SCT Dobsonian?

Pardon my ignorance on this, but why are there not SCT's with Dobsonian
mounts? I mean, would it not make sense as then you would not need a ladder
to view large aperture Dob scopes? Of course, unless the scope was mounted
a little higher than a Newtonian Dob, you'd have to lie on the ground.
Still stooping low seems safer and easier than climbing a ladder.

Thoughts?

Dark Helmet

"Dark Helmet" wrote in
. net:

Pardon my ignorance on this, but why are there not SCT's with
Dobsonian mounts? I mean, would it not make sense as then you would
not need a ladder to view large aperture Dob scopes? Of course,
unless the scope was mounted a little higher than a Newtonian Dob,
you'd have to lie on the ground. Still stooping low seems safer and
easier than climbing a ladder.

Thoughts?

Dark Helmet




Well you could buy an SCT OTA and install it on a dob mount yourself. The
main problem is that you would have to crouch down to look through the
eyepiece unless you made a really tall mount. The fork mounts of most
SCT's bring the eyepiece to about the right height when sitting on a
suitable tripod. The Newtonian is better suited to the dob mounting
system because of the position of the eyepiece.

L.

"Dark Helmet" wrote in
. net:

Pardon my ignorance on this, but why are there not SCT's with
Dobsonian mounts? I mean, would it not make sense as then you would
not need a ladder to view large aperture Dob scopes? Of course,
unless the scope was mounted a little higher than a Newtonian Dob,
you'd have to lie on the ground. Still stooping low seems safer and
easier than climbing a ladder.

Thoughts?

Dark Helmet




Well you could buy an SCT OTA and install it on a dob mount yourself. The
main problem is that you would have to crouch down to look through the
eyepiece unless you made a really tall mount. The fork mounts of most
SCT's bring the eyepiece to about the right height when sitting on a
suitable tripod. The Newtonian is better suited to the dob mounting
system because of the position of the eyepiece.

L.

"Dark Helmet" wrote in alt.astronomy:

Pardon my ignorance on this, but why are there not SCT's with
Dobsonian mounts? I mean, would it not make sense as then you would
not need a ladder to view large aperture Dob scopes? Of course,
unless the scope was mounted a little higher than a Newtonian Dob,
you'd have to lie on the ground. Still stooping low seems safer and
easier than climbing a ladder.

Maybe because there's no market for it? Like there's no Rolls-Royce with
wooden kitchen chairs in it? What's the pojnt of buying an expensive car
and save money on the chairs?

A Dob is not _a_ mount, it's a _cheap_, _easy_ and _simple_ mount. Buying
an expensive SCT with such a cheap and simple mount..... in that case
you'd better buy a hughe and large aperture Dob with the az-mount for the
same money you'd buy that smaller SCT for.



--
CeeBee


Uxbridge: "By God, sir, I've lost my leg!"
Wellington: "By God, sir, so you have!"


Google CeeBee @ www.geocities.com/ceebee_2

"Dark Helmet" wrote in alt.astronomy:

Pardon my ignorance on this, but why are there not SCT's with
Dobsonian mounts? I mean, would it not make sense as then you would
not need a ladder to view large aperture Dob scopes? Of course,
unless the scope was mounted a little higher than a Newtonian Dob,
you'd have to lie on the ground. Still stooping low seems safer and
easier than climbing a ladder.

Maybe because there's no market for it? Like there's no Rolls-Royce with
wooden kitchen chairs in it? What's the pojnt of buying an expensive car
and save money on the chairs?

A Dob is not _a_ mount, it's a _cheap_, _easy_ and _simple_ mount. Buying
an expensive SCT with such a cheap and simple mount..... in that case
you'd better buy a hughe and large aperture Dob with the az-mount for the
same money you'd buy that smaller SCT for.



--
CeeBee


Uxbridge: "By God, sir, I've lost my leg!"
Wellington: "By God, sir, so you have!"


Google CeeBee @ www.geocities.com/ceebee_2

On Thu, 30 Oct 2003 00:58:25 GMT, Dark Helmet wrote:

Pardon my ignorance on this, but why are there not SCT's with Dobsonian
mounts? I mean, would it not make sense as then you would not need a ladder
to view large aperture Dob scopes? Of course, unless the scope was mounted
a little higher than a Newtonian Dob, you'd have to lie on the ground.
Still stooping low seems safer and easier than climbing a ladder.

Thoughts?

Think about where the focal plane on an SCT is.


--
- Mike

Remove 'spambegone.net' and reverse to send e-mail.

On Thu, 30 Oct 2003 00:58:25 GMT, Dark Helmet wrote:

Pardon my ignorance on this, but why are there not SCT's with Dobsonian
mounts? I mean, would it not make sense as then you would not need a ladder
to view large aperture Dob scopes? Of course, unless the scope was mounted
a little higher than a Newtonian Dob, you'd have to lie on the ground.
Still stooping low seems safer and easier than climbing a ladder.

Thoughts?

Think about where the focal plane on an SCT is.


--
- Mike

Remove 'spambegone.net' and reverse to send e-mail.

"CeeBee" wrote in message
. 6.67...
"Dark Helmet" wrote in alt.astronomy:

Pardon my ignorance on this, but why are there not SCT's with
Dobsonian mounts? I mean, would it not make sense as then you would
not need a ladder to view large aperture Dob scopes? Of course,
unless the scope was mounted a little higher than a Newtonian Dob,
you'd have to lie on the ground. Still stooping low seems safer and
easier than climbing a ladder.

Maybe because there's no market for it? Like there's no Rolls-Royce with
wooden kitchen chairs in it? What's the pojnt of buying an expensive car
and save money on the chairs?

A Dob is not _a_ mount, it's a _cheap_, _easy_ and _simple_ mount. Buying
an expensive SCT with such a cheap and simple mount..... in that case
you'd better buy a hughe and large aperture Dob with the az-mount for the
same money you'd buy that smaller SCT for.


Ok, is it the SCT itself that is expensive? Or is it the SCT mount? As far
as I can tell, the only major differences between a Newt and an SCT OTA are

1. The mounting/design of the secondary mirror (any difference in cost
between the two?)
2. The hole/design of the primary mirror (must be slightly more expensive)
3. The lens of the SCT, which a Newt doesn't have (definitely more
expensive, but how much?)
4. The tube itself in an SCT is usually something pretty exotic, but does
it have to be?

I guess the cost of the OTA doesn't seem like it should be significantly
different for either. Please help me understand why it would be.

My point is this. An amateur 14" SCT runs into the $5m+ range. A decent
17.5" Dob runs in the $2.5m range. Once you start getting into this size
range and up on a Dob, you start talking ladder time. Why not have, say, a
large 20" SCT design on a Dob mount, but with the mount a little higher so
you have to sit down low to look? Couldn't an SCT also use a Truss design
or be built around a cheap tube like most non-Truss Dob's? Really, I'm just
thinking out loud here, but I'd like to hear some thoughts. It all comes
down to I like the thought of owning a big Dob, but I can't stand having to
use a ladder to see some objects. It's just not safe or comfortable.

Thanks,

Dark Helmet

"CeeBee" wrote in message
. 6.67...
"Dark Helmet" wrote in alt.astronomy:

Pardon my ignorance on this, but why are there not SCT's with
Dobsonian mounts? I mean, would it not make sense as then you would
not need a ladder to view large aperture Dob scopes? Of course,
unless the scope was mounted a little higher than a Newtonian Dob,
you'd have to lie on the ground. Still stooping low seems safer and
easier than climbing a ladder.

Maybe because there's no market for it? Like there's no Rolls-Royce with
wooden kitchen chairs in it? What's the pojnt of buying an expensive car
and save money on the chairs?

A Dob is not _a_ mount, it's a _cheap_, _easy_ and _simple_ mount. Buying
an expensive SCT with such a cheap and simple mount..... in that case
you'd better buy a hughe and large aperture Dob with the az-mount for the
same money you'd buy that smaller SCT for.


Ok, is it the SCT itself that is expensive? Or is it the SCT mount? As far
as I can tell, the only major differences between a Newt and an SCT OTA are

1. The mounting/design of the secondary mirror (any difference in cost
between the two?)
2. The hole/design of the primary mirror (must be slightly more expensive)
3. The lens of the SCT, which a Newt doesn't have (definitely more
expensive, but how much?)
4. The tube itself in an SCT is usually something pretty exotic, but does
it have to be?

I guess the cost of the OTA doesn't seem like it should be significantly
different for either. Please help me understand why it would be.

My point is this. An amateur 14" SCT runs into the $5m+ range. A decent
17.5" Dob runs in the $2.5m range. Once you start getting into this size
range and up on a Dob, you start talking ladder time. Why not have, say, a
large 20" SCT design on a Dob mount, but with the mount a little higher so
you have to sit down low to look? Couldn't an SCT also use a Truss design
or be built around a cheap tube like most non-Truss Dob's? Really, I'm just
thinking out loud here, but I'd like to hear some thoughts. It all comes
down to I like the thought of owning a big Dob, but I can't stand having to
use a ladder to see some objects. It's just not safe or comfortable.

Thanks,

Dark Helmet

"Dark Helmet" wrote in
. net:

"CeeBee" wrote in message
. 6.67...
"Dark Helmet" wrote in
alt.astronomy:

Pardon my ignorance on this, but why are there not SCT's with
Dobsonian mounts? I mean, would it not make sense as then you
would not need a ladder to view large aperture Dob scopes? Of
course, unless the scope was mounted a little higher than a
Newtonian Dob, you'd have to lie on the ground. Still stooping low
seems safer and easier than climbing a ladder.

Maybe because there's no market for it? Like there's no Rolls-Royce
with wooden kitchen chairs in it? What's the pojnt of buying an
expensive car and save money on the chairs?

A Dob is not _a_ mount, it's a _cheap_, _easy_ and _simple_ mount.
Buying an expensive SCT with such a cheap and simple mount..... in
that case you'd better buy a hughe and large aperture Dob with the
az-mount for the same money you'd buy that smaller SCT for.


Ok, is it the SCT itself that is expensive? Or is it the SCT mount?
As far as I can tell, the only major differences between a Newt and an
SCT OTA are

1. The mounting/design of the secondary mirror (any difference in
cost between the two?)
2. The hole/design of the primary mirror (must be slightly more
expensive) 3. The lens of the SCT, which a Newt doesn't have
(definitely more expensive, but how much?)
4. The tube itself in an SCT is usually something pretty exotic, but
does it have to be?

I guess the cost of the OTA doesn't seem like it should be
significantly different for either. Please help me understand why it
would be.

My point is this. An amateur 14" SCT runs into the $5m+ range. A
decent 17.5" Dob runs in the $2.5m range. Once you start getting into
this size range and up on a Dob, you start talking ladder time. Why
not have, say, a large 20" SCT design on a Dob mount, but with the
mount a little higher so you have to sit down low to look? Couldn't
an SCT also use a Truss design or be built around a cheap tube like
most non-Truss Dob's?

Sure. The cost is going to be much higher than a 20" truss newtonian.
Once you get to this size in SCT's you are talking custom design and
build. A dob mount which lifts the eyepiece of a 20" SCT to a comfortable
viewing height is going to be big and heavy to be stable - it wont be
portable.

L

SNIP