Upgrading my ST120 focuser

[baggywrinkle]

I bit the bullet and ordered the Telescope Service Monorail focuser http://www.teleskop-express.de/shop/product_info.php/info/p3945_MONORAIL-2--Refractor-focuser---e-g--for-Skywatcher-96mm-flange.html

The idea being to give the scope better focusing capabilities with a camera attached.

The TS focuser is extremely well made and solid and as can be seen from the pics below is of a much higher quality and finish.

Fitting is simple, just three screws. Time taken, about 10 minutes.

There is a nice tensioner knob to stiffen the 10:1 focuser, plus a knob to lock it in position. The whole assembly can be rotated with a camera in place via the use of a 3rd locking nut.

It has compression rings for 2'' and 1.25'' diagonals and EP's.

The only problem it has left me with is how to mount a finder scope of RDF? There is no shoe to take the base. Advice please...

[Macavity]

Glad it fitted (Knew you would check!) ST120s as well as ST102s!

Looks like quite a few scope types will accept the same focusser size...

I have stuck things to GSO focusser barrels using (a cut down):

http://www.scopesnskies.com/prod/finder/universal-finder-mounting-plate/universal.html

But these (and the supplier?) are seemingly *no more* ...

For what it's worth, I never like mounting finders in an unbalanced position -

Unless they're light-weight plastic Red Dot ones. I use tube rings, so tend to

attach an extra dovetail bar on the top and (DIY) screw finder shoes to that.

Makes the whole system a bit more rigid and scope balance is guaranteed.

[baggywrinkle]

/\ Tah! Good idea...more pennies to go on more bits.

I was at fiirst confused with the 96mm barrel dimension. That does not refer to the OTA itself but the reduced end which is part of the focuser assembley.

Telescope Express were very gooding in check that this would fit the 120

Now waiting for a clear patch to try it.

[Moonshane]

I made exactly the same improvement with my 120mm ST. I transforms the function of the scope IMHO.

You can fit a standard dovetail shoe to the little grub screws on the main body of the focuser about half way down. There's a better version that fits a little better with holes in a different place http://www.365astronomy.com/SkyWatcher-Shoe-for-Finderscope-Bracket-with-4-Holes-BLACK-M4-Screws.html

[Macavity]

Ah yes, well spotted! They do look a bit like the Williams Optics 

"mystery hole(s)". (They don't appear on Newt/SCT GSO focusers)

The ones nearer the eyepiece have no obvious other function...

[baggywrinkle]

Was looking at that earlier...I owe you a virtual beer...  LP....

[baggywrinkle]

Ordered...the thingy.

[baggywrinkle]

Finaly got 1st Light...or rather I did not.

I finally moved house just under a week ago, and last night was the first time I tried the new set up.

I found I could not rack out far enough to get focus!

So choices, try and return it or try and get an extension tube.....

[Macavity]

Are you going to get exactly the "right" focus for every circumstance though?

A change of diagonal... a change of eyepiece - even within a series, can do this... 

On the ST102, the original focusser body added an extra 1cm over the Monorail...

the drawtube is 60mm not 50mm. The original has an "integral extension" of 30mm. 

Personally, I was happy to buy a 35mm 2" extension tube and have done with it.

http://www.teleskop-express.de/shop/product_info.php/info/p162_TS-2--Extension-tube---35mm-Length.html

My initial (shared) concern was mollified with a brief tour of the internet... Checkout

the bizarre extension configurations other refractorists use to achieve focus?   

Personally, I find a BIT of added in-focus USEFUL - for filter slides / wheels, imaging etc.

The Monorail easily supports these. I convince myself this was part of my great plan! 

[Moonshane]

Me too.

[baggywrinkle]

Thanks...will give it a go.

[Moonshane]

I find with some eyepieces and a 2" diagonal I don't need an extension but it's always good to have options.

[Solar_observer]

Can someone reconfirm the link to buy this ts focuser for my startravel 120mm? Is this better than the sw Crayford focuser?

Thanks

[Solar_observer]

Oh do i need any extension tubes etc cos of not enough travel or is it ok as it is?

[damnut]

Ditto as above. for above two posts!!

[Solar_observer]

Just placed an order for the ts focuser and 35mm extension tube. Dont know how long it will take from germany but ive got cloudy skies for a week.

[Thalestris24]

Just a thought - maybe worth considering a SW autofocuser for the ST120. It made focusing my ST80 a lot easier and better for imaging It does a good job of holding focus too.

Louise