Astromania adjustable tube rings for astrophotography.Set of 2 guide scope rings for guide scopes between 70 mm and 120 mm tube diameter. The guide scope rings from Astromania Optics allow a reliable and above all stable adaption of telescopes parallel to the main instrument. Most common use is astrophotography. With the knurled thumb screws, the guide scope is adjustable and you can centre a sufficiently bright star in the eyepiece or the the autoguider. And the tube rings are suitable for bigger finder scopes, too. The adaption of the tube rings to the telescope. The rings have two female M6 threads in a distance of 38 mm. Therefore, the rings fit directly to the TSFDA or TSPKM dovetail clamps. You can also attach the rings to flat support surfaces like dovetail bars, and get a short adaption to your telescope. Technical Details: Inner diameter: 127 mm Outer diameter: 145 mm Support surface: Flat area with 45 mm diameter and 4x M6 threads (female) Distance of threads: Inner pair 20 mm - outer pair 38 mm