Viewing moon craters

Hello all, i received a telescope as a gift and am interested
in pursuing it further. It is F=900mm and D=114mm. We were
viewing the moon using a 12.5mm lens and got a good clear
shot. However, when trying to use the 4mm lens, it became
just a blur. Would 4mm be too powerful for viewing the moon?

I am a complete newbie, but according to the picture on
the box i should be able to focus in on individual craters.
Is this reasonable given the equipment that i have?

did you try refocusing?
It would be very sensitive and hard to focus.
Once you do actually focus it, the moon will move FAST with the 4mm
and the image will seem darker. Just not as bright white sharp as with the
12.5mm

jojo


"monkeys paw" wrote in message
news:92M7b.412547$uu5.75201@sccrnsc04...
Hello all, i received a telescope as a gift and am interested
in pursuing it further. It is F=900mm and D=114mm. We were
viewing the moon using a 12.5mm lens and got a good clear
shot. However, when trying to use the 4mm lens, it became
just a blur. Would 4mm be too powerful for viewing the moon?

I am a complete newbie, but according to the picture on
the box i should be able to focus in on individual craters.
Is this reasonable given the equipment that i have?

monkeys paw wrote in alt.astronomy:

Hello all, i received a telescope as a gift and am interested
in pursuing it further. It is F=900mm and D=114mm. We were
viewing the moon using a 12.5mm lens and got a good clear
shot. However, when trying to use the 4mm lens, it became
just a blur. Would 4mm be too powerful for viewing the moon?

I am a complete newbie, but according to the picture on
the box i should be able to focus in on individual craters.
Is this reasonable given the equipment that i have?


Rule of thumb is that maximum magnification is the diameter of the
mirror/objective (mm) times 1.5 - 2. In your case that means a
magnificatiin of about 150-200 max. After that images become blurred and
smeared out and air turbulence plays way to big a role to see something
detailed.

With a 4 mm eyepiece your _magnification_ is Focal lenght 900mm divided
by 4mm meaning 225x.
With high quality optics on both ends that might be possible, but with
medium or lower grade telescopes that is way too much. I think a maximum
magnification of 90 - 120 (so say a 10mm - 7.5 eyepiece) might be a
good rule of thumb in your case.

But don't be disappointed. There's so much more to see with low
magnifications- the objective of a telescope is not primarily to
_magnify_ but _gather light_. If you have enough of the foton stuff you
can magnify the image until it gets blurred, but you'd rather let it
stay sharp.

And your field of view stays bigger, enabling you to see deep sky
objects and star clusters big and small. Sometimes details are great,
but when you're starting with your hobby, try to keep it fun by actually
seeing and identifying everything possible, searching the skies for that
nebula you saw on your star chart.

Too many people leave astronomy as a hobby way too soon because of
overexpectations. Don't forget observing is not only setting up a scope,
but training your eyes as well.

After you've become infected for life you could decide to buy a bigger
and better scope.
Here's some good advice - even at this moment:
Telescope Buyers FAQ - http://home.inreach.com/starlord

Good luck, and enjoy your tour of exploration.

--
CeeBee


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


Google CeeBee @ www.geocities.com/ceebee_2

Telescope Buyers FAQ
http://home.inreach.com/starlord

You need to read this first.
That 4mm is way over powered for that scope. Plus you have to make sure
everything is in alinement too.


--
"In this universe the night was falling,the shadows were lengthening
towards an east that would not know another dawn.
But elsewhere the stars were still young and the light of morning
lingered: and along the path he once had followed, man would one day go
again."

Arthur C. Clarke, The City & The Stars

SIAR
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http://home.inreach.com/starlord

"monkeys paw" wrote in message
news:92M7b.412547$uu5.75201@sccrnsc04...
Hello all, i received a telescope as a gift and am interested
in pursuing it further. It is F=900mm and D=114mm. We were
viewing the moon using a 12.5mm lens and got a good clear
shot. However, when trying to use the 4mm lens, it became
just a blur. Would 4mm be too powerful for viewing the moon?

I am a complete newbie, but according to the picture on
the box i should be able to focus in on individual craters.
Is this reasonable given the equipment that i have?


---
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Thanks all, i'm reading the "introductory" material now

On 10 Sep 2003 23:33:41 GMT, CeeBee wrote:

monkeys paw wrote in alt.astronomy:

snip

And your field of view stays bigger, enabling you to see deep sky
objects and star clusters big and small. Sometimes details are great,
but when you're starting with your hobby, try to keep it fun by actually
seeing and identifying everything possible, searching the skies for that
nebula you saw on your star chart.

Even then you will find some deep sky objects are so large (and faint)
that you need to use a regular camera mounted "piggy back" on the
scope to see the whole thing.

As an example, the Andromeda Galaxy is so large (about 5 moon
diameters as I recall) that when the conditions are favorable for
"naked eye" viewing people often mistake if for a high cloud.

Yet I've been able to see it from the next to the university (SVSU)
observatory parking lot with the dorm parking lot lights in the back
ground. Yet I've never seen it from my own back yard which is
relatively dark.


Too many people leave astronomy as a hobby way too soon because of
overexpectations. Don't forget observing is not only setting up a scope,
but training your eyes as well.

And mind. learning the constellations, their histories and folk lore.
How to star hop from known stars to find deep sky objects. There are
a great many things to learn.

And good luck from me as well.

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)


After you've become infected for life you could decide to buy a bigger
and better scope.
Here's some good advice - even at this moment:
Telescope Buyers FAQ - http://home.inreach.com/starlord

Good luck, and enjoy your tour of exploration.

On 10 Sep 2003 23:33:41 GMT, CeeBee wrote:

monkeys paw wrote in alt.astronomy:

snip

And your field of view stays bigger, enabling you to see deep sky
objects and star clusters big and small. Sometimes details are great,
but when you're starting with your hobby, try to keep it fun by actually
seeing and identifying everything possible, searching the skies for that
nebula you saw on your star chart.

Even then you will find some deep sky objects are so large (and faint)
that you need to use a regular camera mounted "piggy back" on the
scope to see the whole thing.

As an example, the Andromeda Galaxy is so large (about 5 moon
diameters as I recall) that when the conditions are favorable for
"naked eye" viewing people often mistake if for a high cloud.

Yet I've been able to see it from the next to the university (SVSU)
observatory parking lot with the dorm parking lot lights in the back
ground. Yet I've never seen it from my own back yard which is
relatively dark.


Too many people leave astronomy as a hobby way too soon because of
overexpectations. Don't forget observing is not only setting up a scope,
but training your eyes as well.

And mind. learning the constellations, their histories and folk lore.
How to star hop from known stars to find deep sky objects. There are
a great many things to learn.

And good luck from me as well.

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)


After you've become infected for life you could decide to buy a bigger
and better scope.
Here's some good advice - even at this moment:
Telescope Buyers FAQ - http://home.inreach.com/starlord

Good luck, and enjoy your tour of exploration.