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1 inch APO vs 12 inch SCT

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#151 yellobeard

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Posted 05 January 2018 - 04:05 PM


I think the Edge scopes have cooling vents and it's easy to get third-party fans that work for them. It should be a stock feature, like it is in big dobs, though.

I realize that the Edge SCT’s have vents but fans or at least a port or two where fans could be added as an aftermarket accessory, should be on the back plate behind the mirror.

Meade did exactly that with their 7-inch Mak. So why not with SCT’s?

Bob
The vent solution in the Edge absolutely is not sufficient, even with fans! They help a bit, but thats it. Most commercial fan solution merely are not solving much of the thermal problems.

And @treadmarks: If a C8 would cost twice the prize, it probably would have way better optics with lower tolerances, the feeling about a C8 would be diffetent, more stable, worth the prize (if they do a good job).. It would be on par with for example Mewlon, and a lot of people buy Mewlons..

Edited by yellobeard, 05 January 2018 - 04:11 PM.


#152 SandyHouTex

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Posted 05 January 2018 - 04:16 PM

 


So thermal issues are no reason anymore to place an APO refractor above a super high quality SCT.
 

I don't know of any super high quality readily available SCT, especially in a 16".

In mass produced SCT's there are none IMHO. Regardless of aperture. Good for the money? Some. But super high quality? None. 

Super high quality APO/s up to 6" are readily available, their culprit being the lack of bigger sizes and a hefty price per inch of aperture of course. There are very few high quality SCT's and Mak's available between 3.5" and 12", most are NLA new, all are scarce and expensive. And per inch of aperture, none reach the cleanliness of the Airydisk under even the best conditions of the same or somewhat smaller aperture high end APO that I have seen. 

 

The Celestron Edge HDs are of very high quality.  If you read the white paper on them there is a lot of testing done on the OTAs before they're shipped out.

 

My C14, C11, C9.25, C8, C6, and C5 are all 1/8 wave or better.  That's really excellent and I couldn't be happier.  By the way, how many SCTs and Maks do you own?


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#153 SandyHouTex

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Posted 05 January 2018 - 04:29 PM

 

Yes I’m exaggerating lol.gif   but why is this a thing in so many refractor discussions on the web?

Why is It that so many will do a comparison of a 4 inch APO and an 8 inch SCT or Newtonian and think that they see more in the APO? Limiting magnitude and resolution will surely be better in the larger scope. Am I missing something?

Provided it's good quality...

 

 

It's like this:

 

1. The apo will provide the absolute best image for it's aperture.  There's no other design that can match it's performance inch for inch . Therefore it can APPEAR to show more than it's size should. In reality it's merely maximized it's full aperture potential.  Other designs do not fulfill their potential as well.

 

2. Apertures APO's typically come in do not resolve the seeing as well as bigger scopes. This can provide a steadier image leading to the false belief it's a more detailed image than a larger scope can provide. It can therefore appear more aesthetically pleasing. This factor coupled with number 1 are the two main things driving APO hype.

 

3. The maximized aperture potential, plus better aesthetics under seeing conditions ALSO couple with the following potent ingredient: Less apparent irradiation.  Meaning, 200x through a 4" is providing an image that's bright but not excessively so. There isn't the glare associated with say, 200x through an 8".  Some refractor folks love to tout this as a result of superior contrast and so on, but it's simply that the small apertures need to work at a higher power per inch of aperture negating the effects of excessive irradiation.   

 

In a nutshell, because the APOs are so very efficient it can lead to boastful claims against other larger less aperture effective designs.  The hard reality of it all though is that even with the seeing effects degrading the image, higher irradiation at lower power per inch and so on, the less aesthetically large aperture scope view will trounce the smaller apertures .   Contrast aside, no small aperture APP, despite maximized contrast efficiency can get past it's angular resolution limits. 

 

Me, I think APOs are great. At night's out at a site frequented by others where inevitably the APO makes an appearance it's always a pleasure, sometimes a revelation.  I never really see it in the light of challenging other scopes but a sampled view of what it's like to look through a virtually perfect aperture.

 

Pete

 

Most of your claims are opinions of an emotional nature with no science to back them up.  For example:

 

Item 1 - "The apo will provide the absolute best image for it's aperture.  There's no other design that can match it's performance inch for inch ."  Really?

Item 3 - Makes no sense.  Because it's smaller and the image is dimmer it looks better?  What???

"In a nutshell, because the APOs are so very efficient (?) it can lead to boastful claims against other larger less aperture effective designs."  More hog wash I'm afraid.


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#154 SandyHouTex

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Posted 05 January 2018 - 04:31 PM

 

Much can be done to improve the stability of the images in SCT and Mak telescopes under falling temperatures and I applaud those who try their best to find good solutions for this. 

The solution is a nice apo refractor! Sorry Eric just kidding but…

 

Here in Pennsylvania, even my open tube Mewlon 210 needs fans to facilitate cooling and eliminate heat plumes from reforming during the night if the temperature is falling, as it usually does on most nights during the year. The fans  I added to my Mewlon 210 do a nice job.

 

It really is criminal that Meade and Synta/Celestron (and yes even the Quester 7) don’t at least offer fans as an option for their SCT’s and Maks. Tak puts them in their upper-end Mewlons but even the 210 and 180 really need them.

 

Bob

 

I thin it would be nice if maybe the SCT and Mak manufacturers did the same thing as Astro-Physics does which is have a removable back for cooling.  Seems to work excellent for them and wouldn't be too hard to implement.



#155 yellobeard

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Posted 05 January 2018 - 04:44 PM



So thermal issues are no reason anymore to place an APO refractor above a super high quality SCT.

I don't know of any super high quality readily available SCT, especially in a 16".
In mass produced SCT's there are none IMHO. Regardless of aperture. Good for the money? Some. But super high quality? None.
Super high quality APO/s up to 6" are readily available, their culprit being the lack of bigger sizes and a hefty price per inch of aperture of course. There are very few high quality SCT's and Mak's available between 3.5" and 12", most are NLA new, all are scarce and expensive. And per inch of aperture, none reach the cleanliness of the Airydisk under even the best conditions of the same or somewhat smaller aperture high end APO that I have seen.
The Celestron Edge HDs are of very high quality. If you read the white paper on them there is a lot of testing done on the OTAs before they're shipped out.

My C14, C11, C9.25, C8, C6, and C5 are all 1/8 wave or better. That's really excellent and I couldn't be happier. By the way, how many SCTs and Maks do you own?
White paper or not, also for the Edge-HD, they still use the same glass and the same polishing method on the schmidt corrector plate, causing roughness that could be prevented.. and 1/8 lambda does not cover all possible surface errors.

If they would make a 'super edge-hd' using a BK7 plate polished with pitch, that would make a difference!

Edited by yellobeard, 05 January 2018 - 04:46 PM.

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#156 Mitrovarr

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Posted 05 January 2018 - 05:07 PM


I think the Edge scopes have cooling vents and it's easy to get third-party fans that work for them. It should be a stock feature, like it is in big dobs, though.

I realize that the Edge SCT’s have vents but fans or at least a port or two where fans could be added as an aftermarket accessory, should be on the back plate behind the mirror.

Meade did exactly that with their 7-inch Mak. So why not with SCT’s?

Bob
The vent solution in the Edge absolutely is not sufficient, even with fans! They help a bit, but thats it. Most commercial fan solution merely are not solving much of the thermal problems.

And @treadmarks: If a C8 would cost twice the prize, it probably would have way better optics with lower tolerances, the feeling about a C8 would be diffetent, more stable, worth the prize (if they do a good job).. It would be on par with for example Mewlon, and a lot of people buy Mewlons..

There are not a lot of owners of Takahashi anything. I would be willing to bet there's at least 100 C8s in the world for every Mewlon.

#157 Mitrovarr

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Posted 05 January 2018 - 05:12 PM

Or, to put it another way - there are at least five to ten C8s of some sort in the local club alone. In fifteen years of observing and going to regional star parties, I don't think I have seen a Takahashi scope of any kind, and I have absolutely not seen a Mewlon.

Stuff that expensive just doesn't exist in the same universe as most people. Even the C8 is a huge stretch for many.
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#158 Gofr

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Posted 05 January 2018 - 05:27 PM

Or, to put it another way - there are at least five to ten C8s of some sort in the local club alone. In fifteen years of observing and going to regional star parties, I don't think I have seen a Takahashi scope of any kind, and I have absolutely not seen a Mewlon.

Stuff that expensive just doesn't exist in the same universe as most people. Even the C8 is a huge stretch for many.

True that. I only have a C9 (and even then just the standard non-edge XLT) because I was able to find one used at a very good price. A new one, even non-edge, is way beyond my current price point.

Edited by Gofr, 05 January 2018 - 05:28 PM.


#159 Peter Besenbruch

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Posted 05 January 2018 - 06:01 PM


What I always laugh about, because it is ridiculous, is the "my refractor has pinpoint stars while SCTs give bloated star images".  I hear it all of the time, but of course it's not true.  ...  I think many times the SCTs with "bloated" images are just not in equilibrium with the environment.  I have seen this happen with APO triplets that are airspaced.  It takes awhile for them to cool down as well.

... OTA equilibrium of the compound optical design of an SCT and MAK is such that they can take inordinately long to acclimate, and they may never acclimate over an evening of observing.  This is common experience.

But not in Hawaii, yet still SCTs don't measure up very well. I don't want to minimize the effects of acclimation, but I have yet to see an SCT perform at the level of either my Maksutovs or refractors. Actually, one came close to my 120mm, but unfortunately the focusing mechanism broke. The owner "fixed" it, but now image shift is several minutes, and focusing isn't clean. Let's face it, SCTs aren't precision instruments.

 

That said, neither is my 180mm Mak. You just have to look at one of these things to realize that. It, too, has mirror image shift (40-50") out of the box. Jon's posting of the Dutch SCT shows what a precision instrument might look like. So if cooling isn't a critical factor, and manufacturing precision isn't, what is? One of the factors that Yellowbeard keeps bringing up is the corrector. The Maksutov corrector is made from better glass, and is given the full optical treatment. That shows up in star tests in the smoothness of the defocused star rings.

 

I tend to give some credence to Yellowbeard's comments, because I have seen similar assertions made by Rohr, backed up by not-so-pretty pictures. Maksutovs (of the Gregory persuasion) also tend to use longer f-ratio mirrors. These may be easier to make than the roughly f2 primaries of the SCT, though I don't know how big a factor this is.



#160 Daniel Mounsey

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Posted 05 January 2018 - 06:13 PM

 

 


So thermal issues are no reason anymore to place an APO refractor above a super high quality SCT.
 

I don't know of any super high quality readily available SCT, especially in a 16".

In mass produced SCT's there are none IMHO. Regardless of aperture. Good for the money? Some. But super high quality? None. 

Super high quality APO/s up to 6" are readily available, their culprit being the lack of bigger sizes and a hefty price per inch of aperture of course. There are very few high quality SCT's and Mak's available between 3.5" and 12", most are NLA new, all are scarce and expensive. And per inch of aperture, none reach the cleanliness of the Airydisk under even the best conditions of the same or somewhat smaller aperture high end APO that I have seen. 

 

The Celestron Edge HDs are of very high quality.  If you read the white paper on them there is a lot of testing done on the OTAs before they're shipped out.

 

My C14, C11, C9.25, C8, C6, and C5 are all 1/8 wave or better.  That's really excellent and I couldn't be happier.  By the way, how many SCTs and Maks do you own?

 

 

1/8 wave for all those scopes? How did you determine that? also, I'd like to know what procedure you use to determine that a triplet has taken longer to acclimate than a doublet. 


Edited by Daniel Mounsey, 05 January 2018 - 06:46 PM.


#161 CHASLX200

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Posted 05 January 2018 - 06:45 PM

 

 


So thermal issues are no reason anymore to place an APO refractor above a super high quality SCT.
 

I don't know of any super high quality readily available SCT, especially in a 16".

In mass produced SCT's there are none IMHO. Regardless of aperture. Good for the money? Some. But super high quality? None. 

Super high quality APO/s up to 6" are readily available, their culprit being the lack of bigger sizes and a hefty price per inch of aperture of course. There are very few high quality SCT's and Mak's available between 3.5" and 12", most are NLA new, all are scarce and expensive. And per inch of aperture, none reach the cleanliness of the Airydisk under even the best conditions of the same or somewhat smaller aperture high end APO that I have seen. 

 

The Celestron Edge HDs are of very high quality.  If you read the white paper on them there is a lot of testing done on the OTAs before they're shipped out.

 

My C14, C11, C9.25, C8, C6, and C5 are all 1/8 wave or better.  That's really excellent and I couldn't be happier.  By the way, how many SCTs and Maks do you own?

 

I would have to look thru them all before i could judge them.  You must have got lucky that they are all excellent. But what is one's excellent may not be my excellent.


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#162 junomike

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Posted 05 January 2018 - 06:55 PM

 

 

 


So thermal issues are no reason anymore to place an APO refractor above a super high quality SCT.
 

I don't know of any super high quality readily available SCT, especially in a 16".

In mass produced SCT's there are none IMHO. Regardless of aperture. Good for the money? Some. But super high quality? None. 

Super high quality APO/s up to 6" are readily available, their culprit being the lack of bigger sizes and a hefty price per inch of aperture of course. There are very few high quality SCT's and Mak's available between 3.5" and 12", most are NLA new, all are scarce and expensive. And per inch of aperture, none reach the cleanliness of the Airydisk under even the best conditions of the same or somewhat smaller aperture high end APO that I have seen. 

 

The Celestron Edge HDs are of very high quality.  If you read the white paper on them there is a lot of testing done on the OTAs before they're shipped out.

 

My C14, C11, C9.25, C8, C6, and C5 are all 1/8 wave or better.  That's really excellent and I couldn't be happier.  By the way, how many SCTs and Maks do you own?

 

I would have to look thru them all before i could judge them.  You must have got lucky that they are all excellent. But what is one's excellent may not be my excellent.

 

Some people feel the EdgeHD series is held to a higher standard than the non-EdgeHD OTA's.

Not sure if that's true or not but my 8" EdgeHD was a perfect as ANY SCT I've viewed through (out of 10 or more) although a few 10" ACF's come close..


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#163 Daniel Mounsey

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Posted 05 January 2018 - 07:29 PM

 

 

 

 


So thermal issues are no reason anymore to place an APO refractor above a super high quality SCT.
 

I don't know of any super high quality readily available SCT, especially in a 16".

In mass produced SCT's there are none IMHO. Regardless of aperture. Good for the money? Some. But super high quality? None. 

Super high quality APO/s up to 6" are readily available, their culprit being the lack of bigger sizes and a hefty price per inch of aperture of course. There are very few high quality SCT's and Mak's available between 3.5" and 12", most are NLA new, all are scarce and expensive. And per inch of aperture, none reach the cleanliness of the Airydisk under even the best conditions of the same or somewhat smaller aperture high end APO that I have seen. 

 

The Celestron Edge HDs are of very high quality.  If you read the white paper on them there is a lot of testing done on the OTAs before they're shipped out.

 

My C14, C11, C9.25, C8, C6, and C5 are all 1/8 wave or better.  That's really excellent and I couldn't be happier.  By the way, how many SCTs and Maks do you own?

 

I would have to look thru them all before i could judge them.  You must have got lucky that they are all excellent. But what is one's excellent may not be my excellent.

 

Some people feel the EdgeHD series is held to a higher standard than the non-EdgeHD OTA's.

Not sure if that's true or not but my 8" EdgeHD was a perfect as ANY SCT I've viewed through (out of 10 or more) although a few 10" ACF's come close..

 

 

When I worked with Celestron, I spent some time in QC speaking with the tech's. They're basically checked to make sure they're collimated and aligned after receiving them because the secondary adjustment is EXTREMELY tight and they want to make sure astrophotos are as flat as possible in all four corners. I also recall them using a full frame camera to check the corners as well but Amir in charge of QC knows best and is the one to get the best information from. As far as optical quality compared to the standard SCT, both are held to the same standards. 


Edited by Daniel Mounsey, 05 January 2018 - 07:38 PM.

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#164 CHASLX200

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Posted 05 January 2018 - 07:42 PM

 

 

 

 

 


So thermal issues are no reason anymore to place an APO refractor above a super high quality SCT.
 

I don't know of any super high quality readily available SCT, especially in a 16".

In mass produced SCT's there are none IMHO. Regardless of aperture. Good for the money? Some. But super high quality? None. 

Super high quality APO/s up to 6" are readily available, their culprit being the lack of bigger sizes and a hefty price per inch of aperture of course. There are very few high quality SCT's and Mak's available between 3.5" and 12", most are NLA new, all are scarce and expensive. And per inch of aperture, none reach the cleanliness of the Airydisk under even the best conditions of the same or somewhat smaller aperture high end APO that I have seen. 

 

The Celestron Edge HDs are of very high quality.  If you read the white paper on them there is a lot of testing done on the OTAs before they're shipped out.

 

My C14, C11, C9.25, C8, C6, and C5 are all 1/8 wave or better.  That's really excellent and I couldn't be happier.  By the way, how many SCTs and Maks do you own?

 

I would have to look thru them all before i could judge them.  You must have got lucky that they are all excellent. But what is one's excellent may not be my excellent.

 

Some people feel the EdgeHD series is held to a higher standard than the non-EdgeHD OTA's.

Not sure if that's true or not but my 8" EdgeHD was a perfect as ANY SCT I've viewed through (out of 10 or more) although a few 10" ACF's come close..

 

 

When I worked with Celestron, I spent some time in QC speaking with the tech's. They're basically checked to make sure they're collimated and aligned after receiving them because the secondary adjustment is EXTREMELY tight and they want to make sure astrophotos are as flat as possible in all four corners. I also recall them using a full frame camera to check the corners as well but Amir in charge of QC knows best and is the one to get the best information from. As far as optical quality compared to the standard SCT, both are held to the same standards. 

 

When did you work for Celestron?  I wonder why some super bad scopes slipped out from Meade and Celestron?



#165 Daniel Mounsey

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Posted 05 January 2018 - 07:47 PM

2012-14



#166 Asbytec

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Posted 05 January 2018 - 07:51 PM

This may be one of the best comparison threads I've read. Great discussion.

 

It's important to realize a scope does not have to be perfect to perform. Does a "decidedly prejudicial" view begin at Strehl 0.997? I am not saying nearly perfect, unobstructed Strehl does not produce some amazing views of a 1" arc Airy disc. The central peak of the PSF is equal to it's polychromatic Strehl, that's amazing in itself. You get what you pay for. What I am saying is, even a 'diffraction limited' image is nothing to sneeze at when the scope is prepped for observing (cooled and collimated) and seeing is the final arbiter. Hopefully seeing is excellent so you can really see what the scope can do. 

 

I have a very smooth, ~1/6 PVW LSA, cheapo, China made, piece of ****, obstructed, and mass produced Synta scope that has shown me craterlets on Plato's floor 0.9 miles in diameter near lunar perigee. It appears to have a decent Strehl and is obstructed to about 0.8 of it's peak intensity, give or take, i.e., operating near the diffraction limit. If I did the small angle formula math right, this full crater form, with a pit and a bright rim, subtended (from memory) 0.72" arc and well below Dawes. Dawes does not apply to extended objects, but contrast and contrast transfer does. I bet a 6" APO could show the same craterlet on that night in the tropics. But, I doubt a smaller 4" APO would have resolved it even in excellent seeing.

 

I have also seen surface albedo features, such as Osiris, on Ganymede, amazing views of Jupiter, mars, and Saturn and hints of spiral arms in several brighter NGC galaxies under yellow/orange zone skies. Where's the beef? It performs above its weight class, and some of that is the human element as well as preparation and observing conditions. I have yet to hear any 6" APO owner reporting detail on Ganymede, even though the scope is capable of it when conditions permit. And only two guys I know of have reported seeing the same craterlet in a 6" aperture, one of them was a 6" Newt. 

 

I have owned more than a few SCTs over the years, and yes have seen heat plumes well into the night because I did not know how to acclimate the scope back then. These days, an ice pack does the job perfectly (the insulation solution seems reasonable, too) in a tropical climate. Textbook 6" obstructed stars right out the door at observing time and steady views in excellent seeing. And crappy optics. 


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#167 Asbytec

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Posted 05 January 2018 - 07:58 PM

"When I worked with Celestron, I spent some time in QC speaking with the tech's. They're basically checked to make sure they're collimated and aligned after receiving them because the secondary adjustment is EXTREMELY tight and they want to make sure astrophotos are as flat as possible in all four corners. I also recall them using a full frame camera to check the corners as well but Amir in charge of QC knows best and is the one to get the best information from. As far as optical quality compared to the standard SCT, both are held to the same standards."

 

 

Sometimes I wonder if folks confuse a flat field (to the "Edge") for excellent optics. I doubt they are the same thing. But, a cluster of online IF tests seem to show a descent Strehl at 0.9 or better. Sometimes worse. Add an obstruction, yada yada...


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#168 CHASLX200

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Posted 05 January 2018 - 07:59 PM

2012-14

That was way after the scopes i had used that were made in the 70's and 80's. Just don't understand how so many bad scopes got out of the factory like they did.  I don't think the hit and miss is as bad today.



#169 Jon Isaacs

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Posted 05 January 2018 - 08:02 PM

The other day I was at the 99 cent store and noticed a table with telescopes for $5.99.  Always interested in seeing what any telescope can do, I paid my $6 and walked out the door with my new scope..  It's not much, an aperture of about 35mm, mostly plastic, Galilean optics.. Probably a singlet, maybe a plastic doublet.  But it does work, it does magnify images and it does show the moon in more detail than I see naked eye.  It might be comparable to Galileo's scope. 

 

Six dollar scope.jpg

 

Using this scope, I was struck my the same thoughts, the same feelings I get when I page though Sam Brown's All About Telescopes:  "Jon, are you ever spoiled."

 

A commercial 8 inch SCT, an 80mm achromat, they're darn good scopes and very capable of providing a life time of views.. Just how is it that I became so darn picky?"

 

Ever wonder about that.. just how the perfection of the equipment came to over take the wonders of the heavens above as a priority?

 

Jon

 

 

 

 


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#170 Daniel Mounsey

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Posted 05 January 2018 - 08:10 PM

I recently did more comparisons using a very special special C8 against an Edge HD. After digging further into this sample with Alan Hale, it appears to have been figured by Carl Zambuto's mentor, master optician Bob Goff. This particular SCT will compete or surpass any cassegrain in its aperture class regardless of price and it's the only sample I've evaluated that really blew me away. All of Jupiter's bands snap right into crystal clarity without any ambiguity. 

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#171 Arizona-Ken

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Posted 05 January 2018 - 08:17 PM

There other day I was at the 99 cent store and noticed a table with telescopes for $5.99.  Always interested in seeing what any telescope can do, I paid my $6 and walked out the door with my new scope..  It's not much, an aperture of about 35mm, mostly plastic, Galilean optics.. Probably a singlet, maybe a plastic doublet.  But it does work, it does magnify images and it does show the moon in more detail than I see naked eye.  It might be comparable to Galileo's scope. 

 

attachicon.gifSix dollar scope.jpg

 

Using this scope, I was struck my the same thoughts, the same feelings I get when I page though Sam Brown's All About Telescopes:  "Jon, are you ever spoiled."

 

A commercial 8 inch SCT, an 80mm achromat, they're darn good scopes and very capable of providing a life time of views.. Just how is it that I became so darn picky?"

 

Ever wonder about that.. just how the perfection of the equipment came to over take the wonders of the heavens above as a priority?

 

Jon

I hope the Mods don't make a fuss, but Jon, this properly should go to the Refractor Forum where it will be compared ad nauseum to Taks, TECs, and the occasional Stellarvue. I'm sure it will be declared better than any mirrored telescope. Did you get a Strehl report with it? lol.gif

 

Arizona Ken


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#172 CHASLX200

CHASLX200

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Posted 05 January 2018 - 08:18 PM

I recently did more comparisons using a very special special C8 against an Edge HD. After digging further into this sample with Alan Hale, it appears to have been figured by Carl Zambuto's mentor, master optician Bob Goff. This particular SCT will compete or surpass any cassegrain in its aperture class regardless of price and it's the only sample I've evaluated that really blew me away. All of Jupiter's bands snap right into crystal clarity without any ambiguity. 

There are a few super sharp SCT's out there.  Wished i never sold my 1984 C8.  That was a 450x scope easy and close to many of the 8" F/8 Newts i had in the past.  I may buy a C5 for $1k, made in 1976 and looks like it was made today.  I know the price is about double the going rate, but i will pay more for a better scope.


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#173 PXR-5

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Posted 05 January 2018 - 08:25 PM

Magical fairy dust, LOL

Everyone knows that even the Walgreens Christmas 50mm refractor can beat a 16 inch Dob.

#174 Bill Barlow

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Posted 05 January 2018 - 09:48 PM

I recently did more comparisons using a very special special C8 against an Edge HD. After digging further into this sample with Alan Hale, it appears to have been figured by Carl Zambuto's mentor, master optician Bob Goff. This particular SCT will compete or surpass any cassegrain in its aperture class regardless of price and it's the only sample I've evaluated that really blew me away. All of Jupiter's bands snap right into crystal clarity without any ambiguity. 

Well which C8 won in this side by side observing session?

 

Bill


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#175 yellobeard

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Posted 06 January 2018 - 08:19 AM

As nice as this refractor/reflector discussion is, as always, it will be a discussion without end!

The question always remains: Should you base things on the real world, where people are destined to accept the commercially aviable quality, which varies from brand to brand, even from model to model.. Of course, as most people cannot improve their scopes themselves (exept for the very important insulation mods) involving the commercial avaible quality is the best for most.
But when you do that, you definitely will not be fair to scopes that fail to impress you, only because of wider factory tolerances.
NOBODY that has never saw a truely exeptional SCT, as they are build from the ground, by only a few people on this World, ever does have the right to be negative about what the optical SCT setup can do! Which is the same with any other reflective scope.
Because then, the theoretics will be against you!
No matter how many reasons one can sum up, why a SCT would not be capable to be on par with a super high quality Apochromatic refractor, theoretically, and based on new insights, there is only one factor that remains: the central obstruction.
Even when someone writes that with the multiple surfaces in an SCT it will not ever compete with a 'perfect' refractor, I can tell from experience, that I and maybe a few others, cam reach a surface quality, that is high enough, that even with 100 reflective surfaces, there will be no total error that can be determined in the field!

So if this discussion is about real life, and performance in the field, then we should stick to that, and not go into the theoretics of things..

Edited by yellobeard, 06 January 2018 - 08:21 AM.

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