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Antares 2" Helical Focuser


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Hi all

I am currently looking at ways to reduce overall weight on a suitcase dobsonian I am making. one way to do this is to reduce the weight of the focuser. As the scope will be a travel dob, it really does not need a dual speed focuser which I originally planned to instal.

Therefore I looked around and although there are some good helical focusers on the market from Borg and Kineoptics, these are quite expensive at just a little less than a new single speed Moonlite!

Therefore I took a punt on this item from Rother Valley Optics.

http://www.rothervalleyoptics.co.uk/antares-2-inch-helical-focuser_d2474.html

At £45 delivered it was not expensive and I am really quite pleased with it.

I'll review this with pros and cons (albeit I have not actually installed it yet.

Pros

  • Very solid and light - 300g without an adapter
  • Came with a 2"-1.25" adapter included
  • Very smooth and easy rotation
  • Small footprint
  • Fits a wide range of scopes

Cons

  • The grease on the threads is really awful - I cleaned this off immediately
  • After cleaning off the grease there is a little play in the threads although it's still nice and smooth
  • Thumbscrew only fittings

The focuser has a little play after cleaning off the grease but in operation this will not matter as the weight will bear down on the threads and retain it in one relative position. I am not worried about this.

I'll be using only 1.25" eyepieces and have an adapter with compression rings and a Baader fine tuning ring so I can use 2" filters.

Typically, I think I can do better than the manufacturer and have already modded as follows:

Taken off the rubber feet as I will be using it on a flat base

Changed the steel thumbscrew for a nylon version

Removed the grease as above

I'll also be redrilling tapped holes in the outer corners as the current fiving points seem to be far too close to the focuser hole for my liking. this will provide a mich firmer attachment.

On the whole this is a superb bit of kit subject to the above provisos for the money. If you can afford a single speed Moonlight then this might be a good option (not sure of the weight of that though) at three times the price obviously.

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A good helical focuser can be lovely to use. Supremely easy to find best focus and sooo smooth. It has it's downsides too of course.

I've got a nice, but limited range one, on my Tal M and a couple of old eyepieces that have this feature.

I looked at these a while back, but put it on the backburner due to not knowing the exact dimensions.

Could I be a pain and ask for some sizes?

Does the helical drawtube poke out from beneath the base when fully retracted?

7255316160_e966019cf7.jpg

Cheers,

Andy

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Hi Andy

I'll check the dimensions when home later.

Hi Michael, I'd be worried about other greases to be honest as it would be inevitable in my view that youd be constantly having to wipe your fingers as you'd get grease on them off the exposed threads. maybe some PTFE tape round the threads might be a better idea, albeit more 'ugly'.

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Thanks for that. Would regreasing the focuser with a different type be worth considering?

If you want to lubricate it without messy greases? You could try some of this Michael. http://www.3inone.com/products/dry-lubricant/

We use similar lubes on stuff like table saws router jigs etc. it lubes without leaving a sticky surface that the sawdust can stick to. It also avoids getting messy grease all over prepared timber. I would give it a bash.

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It is very smooth without the grease so lubrication is not the issue, it's the small amount of play in the threads (usually taken up by the grease) that's the problem.

the (small) weight of the barrel and the eyepiece will make the threads sit down though so I don't see this as a problem (and when you collimate it will be the same thing with the cheshire acting like the eyepiece).

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lapping paste could eventually make the play worse. So no, I wouldn't use that. Every time you turn the focuser you'd in effect be grinding the threads down, probably making them looser, I reckon.

Andy.

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A good helical focuser can be lovely to use. Supremely easy to find best focus and sooo smooth. It has it's downsides too of course.

I've got a nice, but limited range one, on my Tal M and a couple of old eyepieces that have this feature.

I looked at these a while back, but put it on the backburner due to not knowing the exact dimensions.

Could I be a pain and ask for some sizes?

Does the helical drawtube poke out from beneath the base when fully retracted?

7255316160_e966019cf7.jpg

Cheers,

Andy

Hi Andy

Measurements as follows:

rubber grip = 12mm total

base width = 65mm square

base thickness = 10mm

base tube height = 23mm on top of base thickness

I reckon you could get away with a total extended height (no adapter) of 90mm (this is with two full turns of thread in the base) and with the thread wound all the way in, the threads extend about 23mm below the base (although this is with rubber feet removed - with them on it would reduce by 6mm).

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If you want to lubricate it without messy greases? You could try some of this Michael. http://www.3inone.com/products/dry-lubricant/

We use similar lubes on stuff like table saws router jigs etc. it lubes without leaving a sticky surface that the sawdust can stick to. It also avoids getting messy grease all over prepared timber. I would give it a bash.

hi mate

would this be similar enough?

http://www.ebay.co.uk/itm/Finish-Line-DRY-Bike-Bicyle-Cycle-Chain-Lube-2oz-60ml-/310394164086?pt=UK_SportGoods_CyclAcces_RL&hash=item4844ef1376

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latest pics showing the Helical focuser in position. I had to file down one side of the provided washers to a flat as far as I dared as they touched the threads of the focuser - seems a silly mistake to me. you literally could not wind in the last 20mm of threads without this mod. another thing to note is that as this is made in Canada (so I noted on the box) the sctrews (and threaded holes in the base) are an oddball imperial size - possibly 3/16ths? (close to M4 anyway).

however, I am now happy I made this decision. It works well is very solid and just needed some slots cutting out from the 50mm hole to allow fitting.

the threads wind out a lot further than I expected too. the extended photo is with two full turns of thread inside the base. I'd not hang a 26mm Nagler off it but a plossl? there's also more ability to course focus with the 2-1.25" adapter and then fine focus with the threads.

post-17776-13387777902_thumb.jpg

post-17776-133877779025_thumb.jpg

post-17776-13387777903_thumb.jpg

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Nice pics. Gives a better idea of what this focuser is like, than the stock one. In fact the stock photo does it no justice. Very impressive.

Wow, that can screw out a hell of a way !!

Andy.

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