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azure1961p
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Roland's 10" Mak versus a 10" f/5 reflector
      #5823869 - 04/26/13 09:25 AM

The scopes:

10" f/14.6 Mak 23% co
10" f/5 newt 26% co

Ok, no doubt Roland's Mak is corrected to a higher degree than any 10" f/5, too a paracor would eat up the throughput advantage of the newt s simple design but that still makes it seem like the reflector has a fighting chance to match this $10,000 OTA Mak.

So what's going on here? Is Roland really getting 10" f/5 planetary performance? Or is the ability to perfect a maks optics so much better than a similar parabola that no reflector in that size can realistically hope to compete?

Pete


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dbledsoe
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5823954 - 04/26/13 10:00 AM

Do you own either of those scopes? Not sure what the point of this thread is... No offense intended, just curious.

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Darren Drake
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: dbledsoe]
      #5823991 - 04/26/13 10:16 AM

If you're talking about on axis performance any well made 10 inch f/5 or so newt can absolutely compete with the high end mak as long as the secondary obstruction percentages are similar. Off axis performance would goto the mak but a paracorr would offset that advantage. The light loss from the paracorr is a complete non-factor.

Edited by Darren Drake (04/26/13 10:19 AM)


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Asbytec
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5824027 - 04/26/13 10:31 AM

Quote:


So what's going on here? Is Roland really getting 10" f/5 planetary performance? Or is the ability to perfect a maks optics so much better than a similar parabola that no reflector in that size can realistically hope to compete?

Pete




Pete, I love MCTs and whenever the topic of those nice 10" MCTs pops up, I get excited.

Its really interesting how spherical optics make horrible telescopes, but they can do so much with the caustic focus they can be quite good. Smooth and corrected using additional spherical lens while tossing in that troublesome higher order SA. Still, one this size needs some aspheric term to work as advertised and can be corrected quite well.

Still, a Newt uses a parabolic curve which is ideal for forming a spherical wavefront to some level of precision and cost. It'll deal with less surfaces and employ no lens to absorb light.

Which would work best on planets? I love my MCT on planets so I'd tend to want to vote for the 10" MCT...as dream, refractor-like scope when cooled and collimated. But a good 10" Newt is no slouch.

Does the 10" MCT really have better reflected light and contrast control? At least both should be affected by seeing about the same way.

I dunno, Pete, for one of those comparison threads, you picked a doozie. I'd take the 10" MCT though, if the opportunity arose, primarily because I love the design. They are "pleasing" designs.

Edited by Asbytec (04/27/13 10:10 AM)


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bierbelly
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Asbytec]
      #5824079 - 04/26/13 10:49 AM

IIRC, there's a picture of something through the AP 10" MCT in the current issue of S&T.

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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: dbledsoe]
      #5824108 - 04/26/13 10:58 AM

Quote:

Do you own either of those scopes? Not sure what the point of this thread is... No offense intended, just curious.




I'm not understanding the point of your post to be quite honest. Ownership is not a prerequisite for query. As it is I'm the former owner of a fine 10" f/5 that simply was an unimpressive planetary scope. After several months and not a single wow moment I sold it and was never happier. That said it'd be odd for that beast to be seen as a challenger to a $10000 Mak OTA.

Pete


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Jon Isaacs
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Asbytec]
      #5824110 - 04/26/13 10:58 AM

From memory:

It's probably worth noting that Roland's 10 inch MAK is hand figured by Roland and I believe it is somewhat aspheric. The optics were designed by Valery Deryuzhin of Aries Optical. It also has mirrors made from zero expansion materials and it has cooling ports. I also believe it has a removable baffle for Planetary work that allows for a 22% Central Obstruction.

The thing about the A-P Mak is that it was designed as a system, not just high end, near perfect optics but matched optics in structure optimized... I believe they were $10,000 new, the last one I found that sold was $30,0000 in 2009.

I have to believe that the 10 inch A-P mak is about as close to perfection as any 10 inch scope can be. I think the question would be whether Roland could build an 10 inch F/5 Newtonian that equaled it's performance. He would probably build a Mak-Newt...

One other note: Pete mentions a 10 inch F/5 with a 26% CO. A 10 inch F/5 Planetary Newtonian would have a much smaller CO, a standard configuration with a low profile focuser allows for a 19% CO with a fully illuminated field of view of 19%.

Jon

Edited by Jon Isaacs (04/26/13 11:04 AM)


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Eddgie
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Jon Isaacs]
      #5824227 - 04/26/13 11:51 AM

Yes, I agree that if the CO is kept about the same and the quality (Zambuto, Royce, etc) is about the same, the scopes should perform to about the same level on axis.

The MCT may have better off axis performance, but then again, it is limited to a much narrower true field. If the 10" f/5 scope were limited to the same size true field the coma would not be all that serious an issue.

The AP could give a pinpoint field with a 41mm Panoptic, but the power would be .72 degrees.

If I used a 27mm Panoptic in the 10" reflector, I would limit the field size to .76 degrees (slightly larger than the AP, but because I am not looking as far off of center as I could get with something like a 35mm Pan, the coma would be far less of a factor.

And I could use a Paracorr is I wanted to, and still have a scope that is only 1500mm in focal length vs 3000 for the 10" AP.

There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.

And as to the relevance of the OPS post... Just about anyone that can afford moderately high end 4" APO (Televue or Stellarvue for example) can afford to buy a 10" Go-To Newtonion ($1300) and have the mirror custom refinished (maybe $800 for re-finishing and re-coating)!

For someone wanting a telescope that would go head to head with the AP 10" for less than the price of a little expensive toy telescope, they could have a fantastic planetary scope.

And that includes the tracking mount!!!!!

Yes, I am mocking the refractor community by calling their telescopes little expensive toys.

Don't hate me because physics is beautiful.

Oh, and I think that the reason the AP has aspherized optics is that it is difficult to make a 10" MCT faster than about f/22 that doesn't suffer from some higher order spherical aberration.

The way to manage that is to aspherize one element, most likely the curve of the meniscus on one side. OMG, that has to be hard.

And Mr. Christen even said so as I recall. It seems to me that many years ago he commented that the hand figuring was far more difficult than he would have thought, and did not know if he would ever build another one...

Edited by Eddgie (04/26/13 12:03 PM)


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Paul G
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Jon Isaacs]
      #5824405 - 04/26/13 01:18 PM

Quote:

From memory:

It's probably worth noting that Roland's 10 inch MAK is hand figured by Roland and I believe it is somewhat aspheric. The optics were designed by Valery Deryuzhin of Aries Optical. It also has mirrors made from zero expansion materials and it has cooling ports. I also believe it has a removable baffle for Planetary work that allows for a 22% Central Obstruction.

The thing about the A-P Mak is that it was designed as a system, not just high end, near perfect optics but matched optics in structure optimized... I believe they were $10,000 new, the last one I found that sold was $30,0000 in 2009.

I have to believe that the 10 inch A-P mak is about as close to perfection as any 10 inch scope can be. I think the question would be whether Roland could build an 10 inch F/5 Newtonian that equaled it's performance. He would probably build a Mak-Newt...

One other note: Pete mentions a 10 inch F/5 with a 26% CO. A 10 inch F/5 Planetary Newtonian would have a much smaller CO, a standard configuration with a low profile focuser allows for a 19% CO with a fully illuminated field of view of 19%.

Jon




The AP Mak has a heavily aspherized primary, very smooth, with at minimum 1/10 wave optics (system), zero coma, and is permanently collimated. A long focal length 10" Newt with excellent optics could come close on axis, except for the effects of the spider vanes and any dust on the mirror in the open system on contrast. Excelsior optics used to make a 10" f8 newt for planetary imaging, it produced some superb images. Roland was asked to compare his 10" Mak with Excelsior's 10" f8 newt and he said:

Link


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Paul G
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5824448 - 04/26/13 01:36 PM

Quote:

Oh, and I think that the reason the AP has aspherized optics is that it is difficult to make a 10" MCT faster than about f/22 that doesn't suffer from some higher order spherical aberration.

The way to manage that is to aspherize one element, most likely the curve of the meniscus on one side. OMG, that has to be hard.

And Mr. Christen even said so as I recall. It seems to me that many years ago he commented that the hand figuring was far more difficult than he would have thought, and did not know if he would ever build another one...




It took Roland nearly one year to complete the optics on about two dozen 10" Maks. He said it was a real "hair puller" and that Valery's design was "very elegant but a b***h to make." He has posted that any Maks he makes now will be all spherical and that he will never make such a complex design again.

Initially he was hoping he could import the optics, manufacture the ota, assemble them and have a large aperture lunar/planetary scope that would be easy to make and would satisfy those on his large refractor list. However, once he started it became an exercise in making the most perfect optimized lunar/planetary scope possible, and he did. The coatings alone cost AP nearly $2000 per scope. He even did extra aspherizing of the already heavily aspherized primary to give the scope identical inside and outside star test patterns. Sweet, but the net result was that it was not practical to manufacture long term.

The AP 10" Mak with a MkV binoviewer and ZAO's absolutely screams on the planets. When experienced observers look through it for the first time their unsolicited initial comment is almost always about its superb contrast.


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saemark30
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Paul G]
      #5824701 - 04/26/13 03:37 PM

Looking through a couple of custom 10" F/6 Newtonians with low expansion material, Antares or Prototype secondaries and fans I have seen more detail on Jupiter, Saturn and Mars through that than any MCT or 6" refractor. That is, if the conditions are right.
I have never looked through the AP MCT, but a custom 10" Newtonian only fault is a slight vane effect, otherwise it can be refractor-like in the good sense.


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DJCalma
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: saemark30]
      #5824726 - 04/26/13 03:45 PM

A 2.6" secondary has no business being in a 10" F/5 system. Even if it could be replaced by a 1.83" with full illumination, I'd take the Mak on all days that end in Y.

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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: DJCalma]
      #5824773 - 04/26/13 04:10 PM

Lol, Ed you never disappoint. The physics/beautiful line ought to be your signature.

Pete


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Jon Isaacs]
      #5824804 - 04/26/13 04:29 PM

Quote:

From memory:

It's probably worth noting that Roland's 10 inch MAK is hand figured by Roland and I believe it is somewhat aspheric. The optics were designed by Valery Deryuzhin of Aries Optical. It also has mirrors made from zero expansion materials and it has cooling ports. I also believe it has a removable baffle for Planetary work that allows for a 22% Central Obstruction.

The thing about the A-P Mak is that it was designed as a system, not just high end, near perfect optics but matched optics in structure optimized... I believe they were $10,000 new, the last one I found that sold was $30,0000 in 2009.

I have to believe that the 10 inch A-P mak is about as close to perfection as any 10 inch scope can be. I think the question would be whether Roland could build an 10 inch F/5 Newtonian that equaled it's performance. He would probably build a Mak-Newt...

One other note: Pete mentions a 10 inch F/5 with a 26% CO. A 10 inch F/5 Planetary Newtonian would have a much smaller CO, a standard configuration with a low profile focuser allows for a 19% CO with a fully illuminated field of view of 19%.

Jon




The 2.6" secondary is a Parks spec and Im almost positive the same size I had with my Parks 10" F/5 . There's no way in heaven at least my secondary was anything close to 1.8" in that f/5. It was this FAT thing and if it wasn't 3" it was certainly 2.6". I believe the 2.6" besides the 10" f/5 Parks is also the same size for the Orion XT10. Moreover GSO also goes with a similar sized secondary for its 10" f/5 optical set. We can all shave our secondaries down Jon but the fact is three things begin to rear their head:

1. Collimation becomes more critical in centering the primaries reflection
2. Some oculars may show vignetting
3. The edges of flats are often prone to error if there are errors to be had.

I could arguably make my 8" reflectors secondary the size of my thumbnail but to no gainful benefit.

DJ: its actually good business if you look at the reflectors sold over the last couple decades anyway.
Pete

I can fish out links if its required.

Edited by azure1961p (04/26/13 05:10 PM)


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DJCalma
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5824912 - 04/26/13 05:10 PM

My 10" F/4.5" has a 2.14" secondary and so do several other 10 inchers in my club. One member's scope is a 10" F/7 and has a 1.83".
The only 2.6 incher I've seen is the stock secondary in my lowly Coulter. A newt these days with a 26% obstruction is absurd unless it comes in around F/2.8 or so.


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gnowellsct
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5824915 - 04/26/13 05:11 PM

I think the ten inch Mak went for $10 or $12 k, and on the used market will be bid up to $35 or $40 k. Mainly a prestige item. The question then is what could you do for that kind of money that would out perform it. And there the answer is a 14 or 16 or 18 inch just-about-anything. As with all AP products the ten inch Mak is an ultra precision optical work of art where all elements of design have been thought through. Greg N

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amicus sidera
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5825007 - 04/26/13 06:17 PM

Quote:

Just about anyone that can afford moderately high end 4" APO (Televue or Stellarvue for example) can afford to buy a 10" Go-To Newtonion ($1300) and have the mirror custom refinished (maybe $800 for re-finishing and re-coating)!
For someone wanting a telescope that would go head to head with the AP 10" for less than the price of a little expensive toy telescope, they could have a fantastic planetary scope.

And that includes the tracking mount!!!!!

Yes, I am mocking the refractor community by calling their telescopes little expensive toys.

Don't hate me because physics is beautiful.








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Jon Isaacs
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5825194 - 04/26/13 07:34 PM

Quote:

The 2.6" secondary is a Parks spec and Im almost positive the same size I had with my Parks 10" F/5 . There's no way in heaven at least my secondary was anything close to 1.8" in that f/5. It was this FAT thing and if it wasn't 3" it was certainly 2.6". I believe the 2.6" besides the 10" f/5 Parks is also the same size for the Orion XT10. Moreover GSO also goes with a similar sized secondary for its 10" f/5 optical set. We can all shave our secondaries down Jon but the fact is three things begin to rear their head:

1. Collimation becomes more critical in centering the primaries reflection
2. Some oculars may show vignetting
3. The edges of flats are often prone to error if there are errors to be had.

I could arguably make my 8" reflectors secondary the size of my thumbnail but to no gainful benefit.

DJ: its actually good business if you look at the reflectors sold over the last couple decades anyway.
Pete

I can fish out links if its required.




Pete:

I am not sure what your goal is. If you are trying to compare a Parks 10 inch F/5 Newtonian to Roland Christen's legendary 10 inch Mak, I think everyone agrees that the Parks scope would not be up to the task. It's not an optimized design and many aspects of it are crude, Parks scopes haven't changed much in the past 35 years or so.

This is the question you ask:

"Or is the ability to perfect a maks optics so much better than a similar parabola that no reflector in that size can realistically hope to compete?"

The Parks is not relevant to this question. People do build 10 inch reflectors with small central obstructions by using low profile focusers. They do use mirrors that are tested and figured using interferometers, just as Roland does, they use zero expansion substrates just as Roland does... Consider that Roland removes the baffle to reduce the central obstruction because the light leak is not relevant when viewing the planets...

Jon


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*skyguy*
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Jon Isaacs]
      #5825850 - 04/27/13 08:24 AM

A 10" ... is a 10" ... and always will be a 10". The ultimate end performance is all about design, execution and attention to detail ... and money spent!

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amicus sidera
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: *skyguy*]
      #5825909 - 04/27/13 09:12 AM

Quote:

A 10" ... is a 10" ... and always will be a 10". The ultimate end performance is all about design, execution and attention to detail ... and money spent!




Precisely.

My question is: which 10" f/5 reflector, made with what level of optical quality, versus this vaunted 10" Mak?


Fred (who, after almost fifty years at this, remains unimpressed by "legendary telescopes", having actually had the opportunity to observe through many so designated)


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: amicus sidera]
      #5825963 - 04/27/13 10:02 AM

The PARKS is relative to the example as a model or example of a typical classic 10" f/5 . True, they haven't advanced in 35 years and much to the detriment of their business. At anyrate being that they are so prevalent (reflectors in this size and speed) and that it shared some specs with the Roland -Vallery Mak the comparison seemed worthwhile and revealing of both pluses and minuses in both systems.

You could make the argument that an optimized 10" newt bridges the gap better but that wouldn't be representative of the common reflector in this size most people seem to own.

Pete


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Eddgie
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5825999 - 04/27/13 10:29 AM

Quote:

10" f/5 that simply was an unimpressive planetary scope.




You are comparing a telescope that was crafted over a years time by one of the leading optical fabricators on the planet to a telescope that was most likley not.

The CO you site also understates the real obstruction which is more like 28%. This is because the secondary size alone does not constitute the entire obstruction. A very thin vane spider will ad 2" to the obstruction, and this assumes a very thin. Many time, the spiders are made a bit thicker than the minimum so it is possible that 3% is more realitic, which brings the obstruction to something like 29%.

But it gets worse. Often, the focuser tube will extend very slighty into the light path of a Newtonian when using eyepecies with a field stop located far up in the barrle.

We don't know if this was the case for your particular scope, but I have seen it enough to know that it is not at all uncommon. This may add another couple of percent of obstruction.

But the biggest difference here is optical quality.

The AP is without doubt most liklely to be pushing a strehl of .98%.

I have a serious doubt that the Parks is in this stratified quality level.

And finally this. Planetary Observing rarely presents a "Wow" because seing for most of us is simply not that good.

I spend an hour or two glued to my binovierers to get glimpses of detail on planets. I don't just sit down and see it all. It comes and goes.

Were you patient? Or did you just sit down and expect to see pictures like we seen in the solar system imageing forum?

On my best nights, I don't see Jupiter as well as even so-so images taken with cheap planeatry cameras. One has to remember though that the planeatry camera does what I do, but it does it in five minutes. It watches and takes thousands of images, and the software selects the best images and combines them together.

And that is what I do. I sit and I watch, and I wait. And after several dozen moments of steadiness in the images over an hour or two, I do the same thing. I "Stack" these images in my brain, and I wind up with a mental image that shows much of the detail that the CCD camera captured.

But not all. The eye simply is not a sensitive and lacks the resoltuion of a modern CCD camera.

Summary: Your telescope is more obstructed than you think, and there is a huge probability that the quality is not on par with what we can reliably expect to be one of the finest set of optics ever made.

And my hunch is that you did not exercise the patience necessary to do planetary observing to the level your instrument was capable.


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Eddgie
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5826030 - 04/27/13 10:48 AM Attachment (34 downloads)

I have plotted the two scopes.

The AP was plotted as being perfect optically an that is because we can assume that it is.

The Parks was plotted with a 29% obstruction (to reflect the added diffraction of the spider which I doubt was an optimized thin vane type).

I also plotted the Parks with a single optical defect, which was 1/8th wave of spherical abberation.

Now this represents a mirror of far better than average quality. Most mirrors produced today are not nearly this perfect just on spherical abberation.

Most will have other very small errors like some amount of surface roughness, and usually a very small amount of astigmatism or other on-axis errors.

Usually the only time you get a mirror as good as the one I plotted here is if you pay for a custom mirror.

Anyway, the plot on the right represents the quality of a Newtonian that many of us would be thrilled to have, and my guess is that it represents a level of quality that is above the level that your instrument had.

Notice that at every point on the MTF plot, the AP maintains more of the initial contrast than the Newt.

The CO is the major contributor, but again, I was very kind to the Parks and gave it only a single, minor optical error. The vast marjority of mirrors made today are not this good.

A 10" f/5 reflector could be made to do as well as the AP, but the one you owned could not be expected to come close.


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Eddgie
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5826041 - 04/27/13 10:58 AM

If you are not famaliar with MTF, the solid red line represents the contrast loss of a perfect, unobstructed aperture 10" in size.

The dotted lines represent the additional amount of contrast lost due to optical quality issues or obstruction.

If you worked down from the top of the chart at .4 on the X axis, you would see that even a perfect 10" unobstructed instrument would loose mybe 47% of the contrast at .4 of its maximum linear resolution.

THe AP would loose an additional 7% or so, for a combined contrast loss of about 56%.

The 10" 29% obstructed with 1/8th wave would loose about 62%. This way you can find out how the scopes would transfer contrast on varius sized details, The left side represents large details, and as you work to the right, smaller sized details.

The .4 line represents detials that would be maybe 3 or 4 Airy Disk diametars of the instrument. In a 10" scope this might be detail taht was 2 or 3 arc seconds in size.

Now if you are looking at Jupiter, and it is 35 arc seconds across, this should give you the idea. We would be looking at medium sized pale ovals as an example. These are difficult contrast targets for a smaller apeture, and at 8" or 9" of good apeture, under good seeing, and with patience, will start to show more reqularly.


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5826783 - 04/27/13 05:31 PM

Edd,

I'm at work - I just read through your posts. Can't reply now but I believe the MTF does a fine job of fog lifting here and I appreciate your working through the details in presenting the comparison.

Pete

Edited by azure1961p (04/27/13 05:31 PM)


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5827468 - 04/27/13 11:11 PM

Ok off work ...

I've been observing planets for decades. Even as a kid I was the patient observer. Its my natural thing to lose myself in the observation. Over the course of several months with the 10" f/5 (my prior scope being a C8 and prior to that an old orange C8) I really gave it my all. I was very dissatisfied with the performance - even sending it back to Parks saying that while their accompanied ronchi was ruler straight this was not a performer. I began to see traces if astig at the larger exit pupils of low power but that's a side note that obviously wasn't the issue of PARKS. Anyway, Clements is on the phone with me saying "Jupiter ought to look like gangbusters with this mirror" - they sent it back nothing changed. The night I had a local club menber invite me to come over and let him have a look it was all over. Jupiter was up and he had his 10" f/7 Cave and I realized that was what I wanted. I messed with the collimation doing the high power diffraction pattern centering - he messed with it too. I just had it. I sold the beast and was dead set on a scope from Parralax Instruments. Their brochures aeed to embody my wants here and a check was nearly in the mail till Chris at PARKS said " yes we do custom telescope assemblies". That's all it took. - check was in the mail and the weeks passed. When I finally got it the views were a revelation outdoing any instrument Ive ever owned - certainly the 10" f/5. But it wasn't just planetary Ed...

The Orion Nebula was up I swung it there for a gander and saw clearer than any view before the E-F stars in the trap and in mediocre seeing. Those months I had the ten they didn't budge even once. Jupiter now had these flashes of watermark intensity markings that I never noticed before. It was uncanny. Mind you it wasnt a matter of paying extra attention - these things came to me . I wasn't even thinking of the E-F stars and Jupiter was so good it took getting used to. Saturn later on proved equally stunning and I even went headlong into doubles that spring summer and fall - an interest that was always so-so to me. Clements suggested I try doubles with the scope, I was polite and silently scoffed at it. Bootes was riding that spring and it was a nearly year long obsession. I was seeing these text book star patterns the ten never seemed to manage. Instead he rings tended to blur into the disc - wether it was seeing or extra light in the diffraction rings it was a downer. Other 10" scopes at star parties of the f4.5 variety and such left me equally ho-hum. The one that wasnt was a home made 10" F/7 with a PARKS mirror and dang it what a fabulous Saturn!

The other scopes to sum it up were big bright blah images. That uncanny tickle of gossamer details that flutter with the seeing just kind of simplified into something that didn't move me. Eh.

Sometimes I regret having let the 10" go - I lost angular res and some deepsky ability. I wonder what I might have or could have done to make it work but Im happy enough with the carefree, coma free easy collimating f/9 and I leave it there.

Maybe the next time Im at a star party and there's another fast ten Ill give a look see . The images in the f/9 though again were a revelation. If it'd been even a little ho hum Id ve sold it - as it is this was no. 4 in a succession of buying, trying and selling. This one for me was the winner.

Pete

Ps: I've read through all the technicals on MTF. I'm going to rereading it all tomorrow morning when Im fresh. Again thanks.

Edited by azure1961p (04/27/13 11:24 PM)


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5827501 - 04/27/13 11:27 PM

Edd,

How ARE you saving those aberrator mtf images - I can't manage this but Id like to be able to save them for comparisons I do.

Thanks.


Pete


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Eddgie
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5827567 - 04/28/13 12:34 AM

I have to do a FN/Print Screen, then past them into individual MS Paint images, then copy the MTF from one, then past it into the other, then crop the two MTFs.

Aberrator does not allow you to generate more than one MTF at a time.

I did not realize that you had tow different 10" scopes.

My guess was that the f/7 one was more optimized than the f/5 one, but if an f/5 scope were built with a 20% secondary and the optics were of superb quality, then it should do as well as the MCT.

But this would be a custom scope, and the off axis illumination would not be great. But still, you would likely have the same true field capability of the f/14.4 AP, with a bit of coma of course. At the center of the field, the performance should be similar.


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5827846 - 04/28/13 07:52 AM

Thanks Edd,

What's a fn/print screen?

I didn't have two ten inch scopes - one was a friends from a local club I spent the evening with another was at a starparty . Sorry for the confusion on description.
Pete

Edited by azure1961p (04/28/13 07:54 AM)


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iluxo
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: amicus sidera]
      #5827875 - 04/28/13 08:27 AM

You're all missing something - you need eyepieces to see anything. It isn't just about CO and MTF.

On the planets I'd much rather use an f/15 Mak with a 10mm eyepiece than struggle with an f/5 Newtonian with any 3.5mm eyepiece you can name (to achieve roughly the same magnification).

Barlows/Powermates etc don't help either.

Edited by iluxo (04/28/13 08:29 AM)


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JJK
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5827906 - 04/28/13 08:56 AM

Quote:

The scopes:

10" f/14.6 Mak 23% co
10" f/5 newt 26% co

Ok, no doubt Roland's Mak is corrected to a higher degree than any 10" f/5, too a paracor would eat up the throughput advantage of the newt s simple design but that still makes it seem like the reflector has a fighting chance to match this $10,000 OTA Mak.

So what's going on here? Is Roland really getting 10" f/5 planetary performance? Or is the ability to perfect a maks optics so much better than a similar parabola that no reflector in that size can realistically hope to compete?

Pete




Why would a faster OTA be in the running as a comparable or better planetary instrument?

I have the AP 10" Mak-Cass and a good number of other fine scopes (AP apos, Zeiss APQs, Tak Mewlon 300CR), and have looked through a lot of other's telescopes. Roland's Mak-Cass provides about as close to refractor performance as I've seen. In addition to delivering highly detailed views of the planets (Jupiter & Saturn), it performs well on Lunar features, globular clusters and other DSOs. Thus far, it has given me the best view of M42 (with a Leitz 30 mm 88* AFOV EP). It easily shows the central star of M57, because it can tolerate ridiculously high magnification.

I may be selling a scope or two soon to purchase an FLI CCD camera. My AP Mak-Cass will never leave.


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Eddgie
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5828013 - 04/28/13 10:15 AM

Function Key, Print Screen Key on your keyboard.

This will make an image of your desktop in your computer clipboard.

Now, when you want to edit it, just open Microsoft Paint and do a "Paste." The image of your desktop will show up in Paint.

I did two different Aberrator images into two different Paint Windows, then cut and pasted the MTF from one to the other, then cropped everything else out.

It is only a little tedious, but I do it so that it is easy to make a side by side comparison for interested people that are interested.

Of course I realize that most people are not at all interested, but as you can see, MTF offers a very visual way of comparing how two different instruments might perform.


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Eddgie
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5828020 - 04/28/13 10:21 AM

The speed of an optical system does not really have much bearing on its ability to perform well on planets.

And the reality is that it has to be in the running because not everyone can afford a $10,000 telescope.

And when you could put together a telescope offereing similar performacne with a tracking mount for less than $3000, most people would say that this would indeed be a valid challanger.

The only issue with building an f/5 planetary scope is that the small obstruction required would make it unusable for wider field viewing, but then again, a 10" f/14.4 MCT does not really offer much in the way of wide field viewing either.

Still, if you used a very low profile focuser on the Newtonian, you could potentially have a wider true field than the f/14.4 MCT.

So, similar planetary performance and a wider field of view for maybe 25% of the price.

Sure, one is an AP and one is an Orion Dob with custom mirrors, but if the goal is to see an equal amount of detail on planets, then you can get there with an optimized 10" f/5.


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Jon Isaacs
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5828134 - 04/28/13 11:24 AM

Quote:


Why would a faster OTA be in the running as a comparable or better planetary instrument?




A point I think is worth making: The primary mirror of the Mak is in the F/3 realm. Compound scopes are very fast spherical mirrors combined with corrective optics and a magnifying secondary mirror to achieve that slow focal ratio. While the optics may be spherical they are not in the scope in question and one can fabricate a somewhat slower parabola with equal precision.

Jon


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: iluxo]
      #5828136 - 04/28/13 11:25 AM

Quote:

You're all missing something - you need eyepieces to see anything. It isn't just about CO and MTF.

On the planets I'd much rather use an f/15 Mak with a 10mm eyepiece than struggle with an f/5 Newtonian with any 3.5mm eyepiece you can name (to achieve roughly the same magnification).

Barlows/Powermates etc don't help either.




No they dont. Barlows are cosmetic attachments to make low power oculars feel mighty.

P.


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5828140 - 04/28/13 11:29 AM

Quote:

Function Key, Print Screen Key on your keyboard.

This will make an image of your desktop in your computer clipboard.

Now, when you want to edit it, just open Microsoft Paint and do a "Paste." The image of your desktop will show up in Paint.

I did two different Aberrator images into two different Paint Windows, then cut and pasted the MTF from one to the other, then cropped everything else out.

It is only a little tedious, but I do it so that it is easy to make a side by side comparison for interested people that are interested.

Of course I realize that most people are not at all interested, but as you can see, MTF offers a very visual way of comparing how two different instruments might perform.




Im thinking of an overlay here in photoshop where both are visible as one image. I could color shift one to separate it from the other .
Just a thought.

Pete


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Eddgie
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5828694 - 04/28/13 04:30 PM

Well, that would indeed be better. I don't have photoshop, so my tool was Paint.

When you have had a chance to do one, would you show me what it looks like


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Jon Isaacs
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5828942 - 04/28/13 07:19 PM

Quote:

Quote:

You're all missing something - you need eyepieces to see anything. It isn't just about CO and MTF.

On the planets I'd much rather use an f/15 Mak with a 10mm eyepiece than struggle with an f/5 Newtonian with any 3.5mm eyepiece you can name (to achieve roughly the same magnification).

Barlows/Powermates etc don't help either.




No they dont. Barlows are cosmetic attachments to make low power oculars feel mighty.

P.




As someone who actually uses F/5 Newtonians for Planetary viewing, Barlows can be an effective tool. It's probably easier to fabricate a high quality Barlow than a high quality 5x magnifying mirror...

Jon


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JJK
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5829008 - 04/28/13 08:03 PM

Quote:

The speed of an optical system does not really have much bearing on its ability to perform well on planets.

And the reality is that it has to be in the running because not everyone can afford a $10,000 telescope.

And when you could put together a telescope offereing similar performacne with a tracking mount for less than $3000, most people would say that this would indeed be a valid challanger.

The only issue with building an f/5 planetary scope is that the small obstruction required would make it unusable for wider field viewing, but then again, a 10" f/14.4 MCT does not really offer much in the way of wide field viewing either.

Still, if you used a very low profile focuser on the Newtonian, you could potentially have a wider true field than the f/14.4 MCT.

So, similar planetary performance and a wider field of view for maybe 25% of the price.

Sure, one is an AP and one is an Orion Dob with custom mirrors, but if the goal is to see an equal amount of detail on planets, then you can get there with an optimized 10" f/5.




I would expect with faster optics, more care needs to be applied with figuring them.

Also, I doubt that an Orion Newtonian can perform as well as the AP Mak-Cass.


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R L Harris
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5829127 - 04/28/13 09:14 PM

I have seen some fantastic views in newtonians in my life time!
I started out in astronomy when I was 14 years old 1972!
ground my first telescope lense when I was 16-1974!
Worked for Celestron !978-1980 as optical Assembler Mainly
worked on C-14!
And have used and built many scopes in my life time!


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JJK
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: R L Harris]
      #5829215 - 04/28/13 09:59 PM

Quote:

I have seen some fantastic views in newtonians in my life time!
I started out in astronomy when I was 14 years old 1972!
ground my first telescope lense when I was 16-1974!
Worked for Celestron !978-1980 as optical Assembler Mainly
worked on C-14!
And have used and built many scopes in my life time!




I'm not knocking the virtues of Newtonians with well-figured mirrors. I'm simply suggesting that an AP 10" f/14.6 Mak-Cass will outperform a more conventional 10" f/5 Newt on lunar and planetary views for several reasons.


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R L Harris
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5829262 - 04/28/13 10:28 PM

I agree with that even SC would work a little better on
Planetary but mak are awesome scopes for it -
but expensive lol!


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iluxo
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: R L Harris]
      #5829547 - 04/29/13 04:46 AM

I'm not disputing the possible qualities of a 10" f/5 primary mirror.

What does concern me - after 40 years experience - is the performance of eyepieces, especially short ones. If you regularly observe at x1 or more per mm of aperture a long focal ratio scope coupled with a quite modest medium f.l. eyepiece is a far more appropriate solution than any f/5 scope no matter how perfect the primary, and any eyepiece combination your can come up with.

One of the major drawbacks at the eyepiece end - especially with very short f.l. eyepieces - is the scattering, losses and general image degradation arising from the number of air-glass surfaces and the scattering within the eyepiece. Adding a Barlow or PowerCorr only makes it worse.


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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: iluxo]
      #5829613 - 04/29/13 07:13 AM

Quote:


What does concern me - after 40 years experience - is the performance of eyepieces, especially short ones. If you regularly observe at x1 or more per mm of aperture a long focal ratio scope coupled with a quite modest medium f.l. eyepiece is a far more appropriate solution than any f/5 scope no matter how perfect the primary, and any eyepiece combination your can come up with.




I think Texereau said it best:

"It is not usually made clear, that these elements, objective and eyepiece, are by no means comparable in importance. The astronomer's hopes are almost wholly tied to the size and quality of the objectve. The objective of even the smallest telescope, because of its larger dimensions, the severe optical requirements it must meet, and the difficulty of its construction, completely overshadows the eyepiece."

- "How to Make a Telescope," by Jean Texereau, Page 1, Paragraph 2.

When it comes to planetary viewing, the most important factor is the seeing, then comes the scope, the size, the quality and thermal state.

Jon


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Jon Isaacs]
      #5830931 - 04/29/13 07:09 PM

Quote:

Quote:

Quote:

You're all missing something - you need eyepieces to see anything. It isn't just about CO and MTF.

On the planets I'd much rather use an f/15 Mak with a 10mm eyepiece than struggle with an f/5 Newtonian with any 3.5mm eyepiece you can name (to achieve roughly the same magnification).

Barlows/Powermates etc don't help either.




No they dont. Barlows are cosmetic attachments to make low power oculars feel mighty.

P.




As someone who actually uses F/5 Newtonians for Planetary viewing, Barlows can be an effective tool. It's probably easier to fabricate a high quality Barlow than a high quality 5x magnifying mirror...

Jon




I was jesting. I love barlows.

Pete


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iluxo
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5831472 - 04/30/13 01:33 AM

Well ... I know many will still shake their heads in disbelief but all I can say is go try it, as I did 2 nights ago.

... a direct practical test on Saturn which at the moment is near the zenith here - my 7" f/15 Mak vs a very good 10" f/5 dob 2 nights ago.

The 10" dob gave a brighter image, no question, but the 7" Mak showed more details on Saturn.

The eyepieces used in both scopes were my set of Vixen LVW's; 13mm in the 7" Mak gave almost identical magnification as 5mm in the 10" dob. The owner of the dob was quite interested in the side-by-side comparison.

A good 10" f/15 Mak will easily SLAY a 10" f/5 newtonian on the planets, for resolution of fine detail.



Edited by iluxo (04/30/13 01:35 AM)


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: iluxo]
      #5831661 - 04/30/13 07:13 AM

See that's my finds with my 8" versus the 10" reflector - its big and bright but not as detailed. As I've mentioned (ad naus.) an f/7 is a different kind of 10" though.

Pete


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GeneT
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5833181 - 04/30/13 08:42 PM

Quote:

10" f/14.6 Mak 23% co
10" f/5 newt 26% co




For a 10 inch F5 Newt, 26 percent CO seems a little high. There are models that are in the 20-22 percent range. However, I don't think a few percent extra CO will be all that noticeable if the optics are of high quality.


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azure1961p
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: GeneT]
      #5833272 - 04/30/13 09:42 PM

Thanks Gene. Others have mentioned that too . I can attest my 10" f/5 was that.

Pete


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issdaol
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: Eddgie]
      #5870135 - 05/18/13 08:30 PM

Quote:


There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.






Would appreciate if you can point us to these bench tests??

There are quite a few interested people including me that would find this helpful as comparison for future purchases.


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JJK
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: issdaol]
      #5870837 - 05/19/13 07:49 AM

Quote:

Quote:


There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.






Would appreciate if you can point us to these bench tests??

There are quite a few interested people including me that would find this helpful as comparison for future purchases.




Even a bit more off-topic, I have both a AP 10" f/14.6 Mak-Cass and a Tak Mewlon 300CR. If I couldn't get the former, I'd be quite pleased with the latter. They're both wonderful visual instruments for lunar, planetary, globular, and relatively bright DSOs (my 25" Newt is obviously better for viewing the fainter fuzzies).


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charles genovese
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5871317 - 05/19/13 12:49 PM

U guys r silly. A newt can equal any other design. I have esentilly perfect optics in both of my 10" newts -f/4.5 and f/6- and il put both up against th mak. They hav all th tricks and essentially perfect optics. There is no single secondary size for a newt. It depends on th field illumination u want and the distance prime focus is out. Both can have th mirror slide back or foreward 3" to give 1/2 " back focus for visual or planetary imaging and 3-4" out for deepsky imaging. The secondary is easily interchangable (same for my 16"f/4.5) and i have 1.8, 2.1, 2.6,3.1, 3.5, and 4" ers. For the 10"f/6 1/2 " back focus 1.8 " secondary gives 1/2 " of 100% illumination- usual setup. If i wanted to image deep sky i would move th primary foreward 3" and change to a 2.6 " secondary giving about 35mm of 100% illumination- gives roo
For a coma corrector and off axis guider. For the 10" f/4.5 the typical setup is 3" backfocus and a 2.6" secondary and it has about -5 mm of 100% illumination. For serious widefield imaging i would move th primary foreward another 1/2 inch and increase the secondary to 3.1.
Also whoever said something about th spider was wrong. The effect is insignificant. Btw a curved spider eliminates difraction spikes if it bothers u.
A subaperature corrector (coma corrector) is a lot easier to make than a full aperature mak corrector! And barlows are an integral part of all widefield short focal length eyepieces.
Sorry if aNy typos- out on my boat fishing lol


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charles genovese
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5871331 - 05/19/13 12:57 PM

Also - perfect optics for a newt is a LOT cheaper than a mak!
I also have fans , vent holes , flock , (btw baffles are unnecessary with modern flock).
There are a few other considerations- newts r more sensative to ground radiation- grass is best but if u cool cement slabs with water before observing its bettr.


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issdaol
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5872188 - 05/19/13 06:40 PM

Quote:

Quote:

Quote:


There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.






Would appreciate if you can point us to these bench tests??

There are quite a few interested people including me that would find this helpful as comparison for future purchases.




Even a bit more off-topic, I have both a AP 10" f/14.6 Mak-Cass and a Tak Mewlon 300CR. If I couldn't get the former, I'd be quite pleased with the latter. They're both wonderful visual instruments for lunar, planetary, globular, and relatively bright DSOs (my 25" Newt is obviously better for viewing the fainter fuzzies).




Sounds like a big investment there :-) How would you compare the views, build and optical quality of the Tak 300 against the AP and other top end scopes??


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JJK
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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: issdaol]
      #5872739 - 05/19/13 10:46 PM

Quote:

Quote:

Quote:

Quote:


There was a thread a while back that pitted a 250 Mewlon against the 10" AP and I picked the 10" AP on that one.

For that one, the Mewlon had a meaningfully bigger CO, but more importantly, the bench tests I have seen on Mewlons have led me to believe that they are not made to the same high level of perfection that you would get from either the AP or a custom mirror Dob.






Would appreciate if you can point us to these bench tests??

There are quite a few interested people including me that would find this helpful as comparison for future purchases.




Even a bit more off-topic, I have both a AP 10" f/14.6 Mak-Cass and a Tak Mewlon 300CR. If I couldn't get the former, I'd be quite pleased with the latter. They're both wonderful visual instruments for lunar, planetary, globular, and relatively bright DSOs (my 25" Newt is obviously better for viewing the fainter fuzzies).




Sounds like a big investment there :-) How would you compare the views, build and optical quality of the Tak 300 against the AP and other top end scopes??




It's hard to say. I don't often have them out together, but they're both excellent instruments. The AP Mak-Cass is lighter, looks sleeker, and has excellent thermal design. The Mewlon 300CR should have more reach, but I haven't critically tested them to see which one performs better visually with faint fuzzies. IMO, previously owned Mewlon 300 OTAs are bargains.

I also have an AP 175 f/8 apo (used to have an AP 180 f/9 EDT, but regrettably had to sell it, per the current CFO's orders). I'll be comparing the 175 and the AP Mak-Cass this Summer.


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5872748 - 05/19/13 10:49 PM

Quote:

U guys r silly. A newt can equal any other design. I have esentilly perfect optics in both of my 10" newts -f/4.5 and f/6- and il put both up against th mak. They hav all th tricks and essentially perfect optics. There is no single secondary size for a newt. It depends on th field illumination u want and the distance prime focus is out. Both can have th mirror slide back or foreward 3" to give 1/2 " back focus for visual or planetary imaging and 3-4" out for deepsky imaging. The secondary is easily interchangable (same for my 16"f/4.5) and i have 1.8, 2.1, 2.6,3.1, 3.5, and 4" ers. For the 10"f/6 1/2 " back focus 1.8 " secondary gives 1/2 " of 100% illumination- usual setup. If i wanted to image deep sky i would move th primary foreward 3" and change to a 2.6 " secondary giving about 35mm of 100% illumination- gives roo
For a coma corrector and off axis guider. For the 10" f/4.5 the typical setup is 3" backfocus and a 2.6" secondary and it has about -5 mm of 100% illumination. For serious widefield imaging i would move th primary foreward another 1/2 inch and increase the secondary to 3.1.
Also whoever said something about th spider was wrong. The effect is insignificant. Btw a curved spider eliminates difraction spikes if it bothers u.
A subaperature corrector (coma corrector) is a lot easier to make than a full aperature mak corrector! And barlows are an integral part of all widefield short focal length eyepieces.
Sorry if aNy typos- out on my boat fishing lol




I don't know why you replied to my post. I didn't knock Newtonians.


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azure1961p
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Reged: 01/17/09

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Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5872777 - 05/19/13 11:02 PM

Nice post and points Charles.

Pete


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issdaol
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Reged: 01/01/10

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: azure1961p]
      #5872997 - 05/20/13 02:02 AM

Hi JJK,

Good to hear favorable comparisons from someone that actually owns and uses both AP and Tak scopes.

It seems like a lot of people put one or the other down without ever having owned both referring to vague tests and statements that are never validated or produced.

So based on the OP topic the Mewlon would stand up well against the AP Mak even though it is not f5??


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charles genovese
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Reged: 02/04/06

Loc: Madisonville Louisiana
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: issdaol]
      #5873361 - 05/20/13 09:59 AM

Hi JJK- wasn't knocking you- just responded based on some things that were said. Rollands Mak is a spectacular instrument I'm sure, but for 1/10 (or less) one could have a comperable Newt. BTW, my most used scope is a C8 with excellent optics (that has vent holes-note the large amount of ventillation on the AP Mak!)

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azure1961p
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Loc: USA
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5874460 - 05/20/13 07:06 PM

You know Charles its interesting that you have several secondary sizes and it would seem like the way it ought to be for everyone with fast newts. Like I said in the previous post you've made a lot of good points. Its easy enough just to switch it out based on the call of the evening. Had an f/5 been my instrument and long focus didn't exist Id have a number of secondaries.

And they are so relatively cheap!

Pete


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: charles genovese]
      #5874579 - 05/20/13 08:21 PM

Quote:

Hi JJK- wasn't knocking you- just responded based on some things that were said. Rollands Mak is a spectacular instrument I'm sure, but for 1/10 (or less) one could have a comperable Newt. BTW, my most used scope is a C8 with excellent optics (that has vent holes-note the large amount of ventillation on the AP Mak!)




Ok, thanks. I don't mind criticism, as long as it's accurate and constructive.

Roland's 10" Mak-Cass was "only" $10K new (I shudder at what it might fetch now). Are top-notch 10" f/5 Newtonians selling for less than $1K new? That'd be a lot of bang for the buck.

I've used C8s, C9.25s, and C11s. IMO, they're incredible bargains (and some day, I'd love to get a cherry-picked C14). However, none of them were as well made (optically & mechanically) as the AP, they didn't perform as well on lunar/planetary views, and are not as versatile (the AP can be used visually at much higher magnification).

With the AP Mak-Cass, I've seen extremely fine lunar features (e.g., the entire length of Rima Marius, not just the part drawn in Rukl's atlas). There's no way any SCT I've ever used could have performed that well (FWIW, an AP155 f/7 EDF failed to show the finest part of the Rima that night). I wish I had the Tak Mewlon 300CR back them. It would have been a very interesting and critical comparison.


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JJK
Carpal Tunnel


Reged: 04/28/08

Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: issdaol]
      #5874587 - 05/20/13 08:25 PM

Quote:

Hi JJK,

Good to hear favorable comparisons from someone that actually owns and uses both AP and Tak scopes.

It seems like a lot of people put one or the other down without ever having owned both referring to vague tests and statements that are never validated or produced.

So based on the OP topic the Mewlon would stand up well against the AP Mak even though it is not f5??




I think the Tak Mewlon 300CR performs extremely well. I'd recommend one to anyone whose seeing can support it, even if only occasionally.


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charles genovese
professor emeritus
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Reged: 02/04/06

Loc: Madisonville Louisiana
Re: Roland's 10" Mak versus a 10" f/5 reflector new [Re: JJK]
      #5876886 - 05/21/13 08:35 PM

Minor correction- I pulled out the calculations and the field of 100% illumination for the 10" f/4.5 with th 2.6" diagonal and the focal plane 12" from the optical axis (6" from the tube or 4" of back focus from the focuser) is about .6" or 15mm, (not 5 as I wrote).

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