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


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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


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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

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.

What is the size of the set screws that hold the CPO3 control box onto the AP1200 GTO
mount? Is it 8-32 or a different size? I'll be removing the box and would like to have a couple
of thumb screws to replace the set screws so I don't have to think about having a hex set with
me in the dark...
Morgan

One of the coolest designs for a small college observatory was this one that I saw in the
little Florida town my sister lives in:

http://www.dagarchitects.com/projects/project.aspx?
PortfolioItemID=6228243288807213646&ImagePage=0&DisplayImage=-
5645039808127803596

I think the URL is so long you'll have to paste it on to get it to work. The project is for
Okaloosa Walton Community College by DAG Architects. Shaped like a shell (they're near
the Gulf of Mexico in the Panhandle), it has a beautiful ashdome surrounded by a circular
pad with about 8 permanent piers. The rear building is a classroom for the college's
astronomy classes. Its set off in the woods, so its quite dark and quiet at night. Just a
thought; I think its quite well thought out and distinctive.

Morgan

--- 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.

--- 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.

Hi Paul,

The layout and size of your public pads will obviously be dictated
by the amount of space you have (and any viewing obstructions) as
well as access for parking and driveway space.

I can describe a successful installation at the San Diego Astronomy
Association east of San Diego at Terra Del Sol, CA. Some 30+ years
ago (maybe 40+), the club installed a long concrete pad about 10 to
12 ft wide running east-west. Parking is on the north side, with
most cars backed into place so that vans and hatchbacks provide easy
access to unload or load equipment. Power posts are provided along
the length (I think at about 20 ft intervals). The concrete pad
follows the contour of the land, so each setup requires leveling for
a vertical pier. No permanent piers are on this pad. A second pad
like this was built more recently parallel to the first, about 75 ft
south, with cars also parking on the north side of that pad. The
system works very well, with great star party etiquette, and a
minimum of auto light pollution from arrivals and departures. It's
not uncommon to have up to 30 or 40 scopes setup on these pads.
Scopes range from binocular observers to Dobsonians, SCT's up to
high end refractors, both visual and astrophotography.

At this facility, permanent piers are allowed on "private pads",
each with it's own power and parking space. These pads are
maintained by individual "owners" who rent the spots and have their
dedicated piers to fit their mounts. The whole area is in the
desert, so there is brush 5 or 6 ft high that separates individual
private pads and the public pads to reduce light interference.

Public rest rooms and showers are located nearby for both Women and
Men.

One recommendation I have is to make the concrete pad flush with the
ground. A raised edge is a tripping obstruction at night.

Hope this helps give some ideas,

Don Westergren

--- In ap-gto@..., "Paul Gustafson" <laservet@...> wrote:

I'm tangentially involved in the planning of the fourth of four
observatories across the US that will be used primarily for
education. The third, to some extent, but primarily the fourth

will

be used for real science as well as education, articles to be
published in the Astrophysical Journal, and will have full remote
capability with broadband at the observatory. The observatory is
under construction, scope, dome and mount already here in storage.

My task is to find plans for a concrete scope pad that will be

near

the observatory to give club members a place to set up. It should

be

large enough for 6 to 8 scopes with power to all, hopefully two or
three locations with piers (looking at Le Seur AstroPiers, same as

in

the four observatories). Anyone have any experience or could point

me

in a productive direction? We don't know if it would be more
economical or more functional to have a large rectangular pad,
something like a boat pier with smaller pads off a central

walkway,

hexagonal or circular pads interconnected, just don't know. We'd

like

to keep the cost down, concrete is being done by a commercial
concrete company, but it's more important to do it right.

Any suggestions would be greatly appreciated.

All four observatories will have AP 1200 mounts (to keep on topic

for

group) in domes, would be nice if at least a couple of the pads

would

be AP900-friendly as well. :-)

Paul Gustafson

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

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

--- 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.

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

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

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

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




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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

Help me to understand.
After upgrading the keypad to firmware 4.15 and after favourably
checking Status "All system go", in a mount 400GTO purchased in October
2000, the Time, Date,GMT,LST and Photo Timer no more update and no more
advance as before (red lights blink but do not change digits in
Time/LST).
Could it be Real Time Clock Battery exhausted or could it be for some
other reason I can't understand?
Do you think I can still make use of the mount or I have to change RTC
chip?

I'm tangentially involved in the planning of the fourth of four
observatories across the US that will be used primarily for
education. The third, to some extent, but primarily the fourth will
be used for real science as well as education, articles to be
published in the Astrophysical Journal, and will have full remote
capability with broadband at the observatory. The observatory is
under construction, scope, dome and mount already here in storage.

My task is to find plans for a concrete scope pad that will be near
the observatory to give club members a place to set up. It should be
large enough for 6 to 8 scopes with power to all, hopefully two or
three locations with piers (looking at Le Seur AstroPiers, same as in
the four observatories). Anyone have any experience or could point me
in a productive direction? We don't know if it would be more
economical or more functional to have a large rectangular pad,
something like a boat pier with smaller pads off a central walkway,
hexagonal or circular pads interconnected, just don't know. We'd like
to keep the cost down, concrete is being done by a commercial
concrete company, but it's more important to do it right.

Any suggestions would be greatly appreciated.

All four observatories will have AP 1200 mounts (to keep on topic for
group) in domes, would be nice if at least a couple of the pads would
be AP900-friendly as well. :-)

Paul Gustafson

Hi Rick,

Here is the other link I had for a backyard BOX observatory, covering just the Meade 8" telescope on a pier - with blue prints..
Collier Hall of Science at Moravian College in Bethlehem, PA

http://home.moravian.edu/users/phys/mejjg01/interests/apparatus_pages/telescope_enclosure.htm