FS-78 "in-focus" Issue

Hi folks, I have had an FS-78 for about 4 months now. It was purchased new, so presumambly it's the most recent generation in terms of tube length, focuser tube length, etc. Last month, I purchased the 2" adapter for the FS-78. Previously I used the 1.25" visual back and teh 1.25" Takahashi prism diagonal. On Saturday night I used a William Optics 2" mirror diagonal. Everything worked spendidly until...

I discovered that my 4mm University Optics could not come to focus. There was just barelt insufficient "in" travel to achieve focus. All of my other eyepieces, 1.25" and 2", achieved focus no problem.

The 2" adapter also seems to add about 1.5" of extension. I'm guessing that if I placed the 1.25" adapter from the 2" diagonal directly in the 2" adapter, I could have achieved focus in straight through mode. It was that close. Has anyone else experienced anything similar?

Jim,

I have an FS78 with the longer tube length and was worried about the same issue using a WO 2" diagonal. I ordered the "Setscrew" version of the Tak 2" adapter, P/N TOA0040 rather than the "Compression" version, P/N TOA0050, because it was a little shorter thereby increasing the amount of in-focus. All of my eyepieces came to focus except the Pentax SMC 28.

You might try buying a 1.25" adapter with a lower profile than the one supplied with the WO 2" diagonal.

Good luck,
Rick