Quote:

---

The effect of the prism diagonal. It just shifts the red focus closer to the objective.
Most simple ED doublets are designed in such way: an optimal color correction shifted towards blue-violet in trade-off of the correction in red - according to a night time vision sensitivity shift. With such correction violet is much less pronounced. This gives us a feeling of better color correction. But this is only feeling. Prism diagonal just return color correction to a better optimum. Nothing magical.

Clive, I think you never saw how a Chromacor and SAFIX do their job in image improvement.

---

Valery,

Explains exactly what I have seen with some of the ED
doublets out there. They tend to not handle the red well
so that they can be well corrected in the blue/violet. My
Orion 80ED fell out in the red, and worked better with a
prism diagonal. My 80mm triplet and 127mm triplet are well
corrected in the red, but fall out a bit in the blue/violet.
I tried a prism diagonal in my 80mm triplet, and the color
correction got noticeably worse on a white fencepost with
the prism. Just a bare trace of violet at 160X with a
mirror diagonal, that went to clearly evident blue/violet
with the prism and same eyepiece. No magic, just a shift
back to a standard correction on the ED scopes that seem
so well corrected in the blue/violet. Too many fail to
understand the effect of poorer red correction on the view
of certain double stars (such as Izar) and the planets.
Shifting the color correction does seem to sell scopes
though.

As to the Chromacor, yes, definite, real improvement. I
still remember the experience I had testing you first
prototype on my 120mm and 150mm achromats. The improvement
in planetary detail was immediately evident. The Chromacor
provided a real improvement in color correction, I can
vouch for that from experience.


Tom

Post Extras