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C8 v. Mak 7

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#26 Astrojedi

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Posted 23 July 2019 - 03:38 PM

Easy to see a diff from a good Mak and a normal SCT. Owned around 250 scopes and not even close in my book. I would take a good 7' Mak jack over any 8" SCT.
 

Differences if any would be very minor. In my personal experience I was not able to tell the difference but maybe others can.



#27 aa6ww

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Posted 29 July 2019 - 05:48 PM

There is a review out now comparing the 180 Skywatcher to a C9.25 Non Edge and the Mak outdoes the C9.25 on planetary sharpness and just overall planetary performance. Since planets are observed on Axis, there wouldn't be a difference between edge and no edge SCT's

Its a pretty good realistic review. Both just production scopes, nothing special about either of them.

I'll try and dig it up.

Its a gold tube Skywatcher 180 Mak.

No surprises on the results. The smaller SCT's are not planet killers.

..Ralph

#28 khingdheano

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Posted 02 August 2019 - 10:36 PM

OK, I'll weigh in on this since I own a C8 Evolution, purchased new in 2018, plus a SW 180 Mak, purchased new in 2017. Tonight I viewed Jupiter through both scopes.

I'll say right off that both scopes are stored on my covered patio, so there is no adjustment time regarding temperature. I have also recently collimated the C8, whereas I have never made any adjustments to the Mak.

Tonight I first mounted the SW Mak onto the Evo mount and had a look using a Baader Hyperion Mark III zoom ep at the 20mm setting (about 137x). This telescope also has a Moonlight Crayford focuser and an Orion 2" mirror diagonal. After viewing Jupiter for about 1/2 hour, I switched the OTAs and had a look through the C8, same ep but at 16mm setting (127x). This scope has the standard focuser, and a William Optics 2" dialectric diagonal. The immediate subjective impression was the C8 was clearly sharper. If I said Jupiter appeared to be crossed by 60 super-thin lines drawn with a mechanical pencil when viewed through the Mak, I would raise that number to 100 lines when viewed through the C8. Festoons only vaguely seen with the Mak were quiet definite through the C8.

Yes, there are variables, the differences in diagonals and the Crayford focuser extending the focal length of the Mak which renders my magnification calculation askew--- but the bottom line is this: Looking first through the Mak, I was pleased with the image. Looking secondly through the C8, I said out loud, "Oh yeah!" It was a sharper view. Maybe a less experienced astronomer than myself might have equated the two scopes, but I have over 50 years observing experience, and subtle differences are more apparent to me.

If I had to give up one of these scopes, it would be the Mak. Now the bad news--- if I had known in 2017 what I know now, I could have saved myself some dough--- which I would have undoubtedly spent on some other astro gear anyway...

The view through the C8 definitely rivals the best view of that planet I ever had, which was through my GEM-mounted 10-inch Meade Newtonian (also known as The Water Heater) back in 1994, during those halcyon days of the Shoemaker-Levy impacts. I've no doubt I would be able to see those atmospheric blemishes with both of these scopes, but I would for sure want to have this C8 on hand.

Cheers, and clear skies!


Edited by khingdheano, 02 August 2019 - 10:51 PM.

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#29 luxo II

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Posted 03 August 2019 - 07:23 AM

Not a fair contest. You said you’ve recently collimated the C8, but never collimated the mak.

With both types of scope there is a very significant difference in image sharpness when the collimation is good but not perfect, va what you see when perfect.

Collimate the mak and try again.

#30 Bill Barlow

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Posted 03 August 2019 - 09:35 AM

Maybe the Maks collimation was already spot-on.

 

Bill


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#31 khingdheano

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Posted 03 August 2019 - 10:13 AM

It was just a quick subjective comparison, not a scientific study. Too many variables to get a definitive answer. And yes, the collimation of the Mak looks fine.


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#32 Auburn80

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Posted 03 August 2019 - 10:14 AM

I've been following this thread with interest and there doesn't seem to be a general consensus. It may very well be as Richard Whalen posted; it depends on the luck of the draw. I'm sorely tempted to try a 180 and give it a thorough shake down.

#33 Burgher

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Posted 03 August 2019 - 04:07 PM

I owned both, the Orion 180 mm Mak and a Celestron 8se.  My experience was that the Mak was much sharper than my 8se on both, lunar and planetary images (both scopes were collimated). I was very surprised at the difference. 


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#34 Asbytec

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Posted 05 August 2019 - 11:12 AM

Reading the last two accounts, one definitely favoring the C8 and the other favoring the 180 MCT may be due to differences in quality of each C8. Both Mak views we're nice, but maybe not as nice as a very good sample C8 yet better than possibly an average sample C8.

There is likely some variation in mass production MCTs, too, but maybe they are more consistent. I've really enjoyed my 150 MCT, as do so many through their testimonies, and have always wondered why. The only answer that seems reasonable to me is the smooth spherical surfaces, and not necessarily better correction. Maks are not easy to make with tight tolerances, but I suspect they can be made smooth (ref Rolands Star Testing essay speaking to the ability to make smooth surfaces commercially) or possibly aspheric (like the Meade 7). I know mine is smooth and free of any zones (and has some redidual higher order SA) and really sharp. It eats magnification like popcorn.

I've owned three SCTs, but it was too long ago and I dare not try to remembering what the images looked like for comparison. Plus, I gained a lot of dedicated experience with Jupiter in the MCT, so that counts enough to distort my more inexperienced views through my previous SCTs.

Maks are often very good scopes. No doubt SCTs are better these days, more often than not. So, it may just boil down to the luck of the draw. If I had to make the choice, I'd think long and hard about the 180 MCT based on my views through a 150 MCT. I never got a 180, though, because I (almost) already have one. In fact, I didn't get a larger Dob, until recently, or a 4" APO because the MCT made me wonder why I needed either. I was enjoying it and didn't feel the need.

Get a good sample of either, you won't be disappointed, I'm sure. Which has the best chance of producing a good sample? All I know is, after putting my MCT through the ringer, I began to realize what I had. It became my "poor man's Questar". (OK, just to be clear, it's probably not really a Questar, but it felt like one).


Edited by Asbytec, 05 August 2019 - 09:50 PM.

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#35 Auburn80

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Posted 05 August 2019 - 04:48 PM

Gonna give the Celestron version a shot. Ordered it today.
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#36 Asbytec

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Posted 06 August 2019 - 09:41 AM

Gonna give the Celestron version a shot. Ordered it today.


Report back so others can know more
Thanks
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#37 ATM57

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Posted 07 August 2019 - 01:18 AM

Gonna give the Celestron version a shot. Ordered it today.

Looking forward to your report.


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#38 azure1961p

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Posted 07 August 2019 - 08:51 AM

Reading the last two accounts, one definitely favoring the C8 and the other favoring the 180 MCT may be due to differences in quality of each C8. Both Mak views we're nice, but maybe not as nice as a very good sample C8 yet better than possibly an average sample C8.

There is likely some variation in mass production MCTs, too, but maybe they are more consistent. I've really enjoyed my 150 MCT, as do so many through their testimonies, and have always wondered why. The only answer that seems reasonable to me is the smooth spherical surfaces, and not necessarily better correction. Maks are not easy to make with tight tolerances, but I suspect they can be made smooth (ref Rolands Star Testing essay speaking to the ability to make smooth surfaces commercially) or possibly aspheric (like the Meade 7). I know mine is smooth and free of any zones (and has some redidual higher order SA) and really sharp. It eats magnification like popcorn.

I've owned three SCTs, but it was too long ago and I dare not try to remembering what the images looked like for comparison. Plus, I gained a lot of dedicated experience with Jupiter in the MCT, so that counts enough to distort my more inexperienced views through my previous SCTs.

Maks are often very good scopes. No doubt SCTs are better these days, more often than not. So, it may just boil down to the luck of the draw. If I had to make the choice, I'd think long and hard about the 180 MCT based on my views through a 150 MCT. I never got a 180, though, because I (almost) already have one. In fact, I didn't get a larger Dob, until recently, or a 4" APO because the MCT made me wonder why I needed either. I was enjoying it and didn't feel the need.

Get a good sample of either, you won't be disappointed, I'm sure. Which has the best chance of producing a good sample? All I know is, after putting my MCT through the ringer, I began to realize what I had. It became my "poor man's Questar". (OK, just to be clear, it's probably not really a Questar, but it felt like one).

 

 

My repeating objection with a lot of these kinds of comparisons is simply that the test was done wrong.  Looking at Jupiter, probably at 200x doesn't say squat really but speaks to lower power aesthetics.  Comments like "the belts were more contrasty" and the like fall short of a definitive conclusion.  Instead ramp up both systems on Ganymede and THEN make the call. Few think to, or want to do this but this orb seperates one system from another.  These 25x per inch of aperture "tests" are quaint even but they aren't challenging the systems so much as seeing which one idles better than the other.

 

On Ganymede consider these tests:

 

1. Which one shows the greatest contrast (which will be subtle to say the most).

 

2. Which one shows THE SMALLEST contrasts?  (This one can't be overstated).

 

Any triumph of one scope over the other here will translate to Jupiter as well .  Oh, one scope may make it seem prettier than the other but if it's shackled with lower angular res - well , the Ganymede test will show that.

 

 

First think that came to mind in this test is 278x for the 7" mak and 320x for the C8 but I'm quite confident this real advantage was never exercised in so many of these kinds of comparisons.

 

Pete


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#39 Bill Barlow

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Posted 07 August 2019 - 09:17 AM

Those magnifications seem too high unless you have perfect seeing conditions.  I could never use those scopes here with those magnifications.

 

Bill


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#40 Astrojedi

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Posted 07 August 2019 - 09:53 AM

Every time a SCT outperforms it is a unique sample or some such thing and the observation is dismissed.

I my experience agrees with khing. As I will say again the newer SCTs are much more consistent in quality.

In terms of physics there is no reason why a 180mm Mak should outperform a 203mm SCT.
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#41 Auburn80

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Posted 07 August 2019 - 11:08 AM

Every time a SCT outperforms it is a unique sample or some such thing and the observation is dismissed.

I my experience agrees with khing. As I will say again the newer SCTs are much more consistent in quality.

In terms of physics there is no reason why a 180mm Mak should outperform a 203mm SCT.


Agreed; in terms of physics, there should little to no difference. Where it starts getting murky are the production techniques used followed by all the variables inherent in real world tests/observations/comparisons. Does the production process for a Mak lend itself to a tighter sample to sample variation? When comparing, are the scopes treated as equally as possible? Etc, etc, . . .

At any rate, I'm starting to formulate a plan that I think will come to a satisfactory conclusion for Me and My intended usage.

BTW, even though I'm not the OP, I really appreciate all the thoughtful discussion and inputs here.
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#42 Astrojedi

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Posted 07 August 2019 - 02:35 PM

Keep in mind that both are mass produced scopes.

Also high quality smooth spherical mirrors are incredibly easy to produce. In my ATM days even I was able to quite easily produce almost perfect spheres. Parabolas are very hard... much harder.

So, if you are making an optical quality argument it boils down to the SCT corrector vs. the Mak meniscus quality. It is hard for me to believe that the Mak corrector is consistently so much better given the 40+ yrs of experience C & M have making SCTs. Especially with much better manufacturing processes in the last 10-15 years after the move to China.

Edited by Astrojedi, 07 August 2019 - 02:40 PM.


#43 Yu Gu

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Posted 07 August 2019 - 03:56 PM

From a visual planetary observation point of view:

 

There are a few things going for the MCT 180

1. Potentially smoother optics due to all spherical surfaces vs. known roughness issue with SCT corrector plate (not sure how much effect)

2. Longer focal ratio, which is easier on eyepiece (not sure how much effect)

3. The mak design would have a lower spherochromatism, which may add a few percentage points in terms of strehl (not sure how much effect)

4. Slightly smaller aperture meaning slightly less sensitivity to seeing conditions (not sure how much effect)

5. Smaller central obstruction

 

There are a few things going for the C8 Edge HD

1. Slightly larger aperture can lead to higher resolution and brightness (if the atmosphere cooperate, which is rare in most places)

2. Slightly lighter and has better ventilation, which can lead to quick acclimatization

3. Flatter field, which helps when you don't have a tracking mount

 

To me, it's a toss-up. The differences are probably less than the sample to sample variations in each model (which are probably quite small these days). I have a good Orion 180mm MCT, but I am ok if someone trades me with a C8 Edge flowerred.gif

Gu


Edited by Yu Gu, 07 August 2019 - 03:57 PM.


#44 Astrojedi

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Posted 08 August 2019 - 11:22 AM

Gu,
Nice post. Some additional points.

1. As far as I know the newer SCT OTAs don’t suffer from a rough corrector.
2. Longer FL - I agree with this. Actually I think this is the key factor in the difference in views.
3. Spherochromatism - yes this could be a factor but much smaller one.
4. Smaller aperture - while less sensitive to seeing also means less resolution and color saturation
5. Maks have pretty much a similar central obstruction as the C8 even a 2-3% cannot be seen at the EP. (in my informed opinion central obstruction matters a lot less than you would think but that is a discussion for another thread)

#45 Auburn80

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Posted 08 August 2019 - 09:07 PM

So, for discussion/entertainment purposes . . .
Why do 5", 6" and 7" Maks even exist? So that one can use simpler eyepieces with long fl? Is that the only advantage a Mak now has?

Or could it be that smooth optics Plus lower spherochromatism Plus smaller obstructions make a detectable difference?

#46 freestar8n

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Posted 08 August 2019 - 10:17 PM

Keep in mind that both are mass produced scopes.

Also high quality smooth spherical mirrors are incredibly easy to produce. In my ATM days even I was able to quite easily produce almost perfect spheres. Parabolas are very hard... much harder.

So, if you are making an optical quality argument it boils down to the SCT corrector vs. the Mak meniscus quality. It is hard for me to believe that the Mak corrector is consistently so much better given the 40+ yrs of experience C & M have making SCTs. Especially with much better manufacturing processes in the last 10-15 years after the move to China.

This is a common view about maks but it is almost the other way around.  The sct design is fairly tolerant to errors in the curvature of the components - and although the corrector is aspheric, it is figured the same way a sphere is - except it is warped during the process.  You can make the individual components and put it all together and it has a good chance of working well.  Imperfect components can be rotated into an optimal orientation for best system performance - and if need be a surface can be slightly retouched.

 

In contrast - a spot maksutov of reasonable aperture is not likely to work well even if all the surfaces are perfect spheres - because the tolerance in the curvatures is so tight on getting everything exactly right - the result will likely have spherical aberration.  This is all made harder when you have a) faster system b)  larger aperture or c) thin corrector.

 

In addition, some large maks, such as the Meade mak7, include a highly aspheric component, which is the primary in the Meade case.  And it isn't trivial to make a large, fast asphere.  I'm not sure how they do it for the Meade.

 

So - unless the Mak is small and slow, it either has a strongly aspheric element, or the overall system was retouched in an autocollimator to work well.  That's how Maksutov himself, and Gregory made them.

 

One obvious point is that if maks were so easy to make and only relied on spheres - why are they so expensive?  It isn't just the corrector that adds to the price.

 

Why do they have such an allure?  I don't know - but I assume questar ads played a role.  That's probably what helped motivate me to buy a Meade mak7.  But once I had a C11 I had no reason to use it.  11" f/10 has same focal length as 7" f/15, so only difference was aperture with a given eyepiece.  I didn't compare it to c8, though.

 

Frank


Edited by freestar8n, 08 August 2019 - 10:19 PM.

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#47 Astrojedi

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Posted 08 August 2019 - 11:08 PM

So, for discussion/entertainment purposes . . .
Why do 5", 6" and 7" Maks even exist? So that one can use simpler eyepieces with long fl? Is that the only advantage a Mak now has?

Or could it be that smooth optics Plus lower spherochromatism Plus smaller obstructions make a detectable difference?

I wonder that as well. The benefits of a 180mm Mak vs an EdgeHD 8 are not clear to me. I definitely preferred the view in my EdgeHD 8.

 

Why would a commercial Mak have better / smoother optics than a commercial SCT? Both have mass produced spherical mirrors which are very good by the way. Spherical mirrors are very easy to produce to a very accurate curve.

 

That Maks have better/smooth optics is an urban legend that just refuses to die. 


Edited by Astrojedi, 08 August 2019 - 11:08 PM.


#48 Asbytec

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Posted 08 August 2019 - 11:19 PM

Why do they have such an allure?  I don't know...

 

Frank

Hi frank, yea, I do not know, either, why the allure and I do not know how they do it. Spherical or aspheric, but I do know mine tested between 0.1 PV (0.017 RMS) and 0.22 PV (0.037 RMS) by the examples in figure 189 here (at the bottom of the page) which are spherical. Even the in focus PSF matches nicely. It certainly did not test like anything close to 1/4 LSA. In fact, prior to my baffle mod (vignetting full aperture), it very much resembled Suiter's 1/8 LSA and 33% obstructed sims. But I was struggling to compare with the wrong simulated images.  

 

It's difficult, IMO, to star test MCTs accurately because we likely will not see pure classic lower order spherical like a parabola, but a mix of higher and lower order SA. In any case, even in the worst case 0.037 RMS has some allure. So, however they do it, the get it pretty much right. Of course, you'll find many SCTs in the 90's Strehl range, as well. Maybe it's the smoothness of the spherical (or aspheric) curves that gives them some allure. I know mine is incredibly smooth without so much as a hint of roughness in excellent seeing and no zones (other than what is likely HSA). It's certainly not 1/4 PV pure over corrected LSA, either. 


Edited by Asbytec, 08 August 2019 - 11:44 PM.


#49 Asbytec

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Posted 08 August 2019 - 11:36 PM

That Maks have better/smooth optics is an urban legend that just refuses to die. 

Roland Christen, "An example is the Maksutov Cassegrain. This system can be manufactured many different ways, but one popular way is to have all surfaces spherical, which cuts down the need for hand work. Machines exist now that can lay down a 1/20 wave or better spherical surface on a piece of glass without any human intervention."

 

http://www.csun.edu/.../startest2.html

 

A MCT report similar to mine, note the artificial star test. Unfortunately, no Lyot test. 

http://r2.astro-fore...ksutov-150-1800

 

I do not know how or if SCTs use the same technology, but I have seen some pretty rough IF reports on various sites. Not all of them, of course, but more than a few. Which leads to production variance. 

http://r2.astro-fore...pt-hervorragend

http://r2.astro-fore...-9dot25-im-test

 

Wolfgang Rohr, "At least as interesting is the question of the smoothness of a system...However, the influence of the Schmidt plate on the quality of reproduction is generally known , as is the retouching via the secondary mirror, a problem that Maksutov does not have to contend with because spherical surfaces make a smoother polish possible."

http://r2.astro-fore...rich-gebuerstet


Edited by Asbytec, 08 August 2019 - 11:41 PM.


#50 Astrojedi

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Posted 09 August 2019 - 01:28 AM

Roland Christen, "An example is the Maksutov Cassegrain. This system can be manufactured many different ways, but one popular way is to have all surfaces spherical, which cuts down the need for hand work. Machines exist now that can lay down a 1/20 wave or better spherical surface on a piece of glass without any human intervention."

 

http://www.csun.edu/.../startest2.html

 

A MCT report similar to mine, note the artificial star test. Unfortunately, no Lyot test. 

http://r2.astro-fore...ksutov-150-1800

 

I do not know how or if SCTs use the same technology, but I have seen some pretty rough IF reports on various sites. Not all of them, of course, but more than a few. Which leads to production variance. 

http://r2.astro-fore...pt-hervorragend

http://r2.astro-fore...-9dot25-im-test

 

Wolfgang Rohr, "At least as interesting is the question of the smoothness of a system...However, the influence of the Schmidt plate on the quality of reproduction is generally known , as is the retouching via the secondary mirror, a problem that Maksutov does not have to contend with because spherical surfaces make a smoother polish possible."

http://r2.astro-fore...gen-den-strich-

I think you missed my point - first both optics in question are mass produced and use spherical mirrors. Why should one be better than the other or vary in quality more than the other. If anything SCTs are actually easier to make.

 

Second the SCT production variance is also another myth propagated by outdated information. I have seen all these websites and in many instances they are testing 20 year old SCT OTAs. The is ridiculous imo. The newer SCTs are much more consistent quality wise. Having looked through 25+ of these I did not find any lemons. The EdgeHDs were even better.




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