Modelling - can of worms


Gerald Sargent <sargentg@...>
 

In my initial submission starting the modelling topic, I should perhaps
have noted that I am one of those who has to set up each time, hence
the need for rapid polar alignment, and I mainly image, using either an
SBIG with self guide or the STV for autoguiding, both of which work well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting aligned
using 3 stars, and it had an inbuilt GPS feature which enabled me to
download time/location from an external GPS receiver. Both these are
great time savers and one could be reasonably well aligned with the
mount knowing exactly where it was and what time it was in a matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the crank
handle every time - well that is how I feel using the Mach1 with no
modelling or GPS facility, sure half an hour or so and I can get it
aligned but with a lot of "crank handle effort" that I have not had to
do with my last two mounts. The Mach1 tracks superby once aligned,
and it is a perfect mount for imaging - but it does lack the "self starter"
Gerald.


Poschinger Konstantin v. <KPoschinger@...>
 

Hi Gerald,

you must know, that if you setup a mount with the three star alignment
the mount is not really polar aligned! The computer only know how to
handle the misalignment. I setup my mach1 in the daylight with the sun
and a good spirit level within e error of 5 arc min only using the
park positions 1 and 2 and then pointing to the sun. In the night I
use the polar alignment scope and then with the ccd camera PoleAlignMax.

Konstantin


Konstantin v. Poschinger

Hammerichstr. 5
22605 Hamburg
040/8805747
01711983476

Am 02.09.2008 um 03:19 schrieb Gerald Sargent:

In my initial submission starting the modelling topic, I should
perhaps
have noted that I am one of those who has to set up each time, hence
the need for rapid polar alignment, and I mainly image, using either
an
SBIG with self guide or the STV for autoguiding, both of which work
well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting aligned
using 3 stars, and it had an inbuilt GPS feature which enabled me to
download time/location from an external GPS receiver. Both these are
great time savers and one could be reasonably well aligned with the
mount knowing exactly where it was and what time it was in a matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the crank
handle every time - well that is how I feel using the Mach1 with no
modelling or GPS facility, sure half an hour or so and I can get it
aligned but with a lot of "crank handle effort" that I have not had to
do with my last two mounts. The Mach1 tracks superby once aligned,
and it is a perfect mount for imaging - but it does lack the "self
starter"
Gerald.



Edd Weninger
 

I'm curious what information the Mach 1 needs from a GPS to enable
polar alignment? My AP1200 starts with a question "Location ?" and I
can select one of several pre-loaded. Time is kept internally with
sufficient accuracy. Is the Mach 1 different?

Edd Weninger

--- In ap-gto@..., Gerald Sargent <sargentg@...> wrote:

In my initial submission starting the modelling topic, I should
perhaps
have noted that I am one of those who has to set up each time, hence
the need for rapid polar alignment, and I mainly image, using
either an
SBIG with self guide or the STV for autoguiding, both of which work
well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting aligned
using 3 stars, and it had an inbuilt GPS feature which enabled me to
download time/location from an external GPS receiver. Both these are
great time savers and one could be reasonably well aligned with the
mount knowing exactly where it was and what time it was in a matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the
crank
handle every time - well that is how I feel using the Mach1 with no
modelling or GPS facility, sure half an hour or so and I can get it
aligned but with a lot of "crank handle effort" that I have not had
to
do with my last two mounts. The Mach1 tracks superby once aligned,
and it is a perfect mount for imaging - but it does lack the "self
starter"
Gerald.


Dean S
 

No, it is the same. Time can be synched with a computer though.

----- Original Message -----
From: "eddwen2001" <Eddwen@...>
To: <ap-gto@...>
Sent: Tuesday, September 02, 2008 10:22 AM
Subject: [ap-gto] Re: Modelling - can of worms


I'm curious what information the Mach 1 needs from a GPS to enable
polar alignment? My AP1200 starts with a question "Location ?" and I
can select one of several pre-loaded. Time is kept internally with
sufficient accuracy. Is the Mach 1 different?

Edd Weninger

--- In ap-gto@..., Gerald Sargent <sargentg@...> wrote:

In my initial submission starting the modelling topic, I should
perhaps
have noted that I am one of those who has to set up each time, hence
the need for rapid polar alignment, and I mainly image, using
either an
SBIG with self guide or the STV for autoguiding, both of which work
well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting aligned
using 3 stars, and it had an inbuilt GPS feature which enabled me to
download time/location from an external GPS receiver. Both these are
great time savers and one could be reasonably well aligned with the
mount knowing exactly where it was and what time it was in a matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the
crank
handle every time - well that is how I feel using the Mach1 with no
modelling or GPS facility, sure half an hour or so and I can get it
aligned but with a lot of "crank handle effort" that I have not had
to
do with my last two mounts. The Mach1 tracks superby once aligned,
and it is a perfect mount for imaging - but it does lack the "self
starter"
Gerald.


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Howard Hedlund
 

The Mach1GTO has the same servo drive system as the 900GTO and 1200GTO.
With the keypad firmware vewrsions of 4.xx, you have up to nine
locations that can be entered into the keypad's memory.



Mag. 7 skies!



Howard Hedlund

Astro-Physics, Inc.

815-282-1513

________________________________

From: ap-gto@... [mailto:ap-gto@...] On Behalf
Of eddwen2001
Sent: Tuesday, September 02, 2008 9:22 AM
To: ap-gto@...
Subject: [ap-gto] Re: Modelling - can of worms



I'm curious what information the Mach 1 needs from a GPS to enable
polar alignment? My AP1200 starts with a question "Location ?" and I
can select one of several pre-loaded. Time is kept internally with
sufficient accuracy. Is the Mach 1 different?

Edd Weninger

--- In ap-gto@... <mailto:ap-gto%40yahoogroups.com> , Gerald
Sargent <sargentg@...> wrote:

In my initial submission starting the modelling topic, I should
perhaps
have noted that I am one of those who has to set up each time, hence
the need for rapid polar alignment, and I mainly image, using
either an
SBIG with self guide or the STV for autoguiding, both of which work
well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting aligned
using 3 stars, and it had an inbuilt GPS feature which enabled me to
download time/location from an external GPS receiver. Both these are
great time savers and one could be reasonably well aligned with the
mount knowing exactly where it was and what time it was in a matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the
crank
handle every time - well that is how I feel using the Mach1 with no
modelling or GPS facility, sure half an hour or so and I can get it
aligned but with a lot of "crank handle effort" that I have not had
to
do with my last two mounts. The Mach1 tracks superby once aligned,
and it is a perfect mount for imaging - but it does lack the "self
starter"
Gerald.


Wiggins, Rick
 

Hi,
I would like to chime-in based on extensive use of the AP mounts in
both observatory and portable setups (ap 400, 600, 900, 1200, &
Mach1.
A. First GPS: There is no real need for GPS. You can get location
coordinates from any map or look them up on the internet ahead of
time. Once programmed in (less than one minute to program during
setup even in the dark), they can be called up in less than 1 sec
during the startup routine. Also, the exact location is not critical
to imaging.
B. Modeling: Modeling is great for very precise visual or imaging
setup work. It is not necessary for imaging as long as the mount can
get you within the FOV of the camera. Doing plate solves is far more
accurate than modeling for centering an image. If you are using
something smaller than an ST-10 and focal lenght over 3000mm,
modeling may be a real benefit. Modeling has nothing to do with
polar alignment. I do not use modeling with my AP mounts when doing
fully remote imaging. I only use plate solves. With an AP1200 mount,
1200mm FL scope and ST-10 (app 30 x 45 arc mins), my target is
always better than 15 arc mins from center (prior to plate solve)
over an entire nights imaging session of multiple targets ranging
across the entire sky and including multiple meridian flips.
C. Polar alignment: The AP mounts align very well with the polar
scope. I typically get mine better then 10 arc mins with the polar
scope. That is good enough for 20 min subframes at 1200mm FL on a
24mm x 36mm chip or camera. If you need better alignemnt, Pole-
Align_Max, PEMPro, or drift alignment can get you below 30 arc secs
with a time investment of 30 to 60 minutes.
D. Tracking for imaging: Here is a list of factors using my AP
mounts in descending order of importance (factors affecting tracing
performance). These are based on monitoring of my tracking logs:

1. Polar alignment with the polar scope. I find this takes less than
5 minutes for portable use assuming mount has been prealigned with
compass or better during daytime.
2. Exception rigid mechanical setup (based on separate guidescope
and N/A in OAG or internal guiding) with no snagging cables. This is
a one time setup for each optical configuration if done correctly.
3. Very well adjusted (dialed-in) guider parameters (min/max
corrections, aggressiveness, etc.) Note: McMillain's paper is the
best guide I have seen. This is a one time setup for each optical
configuration.
4. PEMPro or similar PEC corrections. This will reduce AP mounts
from factory performance (I have found between 5 to 2 arc secs PE)
to below 1 arc sec PE. This is basically a one time setup, although
it should probably be checked yearly or if tracking changes.
5. PEMPro, PoleAlignMax, drift align, or similar polar alignemtn
refinement. This is done during each setup if required.

I hope this data provides some help in understanding imaging
capabilities regarding tracking and alignment with AP mounts.
Thanks, Rick

--- In ap-gto@..., Gerald Sargent <sargentg@...> wrote:

In my initial submission starting the modelling topic, I should
perhaps
have noted that I am one of those who has to set up each time,
hence
the need for rapid polar alignment, and I mainly image, using
either an
SBIG with self guide or the STV for autoguiding, both of which
work well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting
aligned
using 3 stars, and it had an inbuilt GPS feature which enabled me
to
download time/location from an external GPS receiver. Both these
are
great time savers and one could be reasonably well aligned with the
mount knowing exactly where it was and what time it was in a matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the
crank
handle every time - well that is how I feel using the Mach1 with no
modelling or GPS facility, sure half an hour or so and I can get it
aligned but with a lot of "crank handle effort" that I have not
had to
do with my last two mounts. The Mach1 tracks superby once aligned,
and it is a perfect mount for imaging - but it does lack the "self
starter"
Gerald.


Kent Kirkley
 

In a message dated 9/2/08 4:49:56 PM, Eddwen@... writes:


I'm curious what information the Mach 1 needs from a GPS to enable
polar alignment?  My AP1200 starts with a question "Location ?" and I
can select one of several pre-loaded.  Time is kept internally with
sufficient accuracy.  Is the Mach 1 different?

Edd Weninger
No...!!!! It is identical.....and a GPS is not needed.

Kent Kirkley


**************
It's only a deal if it's where you want to go. Find
your travel deal here.

(http://information.travel.aol.com/deals?ncid=aoltrv00050000000047)


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


Edd Weninger
 

That's what I thought. I was wondering why Gerald felt the need to
futz with a GPS to polar align.

Edd Weninger

--- In ap-gto@..., "Howard" <howard@...> wrote:

The Mach1GTO has the same servo drive system as the 900GTO and
1200GTO.
With the keypad firmware vewrsions of 4.xx, you have up to nine
locations that can be entered into the keypad's memory.



Mag. 7 skies!



Howard Hedlund

Astro-Physics, Inc.

815-282-1513

________________________________

From: ap-gto@... [mailto:ap-gto@...] On
Behalf
Of eddwen2001
Sent: Tuesday, September 02, 2008 9:22 AM
To: ap-gto@...
Subject: [ap-gto] Re: Modelling - can of worms



I'm curious what information the Mach 1 needs from a GPS to enable
polar alignment? My AP1200 starts with a question "Location ?" and
I
can select one of several pre-loaded. Time is kept internally with
sufficient accuracy. Is the Mach 1 different?

Edd Weninger

--- In ap-gto@... <mailto:ap-gto%40yahoogroups.com> ,
Gerald
Sargent <sargentg@> wrote:

In my initial submission starting the modelling topic, I should
perhaps
have noted that I am one of those who has to set up each time,
hence
the need for rapid polar alignment, and I mainly image, using
either an
SBIG with self guide or the STV for autoguiding, both of which
work
well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting
aligned
using 3 stars, and it had an inbuilt GPS feature which enabled me
to
download time/location from an external GPS receiver. Both these
are
great time savers and one could be reasonably well aligned with
the
mount knowing exactly where it was and what time it was in a
matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility
which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the
crank
handle every time - well that is how I feel using the Mach1 with
no
modelling or GPS facility, sure half an hour or so and I can get
it
aligned but with a lot of "crank handle effort" that I have not
had
to
do with my last two mounts. The Mach1 tracks superby once aligned,
and it is a perfect mount for imaging - but it does lack
the "self
starter"
Gerald.




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


Christopher Vedeler L.Ac. <vedeler@...>
 

I never understood the hoopla about GPS built into a mount. I already
have a GPS and I can input the coordinates in just a few minutes. Not
that I bother. Unless I'm observing more than a few hundred miles from
home I don't even bother changing the Lat and Long with my mount. It
makes no difference as far as polar alignment, tracking or pointing that
I can tell.

The ability of the mount to compensate for polar alignment error and
model the sky like much lesser mounts can do would be a big plus in my
opinion however. That and a wireless hand controller... :-D And lets
not forget going with USB native to the mount instead of the dinosaur
RS-232 serial.

Chris Vedeler


Ladislav Nemec <nemecl@...>
 

Good summary of essential conditions for imaging. I just somewhat disagree
with the statement that 'modeling has nothing to do with polar alignment'.
It depends on the modeling algorithm. Gemini modeling compensates for polar
misalignment quite well - the question is, of course, whether modeling
should substitute for a good polar alignment. Not for permanent installation
but it may be handy for transient installation - building a model that
includes compensation for minor polar misalignment may be faster than very
precise polar alignment in the field.



Also, I still have to achieve significant reduction of tracking errors (some
of them non-periodic on my Losmandy G11 and thus not possible to correct by
PEC) that, at this time, are typically less than 8 arcsecs peak-peak. AP
mounts, perhaps, do not have these non-periodic errors - they are created
(general belief) by mechanical imprecisions.

-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...] On Behalf Of
Rick Wiggins
Sent: Tuesday, September 02, 2008 10:37 AM
To: ap-gto@...
Subject: [ap-gto] Re: Modelling - can of worms



Hi,
I would like to chime-in based on extensive use of the AP mounts in
both observatory and portable setups (ap 400, 600, 900, 1200, &
Mach1.
A. First GPS: There is no real need for GPS. You can get location
coordinates from any map or look them up on the internet ahead of
time. Once programmed in (less than one minute to program during
setup even in the dark), they can be called up in less than 1 sec
during the startup routine. Also, the exact location is not critical
to imaging.
B. Modeling: Modeling is great for very precise visual or imaging
setup work. It is not necessary for imaging as long as the mount can
get you within the FOV of the camera. Doing plate solves is far more
accurate than modeling for centering an image. If you are using
something smaller than an ST-10 and focal lenght over 3000mm,
modeling may be a real benefit. Modeling has nothing to do with
polar alignment. I do not use modeling with my AP mounts when doing
fully remote imaging. I only use plate solves. With an AP1200 mount,
1200mm FL scope and ST-10 (app 30 x 45 arc mins), my target is
always better than 15 arc mins from center (prior to plate solve)
over an entire nights imaging session of multiple targets ranging
across the entire sky and including multiple meridian flips.
C. Polar alignment: The AP mounts align very well with the polar
scope. I typically get mine better then 10 arc mins with the polar
scope. That is good enough for 20 min subframes at 1200mm FL on a
24mm x 36mm chip or camera. If you need better alignemnt, Pole-
Align_Max, PEMPro, or drift alignment can get you below 30 arc secs
with a time investment of 30 to 60 minutes.
D. Tracking for imaging: Here is a list of factors using my AP
mounts in descending order of importance (factors affecting tracing
performance). These are based on monitoring of my tracking logs:

1. Polar alignment with the polar scope. I find this takes less than
5 minutes for portable use assuming mount has been prealigned with
compass or better during daytime.
2. Exception rigid mechanical setup (based on separate guidescope
and N/A in OAG or internal guiding) with no snagging cables. This is
a one time setup for each optical configuration if done correctly.
3. Very well adjusted (dialed-in) guider parameters (min/max
corrections, aggressiveness, etc.) Note: McMillain's paper is the
best guide I have seen. This is a one time setup for each optical
configuration.
4. PEMPro or similar PEC corrections. This will reduce AP mounts
from factory performance (I have found between 5 to 2 arc secs PE)
to below 1 arc sec PE. This is basically a one time setup, although
it should probably be checked yearly or if tracking changes.
5. PEMPro, PoleAlignMax, drift align, or similar polar alignemtn
refinement. This is done during each setup if required.

I hope this data provides some help in understanding imaging
capabilities regarding tracking and alignment with AP mounts.
Thanks, Rick

--- In ap-gto@yahoogroups. <mailto:ap-gto%40yahoogroups.com> com, Gerald
Sargent <sargentg@...> wrote:

In my initial submission starting the modelling topic, I should
perhaps
have noted that I am one of those who has to set up each time,
hence
the need for rapid polar alignment, and I mainly image, using
either an
SBIG with self guide or the STV for autoguiding, both of which
work well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting
aligned
using 3 stars, and it had an inbuilt GPS feature which enabled me
to
download time/location from an external GPS receiver. Both these
are
great time savers and one could be reasonably well aligned with the
mount knowing exactly where it was and what time it was in a matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the
crank
handle every time - well that is how I feel using the Mach1 with no
modelling or GPS facility, sure half an hour or so and I can get it
aligned but with a lot of "crank handle effort" that I have not
had to
do with my last two mounts. The Mach1 tracks superby once aligned,
and it is a perfect mount for imaging - but it does lack the "self
starter"
Gerald.


Poschinger Konstantin v. <KPoschinger@...>
 

Hello Chris,

you should not forget if you model the sky you will get star rotating
in long time images!!

Konstantin v. Poschinger

Hammerichstr. 5
22605 Hamburg
040/8805747
01711983476

Am 02.09.2008 um 23:06 schrieb Christopher Vedeler L.Ac.:

I never understood the hoopla about GPS built into a mount. I already
have a GPS and I can input the coordinates in just a few minutes. Not
that I bother. Unless I'm observing more than a few hundred miles from
home I don't even bother changing the Lat and Long with my mount. It
makes no difference as far as polar alignment, tracking or pointing
that
I can tell.

The ability of the mount to compensate for polar alignment error and
model the sky like much lesser mounts can do would be a big plus in my
opinion however. That and a wireless hand controller... :-D And lets
not forget going with USB native to the mount instead of the dinosaur
RS-232 serial.

Chris Vedeler





Ladislav Nemec <nemecl@...>
 

The rotation is not really related to modeling but to polar misalignment.
Some modeling algorithms (see my previous post) can 'compensate' for polar
misalignment but not at all of the intrinsic image rotation - in that sense
modeling may not be such a great idea since it can mask polar misalignment.



LN

-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...] On Behalf Of
Poschinger Konstantin v.
Sent: Tuesday, September 02, 2008 3:44 PM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Modelling - can of worms



Hello Chris,

you should not forget if you model the sky you will get star rotating
in long time images!!

Konstantin v. Poschinger

Hammerichstr. 5
22605 Hamburg
040/8805747
01711983476

Am 02.09.2008 um 23:06 schrieb Christopher Vedeler L.Ac.:

I never understood the hoopla about GPS built into a mount. I already
have a GPS and I can input the coordinates in just a few minutes. Not
that I bother. Unless I'm observing more than a few hundred miles from
home I don't even bother changing the Lat and Long with my mount. It
makes no difference as far as polar alignment, tracking or pointing
that
I can tell.

The ability of the mount to compensate for polar alignment error and
model the sky like much lesser mounts can do would be a big plus in my
opinion however. That and a wireless hand controller... :-D And lets
not forget going with USB native to the mount instead of the dinosaur
RS-232 serial.

Chris Vedeler





Joel
 

AP modeling debaters,

A couple of years ago there was the same debate on this forum. I
suggested then that given AP's status as the state of the art mount
manufacturer, its mount control software should be state of the art.
Other manufacturers have included both modeling and GPS in their
mount control software for years. I have found both to be convenient
for all scopes and for non-orthoganal scopes more than helpful. I am
presently running a G-11/Gemini and an AP900GTO in my observatory. No
doubt that the AP900 is more robust and more accurate in its
tracking, but the Gemini modeling and polar alignment routine would
be a welcome addition to the AP900 with my slightly non-orthogonal C-
14. GPS and modeling are great when you set up in the field. For
those "purists" who think that GPS and modeling are not needed, you
can still do it all manually. I continue to vote for adding both
these features to the AP mount control software and I am pleased to
see that AP is working on modeling. I am looking forward to the
upgrade.

Joel

--- In ap-gto@..., "Ladislav Nemec" <nemecl@...> wrote:

The rotation is not really related to modeling but to polar
misalignment.
Some modeling algorithms (see my previous post) can 'compensate'
for polar
misalignment but not at all of the intrinsic image rotation - in
that sense
modeling may not be such a great idea since it can mask polar
misalignment.



LN



-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...] On
Behalf Of
Poschinger Konstantin v.
Sent: Tuesday, September 02, 2008 3:44 PM
To: ap-gto@...
Subject: Re: [ap-gto] Re: Modelling - can of worms



Hello Chris,

you should not forget if you model the sky you will get star
rotating
in long time images!!

Konstantin v. Poschinger

Hammerichstr. 5
22605 Hamburg
040/8805747
01711983476

Am 02.09.2008 um 23:06 schrieb Christopher Vedeler L.Ac.:

I never understood the hoopla about GPS built into a mount. I
already
have a GPS and I can input the coordinates in just a few minutes.
Not
that I bother. Unless I'm observing more than a few hundred miles
from
home I don't even bother changing the Lat and Long with my mount.
It
makes no difference as far as polar alignment, tracking or
pointing
that
I can tell.

The ability of the mount to compensate for polar alignment error
and
model the sky like much lesser mounts can do would be a big plus
in my
opinion however. That and a wireless hand controller... :-D And
lets
not forget going with USB native to the mount instead of the
dinosaur
RS-232 serial.

Chris Vedeler

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


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





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Kent Kirkley
 

In a message dated 9/2/08 9:51:37 PM, jeguthals@... writes:


For
those "purists" who think that GPS and modeling are not needed, you
can still do it all manually. I continue to vote for adding both
these features to the AP mount control software and I am pleased to
see that AP is working on modeling. I am looking forward to the
upgrade.
How many locations do people image from? One, two, four, seven.....how about
9???
I have currently stored in my AP 'locations' five places I sometimes image
from.
All I have to do is select one. A built in GPS is not needed.

As far as modeling is concerned....with a mount like the AP1200GTO that I
use....I haven't found it necessary. While unguided imaging may seem to be
necessary for some........simply guiding works so well as to render the effort
less than appealing. I think you will find that all accomplished imagers guide
their exposures.....either by built in or external guiders, off axis guiders or
guide scopes.

Kent Kirkley


**************
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Christopher Vedeler L.Ac. <vedeler@...>
 

Kent,

Having a mount system that is forgiving of polar alignment error,
non-orthaginal orientation and even atmospheric refraction just makes
things eaiser. The technology is out there, it is relativly cheap and
lesser mounts are doing it. Why not AP? After having worked with the
Atlas EQ-G and seeing what software could make mediocire hardware do, I
can't help imagine how powerful it would be to have top of the line
hardware under the same type of software control.

Chris Vedeler


Wiggins, Rick
 

Hi,
I don't want to get into a large debate, but would like to point out
what I believe, for some people, may be a misconception regarding
the definitions of modeling vs. polar alignment.

1. Polar alignment of the mount involves physically aligning the
mount with the polar aixs. This can only be achieved by physically
adjusting the azimuth and altitude of the mount. Any variation from
perfect alignment means that the FOV will rotate relative to the
polar axis by an amount proportional to the polar alignment error
(commonaly called drift by imagers). The image train non-
orthogonality with respect to the polar axis will also drive the
drift error to be higher proportiuonal to the non-orthogonality.
There are various programs such as PEMPro and PoleAlignMax that can
calculate and provide quantitative feedback of the polar alignment
error to the user; however, the user still has to manually move the
mount in azimuth and altitude to better perform polar alignment.

2. Modeling is a common term given to algorithms that calculate
various error terms. Modeling programs "subtract" these error terms
from the non-modeled calculated position of targets to allow the
mount to correctly position the telescope so that the target is
centered in the FOV. These modeling programs can compensate for
refraction, non-orthogonality of the scope relative to the mount,
and polar mis-alignment as well as other terms. They perform this
compensation for the pointing or initial pointing placement of the
telescope on the target. They will do an excellent job of having the
telescope go exactly to the center of the desired FOV following a
slew.

Understandig the brief definitions above allows one to understand
how these terms come into play while imaging. Although the modeling
program will properly position the scope following a slew; once the
tracking begins, the FOV will rotate relative to the tracking star
based on the degree of polar mis-alignment. The modeling will not
help this. In addition, if polar alignment is significantly off, it
will also affect the ability of the guider to correct all the error
terms including periodic error and polar mis-alignment. This is why
I say that modeling is separate from polar alignment. It certainly
can help with pointing, but has no effect on guiding and tracking.

I hope this helps clarify the issue.
Thanks, Rick

--- In ap-gto@..., "Ladislav Nemec" <nemecl@...> wrote:

Good summary of essential conditions for imaging. I just somewhat
disagree
with the statement that 'modeling has nothing to do with polar
alignment'.
It depends on the modeling algorithm. Gemini modeling compensates
for polar
misalignment quite well - the question is, of course, whether
modeling
should substitute for a good polar alignment. Not for permanent
installation
but it may be handy for transient installation - building a model
that
includes compensation for minor polar misalignment may be faster
than very
precise polar alignment in the field.



Also, I still have to achieve significant reduction of tracking
errors (some
of them non-periodic on my Losmandy G11 and thus not possible to
correct by
PEC) that, at this time, are typically less than 8 arcsecs peak-
peak. AP
mounts, perhaps, do not have these non-periodic errors - they are
created
(general belief) by mechanical imprecisions.







-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...] On
Behalf Of
Rick Wiggins
Sent: Tuesday, September 02, 2008 10:37 AM
To: ap-gto@...
Subject: [ap-gto] Re: Modelling - can of worms



Hi,
I would like to chime-in based on extensive use of the AP mounts
in
both observatory and portable setups (ap 400, 600, 900, 1200, &
Mach1.
A. First GPS: There is no real need for GPS. You can get location
coordinates from any map or look them up on the internet ahead of
time. Once programmed in (less than one minute to program during
setup even in the dark), they can be called up in less than 1 sec
during the startup routine. Also, the exact location is not
critical
to imaging.
B. Modeling: Modeling is great for very precise visual or imaging
setup work. It is not necessary for imaging as long as the mount
can
get you within the FOV of the camera. Doing plate solves is far
more
accurate than modeling for centering an image. If you are using
something smaller than an ST-10 and focal lenght over 3000mm,
modeling may be a real benefit. Modeling has nothing to do with
polar alignment. I do not use modeling with my AP mounts when
doing
fully remote imaging. I only use plate solves. With an AP1200
mount,
1200mm FL scope and ST-10 (app 30 x 45 arc mins), my target is
always better than 15 arc mins from center (prior to plate solve)
over an entire nights imaging session of multiple targets ranging
across the entire sky and including multiple meridian flips.
C. Polar alignment: The AP mounts align very well with the polar
scope. I typically get mine better then 10 arc mins with the polar
scope. That is good enough for 20 min subframes at 1200mm FL on a
24mm x 36mm chip or camera. If you need better alignemnt, Pole-
Align_Max, PEMPro, or drift alignment can get you below 30 arc
secs
with a time investment of 30 to 60 minutes.
D. Tracking for imaging: Here is a list of factors using my AP
mounts in descending order of importance (factors affecting
tracing
performance). These are based on monitoring of my tracking logs:

1. Polar alignment with the polar scope. I find this takes less
than
5 minutes for portable use assuming mount has been prealigned with
compass or better during daytime.
2. Exception rigid mechanical setup (based on separate guidescope
and N/A in OAG or internal guiding) with no snagging cables. This
is
a one time setup for each optical configuration if done correctly.
3. Very well adjusted (dialed-in) guider parameters (min/max
corrections, aggressiveness, etc.) Note: McMillain's paper is the
best guide I have seen. This is a one time setup for each optical
configuration.
4. PEMPro or similar PEC corrections. This will reduce AP mounts
from factory performance (I have found between 5 to 2 arc secs PE)
to below 1 arc sec PE. This is basically a one time setup,
although
it should probably be checked yearly or if tracking changes.
5. PEMPro, PoleAlignMax, drift align, or similar polar alignemtn
refinement. This is done during each setup if required.

I hope this data provides some help in understanding imaging
capabilities regarding tracking and alignment with AP mounts.
Thanks, Rick

--- In ap-gto@yahoogroups. <mailto:ap-gto%40yahoogroups.com> com,
Gerald
Sargent <sargentg@> wrote:

In my initial submission starting the modelling topic, I should
perhaps
have noted that I am one of those who has to set up each time,
hence
the need for rapid polar alignment, and I mainly image, using
either an
SBIG with self guide or the STV for autoguiding, both of which
work well,
However both need that the mount be reasonably aligned. My
Gemini on a Losmandy G8 had an excellent routine for getting
aligned
using 3 stars, and it had an inbuilt GPS feature which enabled
me
to
download time/location from an external GPS receiver. Both these
are
great time savers and one could be reasonably well aligned with
the
mount knowing exactly where it was and what time it was in a
matter
of a few minutes.
With my next mount, a Vixen Atlux, a really excellent mount I
had the SS2KPC controller which did not have the GPS facility
which
meant a few minutes "lost", it did however have a very good polar
alignment facility using three stars and one could be very
quickly
sufficiently well aligned for imaging.
One gets used to taking advantages of advanced routines,
image trying to use a car in a city without a self starter - the
crank
handle every time - well that is how I feel using the Mach1 with
no
modelling or GPS facility, sure half an hour or so and I can get
it
aligned but with a lot of "crank handle effort" that I have not
had to
do with my last two mounts. The Mach1 tracks superby once
aligned,
and it is a perfect mount for imaging - but it does lack
the "self
starter"
Gerald.






rags_the_cat
 

Chris

As you point out modeling is a software patch to fix the short
comings of mediocre equipment. Adding it to my AP900 would be sorta
like putting patches on your tires when there's no leak. Sky
modeling essentially makes an empirical map of the effective, or
distorted sky to offset repetitive or systematic errors it can infer
from an actual setup. AP's approach short circuits the need for much
of what modeling can deliver. The only issue I see that modeling can
possibly help with would be atmospheric refraction or if I had
noticible tube flexure. Both of which I consider negligible for my
setup. The sky model that an AP mount would generate for it's own
use would be very close to the actual sky. It already has that model
in it. I for one would want AP to continue offering a modeling free system.

Jerry


9/3/2008, you wrote:

Kent,

Having a mount system that is forgiving of polar alignment error,
non-orthaginal orientation and even atmospheric refraction just makes
things eaiser. The technology is out there, it is relativly cheap and
lesser mounts are doing it. Why not AP? After having worked with the
Atlas EQ-G and seeing what software could make mediocire hardware do, I
can't help imagine how powerful it would be to have top of the line
hardware under the same type of software control.

Chris Vedeler




planetary_hunter
 

Modeling would always need to be an option that can be turned on or
off. When off, the mount would act exactly as it does now.

Whiling imaging I would want the modeling off and while visual
observing I would want the model on.

Bryan

--- In ap-gto@..., "Jerry A. Wilson" <JerryAWilson@...>
wrote:

Chris

As you point out modeling is a software patch to fix the short
comings of mediocre equipment. Adding it to my AP900 would be
sorta
like putting patches on your tires when there's no leak. Sky
modeling essentially makes an empirical map of the effective, or
distorted sky to offset repetitive or systematic errors it can
infer
from an actual setup. AP's approach short circuits the need for
much
of what modeling can deliver. The only issue I see that modeling
can
possibly help with would be atmospheric refraction or if I had
noticible tube flexure. Both of which I consider negligible for my
setup. The sky model that an AP mount would generate for it's own
use would be very close to the actual sky. It already has that
model
in it. I for one would want AP to continue offering a modeling
free system.

Jerry


Dean S
 

The modeling would have no effect on tracking or guiding, only on the GOTO.
So turning it on or off would make no difference while imaging.

----- Original Message -----
From: "Bryan Henry" <behenry10@...>
To: <ap-gto@...>
Sent: Wednesday, September 03, 2008 2:23 PM
Subject: [ap-gto] Re: Modelling - can of worms


Modeling would always need to be an option that can be turned on or
off. When off, the mount would act exactly as it does now.

Whiling imaging I would want the modeling off and while visual
observing I would want the model on.

Bryan

--- In ap-gto@..., "Jerry A. Wilson" <JerryAWilson@...>
wrote:

Chris

As you point out modeling is a software patch to fix the short
comings of mediocre equipment. Adding it to my AP900 would be
sorta
like putting patches on your tires when there's no leak. Sky
modeling essentially makes an empirical map of the effective, or
distorted sky to offset repetitive or systematic errors it can
infer
from an actual setup. AP's approach short circuits the need for
much
of what modeling can deliver. The only issue I see that modeling
can
possibly help with would be atmospheric refraction or if I had
noticible tube flexure. Both of which I consider negligible for my
setup. The sky model that an AP mount would generate for it's own
use would be very close to the actual sky. It already has that
model
in it. I for one would want AP to continue offering a modeling
free system.

Jerry

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Tho Dinh
 

Speaking of the Gemini, it had a Polar Axis Correction feature which I found
very helpful for refining polar alignment. After building a decent model,
centering on a star near the intersection of the meridian and celestial
equator, and selecting this feature, the mount would slew the scope such
that by adjusting in azimuth and altitude to re-center the star, you would
bring the mount closer to perfect polar alignment. This is similar to Pole
Align Max, except that it also took into account other errors in the system
such as tube flexure, non-orthogonality, etc. I would certainly welcome a
similar feature in the keypad software and is an example of how modelling
can be beneficial to those of us that image.

-Tho

On Tue, Sep 2, 2008 at 7:51 PM, Joel <jeguthals@...> wrote:

AP modeling debaters,

A couple of years ago there was the same debate on this forum. I
suggested then that given AP's status as the state of the art mount
manufacturer, its mount control software should be state of the art.
Other manufacturers have included both modeling and GPS in their
mount control software for years. I have found both to be convenient
for all scopes and for non-orthoganal scopes more than helpful. I am
presently running a G-11/Gemini and an AP900GTO in my observatory. No
doubt that the AP900 is more robust and more accurate in its
tracking, but the Gemini modeling and polar alignment routine would
be a welcome addition to the AP900 with my slightly non-orthogonal C-
14. GPS and modeling are great when you set up in the field. For
those "purists" who think that GPS and modeling are not needed, you
can still do it all manually. I continue to vote for adding both
these features to the AP mount control software and I am pleased to
see that AP is working on modeling. I am looking forward to the
upgrade.

Joel