GSO 8" Dob focus travel

[MortonH]

I discovered last night that my TeleVue eyepieces don't quite reach focus. There's not quite enough out travel. My Pentax and Meade eps were fine (both wide angle). Using the Meade/Pentax with my 2.5x Powermate had the same problem.

I guess the solution is to buy one of Bintel's 35mm extension tubes, which will have the added advantage of allowing me to attach a filter and then change eyepieces without removing the filter each time.

Anyone else had this issue?


Morton

[janoskiss (Steve H)]

That is normal. My 8" GSO is the same. Most TV EPs need to be pulled a few mm out of the focuser barrel (of GSO crayford). I also have the 35mm extension tube - but with one of those there is not enough in-travel. But you can play around with the primary mirror position to get there one way or another.

[MortonH]

Or somehow you need to 'build up' the 2"-1.25' adapter by a few millimetres, but how would you make sure it was level? Maybe someone could fashion a flat ring that could either be attached to the top of the adapter, or else fitted between the eyepiece and the focuser. Doesn't sound too hard, does it?

Morton

[GeoffW1 (Geoff)]

Originally Posted by MortonH

I discovered last night that my TeleVue eyepieces don't quite reach focus. There's not quite enough out travel. My Pentax and Meade eps were fine (both wide angle). Using the Meade/Pentax with my 2.5x Powermate had the same problem.

I guess the solution is to buy one of Bintel's 35mm extension tubes, which will have the added advantage of allowing me to attach a filter and then change eyepieces without removing the filter each time.

Anyone else had this issue?


Morton

Hi,

Yes, this was also a problem with a pre-loved Bintel 8" Dob I got. There were no Televue or Pentax eyepieces came with it either *sniffle*.

So I got a Bintel 35mm extension tube, and no problem since, except still no
Televue or Pentax eyepieces *snuffle*.

GeoffW1

[MortonH]

I spent an hour hunting round the flat for elastic bands to wrap round the bottom of each eyepiece so they'd be at the right height, then realised that this would mean that they wouldn't be sitting in the right place in my Powermate. So now I just have to pull them out a little bit and they're fine. Not worth spending $35 on an adapter.

Morton