Review on YUANJS Telescope Interface Astronomical Accessory by Ryan Hampton

I chose this item along with the SVBONY T2-1.25" adapter and 17.5mm eyepiece to convert a 600mm camera telephoto lens into a "telescope". .The eyepiece on my T-Lens with adapter is fine although the image is upside down.(No problem seeing the starry sky save your sore throat.) Using a 45 degree prism set the eyepiece/lens focuses however, no further than 20 feet, far from infinity. Problem: The 45 degree adapter increases the extra crop distance between the lens and the eyepiece. I can't achieve long-distance focusing even if I remove the T2-1.25" adapter and hold the prism just behind the back of the lens. This is defined as the "focus" distance, and some manufacturers warn that their prisms will add an extra 5/8 inch to your telescope's focal length (or camera lens in my case). I expected this to be a problem, but this particular prism seems to add SIGNIFICANTLY more than 5/8ths of an inch. The point is that your instrument must have sufficient inward focus travel to allow the eyepiece to get close enough to the objective lens to focus at infinity. However, the product description does not mention this and in fact this 45 prism may not be suitable. for some reflecting telescopes for this reason. Beware. It's cheap enough so there isn't much financial loss for me because it's useless in my adaptation.