In the Internet you can find a whole range of DIY telescopes based on HT tubes. Since this does not satisfy me optically, I decided to build a variant based on PVC pipes. In comparison to the HT pipes there is a large selection of adapters which can be used for building.
Unfortunately there are only a few suppliers of cheap lenses that you can use for your own telescopes. In China there are a lot of suppliers, but the offer is very confusing and you do not know which quality you will get.
In the photo sector the Beroflex f8 500mm telephoto lens is a cheap and good alternative to the lenses of the big manufacturers. Because the Beroflex is similar to a normal telescope I decided to try to build a DIY telescope based on it.
Besides the front lens there is a correction lens inside which I will not use. I suppose that the lens is a kind of Barlow lens because the focal length does not fit to the length of the telescope. Without this additional lens the focal length seems to be about 335mm.