Beginner: Which to Buy? ETX-70 or 6" Newtonian Refractor?

"David Jones" wrote in message
om...
Yeah I have a pair of 10x50 Bushnells... old but they do the trick. I
am amazed at dusk how many more stars can be seen through the
binoculars than with the naked eye.

I'm still keen on getting something... while the ETX-70 GOTO features
are neat it sounds like it is too small a scope.

OK... Same place that is selling the 6" Newtonian Reflector is also
selling this...


http://www.citiwellint.com/vu.php?pa...ng+Goods&age=+

a 90mm Maksutov-Cassegran with two 1.25" eyepieces (a 9mm and a 25mm)
for $189 CDN. It doesn't have an EQ mount or motor (nor the GOTO) but
it is larger than the ETX-70. My big concern is the mount... What
should I be looking for in a tripod/mount? I get the feeling that I
will want something with guides for setting azimuth,
elevation(altitude) and declination? or how how else does a newbie
end up finding things?
The big problem is that mounts that have really nice 'smooth' motions, and
reasonable rigidity, are expensive. Basically, the 'best' small mount
around, is probably the Vixen GP-DX, and it's slightly smaller brother the
GP. These mounts have been 'copied' by allmost everybody, and some of the
copies are quite good (though few have quite the gear quality shown by the
Vixen units). The Celestron copy, in it's 'latter' incarnation (with
improved RA bearings), can work quite well, but usually needs some 'tuning'
to be really good. Generally, a reasonable mount, will cost as much as the
scope on it. 80% of the aluminium tripods supplied with scopes, are too
'springy' to really work well (one option that is quite cheap, and gives
excellent results, is to replace the legs on such a tripod, with timber ones
made from a wood like ash - surveyors tripods are also suprisingly cheap,
and a lot better than 95% of the normal telescope ones).
Maksutov scopes, are often quite good, but have the disadvantage, of
relatively long focal lengths. This gives relatively high magnifications
(making them good for 'planetary' observation), but relatively small FOV's,
which can make them less useful for 'deep sky' observation.
There is a problem, because of your desire to image. Basically, imaging,
puts more demands on the mount, and the 'starting point', tends to be
higher, than for basic viewing. For simple viewing, the 'Dobsonian mounted
Newtonian', is the cheapest system, with the downside that you have to move
the scop yourself, but the plus of putting the money into the optics. The
Hardin Optical units are probably the best 'value' around at the moment,
being one of a number coming from Chinese manufacturers, with reasonable
optics. The Orion 'Intelliscope' series, are similar, but add a 'push to'
system, which tells you where the scope is pointing.
The way people find things with scopes, depends (a little) on the mount, but
the simplest way, is 'star hoping'. Basically most interesting objects, have
recognisable 'bright' stars reasonably close, or patterns that 'point' to
them. With a EQ mount, there are normally RA/Dec 'dials' on th axes, and you
can point the scope to a known object, and then adjust the dials so that the
reading corresponds to the RA/Dec of that object. Then if you move the scope
to the RA/Dec of the desired target, it will be pointing at the right spot.
I really have to support the suggestion, that you see if there is an
astronomy club nearby. It is terrifyingly easy to spend a lot of money on
astronomy equipment, and not get what you really want. Learning what
equipment does, is far cheaper, by looking at other people's kit, than by
buying it yourself!...

Best Wishes

What should I be looking for in a tripod/mount? I get the feeling that I
will want something with guides for setting azimuth, elevation(altitude) and
declination? or how how else does a newbie
end up finding things?

This is a good question.

There are several ways to find things.

1. Just start looking, wander around until you find something that is
interesting. Use a low power eyepiece to provide a wide field of view. I
enjoy doing this.

2. Starhopping: Using a star chart(paper or software) and the telescope's
finder, locate the desired target. Start with a bright, easily recognizable
star and find a path. Sky and Telescope has several monthly columns that are
a big help in this regard. I like Sue French's small telescope column, lots of
interesting stuff to see.

3. Setting circles, either analog or digital. You align your scope and then
using the dials or the controller, set it to the proper coordinates for a given
object. Takes decent alignment.

4. GOTO. A computerized telescope that once aligned, will hopefully point
itself at some target.

The choice of a telescope does depend on which of these techniques you are
likely to use.

Which technique will suit your needs really depends on you.

Myself, a big part of the enjoyment comes from learning the sky and learning to
locate the objects by myself. Each time I find something, whether it is the
first time or the 200th time, its a thrill.

As the years have tumbled past, my understanding and knowledge has grown so
that I have a pretty good knowledge of how large chunks of the night sky is put
together.

Some observers find Starhopping frustrating, they want to be looking at the
target as soon as possible. For me, I enjoy just looking at the star fields as
the pass in front of my eyes.

If learning your way around the sky is high on your list of reasons you are
interested in astronomy, then you will probably want a scope that optimized for
starhopping.

The things that are important for starhopping are a widefield of view, enough
aperture to see some real stuff and an easy to use intuitive mount.

I think that a 6-10 in DOB is the ideal scope for Starhopping. The shorter
focal length of the medium size DOBs allows for the wider field of view with a
bright image, the mount is stable and easy to setup and use. Best Bang for the
Buck,

For use with setting circles or GOTO, there are other priorities. The scope
points itself once aligned and the observer enjoys the target.

If one is on a budget, then one trades optical performance for the
electronics, not such a great trade. Small GOTO scopes by Meade and Celestron
have databases that include many objects one will never see because they are
beyond the ability of the scope.

So GOTO certainly has advantages, but the choice between having to point the
scope yourself in order to see an object and having the telescope point at
something you cannot see is an obvious one, so first comes optics...

-----------

Regarding the 90mm MAK on a photo style tripod. THis scope has a 1200mm focal
length and takes 1.25 inch eyepieces. The maximum field of view will be
something like 50degree (AFOV Eyepiece) x focal length eyepiece/focal length
scope. With the optimal 32 mm plossl, it will provide a 1.3 degree FOV, not so
bad, but the image will be dim because of the small aperture. The finder will
not be too helpful either.

This is not a good scope for starhopping.

Bottomline: Please check out your local astronomy club and get some eyepiece
time in before spending your hard earned cash. Amateur Astronomers are a
friendly lot who just love to show you their junk and talk about it..

Take advantage of this so that when you do buy a scope, you will get one that
does the job for you.

Best wishes, clear skies

jon

On 28 Apr 2004 11:02:27 GMT, (Jon Isaacs) wrote:

4. GOTO. A computerized telescope that once aligned, will hopefully point
itself at some target.

My ETX-125 works just fine in this regard, and has the sharpest
resolution of any telescope I've yet owned. Between the GOTO and
resolution, I've found and seen things I've never been able to find or
see before.



--------------
Beady's Corollary to Occam's Razor: "The likeliest explanation of any phenomenon is almost always the most boring one imaginable."


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That's lots of good feedback thanks all...

I'm pretty sure the ETX-70 is out. While the GOTO sounds great... I can't
abide by spending $200 USD on one and when I'm done with the duty and taxes
have an automated 70mm monocular for about $400 cdn. As for the suggestions
for a Dobson... they all look pretty combersome to me and I would need to
move them to get a decent spot for viewing.

So that means I'm looking at the...

6" Newtonian Reflector (I got that right this time... not a refractor)
Orbitor OR9000 with Motorised Equatorial Mount
http://www.citiwellint.com/vu.php?pa...ng+Goods&age=+

This is how it is described...
The OR9000 is a superior, premium-quality reflector telescope for the
serious enthusiast, featuring a 6.0" / 152mm objective and a 750mm focal
length. With 30-375X magnification power, this orbitor model boasts amazing
optics, superb light gathering power and a motorized equatorial mount for
accurate and precise tracking of celestial objects. The OR9000 includes two
high quality 1.25" Kellner eyepieces (4mm and 25mm), 2X Barlow, large 6 x 35
power finderscope, rack and pinion focusing, plus a full-height heavy duty
aluminum tripod with accessory tray.

or a

90mm Compact Maksutov-Cassegran Telescope Orbitor OR3900

http://www.citiwellint.com/vu.php?pa...ng+Goods&age=+

This is how it is described...

The OR3900 is premium quality, ultra compact, weatherproof
Maksutov-Cassegrain telescope. With 48-400X magnification power, this
orbitor model serves as both a high power spotting scope for daytime/land
use, and as a razor sharp astronomical telescope for planetary and deep
space observing. With its 1200mm focal length and bright 3.6" / 90mm
objective lens, the OR3900 also performs as an extremely portable telephoto
lens (with optional 35mm SLR camera adapter). Also features an 8x21
finderscope, two viewing ports, two 1.25 " eyepieces (9mm and 25mm), 3X
Barlow, 45 degree terrestrial viewing prism and a full-height heavy duty
aluminum tripod with accessory tray.



I like the mount on the OR9000, however I like the fact I could use the
OR3900 for terrestrial photos with my Sony Mavica CD400 (I'll need the
adaptor from Scopetronix)... Still undecided. They are roughly the same
price (about $200 CDN) from a discount (misguided freight) reseller nearby.

I live in a small town in Southern Ontario... there is moderate light
pollution where I am (mostly street lights)... but I can get reasonable
dark skies with only a 5 minutes drive onto the Niagara escarpment. Last
night I had a great view of Venus with my 10x50's and a small 50mm scope (a
$30 Orbitor kid scope). Sine an ETX-70 is only 20mm larger than this scope
I can't imagine the view would be any better.

I suppose if I was going to spend up to $400 CDN on a ETX-70 I might as well
get both anyway. See which one I like and use more often and sell the other
one.

Any opinions are still welcome and thanks for the great advice so far.

On Wed, 28 Apr 2004 11:12:16 -0400, "XxXxXxX" wrote:

That's lots of good feedback thanks all...

I'm pretty sure the ETX-70 is out. While the GOTO sounds great... I can't
abide by spending $200 USD on one and when I'm done with the duty and taxes
have an automated 70mm monocular for about $400 cdn. As for the suggestions
for a Dobson... they all look pretty combersome to me and I would need to
move them to get a decent spot for viewing.

IMHO, compared to an equatorial mount a Dobson is not cumbersome at
all. I believe if you look up *cumbersome* in the dictionary, you'll
find a picture of an EQ mount. :^)

Good luck in the search...

Les Blalock
http://www.txastro.com

Live and learn I guess... The problem is that scopes are hard to find in
our area and expensive...


Check out:

http://stargazer.isys.ca/

My ETX-125 works just fine in this regard, and has the sharpest
resolution of any telescope I've yet owned. Between the GOTO and
resolution, I've found and seen things I've never been able to find or
see before.

I happen to currently own an ETX-125EC. (Its for sale.) Yes, the GOTO does
work quite well. But at F15 and using 1.25 inch eyepieces, the maximum field
of view is under 1 degree and without restrictng the FOV, the maximum exit
pupil is barely over 2mm.

I find that the sharpness/resolution of my Orion Space Probe 130ST (5 inch F5
Newt) to be comparable but I can see many more things with it because it offers
the possibility of a 3 + degree FOV with a 6+mm exit pupil.

An ETX-125 costs well over a grand by the time you are done. For this kind of
money, a 10 inch or 12 inch DOB will certainly offer better resolution and show
things in detail that are not possible in any 5 inch Scope..

Jon

Well they all look VERY big to me... and how do you set them up on a rough
surface...

As others have pointed out, inch for inch, a Dobsonian is more compact and less
cumbersome than an EQ mount.

There are several vendors in Canada that sell scopes similar to the Orion and
Hardin Optical line and seem to offer good prices. No need to pay the US duty.

When it comes to optics, well, it is nice to get by without spending a great
deal of money. The problem is that decent quality optics are expensive to make
so if one is buying a 6 inch scope for $200, it means that some corners must
have been cut. The two places where serious compromises are normally made is
in the optics and the mount. A poor scope on a shaky mount is just not fun to
use.

On the other hand, many of us here started with a poor scope on a poor mount, I
certainly did. It did not stop me from enjoying astronomy. But I soon moved
up.

So the hope I have is that you can spend your money on a scope that is capable
of providing many hours of enjoyment with out learning the hard way.....

That said, if you are determined to buy one of the two scope, the 90mm or the 6
inch, I would have to suggest the 6 inch and make sure you keep all the
packaging so that you can return it if you are dissatisfied.

jon

OK...

So here is what happened... I actually bought both the Orbitor 6"
Newtonian (OR9000) and the 90mm MAKS (OR3900).

I have yet to setup the 6" Newtonian, I have setup the 90mm MAKS.

The 90mm MAKS is very cool and easy to use. I aligned the 8x20 finder
and it is pretty much bang on... (I can see buds on trees about 800
feet away).

I've already used it for getting a glimpse at Jupiter, The Moon, Venus
and Saturn.

It has two eyepieces, one at 90 degrees and another on a 45 degree
mirror. Switching between the two is as easy as flipping a lever. It
came with a Kelner 25mm and 9mm eyepiece. It is so cool to be able to
flip from one to another... I have to attach the 2x barlow at some
time. My only criticism of this purchase is the mount... cheap
doesn't describe it. It was so bad I switched to my vivitar camera
tripod. Needless to say I'm searching eBay and Astromart for a decent
mount for this scope.

The scope regularly retails for about $399 so I'm very happy with it.
I've just ordered a Scopetronix adaptor for my camera and can't wait
to start snapping some pics.

As for the Newtonian... Well I just need some time to set it up and
give it a whirl.

OK so we setup the the OR9000 (6" Newtonian)...

Not to be done at night over a few beers. The mount is MUCH better
than I thought it would be (however, really complex). I'm not as fond
of the eyepieces.

The whole setup is huge... I see why people like the more compact
cassigrain scopes.


(David Jones) wrote in message . com...
OK...

So here is what happened... I actually bought both the Orbitor 6"
Newtonian (OR9000) and the 90mm MAKS (OR3900).

I have yet to setup the 6" Newtonian, I have setup the 90mm MAKS.

The 90mm MAKS is very cool and easy to use. I aligned the 8x20 finder
and it is pretty much bang on... (I can see buds on trees about 800
feet away).

I've already used it for getting a glimpse at Jupiter, The Moon, Venus
and Saturn.

It has two eyepieces, one at 90 degrees and another on a 45 degree
mirror. Switching between the two is as easy as flipping a lever. It
came with a Kelner 25mm and 9mm eyepiece. It is so cool to be able to
flip from one to another... I have to attach the 2x barlow at some
time. My only criticism of this purchase is the mount... cheap
doesn't describe it. It was so bad I switched to my vivitar camera
tripod. Needless to say I'm searching eBay and Astromart for a decent
mount for this scope.

The scope regularly retails for about $399 so I'm very happy with it.
I've just ordered a Scopetronix adaptor for my camera and can't wait
to start snapping some pics.

As for the Newtonian... Well I just need some time to set it up and
give it a whirl.