C102F can't come to focus

OK, so I just went and picked up a super mint Celestron C102F. This is the scope I drooled over as a kid but couldn't afford. Now at age 35 my dream finally comes true...but I can't come to focus with any eyepiece I tried tonight.

Nagler 16
Radian 12
Tak 3.6

It seems that there's not enough infocus. The tube apparently is too long. Any other Celestron/Vixen/Orion 102 Fluorite users out there with the same problem? If so, any idea how to remedy his issue?

Thanks in advance.

-Evan

p.s. As soon as I get this scope up and running, I'm going to do a side-by-side with the vaunted Takahashi FS102nsv

I think these were designed for a 1.25" diagonal.
After-market 2" adapters were available, but I
suppose there could be back-focus issues if used
with a 2" diagonal. An easy solution would be to
change-out the focuser with one of the 2" Moonlight
models.

mmmm... that's a weird one. I used to have the Vixen/Orion version and it worked fine with all my eyepieces (I think it had a 1¼" visual back). You can put the tube on a mount, remove the focuser (3 screws), hold the diagonal with the eyepiece in it in your hand and try to reach focus that way, just to make sure nothing is wrong with the lens. Maybe the previous owner took it apart to clean and put the lens/s back in backwards...

oren.

Hacksaw time! 8O

Philip

I have seen several C102F's with the 2" Lumicon diagonals that appear to come to focus. Not sure if their tubes had been shortened.

If the moonlite focuser is shorter or of a lower profile than the stock focuser, it might just fix your problem.

I use a 1.25 diagonal on mine and have no problems. I also don't have any 2" eyepieces.

Good luck
C

Hi Evan,

I have a C102F as well. Mine is the 900mm focal length version and arrived with a 2" focuser but I found I could not reach focus with a 2" diagonal and 2" eyepieces. The scope works perfectly with a 1.25" diagonal and any 1.25" eyepiece I have tried and straight through with any 2" eyepiece. The optics on my scope are stunning. I ran across this on Excelsis:

"This was one of the first fluorites sold. The mechanical
finish is so-so, but the optical quality is outstanding.
They were sold on Super Polaris mounts, which were inadequate.
The color correction outside visible appears fair (i.e.
trouble with an unfiltered CCD), but visually it knows
"no limit" to magnification and has exceptional contrast.
The tube is long, but light.

I sawed the tube down by 1/2" to reach focus with a 2" star
diagonal with a 15" TV widefield. I have never, ever seen
false color on any object with this scope. It beat a very
early Tak 100 side by side. In the 1988(?) pass of 23 Sag (??)
through Saturn's rings, it just blew away the view in a C11
right next to it. I owned a 6"f/9 AP StarFire, and in crappy
seeing (as I almost always have), the C102F was almost always
the preferred instrument.

I love this scope.

15 years later, you can still find them. They are 900mm focal
length (different than the new Vixen fluorites), and should
run about $1400. Mount yours on something worthy."

Interesting thread, as I am the one who sold Evan the C102F.

I was able to reach focus just fine with all my eyepieces using a 2" diagonal with this very scope. That being said, I used it with a Lumicon 2" enhanced diagonal - not sure if that makes a difference or not.

Also, contrary to what has been suggested earlier in this thread, the scope has never been disassembled or modified in any way. Evan, feel free to give me a call if you experience problems or would like to return the scope- I miss it already!

Evan,

Since the beginning of this thread, I've been looking all over the house looking for my original C102 Ffocuser and Lumicon 2" visual back. I can't find it - too much stuff!

I wanted to measure the difference in length between the old focuser + visual back with the the Moonlite CF1-V focuser with the 4.5" compression ring draw tube racked all the way in so that I could let you know how much shorter the Moonlite focuser is. My Moonlite CF1-V has the motor focus option, but the motor is on the side of the focuser and doesn't add any length. I suspect that the Moonlite CF2-V with the fine adjustment knob is the same length as the CF1-V.

The 2" Lumicon visual back added 1" of additional length to the length of the orinal C102F focuser + 1.25" visual back and out of necessity was very thin walled especially at the threads that screw into the original focuser draw tube.

I just measured the length of the Moonlite CF1-V on my C102F and that measures 92.5mm from the back end of the telescope tube which is significantly shorter than the original C102F focuser + Lumicon 2" visual back.

I did not put a hack saw to the tube - it is still the original lenth.

The only 2" eyepiece I have is a University Optics 32mm MK-80 and I also have an Astro-Tech 2" Dielectric Quartz Diagonal. So far I have not yet used this at night: I have only tested this setup in daylight aimed a tree near the horizon and it came to focus with no problems.

Jim