Re: optical telescope choice

[Ken Olum <kdo cosmos phy tufts edu>]

Hi, all.  Here are some thoughts about the Celestron CPC Deluxe 1100 HD
vs the Nexstar Evolution 925.

The obvious advantage of the the Deluxe 1100 is that it is larger
[(11/9.25)^2 = 1.4 times more light].  This obvious disadvantage is that
it is more expensive, but my understanding is that in our case it
doesn't matter because otherwise we'd have to return the money.  Only
about half the price is due to the size, because there is a Deluxe 925,
and that is $4,299.  So this line is probably better in optical quality.

The Nexstar has Wifi, whereas the Deluxe has an attached handheld
control.  I don't immediately see why it makes much difference. The
Nexstar has a built-in battery, whereas the Deluxe attaches to your car
or plugs in to the wall.  I wouldn't really expect to carry it far from
my car, so this probably doesn't make much difference either.

The Nexstar "mount head weight" is 36 lbs.  I think this means
everything but the tripod.  For the Deluxe 1100 it is 65 lbs.  Again,
there's not much dependence on the size, the Deluxe 925 mount head
weight is 58 lbs.  The Nexstar tripod weighs 19 lbs, and the Nexstar
tripod 26.6 lbs.  Presumably this is the additional weight of the
battery.  I don't know how these telescopes are packed up for travel, so
I don't know if you have to carry the whole mount head weight at once.

It looks like the Deluxe takes either 2" or 1.25" eyepieces, whereas the
Nexstar takes only 1.25".  This seems like an important advantage to
me.  For large, faint objects, you need to have low magnification, so
the small amount of light is not spread out over too much of your visual
field.  The smallest usable magnification on the Deluxe 1100 is 40X, and
for that you would need a 70mm of eyepiece, which doesn't exist, as far as 
I
can tell.  But you can get 56mm.  You can't get it in 1.25", however,
because such an eyepiece with a reasonable field of view would not fit in
a 1.25" tube.

I have a friend who knows about these things.  I'll ask him for more
advice.

                                        Ken