Questar should have made a 5" Mak-Cass

On Sunday, March 13, 2016 at 12:33:58 AM UTC, palsing wrote:
On Saturday, March 12, 2016 at 12:54:12 PM UTC-8, SlurpieMcDoublegulp wrote:

Snell is a stalker, stalking you in every thread.

He's just being an authoritarian bully that very picture of a fascist....

This only reinforces my tendency not to respond to him, except on rare occasions when he is clearly over the top...

\Paul A

Unless gang behavior can be called politics there is really nothing only self-serving attention grabbing noise by one saying the opposite of the other in the desperate attempt to sound different when there really is no difference. I say this as an indifferent observer.

The real politics surrounding astronomy and terrestrial sciences is even more dreary from experience and in this too I am mostly indifferent. In terrestrial sciences it is all citation warfare and nothing ever gets done. For instance, in the area of plate tectonics and the dynamic behind crustal evolution/motion they chatter on about the 'debate being open' but inevitably can't extract themselves from the stationary Earth 'convection cells' notion and ignore that all rotating celestial objects ,including the Earth, possess an uneven rotational gradient between Equator and poles in the fluid interior.


Astronomy and these forums provide a more fertile ground than terrestrial sciences as theorists and magnification guys follow a basic schemata of celestial sphere ideologies. There are currently no pretenses involved as the descriptions have become more and more homocentric -

http://apod.nasa.gov/apod/ap140319.html


With no viable organization to bridge the gap between the motions of the Earth and terrestrial sciences it leaves a core ground where the theoretical and the stultifying citation dross is ignored and narratives are created using clues provided by modern tools. The appearance of the Sun at the North pole in a week is a case in point insofar as all sunrises involve a rotation with special attention given to the ins and outs as to why the Sun appears on the Equinox, stays in view until the opposite Equinox and then disappears for 6 months.


It a question of standards and balances in an era when there are none.

On Saturday, March 12, 2016 at 7:33:58 PM UTC-5, palsing, the little snot, chimes in again with:


This only reinforces my tendency not to respond to him, except on rare occasions when he is clearly over the top...

On Saturday, March 12, 2016 at 11:24:08 AM UTC-5, SlurpieMcDoublegulp wrote:

edit

slurp's crap deleted
He's just angry, probably as a result of listening to AM radio all day. Must take out his frustrations on the nearest "librul"

I don't pronounce liberal that way. You seem to have no facts to support whatever argument it is that you are trying to make.

remaining crap delete

On Saturday, March 12, 2016 at 3:54:12 PM UTC-5, SlurpieMcDoublegulp wrote:

Snell is a stalker, stalking you in every thread.



Actually, if you look objectively at the situation, I make reasonable comments with which peterson then disagrees, usually in a rather hostile manner.

You need to get your facts straight before making a fool of yourself, yet again.

On Sunday, March 13, 2016 at 7:36:43 AM UTC-5, wrote:
On Saturday, March 12, 2016 at 3:54:12 PM UTC-5, SlurpieMcDoublegulp wrote:

Snell is a stalker, stalking you in every thread.



Actually, if you look objectively at the situation, I make reasonable comments with which peterson then disagrees, usually in a rather hostile manner.

On Sunday, March 13, 2016 at 1:04:05 PM UTC-4, SlurpieMcDoublegulp wrote:

Similarly an RC with refractive field flattener optics is also a catadioptric. As is a Dall-Kirkham with compensating field lens. In both cases the field lenses play a vital part to add coma correction, astigmatism correction, field curvature correction and or spherical correction. These are not inconsequential optical defects, and without those corrections the instruments would be much less valuable and performance would not be anywhere as good.


If the lenses can be removed and the scope still functions reasonably well, ie spherical aberration is absent or at least endurable for some purposes, then the scope was NOT a catadioptric prior in the first place.

Furthermore most cats were designed to be made cheaply, not for extremely good off-axis correction.

On Sun, 13 Mar 2016 11:45:48 -0700 (PDT), wrote:

On Sunday, March 13, 2016 at 1:04:05 PM UTC-4, SlurpieMcDoublegulp wrote:

Similarly an RC with refractive field flattener optics is also a catadioptric. As is a Dall-Kirkham with compensating field lens. In both cases the field lenses play a vital part to add coma correction, astigmatism correction, field curvature correction and or spherical correction. These are not inconsequential optical defects, and without those corrections the instruments would be much less valuable and performance would not be anywhere as good.


If the lenses can be removed and the scope still functions reasonably well, ie spherical aberration is absent or at least endurable for some purposes, then the scope was NOT a catadioptric prior in the first place.

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 you design a system such that it requires both reflective and
refractive components to meet its specs, it is conventionally called
"catadioptric". That certainly includes any design with a concave
spherical primary and additional lens elements to correct for
aberrations. It's not a complex definition.

Furthermore most cats were designed to be made cheaply, not for extremely good off-axis correction.

Irrelevant to what constitutes a catadioptric design.

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.


peterson's word salad deleted

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.

If one removes the corrector from a Modified Dall-Kirkham (a catadioptric,) one ends up with a telescope that has enough spherical aberration to kill a horse.



If you design a system such that it requires both reflective and
refractive components to meet its specs, it is conventionally called
"catadioptric". That certainly includes any design with a concave
spherical primary and additional lens elements to correct for
aberrations. It's not a complex definition.

Furthermore most cats were designed to be made cheaply, not for extremely good off-axis correction.

Irrelevant to what constitutes a catadioptric design.

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".