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Equipment Discussions >> Cats & Casses

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Patrick
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Reged: 05/16/03

Loc: Franklin, Ohio
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: Cotts]
      #5645257 - 01/26/13 11:05 PM

Quote:

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

Edited by Patrick (01/26/13 11:40 PM)


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Paul Hyndman
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Reged: 07/13/04

Loc: Connecticut Shoreline USA
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: Patrick]
      #5645598 - 01/27/13 08:23 AM

Quote:

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!)


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orion61

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Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: Paul Hyndman]
      #5646197 - 01/27/13 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


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spencerj
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Reged: 11/17/04

Loc: Londonderry, NH
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: Patrick]
      #5647741 - 01/28/13 10:19 AM

Quote:

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.


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Patrick
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Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: spencerj]
      #5648416 - 01/28/13 02:59 PM

Quote:

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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RogerRZ
Whatta you lookin' at?
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Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: Patrick]
      #5648466 - 01/28/13 03:19 PM

My MN65 is listed as having a 26% CO, along with a .97-ish Sthrel. I don't know if this is average for the breed (they seem quite scarce), but it does throw up very nice views that are more similar than different to my 2012 vintage C8.

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JohnH
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Reged: 10/04/05

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Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: RogerRZ]
      #5648927 - 01/28/13 06:36 PM

Quote:

My MN65 is listed as having a 26% CO, along with a .97-ish Sthrel. I don't know if this is average for the breed (they seem quite scarce), but it does throw up very nice views that are more similar than different to my 2012 vintage C8.




My old MN-61 with its 18% obstruction. The MN-76 it replaces has a 7.1" clear aperture with just a 1.125" obstruction, making for 15.8% obstruction, a fair improvement but the increase in size is more noticed.


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Patrick
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Reged: 05/16/03

Loc: Franklin, Ohio
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: JohnH]
      #5649478 - 01/28/13 11:24 PM

Quote:

My old MN-61 with its 18% obstruction. The MN-76 it replaces has a 7.1" clear aperture with just a 1.125" obstruction, making for 15.8% obstruction, a fair improvement but the increase in size is more noticed.




I always wonder what size the 100% field illumination is with scopes like these. If I had to guess, it's pretty small. That's perfectly fine for planetary work, but aren't these mainly visual scopes?

Patrick


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jsrj98
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Reged: 02/21/08

Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: Patrick]
      #5649656 - 01/29/13 02:44 AM

Quote:

I always wonder what size the 100% field illumination is with scopes like these. If I had to guess, it's pretty small. That's perfectly fine for planetary work, but aren't these mainly visual scopes?





The two Mak-Newts (MN56, MN55) I've owned were fine visual instruments, but had serious limitations for imaging. I loved both scopes, and claimed I'd never sell them-- but ended up doing that in both cases. I also vowed I'd never buy a SCT-- and recently did just that. I've had my EdgeHD 8 for less than a week now, but WOW, what a great scope.

The MN55 wouldn't even come to focus with a new filter wheel I purchased, so replaced it with an MN55. It had more back focus, but when I changed cameras to one with an APS sized chip, the illumination was poor. While I could correct the image with flats, I couldn't get over the fact that I was losing so much data. Without flats, there's no way to make an acceptable image with a Mak-Newt IMO-- and I did that for years with them. I eventually moved on to smaller ED refractors and APO's (90mm to 100mm).

From a visual perspective, for me actually looking thru the APO was always a more pleasing experience than with my Mak-Newts. With them I was always fighting cool down issues (and the MN55 had a fan), plus they are bulky and heavy for their aperture. I never owned a Nagler at the same time as my Mak-Newts, but I can't image they would come close to fully illuminating a 22mm Nagler, let alone a 31mm.

When I decided I wanted more aperture than my smallish APOs could give me (but still have the same viewing experience with a Nagler) I bought an EdgeHD 8. Because I'd read nothing bad about one, I felt confident I'd probably get good to excellent optics. Mine shows a very good star test, and so far I'm extremely happy with the decision. When Celestron ships my dedicated reducer, I suspect I'll be even happier.


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orion61

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Reged: 10/20/07

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Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: jsrj98]
      #5649831 - 01/29/13 08:17 AM

If you look back a couple pages there is quite an exhaustive
thread about central obstruction and images and it doesn't seem to degrade the views nearly as much as people believe it does. A good example is the Meade RCX, fantastic optics with a larger secondary, brightness well, that may be a different story.


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Patrick
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Reged: 05/16/03

Loc: Franklin, Ohio
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: jsrj98]
      #5649900 - 01/29/13 09:16 AM

Quote:

Quote:

I always wonder what size the 100% field illumination is with scopes like these. If I had to guess, it's pretty small. That's perfectly fine for planetary work, but aren't these mainly visual scopes?



when I changed cameras to one with an APS sized chip, the illumination was poor.




That's kind of what I figured. I think that's one reason Explore Scientific decided to go with the larger CO on their Comet Hunter. The large secondary means the scope is capable of being used as an astrograph. Mine is actually an f/4.8, but you can see that in some loss of contrast visually.

For imaging, the CO contrast loss doesn't matter, and the larger 100% full illumination circle is very useful. Still, it is a big instrument for only being 6" of aperture.

For Mak Newts, rather than make comparisons to SCT's, I think they should be compared to APO refractors because they have more in common in terms of f/ratio and focal lengths. My Comet Hunter has a focal length of 731mm at f/4.8 with 6" of aperture. The ES 127 f/7.5 Triplet APO has a focal length of 952mm at f/7.5. With a 0.8x focal reducer that gets much closer to the Comet Hunter (762mm at f/6).

Also, the comparison in physical size is closer between a large refractor and the MN.

Patrick


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spencerj
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Reged: 11/17/04

Loc: Londonderry, NH
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: jsrj98]
      #5649949 - 01/29/13 10:00 AM

Quote:


From a visual perspective, for me actually looking thru the APO was always a more pleasing experience than with my Mak-Newts. With them I was always fighting cool down issues (and the MN55 had a fan), plus they are bulky and heavy for their aperture. I never owned a Nagler at the same time as my Mak-Newts, but I can't image they would come close to fully illuminating a 22mm Nagler, let alone a 31mm.





This comes up a lot on this forum. Someone has never tried a wide field eyepiece in their Mak Newt (or doesn't even own a Mak Newt), but they are sure the view would be unacceptable. Well . . . I owned a MN66 (smaller secondary than the MN55 or MN65) and I own a 26mm Nagler T5. I have used that eyepiece in that scope several hundred times. While there is a mathematical drop-off in light (that I am sure causes an issue in deep sky imaging) for visual use, the combination works very well.

I loved viewing 2* plus areas of the sky with the 26mm Nagler. The view was flat and sharp to the edge. The illumination drop off does not affect the visual view—certainly not to the extent that some with (or without) experience claim. Outside of an Apo refractor or a Newtonian with a very large secondary mirror, there is always a drop off in illumination at the edge of the field in all telescope designs. The SCT is certainly not immune to this. Until the recent release of the HD SCTs, field curvature as well as edge illumination was an issue in a standard C8. Basically, I could choose to either focus the stars in the middle of the field or the stars at the edge of the field in my C8 with the 26mm Nagler. (Unless I chose something in between where everything was just a little blurry.) So the Mak Newt is held to a higher standard in edge of field illumination because the standard SCT has so much field curvature that illumination drop off is not the biggest issue?

The C8 I had did not have great optics. It was a black tube version from the 90s. My MN66 killed in every way except for light grasp, but the sharper image in the MN66 minimized that advantage the C8 had. The MN66 showed more detail on Mars, Jupiter. Gave cleaner views of double stars. Showed flat, wide-field views that the C8 could never dream of producing. And it cooled down faster. A lot faster. Again, my C8 was not great, but it was not a lemon either. It was somewhere in between and probably well within the bell curve for what was being produced at the time.

Mak Newts are bulky and heavy for their aperture. For me that was the real weakness. As far as cool down goes, that has never been a problem for me either. Certainly not if the comparison is an SCT. The Mak Newt has an oversized tube and light only passes through the tube twice (not 3 times like in a Mak Cass or SCT). Those two features make the Mak Newt superior to those scopes for cool down. Does a standard Newtonian or refractor cool down faster? Sure, but cool down is not a big drawback to the Mak Newt design.


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JohnH
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Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: spencerj]
      #5649981 - 01/29/13 10:18 AM

Between my MN-61 and now the MN-76, I have used both a 26mm Nagler and a 41mm Panoptic. I had not noticed any serious light fall off across the field of view while observing.

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jsrj98
member


Reged: 02/21/08

Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: JohnH]
      #5650013 - 01/29/13 10:38 AM

Quote:

Between my MN-61 and now the MN-76, I have used both a 26mm Nagler and a 41mm Panoptic. I had not noticed any serious light fall off across the field of view while observing.




On my MN55 (which was theoretically optimized for imaging, with a larger secondary and more back focus) the light loss at the outer 1/4 edge of an image taken with a QHY8 CCD camera (slightly larger than a normal DSLR) was more than 50%. I just couldn't get over that, which is why I eventually sold it. At the time I never owned a Nagler, so I could not make a visual comparison.

In theory, the Mak-Newt should experience less cool down issues than an SCT. I've only had my EdgeHD 8 for less than a week, so I guess I'll eventually find out. Having said that I was always disappointed how long it took the views to get really good on my two Mak-Newts.

From a quality perspective (star test), the MN56 and MN55 were always first rate-- and I had the 'papers' from ITE to prove their high Strehl. Of course my new Edge didn't come with any 'proof' of quality (which is why it took me so long to pull the trigger on it), but it's star test is virtually the same on both sides of focus-- which I thought was amazing for a mass produced scope. I'm going to have to dig up my copy of Suiter's book to try to find a fault.


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spencerj
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Reged: 11/17/04

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Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: jsrj98]
      #5650045 - 01/29/13 10:57 AM

What kind of cool down times were you seeing with the Mak Newts? What about the EdgeHD. I used to take mine from inside the house to outside in the winter (40-60*) temp change. It was always fine after an hour or so and ready for high magnification in about 2 hours.

Have you measured the light loss at the edge of the image in the EdgeHD?


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titanio
sage


Reged: 02/15/09

Loc: Alicante, Spain
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: Paul Hyndman]
      #5650083 - 01/29/13 11:21 AM

Quote:

Quote:

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!)




My Mak Newt 8" f 6 has a 17% central obstruction and it weight less than 12 kg.

Toni


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bierbelly
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Reged: 01/23/04

Loc: Sterling, VA
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: titanio]
      #5650242 - 01/29/13 12:46 PM

Quote:

Quote:

Quote:

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!)




My Mak Newt 8" f 6 has a 17% central obstruction and it weight less than 12 kg.

Toni




My 8" f/4 has a 25% CO and weighs about 22lb (10 kg).


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: bierbelly]
      #5650354 - 01/29/13 01:44 PM Attachment (23 downloads)

Quote:

Quote:

Quote:

Quote:

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!)




My Mak Newt 8" f 6 has a 17% central obstruction and it weight less than 12 kg.

Toni




My 8" f/4 has a 25% CO and weighs about 22lb (10 kg).




Just to join the party, here's my MN-66:

Quartz primary, clear polished on the back to speed up cool down, 20% CO, 1/50 RMS , 1/10 wave certified by Intes. Mount by 1st Base Mounts, assembled and finshed by yours truly.

Unlike other MN-66s, it has a fan on the side sticking out like an ugly wart, but which also helps clearing off the boundary layer from the primary. In addition, the mirror is cored to hold it to the cell with a plug/nut.

After I almost broke my neck in the dark trying to use it on the CGE, I put it on a dob mount where it excels in both widefield (2 degrees with a 23mm Nagler clone) and planetary usage (300x on the planets and 500x on the moon). I've used it a lot more since I put it on the dob mount simply because it's always ready to go and cools down in 30min.

Tanveer.


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Paul Hyndman
sage


Reged: 07/13/04

Loc: Connecticut Shoreline USA
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: TG]
      #5650845 - 01/29/13 06:00 PM

Nice set up, Tanveer!

Paul


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titanio
sage


Reged: 02/15/09

Loc: Alicante, Spain
Re: Maksuton-Newtonian vs Schmidt-Cassegrain new [Re: Paul Hyndman]
      #5650920 - 01/29/13 06:40 PM

Hi
My Mn 86 has also quartz optics



Toni


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