Mach1 and checking PASILL4 results


Pierre Henrotay
 

Hello all,

I am running a Mach1 and experience some problems with my polar
alignment scope (PASILL4). I'd appreciate your ideas here.

My goal is to use for alignment the PASILL4 only and reach a polar
alignment within 5 arcmin at worst, hopefully 2 arcmin.
As far as I heard the PASILL4 is very capable of this.

The very few clear nights we just had here (I live 50°N, 5° E)
allowed me to make some tests.

I spent a long time to:
- center the reticle in day light
this looks OK: centering an object and rotating the housing does not
show a significant displacement of the target object wrt to the
centre of the reticle
- make the scope orthogonal (indeed makes a big difference when
gotoing, definitely worth the effort !)
- train PEM (impressive low error, great !) using PemPro; PEM is
active

There is a very (very very) tiny amount of play when the polar scope
is tightly screwed in the polar axis. Not expecting this to be a
problem.

Last night I did a polar alignment using first the polar scope for
rough alignment, then I used PoleAlignMax (I am familiar with this
and checked in the past that I have consistent results with PemPro);
resulting alignment error was under 1 arcminute in both directions.

I verified that goto was accurate and I took 4x4 min unguided
exposures of M51 that show no significant drift (resolution: 2
arcsec/pixel). Excellent alignment thus.

Then I checked what PASILL4 was showing; the 3 reference stars were
visible (of of them barely as expected) but obviously
when rotating the polar scope, the best match showed Polaris
approximately with a perpendicular offset from its gap:
it was near the base of the engraved arrow head pointing at the gap
where Polaris should be.
Or, expressed differently, when rotating the polar scope to bring
Polaris in its gap,
the two other stars were far from their radial lines (30 degrees or
so for delta UMi).

I then redid a polar aligment just carefully using the PASILL4.
Then rerun PoleAlignMax to derive how big the misalignment was.
The result: a bit more than 10 arcminutes both in azimuth and in
altitude, so clearly way beyond my expectations.
And too big to be explained by refraction effects.
I took a series of images of M51 again (4x4minutes unguided) and
indeed there was an evident drift.

This morning I rechecked the optical centering of the reticle: it is
still OK, nothing changed.

One thing I thought of was that the polarscope might be not aligned
within the axis once screwed in but I would be very very surprising.
Is there a way to check this ?
Maybe I am doing wrong or assuming something incorrectly but I
cannot see what is the trouble. I'd welcome your ideas and hints.
The mount is properly balanced, the telescope is rigidly attached,
the imaging combo is not very heavy (NP127 + DSLR).

Regards,
Pierre


Kent Kirkley
 

In a message dated 4/13/08 11:03:21 AM, JunkMailGoesHere@... writes:


If they are not on the
original point of aim, then the housing with relation to the polar
scope itself will require adjustment and since I don't have any
information here I can't tell you how to go about doing that. Maybe
there is something in the PAS manual.
This can be adjusted by carefully moving the reticle.
This is done my loosening and tightening the three small screws that hold the
reticle in place.
They are found around the barrel foreward of the eyepiece.

WARNING!!!
Be very careful when loosening and tightening as too much pressure can crack
the reticle.

Kent Kirkley




**************
It's Tax Time! Get tips, forms and advice on AOL Money &
Finance.
(http://money.aol.com/tax?NCID=aolcmp00300000002850)


Joe Zeglinski
 

Hi Pierre,

Well done analysis.
Just a basic question though. You noted the position of Polaris was still
offset at the bottom of it's arrow marked gap.
Is there any possibility of a mistake, and you have a Passil3 scope, or the wrong reticle was
put in? Double check that you have positions good until 2030 (reticle engraved with N-05-10-20-30).

Joe


Pierre Henrotay
 

Hi Joe,

It has the engravings till 2030 (N-05-10-20-30).

Pierre

--- In ap-gto@..., "Joseph Zeglinski" <J.Zeglinski@...>
wrote:

Hi Pierre,

Well done analysis.
Just a basic question though. You noted the position of Polaris was
still
offset at the bottom of it's arrow marked gap.
Is there any possibility of a mistake, and you have a Passil3 scope,
or the
wrong reticle was
put in? Double check that you have positions good until 2030 (reticle
engraved with N-05-10-20-30).

Joe


Pierre Henrotay
 

I just put in the Files section (folder phenrotay) 2 pics that show how
the 3 reference stars are positioned in the PASILL4 after
having achieved a good (< 1 arcmin) polar alignment:

- PASILL4-1.jpg : Polaris approximately with a perpendicular offset
from its gap: it was near the base of the engraved arrow head pointing
at the gap where Polaris should be. PASILL4 rotated to have the 2 other
stars are put in their gap line or close.

- PASILL4-2.jpg , when rotating the polar scope to bring Polaris in its
gap,the two other stars were far from their radial lines (30 degrees or
so for delta UMi).

Not 100% accurate of course, just to give an idea of the deviations.

Pierre


observe_m13
 

--- In ap-gto@..., "phenrotay" <Pierre.Henrotay@...> wrote:

Hello all,

I am running a Mach1 and experience some problems with my polar
alignment scope (PASILL4). I'd appreciate your ideas here.
.
.
.
One thing I thought of was that the polarscope might be not aligned
within the axis once screwed in but I would be very very surprising.
Is there a way to check this ?
Maybe I am doing wrong or assuming something incorrectly but I
cannot see what is the trouble. I'd welcome your ideas and hints.
The mount is properly balanced, the telescope is rigidly attached,
the imaging combo is not very heavy (NP127 + DSLR).

Regards,
Pierre
Hi Pierre,

I think you might have discovered the error here. From you description
it sounds like you have centered the polar scope in the housing but
you haven't checked the relationship of the PAS housing to the mount.
Set up the mount so that the polar axis is close to horizontal - as if
you were setting it up near the equator at 0 latitude. You do not need
nor want your OTA or counterweights / shaft on for this. With the
polar scope in place, move the mount and point the crosshairs at
something a long distance off. (that is why the setup at close to
horizontal - so you can look for something that is permanent in
relationship to the telescope. You cannot use a star for this since
the earth is continually moving with relation to the sky. Then,
without rotating the polar scope, loosen the clutches or slew with the
handpaddle to rotate the whole RA axis by 180 degrees and see where
the polar scope crosshairs are pointing. If they are not on the
original point of aim, then the housing with relation to the polar
scope itself will require adjustment and since I don't have any
information here I can't tell you how to go about doing that. Maybe
there is something in the PAS manual.

Rick.


Pierre Henrotay
 

Rick,

the Mach1 is a bit different from the other AP mounts: turning the
polar axis does not also turn the polar scope. The polar axis shaft
does not reach all the way to the bottom of the polar axis housing.
So the only thing I can check is the centering of the reticle in the
polar alignment scope itself.

Pierre


Pierre Henrotay
 

Kent,

I used these screws indeed to optically center the reticle within the
polar scope itself - as indicated in my original post.

What I cannot do is check the centering of the polar scope (and the
aligned reticle) within the polar axis itself: the Mach1 is a bit
different from the other AP mounts: turning the polar axis does _not_
also turn the polar scope.
I would however be surprised that the polar axis of the mount and the
axis of the polar scope be misaligned after threading in. Not typical
of AP.

Pierre


observe_m13
 

--- In ap-gto@..., "phenrotay" <Pierre.Henrotay@...> wrote:

Rick,

the Mach1 is a bit different from the other AP mounts: turning the
polar axis does not also turn the polar scope. The polar axis shaft
does not reach all the way to the bottom of the polar axis housing.
So the only thing I can check is the centering of the reticle in the
polar alignment scope itself.

Pierre
Darn, you are absolutely right! As soon as you mentioned it the mental
image of the AP mounts popped up. Now just how DOES one test the
mechanical alignment of the cope within the mounting plug?

Rick.


observe_m13
 

--- In ap-gto@..., "phenrotay" <Pierre.Henrotay@...> wrote:

Kent,

I used these screws indeed to optically center the reticle within the
polar scope itself - as indicated in my original post.

What I cannot do is check the centering of the polar scope (and the
aligned reticle) within the polar axis itself: the Mach1 is a bit
different from the other AP mounts: turning the polar axis does _not_
also turn the polar scope.
I would however be surprised that the polar axis of the mount and the
axis of the polar scope be misaligned after threading in. Not typical
of AP.

Pierre
There is only one way to check! Same set-up I suggested originally but
instead of moving the RA axis, which will do absolutely nothing as you
pointed out, rotate the polar scope 180 degrees. If the crosshair
position shifts relative to a fixed object, the reticle will have to
be adjusted. This will test the complete polar scope and mounting plug
assembly. We are going to have to assume that the threading and holes
are on-axis with the rotational axis of the RA. I know I have to
adjust my Pasill4 as well so this has been instructive to think about.
It definitely is not as well aligned as my older Pasill3.


Muhammed Samir Kharusi
 

I am very keen to hear the resolution of this one since I have
another mount that has similar issues. I really wonder whether we can
assume so casually that the threads for the polar scope are as well
aligned with the RA axis as we seem to be doing here. We are talking
of a "few" arc-minutes, on a thread that is not very long either,
under a cm? Perhaps AP can comment as to whether they have been
paying the requisite great attention in the fabrication process, or
assuming that we will always drift align anyway (refraction, etc).
The below-suggested method of rotating the scope 180deg presumably
assumes loosening the scope. Recall that we are talking arc-minutes.
Loosening does not seem appropriate. I do not own a Mach1 so I cannot
verify that one can rotate the entire assembly without loosening.
Recall that the chap has already rotated and fixed the reticle to
match the rotatable part of the scope, and that what has delivered us
to this stage.
--- In ap-gto@..., "Rick K" <JunkMailGoesHere@...> wrote:

--- In ap-gto@..., "phenrotay" <Pierre.Henrotay@> wrote:

Kent,

I used these screws indeed to optically center the reticle within
the
polar scope itself - as indicated in my original post.

What I cannot do is check the centering of the polar scope (and
the
aligned reticle) within the polar axis itself: the Mach1 is a
bit
different from the other AP mounts: turning the polar axis does
_not_
also turn the polar scope.
I would however be surprised that the polar axis of the mount and
the
axis of the polar scope be misaligned after threading in. Not
typical
of AP.

Pierre
There is only one way to check! Same set-up I suggested originally
but
instead of moving the RA axis, which will do absolutely nothing as
you
pointed out, rotate the polar scope 180 degrees. If the crosshair
position shifts relative to a fixed object, the reticle will have to
be adjusted. This will test the complete polar scope and mounting
plug
assembly. We are going to have to assume that the threading and
holes
are on-axis with the rotational axis of the RA. I know I have to
adjust my Pasill4 as well so this has been instructive to think
about.
It definitely is not as well aligned as my older Pasill3.


Pierre Henrotay
 

Rick,


There is only one way to check! Same set-up I suggested originally
but
instead of moving the RA axis, which will do absolutely nothing as
you
pointed out, rotate the polar scope 180 degrees. If the crosshair
position shifts relative to a fixed object, the reticle will have to
be adjusted. This will test the complete polar scope and mounting
plug
assembly. We are going to have to assume that the threading and
holes
are on-axis with the rotational axis of the RA. I know I have to
adjust my Pasill4 as well so this has been instructive to think
about.
It definitely is not as well aligned as my older Pasill3.
This is the first thing I did; the steps are clearly described in the
instructions which come with the PASILL4, under "Initial
adjustments". This is OK: no move/shift when rotating the polar
scope. I also rechecked this the next morning after my test: no
change, still OK.
As you adequately mention, "We are going to have to assume that the
threading and holes are on-axis with the rotational axis of the RA."
I see no way to check this, I think it is highly unlikely and would
like to eliminate/check all other possibilities first - if any remain.

Pierre


Roland Christen
 

In a message dated 4/13/2008 11:13:49 PM Central Daylight Time,
samirkharusi@... writes:


I really wonder whether we can
assume so casually that the threads for the polar scope are as well
aligned with the RA axis as we seem to be doing here. We are talking
of a "few" arc-minutes, on a thread that is not very long either,
under a cm? Perhaps AP can comment as to whether they have been
paying the requisite great attention in the fabrication process
Well, the fabrication process of the threads in the polar axis is all done by
modern CNC machinery, and this does not in itself cause any misalignment
problems. When a housing rotates in a lathe chuck it is always aligned with itself
and any cuts or threads that are taken on the surfaces are alsoautomatically
aligned.

What we cannot control is the placement of the reticle in the polar scope.
This is adjustable, so the lateral displacement of the reticle is never going to
be perfectly centered from the factory that makes this scope. Once installed
in the polar axis, one needs to rotate the scope/reticle combination while
pointing to a faraway object and adjust the reticle so that the crosshairs are
always pointing in exactly the same position no matter what angle the scope is
rotated to. This is a given with this scope.

Rolando


**************
It's Tax Time! Get tips, forms and advice on AOL Money &amp;
Finance.
(http://money.aol.com/tax?NCID=aolcmp00300000002850)


Roland Christen
 

In a message dated 4/14/2008 10:49:32 AM Central Daylight Time,
Pierre.Henrotay@... writes:


What I further observed looks interesting IMHO:
- (confirmation) the reticle has been carefully aligned: when
rotating the reticle housing, there is no change in the position of a
remote object centered at the crossed lines; so to me the poslar
scope itself is OK
- if I turn (unscrew) the polar scope adapter - the metallic end of
the RA axis with a knurled grip - I notice that the centered object
moves off the reticle lines and defintely travels in a circle; when
doing a 360 turn, it is back to the original position.
We have no input on the manufacture of the polar scope, so however it is
centered in the adapter, we have no control over that. It is a manufactured item
that we purchase from Losmandy. The polar scope adapter along with the scope
should be screwed tight and not loosened. Once tight it can be adjusted so that
the reticle is centered and stays centered when the entire assembly is rotated
inside its own axis. When it is tight in the axis, the threaded parts are no
longer in the picture and can be considered fused together as if they were one
piece. So please do not chase red herrings down blind alleys.

If it appears that your polar scope is not accurate compared to other methods
of polar alignment, then perhaps the reticle itself is not accurate. If it is
repeatable, then place Polaris in that spot where your other methods say it
should be. If it is not repeatable, then I have no solution for you in your
case. In my case, I use the polar scope to get me close, and then I drift align.
This has always worked well for me in the field.

Rolando


**************
It's Tax Time! Get tips, forms and advice on AOL Money &amp;
Finance.
(http://money.aol.com/tax?NCID=aolcmp00300000002850)


Roland Christen
 

In a message dated 4/14/2008 11:42:39 AM Central Daylight Time,
Pierre.Henrotay@... writes:


If it appears that your polar scope is not accurate compared to other
methods
of polar alignment, then perhaps the reticle itself is not accurate.
OK, noted. When do you consider then that a polar scope is defective ?
These reticles are all the same. If one is defective, then all are.
Personally I don't think they are, and I think they are quite useful, even if they are
not 100% perfect somehow. I have never seen perfect optics, neither have I
ever seen perfect mechanics, yet we all do well with what is possible in our
imperfect world. If you are not happy with the scope, then of course we will take
it back.

Rolando


**************
It's Tax Time! Get tips, forms and advice on AOL Money &amp;
Finance.
(http://money.aol.com/tax?NCID=aolcmp00300000002850)


Roland Christen
 

In a message dated 4/14/2008 12:02:42 PM Central Daylight Time,
Pierre.Henrotay@... writes:


About "the threaded parts are no longer in the picture": to me I see
a difference: for the Mach1, centering the reticle is bringing it on
the optical axis of the polar scope. For the other AP mounts, where
the polar scope rotates with the RA axis, centering the reticule is
bringing it on the RA axis - fort hse indeed the threaded parts
appear as "fused together". However, for the Mach1, if the threaded
parts are not exactly centered, this induces an error which cannot be
corrected by centering the reticle (as the reticle housing rotates).

What really annoys me is that the error is big - more than 10
arcminutes; as you wrote, if repeatable, there might be workarounds.
Need to check again one the sky clears up... in one month or so ...
This leaves me plenty of time to find out where this expression about
red herrings come from ;-) - I am not a native english speaker, as
you have probably recognized.
In this case there may not be any solution since we cannot bring the rotating
part of the RA axis back far enough to accomodate the polar scope. I don't
think that the threaded part of the Mach1 RA housing can be off since these are
machined as one piece on a CNC. It is possible that the threads on the polar
scope are not aligned with the optical axis of the polar scope. There are many
parts to the scope, and these are assembled with various threads and fittings.
I can't off-hand think of any way to check all these alignments. We have
always relied on moving the reticle about in order to center it in the optical
axis. If anyone has any ideas, I'm open to suggestions.

Rolando


**************
It's Tax Time! Get tips, forms and advice on AOL Money &amp;
Finance.
(http://money.aol.com/tax?NCID=aolcmp00300000002850)


observe_m13
 

I am at a loss as to how to test for this error other than in use on
the sky with a separate verifiable method of polar alignment and then
working backwards, seeing where the PAS is actually pointing. This is
what Pierre started when he measured the error after using other
software to get a fairly good polar alignment. As far as I can tell
this would be the only time possible to adjust the reticle to match
any possible slight inaccuracies in the PAS alignment with the mount.

Rick.

--- In ap-gto@..., "Samir Kharusi" <samirkharusi@...> wrote:

I am very keen to hear the resolution of this one since I have
another mount that has similar issues. I really wonder whether we can
assume so casually that the threads for the polar scope are as well
aligned with the RA axis as we seem to be doing here. We are talking
of a "few" arc-minutes, on a thread that is not very long either,
under a cm? Perhaps AP can comment as to whether they have been
paying the requisite great attention in the fabrication process, or
assuming that we will always drift align anyway (refraction, etc).
The below-suggested method of rotating the scope 180deg presumably
assumes loosening the scope. Recall that we are talking arc-minutes.
Loosening does not seem appropriate. I do not own a Mach1 so I cannot
verify that one can rotate the entire assembly without loosening.
Recall that the chap has already rotated and fixed the reticle to
match the rotatable part of the scope, and that what has delivered us
to this stage.
--- In ap-gto@..., "Rick K" <JunkMailGoesHere@> wrote:

--- In ap-gto@..., "phenrotay" <Pierre.Henrotay@> wrote:

Kent,

I used these screws indeed to optically center the reticle within
the
polar scope itself - as indicated in my original post.

What I cannot do is check the centering of the polar scope (and
the
aligned reticle) within the polar axis itself: the Mach1 is a
bit
different from the other AP mounts: turning the polar axis does
_not_
also turn the polar scope.
I would however be surprised that the polar axis of the mount and
the
axis of the polar scope be misaligned after threading in. Not
typical
of AP.

Pierre
There is only one way to check! Same set-up I suggested originally
but
instead of moving the RA axis, which will do absolutely nothing as
you
pointed out, rotate the polar scope 180 degrees. If the crosshair
position shifts relative to a fixed object, the reticle will have to
be adjusted. This will test the complete polar scope and mounting
plug
assembly. We are going to have to assume that the threading and
holes
are on-axis with the rotational axis of the RA. I know I have to
adjust my Pasill4 as well so this has been instructive to think
about.
It definitely is not as well aligned as my older Pasill3.


observe_m13
 

I forgot to add that by changing the alignment to match the mount, it
may make the PAS specifically aligned for that mount only and not
transportable between other AP mounts you may have. I do know in my
case that the older PAS3 I have is better aligned, for whatever
reason, than my newer PAS4 since I have used both with the same mount
several times. The PAS3 is closer to a 'good' polar alignment than the
PAS4.

I think the original intent was to supply a relatively inexpensive
polar scope to get one close, certainly close enough for visual goto
operation across the entire sky with a little care, and then follow up
with some other more rigorous polar alignment method if required for
astrophotography. It may be that there is no free lunch and that some
suitable polar alignment method will always be required over and above
the PAS scopes.

Rick.

--- In ap-gto@..., "Rick K" <JunkMailGoesHere@...> wrote:

I am at a loss as to how to test for this error other than in use on
the sky with a separate verifiable method of polar alignment and then
working backwards, seeing where the PAS is actually pointing. This is
what Pierre started when he measured the error after using other
software to get a fairly good polar alignment. As far as I can tell
this would be the only time possible to adjust the reticle to match
any possible slight inaccuracies in the PAS alignment with the mount.

Rick.


--- In ap-gto@..., "Samir Kharusi" <samirkharusi@> wrote:

I am very keen to hear the resolution of this one since I have
another mount that has similar issues. I really wonder whether we can
assume so casually that the threads for the polar scope are as well
aligned with the RA axis as we seem to be doing here. We are talking
of a "few" arc-minutes, on a thread that is not very long either,
under a cm? Perhaps AP can comment as to whether they have been
paying the requisite great attention in the fabrication process, or
assuming that we will always drift align anyway (refraction, etc).
The below-suggested method of rotating the scope 180deg presumably
assumes loosening the scope. Recall that we are talking arc-minutes.
Loosening does not seem appropriate. I do not own a Mach1 so I cannot
verify that one can rotate the entire assembly without loosening.
Recall that the chap has already rotated and fixed the reticle to
match the rotatable part of the scope, and that what has delivered us
to this stage.
--- In ap-gto@..., "Rick K" <JunkMailGoesHere@> wrote:

--- In ap-gto@..., "phenrotay" <Pierre.Henrotay@> wrote:

Kent,

I used these screws indeed to optically center the reticle within
the
polar scope itself - as indicated in my original post.

What I cannot do is check the centering of the polar scope (and
the
aligned reticle) within the polar axis itself: the Mach1 is a
bit
different from the other AP mounts: turning the polar axis does
_not_
also turn the polar scope.
I would however be surprised that the polar axis of the mount and
the
axis of the polar scope be misaligned after threading in. Not
typical
of AP.

Pierre
There is only one way to check! Same set-up I suggested originally
but
instead of moving the RA axis, which will do absolutely nothing as
you
pointed out, rotate the polar scope 180 degrees. If the crosshair
position shifts relative to a fixed object, the reticle will have to
be adjusted. This will test the complete polar scope and mounting
plug
assembly. We are going to have to assume that the threading and
holes
are on-axis with the rotational axis of the RA. I know I have to
adjust my Pasill4 as well so this has been instructive to think
about.
It definitely is not as well aligned as my older Pasill3.


Kent Kirkley
 

In a message dated 4/14/08 12:51:45 PM, llp41astro@... writes:


Pierre,
I have not had this problem when using my PASILL4 which you seem to
have.  One thing to note that has been discussed on the Losmandy site
is the star location is dependent on the magnification of the PAS
lens.  These have been known in the past to be inaccurate and cause
the stars to be mislocated.  It appears from your pics that they have
slightly too much magnification.  Perhaps trying a second scope might
prove enligntening.

Larry
Back in 1996-97 there was a 'batch' of Losmandy Polar Alignment Scopes that
had the wrong magnification of the reticle, resulting in an inability to place
Polaris and the other two stars where they should be. At that time Celestron
was selling the G-11 as their own and replaced the PAS if you had gotten one. I
did and they did.

Kent Kirkley


**************
It's Tax Time! Get tips, forms and advice on AOL
Money &amp; Finance.
(http://money.aol.com/tax?NCID=aolcmp00300000002850)


Pierre Henrotay
 

Hi Roland,

the alignment of the polar scope to the RA axis is/was also the least
probable in my mind.
This is why I wanted to explore all other possible causes first but I
am out of ideas. A difference of more than 10 arcminutes is too big
tyo be left unexplained.

What I further observed looks interesting IMHO:
- (confirmation) the reticle has been carefully aligned: when
rotating the reticle housing, there is no change in the position of a
remote object centered at the crossed lines; so to me the poslar
scope itself is OK
- if I turn (unscrew) the polar scope adapter - the metallic end of
the RA axis with a knurled grip - I notice that the centered object
moves off the reticle lines and defintely travels in a circle; when
doing a 360 turn, it is back to the original position.

I make no conclusion of that but I would reconsider the idea that
maybe there is a discrepancy btw RA axis and polar scope axis once
scrwed in. Or am I wrong ?

Pierre


--- In ap-gto@..., chris1011@... wrote:

In a message dated 4/13/2008 11:13:49 PM Central Daylight Time,
samirkharusi@... writes:


I really wonder whether we can
assume so casually that the threads for the polar scope are as
well
aligned with the RA axis as we seem to be doing here. We are
talking
of a "few" arc-minutes, on a thread that is not very long either,
under a cm? Perhaps AP can comment as to whether they have been
paying the requisite great attention in the fabrication process
Well, the fabrication process of the threads in the polar axis is
all done by
modern CNC machinery, and this does not in itself cause any
misalignment
problems. When a housing rotates in a lathe chuck it is always
aligned with itself
and any cuts or threads that are taken on the surfaces are
alsoautomatically
aligned.

What we cannot control is the placement of the reticle in the polar
scope.
This is adjustable, so the lateral displacement of the reticle is
never going to
be perfectly centered from the factory that makes this scope. Once
installed
in the polar axis, one needs to rotate the scope/reticle
combination while
pointing to a faraway object and adjust the reticle so that the
crosshairs are
always pointing in exactly the same position no matter what angle
the scope is
rotated to. This is a given with this scope.

Rolando


**************
It's Tax Time! Get tips, forms and advice on AOL Money &amp;
Finance.
(http://money.aol.com/tax?NCID=aolcmp00300000002850)


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