Picked this up a few weeks ago - as I wrote elsewhere the mechanics are wonderful but the optics were not. I replaced the cemented f/5 objective by an air-space 60/360mm f/6 from AliExpress. Initial tests are very good. At this f/ratio there is almost no color, even on branches against the sky. This is focused at infinity. I had a 60/300mm in my stuff that was too short. Here, there is one 1" spacer and the Borg shorty Vixen adapter. I can use a porro prism straight through or a right-angle roof prism as well, or a standard diagonal. But this is destined for sweeping with my 32mm and 40mm Plossls for 11x 6mm exit pupil or 9x 7mm exit pupil. So this becomes a fine spotter as well as astronomically ready and takes all my 1.25" accessories. A little later I will finally get to try my new Herschel wedge!
The lens came with a well-made thin metal spacer. Hard to believe they can sell these good achromats for $30. It arrived very well wrapped and spotlessly clean. The coatings are standard MgF2 on both elements. There is also a green coating option but I wanted the original look.
I will probably buy a 60/400mm next for one of my cut-down click-zoomers which is my main super finder. It's very fun to install a brand new objective
-drl
Well the adventure continues! Today I did some serious testing of the new objective and the issues with focusing with various accessories given the short travel of the helical focuser.
The 60/360mm objective is alas a fail. It has much more color than it should, and pretty serious spherical aberration. That explains why they are cheap. They are probably seconds from a batch that QC flagged.
Well I had a nagging feeling about the original cemented objective. It's Pentax after all. Maybe I should re-evaluate it. I have a short fuse for cemented objectives. I didn't really test it much. I saw some mush and color and said "that's gotta go".
I cleaned it up and put it back in place. To my amazement, it's fantastic! It must have been in backward. For f/5 there is very little color and a Baader filter knocks that out. But this scope can do 30x per inch of aperture with a crisp image - very very good spherical correction. That's as high as I can get with a 4mm eyepiece. There isn't enough focus travel to use even a short Barlow.
I apologize to Pentax for doubting them!
Having returned to f/5, I lose the ability to use my 1.25" porro prism or 45 degree erecting prism. But with the shorty Vixen adapter, I can use my 90 degree roof prism for a RACI view. Standard diagonals are fine as well. So, no great loss. I'll have to try the screw-in porro that came with my Sears 3".
This is a fine little scope and should be considered if it crosses your radar! Pentax put some effort in here. I'm still sort of in shock about how good the cemented objective is.
-drl