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Meade 6" Maksutov-Caseagrain vs Meade 6"ACF

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#1 DeltaFlyer

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Posted 21 September 2018 - 10:11 PM

I currently have a Meade 10" Starfinder on an Equatorial Mount (motor not working) and a 14" Skywatcher GoTo Collapsible, I have been looking for a more portable/affordable grab and go/travel scope so I have been looking at the new Meade LX85 scopes. I have pre-ordered the 6" Newtonian because of the price but have reconsidered, maybe the 6" Maksutov-Caseagrain. I am uncertain of the difference between that scope and the Meade 6" ACF. My intentions are to begin doing some Astrophotography and to also have portable scope I could use on road trips, where I might take  my 10 or 14" to a dark sky site but not travel cross country with them. I have reconsidered my choice of the 6" Newtonian in favor of the Mak or ACF because they would be different from my Newts and compliment them, and be better on planets and from what I've read the Mak has better contrast and perhaps better detail in viewing planets. My 10" weighs about 23-24 lbs so I'm hoping to mount it on the LX85 mount for visual use as well and use the Maksutov-Cassegrain or ACF for AP. So I see the difference in focal length and focal ration, besides that, is there a difference? They both are the same price. Will the Mak-Cass show more contrast? Visually or photographically will I see a difference other than FOV? Thank you for opinions, Lance.



#2 Taosmath

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Posted 22 September 2018 - 12:18 AM

The Maksutov is F12, the ACF is F10 and the newtonian F5. I'm not a photographer, but I've always been told that in AP high F no. means long focal length means much higher demands on the mount.  This would imply the Newt would be your best choice for getting into AP.  However at F5 the Newt would probably show coma , so an alternate approach might be to get the ACF (The ACF stands for advanced Coma Free, I believe) with a F6.3 focal reducer which would take you back down to a 950mm or so focal length which should be easier to handle than the native 1500 (or 1800 for the Mak).

 

However I expect the experienced AP's will weigh in recommending the 80mm APO from that range.


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#3 aeajr

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Posted 22 September 2018 - 11:51 PM

If this is AP focused then you would be best served to post it in the imaging forums. 



#4 DeltaFlyer

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Posted 23 September 2018 - 01:59 PM

Not necessarily AP, but actually trying to understand the difference between these to scopes. I understand that they have different focal lengths and different f/rations, is that the extent of their differences? I plan on using it for visual as well as begin AP, but I will do much more observing than AP. 



#5 TareqPhoto

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Posted 01 October 2018 - 06:45 AM

To be honest, i am new in this, started last year, i learnt few things and i try to keep it as simple as that even if they are not a fixed facts maybe or not necessary true always.

 

1. The faster the lens the better it is for AP which needs long exposures, most targets faint or dark need longer exposures, and for that the fast f ratio it will help you for that, just the size of aperture will determine you what size of the target you need combined with f ratio.

 

2. The larger or longer focal length the scope, the better it is for planetary, sure you can do with shorter focal length, but here the details in planets will be served better if you go longer focal length, mostly with fast f ratio it won't get long focal length enough unless you go with very large scope over 20", and those if they have slow f ratio will have a bit longer focal length but it will be headache for DSO imaging as they are slow so you will take very very long time to do mainly if most those targets are faint.

 

So, from above i felt like i got an idea which scopes to buy, but there is always the problem of accessories that may give you more options, like if you want fast scope then most refractors and Newtonian will give you that, but there is a tool such as Starizona Hyperstar that will transfer F10 SCT into F2 so then now even SCT is a big option, and many go this way because they want one scope for many targets or multitasking, also if you use reducers sometimes even slightly slow scopes can be used then, so instead of having only 2 types of scopes now you may have 4-5 types.

 

I am still learning, and have few scopes [3 if i include the guide scope of ST80], more will come later, and scopes alone aren't the only items i need for APO, in fact an astro cooled camera and filters also helped in AP for me although i am not done much yet, in fact the scope is like a car, you choose the car according to the targets you want to do.



#6 Bill Barlow

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Posted 01 October 2018 - 10:40 AM

The ACF optics are very sharp if well collimated while the Mak will also have very good optical quality if you get a good sample.  I owned the Meade 6”ACF and it was super sharp.  But it had a large secondary obstruction around 44% while the Maks is around 33%, so the MAK might be better for showing a tad more contrast on planets.  

 

One other difference, the Mak is collimated by adjusting the primary mirror while the SCT is done adjusting the secondary mirror.  Hope this helps.

 

Bill


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#7 DeltaFlyer

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Posted 01 October 2018 - 11:43 AM

Thanks again to everyone for your input, helps to hear other people’s ideas. Bill, think that is where I was heading, towards the Mak.

Lance



#8 macdonjh

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Posted 01 October 2018 - 12:12 PM

Lance,

 

I have used both Maks and SCTs visually.  I didn't notice that much difference in the view, provided both scopes were set-up for best performance.  That means both scopes are collimated well, sufficiently cooled or otherwise thermally stable, no dew on the corrector plates, etc.  The focal lengths of 6" Maks (assume f/12) and SCTs are pretty close, so the true field of view will be similar (1o for the SCT, 0.9o for the Mak with a 32mm Plossl).  Either the 6" SCT or the 6" Mak will be small and light for travel and easily packed.  Both have enough aperture, in my opinion, to provide pleasing views of many deep sky objects and good detail for solar system objects.  Full disclosure: I don't really like 4" scopes, I find their images too dim and the "reach" too limited (my first scope was a 4" Mak, but I don't use it any more except for white light solar).  I prefer a 6" SCT to a 4" refractor.  

 

As for differences in the optical design between the Mak and SCT: both scopes are catadioptric, so each has both mirrors and refractive elements.  The Mak has a relatively thick lens in the front that refracts the incoming light, then the primary mirror focuses the light cone on the secondary mirror (that silver spot on the back side of the front corrector), and finally the secondary mirror magnifies the image and reflects the light cone toward your eye piece.  The SCT works in basically the same way: a relatively thin corrector refracts the incoming light, the primary mirror focuses the light cone on the secondary mirror (in a plastic holder in the center of the corrector), and the secondary mirror magnifies the image and reflects the light toward your eye piece.  In general, Maks are heavier than SCTs, but there might be exceptions(?).  Both designs have pretty slow focal ratios (f/10 for SCTs and f/12 or f/15 for Maks).  For visual observing that means that high magnification can be achieved with longer focal length eye pieces (for example, that 20mm eye piece that I would guess gives you about 63x in your 10" Starfinder will give you 76x in a 6" SCT and 91x in a Mak), but at the expense of field of view (0.8o for the Starfinder, 0.65o in the SCT and 0.55o in the Mak assuming a 20mm Plossl).  Photographically, you'll at least need to have much longer exposures with the slower SCT and Mak than you would with a faster Newtonian or refractor.

 

I think aeajr is right about any photography questions you have, make a "parallel post" in the imaging forum.  However, since you're here, I'll tell you what I've heard.  But be warned, I do not image.  Either the Mak or SCT should be fine for lunar and planetary imaging.  I have zero experience with Meade mounts, so I have no idea what to expect using an LX85 for any kind of photography.  The Celestron AV-X and Orion Sirius are being used by members here for solar system photography with good results.  For deep sky objects requiring long exposures, I think you'd be better served with a 6" Newtonian at f/5 or f/4.  The amount of time required to collect enough light for a pleasing image with an f/10 (SCT) or f/12 (Mak) system may be beyond the ability of an LX85 mount to track accurately.


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#9 DeltaFlyer

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Posted 01 October 2018 - 06:55 PM

Thanks macdonjh. I appreciate the input, especially from someone with experience both these scopes. As far as the LX85. I don't know either. I did talk to someone who was able to test one prior to their release and he seemed think highly of the mount.



#10 macdonjh

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Posted 01 October 2018 - 09:16 PM

Perhaps do some lurking in the beginning imaging forum here.  See if there's any chatter about the Meade LX85.  If not, ask the question.  It's been said before, this is a Celestron-centric website: there is much more discussion of Celestron scopes and mounts than Meade.  No idea why, but it is.


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#11 DeltaFlyer

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Posted 01 October 2018 - 10:25 PM

Thanks, do a lot of lurking because most of my questions have already been asked and answered. There is so much knowledge already posted here. What an amazing resource, wish I had found it sooner.



#12 SeattleScott

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Posted 01 October 2018 - 11:08 PM

The LX85 weighs 23 lbs, so this idea that it can handle 33lb OTAs seems like it deserves a good laugh. By comparison the Celestron VX weighs 35lb and is rated for 30lbs. So unless you believe this Meade mount is engineered light years better than a comparable Celestron mount, the rated weight for the Meade mount is most likely a joke.

However your OTA is not 33lb. More like 24lb you say. That is really pushing it for a 23.2lb mount. Now, my Japanese mount that originally retailed for about $2,000 is 26lb and rated for 26.5lb. And it does ok with my 26lb 10” reflector. So it could possibly work, if Meade’s mount is engineered as well as a Japanese mount. If my Meade LXD55 is any indication, I wouldn’t do it.

Scott
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#13 carolinaskies

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Posted 02 October 2018 - 09:46 AM

The LX85 is rated at 33lb capacity, be aware that even though your 10" can be used on it you'll be dealing with balance issues and ergonomic issues viewing through the eyepiece as you change objects. 

6" SCT and Mak's are ideal grab and go for objects from planetary size up to star clusters.  For photographic they are OK, but the LX85 is an unproven AP platform being newly introduced which may or may not have issues.  Due to this I have the following suggestion, look at opting for maybe a dual saddle system and a widefield refractor to pair with the Mak or SCT for visual and for starting any serious AP in general.  

Planetary imaging with the SCT/Mak are simple due to the short imaging times involved.  I would use something like https://astronomy.to.../field_of_view/  to give you a good reference point of field of view between the different scopes you own.  Put in the basic information and choose one eyepiece/camera and you'll see in general what you gain/lose for the different telescopes. 

Both SCT/Mak should retain good collimation if stored/transported suitably.  Unlike a Newtonian they don't go off collimation(once set well) unless treated very roughly. 

General physical differences between the SCT-Mak - Weight, focal length with the Mak being heavier (9.14/12.7)  and just a tad longer.  

The SCT will result in slightly brighter images because of the shorter FL while the Mak will provide higher magnification for the same size eyepiece.  Neither scope is going to push observing limits in average skes so you'll likely be using 10mm-24mm eyepieces most of the time unless you have really good conditions. 

Given the equipment your currently have either will be a larger change in visual experience and ergonomic use.  The folded design makes these very fun without having to go through contortions as you go from horizon to zenith.  

FWIW if you're looking at a grab and go setup with SCT/MAK and future LIMITED photographic use you might consider the new LX65 with either of these.  The ease of setup will be easier than the LX85 and give optional OTA use(though not your 10").   

 



#14 Douglas Matulis

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Posted 02 October 2018 - 05:28 PM

One other thing to consider...  The front element of a Mak is spherical whereas an SCT has a complex curve that is matched to the primary mirror.  The process to make SCT optics certainly has a small margin of error compared to the simple spherical elements in a Mak.  What does this mean in practical terms?  Maybe not much.  But my experience with owning and using several samples of each type over the years is that Maks tend to be generally consistently good across a given sample size.  SCTs can be equally good, it is just that what I have noticed is that when a SCT is manufactured good, the views are awesome.  I have just seen more subpar SCT's than maks in my 30 years of observing.  SCTs tend to be really good or really bad. Now I do believe some of this is due to collimation.  SCTs are more sensitive to misalignment of optics. I don't believe they hold collimation as well as Maks and I thinks lots of SCT owners tend to not collimate because it requires more time and care to get it right than say collimating a Newtonian reflector.  Well, looking back over what I just have written, I'm not sure I said anything helpful.  So, I have always thought of it this way.  If I am primarily interested in viewing planets, moon, sun, double starts I use a Mak.  If I am interested in everything in the night sky and maybe even feel some AP is in the future and I can have only one scope, it's an SCT for me.


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#15 skyjim

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Posted 02 October 2018 - 06:58 PM

I agree with the above post but a 5" scope is limited for deep sky so my vote would be the mac, the amount of outer field curvature in the SCT will be no-were as good as the flat field in the mac.



#16 carolinaskies

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Posted 02 October 2018 - 07:24 PM

One other thing to consider...  The front element of a Mak is spherical whereas an SCT has a complex curve that is matched to the primary mirror.  The process to make SCT optics certainly has a small margin of error compared to the simple spherical elements in a Mak.  What does this mean in practical terms?  Maybe not much.  But my experience with owning and using several samples of each type over the years is that Maks tend to be generally consistently good across a given sample size.  SCTs can be equally good, it is just that what I have noticed is that when a SCT is manufactured good, the views are awesome.  I have just seen more subpar SCT's than maks in my 30 years of observing.  SCTs tend to be really good or really bad. Now I do believe some of this is due to collimation.  SCTs are more sensitive to misalignment of optics. I don't believe they hold collimation as well as Maks and I thinks lots of SCT owners tend to not collimate because it requires more time and care to get it right than say collimating a Newtonian reflector.  Well, looking back over what I just have written, I'm not sure I said anything helpful.  So, I have always thought of it this way.  If I am primarily interested in viewing planets, moon, sun, double starts I use a Mak.  If I am interested in everything in the night sky and maybe even feel some AP is in the future and I can have only one scope, it's an SCT for me.

You have your details wrong.  The front corrector on a Mak is not as simple to manufacture. It's a thicker curved glass(matching the primary) which takes more to produce than the 'weak' correction on an SCT which essentially straightens out the light path to reduce spherical aberation.  The SCT corrector is thinner and much easier to make overall because it provides a much more mild correction than a Mak corrector. An SCT corrector is not fully ground to the shape of the primary but rather at the center of the curvature.   

On the commercial Mak's the secondary is a mirror coating on the reverse of the corrector which is also why these Mak's have to be collimated via the primary. They save money these small Maks as they don't have to grind the corrector on the 6" and smaller Maks to match the primary like they do in the larger versions. At F/12-F/15  a Mak is less sensitive to collimation errors which is the advantage of long focal length equipment in general. 

An SCT uses a convex secondary whereas the Mak uses a spherical design.  Large Mak's are expensive due to the thick glass and spherical secondary ground into the corrector itself. This is why there are large SCTs up to 16" off the shelf but Mak's tend to stick under 8".   If you had to grind every corrector plate separately to create a matched secondary it would be quite time consuming.  And also why commercial Mak's aren't made faster.  A scientific grade Mak on the other hand would have a specially ground secondary precision matched to the primary and add considerable cost.  

As far as holding collimation, as I state above, unless either Mak/SCT is mishandled they are NOT likely to lose collimation.  That's just a plain false assumption and online fairy tale.   While some people claim it is necessary to use very expensive laser alignment tools, this is entirely false and unless a telescope was completely dissasembled and not properly marked and not gotten back to in years so stuff was misplaced it's rather miniscule chance such drastic techniques ever are necessary.  Of course I think it's like so many things, it's easy to make people with deep pockets believe an expensive gadget will provide the magical outcome when just basic knowledge and knowhow will accomplish the same without such expense.  More often, misunderstood tube current issues have misled owners of SCTs to chase after collimation issues blaming alignment rather than the actual source. 

Currently I own two 8" SCTs, one F/10 the other F/6.3.  I have an 11" SCT and 16" SCT and I have a 90mm Mak.  I wouldn't mind having the 6" Mak the OP is considering as it would fit nicely with my equipment I believe.  The 6" SCT on the other hand wouldn't gain me anything as an 8" is about as heavy as the 6" Mak.  



 


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#17 Bill Barlow

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Posted 02 October 2018 - 08:22 PM

The LX85 is rated at 33lb capacity, be aware that even though your 10" can be used on it you'll be dealing with balance issues and ergonomic issues viewing through the eyepiece as you change objects. 

6" SCT and Mak's are ideal grab and go for objects from planetary size up to star clusters.  For photographic they are OK, but the LX85 is an unproven AP platform being newly introduced which may or may not have issues.  Due to this I have the following suggestion, look at opting for maybe a dual saddle system and a widefield refractor to pair with the Mak or SCT for visual and for starting any serious AP in general.  

Planetary imaging with the SCT/Mak are simple due to the short imaging times involved.  I would use something like https://astronomy.to.../field_of_view/  to give you a good reference point of field of view between the different scopes you own.  Put in the basic information and choose one eyepiece/camera and you'll see in general what you gain/lose for the different telescopes. 

Both SCT/Mak should retain good collimation if stored/transported suitably.  Unlike a Newtonian they don't go off collimation(once set well) unless treated very roughly. 

General physical differences between the SCT-Mak - Weight, focal length with the Mak being heavier (9.14/12.7)  and just a tad longer.  

The SCT will result in slightly brighter images because of the shorter FL while the Mak will provide higher magnification for the same size eyepiece.  Neither scope is going to push observing limits in average skes so you'll likely be using 10mm-24mm eyepieces most of the time unless you have really good conditions. 

Given the equipment your currently have either will be a larger change in visual experience and ergonomic use.  The folded design makes these very fun without having to go through contortions as you go from horizon to zenith.  

FWIW if you're looking at a grab and go setup with SCT/MAK and future LIMITED photographic use you might consider the new LX65 with either of these.  The ease of setup will be easier than the LX85 and give optional OTA use(though not your 10").   

 

If the f/12 Mak and f/10 SCT use about the same power, the image will be the same brightness since the exit pupil will be the same.  Image quality?  Depends on the quality of the optics and collimation.  But if you use the same eyepiece in both, then the SCT should be very slightly brighter due to the shorter focal length and lower magnification and larger exit pupil.  

 

Bill



#18 TareqPhoto

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Posted 03 October 2018 - 01:19 AM

If the f/12 Mak and f/10 SCT use about the same power, the image will be the same brightness since the exit pupil will be the same.  Image quality?  Depends on the quality of the optics and collimation.  But if you use the same eyepiece in both, then the SCT should be very slightly brighter due to the shorter focal length and lower magnification and larger exit pupil.  

 

Bill

Yes, i did test my Mak viewing planets, and i saw planets from SCT only C9.25 and Meade 10" i think, both giving me brighter view of planets than my Mak f15, not sure if i use a reducer if available with my Mak it may give me brighter view as well or no.

 

I will try to use my ST80 and use say 3x for example to reach f15 and see how bright or dark it will be, but i also have 8" Newtonian that i didn't use yet, it has f5, so if i use 2x or 3x for example to reach f10-f15 how that will be, all to be tested one day i hope soon.



#19 Bill Barlow

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Posted 03 October 2018 - 09:41 AM

Try and use eyepieces that will give about the same magnification and exit pupil in each scope.  Then see how each scope compares to how bright objects are.

 

Bill



#20 TareqPhoto

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Posted 03 October 2018 - 09:56 AM

Until now i don't have special eyepieces, only the ones that come with the scopes, i used the eyepiece that came with the Mak, later when i will use the Newtonian then i will try the eyepiece came with it, also i bought one eyepiece that to give very very high magnification, but it wasn't that great much on Mak, kind of make it much darker a bit and no more details.



#21 Douglas Matulis

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Posted 03 October 2018 - 01:41 PM

You have your details wrong.  The front corrector on a Mak is not as simple to manufacture. It's a thicker curved glass(matching the primary) which takes more to produce than the 'weak' correction on an SCT which essentially straightens out the light path to reduce spherical aberation.  The SCT corrector is thinner and much easier to make overall because it provides a much more mild correction than a Mak corrector. An SCT corrector is not fully ground to the shape of the primary but rather at the center of the curvature.   

On the commercial Mak's the secondary is a mirror coating on the reverse of the corrector which is also why these Mak's have to be collimated via the primary. They save money these small Maks as they don't have to grind the corrector on the 6" and smaller Maks to match the primary like they do in the larger versions. At F/12-F/15  a Mak is less sensitive to collimation errors which is the advantage of long focal length equipment in general. 

An SCT uses a convex secondary whereas the Mak uses a spherical design.  Large Mak's are expensive due to the thick glass and spherical secondary ground into the corrector itself. This is why there are large SCTs up to 16" off the shelf but Mak's tend to stick under 8".   If you had to grind every corrector plate separately to create a matched secondary it would be quite time consuming.  And also why commercial Mak's aren't made faster.  A scientific grade Mak on the other hand would have a specially ground secondary precision matched to the primary and add considerable cost.  

As far as holding collimation, as I state above, unless either Mak/SCT is mishandled they are NOT likely to lose collimation.  That's just a plain false assumption and online fairy tale.   While some people claim it is necessary to use very expensive laser alignment tools, this is entirely false and unless a telescope was completely dissasembled and not properly marked and not gotten back to in years so stuff was misplaced it's rather miniscule chance such drastic techniques ever are necessary.  Of course I think it's like so many things, it's easy to make people with deep pockets believe an expensive gadget will provide the magical outcome when just basic knowledge and knowhow will accomplish the same without such expense.  More often, misunderstood tube current issues have misled owners of SCTs to chase after collimation issues blaming alignment rather than the actual source. 

Currently I own two 8" SCTs, one F/10 the other F/6.3.  I have an 11" SCT and 16" SCT and I have a 90mm Mak.  I wouldn't mind having the 6" Mak the OP is considering as it would fit nicely with my equipment I believe.  The 6" SCT on the other hand wouldn't gain me anything as an 8" is about as heavy as the 6" Mak.  



 

Thanks for the correction Paul.  I was always told the corrector on an SCT had a complex curve, neither convex or spherical, and that it was difficult to get right.  Celestron, I believe it was maybe Meade I don't know for sure, was the first to develop a process to consistently produces these correctors.  Even so, the tolerances needed are more precise and the corrector plate and primary were a matched set.  At least that is what I was told and I can't remember who or where I might have read it, maybe here on cloudynights or Astromart or sci.astro.amateur.  While a Mak has a thicker piece of glass, it is still just a spherical curve to grind and was told that was easier to figure. But I stand corrected.



#22 davidc135

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Posted 03 October 2018 - 04:27 PM

I think, Doug, that you're not so far off.

I'd say they are demanding in different ways. Mak correctors need thick, high quality glass with thickness and radii controlled to a fine tolerance but with the huge advantage of spherical surfaces. Schmidt correctors use glass which costs peanuts but require complex aspheric figures that can readily be made to a fair standard but which are difficult to consistently make to a premium standard. Why are there no premium Sct makers?

 

So Scts are a good design for small, medium and large aperture scopes of an average, decent standard. Maks come into their own as high grade, medium aperture systems but give way in larger sizes to all mirror Cassegrains such as RC and CDKs etc

 

Schmidt plates will be more strongly correcting than those of Maksutovs of the same aperture as Scts are faster systems. 

 

David


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#23 carolinaskies

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Posted 03 October 2018 - 08:52 PM

Thanks for the correction Paul.  I was always told the corrector on an SCT had a complex curve, neither convex or spherical, and that it was difficult to get right.  Celestron, I believe it was maybe Meade I don't know for sure, was the first to develop a process to consistently produces these correctors.  Even so, the tolerances needed are more precise and the corrector plate and primary were a matched set.  At least that is what I was told and I can't remember who or where I might have read it, maybe here on cloudynights or Astromart or sci.astro.amateur.  While a Mak has a thicker piece of glass, it is still just a spherical curve to grind and was told that was easier to figure. But I stand corrected.

Celestron developed a process of spinning a heated glass blank against a master to create an aspherical corrector, this heralded the era of the successful commercial SCT. 

Correctors are paired with primary mirrors in testing so that they reduce spherical abberation.  While such correctors are not highly hand figured as in custom telescopes costing significantly more by several factors, they are paired in such a manner to produce an acceptable result.  They may not be NASA satellite optic level, but then they are far better performers in the experience of thousands of owners.   

Mak-Cass mirrors are a reverse curve meniscus 10% the thickness of the aperture so you have a large hunk of glass which must be countered in the mount balancing design and one of the major factors in not making very larger Mak-Cass's. As the glass gets thicker to mimic the curve of the primary it becomes much harder to manufacture as well.  I believe a similar match-testing methodology is also used to pair Mak-Cass telescope optics.  Since most Mak/Cass designs are F/12-F/15 the tube length becomes another factor as the size increases.  The 7" Meade LX200 Mak is 3 inches longer than the 8" SCT and significantly heavier(8lbs) while the OTA is the same diameter.   

The Mak long focal length like any long focal length telescope tends to hide errors in figure so indeed the meniscus is somewhat 'easier'.  As focal ratio speed increases more precision in optical design becomes necessary to achieve flatness of field and reduction of Coma.  The ACF and Edge modern SCTs now approach the issue in different ways to achieve similar results.  Meanwhile the Mak-Cass is stuck at long FL so it will remain relegated to limited AP and narrower field visual use. 

But when you look back 60 years we are well ahead of the game compared to our grandfathers who had far fewer choices in telescope size which dictated specific mount designs.   Until Questar created it's little telescope mounts were large, cumbersome, and limited in tracking functionality.  Large clock drives and heavy gears along with long focal length refractors and newtonians made trekking out under the skies much more difficult.  There really weren't 'grab n go' designs until the Questar or if you built a 10" Dobsonian.  

Now we can buy 90mm-200mm grab n go scopes that can be setup and used in a fraction of the time.  Long live both Mak and SCT!   

  

   


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#24 DeltaFlyer

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Posted 03 October 2018 - 10:30 PM

The LX85 weighs 23 lbs, so this idea that it can handle 33lb OTAs seems like it deserves a good laugh. By comparison the Celestron VX weighs 35lb and is rated for 30lbs. So unless you believe this Meade mount is engineered light years better than a comparable Celestron mount, the rated weight for the Meade mount is most likely a joke.

However your OTA is not 33lb. More like 24lb you say. That is really pushing it for a 23.2lb mount. Now, my Japanese mount that originally retailed for about $2,000 is 26lb and rated for 26.5lb. And it does ok with my 26lb 10” reflector. So it could possibly work, if Meade’s mount is engineered as well as a Japanese mount. If my Meade LXD55 is any indication, I wouldn’t do it.

Scott

Scott, I had originally heard the LX85 mount was 19 lbs, now with more research I see that this weight includes the counter weight and the Celestron  Advance VX head weight does not include the counter weight, so now I see the discrepancy and I am now really concerned with the LX85's ability. It may be able to handle any of the 6" OTA but not my 10". Thanks.

Also all of the other posts about the differences between SCT and Maks is incredibly informative.


Edited by DeltaFlyer, 03 October 2018 - 10:34 PM.


#25 Asbytec

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Posted 04 October 2018 - 04:21 PM

Mak-Cass mirrors are a reverse curve meniscus 10% the thickness of the aperture so you have a large hunk of glass which must be countered in the mount balancing design and one of the major factors in not making very larger Mak-Cass's. As the glass gets thicker to mimic the curve of the primary it becomes much harder to manufacture as well.  I believe a similar match-testing methodology is also used to pair Mak-Cass telescope optics.  Since most Mak/Cass designs are F/12-F/15 the tube length becomes another factor as the size increases.  The 7" Meade LX200 Mak is 3 inches longer than the 8" SCT and significantly heavier(8lbs) while the OTA is the same diameter.   

As you know, the purpose of the meniscus is to generate higher order spherical which is added to the lower order (opposite sign) of the primary. When well executed, the RMS can be quite good even though it's not possible without an aspheric surface to fully correct the higher order spherical from the meniscus. Even at some 0.4 PV residual HSA, the scope is still diffraction limited. At larger apertures, this higher order spherical becomes exponentially significant and cannot be balanced by adding lower order spherical of the primary. This form of correction also affects and can be seen in the star test (I think for the better).

 

https://www.telescop...n_telescope.htm

 

Maksutov-Cassegrain star test (Fig 189 at bottom)

https://www.telescop...k_spherical.htm


Edited by Asbytec, 04 October 2018 - 04:39 PM.



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