Getting a 10" dob...question on adding things to cart.

Sorry for the fuss here tonight. I have settled on the Dobs, rather than
the
adventure into Apochromats. It's the money.

Nobody has said why the Orion XT10 is worth 50 bucks more, and the
Hardin comes with Messier list and a moon filter if I remember correctly.
I'll go with the Hardin I guess. There is a barlow lense offered for 50
bucks
as an accessory. I assume this scope can handle a 300x magnification, but
the
barlow is achromatic. Would an achromatic barlow cause chromatic aberation
in a newtonian scope?

Also, there is the laser collimator. I read some literature here on star
testing, so
does this make the laser obsolete? And one more thing, bear with me
here....
is correcting the optics just a harmless excersise in trial and
error...lighly tweaking
the screws? I have read how to tell if something is wrong, and even what is
wrong, but not much on which screws to tweak. -Thanks.
Tom

Tom wrote:

Sorry for the fuss here tonight. I have settled on the Dobs, rather than
the
adventure into Apochromats. It's the money.

You'll be a happier camper with the dob, if it's your first scope. 10"
is a very good starting aperture. You'll likely never run out of things
to see.

Nobody has said why the Orion XT10 is worth 50 bucks more, and the
Hardin comes with Messier list and a moon filter if I remember correctly.
I'll go with the Hardin I guess.

I think I recall someone or some reviewer somewhere stating that the
Hardin has a plastic secondary holder/spider that is not adjustable--is
this correct--I may be mistaken, but it's worth looking into. The Orion
has a steel spider.

There is a barlow lense offered for 50
bucks
as an accessory. I assume this scope can handle a 300x magnification, but
the
barlow is achromatic. Would an achromatic barlow cause chromatic aberation
in a newtonian scope?

Also, there is the laser collimator. I read some literature here on star
testing, so
does this make the laser obsolete?

You can't do a good star test if the seeing is poor, but poor seeing
doesn't affect laser collimators, at least not in amateur-sized
telescopes. ;-)

And one more thing, bear with me
here....
is correcting the optics just a harmless excersise in trial and
error...lighly tweaking
the screws? I have read how to tell if something is wrong, and even what is
wrong, but not much on which screws to tweak.

What screws to tweak depends on what is wrong.
Basically, it's:
1.) Square the focuser to the tube/optical axis. (shim/adjust screws
holding the focuser to the tube).
2.) Center the secondary in the focuser. (Adjust spider vane length and
secondary holder rod length)
2a.) add offset if desired
3.) Point the secondary at the center of the primary. (three or four
screws on the secondary holder)
4.) Point the primary back at the center of the focuser. (collimation
screws under the mirror cell).
5.) do a star test and start all over again ;-) --just kidding!

The above assumes the primary is centered in the optical tube.


Is this what you were wondering about, or have I misunderstood your
question?


Regards,
Uncle Bob

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Tom" wrote in message
...
Sorry for the fuss here tonight. I have settled on the Dobs, rather than
the
adventure into Apochromats. It's the money.

Nobody has said why the Orion XT10 is worth 50 bucks more, and the
Hardin comes with Messier list and a moon filter if I remember correctly.
I'll go with the Hardin I guess. There is a barlow lense offered for 50
bucks
as an accessory. I assume this scope can handle a 300x magnification, but
the
barlow is achromatic. Would an achromatic barlow cause chromatic
aberation
in a newtonian scope?

Also, there is the laser collimator. I read some literature here on star
testing, so
does this make the laser obsolete? And one more thing, bear with me
here....
is correcting the optics just a harmless excersise in trial and
error...lighly tweaking
the screws? I have read how to tell if something is wrong, and even what
is
wrong, but not much on which screws to tweak. -Thanks.
Tom



Congratulations on your Dob -- you'll enjoy it -- if you don't know the sky
very well (as I do not) you'll find yourself frustrated now and then by not
being able to immediately find what you are looking for but keep looking --
it's out there.

As someone else pointed out, you need to check into the spider/secondary
holder -- the Orion spider/secondary holder is steel and adjustable; the
Hardin may be plastic -- steel is better, much better.

Collimation: Forget the laser collimator. Use the collimating cap that
comes with the scope. Then, look around for a set of collimating tools made
by Tectron. You will also need a #2 Phillips screwdriver and a hex key to
fit the tiny hex head screws that adjust the tilt of the secondary.

Here is my experience with collimating my XT-8; hope you find something
useful here.
http://www.schlatter.org/Dad/Astronomy/collimate.htm

When you can, get a right-angle finder scope and a Telrad. Check it out
he
http://www.schlatter.org/Dad/Astronomy/xt%208.htm

Get some books and a planisphe
http://www.schlatter.org/Dad/Astronomy/books.htm

And you thought the telescope was expensive!!!

Also, get some clear skies without pollution from a nearby WalMart parking
lot.

---------------
Joe S.

On 22 Aug 2004 06:56:14 GMT, Manuel Joseph Din
wrote:


I think I recall someone or some reviewer somewhere stating that the
Hardin has a plastic secondary holder/spider that is not adjustable--is
this correct--I may be mistaken, but it's worth looking into. The Orion
has a steel spider.

I have the Hardin scope under another name.
It is manufactured by Guan Sheng in Taiwan whereas the Orions are made
by Synta in the PRC.

The hardin has a plastic secondary holder and the spider is steel. The
only known problems with this is that some of the plastic holders can
be a little tight and cause flexing of the secondary . A few minutes
with a piece of sandpaper will fix it.

Although the Orions and G.S scopes are similar in price and
performance, the G.S has a slight edge optically and being cheaper I
cant see why one would choose the Orion over the Hardin.

I think I recall someone or some reviewer somewhere stating that the
Hardin has a plastic secondary holder/spider that is not adjustable--is
this correct--I may be mistaken, but it's worth looking into. The Orion
has a steel spider.

I have an OPT Star Hunter 10, same thing as the Hardin scope and from the same
company that made the original XT-10, this is essentially an improved version
of the original XT-10. Great scope IMHO.

These scopes have a nice 4 vane steel spider assembly that is fully adjustable.
The secondary mirror holder is plastic. The difference between the Orion/Synta
scopes that I have seen and the GSO/Hardin/OPT is that the GSO scope enclose
and capture the secondary whereas the Synta secondary mirror is apparently just
glued in place.

Both work, but personally I prefer the fully captured design. I have seen
several 1.25 inch refractor/SCT diagonals that had the mirror glued on
improperly causing bad collimation. A poorly attached mirror that comes off
can be a real disaster.

The captured design, at least in some of the earlier 10 inch GSO models,
sometimes pinched the secondary and caused astigmatism. Mine had this problem
but once I discovered it and corrected it, the optics have turned out to be
quite amazing..

Collimation:

It should be relatively easy with the Hardin scope and one set it should only
require minor tweaks. Last year mine went on a 10 day, 2000 mile trip in a
motor home, in and out and setup every night, bouncing around and accidently
banged a few times. The collimation never needed to be touched.

Personally I recommend a good quality laser collimator and a collimation cap.
I first set the rotation of the secondary with collimation cap or cheshire and
then use the collimator to set the secondary tilt and Nils Olof Carlin's
"Barlowed Laser" technique to set the primary tilt.

The focuser should be square already, the new Hardin scopes have a nice looking
(in the photos anyway) Crayford focuser.

------

The primary advantage of the laser collimator is that one can use it anytime,
day or night. Cheshires are daytime only, star testing requires a nicely
cooled scope and good conditions.

I also recommend spending a few dollars extra and buying a premium laser
collimator like a Howie Glatter. (www.collimator.com) Normally I buy on price
but I wanted a good one so I spent a few dollars extra and bought one of
Howie's master pieces. I have had it about 5 years, still in perfect
collimation,it is made to close tolerances and is still on the same battery.

In my view, having a good tool like a Howie Glatter is something I will have
and use no matter what scopes I might own, its an investment, quality alignment
tools are a big help in getting accurate collimation. Howie machines these
from solid aluminum to tight tolerances and they are nice to look at...

It is my understanding the asian collimators are sometimes out of collimation
when they arrive and can be somewhat sloppy in the draw tube.

-----

Anyway, I think you have made a wise choice, I really like my GSO 10 incher,
lots of bang for the buck and for some of us, the ideal tool.

A DOB is like a bicycle, it won't do anything for you that you cannot do for
yourself, but those things you cannot do, it does a marvelously.

Best wishes, clear skies

jon isaacs

Thanks for the feedback everyone. The Hardin comes with an 1.25 Asrola 9mm
and an Astrola
2" eyepiece. I believe Ed Ting recommended a high end eyepiece to really
enhance the performance
of these things. If I added a TeleVue or something to the cart, what size
or type would fit the bill
in your opinion? Thanks, Tom

"Tom" wrote in message
...



Thanks for the feedback everyone. The Hardin comes with an 1.25 Asrola
9mm
and an Astrola
2" eyepiece. I believe Ed Ting recommended a high end eyepiece to really
enhance the performance
of these things. If I added a TeleVue or something to the cart, what size
or type would fit the bill
in your opinion? Thanks, Tom



Tom:

Now you've done it. You asked the Forbidden Question: Eyepiece
recommendations? :-)

Prepare to be overrun with recommendations and I will start the flood.

After two years of buying, selling, trading, this is what I use with my
8-inch Dob:

-- TeleVue 32mm Plossl -- sharp from edge to edge, wide views
-- Meade Super Wide Angle 18mm -- sharp from edge to edge, a favorite for
wide objects such as nebulae, globular clusters, and the like
-- Nagler Type 1 7mm -- a bit dated but wait until you see Jupiter or Saturn
with this eyepiece
-- Meade Ultra Wide Angle 6.7mm -- redundant to the Nagler 7mm but I got it
at an estate sale for $10.00, excellent eyepiece, I can't tell any
difference from the 7mm Nagler
-- Nagler Type 6 5mm -- use this one on planets, knocks my socks off
-- UO ortho 4mm -- planetary eyepiece, I love it
-- Televue 2X Barlow.

Your mileage may vary.


--

-----
Joe S.

"Tom" wrote in
:

Thanks for the feedback everyone. The Hardin comes with an 1.25
Asrola 9mm and an Astrola
2" eyepiece. I believe Ed Ting recommended a high end eyepiece to
really enhance the performance
of these things. If I added a TeleVue or something to the cart, what
size or type would fit the bill
in your opinion? Thanks, Tom

If you're set on getting a Televue the 27mm Panoptic is a very useful
eyepiece.

Don't forget at Telrad finder. It will be the best $39 you spend on your
scope. g

I just bought the 10" Hardin because of the really good reviews. I'm
hoping to receive it tomorrow. Cost, however, was about a tossup when
the "free" laser collimeter with the Orion is factored in.


On Sat, 21 Aug 2004 22:32:07 -0700, "Tom" wrote:

Sorry for the fuss here tonight. I have settled on the Dobs, rather than
the
adventure into Apochromats. It's the money.

Nobody has said why the Orion XT10 is worth 50 bucks more, and the
Hardin comes with Messier list and a moon filter if I remember correctly.
I'll go with the Hardin I guess. There is a barlow lense offered for 50
bucks
as an accessory. I assume this scope can handle a 300x magnification, but
the
barlow is achromatic. Would an achromatic barlow cause chromatic aberation
in a newtonian scope?

Also, there is the laser collimator. I read some literature here on star
testing, so
does this make the laser obsolete? And one more thing, bear with me
here....
is correcting the optics just a harmless excersise in trial and
error...lighly tweaking
the screws? I have read how to tell if something is wrong, and even what is
wrong, but not much on which screws to tweak. -Thanks.
Tom

"FAB" wrote in message
...

I just bought the 10" Hardin because of the really good reviews. I'm
hoping to receive it tomorrow. Cost, however, was about a tossup when
the "free" laser collimeter with the Orion is factored in.

I placed my order for that one too, and should get it Friday or Sat. I HOPE
I get the Crayford focuser, but not that I would know the difference
anyways.

Are you sure about the free Laser Coll. with the XT10? It is listed as a
suggested
option on the Orion site. One thing on the XT has that I like is the little
knob under
the front of the tube for easy guiding. I wonder if it is advisable to
drill a small hole
in the Hardin's, and screwing in a knob. Lots of knobs to choose from at
the Home
Depot. Just a thought. -Tom