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18 inch f4.42 Dob on eq platform w ST120 f/5 finder
12 inch Zhumell Dob
8 inch f/6.9 home made Dob with Seevers optics
William Optics red 10th Anniversary 80mm FD
C8 XLT on Vixen GPDX
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Cernan Space Center astronomer
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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?
150mm MCT f/13, 31% CO
"People say I'm in denial. I disagree."
12" DSH 8" f/4 Vega MakNewt
Quote:Do you own either of those scopes? Not sure what the point of this thread is... No offense intended, just curious.
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%.
"Coffee leads men to trifle away their time, scald their chops, and spend their money, all for a little base, black, thick, nasty, bitter, stinking nauseous puddle water." ~The Women's Petition Against Coffee, 1674If it ain't broke, fix it 'til it is.
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...
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.
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 reflection2. Some oculars may show vignetting3. 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.PeteI can fish out links if its required.
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!
Quote: 10" f/5 that simply was an unimpressive planetary scope.
Skywatcher BD 180mm f/15 Mak Intes M703 180mm f/10 Mak ED102 f/7 refractor Vixen LVW42, 22,13,8,5 and Vixen LV50
Quote:The scopes:10" f/14.6 Mak 23% co10" f/5 newt 26% coOk, 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
Quote: Why would a faster OTA be in the running as a comparable or better planetary instrument?
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.
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.
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.
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.