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Maksuton-Newtonian vs Schmidt-Cassegrain

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#1 m00nless

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Posted 26 January 2013 - 09:16 AM

How would a SkyWatcher 190mm f/5.3 Maksuton-Newtonian compare to a Celestron 200mm f/10 Schmidt-Cassegrain?

#2 microstar

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Posted 26 January 2013 - 10:09 AM

Are you doing astrophotography? If so the Mak-Newt wins hands down. My SW 190MN is my main astrophotography workhorse. Very flat field and sharp stars to the edge of field while still reasonably fast and a FOV suited to a wide range of deep sky objects. I rarely observe with it visually so will let others comment on visual use.
...Keith

#3 coopman

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Posted 26 January 2013 - 10:51 AM

I would take the MN any day over a SCT. I do visual only.

#4 m00nless

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Posted 26 January 2013 - 12:28 PM

No astrophotography for now. Would there be a real reason to switch to a MN from a SCT for visual?

#5 JohnH

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Posted 26 January 2013 - 01:10 PM

Image scale is one reason I could think of, but the use barlows and short focus EPs level the playing field considerably.

#6 Cotts

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Posted 26 January 2013 - 01:29 PM

Visual only? The Mak Newt. The 190mm f/5.3 will have a much smaller central obstruction than the SCT - (around 20% rather than >than 30% for the SCT) which makes the changes to the diffraction pattern almost indistinguishable from an unobstructed telescope. Your planetary and Lunar viewing will be enhanced.

The f/5.3 focal ratio of the M-N will be better for wide field viewing than the f/10 of the SCT.

The two scopes are equally excellent for chromatic aberration.

I have an INTES 6" f/8 Mak Newt (16% central obstruction) which can run with any 6" refractor on the planet and is very much the equal of a 200mm SCT except for light grasp. The 190mm MN should be noticeably better than the 200mm SCT.

Dave

#7 HenryB

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Posted 26 January 2013 - 01:32 PM

The Mak-Newt gives a wider field and depending on what you observe, that may be an advantage. I have a 10" Mak-Newt and a C11 and enjoy both, but the wider field is nice on clusters.

Bryan

#8 Yu Gu

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Posted 26 January 2013 - 02:27 PM

I had both scope, as well as a TEC140 at the same time. The 190 was kept and the other two were sold. It's really a 185mm F5.4. The CO is 31% for the older version (mine) and larger for the newer ones. On my sample, the figure was exceptionally smooth and accurate, rivials any top maker. The planetary performance is a step above the TEC140, not to mention the light gathering. It's just not as beautiful a machine as a TEC. The C8 had an accurate but less smooth figure (due to high magnification of the secondary).

#9 rmollise

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Posted 26 January 2013 - 03:01 PM

No astrophotography for now. Would there be a real reason to switch to a MN from a SCT for visual?


The MNT is a fine telescope, but the SCT is a little more versatile. It works well at f/10, f/3.3, and f/6.3. It is as suited for high resolution planetary imaging as deep sky work. It's, very impotantly, got a short, relatively light tube that will not stress a mount. Finally, counteless accessories have been developed for the SCT over the last 40 years. ;)

#10 NHRob

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Posted 26 January 2013 - 03:46 PM

Yu Gu,
Which model 190 Mak-Newt do you have? Is it the Skywatcher brand?

#11 BillP

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Posted 26 January 2013 - 04:15 PM

Yu Gu,

How did you find that the thermal issues differed between the SCT and MN you had? Was one faster to acclimate than the other?

#12 titanio

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Posted 26 January 2013 - 04:43 PM

I prefer the MN to the SCT.
As for thermal issues, it is much better in my MN than in my C9 HD, the MN has a fan which make the telescope to be ready in a few minutes

Toni

#13 Yu Gu

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Posted 26 January 2013 - 05:00 PM

The one I have is the white version. It has a removable door at the back. I typically use a fan to force air in from the back and keep the focuser end open for the air to get out. It works great! I typically set the scope out at sunset and let the fan run for an hour and I haven't had any thermal issue at all! (unlike many other scopes I had). I live in West Virginia and the temperature can drop pretty quickly at night. I can see white ovals on Jupitor consistantly with the MN190, which was not the case for TEC140. The only issue is that I have not yet had a success to get my Denk II working properly with this scope...

#14 laconicsax

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Posted 26 January 2013 - 05:31 PM

The Mak-Newt has more advantages over the SCT than the other way around. As long as you have a mount that can handle it, I'd say go with the Mak-Newt.

#15 Eddgie

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Posted 26 January 2013 - 06:19 PM

The MNs have an excellent reputation as visual scopes but this is due to the fact that at f/6 the central obstruction can be kept very small.

The 190mm MCT you are looking at is sold usually as an astrograph, and while I could not confirm the Specs of the Skywatcher branded scope, the Orion 190mm f/5.3 has a rather large obstruction, which is almost always the case with astrographs.

The Orion version has a 64mm secondary obstruction so in fact, the secondary obstruction is about the same percentage (33%) as a C8.

And since a C8 has more aperture to start with, it should have a slight edge for deep sky and planets.

The MN will have the ability to provide quite a bit larger field, so will do better for large clusters and such, but there are not that many targets that won't fit into the field of a C8 with a 35mm Panoptic.

The MN also weighs in at a hefty 22 lbs. And being a Newt, it will not have the great ergonomics of a C8.

So, pick you posion. A larger field in a heavier (harder on the mount) and less ergonomic package (MN), or a compact scope that will do slightly better on planets and deep sky, will work on a light mount, and will have great ergonomics with an eyepiece that can always quickly be adjusted to the right angle.

Don't discount the ergonomics. This is the weak point of a GEM mounted Newt. Even if you have rotating rings, the eyepeice can sometimes get into uncomfortable positions. This is hardly ever an issue with a C8.

The question is do you mind the extra bulk and weight of the MN for the bigger field it can provide, or do you want the better deep sky and planetary performance that the C8 can provide.

#16 Jon Isaacs

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Posted 26 January 2013 - 07:35 PM

Don't discount the ergonomics. This is the weak point of a GEM mounted Newt. Even if you have rotating rings, the eyepeice can sometimes get into uncomfortable positions. This is hardly ever an issue with a C8.



In my experience, the ergonomics of an 8 inch F/5 Newtonian are still reasonable, seated viewing is possible even at the zenith. Effective rotating rings can be fashioned with some handiwork and Teflon.

In my mind, a standard Newtonian with a coma corrector is a worthy competitor to a Mak-Newt and has a few advantages such as fewer issues with dew, open tube promoting thermal equilibrium...

Jon

#17 maknewtnut

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Posted 26 January 2013 - 07:51 PM

My route to MN's was very similar to that of Yu Gu. I got my first because I couldn't afford a 4" apo to supplement my Ultima 8 (had my eyes on an AP Traveller at the time). It paid off. I then sold the MN56 and the C8 to obtain an MN76. That paid off too.

I later owned a TEC 140, and ran it side by side with the MN76. I sold that fine refractor too (because the advantages on both deepsky and high mag planetary were considerable).

The C8's attribute of size and weight is a very real issue to consider. However, trying to imply parity in image quality at faster focal ratios by simply screwing on a mass produced accessory is misleading. It has become widely accepted that quality will vary widely with C8's. What is not as widely known is that the same applies (if not more so) to the redcucer/correctors made for them.

#18 NHRob

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Posted 26 January 2013 - 09:50 PM

Hi Mark,
Didn't I sell you that first MN56?
Wish I still had it.
:rainbow:

#19 maknewtnut

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Posted 26 January 2013 - 10:39 PM

That's right Rob O.

I have another I built recently with Deluxe spec optics. I built it with a carbon fiber tube and Delrin primary cell and focuser block. Incredibly tight star images to very near the edge of the field at lower mags, and still sucks up magnification without flinching for planetary and double star observation....although I have to sell it because the stable is too full.

As for my previous post...Rod, sorry if it seems like I might pick on your replies now and then. The SCT is a good choice for many. However.....IMHO, playing them up as having no cons whatsoever is a gross disservice to those asking for opinions on the differences between them and other makes and/or design types. EVERY telescope has pros and cons, and attributes each person can weigh in level of importance to them.

#20 JohnH

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Posted 26 January 2013 - 11:02 PM

Hi Mark,
Didn't I sell you that first MN56?
Wish I still had it.
:rainbow:


Vancouver Telescope has an MN 66 with test papers around. If they are selling it or its being spoken for are questions I cant answer

#21 Patrick

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Posted 26 January 2013 - 11:05 PM

Visual only? The Mak Newt. The 190mm f/5.3 will have a much smaller central obstruction than the SCT - (around 20% rather than >than 30% for the SCT) which makes the changes to the diffraction pattern almost indistinguishable from an unobstructed telescope. Your planetary and Lunar viewing will be enhanced.



My 6" f/5 Mak Newt has a 32% central obstruction, so I seriously doubt that the f/5.3 has a 20% obstruction. It's even difficult to find standard commercial Newtonian's with central obstructions less than 25%.

Back to the question at hand...I spent a considerable amount of time comparing my C6 SCT with my 6" MN and ended up thinking that for planetary viewing the C6 SCT performed better. The 6" MN was close, but did not show quite as much detail. Of course for wide field work, the 6" MN excels. That's what it's designed for...wide flat fields.

One of the things you left out of your question though is 'which SCT'? The newer EdgeHD SCT's are quite a bit better than the standard SCT's in regards to flat fields and edge of field correction.

I'd like to reiterate one of the comments above also...a Mak Newt scope is a lot bigger than the SCT of the same aperture. My 6" MN is about 28" long while my C6 SCT is about 14" long. The case for the MN is 36" x 14" x 17" and weighs about 35 lbs with the scope in it. The C6 can fit in a small duffle bag. For that matter my EdgeHD 8" has a smaller foot print than the 6" MN and the EdgeHD 8" scope dramatically outperforms the 6" MN. Ergonomically, the MN is also cumbersome to use on an EQ mount while the SCT is quite comfortable. Ergonomics and comfort do matter, and make for a more enjoyable viewing experience.

Patrick

#22 Paul Hyndman

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Posted 27 January 2013 - 08:23 AM

My 6" f/5 Mak Newt has a 32% central obstruction, so I seriously doubt that the f/5.3 has a 20% obstruction. It's even difficult to find standard commercial Newtonian's with central obstructions less than 25%.


MNs designed for visual usage place focus very close to the tube wall, squeaking by with as small a (fully illuminated) secondary as possible. Placing focus so close to the OTA presents a dilemma for imaging and bino-viewing though, usually requiring a relay lens (or Barlow/Powermate etc) to sufficiently "draw out" the image enough to reach focus. To accommodate these uses, some later designs bumped focus further from the tube by reducing the distance from the primary, necessitating the use of a larger secondary, hence a larger CO.

While nice images can be attained using a MN, its greatest prowess (IMHO) is attained when optimized for visual use.

Paul

PS: I loved my (visually optimized) MN86 but, alas, eventually parted with it to make room for other equipment (it was built like a tank, and almost as pretty!)

#23 orion61

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Posted 27 January 2013 - 02:47 PM

If optical quality is the same I'll go the SCT,
The Schmidts built in about the last 10 years or so
are pretty consistant

#24 spencerj

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Posted 28 January 2013 - 10:19 AM

Back to the question at hand...I spent a considerable amount of time comparing my C6 SCT with my 6" MN and ended up thinking that for planetary viewing the C6 SCT performed better. The 6" MN was close, but did not show quite as much detail. Of course for wide field work, the 6" MN excels. That's what it's designed for...wide flat fields.


I have wondered for a while how the optics in the ES mak newts stacked up to the Intes Micro mak newts. For me, this post helps answer that question. When comparing scopes of the same aperture, the better optics will win. It sounds like most of the C6s have good optics, but as a general rule, I would be very surprised if the average C6 could routinely beat the average Intes Micro mak newt on planetary performance.

#25 Patrick

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Posted 28 January 2013 - 02:59 PM

It sounds like most of the C6s have good optics, but as a general rule, I would be very surprised if the average C6 could routinely beat the average Intes Micro mak newt on planetary performance.



It would be fun to do a side by side. I see the MN66 has a 20.4% central obstruction, so I'm guessing it would do very well.

Patrick






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