As specified in the technical data the inner diameter is 47,5mm. There is no thread inside, the thread is just like a baffle against straylight.. There is no need to attach filters in this place because its part of the UFC system and the fitlers are placed in UFC filter holders
Answer by: Baader Web Team (Admin) on Feb 13, 2019 3:39:00 PM
Please click on one of the filter sizes and scroll down to "technical specifications". When you click on that, you will find the size and thickness of the filter. The bandwith is shown in a graphic on the top left of the page, in the image gallery
Answer by: Baader Web Team (Admin) on Feb 14, 2019 8:50:00 AM
Our company exists now for more than 50 years. In this time, more than 15.000 Baader Planetariums (the first patented product of our company) help all over the world to give students an understanding of astronomical correlations. In our own manufactory, more than 500 observatory domes have been produced and delivered turnkey-ready. Instruments and telescope accessories from "Baader" are known for their high qualities by many astronomers and universities. We consider it our duty and obligation, not only to sell telescopes, but an indivdually selected telescope system, that brings you a lifetime of joy.