Tele Vue NPR-2073 0.8x Reducer for NP Telescopes

Tele Vue NPR-2073 0.8x Reducer for NP Telescopes

Model NPR-2073 0.8x Reducer for NP Scopes is specifically designed to be used with the Tele Vue NP127is and NP101is Imaging System telescopes. This reducer was designed to minimize vignetting with camera sensors up to 43mm diagonal (Full Frame) and is a replacement for the previous 0.8x reducer, the discontinued NPR-1073 (which worked best up to APS-C sensors). When combined with a Tele Vue Petzval type telescope, NPR-2073 reduces the focal length of the telescope by 20% and makes it that much faster. This increases the telescope´s field of view by 25%.

This reducer is threaded on both sides for the Tele Vue Imaging System. It attaches to the Imaging Insert included with the Tele Vue NP127is and NP101is scopes and the other side accepts all the spacers, camera adapters, and thread converters included in the Tele Vue Imaging System. Back Focal Length spacing for the reducer is included in the instructions.

The NPR-2073 can also be used to enlarge the field of other Tele Vue Petzval type telescopes, but will not provide additional correction for those models. For use on Tele Vue Petzval model telescopes with 2-inch focusers, use Tele Vue Imaging System Nosepiece for 2" Focuser (RAD-1074). The RAD-1074 slides into a 2" telescope drawtube and has a 2.4" Imaging System thread on the other side to accept any Imaging System accessory.

Connecting the reducer

Objective Side
For Imaging System scopes, install an I.S. Imaging Adapter to the front of the reducer. If you find that the drawtube extends more than 1.5 inches in order to reach focus, install spacers between the reducer and I.S. adapter. For use on other Tele Vue Petzval model telescopes with 2-inch focusers, use the RAD-1074 Adapter instead of the I.S. Imaging Adapter. Note that when used with 2” focusers there will be increased vignetting for full frame sensors because of the inner diameter of the 2-inch barrel.

Camera Side
The reducer has a nominal Back Focal Length (BFL) of 68 mm, measured from the reducer rear shoulder as shown in figure 1 (image 4). This BFL will work best for most color imaging applications such as OSC and DSLR full-frame and crop sensors, and in monochrome with either LRGB or HST palette filters (but only with crop sensors). Imaging with DSLRs is only possible with this BFL because 68 mm is large enough to support the 55 mm needed for DSLRs. For DSLR use, install a ¼ inch I.S. spacer (TLA-0250) and then a camera adapter such as the CWT-2070 or NWT-2073.

In the special case of imaging in full-frame monochrome with either LRGB or HST palette filters, a BFL of 50 mm should be used, as shown in figure 2 (image 5). This BFL includes a +1 mm focus shift required for a single 3 mm filter. In this configuration, star images in isolated wavelengths focus sharper at the very edges of the field than they would have in color cameras.