Camera specific bayonet adapter (camera ring) for Nikon DSLR with M48x0.75 mm internal thread for astrophotography. 
By using the large thread M48x0.75 mm, the vignetting of e.g. a DSLR full format sensor is effectively avoided. Compared to the small T2 thread M42x0.75, this adapter has a free inner diameter of 41.2 mm. This camera ring is made of matt black anodised aluminium and weighs only 30 grams. The light path (overall length) is 8.0 mm. 
FEATURES 
Camera-specific bayonet adapter Nikon
Large female thread M48x0.75 mm 
Free inner diameter of 41,2mm 
No vignetting for full format sensors 
Light path (overall length) is 8.0 mm 
Made of matt black anodized aluminium 
Weight only 30 grams