12inch focus problems

[alan meehan (Alan)]

Hi guys i have been restoring a orion 12.5 inch dob and have put a new crayford focuser on it but i cannot bring it into focus i need more inward travel
if i was too bring the primary mirror up towards the secondary would that enable me more inward focus iam not sure i dont want to cut it off and it wont work nor do i want to replace a new focuser i just brought its a sonotube type
any answers would be helpfull
thanks

[glend (Glen)]

Alan , how much inward travel do you think you need? There are inward travel adaptors that fit into 2" focuser draw tubes, they are recessed so that EPs sit inside them. I have one made by Televue, sold by Bintel. They don't provide alot of range, maybe 1cm.
Another thing to look at is the mirror cell and its attachment, longer springs and bolts can be used to move the focuser up in the tube; you should not have to cut the tube.
Also there are a number of very low profile focusers on the market, designed for this type of problem.
Have a look here at one example:

https://www.firstlightoptics.com/sky...d-focuser.html

And another here:

https://agenaastro.com/antares-low-p...ual-speed.html

TS has them as well.

[Rainmaker (Matt)]

Originally Posted by glend

Alan , how much inward travel do you think you need? There are inward travel adaptors that fit into 2" focuser draw tubes, they are recessed so that EPs sit inside them. I have one made by Televue, sold by Bintel. They don't provide alot of range, maybe 1cm.
Another thing to look at is the mirror cell and its attachment, longer springs and bolts can be used to move the mirror up in the tube; you should not have to cut the tube.
Also there are a number of very low profile focusers on the market, designed for this type of problem.
Have a look here at one example:

https://www.firstlightoptics.com/sky...d-focuser.html

And another here:

https://agenaastro.com/antares-low-p...ual-speed.html

TS has them as well.

fixed that for you Glen

[alan meehan (Alan)]

Thanks guys i like the idea of the televue inwards eyepiece adapter this might do the trick or maybe extend the length of the springs on the primary
as well thankyou i will try this out