Date   

Re: pointing accuracy

Louis A. Mamakos <louie@...>
 

Hi Colt,

Yes, from one part of the sky to the opposite side I have
seen better than 2-arc-minutes accuracy. To get this kind
of accuracy you need to make sure your OTA is orthogonal
and that none of the optical elements shift in movement
(e.g. many SCT's primary mirrors will shift when you move
to another part of the sky). That is why I said I get this
accuracy with my refractor.
Ah, so this makes sense. Based on my experience with some digital
setting circles on my G-11 mount (on the waiting list for a 900GTO, sigh),
polar alignment doesn't seem significant. That's of course doing a
two star alignment.

Orthoganality does seem very important during alignment (e.g., the
SET DEC=0 step) can be difficult on the G-11 given the lack of a fixed
declination axis setting circle.

louie


Re: pointing accuracy

Ron Wodaski <ronw@...>
 

I think that pointing accuracy on any of the AP goto mounts is excellent,
and mostly depends on how well aligned you are to the celestial pole. On
nights when I have taken the time for really good polar alignment, objects
routinely show up in just about exactly the same spot on the CCD chip. On
those nights, it wouldn't matter what camera I was using; objects would be
on the chip. <g>

To get really high pointing accuracy, you must also make sure that your
scope is well aligned to the mount's RA axis, of course.

Ron Wodaski

-----Original Message-----
From: Colt Bednorz [mailto:colt@airmail.net]
Sent: Saturday, May 06, 2000 8:44 AM
To: ap-gto@egroups.com
Subject: Re: [ap-gto] pointing accuracy


Ray,
So, it's not only on the chip of a st7/8, but not too far off center.
I looked at what u see and that would even hit the st-4's
little chip for a standard sct.
Thanks
Colt

Ray Gralak wrote:

Hi Colt,

With really good polar alignment (and my 5" refractor) I have
seen better than 2 arc-minutes accuracy on my 1200 GTO. And most
of that error could be from non-perfect polar alignment.

Taka care,

-Ray Gralak

-----Original Message-----
From: Colt Bednorz [mailto:colt@airmail.net]
Sent: Saturday, May 06, 2000 7:59 AM
To: ap-gto@egroups.com
Subject: [ap-gto] pointing accuracy



What is the pointing accuracy of the A.P.1200?
Assuming everything is accurately set up, and polar
aligned, what do you normally get?
I would imagine that this feature, which I've never had, is
pretty nice for imaging those faint invisible objects.

Thanks
Colt Bednorz


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Re: pointing accuracy

Ray Gralak <ray@...>
 

Hi Colt,

Yes, from one part of the sky to the opposite side I have
seen better than 2-arc-minutes accuracy. To get this kind
of accuracy you need to make sure your OTA is orthogonal
and that none of the optical elements shift in movement
(e.g. many SCT's primary mirrors will shift when you move
to another part of the sky). That is why I said I get this
accuracy with my refractor.

Take care,

-Ray

-----Original Message-----
From: Colt Bednorz [mailto:colt@airmail.net]
Sent: Saturday, May 06, 2000 8:44 AM
To: ap-gto@egroups.com
Subject: Re: [ap-gto] pointing accuracy


Ray,
So, it's not only on the chip of a st7/8, but not too far off center.
I looked at what u see and that would even hit the st-4's
little chip for a standard sct.
Thanks
Colt

Ray Gralak wrote:

Hi Colt,

With really good polar alignment (and my 5" refractor) I have
seen better than 2 arc-minutes accuracy on my 1200 GTO. And most
of that error could be from non-perfect polar alignment.

Taka care,

-Ray Gralak

-----Original Message-----
From: Colt Bednorz [mailto:colt@airmail.net]
Sent: Saturday, May 06, 2000 7:59 AM
To: ap-gto@egroups.com
Subject: [ap-gto] pointing accuracy



What is the pointing accuracy of the A.P.1200?
Assuming everything is accurately set up, and polar
aligned, what do you normally get?
I would imagine that this feature, which I've never had, is
pretty nice for imaging those faint invisible objects.

Thanks
Colt Bednorz


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Re: pointing accuracy

Colt Bednorz <colt@...>
 

Ray,
So, it's not only on the chip of a st7/8, but not too far off center.
I looked at what u see and that would even hit the st-4's
little chip for a standard sct.
Thanks
Colt

Ray Gralak wrote:

Hi Colt,

With really good polar alignment (and my 5" refractor) I have
seen better than 2 arc-minutes accuracy on my 1200 GTO. And most
of that error could be from non-perfect polar alignment.

Taka care,

-Ray Gralak

-----Original Message-----
From: Colt Bednorz [mailto:colt@airmail.net]
Sent: Saturday, May 06, 2000 7:59 AM
To: ap-gto@egroups.com
Subject: [ap-gto] pointing accuracy



What is the pointing accuracy of the A.P.1200?
Assuming everything is accurately set up, and polar
aligned, what do you normally get?
I would imagine that this feature, which I've never had, is
pretty nice for imaging those faint invisible objects.

Thanks
Colt Bednorz


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http://click.egroups.com/1/3555/5/_/3615/_/957624889/
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Re: pointing accuracy

Ray Gralak <ray@...>
 

Hi Colt,

With really good polar alignment (and my 5" refractor) I have
seen better than 2 arc-minutes accuracy on my 1200 GTO. And most
of that error could be from non-perfect polar alignment.

Taka care,

-Ray Gralak

-----Original Message-----
From: Colt Bednorz [mailto:colt@airmail.net]
Sent: Saturday, May 06, 2000 7:59 AM
To: ap-gto@egroups.com
Subject: [ap-gto] pointing accuracy



What is the pointing accuracy of the A.P.1200?
Assuming everything is accurately set up, and polar
aligned, what do you normally get?
I would imagine that this feature, which I've never had, is
pretty nice for imaging those faint invisible objects.

Thanks
Colt Bednorz


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pointing accuracy

Colt Bednorz <colt@...>
 

What is the pointing accuracy of the A.P.1200?
Assuming everything is accurately set up, and polar
aligned, what do you normally get?
I would imagine that this feature, which I've never had, is
pretty nice for imaging those faint invisible objects.

Thanks
Colt Bednorz


Re: Help with AP GTO on Parallax 125

ericj <ericj@...>
 

Peter wrote:

Can you or anyone tell me where to find a
three-star alignment technique? I've never heard of that before. Does it
require polaris?
Hi Peter:

Please see my response to Mike's question about the "three star alignment
procedure". I think I inadvertently created it :-). If you cannot use
Polaris from your site and the two-star alignment procedure isn't working
try using a third calibration star. It helped me to get accurate alignment.
Let us know how it goes.

Clear Skies,

Eric Jamison


Re: Help with AP GTO on Parallax 125

ericj <ericj@...>
 

Mike Mah wrote:

What is the three star alignment procedure? I don't recall seeing
this in the manual.
Hi Mike:

I think I inadvertently created the "three star alignment procedure" :-). I
noticed the other night that after I had used the two star alignment
procedure (Polaris and Vega) when the scope slewed to a deep-sky object it
was not quite in the center of the field of view, even in a low power
eyepiece. On page 8 of the GTO Keypad Controller manual, items 7 through 14,
it recommends that using additional calibration stars to get a more accurate
polar alignment.

In my case after I used Regulus as my third calibration star (the "third"
star in my "three star alignment procedure") any deep-sky object that the
scope slewed to was near the center of the field of view of the 16mm Zeiss.
Normally when deep-sky observing I start off with a low power 2" eyepieces
like a 56mm Meade or 35mm Panoptic and work my up to higher power views
using the 1-1/4" eyepieces. But Sunday night it was late, I was tired, so I
just left the 16mm in. When AP comes out with the polar scope it should make
the whole polar alignment process much easier and faster.

I should mention that I have only had the mount for a short while, and only
had the chance to use it a few times, so am learning like everyone else.
Also, I did not mean to imply that the Dec setting circle on other AP GTO
mounts might be off slightly as mine was. I think I just happened to get one
that had this issue.

Clear Skies,

Eric Jamison

-----Original Message-----
From: Mike Mah <mikemah@attglobal.net>
To: ap-gto@egroups.com <ap-gto@egroups.com>
Date: Friday, May 05, 2000 8:42 PM
Subject: Re: [ap-gto] Help with AP GTO on Parallax 125


Thanks for the advice, everyone.

What is the three star alignment procedure? I don't recall seeing
this in the manual.

Mike Mah


Re: Help with AP GTO on Parallax 125

Mike Mah
 

Thanks for the advice, everyone.

What is the three star alignment procedure? I don't recall seeing
this in the manual.

Mike Mah

--- In ap-gto@egroups.com, "ericj" <ericj@m...> wrote:
Hi Mike:

I just recently went through this with my 900 GTO mount so can
offer a
couple of suggestions.

This is how I tried to align the mount and scope on Polaris, as
suggested in
the AP manual that comes with the mount. After setting up the mount
and
setting the Dec setting circle to 90 degrees I would look through
the polar
alignment sight hole in the center of the polar axis to align on
Polaris.
Then I would add the counterweight shaft and counterweights, and
finally the
tube assembly. Each time I did this though I noted that OTA would
be offset
slightly to the left or west of Polaris.

At first I thought that I had somehow shifted the mount a little
when adding
the counterweights and tube assembly, so would just "pick up" (more
like
nudge) the mount and scope until Polaris was aligned through the
scope. But
I found that even after using the two star alignment method I would
not end
up anywhere near the deep-sky object that I was trying to find
using the GTO
feature.

So finally I looked through the polar alignment sight hole and to
my
surprise Polaris was no where to be seen, even though it was still
centered
in scope. At this point I figured the problem had to be that the
rings were
not orthogonal with the mount. So off came the OTA and after
checking the
rings realized they were fine. I then removed the ribbed mounting
plate and
examined it to see if there could be a problem with it. It was fine
too
however.

My next thought was that since I had used the used the scope and
rings on my
home made Dob mount for the past four years that somehow I warped
the rings
slightly (I rotate the rings on their sides and attach side
bearings to
them; a photo of how they look is on my web page at
http://www.metro2000.net/~ericj, and click on Telescopes). I
couldn't be
sure if this was a problem or not, and figured the only way to be
sure was
to find another pair of AP mounting rings that would not be warped.
Since I
have only had my 5.1" AP for less then a year I figured the
likelihood that
these rings would be warped as the rings for the 7.1" were was
unlikely.

So off came the 7.1" and rings, and on went the 5.1" and rings.
Same
problem. Finally, I decided to look down the polar alignment sight
hole from
the front to see if it looked aligned correctly. It didn't. With
the setting
circle to 90 degrees the Dec axis seemed off to one side. I aligned
it by
eye so that it appeared to be aligned correctly, and noted that the
Dec
setting circle read 87 degrees. Back on went the 5.1" with rings,
and this
time with the mount aligned on Polaris the scope was aligned on
Polaris as
well.

Did the two star alignment method, but although the scope slewed
closer to
the deep-sky object it still was off. So I finally tried using
three star to
align the mount: Polaris, Vega, and Regulus. This time, the scope
slewed to
M101 correctly, and with the high contrast of the 5.1" the galaxy
was sharp,
well defined and surprisingly bright. Tried a few more objects and
the
results were the same.

At this point, even though it was a during the work week, and it
was almost
midnight, I couldn't resist the temptation of not using the 7.1".
So off
came the 5.1" and on went the 7.1". This time I was even more
careful when
aligning the mount, so I got to the point that I just left a 16mm
Zeiss
eyepiece in the MaxBright when slewing from object to object and
they were
often very close to the center of the FOV, which in the 16mm is
around half
a degree or so. I finally got to bed around 2 AM, but it was worth
it, even
though I dead tired the next day a work.

So I have a couple of suggestions for you. First, check to make
sure that
the rings and OTA is orthogonal with the mount.

Second, check to see if, when looking down the front of the polar
alignment
sight hole on your mount, if the Dec axis is centered or not. If
not, you
cold have the same problem that I do. I have sent an e-mail to Marj
and
mentioned it so she is aware of the situation. Whether yours has
the same
problem or not I am not sure, but you can check.

Third, when you are doing you alignment do not use the N-S-E-W
buttons to
recenter the star if it is off to one side. Use the altitude and
azimuth
adjusters on your mount for this.

Fourth, try using three star rather then two.

Hope this helps. For what it is worth, I have found the 900 to be a
very
fine and stable mount. I got into astronomy in the early 1970's,
and got
quite use to star hopping to find deep-sky objects. When computer
controlled
telescopes first came out I did not think I would ever want one.
However,
since I have now had a chance to use the GTO feature I realize that
there
are many deep-sky objects, like some of the fainter NGC or IC
objects, that
will be much easier to find and observe now. So I look forward to
many years
of finding and observing with my AP scopes and mounts.

Clear Skies,

Eric Jamison


Re: Help with AP GTO on Parallax 125

steppzimmr@...
 

In a message dated 5/5/00 1:33:50 AM Mid-Atlantic Daylight Time,
ericj@metro2000.net writes:

Fourth, try using three star rather then two.
Hi, I am very interested in this issue because I have the same problem with
my AP 600EGTO and cannot use polaris from my site. I've tried AP's two-star
alignment without success. Can you or anyone tell me where to find a
three-star alignment technique? I've never heard of that before. Does it
require polaris?

Peter


Re: Baader solar filter material question

lapides.family@...
 

Dear Jeffrey--
I also wanted a nice solar filter for my Stowaway. I found a manfacturer that
makes them for AP telescopes from the Baadar material. See
<phil.sonja@xtra.co.nz>. You can see a picture of the filter on his Web site.
The manfacturer is Phil Barker (in New Zealand I think). I'm scheduled to
receive mine early next wee for my Stowaway, and I can let you know how it
turned out. Phil seems like a very nice person and although he couldn't make me
one for a 50 mm finder, he generously offered to cut one for me and include it
in my package at no extra charge! Also Marj at Astro-Physics told me that
Kendrick Astro Instruments (2920 Dundas St. West, Toronto, ON M6P 1Y8 Canada)
has also agreed to start making the Baadar Solar Filters for the AP telescopes.
These are the same people that make the portable battery packs for the AP
mounts.
Good Luck! Richard Lapides



"Jeffrey D. Gortatowsky" wrote:

Well I did the best I could to create a decent cell for the Baader solar
filter material. It appears to be VERY serviceable cell if I do say so
myself. However I must say it looks like total hell. I did not get the
material PERFECTLY flat. It's not badly wrinkled, but it's not an optical
window either. Especially around the edges. If it's safe, I'll have it on
the 130EDT at RTMC and you can all have a good laugh! :) (Or I'll make a
new one before then!) No merit awards for craftsmanship here! LOL! I have
several digital pics of the cell and filter but am afraid to upload them.
You may hurt yourself laughing! :)

I have not tried it yet as I do have a question on safety (besides the Sun
had set<g>). I did blot a few pinholes with a black Sharpie pen. But there
really are quite a few when examined under an intense spotlight. Is it okay?
I mean we are talking teeny weeny tiny pin prick pinholes. If I blotted all
of them there would be a significant amount of black dots. Am I being too
picky? I am going to order another sheet as I should have used a stiffer
sandwich material which would have alleviated the flexure that caused the
'edge waves' (it's fairly flat in the middle. But for now, if things look
good by eye looking at the Sun, I'll try it (carefully) in the AM.

Clear skies,
Jeff

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Re: Baader solar filter material question

J. L. Schenz <deltatec@...>
 

Jeff,

I wouldn't trust the IR blocking in a Sharpie pen. To really block a pinhole
you want something that is totally opaque, to be safe. Any paint that has a
reasonable level of inorganic filler - titanium dioxide for instance - should
do it. It won't look as "pretty" but you retina will be safe.

Jim Schenz

"Jeffrey D. Gortatowsky" wrote:

Well I did the best I could to create a decent cell for the Baader solar
filter material. It appears to be VERY serviceable cell if I do say so
myself. However I must say it looks like total hell. I did not get the
material PERFECTLY flat. It's not badly wrinkled, but it's not an optical
window either. Especially around the edges. If it's safe, I'll have it on
the 130EDT at RTMC and you can all have a good laugh! :) (Or I'll make a
new one before then!) No merit awards for craftsmanship here! LOL! I have
several digital pics of the cell and filter but am afraid to upload them.
You may hurt yourself laughing! :)

I have not tried it yet as I do have a question on safety (besides the Sun
had set<g>). I did blot a few pinholes with a black Sharpie pen. But there
really are quite a few when examined under an intense spotlight. Is it okay?
I mean we are talking teeny weeny tiny pin prick pinholes. If I blotted all
of them there would be a significant amount of black dots. Am I being too
picky? I am going to order another sheet as I should have used a stiffer
sandwich material which would have alleviated the flexure that caused the
'edge waves' (it's fairly flat in the middle. But for now, if things look
good by eye looking at the Sun, I'll try it (carefully) in the AM.

Clear skies,
Jeff

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Re: Help with AP GTO on Parallax 125

Larry Denmark <kldenmark@...>
 

Thanks for the tips Eric. You wrote:

I just recently went through this with my 900 GTO mount so can offer a
couple of suggestions.
----snip----

...so I got to the point that I just left a 16mm Zeiss
eyepiece in the MaxBright when slewing from object to object...
Using star diagonals (e.g., MaxBright) saves wear and tear on one's neck and
knees, but can introduce polar alignment errors. Be certain that the star
diagonal is dead-on in it's position within the 2" focuser tube; i.e., make sure
it is absolutely flush up against the focuser. Also make certain your ocular is
seated properly. Finally, be certain to use an ocular with cross-hairs.

Third, when you are doing you alignment do not use the N-S-E-W buttons to
recenter the star if it is off to one side. Use the altitude and azimuth
adjusters on your mount for this.
Just for clarification, don't use the N-S-E-W buttons to *recenter* Polaris.
One should use the buttons to center the other reference stars.

Larry Denmark
----
E-mail ..... kldenmark@att.net
Web site .. http://home.att.net/~kldenmark/


Re: Baader solar filter material question

Jeffrey D. Gortatowsky
 

Forgive me. That was supposed to go to the ap-ug


Baader solar filter material question

Jeffrey D. Gortatowsky
 

Well I did the best I could to create a decent cell for the Baader solar
filter material. It appears to be VERY serviceable cell if I do say so
myself. However I must say it looks like total hell. I did not get the
material PERFECTLY flat. It's not badly wrinkled, but it's not an optical
window either. Especially around the edges. If it's safe, I'll have it on
the 130EDT at RTMC and you can all have a good laugh! :) (Or I'll make a
new one before then!) No merit awards for craftsmanship here! LOL! I have
several digital pics of the cell and filter but am afraid to upload them.
You may hurt yourself laughing! :)

I have not tried it yet as I do have a question on safety (besides the Sun
had set<g>). I did blot a few pinholes with a black Sharpie pen. But there
really are quite a few when examined under an intense spotlight. Is it okay?
I mean we are talking teeny weeny tiny pin prick pinholes. If I blotted all
of them there would be a significant amount of black dots. Am I being too
picky? I am going to order another sheet as I should have used a stiffer
sandwich material which would have alleviated the flexure that caused the
'edge waves' (it's fairly flat in the middle. But for now, if things look
good by eye looking at the Sun, I'll try it (carefully) in the AM.

Clear skies,
Jeff


Re: Help with AP GTO on Parallax 125

ericj <ericj@...>
 

Hi Mike:

I just recently went through this with my 900 GTO mount so can offer a
couple of suggestions.

This is how I tried to align the mount and scope on Polaris, as suggested in
the AP manual that comes with the mount. After setting up the mount and
setting the Dec setting circle to 90 degrees I would look through the polar
alignment sight hole in the center of the polar axis to align on Polaris.
Then I would add the counterweight shaft and counterweights, and finally the
tube assembly. Each time I did this though I noted that OTA would be offset
slightly to the left or west of Polaris.

At first I thought that I had somehow shifted the mount a little when adding
the counterweights and tube assembly, so would just "pick up" (more like
nudge) the mount and scope until Polaris was aligned through the scope. But
I found that even after using the two star alignment method I would not end
up anywhere near the deep-sky object that I was trying to find using the GTO
feature.

So finally I looked through the polar alignment sight hole and to my
surprise Polaris was no where to be seen, even though it was still centered
in scope. At this point I figured the problem had to be that the rings were
not orthogonal with the mount. So off came the OTA and after checking the
rings realized they were fine. I then removed the ribbed mounting plate and
examined it to see if there could be a problem with it. It was fine too
however.

My next thought was that since I had used the used the scope and rings on my
home made Dob mount for the past four years that somehow I warped the rings
slightly (I rotate the rings on their sides and attach side bearings to
them; a photo of how they look is on my web page at
http://www.metro2000.net/~ericj, and click on Telescopes). I couldn't be
sure if this was a problem or not, and figured the only way to be sure was
to find another pair of AP mounting rings that would not be warped. Since I
have only had my 5.1" AP for less then a year I figured the likelihood that
these rings would be warped as the rings for the 7.1" were was unlikely.

So off came the 7.1" and rings, and on went the 5.1" and rings. Same
problem. Finally, I decided to look down the polar alignment sight hole from
the front to see if it looked aligned correctly. It didn't. With the setting
circle to 90 degrees the Dec axis seemed off to one side. I aligned it by
eye so that it appeared to be aligned correctly, and noted that the Dec
setting circle read 87 degrees. Back on went the 5.1" with rings, and this
time with the mount aligned on Polaris the scope was aligned on Polaris as
well.

Did the two star alignment method, but although the scope slewed closer to
the deep-sky object it still was off. So I finally tried using three star to
align the mount: Polaris, Vega, and Regulus. This time, the scope slewed to
M101 correctly, and with the high contrast of the 5.1" the galaxy was sharp,
well defined and surprisingly bright. Tried a few more objects and the
results were the same.

At this point, even though it was a during the work week, and it was almost
midnight, I couldn't resist the temptation of not using the 7.1". So off
came the 5.1" and on went the 7.1". This time I was even more careful when
aligning the mount, so I got to the point that I just left a 16mm Zeiss
eyepiece in the MaxBright when slewing from object to object and they were
often very close to the center of the FOV, which in the 16mm is around half
a degree or so. I finally got to bed around 2 AM, but it was worth it, even
though I dead tired the next day a work.

So I have a couple of suggestions for you. First, check to make sure that
the rings and OTA is orthogonal with the mount.

Second, check to see if, when looking down the front of the polar alignment
sight hole on your mount, if the Dec axis is centered or not. If not, you
cold have the same problem that I do. I have sent an e-mail to Marj and
mentioned it so she is aware of the situation. Whether yours has the same
problem or not I am not sure, but you can check.

Third, when you are doing you alignment do not use the N-S-E-W buttons to
recenter the star if it is off to one side. Use the altitude and azimuth
adjusters on your mount for this.

Fourth, try using three star rather then two.

Hope this helps. For what it is worth, I have found the 900 to be a very
fine and stable mount. I got into astronomy in the early 1970's, and got
quite use to star hopping to find deep-sky objects. When computer controlled
telescopes first came out I did not think I would ever want one. However,
since I have now had a chance to use the GTO feature I realize that there
are many deep-sky objects, like some of the fainter NGC or IC objects, that
will be much easier to find and observe now. So I look forward to many years
of finding and observing with my AP scopes and mounts.

Clear Skies,

Eric Jamison


Re: Help with AP GTO on Parallax 125

Tim Khan
 

Mike,

Check if the setting on your hand controller is for
the proper mount. On the AP mounts you can set up the
hand controller for the 400, 600, 900, and 1200
mounts. Choose the correct one for your mount.

Remove your shims.

Alternate method for Othogonality:

Do a star drift alignment, get alignment very
accurate, center a star on the same hour as Polaris,
calibrate with that star, and slew to 90 degrees Dec
and same hour angle, check if setting circles agree
with computer. Doing this should prevent a change in
RA when slewing, just incase something is wrong with
the RA. Insure that you are pointing exactly 90
degrees in dec. If unsure of the Dec, pick a star and
manually slew using the mechanical setting circles to
90 degrees.

Rotate Mount with RA only. Look using medium to high
power through the scope. The stars in the field should
rotate perfectly around centered of the field, if not
your orthogonality is off, you can shim either ring to
bring the orthogonality in. Remember, you must be
polar aligned, and be point perfectly 90 degrees Dec.

Now slew to a star, like Regulus, recalibrate on the
star. Try slewing to other stars to see if it is
pointing properly.

I hope this helps.

Tim


--- Mike Mah <mikemah@attglobal.net> wrote:
AP 155 EDFS, AP rings on 16" Parallax Dovetail on
Parallax 125 with
AP GTO.

I have had this out several times now and have been
unable to get it
to point accurately - place and time setup are
correct.

On calibrating with Polaris, I have used Pollux, but
after several
iterations, whenever the mount slews back to Pollux,
it is always off
by a couple of degrees and I have to push the East
button to
re-center Pollux. When it slews to Polaris, Polaris
will be centered.
When I slew to another object, I can find it by
pressing the East
button for the same period of time.

I haven't checked for orthogonality using the method
in the manual -
I don't know which stars straddling the meridian to
use and I can't
stay up later to use Arcturus as per manual. On spec
and assuming a
one degree error in orthogonality, I shimmed up the
front rings by
one quarter inch tonight and it didn't seem to make
any difference.

Even when I recalibrate on Pollux and then slew to
Castor there is
still variable error of about half a degree.

Any ideas?

Mike Mah

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Help with AP GTO on Parallax 125

Mike Mah
 

AP 155 EDFS, AP rings on 16" Parallax Dovetail on Parallax 125 with
AP GTO.

I have had this out several times now and have been unable to get it
to point accurately - place and time setup are correct.

On calibrating with Polaris, I have used Pollux, but after several
iterations, whenever the mount slews back to Pollux, it is always off
by a couple of degrees and I have to push the East button to
re-center Pollux. When it slews to Polaris, Polaris will be centered.
When I slew to another object, I can find it by pressing the East
button for the same period of time.

I haven't checked for orthogonality using the method in the manual -
I don't know which stars straddling the meridian to use and I can't
stay up later to use Arcturus as per manual. On spec and assuming a
one degree error in orthogonality, I shimmed up the front rings by
one quarter inch tonight and it didn't seem to make any difference.

Even when I recalibrate on Pollux and then slew to Castor there is
still variable error of about half a degree.

Any ideas?

Mike Mah


Re: GPS enabled A-P goto mounts

Louis A. Mamakos <louie@...>
 

Once SA is gone, accuracy will be improved perhaps by one order of
magnitude to about 10m as compared to about 100m with SA enabled. Of
course, if you're not moving, you can average your position and do somewhat
better than that.

Unless you are moving, GPS won't be of any help in figuring out your
orientation. (Well, you can play some games if you have multiple
antennas and do relative carrier-phase measurements to figure out
your orientation with respect to a satellite, but this is somewhat
specialized and expensive.)

But even today with SA, knowing where you are within about 100m
and what time it is within a couple of hundred nanoseconds ain't
too shabby..

louie

The government announced today that the purposeful degradation of the
GPS (Global Positioning System) signals available to civilian users
will end tonight. With selective availability (SA) disabled, accuracy
will improve by a noticeable amount. Just as significantly, the
accuracy of the time signal will improve as well.

Wouldn't it be neat if I could tie my GPS unit to the controller of
the A-P mount? At the very least the mount would know right where
it's positioned (latitude/longitude) and the exact date and time. It
would also know very accurately the direction of true north.

As today's press release mentions, there are many improvements to GPS
in the works ranging from more satellites to new signals being
broadcast. Unless you're a U.S. taxpayer ;-), it's free, and will
probably stay that way. Imagine a portable equatorial mount that
polar aligns itself! I expect that it will happen sooner than we
think.

Paul


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Re: Tripod for 400 GTO

Chris Spratt
 

I don't have the Davis and Sanford aluminum tripod but do use the wooden one and
this
may be more suitable in the long run if you don't get a pier.

Marc Zukoff wrote:


I am anxiously awaiting my mount, but am wondering about the Davis
and Sanford aluminum tripod.Is it a good choice or is the wood tripod
a better one, or any other suggestions. i am planning on using a 4
inch refractor for now, but hope to also obtain a 5 inch refractor in
the next year.

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unique interests. eTour.com is surfing without searching.
And, it's FREE!
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