BillP
Postmaster
Reged: 11/26/06
Posts: 9093
Loc: Vienna, VA
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I'm considering adding a 5" scope to the stall...either the Celestron 5SE or one of the Orion 127mm Maks.
Would there be any advantage to one design vs the other (in terms of optical performance only such as planetary performance, sharpness, widest TFOV possible, highest useful power, visual contrast, etc.
Not getting it for any special observing task other than as a compact general purpose, compact, 5" viewing platform.
Also, if anyone has experience with either or both of these, would appreciate your impressions and comparisons.
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Bill
The KING: Any Eyepiece in the Focuser
The SUBJECTS: XT10i Dob---Meade 2080 SCT---TSA-102 S APO---Onyx 80EDF APO---SkyLight 60mm F15m---P.S.T.
If you want to make an apple pie from scratch, you must first create the universe. - Carl Sagan
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Larry F
Carpal Tunnel
Reged: 05/24/04
Posts: 2096
Loc: Westchester, NY
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FOV: SCT wins. (f/10 vs. f/13).
Cool-down: SCT wins (thinner corrector plate) by about 30-40% shorter.
Planetary sharpness/contrast: Mak wins by a bit.
Ease of collimation: SCT wins (but Mak seems less likely to go out of collimation).
Weight: SCT wins by a little.
I have both, but the C5 is on a fork mount and is more complicated to set up than the Mak, which I use on the Giro/Tech2000 alt-az tracking set-up mostly for planetary observing. Sets up fast and tracks quickly with no polar-alignment required, so its more functional for me.
You'll enjoy either one.
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More stuff than I need
Not as much as I want
(Main scope: CPC800/Mallincam Color Hyper Plus)
Mason & Hamlin BB 2140 mm (grand piano)
Westchester Amateur Astronomers
My Gallery
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Tuugii
professor emeritus
Reged: 03/22/07
Posts: 533
Loc: Ulaanbaatar, Mongolia
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FOV: Mak wins. Planetary views will be far better than C5.For DSO, C5 is better because it accepts 2" accessories so you can put a focal reducer.
Cool Down: if you can put a simple ventilator then Mak wins.
Ease of collimation: no doubt Mak wins. They're built like tanks.
Portability: Mak wins.
Think about Intes M500, which is a better rig than both of them. 
Tuugii
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telescope=time machine...
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blackhaz
Carpal Tunnel
Reged: 05/20/06
Posts: 1825
Loc: Prague, Czech Republic
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Basing on my own experience owning C11 SCT and Synta MAK127 MCT that is the same MCT as Orion 127mm.
FOV: SCT wins. Orion is f/12 while Nexstar 5SE is f/10.
Cooldown: Haven't compared both models but I would anticipate SCT to quick cooler as it's corrector plate is thinner than meniscus. The Mak would require a cooler to cooldown, as Tuugii mentioned.
Planetary performance: I would expect Mak to deliver better planetary views because: 1) it's meniscus doesn't have the SCT corrector plate rougness, 2) it has a slower optics that is easier to make good.
Collimation Mak wins, guys, because it's a slower system.
It takes more movement to move the mirror in Mak. With SCT, you breathe on the screw and your secondary is already went to Hawaii. Nothing wrong with it, just needs a ninja hand.
If I'm to choose a general all-around scope my bet would be on an SCT.
Weight: I would anticipate SCT to be lighter and the weight more biased towards it's back (with MCT is somewhere in the middle as meniscus compensates the main mirror weight) because of it's light corrector.
Hope this helps.
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Maxim Usatov,
Aries 10" f/15 MCT AP 900GTO QSI 532wsg - Celestron C11-SGT (XLT) http://www.bcsatellite.net/bao/
Well, it's a slap in the face or a kick in the butt, you know? (C) Sig Hansen
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BillP
Postmaster
Reged: 11/26/06
Posts: 9093
Loc: Vienna, VA
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Tuugii - didn't realize there are no .63x reducers for the Orion/Synta Mak!! So I gess the rear cell threads are different size than what's on the Celestron? Are there reducers that will fit the Intes you mentioned?
Max - can you elaborate on the roughness of the meniscus you mentioned. I have not heard before that the SCTs are considered less well polished than what's on a Mak.
Does anyone feel the small difference in the CO size between the two 31% Mak vs 35% SCT would make any visual difference for planetary? While some suggest the Mak will be better planetary and have state FL as a reason and meniscus polish, regardless of FL difference between the two, if magnifications used are the same what in your opinion would be the biggest drivers of the better planetary performance between the two?
Thanks!
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Bill
The KING: Any Eyepiece in the Focuser
The SUBJECTS: XT10i Dob---Meade 2080 SCT---TSA-102 S APO---Onyx 80EDF APO---SkyLight 60mm F15m---P.S.T.
If you want to make an apple pie from scratch, you must first create the universe. - Carl Sagan
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blackhaz
Carpal Tunnel
Reged: 05/20/06
Posts: 1825
Loc: Prague, Czech Republic
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Bill, this question is being frequently raised. The last thread (that is a really good one) is here: Shorter link
You may want to search the forum on "roughness" to see if it provides you with more related results.
In two words - corrector of an SCT (it's not a meniscus lens) needs a specific figuring job that is done by automated machines in cases with mass production SCTs like you mention. That keeps their price low. Those machines leave a rough optical surface on the corrector that diverges rays coming into your telescope: points are getting scattered to spots or that robs contrast from non-point sources like planets, the Moon, etc. There's nothing you can do about it really. While I'm still learning on the amount of contrast loss such a rough surface will produce, I can't provide any numeric proof. At the same time I was enjoying views in my C11 (SCT) a lot, both planetary and DSO, but ended up buying an MCT specifically for the planets.
The CO size difference, I guess, won't be dramatic, but Mak should deliver more contrast. If your goal is a planetary instrument then I would vote for Mak. If you need a swiss-knife scope, then it would be SCT, however I'd suggest finding a model that accepts 2" eyepieces so you could get a much wider field out of it. The Nexstar 5SE, AFAIK, accepts 1.25" eyepieces only and it's FOV won't be much wider than the Mak.
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Maxim Usatov,
Aries 10" f/15 MCT AP 900GTO QSI 532wsg - Celestron C11-SGT (XLT) http://www.bcsatellite.net/bao/
Well, it's a slap in the face or a kick in the butt, you know? (C) Sig Hansen
Edited by ~Steph~ (12/12/07 05:54 PM)
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firestar
Born to be Mild
Reged: 10/18/06
Posts: 3942
Loc: Cleveland Ohio USA
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I would have to chose the faster SCT.
I know everyone tells me the speed of the scope only matters for astrophotography,but faster scopes seem to give me brighter views in the eyepiece for visual use.
Am I nuts ?
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Eastlake Ohio
Lots of cheap Asian glass  
Antares 12" Dob,Antares 8" Dob
Meade 8" SCT, Celestron C8 SCT
Zhumell 152 mm F8,Antares 127 mm f9.4
Orion short tube 90 F5.6,Celestron 80 ED F7.5
Imaging Source DMK 21AU04 ccd camera
Stellarvue bv3's with 32,26,23,21,9 mm pairs
Olivon 42,35,28mm,siebert 21,12.5,7mm,GSO superview 20mm,Meade swa 13.8mm,Hyperion 13mm
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blackhaz
Carpal Tunnel
Reged: 05/20/06
Posts: 1825
Loc: Prague, Czech Republic
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It won't give you brighter views and no, you're not nuts to choose an SCT. The f/ratio plays role with photography only. The major visual thing that you may get with a faster scope like SCT is wider field of view. You can calculate the field difference and determine what's the benefit.
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Maxim Usatov,
Aries 10" f/15 MCT AP 900GTO QSI 532wsg - Celestron C11-SGT (XLT) http://www.bcsatellite.net/bao/
Well, it's a slap in the face or a kick in the butt, you know? (C) Sig Hansen
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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I use the F6.3 Celestron FR with my 5" Mak and 2" diagonals using a SCT adapter . I use up to a 2" 26mm SWA 70° with the F6.3 FR with no vignetting and a 40mm Pentax XW 70° eyepiece without the FR.
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Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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Glassthrower
Vendor - Galactic Stone & Ironworks
Reged: 04/07/05
Posts: 17931
Loc: Oort Cloud 9
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I briefly owned an Orion 127mm Starmax. I bought it for my stepson who is living in Japan. I received it, inspected it and gave it a test drive before I shipped it off to him - where he now has it and is happy with it.
I got to use it over a period of about a week. I only had one good clear night out of the week. Most of the observations were through fleeting sucker holes or poor transparency. So I did not get to give it a full "run around the block", but I did get a good feel for the optics and mechanics of the scope.
The optics are very sharp. Also, the brightness and contrast of the image was at least equal to my 4" Orion refractor. This surprised me because of the central obstruction on the Mak, but it seemed to have about the same "penetration" as a 4" unobstructed refractor. But, it also had a lot more image brightness - you could run the magnification up much further with the Mak than you could the 4" achro. At about 200x the 4" achro starts to fall apart - depending on target and conditions. The 5" Mak easily holds up to 250x and can be pushed to 300x before things start to get weak, assuming good seeing.
After being weaned on achromats, I was pleased with the total lack of false color on planets. I did not notice any yellow bias to the view, which some observers report (due to the glass used). I did detect a very subtle shift towards warm compared to a good achromat or apochromat, but it could have been my eyes or my imagination.
In the sample I owned (I was the 2nd owner), there was some mirror shift. Not a deal breaker, and I'm not experienced with CAT's so I don't have a good feel for what is acceptable. But I didn't care for it. I like a good solid image without wobbles or shakes - for focusing and slewing around. If my 150 (which I just bought and is on the way) exhibits the same degree of mirror shift, then I am going to bypass it with a helical focuser.
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Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.
☄ ⒼⒶⓁⒶⒸⓉⒾⒸ ⓈⓉⓄⓃⒺ ☞ www.galactic-stone.com
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BillP
Postmaster
Reged: 11/26/06
Posts: 9093
Loc: Vienna, VA
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Quote:
It won't give you brighter views ... The f/ratio plays role with photography only. ...
I'd say this is a "conditional" issue as to whether the 5SE will be visually brighter than the Starmax 127. "If" you are limiting yourself to 1.25" EPs, no focal reducer, and wide field EPs...then something akin to a 24 Pan or Hyperion are your longest FL EP with a wider than Plossl afov. And these of course max out the TFOV for a 1.25". That being the case, the magnification will be higher in the Starmax vs the SE and since aperture the same, image will be dimmer.
...and actually, even if you go to a 40mm 1.25" Plossl, which is about as low as you can go in 1.25" format, since the EP's FL is the same the image will still be slightly dimmer in the Mak due to the longer FL and same aperture.
So for these particular 2 instruments, with no reducers or 2" EPs in the chain, the SCT will be a tad brighter....all other things being equal (mirror reflectivity, front lens coatings, etc.).
On another note....
I was counting on using a reducer from time to time no matter which I chose. Unfortunate to hear the Starmax will not accept a reducer. I do have a 1.25" .63x reducer though...it works quite well on shorter FL EPs (threads to the filter threads on EPs) in fast scopes...have never tried it in a 24mm EP in a slow scope. Will have to give that a try tonight in my C8 and see what happens.
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Bill
The KING: Any Eyepiece in the Focuser
The SUBJECTS: XT10i Dob---Meade 2080 SCT---TSA-102 S APO---Onyx 80EDF APO---SkyLight 60mm F15m---P.S.T.
If you want to make an apple pie from scratch, you must first create the universe. - Carl Sagan
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Glassthrower
Vendor - Galactic Stone & Ironworks
Reged: 04/07/05
Posts: 17931
Loc: Oort Cloud 9
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Bill, it's my understanding (I may be wrong) that there is an adapter which will let you use all standard 2" SCT accessories on the 127. Does this not include focal reducers?
--------------------
Michael Gilmer - Member of the Meteoritical Society & Collector of Falling Stars.
☄ ⒼⒶⓁⒶⒸⓉⒾⒸ ⓈⓉⓄⓃⒺ ☞ www.galactic-stone.com
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Quote:
Bill, it's my understanding (I may be wrong) that there is an adapter which will let you use all standard 2" SCT accessories on the 127. Does this not include focal reducers?
I use the F6.3 Celestron FR with my 5" Mak and 2" diagonals using a SCT adapter . I use up to a 2" 26mm SWA 70° with the F6.3 FR with no vignetting and a 40mm Pentax XW 70° eyepiece without the FR.
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Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 13646
Loc: southeastern Nebraska
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Tuugii wrote:
Quote:
FOV: Mak wins. Planetary views will be far better than C5.For DSO, C5 is better because it accepts 2" accessories so you can put a focal reducer.
Well, not quite. The C5 is an f/10 so it will have a focal length of about 1270 mm. With a 27mm maximum field stop diameter for 1.25" format eyepieces, this would yield a maximum true field of 1.22 degrees. A 5 inch Mak-Cassegrain like the Orion 127mm Mak-Cass is about f/12.1, so its 1540 mm focal length and with that same 27mm field stop limitation, it will yield a maximum true field of about 1.00 degrees. Thus, the SCT wins here with 22 percent more field of view than the Mak-Cassegrain (and at a lower power too, which is important for observing larger and more diffuse deep-sky objects). An exception to this might be the more expensive ITE M500, as it is also an f/10, so there would be no major difference in true field of view available between it and the C5.
Quote:
Cool Down: if you can put a simple ventilator then Mak wins.
The SCT can also be easily equipped with a simple home-brew ventilator as well, so any difference in cooldown time would be slight. It would be slightly shorter with the SCT due to its thinner corrector plate, but the difference would be minor.
Quote:
Ease of collimation: no doubt Mak wins. They're built like tanks.
Some are built like tanks and some are not. In terms of collimation, I had to collimate the Orion 90mm Mak-Cass, although the Orion Mak-Cassegrains usually do not need much collimation, although they are able to be collimated via three adjustment screws in the base. The C5 is easy to collimate (3-adjustment screws again, but on the secondary mirror) and holds collimation fairly well, so this is not a large factor in the choice.
Quote:
Portability: Mak wins.
Both scope OTAs (the C5 and the Orion 127mm Mak-Cassegrain) are very nearly the same size, so there is not exactly a huge difference in portability. The Orion 127mm Mak has a slightly longer tube (14 inches) but weighs 8.6 lbs compared to the Celestron C5's 11 inch long tube and 17.6 lb weight.
Quote:
Think about Intes M500, which is a better rig than both of them.
It may be, but not for the price. The OTA alone is around $885 which is more than a complete fully-mounted NexStar 5SE with Go-To and just over twice the price of an Orion Apex 127mm Mak-Cassegrain OTA. Clear skies to you.
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David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right."
Hyde Memorial Observatory
http://www.hydeobservatory.info
Prairie Astronomy Club
http://www.prairieastronomyclub.org
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Tuugii
professor emeritus
Reged: 03/22/07
Posts: 533
Loc: Ulaanbaatar, Mongolia
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Bill, Intes Micro M500 can be used with 0.55x reducer from Intes.
David, I suspect you didn't understood my points clearly. I know of course C5 would be better in terms of cool down times, weight etc. I just 'made' maks to win because Larry 'made' the C5 to win.
For planetary views the issue of FOV will be considered inversely. As you had stated 1.00 degree FOV would be better than 1.22.
And for the collimation, generally since the mak-gregory-cassegrains are slower systems, in order to get out of collimation they'll need more element displacement compared to the faster scts.
And for M500, I know it is expensive. But for optical quality, sturdy built, cooling, FOV and for collimating parts it will easily win both scopes.
But of course you'll need to pay some extra $$$ and extra weight.
clear skies to you,
Tuugii
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telescope=time machine...
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bobhen
professor emeritus
Reged: 06/25/05
Posts: 523
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It’s my understanding that the thinner corrector plate on the SCT is NOT an advantage in cool down time compared to the thicker Mak. Both are exposed to the outside air and both will cool rather quickly. The problem with both of these designs is the primary mirror. The primary mirror in both designs is not exposed to the outside air and so in both designs it’s the primary that takes much longer than either corrector to cool and will still be radiating heat when both correctors have long become acclimated to the outside temperature.
I doubt you will see much difference in the quality of view between these 2 mass-produced scopes. At this price point, the difference between same-scope samples might vary as much as the difference between the different designs.
People that have owned both designs seem to enjoy them both. If I had to pick, I’d pick the SCT for its versatility.
Bob
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BillP
Postmaster
Reged: 11/26/06
Posts: 9093
Loc: Vienna, VA
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Quote:
I use the F6.3 Celestron FR with my 5" Mak and 2" diagonals using a SCT adapter . I use up to a 2" 26mm SWA 70° with the F6.3 FR with no vignetting and a 40mm Pentax XW 70° eyepiece without the FR.
Joe,
Is that Celestron FR the same unit which fits on the C8? Reason I ask is that I have the FR for the C8, as well as a 2" visual back that fits those threadings.
Also, anyone know what the clear diameter of the baffle tube is in the 127 Mak? I understand the C5's (and 5SE I presume) is about 37mm...same at the C8's.
-Bill
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Bill
The KING: Any Eyepiece in the Focuser
The SUBJECTS: XT10i Dob---Meade 2080 SCT---TSA-102 S APO---Onyx 80EDF APO---SkyLight 60mm F15m---P.S.T.
If you want to make an apple pie from scratch, you must first create the universe. - Carl Sagan
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Joe Ogiba
Postmaster
Reged: 02/14/02
Posts: 5446
Loc: NJ USA
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Bill,
It's the same F6.3 FR I was using on my C9.25. The clear aperture of the 127mm Mak is under 37mm but it does not vignette with any combination that I use on my C9.25. Before I purchased the SCT adapter I held my 2" TeleVue Everbright diagonal to the back of the 127mm Mak and did not see any vignetting with a 30mm UWA 80° eyepiece.Since getting the SCT adapter I use the scope alot as a daytime spotting scope with F6.3 FR and 2" 26mm SWA 70° eyepiece and William Optics 2" erect image 45° prism diagonal. I think a 22mm Nagler T4 would be perfect since it has about the same 31mm fieldstop as the 26mm 70° and the 31mm aperture of the 45° 2" diagonal.
Joe
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Pentax PF-80ED,Meade 102ED APO,Orion EON 72,120ST
Apex 127,C6 XLT,CR150,C9.25,XT10 ,Celestron Regal 100 F-ED, CT152
Zeiss 7x42 FL,Canon 10x42L IS WP,15x50 IS
12x36 IS II , Pentax 8x32 ED
Garrett Optical 28x110 HD-WP Signature Series
Oberwerk BT-80 45, Apogee RA-88-SA
Denk II Power x Switch binoviewer w/13mm Ethos, 20mm Pentax XW's, 20mm Widescan III's.
21mm Ethos,17mm Ethos, 22mm Nagler, 40mm Pentax XW, 14mm Pentax XL, 5.2mm Pentax XL, 8-24mm Pentax XL Zoom, 31mm Axiom LX
Member #17
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rcg
Pooh-Bah
Reged: 04/27/05
Posts: 1436
Loc: Saint Charles, Missouri
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I got a great deal on a wegat optical 5" Mak from Ken Dauzat, basically a supercharged Meade with proprietary optics done to millitary specifications in a sharp white tube. F/15 focal ratio, a great planetary performer, hope to have a shoot out between it and my WO 110, should be interesting. Optically a Mak of comparable quality should beat an SCT with greater clarity and contrast.
Many SCT owners say that contrast is better in Maks, but SCT's beat them to death in price. F/ratio is the key to field of view. My Mak isn't designed for 2" eyepieces with a wide field of view because of the limited field size.
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Bob G.
8" F/6 Achromat home assembled on home made AltAz w/Pearl Nighthawk finder; currently parting out since return shipping fees for bad APM 8" Achro lenses are killing me  who would have thought you wouldn't get reimbursed for return shipping for optical junk? Live and learn!
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BillP
Postmaster
Reged: 11/26/06
Posts: 9093
Loc: Vienna, VA
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Quote:
I use the F6.3 Celestron FR with my 5" Mak and 2" diagonals using a SCT adapter . I use up to a 2" 26mm SWA 70° with the F6.3 FR with no vignetting and a 40mm Pentax XW 70° eyepiece without the FR.
Joe,
Thanks so much for the info and link. Good to know you can get an adaptor for the 127 Mak -- will make it much more flexible should I go that way. If you don't mind, could you measure the inside diameter of the baffle tube as it exits the unit. Some have said it is only 27mm which makes no sense. I would guess it would have to be at least 31mm or more to accomodate a 1.25" EP. This is a critical measurement so I can determine exactly what TFOV to expect if using a 2" EP.
Interesting about your 40XW working well visually. The Baffle diameter on my C8 is 37.2mm and similarly, even though the field stop of the 40mm Paragon is much more than this, it also gives an extremely nice wide afov with the C8. Without the reducer in place on the C8 the 40 Paragon gives me about 1.05 deg TFOV...with the reducer it is quite a bit larger of course. Not that I do wide field much, but is nice that the flexibility is there with either the C5 or the Orion 127.
-Bill
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Bill
The KING: Any Eyepiece in the Focuser
The SUBJECTS: XT10i Dob---Meade 2080 SCT---TSA-102 S APO---Onyx 80EDF APO---SkyLight 60mm F15m---P.S.T.
If you want to make an apple pie from scratch, you must first create the universe. - Carl Sagan
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