Focuser drawtube extension

[AlistairW]

Hello,

I have noticed that when I achieve prime focus on my refractor I am very very near the limit of its extension. It does work but, but it this anything to worry about, or should I get a focus extender? The thing with extenders, I believe, use compression rings, and I am not a fan, hence why I use a Hotech SCA (Self Centring Assembly) that does not use compression rings.

Thanks

[Ruud]

I use an extension tube to turn my telescope into a long distance microscope. All it does is move the eyepiece back. It's just an empty 2" tube and it has a set screw.

There are many models, some with compression and others without. Mine is among the ones here: Google image search

You don't want too long a tube, because you still want to reach focus at infinity. Maybe you need something the size of a shorty Barlow (with the lens removed).

 

[ronin]

Prime focus usually refers to attachment of a DSLR and that in general means inward travel whereas you are describing outward travel it appears.

I see you have a GT81 - is that the scope in question?.

Have you got the diagonal in place? If not that is likely the reason as the diagonal will be acting as a diagonal and an extension tube. The diagonal will effectively push cameras and eyepiece outwards. If not there then yopu have to extend the focuser far enough if that is possible. WO's seem not to have a great deal of travel on their focusers.

One scope I bought is actually defaulted to imaging, so to use an eyepiece and view, you have to add in one of the supplied extension tubes. First time out you are stood there wondering why the thing cannot produce a view. Eventually realisation dawns.

[AlistairW]

Think I might have used the wrong term with prime focus ....

As it does work and I can get focused, am I really worrying about nothing. As I image my CCD Inspector software says I am suffering from very little tilt - I am thinking if it's not broke why try and fix it. Just doesn't look too good, but I guess the focuser (Moonlite) should be expected to handle it.