A lot of options here. I'll dig-up a couple of old articles. There's also that JMI 25" (IIRC) that uses a flat secondary and a flat tertiary to put the eyepiece at eye-level when pointing straight-up; the light is reflected stratight back down the tube off the secondary, then out the side off the elliptical tertiary. Being a tall guy, you can work the secondary down in size a bit, putting the focuser a bit higher. It's a good idea to use enhanced coatings on as many optical surfaces as you can afford with a 3-mirror system, and the image will be left-right reversed, but you can't beat the convenience. We should talk more, if interested. C. --- David Dunn <david.dunn@albertsons.com> wrote:
I hadn't thought of the area of the mirror. I just ran the numbers. I could get my eyepiece down to about 60" using a 7.3" diagonal. That would leave 93.1% of the area of my mirror unobstructed. My secondary would be 132" from the primary. That will be real tempting since I use curved spiders anyway. I just didn't want to block all the light.
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