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Celestron Edge HD vs Meade ACF [Optical Properties]

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#1 rkelley8493

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Posted 14 July 2019 - 03:50 PM

How much of a difference is the Celestron Edge HD optical performance to the Meade ACF? I've heard the saying "Meade for Mak, Celestron for SCT", are the Celestron's much better? If they were the same aperture using the same eyepiece, would one notice a visual difference between the two? [I'm not concerned with their performance in astrophotography, just curious about their visual performance]



#2 Eddgie

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Posted 14 July 2019 - 04:08 PM

If they were made to the same quality standards, then view should be so similar that it would be hard to tell them apart.

 

If though is the operative word here.   This is my opinion, but it is based on the data I have seen on a lot of star tests, and that data suggests that both Meade and Celestron produce scopes that vary considerably in quality, and if you got a really excellent Meade, and a really poor Celestron, maybe the Meade would to better.

 

That being said, I have seen more examples of Meade scopes that were lemons than Celetron scopes, and some of the Meades were so awful that it is hard to believe Meade would ship such a scope.  I have never seen a bench test of a Celstron that was nearly as bad as some of the worst case Meades. 

 

So, if they were the same quality, one should expect the view to be about the same, but in the real world, it would have to be done sample by sample and this or that Meade or Celestron might beat this or that Celestron or Meade. 

 

If you want to beat either one of these, buy an Intes Micro MCT with deluxe optics. It is a slam dunk if fine optical quality is important. 


Edited by Eddgie, 14 July 2019 - 04:09 PM.

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#3 jhayes_tucson

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Posted 14 July 2019 - 04:22 PM

The Celestron HD has a flat field that is very well corrected so it's a much better choice for imaging with a large sensor.  I can't comment on Meade but Celestron has consistently improved their optical quality over the last number of years so your chances of getting a good instrument are pretty good.

 

John


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#4 Eddgie

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Posted 14 July 2019 - 04:23 PM

And I am sure someone is going to pipe up and say how I must be wrong about Meade, but here is an example of a Meade with less than .5 Strehl:

 

http://fidgor.ru/Obs...2/test_333.html

 

Another big lemon.. Strehl of .315.  Bow wow!

 

http://fidgor.ru/Obs...2/test_459.html

 

And one more.  Not a big Bow wow, but below the diffraction limit:

 

http://fidgor.ru/Obs...2/test_431.html

 

 

Here though is an excellent ACF with Strehl of .956, which to me is quite excellent by any measure.

 

http://fidgor.ru/Obs...2/test_427.html

 

So it really depends on the specific sample, but after seeing dozens and dozens of tests of Meade and Celestron SCTs, I can answer the "Who let the dogs out, Woof Woof" question with this.  Meade has let some absolutely horrible scopes out of the pens.   While you will ocassionally see Celestron fall below the diffraction limit, I have see enough Meade bench tests to have the opinion that you are more likely to get a bitter lemon from Meade than from Celestron. 

 

And back to your question?  It depends more on the quality of the two individual samples you are comparing.   If they are about the same, they will produce about the same view.  If one is a dog and the the other is at the top end of the bell curve, then the one with the best optics will win..

 


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#5 Eddgie

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Posted 14 July 2019 - 04:36 PM

The Celestron HD has a flat field that is very well corrected so it's a much better choice for imaging with a large sensor.  I can't comment on Meade but Celestron has consistently improved their optical quality over the last number of years so your chances of getting a good instrument are pretty good.

 

John

I hear this about Celestron and Meade, but the bench tests I am seeing suggest that both still vary considerably in quality.  

 

 

Maybe there are fewer real lemons though, and as long as it is decent optically the diffraction of the aperture and secondary will be the main limits to performance.   At the price point though, no one should expect Meade or Celetron to produce every scope with a Strehl of .9 or higher. 

 

My never ending search for bench tests has led me to the opinion that the bell curve for Celestron probably peeks around .92 which is nothing to sneeze at (and I would say absolutely in the "Good" category) so most will likely be somewhere in the .85 to .95 range, but until I go a few years without seeing a poor sample, I am going to make a guess that Meade and Celestron put together sets of optics that are diffraction limited, puts them in tubes, and sells them, with no particular effort made to ensure that they are any specific place on the quality bell curve. My bet is that by chance, some sets are excellent and some are poor, but most are Good.  That is the way mass production works.  

 

Example.. EdgeHD, which people somehow believe will have better optics than the standard SCT.  Here is one with .934 Streal, which by the way, is pretty much right at where I estimate the bell curve to peak.  Now this is a good scope but as I said, people think that the EdgeHDs are supposed to have better quality, and this one is pretty much in the middle of the quality range.... http://fidgor.ru/Obs...2/test_369.html


Edited by Eddgie, 14 July 2019 - 04:40 PM.

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#6 Jim Waters

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Posted 14 July 2019 - 04:45 PM

I have looked through a current 10" Meade SCT and a 11" Celestron SCT.  Stick with Celestron.  Moon image through the Meade were very poor.


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#7 stargazer60

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Posted 14 July 2019 - 05:09 PM

I agree jhayes I have a  Celestron 9.25 Edge HD & a 8" Edge HD and both have a flat field that is very well corrected. I use them both for astrophotography. waytogo.gif 


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#8 jhayes_tucson

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Posted 14 July 2019 - 05:12 PM

I hear this about Celestron and Meade, but the bench tests I am seeing suggest that both still vary considerably in quality.  

 

 

Maybe there are fewer real lemons though, and as long as it is decent optically the diffraction of the aperture and secondary will be the main limits to performance.   At the price point though, no one should expect Meade or Celetron to produce every scope with a Strehl of .9 or higher. 

 

My never ending search for bench tests has led me to the opinion that the bell curve for Celestron probably peeks around .92 which is nothing to sneeze at (and I would say absolutely in the "Good" category) so most will likely be somewhere in the .85 to .95 range, but until I go a few years without seeing a poor sample, I am going to make a guess that Meade and Celestron put together sets of optics that are diffraction limited, puts them in tubes, and sells them, with no particular effort made to ensure that they are any specific place on the quality bell curve. My bet is that by chance, some sets are excellent and some are poor, but most are Good.  That is the way mass production works.  

 

Yeah, I don't have any hard data to show population performance over time; however, Celestron implemented interferometric testing on assembled systems a while ago so that presents an opportunity to do better.  What did they do with that opportunity?  Who knows?  The few C14s that I've tested from recent batches have been pretty good.

 

Having run a couple of precision optical instrumentation companies, worked with the disk drive industry, and aerospace manufacturing, I have enough experience with mass production to tell you that this is most definitely not the way production normally works.  The disk drive industry ships about 10 million units per month  That's a product that requires production standards with dimensional control below one millionth of an inch (far more difficult than what a telescope requires) and they maintain an amazing level of quality and reliability.  They don't ship drives that are "mostly" just good with a few that are excellent.  It's all about quality systems that maintain tight controls over the process.  Trust me, Seagate has very detailed statistical data on every stage of their process and they know exactly how each drive performs relative to it's performance specs before it ships.  In my opinion, the ultimate problem at companies like Celestron is that not only do they have no quality system in place, but they don't even know what a "real" quality systems looks like.  A quality system is a LOT more than simply testing each scope before it ships to see if it meets some specification.  It touches every aspect of the company.  Unfortunately when it comes to consumer level telescopes, everything is cost driven so there is little incentive to implement a real quality system.  Quality isn't free and since most folks don't want to pay for it, here we are with hit or miss performance.

 

John


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#9 rkelley8493

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Posted 14 July 2019 - 05:19 PM

I took these pictures of the moon with my phone thru my LX90-10 

moon3.jpg

moon2.jpg

moon4.jpg



#10 havasman

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Posted 14 July 2019 - 05:21 PM

I know several folks with both brands of SCT. Several Meade buyers have returned brand new scope that were failures on receipt and no Meade owner I know has had a trouble free scope.

 

Reliability of the Celestrons whether fork, one-arm or EQ mounted has been high among the group I know.


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#11 rkelley8493

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Posted 14 July 2019 - 05:31 PM

And I am sure someone is going to pipe up and say how I must be wrong about Meade, but here is an example of a Meade with less than .5 Strehl:

 

http://fidgor.ru/Obs...2/test_333.html

 

Another big lemon.. Strehl of .315.  Bow wow!

 

http://fidgor.ru/Obs...2/test_459.html

 

And one more.  Not a big Bow wow, but below the diffraction limit:

 

http://fidgor.ru/Obs...2/test_431.html

 

 

Here though is an excellent ACF with Strehl of .956, which to me is quite excellent by any measure.

 

http://fidgor.ru/Obs...2/test_427.html

 

So it really depends on the specific sample, but after seeing dozens and dozens of tests of Meade and Celestron SCTs, I can answer the "Who let the dogs out, Woof Woof" question with this.  Meade has let some absolutely horrible scopes out of the pens.   While you will ocassionally see Celestron fall below the diffraction limit, I have see enough Meade bench tests to have the opinion that you are more likely to get a bitter lemon from Meade than from Celestron. 

 

And back to your question?  It depends more on the quality of the two individual samples you are comparing.   If they are about the same, they will produce about the same view.  If one is a dog and the the other is at the top end of the bell curve, then the one with the best optics will win..

That's shocking & disappointing to know that a manufacturer would allow such poor products out of their factory. I can see a slip up here and there, but that's ridiculous. Especially when the products are over $2000. You'd expect to get your money's worth on a consistent level. 

Side note - my Meade LX90 is a good product, and I really enjoy using it. I had some issues with the mount after a few months of use, but the OTA is a great performer. Same with my ETX125. They were both purchased from High Point Scientific, and they arrived in great shape. Nothing but good experiences with those guys. Keep up the good work HPS waytogo.gif  

I did notice a slip in quality on the LightBridge. I purchased it from a major online department store and not a telescope retailer. It was very sloppy out of the box. It wasn't packed very well and had some dings on the primary mirror housing. 1 for 3 isn't a good percentage for quality assurance. 


Edited by rkelley8493, 14 July 2019 - 09:17 PM.


#12 Boom

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Posted 14 July 2019 - 05:50 PM

Is there a reason why Meade ACF scopes need such a large secondary?   Are they using a slower primary?  Is a larger secondary easier to figure?


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#13 Mike Spooner

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Posted 14 July 2019 - 06:07 PM

I'm wondering if anyone has looked at the optical designs of these scopes. If I was designing a similar system, I'd try to come up with manufacturing tolerance where field lenses could be spaced during final assembly to optimize the image characteristics. I haven't ray traced such a design, just throwing conjecture about.

 

Mike Spooner



#14 rkelley8493

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Posted 14 July 2019 - 06:09 PM

Is there a reason why Meade ACF scopes need such a large secondary?   Are they using a slower primary?  Is a larger secondary easier to figure?

I've noticed that as well. The secondary mirrors look really large/oversized on the LX850 & LX600 series. I was wondering how the contrast & sharpness would be affected compared to Celestron and their smaller Central Obstruction.



#15 junomike

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Posted 14 July 2019 - 06:40 PM

I've had 2 Meade 10" ACF's and viewed through another and ALL were excellent optically, however the 8" EdgeHD I had was also excellent and I also found it's tone (Luna)

more clean.  Not sure if it was possibly newer or what.

That being said,  If I currently owned one, I wouldn't bother swapping it out for the other.


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#16 starman876

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Posted 14 July 2019 - 06:41 PM

I have always found better optics with the Celestrons.  Most Meades I have tried were soft so I have avoided them.  The Meade 7" Mak is fantastic.  I also have heard good things about the 16" Meades.  


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#17 WadeH237

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Posted 14 July 2019 - 07:02 PM

I took these pictures of the moon with my phone thru my LX90-10 

Any afocal shot, or even a single shot at prime focus, is going to fall far short of what the optics are capable of.  And indeed, these images are very, very soft.  This says nothing poor about your scope, or your skills as a photographer.  It's just an artifact of the method that you used to obtain them.

 

To really see how good the optics are photographically, you would either need to do a proper star test of the scope or do a video run and sort through a few thousand frames and stack the best, the way that high resolution planetary imaging is done.


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#18 Boom

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Posted 14 July 2019 - 07:11 PM

I've noticed that as well. The secondary mirrors look really large/oversized on the LX850 & LX600 series. I was wondering how the contrast & sharpness would be affected compared to Celestron and their smaller Central Obstruction.

 

Some of those are f/8 scopes, which makes sense.  However, even the f/10 scopes appear to have larger secondaries compared to their Celestron counterparts.


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#19 Achernar

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Posted 14 July 2019 - 07:43 PM

If memory serves, the Meade ACF's have a focal ratio of F/8, while the Celestron Edge HD are F/10 telescopes, with the exception of the 14-inch model, which is an F/11 telescope. Therefore with the same eyepiece, the Meades will give you a lower magnification and a wider true field of view. I cannot comment on how they perform visually because I never had one nor have I looked through any of them, but I do have an 8-inch Edge HD. The views through it are very impressive, and quite competitive with my 10-inch Dob on the planets. As long as it's collimated properly, you'll find the views very nice through ultra-wide angle eyepieces. I do not regret buying mine at all.

 

Taras


Edited by Achernar, 14 July 2019 - 07:45 PM.

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#20 rkelley8493

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Posted 14 July 2019 - 07:49 PM

Some of those are f/8 scopes, which makes sense.  However, even the f/10 scopes appear to have larger secondaries compared to their Celestron counterparts.

Oic.. the secondary would have to be larger to collect the wider plane of light. 



#21 rkelley8493

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Posted 14 July 2019 - 07:52 PM

If memory serves, the Meade ACF's have a focal ratio of F/8, while the Celestron Edge HD are F/10 telescopes, with the exception of the 14-inch model, which is an F/11 telescope. Therefore with the same eyepiece, the Meades will give you a lower magnification and a wider true field of view. I cannot comment on how they perform visually because I never had one nor have I looked through any of them, but I do have an 8-inch Edge HD. The views through it are very impressive, and quite competitive with my 10-inch Dob on the planets. As long as it's collimated properly, you'll find the views very nice through ultra-wide angle eyepieces. I do not regret buying mine at all.

 

Taras

The LX90 & LX200 are f/10 models. The LX850 & LX600 are f/8 models. I may be wrong about the 600s, someone please correct me if I am. I'm certain about the others though.



#22 carolinaskies

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Posted 14 July 2019 - 08:46 PM

How much of a difference is the Celestron Edge HD optical performance to the Meade ACF? I've heard the saying "Meade for Mak, Celestron for SCT", are the Celestron's much better? If they were the same aperture using the same eyepiece, would one notice a visual difference between the two? [I'm not concerned with their performance in astrophotography, just curious about their visual performance]

Meade sells ACF in F/10 and F/8 variants.  The F/8 has a larger secondary mirror set at a lesser distance to primary to achieve the relative change(4x instead of 5x). Want the skinny on Meade SCTs?  Talk to Doc Sherrod who has experience with far more SCT instruments first hand.
  

How different are the ACF and Edge?  Not enough to throw tons of money to one over the other or choose simply based on some false brand expectation of quality.  The ACF telescopes have the advantage of not needing specialized focal reducers, and the availability of the F/8 or F/10 version.  With the F/8 a focal reducer can be used to further get the system to a shorter focal length for imaging and there are many to choose from.  The F/8 also has an internal crayford support many find quite an advanced feature.  The ACF have the disadvantage of not having the Hyperstar option. 

The Edge has the advantage of locking primary mirror system to help with movement and vents in the tube(necessary due to design) along with the Hyperstar option.  The disadvantage is proprietary focal reducer and Hyper star costs which are considerable by comparison. 
 

Both ACF and Edge scopes are designed to use the 82 & 100 degree eyepieces to much advantage, that's one reason they were made.  Relative comparisons have indicated neither being superior in performance overall with examples performing on target or above expectations with only limited reports to the contrary and usually remedied by proper alignment or return due to defect.

Modern manufacturing processes make instruments more alike than different, the key is in the setup and matching of primary, secondary, and corrector.  A flawed corrector at the border of acceptability paired with mirrors also borderline can result in a scenario where there is a bad instrument.  It is THE BUYER's responsibility to reject defective instruments and return them to the vendor.  This is why regardless of what instrument you buy, YOU should be aware of the return procedure and policies of the vendor.  Choosing a good vendor goes a long way in ensuring YOU get a good instrument.  
 

Incredibly I've read stories on CN from individuals who have bought new instruments and let them sit for so many months that they get themselves in trouble when they finally decide to operate the instrument.  DON'T be one of those people.  It doesn't matter if you have nights of poor seeing, setting an instrument up and simply operating it will help in determining if basic operations of electronics are up to snuff.  Looking at what stars are available straight overhead and understanding how to check collimation will go a long way toward basic checkout of a telescope's optics.  If it's not properly colimated it won't matter the **** strehl number.  And many telescopes have been called bad by people unwilling to take the steps to do the things that must be done to optimize viewing enjoyment like simple colimation and acclimatization.

CN as a community is rather pro-Celestron as far as SCTs, or I should say there are a few very vocal cheerleaders...  Yet Meade offers a larger variety of SCT based instruments and mount combinations, which I think is a valid consideration in who is selling units to a broad swath of the consumer market. Yet the Meade specific forum is remarkably less active for current instrument issues (outside of the GPS issue hammering both companies legacy equipment). 

If someone were to shove either ACF or Edge into my hands I wouldn't frown on recieving either one, I like things in both designs and dislike other things. As far as performance, I doubt the vast majority of users of the equipment would disagree with my assessment.    Those who do, well they are welcome to their opinion. 


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#23 Astrojedi

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Posted 15 July 2019 - 12:51 AM

I hear this about Celestron and Meade, but the bench tests I am seeing suggest that both still vary considerably in quality.  

 

 

Maybe there are fewer real lemons though, and as long as it is decent optically the diffraction of the aperture and secondary will be the main limits to performance.   At the price point though, no one should expect Meade or Celetron to produce every scope with a Strehl of .9 or higher. 

 

My never ending search for bench tests has led me to the opinion that the bell curve for Celestron probably peeks around .92 which is nothing to sneeze at (and I would say absolutely in the "Good" category) so most will likely be somewhere in the .85 to .95 range, but until I go a few years without seeing a poor sample, I am going to make a guess that Meade and Celestron put together sets of optics that are diffraction limited, puts them in tubes, and sells them, with no particular effort made to ensure that they are any specific place on the quality bell curve. My bet is that by chance, some sets are excellent and some are poor, but most are Good.  That is the way mass production works.  

 

Example.. EdgeHD, which people somehow believe will have better optics than the standard SCT.  Here is one with .934 Streal, which by the way, is pretty much right at where I estimate the bell curve to peak.  Now this is a good scope but as I said, people think that the EdgeHDs are supposed to have better quality, and this one is pretty much in the middle of the quality range.... http://fidgor.ru/Obs...2/test_369.html

Can you point us to the bench tests you are referring to that demonstrate variable quality. More specifically tests that show samples worse than diffraction quality.

 

 


Edited by Astrojedi, 15 July 2019 - 12:56 AM.

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#24 Astrojedi

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Posted 15 July 2019 - 01:06 AM

And I am sure someone is going to pipe up and say how I must be wrong about Meade, but here is an example of a Meade with less than .5 Strehl:

 

http://fidgor.ru/Obs...2/test_333.html

 

Another big lemon.. Strehl of .315.  Bow wow!

 

http://fidgor.ru/Obs...2/test_459.html

 

And one more.  Not a big Bow wow, but below the diffraction limit:

 

http://fidgor.ru/Obs...2/test_431.html

 

 

Here though is an excellent ACF with Strehl of .956, which to me is quite excellent by any measure.

 

http://fidgor.ru/Obs...2/test_427.html

 

So it really depends on the specific sample, but after seeing dozens and dozens of tests of Meade and Celestron SCTs, I can answer the "Who let the dogs out, Woof Woof" question with this.  Meade has let some absolutely horrible scopes out of the pens.   While you will ocassionally see Celestron fall below the diffraction limit, I have see enough Meade bench tests to have the opinion that you are more likely to get a bitter lemon from Meade than from Celestron. 

 

And back to your question?  It depends more on the quality of the two individual samples you are comparing.   If they are about the same, they will produce about the same view.  If one is a dog and the the other is at the top end of the bell curve, then the one with the best optics will win..

Again we are back to SCT bashing even though the op is asking something else.

 

There are many logical errors in your argument. Here is one.

 

Some random Russian website tested Meade SCTs of various vintages and found variable quality. But somehow you managed to extrapolate these results to all new SCTs including Celestrons. 

 

Lets be clear, this tells you nothing about consistency of recent vintages of SCTs. Further even if recent vintages of SCTs have variability it tells you nothing about the standard deviation. For example are all at least diffraction limited? If so, that is quite an excellent outcome since that means you are limited by seeing rather optical quality. What’s wrong with that?

 

In my 20+ years of observing I can count on my fingers evenings where seeing was good enough to tell the difference in optical quality better than diffraction limited in apertures > 8”. Even then it was not conclusive.

 

Do you realize the kind of seeing you need to tell optical quality of scopes above and beyond diffraction limited with aperture 8” and above? As an experienced observer you should know this. 

 


Edited by Astrojedi, 15 July 2019 - 01:11 AM.

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#25 Eddgie

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Posted 15 July 2019 - 07:31 AM

Is there a reason why Meade ACF scopes need such a large secondary?   Are they using a slower primary?  Is a larger secondary easier to figure?

It needs it to be able to fully illuminate a large image circle.  For visual use, it might be possible to make it a little smaller, but the speed of the system requires that the secondary be rather large.

 

This is mostly a marketing response for the growth of imaging in the hobby, where you need a bigger fully illuminated field.  While the human eye and use with eyepieces makes it possible to get away with a 5mm to 10mm fully illuminated image circle, modern large chip sensors would vignette if you made the secondary smaller.  

 

So, these scopes are optimized more to imaging than visual use, and for imaging, the size of the secondary is not really all that big a deal because the scope will still resolve to its limit and contrast can be improved with processing. 


Edited by Eddgie, 15 July 2019 - 07:32 AM.

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