How do I - Direction through the Eyepiece.

I have a Celestron C9 1/4 with 90 degree Star Diagonal on it. I have
no problem star hopping using my Telrad or my Finder Scope (where
EVERYTHING is upside down and backwards), but I'm having a rough time
orieinting myself through the eyepiece. The problem is that the
orientation changes every time you rotate the star diagonal (which I
do often to find a more comfortable viewing position). Combine that
with the fact that the FOV is bloody small (a hair under 1 degree
with widest eyepiece), and I have a hard time orienting myself. Now,
that doesn't affect the views at all, but I find that I'd like some
references when I go to sketch (OK, OK, make a really poor rendition)
an object.

Now, I've thought, "Hey, the DEC motor runs only towards and away
from the north star and the RA motor runs only parallel to it, maybe
I could use these to orient myself..."

Should that work? Are there any ways to figure it all out?

Thanks.

Clear, Dark Skies

Mark

Mark Smith wrote, in part:
Now, I've thought, "Hey, the DEC motor runs only towards and away
from the north star and the RA motor runs only parallel to it, maybe
I could use these to orient myself..."

Should that work? Are there any ways to figure it all out?

Yes, that will work. New sky will enter field in the direction toward which
you're moving the telescope. So, if you slew east, new sky enters from the
east. If you slew north, new sky enters from the north.

I usually slew east in my Newt, select a reference star or asterism near the
edge of the field and use that to maintain orientation during the observation.

This should work for you and your rotating star diagonal. Once you've found a
reference star that lets you know where east--or some direction--is, that's
your marker in whichever orientation you place the diagonal.

Regards,

Bill Ferris
"Cosmic Voyage: The Online Resource for Amateur Astronomers"
URL: http://www.cosmic-voyage.net
=============
Email: Remove "ic" from .comic above to respond

On Fri, 23 Jul 2004 01:10:32 -0500, Mark Smith wrote
(in article ):

I have a Celestron C9 1/4 with 90 degree Star Diagonal on it. I have
no problem star hopping using my Telrad or my Finder Scope (where
EVERYTHING is upside down and backwards), but I'm having a rough time
orieinting myself through the eyepiece. The problem is that the
orientation changes every time you rotate the star diagonal (which I
do often to find a more comfortable viewing position). Combine that
with the fact that the FOV is bloody small (a hair under 1 degree
with widest eyepiece), and I have a hard time orienting myself. Now,
that doesn't affect the views at all, but I find that I'd like some
references when I go to sketch (OK, OK, make a really poor rendition)
an object.

Now, I've thought, "Hey, the DEC motor runs only towards and away
from the north star and the RA motor runs only parallel to it, maybe
I could use these to orient myself..."

Should that work? Are there any ways to figure it all out?

Thanks.

Clear, Dark Skies

Mark


First off, you need to remember that your image through the scope is
mirror-reversed (left and right swapped).

Your are correct about using your Dec and RA motions. There are at least two
ways you can proceed:

1. Hit the North button on your hand paddle. Stars will enter from the North
direction in your field of view. East will be 90 degrees clockwise from that
(because of the mirror image). This is the same orientation as a land map.
In the sky naked eye, East is 90 degrees counterclockwise from North.

2. Turn off your drive and watch the stars drift across the FOV. Stars will
enter from the East and exit from the West. North will then be 90 degrees
counterclockwise from East.

The second procedure will work for any scope (equatorial or not). You just
need to know if your image is mirror reversed or not.

Mark Smith wrote in message . ..

The problem is that the
orientation changes every time you rotate the star diagonal (which I
do often to find a more comfortable viewing position). Combine that
with the fact that the FOV is bloody small (a hair under 1 degree
with widest eyepiece), and I have a hard time orienting myself.

Me too! There's basically three ways to approach this. First, make
a point of observing only objects near the meridian, and make a
point of keeping the diagonal straight up. That makes north up
in your scope.

Second, orient yourself w.r.t. what you see in the field. That
requires having charts that show numerous stars in every FOV.
With your narrow FOV, that will require hand-generating charts
with computer software; even the Millenium Star Atlas doesn't
show that many stars.

Third, orient yourself by thinking about how the tube moves w.r.t.
the ground and the sky. This is, ironically, hard or impossible with
a Go To drive -- which is supposed to make things easy -- and easiest
with a completely hand-controlled scope. But if your scope is mounted
in equatorial mode, it's pretty easy to figure things out by twitching
the Dec control and seeing what happens in the eyepiece as the scope
moves N.

Another very common trick is to turn off the motor drive and watch
which way the stars drift. Stars appear on the E side of the field
and disappear on the W, moving precisely E to W as they go.

I'm afraid I can't help you with the fact that the star diagonal
mirror-reverses things; that continues to confuse me after years
of practice. In fact, it's one of the main reasons that I prefer
Newtonians to refractors and catadioptrics.

- Tony Flanders

If the scope is equatorially mounted, you can use the method you describe.
That's what I do. I move the scope north and then I know where everything
else is (remember that it is a mirror image).

I wrote this article on the various views found in the eyepiece:
http://www.mindspring.com/~jeffpo/whichway.htm

Jeff
http://www.mindspring.com/~jeffpo



"Mark Smith" wrote in message
...
I have a Celestron C9 1/4 with 90 degree Star Diagonal on it. I have
no problem star hopping using my Telrad or my Finder Scope (where
EVERYTHING is upside down and backwards), but I'm having a rough time
orieinting myself through the eyepiece. The problem is that the
orientation changes every time you rotate the star diagonal (which I
do often to find a more comfortable viewing position). Combine that
with the fact that the FOV is bloody small (a hair under 1 degree
with widest eyepiece), and I have a hard time orienting myself. Now,
that doesn't affect the views at all, but I find that I'd like some
references when I go to sketch (OK, OK, make a really poor rendition)
an object.

Now, I've thought, "Hey, the DEC motor runs only towards and away
from the north star and the RA motor runs only parallel to it, maybe
I could use these to orient myself..."

Should that work? Are there any ways to figure it all out?

Thanks.

Clear, Dark Skies

Mark

On Fri, 23 Jul 2004 14:17:01 GMT, Bill Tschumy
wrote:



First off, you need to remember that your image through the scope is
mirror-reversed (left and right swapped).


Hmmm...OK. I know this (I've read it 1000 times), but I guess I'm
having a problem with it intuitively. I have no problem when using
the spotter scope because the orientation ALWAYS remains the same.
North and South are reversed as are East and West.

With the star diagonal, the image "rotates" when I rotate the
diagonal. Now, this makes sense to me, but I've never really thought
of what it means with the light paths. Let me walk through this and
tell me if I got it.

If N is up in the eyepiece, S is down, E is left, and W is right.

N
E W
S

Now, if I rotate 90 degrees so E is up and W is down, N and S will be
reversed and it will look like this.

E
S N
W

Now, what had never jumped out and clubbed me before is that the two
above are exactly the same. Since the image rotated, I somehow got it
in my head that strange things were happening, but they really aren't,
are they? The relation of the cardinal directions are still exactly
the same, just rotated 90 degrees.

Is this making sense? Is it even close to correct?

As always, thank you very much for your help.

Clear, Dark Skies

Mark

I have a Celestron C9 1/4 with 90 degree Star Diagonal on it.
I'm having a rough time
orieinting myself through the eyepiece. The problem is that the
orientation changes every time you rotate the star diagonal (which I
do often to find a more comfortable viewing position). Combine that
with the fact that the FOV is bloody small (a hair under 1 degree
with widest eyepiece), and I have a hard time orienting myself.
Now, I've thought, "Hey, the DEC motor runs only towards and away
from the north star and the RA motor runs only parallel to it, maybe
I could use these to orient myself..."
Should that work? Are there any ways to figure it all out?

while looking thru the eyepiece, release the tracking lock and tweak the manual
DEC controls to confirm your orientation. 'up' or 'toward the pole star' is
always north. manually turning the RA control clockwise always takes you west.
also, practice starhopping thru the eyepiece without the tracking lock.
a 1-degree FOV works well.
for example: M28 lies about half a 'field' north and half a 'field' west of
lambda sagittarius.

SaberStar
P.A.C.
Astronomical League

On Fri, 23 Jul 2004 10:37:44 -0500, Mark Smith wrote
(in article ):

On Fri, 23 Jul 2004 14:17:01 GMT, Bill Tschumy
wrote:



First off, you need to remember that your image through the scope is
mirror-reversed (left and right swapped).


Hmmm...OK. I know this (I've read it 1000 times), but I guess I'm
having a problem with it intuitively. I have no problem when using
the spotter scope because the orientation ALWAYS remains the same.
North and South are reversed as are East and West.

With the star diagonal, the image "rotates" when I rotate the
diagonal. Now, this makes sense to me, but I've never really thought
of what it means with the light paths. Let me walk through this and
tell me if I got it.

The image does rotate, but this doesn't have any effect on the reversal


If N is up in the eyepiece, S is down, E is left, and W is right.

N
E W
S

No, that is the naked eye (or Newtonian) orientation. With a star diagonal
(an odd number of reflections) You will get:

N
W E
S

Think of standing, looking south at Sagittarius. North will be up (and
behind you). East is to the left and West to the right. With a diagonal
oriented straight up this is flipped so West is to the left and East to the
right (just like a land map).


Now, if I rotate 90 degrees so E is up and W is down, N and S will be
reversed and it will look like this.

Everything will just rotate clockwise or counterclockwise as you rotate the
diagonal. Like:


W
S N
E


E
S N
W

Now, what had never jumped out and clubbed me before is that the two
above are exactly the same. Since the image rotated, I somehow got it
in my head that strange things were happening, but they really aren't,
are they? The relation of the cardinal directions are still exactly
the same, just rotated 90 degrees.

You got it!


Is this making sense? Is it even close to correct?


You are right except you got the initial orientation reversed above.


As always, thank you very much for your help.

Clear, Dark Skies

Mark

OK. Now I'm completely confused. Read below:

On Fri, 23 Jul 2004 10:37:44 -0500, Mark Smith wrote
(in article ):

On Fri, 23 Jul 2004 14:17:01 GMT, Bill Tschumy
wrote:



First off, you need to remember that your image through the scope is
mirror-reversed (left and right swapped).


Hmmm...OK. I know this (I've read it 1000 times), but I guess I'm
having a problem with it intuitively. I have no problem when using
the spotter scope because the orientation ALWAYS remains the same.
North and South are reversed as are East and West.

With the star diagonal, the image "rotates" when I rotate the
diagonal. Now, this makes sense to me, but I've never really thought
of what it means with the light paths. Let me walk through this and
tell me if I got it.

The image does rotate, but this doesn't have any effect on the reversal


If N is up in the eyepiece, S is down, E is left, and W is right.

N
E W
S

No, that is the naked eye (or Newtonian) orientation. With a star diagonal
(an odd number of reflections) You will get:

N
W E
S

Think of standing, looking south at Sagittarius. North will be up (and
behind you). East is to the left and West to the right. With a diagonal
oriented straight up this is flipped so West is to the left and East to the
right (just like a land map).

OK. Here is where I'm confused. Your description seems to match my
diagram.

If I'm standing in the center of your diagram facing the S, N is
behind me (as it should be), the E is over my left shoulder (as is
Arizona (I live in southern California), and the W is over my right
shoulder (as is the Pacific).

Now, still standing in the center of the figure, if I orient the star
diagonal so that the S is in the center of the eyepiece, the N would
be off the top in a line directly over my head. Physically, the W is
still over my right shoulder, but it should appear that it is over my
left shoulder in the eyepiece (like in my figure), right?

And aren't land maps correct (I sure hope so or all my orienteering
goes out the window!)? If I put the map on the ground with the north
edge of the map closest to the North Pole and face south (standing on
the north side of the map), the W edge of the map is on my right and
the E edge is on my left (ie, the edges of the map are in the correct
cardinal positions).

Based on the below, I think I'm almost there...




Now, if I rotate 90 degrees so E is up and W is down, N and S will be
reversed and it will look like this.

Everything will just rotate clockwise or counterclockwise as you rotate the
diagonal. Like:


W
S N
E


E
S N
W

Now, what had never jumped out and clubbed me before is that the two
above are exactly the same. Since the image rotated, I somehow got it
in my head that strange things were happening, but they really aren't,
are they? The relation of the cardinal directions are still exactly
the same, just rotated 90 degrees.

You got it!


Is this making sense? Is it even close to correct?


You are right except you got the initial orientation reversed above.


As always, thank you very much for your help.

Clear, Dark Skies

Mark

On Fri, 23 Jul 2004 17:21:44 -0500, Mark Smith wrote
(in article ):

OK. Now I'm completely confused. Read below:

On Fri, 23 Jul 2004 10:37:44 -0500, Mark Smith wrote
(in article ):

On Fri, 23 Jul 2004 14:17:01 GMT, Bill Tschumy
wrote:



First off, you need to remember that your image through the scope is
mirror-reversed (left and right swapped).


Hmmm...OK. I know this (I've read it 1000 times), but I guess I'm
having a problem with it intuitively. I have no problem when using
the spotter scope because the orientation ALWAYS remains the same.
North and South are reversed as are East and West.

With the star diagonal, the image "rotates" when I rotate the
diagonal. Now, this makes sense to me, but I've never really thought
of what it means with the light paths. Let me walk through this and
tell me if I got it.

The image does rotate, but this doesn't have any effect on the reversal


If N is up in the eyepiece, S is down, E is left, and W is right.

N
E W
S

No, that is the naked eye (or Newtonian) orientation. With a star diagonal
(an odd number of reflections) You will get:

N
W E
S

Think of standing, looking south at Sagittarius. North will be up (and
behind you). East is to the left and West to the right. With a diagonal
oriented straight up this is flipped so West is to the left and East to the
right (just like a land map).

OK. Here is where I'm confused. Your description seems to match my
diagram.

If I'm standing in the center of your diagram facing the S, N is
behind me (as it should be), the E is over my left shoulder (as is
Arizona (I live in southern California), and the W is over my right
shoulder (as is the Pacific).

Now, still standing in the center of the figure, if I orient the star
diagonal so that the S is in the center of the eyepiece, the N would
be off the top in a line directly over my head. Physically, the W is
still over my right shoulder, but it should appear that it is over my
left shoulder in the eyepiece (like in my figure), right?

Not exactly sure what you mean when you say S is in the "center" of the
eyepiece. It will be at the bottom and N at the top.

Your figure (the upper one above) shows W to the right. Your paragraph just
said it is to the left in the eyepiece (and that is correct). I'm not sure
how you are visualizing it so as to have this confusion.

I won't discount the possibility that I'm the one that's confused. If any
else thinks so also please let me know.


And aren't land maps correct (I sure hope so or all my orienteering
goes out the window!)? If I put the map on the ground with the north
edge of the map closest to the North Pole and face south (standing on
the north side of the map), the W edge of the map is on my right and
the E edge is on my left (ie, the edges of the map are in the correct
cardinal positions).

Based on the below, I think I'm almost there...




Now, if I rotate 90 degrees so E is up and W is down, N and S will be
reversed and it will look like this.

Everything will just rotate clockwise or counterclockwise as you rotate the
diagonal. Like:


W
S N
E


E
S N
W

Now, what had never jumped out and clubbed me before is that the two
above are exactly the same. Since the image rotated, I somehow got it
in my head that strange things were happening, but they really aren't,
are they? The relation of the cardinal directions are still exactly
the same, just rotated 90 degrees.

You got it!


Is this making sense? Is it even close to correct?


You are right except you got the initial orientation reversed above.


As always, thank you very much for your help.

Clear, Dark Skies

Mark