Help with orthogonality


Roland Christen
 

In a message dated 4/24/2007 1:01:09 PM Central Daylight Time,
lmarchesi@yahoo.com writes:


I had some significant time with my new mount (AP 1200) and the new
camera this past weekend (finally!). One thing that is more
challenging than I expected is polar alignment. I did the 'daytime
polar alignment' routine using a carpenter's level and the Moon. The
mount/pier were reasonably level as well. Then, when I do the 2-star
calibration I seem to be 'oscillating' back and forth in azimuth.
There is always some confusion as to what this 2 Star thing is supposed to
do. It is not a calibration routine. It does not calibrate anything in the
mount. It is simply one more of dozens of polar alignment routine options. This one
in particular can be hard to converge, especially if you happen to choose the
wrong two stars. As such, this polar alignment option is probably the weakest
of all. You should never conclude from this alignment routine that something
is amiss with your orthogonality. In fact, I am tempted to eliminate this
routine because of the confusion it seems to cause everyone who first uses this
mount after using other commercial Alt-Az mountings.

The best way to judge the orthogonality of your setup is to GoTo the same
star on both sides of the meridian. Choose a star near the zenith, then center it
on your crosshairs. Note the RA direction. Then choose the meridian delay
feature (1 hour delay either E or W) of the keypad to GoTo this same exact star
again on the other side of the mount. Note where the star ends up versus the RA
crosshair. Now you can see your orthogonality error - the error is exactly
1/2 of the distance from the crosshair and where your star ended up. Now you can
also see how much to shim the mounting ring, either front or back) to bring
the star 1/2 way to the crosshair. Once you have shimmed it, you can go back
and forth to the same star on either side of the meridian to do a final tweaking
if desired.

The other thing I want to point out is that with a normal refractor and
normally well machined rings, you will never have any orthogonal errors that are
too large. You should have very close GoTo accuracy if you are properly polar
aligned. If you do not wat to do accurate polar alignment, you can still do
precision GoTo by first picking a bright star in the area that you want to
observe, center it, press Rcal and then enter the faint object you wish to observe
and press GoTo. This way you can always find any object in your telescope field,
even if not polar aligned.

Rolando


**************************************
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Roland Christen
 

In a message dated 4/24/2007 4:35:40 PM Central Daylight Time,
drichey@sandia.net writes:


I beleive it is .8º for CNP. So how does one do the alignment
routine in the AP manual using Polaris and another star?
The mount can certainly go to Polaris. No problem. When properly polar
aligned, any mount can go to Polaris. If you have orthogonal error larger than 0.8
degrees in your telescope, then no equatorial mount will be able to access
Polaris. The mount will point to Polaris for sure, but the scope will point
elsewhere. I assume that every amateur knows that the direction that a telescope
points to is not necessarily the direction that the mount points to. It is up to
you, the user, to align the two. Every basic book on astronomical instruments
will point this out.

Rolando


**************************************
See what's free at
http://www.aol.com.


[Non-text portions of this message have been removed]


primeclash
 

I had some significant time with my new mount (AP 1200) and the new
camera this past weekend (finally!). One thing that is more
challenging than I expected is polar alignment. I did the 'daytime
polar alignment' routine using a carpenter's level and the Moon. The
mount/pier were reasonably level as well. Then, when I do the 2-star
calibration I seem to be 'oscillating' back and forth in azimuth.

What surprised me most is that the 'cone of error' seems very large,
as in half a finder scope's field of view. I am not sure how much of
that is how far I am from the pole versus non-orthogonality, but it
does make pointing the scope and camera at a specific target somewhat
challenging.

I have a 6-inch refractor with (IIRC) CNC-machined rings on a Losmandy
17-inch dovetail with 'riser' blocks, then attached to a Casady saddle
on the 1200.

In the manual for the mount, it says to 'simply shim' the rings until
I am orthogonal. I apologize for being dense, but does the shimming
happen to the contact point where the rings mate to the dovetail
plate, or where the dovetail mates to the saddle, or both? What is a
good shimming material ... soda can, 'aluminum' foil? One other thing
I should mention is that I don't yet have a permanent setup, so I'd
like a solution that is repeatable each time I set up.

I recognize that there is software out there to model pointing, but
I'm the kind of person that will be 'bothered' by this. I'd rather get
the scope as orthogonal as possible before I consider T-Point or its
equivalent.

Regards,
Louis Marchesi
New London Twp, PA


spcrichey <drichey@...>
 

I have exactly the same problem, only an AP900. I use a 6" TV refractor with a Robin
Casady saddle and Parallax rings (rings and saddle new). Spent significant time on star
drift alignment, got it perfect for 5 minutes both S and E. My finds are still off. I guess I
also have an orthogonality issue. Am waiting for weather to try the AP Ortho check
routine.
Should one be able to center Polaris in a guiding EP at 60 power. After the alignment (drift
method) I cannot.
Regards,
Dan Richey

--- In ap-gto@yahoogroups.com, "Louis Marchesi" <lmarchesi@...> wrote:

I had some significant time with my new mount (AP 1200) and the new
camera this past weekend (finally!). One thing that is more
challenging than I expected is polar alignment. I did the 'daytime
polar alignment' routine using a carpenter's level and the Moon. The
mount/pier were reasonably level as well. Then, when I do the 2-star
calibration I seem to be 'oscillating' back and forth in azimuth.

What surprised me most is that the 'cone of error' seems very large,
as in half a finder scope's field of view. I am not sure how much of
that is how far I am from the pole versus non-orthogonality, but it
does make pointing the scope and camera at a specific target somewhat
challenging.

I have a 6-inch refractor with (IIRC) CNC-machined rings on a Losmandy
17-inch dovetail with 'riser' blocks, then attached to a Casady saddle
on the 1200.

In the manual for the mount, it says to 'simply shim' the rings until
I am orthogonal. I apologize for being dense, but does the shimming
happen to the contact point where the rings mate to the dovetail
plate, or where the dovetail mates to the saddle, or both? What is a
good shimming material ... soda can, 'aluminum' foil? One other thing
I should mention is that I don't yet have a permanent setup, so I'd
like a solution that is repeatable each time I set up.

I recognize that there is software out there to model pointing, but
I'm the kind of person that will be 'bothered' by this. I'd rather get
the scope as orthogonal as possible before I consider T-Point or its
equivalent.

Regards,
Louis Marchesi
New London Twp, PA


Roland Christen
 

In a message dated 4/24/2007 7:48:26 PM Central Daylight Time,
mphammick@yahoo.com writes:


Taking your point one stage further, there is a potentially flawed
assumption that anything bolted to a mount is pointing in the right direction and
indeed that any series of things bolted to a mount are pointing in the same
direction.

Equipment-alignment and polar-alignment are two very different things which
are both important.
You are correct.

Rolando


**************************************
See what's free at
http://www.aol.com.


observe_m13
 

Uh, no you should not be able to center Polaris. Polaris is not at the
pole, it is beside it.

Rick.

--- In ap-gto@yahoogroups.com, "spcrichey" <drichey@...> wrote:

I have exactly the same problem, only an AP900. I use a 6" TV
refractor with a Robin
Casady saddle and Parallax rings (rings and saddle new). Spent
significant time on star
drift alignment, got it perfect for 5 minutes both S and E. My
finds are still off. I guess I
also have an orthogonality issue. Am waiting for weather to try the
AP Ortho check
routine.
Should one be able to center Polaris in a guiding EP at 60 power.
After the alignment (drift
method) I cannot.
Regards,
Dan Richey
--- In ap-gto@yahoogroups.com, "Louis Marchesi" <lmarchesi@> wrote:

I had some significant time with my new mount (AP 1200) and the new
camera this past weekend (finally!). One thing that is more
challenging than I expected is polar alignment. I did the 'daytime
polar alignment' routine using a carpenter's level and the Moon. The
mount/pier were reasonably level as well. Then, when I do the 2-star
calibration I seem to be 'oscillating' back and forth in azimuth.

What surprised me most is that the 'cone of error' seems very large,
as in half a finder scope's field of view. I am not sure how much of
that is how far I am from the pole versus non-orthogonality, but it
does make pointing the scope and camera at a specific target somewhat
challenging.

I have a 6-inch refractor with (IIRC) CNC-machined rings on a Losmandy
17-inch dovetail with 'riser' blocks, then attached to a Casady saddle
on the 1200.

In the manual for the mount, it says to 'simply shim' the rings until
I am orthogonal. I apologize for being dense, but does the shimming
happen to the contact point where the rings mate to the dovetail
plate, or where the dovetail mates to the saddle, or both? What is a
good shimming material ... soda can, 'aluminum' foil? One other thing
I should mention is that I don't yet have a permanent setup, so I'd
like a solution that is repeatable each time I set up.

I recognize that there is software out there to model pointing, but
I'm the kind of person that will be 'bothered' by this. I'd rather get
the scope as orthogonal as possible before I consider T-Point or its
equivalent.

Regards,
Louis Marchesi
New London Twp, PA


spcrichey <drichey@...>
 

That's what I thought. I beleive it is .8º for CNP. So how does one do the alignment
routine in the AP manual using Polaris and another star?--- In ap-gto@yahoogroups.com,
"Rick K" <JunkMailGoesHere@...> wrote:


Uh, no you should not be able to center Polaris. Polaris is not at the
pole, it is beside it.

Rick.

--- In ap-gto@yahoogroups.com, "spcrichey" <drichey@> wrote:

I have exactly the same problem, only an AP900. I use a 6" TV
refractor with a Robin
Casady saddle and Parallax rings (rings and saddle new). Spent
significant time on star
drift alignment, got it perfect for 5 minutes both S and E. My
finds are still off. I guess I
also have an orthogonality issue. Am waiting for weather to try the
AP Ortho check
routine.
Should one be able to center Polaris in a guiding EP at 60 power.
After the alignment (drift
method) I cannot.
Regards,
Dan Richey
--- In ap-gto@yahoogroups.com, "Louis Marchesi" <lmarchesi@> wrote:

I had some significant time with my new mount (AP 1200) and the new
camera this past weekend (finally!). One thing that is more
challenging than I expected is polar alignment. I did the 'daytime
polar alignment' routine using a carpenter's level and the Moon. The
mount/pier were reasonably level as well. Then, when I do the 2-star
calibration I seem to be 'oscillating' back and forth in azimuth.

What surprised me most is that the 'cone of error' seems very large,
as in half a finder scope's field of view. I am not sure how much of
that is how far I am from the pole versus non-orthogonality, but it
does make pointing the scope and camera at a specific target somewhat
challenging.

I have a 6-inch refractor with (IIRC) CNC-machined rings on a Losmandy
17-inch dovetail with 'riser' blocks, then attached to a Casady saddle
on the 1200.

In the manual for the mount, it says to 'simply shim' the rings until
I am orthogonal. I apologize for being dense, but does the shimming
happen to the contact point where the rings mate to the dovetail
plate, or where the dovetail mates to the saddle, or both? What is a
good shimming material ... soda can, 'aluminum' foil? One other thing
I should mention is that I don't yet have a permanent setup, so I'd
like a solution that is repeatable each time I set up.

I recognize that there is software out there to model pointing, but
I'm the kind of person that will be 'bothered' by this. I'd rather get
the scope as orthogonal as possible before I consider T-Point or its
equivalent.

Regards,
Louis Marchesi
New London Twp, PA


Woodwind
 

Rolando,

You have put your finger on a phenomenon which so often seems to afflict us all at one time or another. Flawed leaps of logic - which can leave one totally bewildered by our inability to achieve an aim - and no apparent solution until someone points out the obvious.

Taking your point one stage further, there is a potentially flawed assumption that anything bolted to a mount is pointing in the right direction and indeed that any series of things bolted to a mount are pointing in the same direction.

Equipment-alignment and polar-alignment are two very different things which are both important.

Just a thought.

Murray







chris1011@aol.com wrote: In a message dated 4/24/2007 4:35:40 PM Central Daylight Time,
drichey@sandia.net writes:

> I beleive it is .8º for CNP. So how does one do the alignment
> routine in the AP manual using Polaris and another star?

The mount can certainly go to Polaris. No problem. When properly polar
aligned, any mount can go to Polaris. If you have orthogonal error larger than 0.8
degrees in your telescope, then no equatorial mount will be able to access
Polaris. The mount will point to Polaris for sure, but the scope will point
elsewhere. I assume that every amateur knows that the direction that a telescope
points to is not necessarily the direction that the mount points to. It is up to
you, the user, to align the two. Every basic book on astronomical instruments
will point this out.

Rolando

**************************************
See what's free at
http://www.aol.com.

[Non-text portions of this message have been removed]






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[Non-text portions of this message have been removed]


spcrichey <drichey@...>
 

So, one person says "Uh, no you should not be able to center Polaris, Polaris is not at the
pole, it is beside it." , and another says "the mount can certainly go to Polaris." I am very
confused. Is not being able to center Polaris an orthogonal error, or not? I have a "normal"
refractor and "normally well" machined rings, so either I am not well enough polar aligned,
or my equipment isn't "normal." --- In ap-gto@yahoogroups.com, chris1011@... wrote:


In a message dated 4/24/2007 4:35:40 PM Central Daylight Time,
drichey@... writes:


I beleive it is .8º for CNP. So how does one do the alignment
routine in the AP manual using Polaris and another star?
The mount can certainly go to Polaris. No problem. When properly polar
aligned, any mount can go to Polaris. If you have orthogonal error larger than 0.8
degrees in your telescope, then no equatorial mount will be able to access
Polaris. The mount will point to Polaris for sure, but the scope will point
elsewhere. I assume that every amateur knows that the direction that a telescope
points to is not necessarily the direction that the mount points to. It is up to
you, the user, to align the two. Every basic book on astronomical instruments
will point this out.

Rolando


**************************************
See what's free at
http://www.aol.com.


[Non-text portions of this message have been removed]


observe_m13
 

If your telescope is orthogonal to the mount and the mount is even
moderately well polar aligned, when you point the telescope right at
the pole, Polaris will NOT be centered. It will be noticeably offset
even in a low power eyepiece field. Polaris can be used as a quick
alignment star for visual use of a moderately wide field telescope
with goto in most cases.

To rough polar align I use the PASILL with great success. In fact,
with a bit of care, I manage to achieve very good to excellent polar
alignment. One can drift after that to fine tune it further if
shooting close to the poles where field rotation really makes a mess
of things if you are not well polar aligned.

Rick.

--- In ap-gto@yahoogroups.com, "spcrichey" <drichey@...> wrote:

So, one person says "Uh, no you should not be able to center
Polaris, Polaris is not at the
pole, it is beside it." , and another says "the mount can certainly
go to Polaris." I am very
confused. Is not being able to center Polaris an orthogonal error,
or not? I have a "normal"
refractor and "normally well" machined rings, so either I am not
well enough polar aligned,
or my equipment isn't "normal." --- In ap-gto@yahoogroups.com,
chris1011@ wrote:

In a message dated 4/24/2007 4:35:40 PM Central Daylight Time,
drichey@ writes:


I beleive it is .8º for CNP. So how does one do the alignment
routine in the AP manual using Polaris and another star?
The mount can certainly go to Polaris. No problem. When properly
polar
aligned, any mount can go to Polaris. If you have orthogonal error
larger than 0.8
degrees in your telescope, then no equatorial mount will be able
to access
Polaris. The mount will point to Polaris for sure, but the scope
will point
elsewhere. I assume that every amateur knows that the direction
that a telescope
points to is not necessarily the direction that the mount points
to. It is up to
you, the user, to align the two. Every basic book on astronomical
instruments
will point this out.

Rolando


**************************************
See what's free at
http://www.aol.com.


[Non-text portions of this message have been removed]


primeclash
 

--- In ap-gto@yahoogroups.com, chris1011@... wrote:
There is always some confusion as to what this 2 Star thing is
supposed to
do. It is not a calibration routine. It does not calibrate anything
in the
mount. It is simply one more of dozens of polar alignment routine
options. This one
in particular can be hard to converge, especially if you happen to
choose the
wrong two stars. As such, this polar alignment option is probably
the weakest
of all. You should never conclude from this alignment routine that
something
is amiss with your orthogonality. In fact, I am tempted to eliminate
this
routine because of the confusion it seems to cause everyone who
first uses this
mount after using other commercial Alt-Az mountings.
Noted. I should have followed your preferred methodology you outlined
in message 17688. I would have sworn it included the '2-star
calibration' but it does not. I started using the 'carpenter's level'
technique but then referred to the manual. I'm ripping that page out
tonight after I get home from work ;-)

Thanks for the help,
Louis Marchesi
New London Twp, PA


Auchter Tom-W11806
 

We are mixing pointing at the pole and pointing at Polaris. If the
mount is polar aligned and the telescope is orthogonal then you can do
the following. When you point the telescope at the pole ie 90 degrees
Polaris will not be centered. If you tell the mount to goto Polaris
then Polaris will be centered. I have done it many times.

Tom