Newtonian Focuser Upgrade / Advice

[DannyH]

I would really appreciate some advice regarding the Skywatcher crayford focuser on the 250px.

In my last few sessions I started to notice I was slowly racking backward and forward to find focus. The higher the mag the more difficult it is to get razor sharp focus, annoyingly so. The sharp focus point is there, just takes a little toing and froing to get there. I think I just found the stock crayford is not the greatest engineering.

I don't plan on imaging/heavy loads, but I do have binoviewers which would benefit from a low profile focuser, so maybe I need to bite the bullet and upgrade.

I suppose my question is do I try to improve the focuser I have or upgrade to the skywatcher low profile dual speed, Moonlite CR1 or god forbid the CR2? I chose these options mainly because there woould be no drilling required.

I know the CR2 will be superior in everyway, but is it really worth it over the outlay of £150 for the Skywatcher version.

Thanks for any help!

[Moonshane]

It sounds normal to me. The seeing will come and go and you are best finding the point of best focus a leaving it alone. If your focuser is slipping then a simple adjustment may sort it out.

I would save your money for now.

[Dr_Ju_ju]

Have a look at this video https://www.youtube.com/watch?v=ofOSAMlqZWw  it may give you some ideas to improve things ?

 

 

Julian

[laser_jock99]

I too have found the SkyWatcher focusers a bit 'ropey' at times.

It's one reason I'd recomend some of the GSO Newtonians- the F4 imaging scopes come with a nice monorail focuser which in comarison seems smooth and above all more stable.

[niallk]

I found this worked simply wonderfully, transforming my stock focusser on the 250px. A joy to use now at high mag.

Best of luck,

Niall.

http://www.teleskop-express.de/shop/product_info.php/info/p2625_1-10-micro-transmission-for-retrofitment-of-Crayford-focusers.html

[DannyH]

Thanks all for the good advice.

The stock one just doesn't seem fine enough to me, a bit of DIY to smooth things out & the microfocus upgrade looks like the solution for me, this also means one less shiny thing to hide from the wife. 

[Moonshane]

There's a few vids online about grinding the flat face of the drawtube flat with a wetstone

[niallk]

...and just to say, what you describe re focus was similar to what I experienced too before upgrade: post upgrade find it so much better to find the optimised point around which seeing varies.

I also have seen some interesting approaches people have with oversize wheels (eg jam jar lids etc) to get the lightness of torque for adjusting. Also, the instructions on the TS site there give some diagrams which might be useful even for tweaking the Teflon pad force on the shaft.

I notice some concavity in my drawtube flat going by the wear marks, but judge it ok/or even preferable because I seem to be getting even contact pressure. Two points define a straight line, and force applied in between. Bar is straight and not bent. I've had no slip issues with a binoviewer in place or filter wheel/powermate/7T6 ep, and I don't use the 'lock nut'.

Luckily, I now find the focusser to perform very well for me - despite what many others say about it being of poor quality.

Best of luck!

[Gasmac]

+1 for the whetstone. Also a bit of screw tightening on the under side can reduce the slop and the tendency for the focus to shift. I decided in the end to splurge and get a cr2 which has made me a very happy boy. I plan to swap it onto my next scope in the far flung future.

Sent from my iPhone using Tapatalk

[DannyH]

Thanks for the advice, I ordered an oilstone from screwfix (think that's the same as a whetstone) and will give that & the screw tightening a shot first before adding a fine focuser, I've seen the Lacerta upgrade kit on 365 astronomy for £60, which looks good.

The focuser quality seems ok, just the set-up/finish is a bit sloppy.