Tele Vue NPR-2073 0.8x Reducer for NP Telescopes User Manual
- June 10, 2024
- Tele Vue
Table of Contents
NPR-2073 0.8x Reducer for NP Telescopes
User Manual
(NPR-2073) 0.8x Reducer for NP
Telescopes
Introduction
This 0.8x focal reducer was specifically designed to be used with the NP127is
and NP101is. While it can also be used to enlarge the field of other Tele Vue
Petzval type telescopes, it will not provide additional correction for those
models. 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 NPR-1073, which worked best up to APS-C sensors. When combined
with a Tele Vue Petzval type telescope, it 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%.
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 68mm, measured from the
reducer rear shoulder as shown in figure 1. 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 68mm is
large enough to support the 55mm 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 50mm should
be used, as shown in figure 2. This BFL includes a +1mm focus shift required
for a single 3mm 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.
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V03/01/23
References
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