride in your ignorance
are relish demonstrating it.

I think you should tone it down. A difference of opinion is not ignorance. Right now we don't have an infallible standard that everyone agrees to. Similar fights erupted over what is an apochromat, a semi-apo, and what is a planet, whether Pluto was one or not.

Not at all. There is no more "difference of opinion" here than there
would be if he denied anthropogenic climate change. If he wanted to
say that he, personally, would not call an optical system consisting
of mixed reflective and refractive elements "catadioptric", I'd tell
him that he was welcome to call it anything he wants, but that most
optical designers would disagree (indeed, I earlier pointed out that
there is no governing body defining optical terms, they are simply
used by convention). Had he said that a telescope with a concave
primary mirror and a removable refractive corrector element would
still probably be _marketed_ as a Newtonian, I'd agree (and I said
something along those lines upthread).

But he said none of these more reasonable things which might genuinely
reflect a different opinion. What he said was "incorrect", which is,
in fact incorrect. So he is demonstrating his ignorance, apparently
with pride.

On Monday, March 14, 2016 at 8:47:14 PM UTC, SlurpieMcDoublegulp wrote:
On Monday, March 14, 2016 at 3:38:49 PM UTC-5, Chris L Peterson wrote:
On Mon, 14 Mar 2016 08:52:53 -0700 (PDT), wrote:

If one "designs" a Dall-Kirkham to "meet specs" by adding a coma corrector of some sort to it, -without- modifying the normal figure of either the primary or secondary, one can remove the corrector and still have a practical telescope. Even with the corrector, the scope was NOT a catadioptric.

With the corrector it is a catadioptric design. Without, it isn't.

Incorrect. That telescope is not catadioptric even with the lenses.

The clearest indication that you live down there in Teabagistan is not
only are you obviously ignorant, but you take pride in your ignorance
are relish demonstrating it.

I think you should tone it down. A difference of opinion is not ignorance.. Right now we don't have an infallible standard that everyone agrees to. Similar fights erupted over what is an apochromat, a semi-apo, and what is a planet, whether Pluto was one or not.

You are such strange people by the limitation you impose on yourselves and thereby unable to deal with issues which should never have arisen in the first place. It is not so much a lack of common sense but a deficit in the technical and historical antecedents which mark you off as simply magnification enthusiasts calling yourselves 'astronomers' on that account. This would normally be fine were it not that a rotating celestial sphere is employed to supplement the use of magnification and that is where it gets you into trouble. In the few decades here I have yet to see someone raise themselves above their attachment to telescopes and actually look at how the great astronomers looked out at the motions in the celestial arena instead of the ineffective 'looking up'.

The very name 'Planet' indicates an object defined by its observed motion in contrast to the Sun and moon and Not by size or composition -

" Moreover, we see the other five planets also retrograde at times,
and stationary at either end [of the regression]. And whereas the sun
always advances along its own direct path, they wander in various
ways, straying sometimes to the south and sometimes to the north; that
is why they are called "planets" [wanderers]. " Copernicus

http://apod.nasa.gov/apod/ap011220.html

In the magnification hobbyist's mind it is size that matters but all the recent fuss shows is how diluted the concept of astronomy has become even with the improvements in imaging.

Within that statement of Copernicus is now a huge shift in perspective which drops the observed motion of the Sun through the constellations and replaces it with the Earth's orbital inputs which puts the stars in motion behind the Sun in a line-of-sight observation -

https://www.youtube.com/watch?v=MdFrE7hWj0A

https://www.youtube.com/watch?v=eeQwYrfmvoQ


Astronomy never makes it into wider circulation because people assume it begins when darkness sets in and fidgety men with telescopes come out to identify objects. It is so much less than what astronomy actually is that it provides an obstacle rather than a benefit to the observer who has never encountered the connection they have between their participation in the Earth's daily,annual and galactic motions with all the objects in view in daylight or in darkness.

The 'planet definition' only exposed how vacuous the technical and historical perceptions among magnification enthusiasts actually is and it is not that they are unapologetic or embarrassed, they really believe they are within the stream of astronomical tradition when clearly they are not.

On Monday, March 14, 2016 at 5:10:13 PM UTC-4, Chris L Peterson wrote:

Not at all. There is no more "difference of opinion" here than there
would be if he denied anthropogenic climate change.

The hypocrisy of you warmingistas tends to promote skepticism, so either zip it or cut your CO2 to **** near zero.


If he wanted to
say that he, personally, would not call an optical system consisting
of mixed reflective and refractive elements "catadioptric", I'd tell
him that he was welcome to call it anything he wants, but that most
optical designers would disagree (indeed, I earlier pointed out that
there is no governing body defining optical terms, they are simply
used by convention). Had he said that a telescope with a concave
primary mirror and a removable refractive corrector element would
still probably be _marketed_ as a Newtonian, I'd agree (and I said
something along those lines upthread).

Unlike you, I am looking at the various optical configurations, whether designed from scratch or made up on the fly, to decide what scopes would -logically- be called catadioptric and what would scopes definitely would not, even if they somehow resembled catadioptrics. That logical approach is NOT something which you have done, peterson.


But he said none of these more reasonable things which might genuinely
reflect a different opinion. What he said was "incorrect", which is,
in fact incorrect.

Hypocrite much?

BTW, I was correct in calling out your incorrect statements, peterson.

So he is demonstrating his ignorance, apparently
with pride.

I am hardly ignorant of optics, you little snot.