Changing the focuser set up..

[Bluenosebatty]

When changing the full set up of a focuser on a 250px is it a hard task?

I want to change my focuser as its the naffest pile of poop there is, is there any style or type or manufacturer in paticular i should be looking for? Is there anythin i should watch out for when buying it in terms of will it for is it worth the money? As you can tell im a beginner. I have about £150 tops to play with and i want to change the hole rack, wheels and everything. I was collimating my scope before as i has nothin better to do and realised theres a lot of movement in the track/tube part of the focuser. Is that normal? I cant see any way of tightening this up either.

Thanks in advance for any help

Mark.

[JamesF]

You can adjust it to a certain extent. There's a tensioning adjuster under the focuser that allows you to change the tension on the tube. It's a grub screw in the centre of the cover plate for focusing mechanism, just in front of the lock screw. It might well be worth tweaking that.

There's also a mod you can do to the focus tube itself. For some reason the flats on the Skywatcher crayford focus tubes that the spindle runs against are not actually flat. They're actually slightly concave, so the spindle only runs on the edges. Mine shows clear wear on the edges and none on the rest. Apparently they are much improved if you remove the focus tube and flatten the surface with an oilstone or something similar.

James

[NGC 1502]

Hi Mark. Lots of people do change their focuser, it's not that hard a job.

But are you sure that you cannot make the present one acceptable ?

If there is slack in the drawtube, there are ways of dealing with that. If you could post a pic, someone could perhaps let you know where any adjustment screws are.

On the basic SW focusers there are 2 tiny grub screws either side of the much larger locking knob. The tiny grub screws are not easy to see. You would need a tiny allen key to make adjustments on a trial and error basis. But there are lots of different focusers out there, so this may not apply to yours. A bit of investigation and DIY may be all you need.

If there is a great deal of slack, some have successfully used teflon tape on the drawtube to sort it.

Regards, Ed.

Regards, Ed.

[steppenwolf]

I replaced my 250PX focuser with one of these from Baader - a little more than your budget but worth every penny, it has transformed the mount.

I wrote up the details of the upgrade in the Sky at Night Magazine earlier this year -but it was relatively simple to do although I did have to drill four new mounting holes in the optical tube.

[JamesF]

And to answer your questions

No, it's not "normal", or doesn't have to be. Mine has very little play.

It's not a pain to replace the entire focuser mechanism. It's only held on with four screws. There aren't many replacement options below the £150 mark though. The Baader Steeltrak is about £200. There is the Skywatcher low-profile crayford as fitted to the MN190 (I think), but you may find that won't reach focus without an extension. The only other one that immediately springs to mind is the Revelation. I have no idea what that is like.

I'd try adjusting it and sorting out the bearing flat before buying a new focuser, I think.

James

[Lews Therin]

Astronomyshed has done a video showing you how to improve the standard Skywatcher Crayford for free:

He also has a couple of other videos that cover focusing modifications... Hope that helps.

[Bluenosebatty]

Here is a pic of my current set up, cheap n plasticy,

[JamesF]

That's rather different from the one I have which has a white body and pierced silver wheels with a rubber grip around the edges. Is it rack and pinion?

James

[Bluenosebatty]

I hadnt noticed the grub screws tbh il have a play with that later when i get home, thanks guys

[Bluenosebatty]

Its the same as this one here....

http://www.opticalvision.co.uk/astronomical_accessories/Focusers/1.25-2_rack_and__pinion_focuser

I bought the scope SH so im guessing at some point it was replaced for some reason.

[JamesF]

Ah, it may be that yours is old enough for that one to be the standard fitment. There is some improvement that can be made to the older style SW R&P focusers, but I'd understand if you weren't happy with it even then. The Revelation crayford focuser would surely have to be an improvement over what you have and be in budget, but as has already been mentioned it may mean drilling new mounting holes in the OTA if yours don't match up. I can't recommend that model from personal experience though as I've never used it.

James

[Bluenosebatty]

Can you see why it has to be changed lol!! Would a low profile focuser be a good swap?

There is these 2 on FLO that no doubt be a big improvement??

http://www.firstlightoptics.com/skywatcher-focusers.html

[JamesF]

I have the second one on my 250 flextube. It does require an extension to reach focus with 1.25" eyepieces. I've not really had the use out of it to really comment on performance though. I've managed about three hours observing since I fitted it and most of that has been getting used to the scope.

James

[Bluenosebatty]

Just tightned up that little grub screw and its worked a treat, no more wobble!! I may have to check if my scope needs collimating again a little later. Still want to replace it though i think.

[JamesF]

Well that's good news.

James

[Bluenosebatty]

Thanks for everyones help by the way!! As always its very much appriciated!!

Mark.

[NGC 1502]

Can you see why it has to be changed lol!! Would a low profile focuser be a good swap?

There is these 2 on FLO that no doubt be a big improvement??

http://www.firstligh...r-focusers.html

These basic R & P focusers can be made to work well with some DIY. There are two tiny grub screws either side of the much larger lock screw. They bear onto a plastic strip. If the plastic strip is replaced with teflon and the adjusters tweaked, the result is a very usable focuser.

For visual observing, they can work just fine.

Regards, Ed.

[Bluenosebatty]

Ive just got in from a hour of observing god damn clouds come over, whilst out it started to wobble again! Il strip it down tomorrow and have a look at it,....i need new Eps too as the ones i have are terrible. Il give flo a call once i get the funds together.

Thanks Ed.

Mark.

[NGC 1502]

Ive just got in from a hour of observing god damn clouds come over, whilst out it started to wobble again! Il strip it down tomorrow and have a look at it,....i need new Eps too as the ones i have are terrible. Il give flo a call once i get the funds together.

Thanks Ed.

Mark.

Hi Mark, obviously its up to you what action you take to sort this. However, if you want, PM me your address and I'll send you some Teflon tape to use on the plastic strip that those two grub screws push against. The tape goes on the plastic strip where it rubs on the focuser draw tube. Nothing to lose to try this.

Regards, Ed.