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Skywatcher Dual-Speed 2" Low Profile Crayford Focuser

johninderby

By johninderby
in Member Equipment Reviews

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johninderby

johninderby

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Skywatcher Dual-Speed 2" Low Profile Crayford Focuser - Mini Review

Got one of these from Steve earlier this week and fitted it to my Skywatcher 250PX dob. As advertised it was a straight bolt on replacement for the stock focuser. It doesn't come with any bolts though so make sure to keep the ones from your old focuser. I set mine at an angle because it is just easier to use this way. On the 10" tube the base just about touches the tube in the middle so I'm not sure how well it would fit the 8". Probably would just slightly flatten the tube where the centre of the base contacts. The 12" will be fine.

When I first tried using it the drawtube rocked from side to side by an alarming amount when it was extended. Also the focusing action felt a bit rough. Tried adjusting the tension screw but it didn't help. After trying several things I finally found the answer. There are four silver hex screws around the black tension adjusting screw. A quarter turn clockwise on all of the four silver screws took the slop out of the drawtube and also the focusing action smoothed right out. Now it was comparable to the focuser fitted to a Skywatcher Equinox refractor.

Now to the unique feature of this focuser. It has a built in 44mm long 2" extender tube. Essential as the drawtube has only 24mm of travel. The combination actually works quite well. Set the drawtube to about half travel. Loosen the extender tube and slide it out to approximately focus the eyepiece and lock it off. Now you've got plenty of focus travel. Most eyepieces are going to need the extender pulled out quite a bit. For visual there is far more infocus travel then you'll ever need. Bodes well for those using this focuser to image with a newt. When the drawtube is all the way in it just intrudes into the tube by about 1/4 inch or so.

One other point. The 1.25" adaptor that comes with it is useless as an eyepiece adaptor. It takes considerable force to get a 1.25" eyepiece into it, enough force to scratch up the eyepiece barrel. However it makes a great holder for a collimating cap so it's not a complete waste. I replaced it with a WO 1.25" adaptor.

To sum it up:

Well made and nicely finished. Focusing action now feels nice and smooth and works well for visual use (not tried any imaging so not sure what the weight capacity is), and while it isn't as good as a top end focuser such as a Feathertouch of course, I'm happy with it considering I only paid just over £100.00. Good value and it does what it claims to do......bolts straight on in place of a stock Skywatcher focuser. Only irritation is that It wasn't adjusted properly in the first place.

John

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DIYASTRO

DIYASTRO

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John,

Nice report, looks just the biz! Hope it works out well on your newt.

Can you tell me how the barrel is fitted to the fixing plate? My thinking is that perhaps this (the base plate) may be exchangeable with the one that I have. Perhaps if it is easy to remove ( mine has a couple of grub screws in base plate) you may be able to tell me the diameter of the crayford barrell. It should have an inverted 45 deg chamfer on it and with luck will measure around 78mm

Thanks

Boyd

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DIYASTRO

DIYASTRO

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John,

That is very thoughtfull and very helpfull. I think that it will be poss. to put the low profile crayford into the plate that I have. The problem with the taller crayford as all with DSLR will tell, is that you can only just achieve focus so the lower profile one should do the trick. Thanks again.

Boyd

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zcapp96

zcapp96

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John,

Thanks very much for that. I think I may just risk the purchase of one of these and try to fit it to my 200mm newt. Thanks again

Boyd

Please let us know how that turns out! I've been looking for a solution for DSLR imaging on my 200mm newt and have been considering this focuser as well.

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John

John

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Hi Boyd

The base plate has an 80mm opening (measured with digital calipers). The botom of the barrel is about 78mm with about a 30 degree taper so yours might fit.

John

Interesting - pretty much exactly the same as the base plate and barrel of the GSO single speed crayford on my Lightbridge 12".

Hmmm ...... I might give that a go as well.

John

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DIYASTRO

DIYASTRO

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I have taken the low profile crayford off my SCT and fitted that to my 200mm newt and it works with DSLR perfectly. I will not be buying another crayford since all I have to do is slacken two grubs and I can interchange from newt to SCT in about 60secs!

I am sure that the skywatcher will fit though.

Boyd

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johninderby

johninderby

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Looks like it should fit. The hole through your OTA tube is smaller than a Skywatcher, but the base of the focuser doesn't stick through into the OTA anyway, only the focuser tube it's self which is a standard size and so will fit.

The only potential problem I can see is with the grub screws that lock the focuser into the base. How far are they down from the top edge of the base plate? Let me know and I'll check to see if they would work.

Here's a photo of the focuser looking from inside the OTA. Brighness has been increased a lot to show some detail so the black inside of the tube doesn't look black at all.

John

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Rob

Rob

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thanks for that. looking at picture 3 looks to be around 1.5 mill down from the edge (thats the edge of the main crayford body on show in the picy).

Hope that may give a guide?... cheers Rob

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johninderby

johninderby

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Hi Rob

Measured the focuser and base dimensions and made a very rough sketch.

The tapered bit on the bottom of the focuser is 4.7mm high and the grub screw in the base is 2.5mm (screw centreline) down from the top of the base.

Hope that's enough to find out if it will fit.

John

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johninderby

johninderby

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Hi

I checked the focuser and the body is 83.7mm in diameter and the bottom taper bit is 79.8mm at it's largest diameter so it just fits into the base.

Could you borrow a set of digital calipers to check the base opening?

John

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Doc

Doc

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attachment.php?attachmentid=19517&stc=1&thumb=1&d=1236014273

Is it possible to use these threads on the end of the drawtube for filters. By placing a 2" light pollution filter here it means no fiters on the eyepieces.

Am I right.

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terryf

terryf

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Hi,

I've just received one of these from FLO without being completely sure if there would be enough back-focus on my 250PX. Well I need not have worried - I haven't measured it, but there has to be 10-15 mm inward travel still at prime focus with my 350D, and the slow speed control really makes focusing easy. And amazingly, its arrival did not bring on the 40 days and 40 nights of continuous cloud cover that normally goes with this kind of purchase. Now I can start thinking about that Baader Coma Corrector...

Terry

Please let us know how that turns out! I've been looking for a solution for DSLR imaging on my 200mm newt and have been considering this focuser as well.
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  • 7 months later...
Phil_H

Phil_H

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Hi John, just read the review and noted that you state "base is 105mm by 115mm and the holes are 85mm apart".

I have an old blue sp250 and the holes appear to be 85mm spaced in one axis (tube length) and 82mm in the other axis ( circumcerence) when measured on the focuser base top ( pozidrive heads).

I wonder if the dual is only a drop in replacement on later tubes ?

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johninderby

johninderby

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Hi

I sold that particular dob but I have another SkyWatcher dob. I took a quick look and measured over the top of the base (same one that comes with the low profile focuser) and I get 85mm on the tube axis and 83mm on the circumference. There is room in the base for the bolts to swing a little bit in the circumference direction which should accomodate a few mm difference in hole spacing.

The low profile focuser can come with two different bases. FLO supplies the correct SkyWatcher base. I'm not sure about other dealers.

John

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  • 5 months later...
Moonshane

Moonshane

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I really want one of these for my Orion Optics UK 12" dob. it's one of the GPDX models and hopefully it will fit or be an easy replacement. looks like it from the pics etc.

Just need to get my final Radian (12mm) so will be looking to get one for summer.

I bought the refractor version - lovely and smooth. the extender sleeve is a fabulous addition - really well thought out.

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