Big Dob won't find focus??

[bond19]

Firstly a very Merry Christmas to you all.

So tonight the skies have cleared and finally after what feels like weeks locked indoors I'm trying for first light with my 12" OOUK dob. Only prboblem is it won't find focus?? It's gutted with a 2" 1/10 speed focusers and seems to have the option to extend. I've tried focussing at minimum and maximum extension and still now luck?? Any suggestion guys and girls??

[Moonshane]

Most oouk newts need a 2" extension to reach focus for visual. If you have one try it and all will be well. If you don't then make sure this is the reason by holding your eyepiece out a bit. If you have a barlow, try unscrewing the lens element and use this as a temporary measure.

[scarp15]

As Shane has said, 2" extension is probably required. I encountered this when I first used my OOUK 14", though I already had a 1.5" extension, just too short and could not focus my low power 2" e.p's. 

[John]

As above. I need a 35mm extension tube on my OO 12" dob to get it to focus.

[bond19]

Thanks, I've now tried holding the ep at the end of the focuser tube fully extended and it does just about reach focus. I guess it a trip to ABS or FLO for the extension tube

Cheers

[John]

Did you buy the scope new from Orion Optics ?. They used to supply extension tubes with their own focusers but I don't know if they still do that now.

[scarp15]

Interesting I was not aware that OOUK used to supply extension tubes for their focusers, as they always seem to need them, though this one is second hand.

I was a bit suprised that this was not pointed out to you (or one was not supplied in the sale) when you purchased the scope Chris, mine came with a plain tube (the barrel of an old 2" barlow) which was just short of 2", so I could at least use some of my eyepieces. I went and bought the 2" William Optics extension tube from FLO and it works a treat. However with this option (there are others) it is only compatible with the High Hat designed 1.25" adapters, as it does not have a slot for the tensioning bolt on standard 1.25" adapters.

[John]

I use one of these:

https://www.altairastro.com/product.php?productid=16444&cat=317&page=1

The scope did come with an OO one but it was rather crude with set screws rather than a compression ring fitting.

[scarp15]

Yes the Altair Astro model looks nice at a good price, yet (similar to mine) looking at the picture I am not so sure that 1.25" adapters requiring a slot for the tension bolt, would sit flush in this.

[John]

..... I am not so sure that 1.25" adapters requiring a slot for the tension bolt, would sit flush in this.

It's not got a cut out for the tension bolt of low profile 1.25" - 2" adapters, you are right. You can get extension tubes that do have that feature though. I also found that a 50mm extension tube worked OK but some of my eyepieces require quite a lot of inwards focuser movement so I find the 35mm better to avoid too much of the focuser drawtube being stuck out into the light path when using those eyepieces (Baader GO's).

[jetstream]

The Baader Clicklock is very handy.

[bond19]

The guy I bought from never mentioned the need for an extension tube, but I'm pleased it's a fairly straight forward fix 

[bond19]

Ordered.. Just hope it arrives soon now the skies are favourable!

https://www.altairastro.com/product.php?productid=16444&cat=317&page=1