Klein aber fein: der neue 8“ f/7 ist fertig

Hallo zusammen,

bisher leider immer noch nicht als Wolken, daher leider noch kein First Light Bericht. Ich habe allerdings noch Carl Zambutos Einschätzung zu der Frage von Konrad (fastride) bezüglich des Öffnungsverhältnisses. Carl hat den Beitrag hier gelesen und mir seine Einschätzung zu Konrads Frage gemailt, die ich in seinem Namen hier einfügen darf:

"Someone on the site asked about whether F/6 is good enough and why go longer.
The secondary obstruction is the least concern. I think the real reasons are three-

One, coma is present to some degree inside of 19mm at the focal plane until you get to F/10. Clyde Tombaugh
observed through a 16” F/10 telescope for planet purpose.

Two- a longer focal length produces greater magnification with a given eyepiece, which is also a smaller exit pupil
and darker sky (background). This is better for contrast.

Three, eyepieces that correct for coma are not necessary because the field is already flat. This allows for
more pristine eyepieces that are geared toward observing and not wide field “showpiece" views. Long focus
is great for Aus Jena and Zeiss eyepieces for example.

You already know all this.

Those who are veteran observers such as yourself know that longer is always better. The only advantage
of shorter focal length is compactness of the telescope. I think the F/3 telescopes that are not for wide field use
but rather for being very large and very compact are stupid. I NEVER hear any rave review about quality of view.

I once evaluated a mirror that would now be 140 years old. It was made by Hereford With.
He only star tested for bench results. It was an 8” at F/12. I have planet photos taken with the mirror, they are superb.

Again, fabulous build on your scope, and I’m glad its at F/7 instead of F/6. My favorite telescope of all time was a 10” F/7.

Carl"

Liebe Grüße,
Matthias