Dear colleagues, I'm about to have to dig into some work and will be away
from the mailing list for a while. Here are some reponses to several
recent messages. To see what I'm working on, look at
www.covingtoninnovations.com/telescope.

Clear skies and good pointing,
Michael

>
> > Michael Covington wrote:
> > <<1-star alignment is inherently inaccurate and very much at the mercy
of
> > leveling and site data. Do a 2-star alignment and you'll be pleasantly
> > surprised. In my opinion, it was a mistake for them to even offer
1-star
> > alignment -- it is a flawed concept. Two stars are necessary (and
> > sufficient) to determine the position of the celestial sphere.>>
>
> This is a silly statement. Permanently mounted LX200 scopes always
> use one star alignment. It works perfectly. One star alignment IS
> NOT a flawed concept at all.

Sorry, I should have made it clear that I meant in altazimuth mode on
portable tripods. You're talking about polar mode, where one point (the
celestial sphere) is already fixed by the axis of the mount.

> Kevin Wigell wrote:
>
> > Michael, I'm curious why you think the 1-star alignment should not have
been
> > offered.

It assumes more accuracy than you're going to get from a bubble level. If
offered, it should at least come with a warning that it is less accurate
than 2-star alignment. (The manual makes this pretty clear, actually, but
people seem to overlook it.) Beginners fall right into the trap -- they
think 1-star alignment is half as much work as 2 stars, when really it's
more work because the leveling is critical.

> > On a slightly different topic, there have been many posts lately about
> > getting the time and location correct in order to ensure accurate
slewing.
> > You've said it before, but apparently many missed it. Time and location
> > entry in the LX-200 brains have NOTHING to do with accurate slewing,
once
> > you've done a good 2-star alignment. I haven't tried it myself, but I
> > believe you can enter any time, date, and location that you want, and
once
> > you do a 2-star alignment, you should still be able to accurately slew.

In fact the NexStar 5 does not even *ask* you your time, date, or location
when you are setting it up that way. I need to do some experiments to make
sure the LX200 is indeed not influenced by site or time data in some strange
way (other than, of course, atmospheric refraction correction near the
horizon). I'm confused by all the reports I see here of an LX200
misbehaving when the time of day is set wrong, which it shouldn't do. I
await enlightenment. If we ever have any clear weather I'm going to enter
the wrong time into my LX200 and see what it does.

> 1-star alignment is not flawed when you consider its purpose. Check p. 33
of
> the (1996) manual (version 0196-2). It is very clear that 1-star
alignment is
> to be used for permanently mounted, level scopes. That's what I have, and
it
> works just fine, as stated.

Noted... It had not occurred to me that people would build permanent mounts
and level them rather than polar-aligning them. I use 1-star alignment on
my permanently polar-aligned pier all the time. What I meant was that
1-star alignment of a portable altazimuth telescope is a flawed concept and
beginners should be steered away from it rather than toward it.

> Date: Sat, 02 Jun 2001 00:32:06
> Subject: [M]: Re: LX200 and Wedge
>
> Just curious, why would you bother to mount a computer driven scope such
as
> an LX200 or a Nexstar on a wedge if you were only going to do visual
> observing?? Either scope is "much" more stable and accurate in GOTO in
the
> alt-az mode. Now if you were going to do photography of imaging, then I
> understand. Am I missing something?

As far as I can see, only for double star work or work with charts where you
need your slewing directions to be exactly north, south, east, and west. As
you note, the LX200 go-to accuracy is at the mercy of the polar alignment,
so if you're going to use a wedge at all, you have to align it carefully
(which can actually be done rather quickly once you're used to it). In
altaz mode the LX200 can correct for leveling errors in both directions.
The NexStar 5 has an equatorial mode in which you align on 2 stars and it
then has good pointing accuracy in spite of polar alignment error. I think
the LX90 does too -- can someone confirm?

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