Many users find the primary mirror focusing mechanism of Schmidt-Cassegrain telescopes (SCT) cumbersome to use. There is some amount of image shift and precise focus cannot be found easily. This is inconvenient for visual use and a serious problem for astrophotography. GSO's (Guan Sheng Optical) latest Crayford focuser model is a gorgeous, all-black, rotatable focuser for Schmidt-Cassegrain telescopes that elegantly solves these problems.
CNC machined from aluminum and anodized black, this focuser will screw on to the rear cell of any* SCT telescopes sold by Meade and Celestron having a standard SCT thread. The standard SCT rear cell thread is 2" diameter male thread with a thread pitch of 24TPI (threads per inch).
This dual-speed Crayford focuser is a joy to use and you will wonder how you ever lived without it once you install it! By design, SCT Crayford focusers eliminate the annoying backlash and image-shift that plagues many SCTs. You will experience very smooth and precisely controlled focuser motion.
The inner drawtube glides on 4 precision bearings and a roller shaft. The inner barrel is baffled and painted a flat black to minimize reflections for maximum contrast. This barrel is also black anodized and features a laser-etched mm (millimeter) scale. It provides 1" of focus travel which is more than adequate for SCTs. You first use your SCTs focusing knob to achieve coarse focus and then switch to the Crayford focuser for finer focus and control. Depending on your range of eyepieces and accessories, you may never need to touch your SCT's main focuser again!
The 2" focuser barrel features a brass compression ring and can accept standard 2" refractor-type diagonals and other 2" accessories (Note that the use of this focuser converts your telescope's rear SCT thread to a 2" visual back. As a result you will not be able to use an SCT-type diagonal with this focuser; you will need a refractor-type diagonal instead). Also included is a 1.25"-2" adapter with brass compression rings and threads to accept standard 2" filters. This deluxe model features a 360-degree rotatable ring that allows you to orient the focuser (and hence your diagonal/eyepiece) to the most comfortable viewing position.
GSO's rated load capacity for their Crayford focusers is a little less than 6 lbs (2.7 kgs). The focuser also has two large thumbscrews. The thumbscrew on the telescope side can be used to lock the focuser, allowing the use of heavy accessories or cameras without fear or slippage or losing focus. The other thumbscrew on the eyepiece end can be used to adjust the tension of the focuser to achieve a focusing "feel" that you like. At the easiest (lightest) setting, the focuser moves extremely smoothly. At tighter settings, you can still use heavier accessories without sacrificing much of the smooth focuser action.
Please note that some larger Meade and Celestron SCTs (11" and larger) have a larger 3.25" rear thread, so please make sure that you have an adapter that reduces that larger thread to the smaller 2" SCT thread. If you have a standard 1.25" SCT visual back, all you need to do is unscrew the visual back and screw on the SCT Crayford focuser in its place. The focuser is shipped in a foam-fitted box.
• Minimum focuser height (with 1.25" adapter) = 4.29" (109mm)
• Maximum focuser height (with 1.25" adapter) = 5.28" (134mm)
• Minimum focuser height (without 1.25" adapter) = 3.90" (99mm)
• Maximum focuser height (without 1.25" adapter) = 4.88" (124mm)
• Tube travel = 0.99" (25mm)
• Focuser weight (with 1.25" adapter) = 1lb-10.5oz (751gm)
• Focus knob diameter = 1.57" (40mm)
• Microfocus knob diameter = 1.02" (26mm)
• Maximum outer barrel diameter = 3.3" (84mm)
-Thread: Standard SCT female thread (2" x 24TPI)
• Millimeter markings on focuser drawtube: Yes
• Rotatable: Yes
• Dust plug: One 1.25" dust plug included
Please note: Most GSO Crayford focusers have or will soon develop two bearing marks/lines on the upper side of the drawtube. This is caused by wear on the barrel anodizing where is makes contact with the roller bearings. In some focusers, you have to look hard to find these marks. In others, it is very prominent, even for brand new items received from GSO. This does not indicate a defective or used product and is essentially just cosmetic.
* Please also note: Some Celestron telescopes made in the late 1970s and early 1980s did not have a standard thread pitch. This focuser will not fit those, and there is no way for us to know what threads you might have on your telescope.
Aug 14, 2018
SCT Crayford FocuserPros: Cons: Comments:
I installed this Focuser after drilling and tapping mirror lock screws, works like a charm. Easier to focus than the stock knob with exact precision. My ASI 1600 is rock solid in this Focuser , I would recommend this to anyone that owns an SCT
This review was provided courtesy of AgenaAstro.comAug 14, 2018
Good focusing but mechanical design could be betterPros: Cons: Comments:
I've owned this focuser for about a year and a half now. It is a replacement unit (my Moonlight Optics unit was stolen) for my C9.25 OTA.
The good: reasonable cost, nice fit and finish, the focusing action works well, and the unit isn't as large and heavy as the Moonlight unit it replaced. Focusing is smooth, and the dual speed knob works as expected. I've read some other reviews that complain about the fine tuning necessary to have the focuser not slide out unexpectedly (like when slewing) but also still work. Mine seems OK in this regard, although the two locking thumbscrews are a bit touchy.
The bad: for SCTs it is critical to be able to turn the focuser on its axis and re-lock, as the OTA is slewed to different objects in the sky on a German equatorial mount, so that the focusing knobs and eyepiece can be positioned comfortably for viewing. This is where the GSO focuser isn't so great. The mechanism to allow the focuser to be rotated about its axis consists of an internal aluminum cone and three set screws through the outer shell. There is also a locking thumbscrew for this action. All of these screws have sharp edges that gouge the surface of the cone. With only a few nights of viewing under my belt with this focuser, I started noticing that when rotating the focuser, it started to feel rough. When I opened it up to figure out what was going on, I noticed that the cone is already damaged. I'll smooth it out somehow, and I've ordered nylon-tipped set screws so it doesn't happen again, but it would certainly be better to have this part of the assembly be better designed in the first place.
This review was provided courtesy of AgenaAstro.comJul 30, 2018
So Much Better!Pros: Cons: Comments:
I am a newbie with a nice Maksutov 180 scope. This focuser is vastly easier to use than the built in primary mirror adjustment knob ... very smooth in operation, and makes the scope a joy to use. I recommend it with enthusiasm!
This review was provided courtesy of AgenaAstro.comJul 28, 2018
Agena FocuserPros: Cons: Comments:
Don't do what I did and wait years to get a focuser like this for your SCT!
Spend $130 and get one of these. Take a minute to figure out which of the bottom knobs adjusts the tension and which one is the focus lock. Take another minute to get a feel for the right amount of tension for your setup and never look back. Love it. Thank you.
This review was provided courtesy of AgenaAstro.comJul 3, 2018
Crayford two speed SCT focuserPros: Cons: Comments:
Solidly made and well designed. Allows for fine focus without the image wobble that is associated with Meade and Celestron factory focusers. Easily threads into place to replace the factory visual back.
This review was provided courtesy of AgenaAstro.com
terrypaula Well-Known Member
- Skill Level
- Time with Product
May 2, 2018
- User Notes:
- Review by Terry
GSO 2" Crayford FocuserPros: Cons: Comments:
Excellent!! Great value The 10-1 ratio focus is what I needed to achieve fine focus on any object I choose.
GSO does it again. Don't tell them they will raise the price.
This review was provided courtesy of AgenaAstro.comMar 29, 2018
Works on the Orion 150mm Mak-CasPros: Cons: Comments:
I got this focuser for my new Orion 150mm Mak-Cas after doing quite a bit of research looking to see if anyone else had used it with the 150. I was specifically worried that the base of the focuser barrel would be too wide and would not fit between the opening in the rear cell and the stock focusing knob. The description of the focuser says: "Maximum outer barrel diameter = 3.3" (84mm)" which would have exceeded the available space from the center of the rear cell opening and the stock focusing knob. However, I did find a very old review entry saying that the focuser worked with one user's 150mm Mak but that reviewer was talking about the original Orion 150mm Mak-Cas and so they needed a step up adapter ring to go from the Mak cell threads to a standard 2" thread. Orion has recently brought the 150mm Mak-Cas "back by popular demand" but they've upgraded it now to include a standard 2" SCT thread (they don't even sell the adapter ring any more).
I took a chance and bought the focuser and I couldn't be more pleased with it! Not only does it fit perfectly on the telescope but it's a fine piece of machinery. It has a nice, clean, smooth motion with the added feature of a tension setting thumbscrew. I haven't actually used it "in the field" but I can tell it's a vast improvement over the stock focuser. Not only that the value for price ratio is through the roof ... it's a steal at this price!
This review was provided courtesy of AgenaAstro.comFeb 3, 2018
GSO 2" Crayford Focuser for SCTs - Dual SpeedPros: Cons: Comments:
Very nice focuser. Smooth operation. Friction adjustment allows for more or less tension as desired and it can be locked into position so that it does not shift focus as scope is moved. However, when used on my Celestron C-11 with Celestron focal-reducer it is almost all the way IN to its mechanical stop before focus is achieved. I have maybe 1 mm of additional inwards travel before hitting the stop. I am focusing my ZWO camera on the scope, then parforcalizing all my lenses to that setting. WITHOUT the focal-reducer installed there is more than adequate barrel travel for camera and lenses. In all, this is the best accessory I have installed on the scope.
This review was provided courtesy of AgenaAstro.comDec 30, 2017
a very nice accesoryPros: Cons: Comments:
I installed this on my Celestron C6. it's an amazing accessory, well-made. ... however the rotational ability doesn't really work on this focuser, it's better to adjust the focuser to a comfortable angle and then tighten the three screws and use it in a fixed position. this focuser holds my diagonal with heavy eyepieces in a secure position and it's a simple matter to slightly loosen the two setscrews and rotate the diagonal to change its position. The focuser itself works very well, smooth, fine focus adjustment is excellent (better than the one I had on my fsq) I run the drawtube halfway out and then I use the focuser on the telescope to focus the eyepiece, and use the fine tuning to get sharp clear focus. I use this with over 1.2kg of diagonal and eyepieces with no slippage at all .... it's very cool and makes my C6 into a high tech instrument that is more fun to use. it works well with all my eyepieces as well as Barlow. GSO's work is high quality and the price is unbeatable. but forget about the rotational ability , other than being able to set the rotational angle in a fixed position , so it doesn't hit the focuser knob on the telescope for example , but not changing it while using the telescope. I removed the adapter plate and screwed that on to my telescope first then I attached the focuser body using the three small Allen head screws.
This review was provided courtesy of AgenaAstro.comJul 25, 2017
Outstanding Quality of Product and ServicePros: Cons: Comments:
This focuser is heavy - not heavier than is necessary and is very well made and finished in high quality material.
I received it on time and was well advised about my shipping options by Agena. I therefore also received it in one piece!
This review was provided courtesy of AgenaAstro.comMay 25, 2017
GSO 2" Crayford focuserPros: Cons: Comments:
Good quality and price. Nice to fine focus an object. Unable to rotate the focuser 360 degrees because it hits the SCT primary focus knob. I also find I still have to coarse focus with the SCT stock focus.
This review was provided courtesy of AgenaAstro.comOct 9, 2015
Not bad for the pricePros:
Lightweight,Easy to Use,Compact,Very Nice Fine Tuning,Strong ConstructionCons: Comments:
Very fine focus and solid construction. Took a bit to learn how to lock down or loosen up. Both screws next to each other so oops. It won't focus top all the way to bottom without special adjustments but still worth it.
This review was provided courtesy of AgenaAstro.comMay 30, 2013
Fantastic - works very wellPros:
Quality Lenses,Accurate,Strong Construction,Easy to Use,CompactCons: Comments:
Fantastic - works very well on my Celestron 9.25 giving me much better focus adjustment
This review was provided courtesy of AgenaAstro.comFeb 13, 2013
Works on my Orion 150mm makPros:
Easy to Use,Strong Construction,AccurateCons: Comments:
I was looking at the Moonlites, the Baaders and finally settled on the GSO because of the decent price and my actual needs as a visual observer. This focuser is a great solution and addition to my OTA for combating the image shift that I was experiencing with the built in focuser. Solid and seemingly well constructed, I was not disappointed when I took it out of the box and inspected it; the focusing is smooth and especially fine when using the micro focus knob. The only thing that some folks might have a problem with is that this is the "lightweight" version of GSO's external SCT focusers and if you do not properly set the tension screw on the base, the tube may "slip" out to its extents; merely the mechanical reality of the design. In order to fit this onto my Orion 150mm Mak, I had to buy Orion's Mak to SCT adaptor ring; this is something that Orion should consider including with their OTAs. The GSO SCT focuser is a very nice piece of hardware for a very decent price.
This review was provided courtesy of AgenaAstro.comJan 1, 2012
Not a bad focuserPros:
Well Made,Economical,Strong Construction,Easy to UseCons:
Nice focuser for the price. We used this to replace the motorized focuser on our 12" LX200 GPS scope. We found that unless the focuser is fully in when observing something directly overhead the focuser hits the fork mount. It needs to be made so that with the focuser fully extended it would miss the fork. Also if the locking srews are not snug and you are viewing directly overhead we find that the adjusting tube of the focuser slides out to its fully extended postion. To stop this from happening we snug up the locking screws but then you cant use the focus knobs. A micro fraction of a turn prevents you from focusing and a micro fraction of a turn lets the tube fall to its fully extended postion. There does not seem to be any happy medium. All and all the two speed focuser should be rated on a scale of 1 to 10 as a 7.5.
This review was provided courtesy of AgenaAstro.comDec 18, 2011
Great Focuser for 127mm MakPros:
Easy to Use,Accurate,Strong ConstructionCons:
I purchased this GSO dual speed focuser for my Sky Watcher 127mm Mak-Cass for more precise focusing than the mirror focuser provides and to work around image shift.
An SCT to MCT adapter ring is required to fit the focuser onto the SW OTA.
Note that the SW 127 Mak stock focuser knob needs to be removed to accommodate the 84mm Crayford circumference. There is ~3mm clearance between the Crayford knurled ring and the Mak focuser stem.
I covered the brass stem with 1/2" vinyl tubing (3/8" inside diameter) to prevent it from slipping into the OTA and provide a bit of grip. Obviously this is NOT a recommended procedure and could void the OTA warranty.
I am very impressed with the GSO focuser construction. It's solid, well appointed and has an elegant appearance. The compression rings and tension control are nice touches as is the ability to rotate the focuser.
The tension control does need to be tight enough to bite into the drawtube somewhat otherwise changing eyepieces is enough to move it out of position. Obvious but worth mentioning.
Also of note is some mounts may not provide enough clearance to view at zenith with the Crayford focuser installed.
Weight may be a concern. As a small measure of insurance I replaced SW's stock dove tail (screwed directly into the OTA) with 144mm tube rings which have much heftier screws.
I'm spending less time messing around with focus and more time observing... well worth the investment even for a small instrument. I've been able to tease more detail out of Jupiter than is possible with the integrated focusing mechanism coupled with the consistently bad seeing here.
This review was provided courtesy of AgenaAstro.comJun 3, 2011
Great value and quality!Pros:
Strong Construction,Accurate,CompactCons: Comments:
Perfect for my 8" vintage Celestron!
It greatly improves my focusing ability over the stock focuser. It's light weight - much lower than other brands - helps with balancing the scope on my mount. It holds my camera and eyepieces well. Great value compared to other brands.
This review was provided courtesy of AgenaAstro.comDec 19, 2010
Great addition to SCT!Pros:
Accurate,Strong ConstructionCons: Comments:
I added this to my SCT so that I could use 2" eyepieces, and it's been a wonderful upgrade.
Adding the dual-speed focusing capability makes focus adjustments much quicker and easier. It's very sturdy and has no trouble locking the focusing tube even with a heavy 2" diagonal and eyepiece.
One thing that I didn't realize when purchasing is that you'll still need to use the SCT internal focusing mechanism even with this focuser. Once you have it sighted into infinity you can rely on the fine focusing knob, but don't worry if you're still using the internal one as well.
This review was provided courtesy of AgenaAstro.comDec 18, 2010
Crayford for an SCT in AstrophotographyPros:
Well built quality,Precision,Strong ConstructionCons: Comments:
I purchased the GSO dual speed Crayford basically to use as a precision focuser in a 11 inch Celestron SCT. I still have a fine feather touch as the main focuser for visual, but when doing Astrophotography, the GSO really helps by avoiding the shift of the mirror and keeping the planets in the middle of the computer screen. I also added a Rigel Systems motor to the GSO making it a very cost effective solution. Feather touch and other high end brands have fine focusers but they are so highly proceed that adding that cost to a AP setup becomes too much, especially when you need to add cameras, dew shield and controller etc.
This review was provided courtesy of AgenaAstro.comJun 9, 2009
Great SCT FocuserPros:
Strong Construction,AccurateCons: Comments:
I bought this focuser for the fine focusing that I can achieve on my telescope.
It's silky smooth and strong construction make it joy to use.
I have used a 2in. dielectric diagonal with 40mm eyepiece with no slipping.
It also handles my Nikon D50 with no problems, I'm very pleased with this focuser.
This review was provided courtesy of AgenaAstro.comMay 29, 2009
New life for my LX-10Pros:
Accurate,Smooth Operation,Strong Construction,Stable SettingsCons: Comments:
This well made little focuser has greatly improved the usability of my venerable Meade LX-10. By adding this GSO 2, I now can view the heavens without the continuous frustrations associated with the age-old primary mirror shifting focus problem. The GSO 2 fits the OTA back so well it looks like it was part of the original design.
This review was provided courtesy of AgenaAstro.comMay 28, 2009
Superb for visual, but light for cameraPros:
Strong Construction,Smooth MechanismCons:
Needs counterweight,Lock not tight enough,HeavyComments:
It's excellent for visual observing, a bit light for camera attachments.
When attached to a Celestron Schmidt-Cassegrain CPC-11 telescope, you will need a counterweight when photographing. Otherwise the tripod motor clutches will slip.
When inserting a Nikon D100 DLSR camera into the 1.25" holder, use a safety strap. The thumbscrew lock may allow your camera to slip out and fall when it's pointed straight up, like when looking at Vega. (Our camera fell onto the concrete--didn't hurt it this time.)
I like the brass internal protector ring, that stops your eyepiece lens barrels from being scratched with the lock screws.
The mechanism feels smooth and it focuses precisely. Although it's rated for 2700g, for our 800 gram Nikon, it wouldn't stay where we put it. The hanging weight slowly pulls the mechanism away from where we had set it. You can tighten the Crayford drag screw which helps. But then it's not smooth anymore.
This review was provided courtesy of AgenaAstro.comMay 27, 2009
It was exactly what I expected to bePros:
Strong Construction,Compact,AccurateCons: Comments:
It was exactly what I expected to be - compact, well constructed, fine focusing, reasonably priced. I have been told by a friend to buy and I recommend it too.
This review was provided courtesy of AgenaAstro.comMay 27, 2009
Strong and heavyPros:
Good design,Strong ConstructionCons:
I use this product with my LX200 Meade for astronomy. Is very good, smooth and solid, but perhaps heavier than other brands. I like it
This review was provided courtesy of AgenaAstro.comMay 26, 2009
This focuser works as I had hoped. The rotation feature is very handy to keep the knobs in a consistant location for focus. The fine focus works very well and very smooth. All in all, just what I was looking for.
This review was provided courtesy of AgenaAstro.comJan 8, 2009
Cannot do without it.Pros:
Strong Construction,AccurateCons: Comments:
I use it on my Skywatcher MAK180, with an adapter ring.
Now focus is easy and perfect. It's very smooth and precise, absolutely necessary for high resolution photos.
Just make a coarse focusing with SCT rotating knob and then obtain fine focus with crayford.
This review was provided courtesy of AgenaAstro.comSort by
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