[ATM] 8x barlow for 126mm F/5 Houghton telescope

["Ukyo Chen" <ukyochen888@hotmail.com>]

Hi all,
I wish my 126mm F/5 Houghton telescope can also be used for planet observing 
in the future, so I desided to design a barlow for it. The result is still 
pretty good while I extend the focal length to 5000mm (F/40), That is 8x of 
F/5 system! Also if I change the thickness between the mirror and the 
barlow, the barlow can reduce to 5x and still get pretty good image. That 
means I can both use for 5x and 8x with the same customized barlow. China 
optical company should able to make the barlow for me, it use 3 BK7 sphere 
lenses like a wynne corrector but get much longer back focal length, 210mm 
in 8x and 110mm in 5x, you can connect other devices(like diagonal mirrors 
for binoscopes) easily. So the barlow will have lenses part and 2 tubes, if 
only 1 tube installed, it works @5x, if both, then it is a 8x barlow. The 
barlow also works fine for any F/5 parabolic mirrors.

And one bad news, since my AL tube is only 129 diameter, I asked the lens 
maker to reduce lens size from 127mm to 126mm. Unfortunately the lens 
surface corrupted during the modification, they had to rework on it and 
re-coating.

Best Regards,
Ukyo Chen


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