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Mak-Cass vs. SC

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#1 ReganJamesFord

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Posted 07 December 2018 - 09:32 PM

As a beginner, can someone please compare a Mak Cass vs. SC? Thank you.

Edited by ReganJamesFord, 07 December 2018 - 09:32 PM.


#2 carolinaskies

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Posted 07 December 2018 - 10:07 PM

The major differences in commercial Mak vs SCT

1. Mak is higher focal ratio, longer focal length - F/12-F/15 vs F/8-F10  Maks therefore tend to be more specific for planetary and small object DSO
2. Mak uses a corrector/reflective mirrored surface for secondary.   SCT use a secondary mirror attached to center of the corrector plate.
3. Mak has a thicker corrector plate spun as a disc to include the surface for the secondary mirror coating.  SCT corrector is a thinner plate glass with varied thickness to provide optical correction. 
4. Maks are harder to make as aperture is increased. Typically a Mak is 90mm - 7". SCTs are typically 5"-16" for commercial grade and are less costly due to the less effort necessary to create the corrector and secondary mirror.  

90mm Mak's are the starting point for what are considered reasonable performance optics in a closed tube application.  


 



#3 vtornado

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Posted 07 December 2018 - 10:09 PM

A maksutov telescope has all spherical components.

Which means the shape of all the optical surfaces are sections of a sphere.

Since the primary is a sphere, if there were no corrector lens the image would suffer from spherical abberations.

A sphere does not focus all the rays of light that hit it to a common point.  Mr. Maksutov figured that a lens in front of the spherical

mirror with the opposite spherical abberation would cancel out the shperical abberation of the primary.

 

A schmidt cassegranian telescope also has a shpherical mirror.   To correct for spherical abberations,

the corrector plate is an asphere.   If you were the look at it closely the center is thick the middle thin and

the edges thick again.  It is not a section of a sphere.   It the before the 70's it was very difficult

to make a lens of this shape.   It had to be hand ground.

However I think it was Celestron in the 70's, that patentened a process where these could

be mass produced with good quality with a machine.

 

Here is a thread.

https://www.cloudyni...194-mct-vs-sct/

 

I just got a C5 telesecope which is an SCT.   Many here will tell you that a mak is better than an SCT for planets.

I am dubious although I cannot tell you since I can't to a side by side.  I bought the C5 because it is lighter,

has a faster f ratio, the secondary size is about the same size as the mct if you count the baffeling, and it operates

at a full 127mm aperture whereas synta mak's are only operating at 120.

I am dubious about the planetary claims.  Both these scopes have spherical primary mirrors.

 

I made a post in cat's and cases asking some of these same questions.

https://www.cloudyni...d-i-go-127-mak/


Edited by vtornado, 07 December 2018 - 10:13 PM.

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#4 ReganJamesFord

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Posted 07 December 2018 - 10:16 PM

Thanks my friends, that’s interesting stuff. @Vtornado, I just bought my first scope, it is also a Celestron C5 spotting scope. I’m still trying to figure it out. Trying to figure out best accessories to view planets and moon. Any advice would be much appreciated.

#5 Luna-tic

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Posted 07 December 2018 - 10:40 PM

One other comparison is weight. For a given aperture, a Mak is heavier than the equivalent aperture SCT, due in part to its much thicker (and therefore heavier) corrector.



#6 Neptune

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Posted 08 December 2018 - 08:46 AM

I would highly remind these 2 books if interested in comparing different telescope optics.

 

Telescope Optics A Comprehensive Manual for Amateur Astronomers by Harrie Rutten and Martin van Venrooij

 

Telescopes, Eyepieces and Astrographs: Design, Analysis and Performance of Modern Astronomical Optics by Gregory Hallock Smith, Roger Ceragioli and Richard Berry


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#7 Eddgie

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Posted 08 December 2018 - 09:15 AM

Neptune offers a good resource for telescope design.

 

Some of the information above by other posters (no offense intended) is incomplete.  

 

MCTs can be just as fast as SCTs.   While the inexpensive ones are typically f/12.5 to f/15, there are f/10 MCTs out there.

 

Also, these f/10 MCTs do not use a mirror surface silvered on to the back of the correct.  Like SCTs, they use a mirror that is detached from the corrector.

 

The point is that an MCT does not have to be slower than an SCT but the cheap ones generally are.

 

As for good acessories for a C5, I recommend a good 1.25" wide field eyepiece like the ES 24mm wide field (or the much more expensive Televue 24mm Panotic though you won't see much difference in performance bewteen these). 

 

I would also highly recommend a good zoom eyepiece like a used Baader Hyperion Zoom.  You could do the very vast majority of all your observing with just these two eyepieces.

 

And get or make a dew shield.

 

So, suggestions:

  • 24mm ES eyepiece
  • Baader Zoom eyepiece
  • Dew Shield
  • Full aperture Baader Film solar filter for solar white light viewing
  • Observer's Chair
  • Sky Safari Phone App
  • Telrad

And frankly, neither of these is going to blow your socks off for planets and the quality variations mean that it is a roll of the dice as to whether this 127 MCT will be better than that C5.  Seriously, the quality of these is quite unpredictable and I have proof to back that statement up.  Most are decent, some are excellent, some are poor. 

 

Both will show rings of Saturn, major features on Jupiter, and a lot of detail on the moon.   You are not going to resolve much on Jupiter though. Just the primary could bands and maybe (when perfectly positioned and under perfect conditions) a bit of detail around the great red spot.  Don't expect to see a great deal using either of these types (as compared to something like a well made 8" reflector). 


Edited by Eddgie, 08 December 2018 - 09:20 AM.

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#8 bandazar

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Posted 08 December 2018 - 09:57 AM

An apo or ed refractor will blow the socks off a c5 or 127 mak if you are looking for vast improvement on planets.  But that's not what c5 and mak's are for.  They are for versatility and at least in small to medium sizes for compactness and easy travel and setup.

The difference in quality between a c5 and 127 mak on planets is probably going to be negligible unless you win the lottery and get one that has super optics.   I have viewed through a 127 make and own a nexstar 5.  I don't remember seeing any appreciable difference in image quality between the other, at least not compared to a similar sized refractor or zambuto optics reflector. 



#9 Magnetic Field

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Posted 08 December 2018 - 11:49 AM

Thanks my friends, that’s interesting stuff. @Vtornado, I just bought my first scope, it is also a Celestron C5 spotting scope. I’m still trying to figure it out. Trying to figure out best accessories to view planets and moon. Any advice would be much appreciated.

 

1. Post the eyepieces that you have got now.

 

2. And post what you would like to observe (are you planing to use your scope mostly for planets or  a combination of both: deep sky objects and planets)j.

 

3. Also are you living in a heavily polluted area? Check your site:

 

https://www.lightpol...ers=B0FFFFTFFFF

 

You can double click on your location and you get some light pollution numbers.

 

4. I think your C5 is a very potent scope (and definitely has to offer a whole lot more than a 80 mm apochromat). The C5 is also more useful for deep sky observing due to f/10 compared to the often seen say f/14 for a Maksutov of similar aperture.


Edited by Magnetic Field, 08 December 2018 - 11:54 AM.


#10 whizbang

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Posted 08 December 2018 - 12:18 PM

The C5 is a good choice.  This summer I compared a vintage orange tube with a newer Synta (Orion) MAK.  Saturn and Jupiter were visable,  the double double, M15, etc.  I found the views virtually identical. 

 

I also recommend a few accessories: the Explore Scientific 24MM 68 degree eyepiece, an Astrozap dew shield, and a good 9x50 finder scope.

OrionCelestron.jpg


Edited by whizbang, 08 December 2018 - 12:19 PM.

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#11 Eddgie

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Posted 08 December 2018 - 12:51 PM

Verty cool C5 Whizbang!

 

I am a big fan of the C5 on the fork.  That is a very nice scope you have there. Very versatile.  Can be used as a polar fork on a tripod or Alt-Az on a tabletop.  Excellent little package. You really don't see them around very much.  Nice to see one in what appears to be pristine condition.


Edited by Eddgie, 08 December 2018 - 12:52 PM.


#12 ReganJamesFord

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Posted 08 December 2018 - 02:52 PM

1. Post the eyepieces that you have got now.

2. And post what you would like to observe (are you planing to use your scope mostly for planets or a combination of both: deep sky objects and planets)j.

3. Also are you living in a heavily polluted area? Check your site:

https://www.lightpol...ers=B0FFFFTFFFF

You can double click on your location and you get some light pollution numbers.

4. I think your C5 is a very potent scope (and definitely has to offer a whole lot more than a 80 mm apochromat). The C5 is also more useful for deep sky observing due to f/10 compared to the often seen say f/14 for a Maksutov of similar aperture.

I have the following.

90* Orion Dialectirc Diagonal (yet to use it on clear night)
45* Orion Deluxe Diagonal
25mm Celestron Plossl that came with scope
8-24mm Celestron zoom ep
Orion Tritech 2 Tripod

I also bought a decent ep that my wife says I can’t open until Christmas! Lol. It’s an ES 14mm 82* widefield.

I haven’t been able to see the moon yet because it’s been cloudy. I’ve seen a few stars and they look like pretty decent points of light. I’ve seen Mars, but it looks basically like a star but red and a little fuzzy. I’ve seen Uranus, which was about the size of an Skittle in my view, but dull and fuzzy. Mind you, all of this has been seen on very cold, partly cloudy skies with bad seeing and tons of light pollution

I live in a Metro Detroit Neighborhood and view in my backyard, where I contend with house lights, street lights, and many view are over houses.

I do have a lake home in. Northern Michigan where it’s really dark. And a cabin in the Smoky Mountains in Tennessee, 1800 ft on the side of a mountain where it’s very very dark. I am hoping to take my scope to either one of these places in the spring and summer for better viewing. Because right now, most the things I see are small and blurry. But again, I’m a total rookie here.

Edited by ReganJamesFord, 08 December 2018 - 02:54 PM.


#13 Bill Barlow

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Posted 08 December 2018 - 10:03 PM

Have you checked the collimation lately?  It could sharpen up the images a bit if it needs a slight adjustment.

 

Bill


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#14 Magnetic Field

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Posted 09 December 2018 - 06:52 AM

I have the following.

90* Orion Dialectirc Diagonal (yet to use it on clear night)
45* Orion Deluxe Diagonal
25mm Celestron Plossl that came with scope
8-24mm Celestron zoom ep
Orion Tritech 2 Tripod

I also bought a decent ep that my wife says I can’t open until Christmas! Lol. It’s an ES 14mm 82* widefield.

I haven’t been able to see the moon yet because it’s been cloudy. I’ve seen a few stars and they look like pretty decent points of light. I’ve seen Mars, but it looks basically like a star but red and a little fuzzy. I’ve seen Uranus, which was about the size of an Skittle in my view, but dull and fuzzy. Mind you, all of this has been seen on very cold, partly cloudy skies with bad seeing and tons of light pollution

I live in a Metro Detroit Neighborhood and view in my backyard, where I contend with house lights, street lights, and many view are over houses.

I do have a lake home in. Northern Michigan where it’s really dark. And a cabin in the Smoky Mountains in Tennessee, 1800 ft on the side of a mountain where it’s very very dark. I am hoping to take my scope to either one of these places in the spring and summer for better viewing. Because right now, most the things I see are small and blurry. But again, I’m a total rookie here.

1. Mars is very tiny. I had a look last week with my VIxen VMC 110L (110 mm Cassegarin aperture). I could see some surface features. However, my 6 mm Ploessl only gives me 172x. I think for the 2020 Mars opposition I will buy a 5 mm wide-field planetary eyepiece.

 

2. You could use your Celestron zoom (it will give you magnifications of between 50x and 160x) to learn how high you can go on the moon under typical seeing conditions. I do not know if the Celestron zooms are any good. However, once you get a feeling for magnifications you could buy some fixed length eyepieces.

 

3. Maybe one thing worth considering. A 30 or 35 mm eyepiece will give you a slightly better true field of view (apparent field of view divided my the magnification). Typical Ploessl eyepieces have got 50 degree apparent field of view (so you would have 1 degree vs 1.4 degrees true field of view for the eyepiece 25mm versus 35 mm). Or you go the route via a wide field eyepiece.

 

4. I know, I know, we are still at solar  minimum and there are not many sunspots on the Sun at the moment. However, have you ever thought of becoming a solar observer?

 

5. Someone has mentioned a 9x50 finder. I however like red-dot finders.


Edited by Magnetic Field, 09 December 2018 - 07:52 AM.


#15 vtornado

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Posted 09 December 2018 - 02:29 PM

I am brand new to the world of cats too.

 

I had an 8 inch SCT a long time ago and did not like it.  My main beef was the field of view is too narrow.   Without goto, and in light pollution,

I wind up using my main scope to star hop, and at 2000 mm it is tough to star hop.  I am willing to live with 1250.  I also bought this

so I can carry it to a remote location to view.

 

If you are on a budget, my first eyepiece I would get is a 32mm plossl.   This will give you the widest total field of view at a low cost.

I also like to view stuff with a 1mm exit pupil.   I find this is a nice balance between brightness and magnification.

You can determine exit pupil by dividing the focal length of the eyepiece by the f ratio of the telescope.

Our C5s are f/10 so that meas a 10mm eyepiece.  You may find a 10mm plossl has too little eye relief to be comfortable.

 

 

You are going to have to learn how to collimate this scope.   When I picked mine up it was horrible.  Defucused stars looked like triangles.

I have it close now,  but not as good as I want it, but this is definitely a different beast to collimate than a newt.  

 

Another thing I noticed is this scope is terrible when you take it out from a warm house to 20 degrees F.   By the time the thermals started clearing up,

The corrector started frosting up.   There are threads here about wrapping the tube with insulation, I am definitely going to do this.   I don't want to buy

dew straps, and have to deal with batteries and wires.  It ruins the grab and go aspect of this scope.


Edited by vtornado, 09 December 2018 - 02:41 PM.


#16 Ptkacik

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Posted 09 December 2018 - 03:13 PM

Back in 2015, I asked the same question and after a couple hundred responses, I summarized it the following way. Of course the generalizations upset several people but Caveat Emptor.

Summary?

It seems that Maksutov Cassegrains are typically F15 and therefore very focused on high power viewing. At high powers, the Mak typically beats out the Schmidt Casegrain telescope (SCT).

The SCT appears to be no less optically refined than the Mak; however, at more like an F10, it is more of a generalized tool. It can reach a wider field of view as well as high powers (jack of all trades but master of none).

Both Maks and SCT's are wonderful designs giving up optical refinement of Newtonians and Apo refractors but beating those other designs with more aperture per dollar (v. the APO) or much more convenient packaging (v. the Newt).

There are also variables on details like cooling and collimation but I think the above is a pretty good summary.

Clear skies,
Peter

#17 Peter Besenbruch

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Posted 10 December 2018 - 09:26 PM

The cheap Synta made 5" Maksutov is not 5", more like 4.7" due to poor internal design.

 

The 3.5", 4", and newer 6" and 7" Maksutovs operate close to the claimed aperture.

 

I suspect, contra the claims of vtornado, that the cheap Maks are not all spherical. When you get virtually no trace of spherical aberration on a star test (on my 7" especially) at a size and f-ratio where you should see some, some surface isn't spherical.

 

SCTs offer shorter f-ratios, a bit larger baffle tubes per given size, and lower power with less vignetting. If you want the edge of the low power field to be sharp, you need the extra correction offered by the Celestron Edge or Meade ACF. SCTs also tend to be lighter weight.

 

Maksutovs, particularly of the Gregory style, collimate from the back, and only the back. You adjust while looking through the eyepiece. Once locked in, the collimation tends to hold for years, or decades, regardless of how it gets knocked around. It's a more rugged design.

 

Maksutovs use optical glass for the corrector, as opposed to float glass for the SCT. Thus, Maksutov optics have the potential to be smoother, and they often achieve it. This and the slightly smaller secondary (again, the 5" Mak is an exception) tend to make them a bit better planetary performers. Low power, such as it is, is better at the edge of the field in a Maksutov than a standard SCT.

 

For a long time people claimed that the thin SCT corrector allowed for faster cool down compared to similarly sized Maksutovs. Tube insulation has changed the equation a bit. If you insulate the tube, the thicker corrector of the Maksutov might turn out to be an advantage. Certainly, my insulated 7" Mak is a set up and go scope. My 3.5" is too small to worry about acclimation. Neither has needed collimation in years. My C8 needed collimation every 6 months, and I checked it more frequently.


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#18 Eddgie

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Posted 10 December 2018 - 09:42 PM

Once again, MCTs do not have to be f/15. Intes Micro made several f/10 models. 

 

Intes M 703 is f/10

Intes M 803 is f/10

Intes-Micro Alter is 150 f/10

Intes 1208 is f/10

There was also a 10" f/10.

 

So MCT does not have to be f/15.   


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#19 Hesiod

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Posted 11 December 2018 - 05:23 AM

As far as I remember Intes Micro made also f/6 Mak-Cass.
5" and 6" Synta MCTs are nominally f/12

#20 freestar8n

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Posted 11 December 2018 - 06:30 AM

It's important to distinguish what I prefer to call "spot Maksutov's" from other forms.  Many people refer to spot Maksutov's as "Gregory" type - but Gregory just popularized the idea with 6" versions - and Maksutov himself was aware of the idea of just aluminizing a spot on the back of the meniscus.

 

It's commonly thought that spot Maks can be easily made and will perform well because their spherical surfaces are easy to make - but the tolerances are so tight in the design that either additional tweaks to the spheres are needed in the end - or they are designed from the start with a fairly ellipsoidal primary.

 

If a spot mak is fairly large aperture - above 3" - and it isn't very long - and if its f/ratio is below 15 - it probably involves a significant asphere, probably on the primary.

 

The Meade mak7 is a classic example of this - with a very ellipsoidal primary - even though it is fairly slow at f/15.

 

But when you allow departures from the spot mak - and allow a separate secondary with its own curvature - everything becomes easier and you can go faster.

 

The 8" f/6 Intes mak cass appears to have a separate secondary - and additional correction lenses near the focal plane for imaging.  That's completely different from a spot mak.  At some point you lose the whole need for the meniscus - because you can make a cdk from the same basic design but without the front corrector.  Ellipsoidal primary, spherical secondary - and corrective lenses near the focus.

 

So - there are many myths associated with maks.  They aren't made from perfect spheres, they are hard to make well (hence the added cost), and they often have a fairly large secondary obstruction.

 

I bought a meade mak7 long ago for the same reason many people buy and like maks: They are somehow a cool concept - and some of us coveted the questar 7 years ago as some kind of ultimate 'scope.

 

In terms of practical differences when comparing say an 8" sct with 7" mak - the main thing is no need to collimate.  It should work out of the box.  But the mak would be less versatile if it is f/15.  I used to use the meade with a 55mm plossl - and had a reasonable low power and wide-ish field.  So it wasn't strictly very high power.

 

I later got a C11 and had both at the same time - and it was a good comparison because they were nearly identical focal lengths (105 vs. 110 inches) - and both performed near the diffraction limit.  So the only real difference was the mak was fainter at a given power.  I never had a compelling reason to use it over the C11.

 

Frank


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#21 Bill Barlow

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Posted 11 December 2018 - 12:48 PM

Once again, MCTs do not have to be f/15. Intes Micro made several f/10 models. 

 

Intes M 703 is f/10

Intes M 803 is f/10

Intes-Micro Alter is 150 f/10

Intes 1208 is f/10

There was also a 10" f/10.

 

So MCT does not have to be f/15.   

I-M also made a 6.5”/165mm f/11 MAK.  I owned one of these and it was excellent.

 

Bill


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#22 JohnH

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Posted 12 December 2018 - 10:35 AM

Once again, MCTs do not have to be f/15. Intes Micro made several f/10 models.

Intes M 703 is f/10
Intes M 803 is f/10
Intes-Micro Alter is 150 f/10
Intes 1208 is f/10
There was also a 10" f/10.

So MCT does not have to be f/15.

Most of the high-end Intes instruments of the Mak Cass variety were F10.

I know my m809 is. I've had a number of people look through it over the years, at RASC events, at Mt. Kobsu and at Table Mountain. Virtually all of them express surprise at how crisp and detailed the instrument performed at high powers, and one of my favorite tricks was to pull out a wide field eyepiece like a 60 mm or a 55, and show them that the contrast between a bright nearly full moon and the surrounding Stars was uch better than they expected. Also with the really great correction available in it feature objects are seen much further to the edge of the field than regular sets

#23 naramsin

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Posted 12 December 2018 - 03:09 PM

If a spot mak is fairly large aperture - above 3" - and it isn't very long - and if its f/ratio is below 15 - it probably involves a significant asphere, probably on the primary.

If this is true, then it would go a long way to explaining why my Apex 102mm (F12.7) projects a 102mm circle using the flashlight test. It might also explain why it doesn't seem to have any issues illuminating my 2" eyepieces. It's like the old (obviously wrong) theory about it being impossible for bumblebees to fly....

 

I'd appreciate any theories about why this is so. The Apex should have a smaller light circle, since it doesn't have the customary oversized primary of a proper Mak. And how can it support my 2" EPs without vignetting? If they used aspheres in the design, would those account for its performance? And shouldn't it be called something else, like an "Asphere Mak" or something? Wouldn't this have been some sort of breakthrough in optics?



#24 freestar8n

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Posted 13 December 2018 - 02:13 AM

If this is true, then it would go a long way to explaining why my Apex 102mm (F12.7) projects a 102mm circle using the flashlight test. It might also explain why it doesn't seem to have any issues illuminating my 2" eyepieces. It's like the old (obviously wrong) theory about it being impossible for bumblebees to fly....

 

I'd appreciate any theories about why this is so. The Apex should have a smaller light circle, since it doesn't have the customary oversized primary of a proper Mak. And how can it support my 2" EPs without vignetting? If they used aspheres in the design, would those account for its performance? And shouldn't it be called something else, like an "Asphere Mak" or something? Wouldn't this have been some sort of breakthrough in optics?

You wouldn't actually be able to tell anything is ellipsoidal by the flashlight test - but it may indicate if the aperture is reduced.  But you can tell that without a flashlight and just by looking at the scope.

 

Maks either have a meniscus in front that spans the full aperture - or it is greatly reduced - like in the meade mak7 and other, mostly high end maks.  And either way, it is paired with a primary that is often not a sphere.

 

It's perfectly fine in either case - if the meniscus fills the tube diameter - or if it is smaller and has a gap around it.  But you know immediately that if it fills the full diameter of the tube, the primary cannot be larger than the meniscus - and in that case the true aperture will be less than the meniscus size - because light diverges after passing through the meniscus - and that means the primary is the limiting aperture - and the effective aperture is smaller than the primary.

 

So it is optically fine to have it that way - but it would be incorrect to say the effective aperture of the scope is the diameter of the meniscus.  It won't be - and if the flashlight test is performed properly, the shadow image should be smaller than the meniscus to reveal that fact.

 

But it doesn't mean you have an "undersized" primary.  It just means the primary is determining the effective aperture of the scope - and it's the meniscus that is "oversized".  And "oversized" doesn't refer to some extra level of quality - it refers to the size of the unvignetted field.  One of the elements needs to be "oversized" in order for there to be no vignetting as soon as you go off axis.  It isn't oversized at all - it is just determining the size of the unvignetted field.  Just like setting the size of the secondary in an SCT or even a Newt.

 

Hope this makes sense-

 

Frank



#25 yellobeard

yellobeard

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Posted 13 December 2018 - 03:31 AM

Once again, MCTs do not have to be f/15. Intes Micro made several f/10 models. 

 

Intes M 703 is f/10

Intes M 803 is f/10

Intes-Micro Alter is 150 f/10

Intes 1208 is f/10

There was also a 10" f/10.

 

So MCT does not have to be f/15.   

 

And SCT's do not have to be F/10.. But to find a (commercially aviable) F/15 SCT will be a challenge.

But in theory, both optical systems can be perfectly optimized for a wide range of F/ratio's, you only must try to find someone who builds it,

because they need to be build from scratch.




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