newbie question

Alan,
It's a Bushnell (this is where I insert justification. It was a gift. It is
better than nothing)
675x4.5" Reflector
Focal length (mm)
900
thanks....
jojo

Far better than the first scope I ever owned..

How to collimate your scope with no tools, Larry Gilstrap' page:

http://gilstrap.home.texas.net/collimat/NoTools.html

jon

You don't have to wait until night...in fact, right now
in broad daylight is actually a better time to do it!
Tom W.



jojo wrote:

"bwhiting" wrote in message
...

For starters, look into the eyepiece hole (I am assuming
a reflector telescope here, with 2 mirrors) without an
eyepiece, and see if the complete reflection of the primary mirror is
reflected off the secondary mirror up thru the eyepiece
hole, AND if the secondary mirror
is centered in your eyepiece hole, which you can tell
by looking at the secondary holders (spider) mount.
They should be roughly equidistant in length.
If its not centered nearly perfectly, then you
are probably out of collimation....for starters.
Clear Skies,
Tom W.


Thanks Tom. I'll look at those tonight...
jojo

"Jon Isaacs" wrote in message
...
Alan,
It's a Bushnell (this is where I insert justification. It was a gift. It
is
better than nothing)
675x4.5" Reflector
Focal length (mm)
900
thanks....
jojo

Far better than the first scope I ever owned..

How to collimate your scope with no tools, Larry Gilstrap' page:

http://gilstrap.home.texas.net/collimat/NoTools.html

jon

jon,
Thanks, That is a great reference!!!!

jojo

"bwhiting" wrote in message
...
You don't have to wait until night...in fact, right now
in broad daylight is actually a better time to do it!
Tom W.



jojo wrote:

"bwhiting" wrote in message
...

For starters, look into the eyepiece hole (I am assuming
a reflector telescope here, with 2 mirrors) without an
eyepiece, and see if the complete reflection of the primary mirror is
reflected off the secondary mirror up thru the eyepiece
hole, AND if the secondary mirror
is centered in your eyepiece hole, which you can tell
by looking at the secondary holders (spider) mount.
They should be roughly equidistant in length.
If its not centered nearly perfectly, then you
are probably out of collimation....for starters.
Clear Skies,
Tom W.


Thanks Tom. I'll look at those tonight...
jojo




Ah, but I'm at work at the scope is at home.
I'll look at it on Saturday if daylight is better!
Thanks!
jojo

jon,
Thanks, That is a great reference!!!!

jojo

Don't thank me, thank Larry Gilstrap, he's the one who took the time to put
that page together.

Best wishes and enjoy your scope. Lots to see in a 4.5 inch Newtonian. If you
scope can take 1.25 inch eyepieces, you might want to consider getting a few
basic eyepieces to add to your collection, they should improve the views
considerably.

www.scopestuff.com has some nice deals.

Another thing to be aware of. Your scope is "rated" by the manufacturer at
675X. This is just a marketing ploy, scopes are not rated this way and it is
unreasonable to think that 675X would be anymore than a fuzzy mess. it would
be in most scopes the vast majority of the time.

The rule of thumb is 50 times the aperture in inches is the highest useable
magnification under the best circumstances. For your scope this works out to
about 220X.

Even with larger scopes, 10 inches and above, most viewing is done at under
200X.
So, 200X is more than enough, 120X and under will probably be where most of the
nice views are in this scope, plenty to see there.


Just a bit of a "heads up" to head of some possible frustration and
disappointment.

Again, best wishes on your new scope and enjoy the heck out of it.

jon

"Jon Isaacs" wrote in message
...
jon,
Thanks, That is a great reference!!!!

jojo

Don't thank me, thank Larry Gilstrap, he's the one who took the time to
put
that page together.

Best wishes and enjoy your scope. Lots to see in a 4.5 inch Newtonian.
If you
scope can take 1.25 inch eyepieces, you might want to consider getting a
few
basic eyepieces to add to your collection, they should improve the views
considerably.

www.scopestuff.com has some nice deals.

Another thing to be aware of. Your scope is "rated" by the manufacturer
at
675X. This is just a marketing ploy, scopes are not rated this way and it
is
unreasonable to think that 675X would be anymore than a fuzzy mess. it
would
be in most scopes the vast majority of the time.

The rule of thumb is 50 times the aperture in inches is the highest
useable
magnification under the best circumstances. For your scope this works out
to
about 220X.

Even with larger scopes, 10 inches and above, most viewing is done at
under
200X.
So, 200X is more than enough, 120X and under will probably be where most
of the
nice views are in this scope, plenty to see there.


Just a bit of a "heads up" to head of some possible frustration and
disappointment.

Again, best wishes on your new scope and enjoy the heck out of it.

jon


Thank jon,
Question,
50 times my aperture (4.5") give me the maximum reasonable magnification.
If I'm using a 12mm lens, what is the magnification? What is the math?
also, what part of the equation does the focal length play?

Thanks,
jojo

Thank jon,
Question,
50 times my aperture (4.5") give me the maximum reasonable magnification.
If I'm using a 12mm lens, what is the magnification? What is the math?
also, what part of the equation does the focal length play?

Thanks,
jojo

Magnification is the focal length of the telescope divided by the focal length
of the eyepiece.

With the 12mm the magnification is:

900mm/12mm= 75X

With the 20mm:

900mm/20mm= 45X

Both very reasonable. A 32 mm would provide you with a nice wide field of view
at abou 29X. A barlow is a good tool but i think that it is likely that you
would find that some basic plossl eyepieces would improve the view over your
current eyepieces.

jon

"Jon Isaacs" wrote in message
...
Thank jon,
Question,
50 times my aperture (4.5") give me the maximum reasonable magnification.
If I'm using a 12mm lens, what is the magnification? What is the math?
also, what part of the equation does the focal length play?

Thanks,
jojo

Magnification is the focal length of the telescope divided by the focal
length
of the eyepiece.

With the 12mm the magnification is:

900mm/12mm= 75X

With the 20mm:

900mm/20mm= 45X

Both very reasonable. A 32 mm would provide you with a nice wide field of
view
at abou 29X. A barlow is a good tool but i think that it is likely that
you
would find that some basic plossl eyepieces would improve the view over
your
current eyepieces.

jon

Thanks!

I find that I use the 12 mm the most often for moon and planets. The 4mm
just
seems to have too small a field.
I have never found anything in deep space such as other galaxies or nebulae.
Given my setup, what is the preferred lens for such deep space objects? To
be able to see the object
as clearly as possible with a decent field of view?

about the Barlow...say I wanted 150x magnification. what would allow me the
best field and light gathering,
a 12mm with a 2x Barlow or a 6mm lens (900mm focal length)?
as far as price goes the Barlow has much more usefulness and it can multiply
any
lens, but am I giving up quality of field using a Barlow (in this instance)
instead of a 6mm?

jojo

On 18 Sep 2003 04:33:32 GMT, lonk (Bill Foley) ...reflected:

Oh, jojo meant "collimate"??
Sorry for what I thought was meant...

Too late, I'm afraid, ol' boy.

On Thu, 18 Sep 2003 12:56:54 GMT, "jojo" ...reflected:


"jojo" wrote in message
.com...
how do I know if I need to culminating?



Sorry folks. A hasty post that spell check took over!
jojo

You were understood.

Alan