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More focuser angst - What is it with stock focusers?

swag72

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swag72

swag72

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I am embarrassed to say that my Equinox 66 that I have had since before the summer has just been hooked up to the camera tonight. I was a little concerned about getting focus and the spacing with the Atik 314L, but it was all fine, I should have been more concerned with keeping the focus!

So, what is it with damn stock focusers? The one on the Equinox 66 is frankly woeful. The SCT - 2" Baader adaptor, even with a rubber washer now attached is slopping all over the place and won't hold the weight of the Atik and filter wheel. The 2 screws and compression ring on the adaptor are awful, they do not hold anything square at all. I've taken everything apart at least twice to try to get it all together without movement, but it is not going to happen.

The focuser - Well, hex bolts tightened, various degrees of tension on the tensioning screw and there must still be a good 2-3mm of play in the thing. It flops about and the whole lot is quite frankly useless and unfit for purpose - Well, my purpose anyway! Not that what I wanted to do, take some images, is very much away from the norm!

So, looks like it will be a new focuser - wasn't expecting that!!

It is undoubtedly the weakest link, in what I think will turn out as quite a nice focal length with the 314L.

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ejwwest

ejwwest

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Your photos on Flickr are super. I just bought a Moonlite for my EdgeHD 925 but not had many clear nights since i got it for Christmas. First attempts are on my Flickr Orion Nebula | Flickr - Photo Sharing! and Moon and Lunar Craters | Flickr - Photo Sharing!

The focus is definitely better but I need to get better on the alignment and stacking.

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ejwwest

ejwwest

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@ejwwest - Cheers. The moonlite is great, works a treat on my other scope. There's loads of tutorials around for alignment, stacking and processing - Have you looed at thetutorials on here?

On alignment, I think it's more a question of actually doing it properly each time (though should I really expect to get better than 60" unguided?). I have noticed that I get better results if I'm more careful with the remote release on the Canon so as not to vibrate the system when exposing. On stacking and processing, I need to practice more. DSS is usually ok when I have a reasonable set of images. Registax is not so novice-friendly, at least for DSLR images. Once I get a CCD or similar planetary imager (looking at getting possibly an Imaging Source DFK 21AU618.AS), maybe I'll get to use it more.

Thanks

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Deneb

Deneb

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Personally i would not bother with replacing the focuser on the 66, sell the scope on & buy a better scope with a better focuser the new zs70 is suppose to come with a r & p. hopefully it won't be bad as a ddg.

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Psychobilly

Psychobilly

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I will try and dig out a few posts on setting up a crayford.. tightening everything is not neccessarily the right thing to do...

It will be when i fire up the pc later..

Until it had an accident my equinoxe focuser worked well with a heavy Nikon D200 and reducer fitted...Ok it still wasn't a moonlight but perfectly useable...

Peter...

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steppenwolf

steppenwolf

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It really is strange that these poor focusers seem to be cropping up everywhere - my old blue tube Sky-Watcher ED80 was/is solid as a rock, holds anything I attach to it and introduces zero focus shift when reversing focus travel direction. OK, it is only a single speed but this shouldn't affect the system, the mechanism for that is all buried inside the larger focus knob - what I have noticed (but only since I have started reviewing gear) is that it is (and always has been) smooth but 'stiff' to operate in comparison with the focusers on more current equipment.

Maybe we are all asking too much of our focusers and the manufacturers are producing silky smooth close to zero effort focusers to meet our expectations in this area while ignoring the downside to this philosophy?

My ED80 focuser moves well but there is a friction pushing back at the movement whereas, my new Baader SteelTrack NT for example will continue moving in or out if I 'spin' the focuser knob. Luckily, tightening up the focus lock does indeed lock it for me so I have the best of both worlds but the mass produced and cheaper standard focusers only seem to be able to do one thing or the other.

Old ED80 single speed Crayford, I salute you!

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swag72

swag72

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That's an excellent link Peter - Thank you.

@Steve - Do you think that the focusers are worse in the newer scopes than they were? Maybe something to do with competition and when optics are so very good, there is only the one place where they can scrimp?

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Stu

Stu

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Does anyone know of a similar document for the focuser on an Astro Tech 106EDT? Have pretty much always had a problem with it, it gets stuck at one particular point when winding back in and literally needs a shove to get it going again. Seems to hold ok once in position. The fine focus also has a little play in it which I would like to get rid of.

Stu

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steppenwolf

steppenwolf

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@Steve - Do you think that the focusers are worse in the newer scopes than they were? Maybe something to do with competition and when optics are so very good, there is only the one place where they can scrimp?
It's hard to say for sure, there have always been poor focusers - the ones in my SW ST80, SW 8" and 10" Newts were all pretty bad but you could swing your grannie on them and they wouldn't budge.

On the current budget Crayfords I think it is simply a trade-off between 'light and silky' v 'load bearing' - you need to pay lots more to both features and even then, you really need to go rack and pinion with fine teeth and impeccable engineering.

For example, my Baader SteelTrack NT is gorgeous but at £185.00 it was nearly half the cost of a brand new SW 250PDS which is essentially the OTA that I have fitted it to BUT my R & P Feathertouch focuser for my Refractor cost £660.00 !!!!! There are some quite desirable telescopes available for that sort of money ......

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Moonshane

Moonshane

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I think the average budget Crayford is fine for visual use. It's just when you start imaging that you see a need for the really quality ones I expect. I prefer a slightly stiff focusing action as this feels more robust and also prevents my eye socket pushing the focus out when using larger eyepieces. I have found that the slightest adjustment can often make a massive difference and it is often counter-intuitive what you need to ad as the article suggests.

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Moonshane

Moonshane

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Looking at it, the general principles of get everything level, even etc seem pretty universal to me and it's a bit like collimation I suppose. Understanding the effect of the adjustments on the system as a whole. Not that I know a lot about it!

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Stu

Stu

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Thanks Shane.

I guess it's just a matter of establishing which adjustment does what on mine. When I get over this lovely bout of man flu, I'll compare the instructions with what I've got and go from there

Cheers

Stu

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ollypenrice

ollypenrice

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My anti Crayford campaign is less of a one man band than it used to be, I see.

Get 'em outta here. Sure they can be made to work. You could make a Triumph Bonneville work - but not for long. Gimme a rack, gimme a pinion...

What bugs me is that there is no need for it. Just make an R and P. What's the big deal? It will happen when the market is ripe for a sales pitch along the lines of 'No cruddy Crayford on our models. We have real focussers here.' Since WO were the world Bad Crayford champions for so long it is no surprize to see them being first on the reformist R and P bandwagon!

Olly

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cathalferris

cathalferris

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I suppose the old style and quality of R&P focusers with their greasy racks and play-filled pinions with no real adjustment possibilities were in need of being superceded by the non-greasy and adjustable properly engineered crayfords. Nowadays with the increase in mass of the imaging trains put on small refractors that would only have at most a medium sized eyepiece on them 10-15 years ago has meant that some people run up to the limits of the mid-range crayford implementations.

I would expect that a well-engineered R&P may outperform a mid-engineered crayford, but I'll take the lack of touchable grease as a big advantage. The steeltrack type of design when well-implemented is the way forwards I think, and not back to the R&P. (opinion :icon_scratch: )

tl;dr horses for courses.

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