[AZ-Observing] Re: The Orion 120mm ED Refractor
- From: Roger Ceragioli <rogerc@xxxxxxxxxxxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Tue, 08 Aug 2006 08:36:16 -0700
Such a system will probably have enough variation of spherical
aberration with wavelength that not all of the light from violet to red
will be exactly "in focus." Yet because there is no obvious spectral
imbalance in the nominally unfocused light, you will see no "color
error" arising from it.
This isn't to say that there's anything wrong with these scopes, but
just to point out that there are many, many complications in fact in
matters of "color correction."
The best scope is the one that gets used and gives the user the greatest
satisfaction.
Roger Ceragioli
> It's description below would indicate a double, not triple lens combination.
>
> "Superb apochromatic optics set the 120ED apart. The 900mm focal length
> (f/7.5) is great for planetary work and fast enough for faint galaxies and
> nebulas. FPL-53 extra-low dispersion (ED) glass in one of the two objective
> lens elements and multi-coating on all air-to-glass surfaces means light
> passes to the eyepiece or camera without color fringing. Besides providing
> more light-grasp for deep-sky imaging &emdash 43% more than a 100mm scope
> &emdash the optics easily handle high magnification"
>
> If I remember correctly this was already pointed out. Several of the
> members have the 100mm ED and are very pleased with it. If it is as good as
> that telescope, it might be worth the cost. I however would spend $395.00
> more and get the Stellarvue SV4 Triplet, $395 dollars more would be a better
> purchase in my option, even though it is only 100mm. The Stellavue quality
> is super. I have there 80mm APO triplet and could not be happier with it.
>
> Thomas Hilton
>
>
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