I have recently bought a 6" 1200mm f/8 refractor. I know that it is relatively slow for NV use, but it was £70.
I'm looking to adapt it for my P8079HP, prime focus. The tube is a Gen 1 cascade that has decent performance, but is massive.
I have taken off the focuser of the refractor and saw that there's a baffle around 13 cm into the tube.
If I remove the focuser, make a custom one with the NV tube, and put a cheap 200mm FL doublet right up against the baffle (Or remove the baffle and put it a bit further in), I believe that I would be able to reduce the focal length (Thus increasing the speed) and decrease the bulkiness of the NV tube by telescoping it into the telescope tube (Wow say that 5 times fast). Something like the diagram below?
Here is a ray optics simulation (That assumes everything is a thin lens), IDK anything about the maths but it may help illustrate what I wish to do. I found a equation online (That also assumes everything is a thin lens) that the effective focal length is 1/f=1/f1+1/f2-d/f1(f2), which gives me the effective focal length of 685mm, or an F stop of 4.5.
Will this approach also cause significant vingetting or abberations? I am using a narrowband Ha filter so CA is not an issue, and the sensor is a 25mm diameter circle with around a 17-18 diameter usable area approx.
Edited by CLJLF, 20 December 2024 - 04:53 PM.