More on Dobsonians...

I suspect it's simply a case of Hardin being a bit more honest.

In my experience, the cases where you'd want more than 250x
magnification are fairly rare. My primary scope is a TScope 14"
f/4.7 Dobsonian, and the two eyepieces I use the most are the
two with lowest power--a 32mm Plossl (52x) and 30mm 1rpd wide-
field (55x). My main use of higher magnifications is for
splitting double stars, and better views of globulars and
planetary nebulae. Even for planets and the Moon, seeing is
rarely good enough to make magnifications beyond 200x worthwhile.
I do have 5mm and 3mm TeleVue Radians (332x, 554x) for nights
with exceptional seeing.

So if we define "useful" as "magnification you're likely to have
occasion to use", Hardin's 250x is a more honest figure, IMO.

-Paul W.

On 13 Apr 2005 18:01:38 -0700, (Clarky) wrote:

I was just looking at the dobsonians again, and had another question.
Both the Celestron 10 inch and the Orion 10 inch both say that they
have a "maximum useful magnification" of 600. The Hardin 10 inch
Dob's "maximum useful magnification" is only 250. I know that
magnification isn't all that important, but that seems like a pretty
big jump, although I'm not sure 'cause I'm new to all this. Does
anyone have any thoughts on why the Hardin would be so much lower than
the other two?

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I give Hardin lots of credit on this one, under-stating and
under-promising, and being more realistic about power. That's a
testament to integrity given that many beginners might be considering
his scopes.

Larry Stedman
Vestal

On 14 Apr 2005 07:45:12 -0700, shneor wrote:

X-No-Archive: Yes
"...dobs are hand-driven..." - NOT for many of us. I've been using an
equatorial platform for over 8 years, as have many others. Some folks
use a Bartels drive. And there are other systems in use to keep dobs
tracking accurately. I regularly view at 750X when conditions permit,
and the image will stay in the field for half an hour, if I have set up
accurately.

Shneor

I'm not sure John Dobson had electronic tracking and equatorial platforms
in mind when he popularized large, inexpensive newtonians, and gave his
name to a simple, elegant alt-azimuth configuration.

None-the-less, I envy your set up. 750x is more than I'll ever hope to
use in this lifetime.

Cheers,
Larry G.