Tele Vue Nagler 12mm

[Sarge (Rod)]

I have just purchased a TV Nagler 4 12mm. A wonderful eyepiece. Got first light tonight before I was clouded out here in Melbourne. I am very impressed with the wide field, the beautiful detail and the awesome "wow" factor that this eyepice has. Expensive but really worth it.

All said, I do have a small problem. The eyepiece when fitted fully into the focuser, will not focus. I have to fix it about 1-2 cm out of the focuser to get proper focus. I am using a SW 12" flex dob with a crayford focuser. Any suggestions?

Rod.

[wavelandscott (Scott)]

A couple thoughts:
* Check to make sure your scope is fully extended and locked.
*You might try raising or lowering your mirror via the collimation screws. That is are you collimated near the top of the screws or near the bottom?

Cheers,

[Sarge (Rod)]

Thanks Scott, I'll check it out.

Rod

[astro744]

Originally Posted by Sarge

I have to fix it about 1-2 cm out of the focuser to get proper focus.

I would think this is in 2" mode, correct? Try inserting in 1.25" mode.

Or get either the Tele Vue EBX-2120 barrel extension or a 2" parfocal ring and lock it at the appropriate position on the 2" barrel portion of the eyepiece. Either will work well. If you go with the EBX a spare 2" cap will be handy as the 1.25" is difficult to remove with the EBX in position. The EBX-2120 is threaded for 2" filters.

[jakob]

I had the same problem with the LB16.
I mounted the focuser with 3 mm shims.

The 12 mm Nagler is my 2nd most used EP after the 26 mm that came with tho LB16.

Regards J.

[Sarge (Rod)]

Thanks for all the advice. Astro you are correct, the problem is only in the 2" mode. Scott I think I'll leave the secondary alone, as it is only a problem with this eyepiece no others. I have sort of solved the problem temporarily (or maybe permanently) using a thick and very tight rubber band on the barrel of the eyepiece, it now sits out of the focuser about 1 cm and focuses beautifully. Using your idea Jakob I'm thinking of buying a parfocal ring and attach that if the rubber band idea is not sustainable.
Now a happy chappy,

Rod

[Andy Walters (Andy)]

Hi, I have 10"flex dob and use 2" 35mm GSO focal extension tube, $29 from Andrews.
Andy.

[wavelandscott (Scott)]

Necessity is the mother of invention, glad it is working so you can now enjoy.