mooreorless
Carpal Tunnel
Reged: 07/05/05
Posts: 1514
Loc: Cornpropst Mills,Huntingdon,Pa
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Hi Don,Thanks for taking the time to post this information on how to do this,I'm sure it will help this guy a lot.I have been checking out Cloudy Nights for a good while and finally just signed up recently.I just never took the time to do it.The baffle on these Orion scopes must be a pretty bright finish to cause this much problem,well I guess it doesn't have to be that bright that is why they make flocking paper.Once again Thank You, Dimitri and Stephane.I'll let you know how he made out or better yet have him tell you.
Steve M
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Regards,Steve M
"the eights are better" Jim Carmichel of Outdoor Life magazine
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stevie
Spiderman
Reged: 12/07/03
Posts: 3135
Loc: Belgium
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glad to be of service
hello again Dimitri 
so it seems everything worked out for you ? 
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tolmac
journeyman
Reged: 07/31/05
Posts: 7
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Just curious Greg, was the Mak properly cooled when you tested it against the Meade 127?
Also, I've found that the primary in the Orion Maks are not under sized according to my tests using a laser perpendicular to the meniscus. The light beam hits the primary as soon as it passes the edge and enters the light path. I could not detect any light going past the primary. Just musing.
Tony
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102/F5
150 Mak
AstroView EQ/HEQ5
15x70 bino
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Starman1
Postmaster
Reged: 06/24/03
Posts: 10847
Loc: Los Angeles
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Quote:
Also, I've found that the primary in the Orion Maks are not under sized according to my tests using a laser perpendicular to the meniscus. The light beam hits the primary as soon as it passes the edge and enters the light path. I could not detect any light going past the primary. Just musing.
Tony
The steeper the curve, the more divergeance it has. Meade makes a point of using an 8" primary on their 7" Mak.
The entrance pupil is the diameter of the corrector, but to field that light does require a primary larger than the corrector.
How much larger is a calculation an optician should be able to provide.
Your laser should not be perpendicular to the corrector's surface, but its beam should be parallel to the tube for On-axis rays. Tilt the laser slightly sideways to simulate off-axis rays.
In my Orion 127 Mak, a laser beam shone into the tube , kept parallel to the tube, hits the edge of the primary mirror well before the beam gets to the edge of the corrector, indicating that the undersized primary significantly vignettes the light from the edge of the corrector. It's difficult to evaluate perfectly, but it appears that the amount of corrector that actually casts its light on the primary mirror is less than 120mm.
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Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie
Edited by Starman1 (07/31/05 02:04 PM)
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tolmac
journeyman
Reged: 07/31/05
Posts: 7
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Perpendicular to the corrector is the same as parallel to the tube I would think, but I didn't allow for stray light and didn't angle the laser because stray light hinders the image, doesn't it? It's not something we want, is it? The beam hit the primary even before it left the useless beveled inner edge of the corrector and I double checked my test rig for squareness.
I would be interested in getting some of the pro-optitians involved in this.
Your response was greatly appreciated.
Regards,
Tony
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102/F5
150 Mak
AstroView EQ/HEQ5
15x70 bino
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Starman1
Postmaster
Reged: 06/24/03
Posts: 10847
Loc: Los Angeles
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Perpendicular to the plane of the corrector would be parallel to the tube, but perpendicular to the surface of the corrector would be substantially angled. That's why I made the clarification.
I had the back of the tube open and a bullseye there. When the laser beam hit the middle of the bullseye, I knew it was "on-axis".
I moved the beam sideways toward the edge of the corrector, keeping the beam centered in the bullseye on the rear of the scope. The beam reached the edge of the primary mirror several mm before it reached the edge of the clear aperture of the corrector.
My corrector is 124mm wide in clear aperture, and the beam hit the edge of the primary mirror about 4mm in from the bevel on the edge of the corrector (116mm diameter, or 58mm radius). At the edge of the usable corrector (124mm diameter), the beam hit the inside diameter of the tube, reflected off the tube onto the mirror as a diffuse beam and put enough light on the rear-mounted bullseye to see. This is proof-positive the inside of the tube is too reflective and can cause a glow in the field of view when viewing bright objects, even on axis. This would be even worse for off-axis light rays.
If the bullseye technique is not good enough to guarantee perpendicularity of the beam to the plane of the corrector, I'll allow a little "fudge" factor and call it a 120mm scope.
At 1540mm of focal length, that makes the f/ratio 12.8 to 13.3 depending on the accuracy of the bullseye method, but definitely not f/12.1.
IMHO, Orion should not advertize this as a 127mm aperture.
I am going to presume their "150mm" aperture is similarly smaller than its true effective diameter, but by how much, I do not know.
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Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie
Edited by Starman1 (07/31/05 07:39 PM)
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Greg W
member
Reged: 02/26/05
Posts: 28
Loc: Wales, Maine
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Quote:
Just curious Greg, was the Mak properly cooled when you tested it against the Meade 127?
Tony
Yes. The Meade also takes a while to calm down. The scopes were out for about 2 1/2 hours.
Greg
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Dylan Gladstone
scholastic sledgehammer
Reged: 08/05/07
Posts: 912
Loc: Connecticut, USA
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Thanks for this thread everyone!
I have that same "loop of light" when a bright object is just out of the field of view with my 127 Mak. I was considering dismantling the scope to flock the inside. Searching on "flocking" and "127 Mak" I came across this thread.
I'll try just flocking the inside of the baffle using Don's instructions.
Will this also increase contrast a bit?
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Orion SkyView Pro 127mm Maksutov
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bobmarleyou812
member
Reged: 01/18/08
Posts: 40
Loc: Poway, CA
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I'm quite happy with mine. I'm in the process of "fine tuning" the collimation, but then again, is it ever going to be perfect? I get good feedback from other people looking through it in star parties. It's my first scope so I really have nothing to compare it to as far as previous scopes. A little more aperture would be nice as I've noticed a dramatic increase in detail with larger scopes, like big scts and dobs, but then you get into portability and other issues so it turns into comparing apples to oranges.
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150 mm Orion Mak Cass
Sky View Pro EQ
Meade 5000 26 mm
Meade qx 20 mm
Meade qx 15 mm
W/O spl 12.5 mm
S/V enhanced diagonal
9x63 Celestron Ultima Binos
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sang33ta
professor emeritus
Reged: 07/08/08
Posts: 537
Loc: UK
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As an alternative you can read my Hioptic 150mm Mak review in my signature, I think they get sold under the brand AstroZap in the USA.
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Hioptic 152mm f12.5 Maksutov
Celestron Advanced CG5-GT Mount (Mr Noisy!)
Meade 4000 Super Plossl Set
Casio QV-2900UX
Got fed up of waiting for Meade ETX-150 so put this together for £500/$1000
Edited by sang33ta (08/08/08 07:50 PM)
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Mert
scholastic sledgehammer
Reged: 08/31/05
Posts: 940
Loc: Spain, Pamplona
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In another thread I posted a Roddier test result
that seems to show near perfect optics.
Maybe I just was lucky but seem to remember I read
more results from others confirming good optical
quality on these OTA's.
For me it's a keeper!
Regards,
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Mert
42º49"N 1º38"W
3" Unitron refractor
6" F12 SW Maksutov,CS2-S
EQ6 + EQMOD 
Webcam with 1.25" nosepiece
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jrbarnett
Carpal Tunnel
Reged: 02/28/06
Posts: 2475
Loc: Petaluma, CA
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Mert:
Mine was very nice as well. I think optically they are very high quality.
To Don's point about undersized primaries, that well could be the case. While I loved the sharp images of my Orion, it was noticeable less bright at the same magnification on the same targets than one of my observing buddies' C6 XLTs. I never thought to use a laser to try and verify the vignetting.
Regards,
Jim
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Obsession 15" Dobson
Orion XT10 Intelliscope Dobson
Intes-Micro M715 MCT
Meade 127ED APO
D&G 5" f/10 achromat
Antares Elite 105mm f/14.4 achromat
Pentax 105-SDHF APO
Televue TV-102 APO
Takahashi FS-78 APO
Sears 60mm f/15 achromat
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Mert
scholastic sledgehammer
Reged: 08/31/05
Posts: 940
Loc: Spain, Pamplona
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That's interesting Jim, likely the XLT coatings
of the Celestron are superior to the Skywatcher's
or Orions's coatings.
IMHO this OTA for me is a "great" little scope and
worth it's money.
Regards,
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Mert
42º49"N 1º38"W
3" Unitron refractor
6" F12 SW Maksutov,CS2-S
EQ6 + EQMOD
Webcam with 1.25" nosepiece
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cuir
scholastic sledgehammer
Reged: 03/03/07
Posts: 812
Loc: 45° 1'12.78" N, 73°56'12.25" W...
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I have the blue tube 150mm skywatcher Mak. It's Keeper.
Quote:
noticeable less bright at the same magnification on the same targets than one of my observing buddies' C6 XLTs
You sould compare at the same exit pupil, not magnification. It's the only fair and level playing field you can use for a comparison of the potential differences incured by vigneting. The scopes have different focal lengths, so an Exit Pupil match is required to do a fair comparison of brightness. The C6 has a larger central obstruction, wich makes it a little less sharp. On the whole, they are probably closer in performance than most would care to acknowledge. I like the Mak, and won't change it for a schmidt, unless it is for a C8 or larger. This is a very subjective choice, though.
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Seb
Eyepiece philosophy - The right eyepiece.
EP spreedsheets v. 6.6 - Numbers do matter.
Main scope: 150mm Skywatcher Maksutov
Favorite ep: 24 Panoptic
Pref'ed filters: Lumicon 0III and UHC
Mounts: EQ6-Pro and Skyview AZ
Just in: C8-S-XLT
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