Jump to content


Extending ES 9mm 100* EP


Recommended Posts

Hello all

i have recently found I need to extend to focus my new ES 9mm 100*. Bit of a pain really. My DSO sessions usually consist of generally using the 20mm and switching to the 9mm. One needs extension, one doesn't. 

My question is, rather than putting in an extension tube every time, could I permanently add something like the Baader extension ring to the EP on its filter thread. I've thought of par focalising rings but just don't like the idea of the EP only partially going into the focuser. 

Any suggestions please? Thanks


Link to comment
Share on other sites

The 17 Nagler T4 is the only TV eyepiece parfocal with other lens lines where the field stop is at the shoulder.  Most TV eyepieces place it 1/4" below the shoulder (about 6mm) requiring some lifting of the eyepiece out of the holder to make it parfocal.  The 12mm Nagler T4 puts it a ridiculous 0.78" (20mm) below the shoulder necessitating a barrel extension and parfocalization ring to parfocalize.  All of the 1.25" Pentax XLs and XWs and Astro-Tech AF70s seem to focus at the shoulder as do the original 30mm ES-82 and 40mm Meade 5000 SWA eyepieces.  If you have a zero or near zero height 2" to 1 1/4" adapter, they all play well together in the focuser.  My 10mm Delos is noticeably different from the non-TV eyepieces.  Not enough to warrant parfocalization like the 12mm T4, but noticeable.  I don't have any 100 degree eyepieces because none of them have near enough eye relief for my deep-set, astigmatic eyes, so I can't comment on their focus locations.

  • Like 1
Link to comment
Share on other sites


I have a few scopes as you probably know and the 6 Ethos'ssss I have focus all over the place but all at least do work in the focusers. Only the M/N 190mm needs an extention and that is for all eyepieces pretty much, it has a focuser a bit like a trombone, slides in and out and lock, bit of a pain actually.

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.