Hi everyone. I purchased this at a local flea market, thinking it was T-mount. My intent, was some nice distant and close ups, using my 30D and T-mount adapter. I believe theres a eyepiece, and or extension tube missing. The lens is marked-CrystalVue Optics, Lx8 DIGITAL. It also says CrystalVue SuperWide Digital 40. May i assume this is an 8X (power) ,wide angle (40 degree) scope ? The thread is indeed T-mount. The large front rubber ring, will focus the lens. Looking thru the lens, with the naked eye, you can almost obtain sharp focus on distant objects. Putting the T-mount on the rear, nothing is sharp. Removing the rear element piece, the lens with T-mount will focus cpose up (inverted image). If i place two Canon extension tubes on the full lens, it still wont quite focus at inf. , and it gives error 99. Taping pins would clear up that i believe. What do i need, or what is missing, to use the lens at inf. focus? Any ideas or comments, will be welcomed.

Scope with rear optic removed, T-mount adapter attached.

HELLO DOLLY - Canon 30D, 1600 ISO, JPEG, from camera.

To begin with:

The "rear optic" is an effective eyepiece as it corrects the image and allows you to see an image thru the scope.

The scope has focusing, so it is more than a refracting telescope.

The 40 probably refers to the objective size in mm diameter. The 8X probably is the power WITH the rear optic.

My guess is this scope is to be used with a small digital camera (p&s) (thus the "digital") where an adapter screws or pushes onto the camera lens and has a T-thread on the end to screw into the "rear objective". This is called eyepiece projection setup. The camera focuses on the focal point of the eyepiece.

Additionally, the T-thread could be mated with a T-thread adapter for your EOS and it will give an upside down image. The question is can you adjust the optical path to get infinity focus? If it focuses on close up targets, you need to shorten the optical path for infinity targets.

I use a Takahashi 60mm APO refractor with great results.

Hi Jim.
Thanks for the reply. That is my EOS T-mount screwed on to the lens in phicture # 2. That allowed me to take the doll close up. With that rear eye piece ? installed-you need to lengthen, not shorten the optical path, to reach out towards inf. focus. Thats why i said my two extension tubes (37MM total) did reach out to a longer distance. There is a loose adapter ring, with the package. Its larger than T-mount thread. It appears to be a 52MM to 55MM step up adapter ring. The large female end , measures 55MM, and the rear male ring, measures 52MM. The was in the box, who knows, for what reason.
Cheers
Harry