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Re: Polar Align Assist and Polar Axis Correction


Feb 7 8:13 PM

 


----------------------------

#2621 Feb 7 8:13 PM

Can someone provide more detailed instructions on using the Polar

Align Assist feature on the Gemini? The instructions refer to using

the altitude/azimuth adjustments to center the two stars but also

imply that it's OK to use the hand paddle (centering) as well. My

inclination is to use the azimuth and altitude adjustments only to

center Polaris and use the hand paddle only to center the other star

(the alignment star).



Thanks!

Steve



----------------------------

#3476 Apr 2, 2001

I've noticed a couple of postings regarding Polar Align Assist

recently so I thought I would step in and post a few comments.

Hopefully, Rene will step in and correct me if I say something dumb.

I've been intending to do a writeup of polar alignment, in general,

as a starting point for Rene but I've been very busy lately. In the

meantime, I'll share what I've learned about the Polar Align Assist

feature.



Polar Align Assist

-------------------

In a nutshell, I think most people should avoid this feature and use

a polar alignment scope and/or the drift method. The polar align

assist feature requires more preparation and care than you might

suspect. As it is currently implemented (v1.x), Polar align assist

does NOT adjust modelling parameters with each "pass". Nor does it

following any other particularly "intelligent" algorithm. Polar

align assist merely does an initial alignment every time you hit the

menu button after the mount slews to one of the two stars.

Basically, the polar align assist is a time saving feature - you

don't have to press all the buttons you normally would to do a GOTO

and an Initial Alignment.



I am not aware of any "tested" procedure for using the polar align

assist. The challenge is to devise an algorithm which is reliable

and efficient (like the drift method). Because polar align assist

does an initial align at each step, any algorithm for polar aligning

requires that the optical axis be well collimated with the RA axis

and that the RA axis be perpendicular to the DEC axis. If you can't

assure yourself that your telescope and mount meet these two criteria

then I would not try to use the polar align assist feature.

Furthermore, I would not try to use the polar align assist if your

telescope shows any tendency for "mirror-flop" or other optical-

mechanical aberrations while slewing across large parts of the sky.



I believe the following procedure should work if the telescope and

mount meet the colimation and stability requirements. But, I haven't

had the time and clear weather to verify this procedure yet. I

welcome anyone to try this procedure and let us know how it works.

If I get some clear skies again, I'll try it myself.



0) Begin by getting the polar alignment as close as you can with your

eye and/or a polar alignment scope.



1) Star 1: Choose a star near the celestial equator



2) Star 2: Choose a star near the celestial pole



3) Aligning on Star 1 (equatorial)

Use the hand controller to center the star and hit menu (initial

align)



4) Aligning on Star 2 (polar)

Use only the altitude and azimuth adjustments of the RA axis to

center the star as well as possible, then hit menu.



5) Aligning on Star 1 (again)

Use the hand controller to center the star and hit menu.



6) Aligning on Star 2 (again)

Hopefully, this slew would up closer to the polar star and you center

it with minor adjustments to the altitude and azimuth of the RA axis.



... repeat steps 5 and 6 until you are either happy with the

alignment or tired.



Steve



----------------------------

#3519 Apr 5, 2001

You don't state what system you're using. The system you describe

below is EXACTLY the NGC Max polar alignment algorithm (for

digital setting circles, not go-to) where you

do a 1-star alignment, go to where the computer "thinks" polaris

is, then ADJUSTING THE MOUNT (not the ota) center polaris in the

FOV, enter polaris location, then return to original star and

align on it again.



This system can't work, I don't think, if the optical axis is

grossly off the RA axis, and if after repeating hte procedure several

times you're not "dead on," it most likely is due to lack of

agreement between the tube and the mount as to where N is.



But I'll be working on this tonight.



greg mpwe;;





--- In Losmandy_users@y..., stevepr@a... wrote:

> I've noticed a couple of postings regarding Polar Align Assist

> recently so I thought I would step in and post a few comments.

> Hopefully, Rene will step in and correct me if I say something

dumb.

> I've been intending to do a writeup of polar alignment, in general,

> as a starting point for Rene but I've been very busy lately. In

the

> meantime, I'll share what I've learned about the Polar Align Assist

> feature.

>

> Polar Align Assist

> -------------------

> In a nutshell, I think most people should avoid this feature and

use

> a polar alignment scope and/or the drift method. The polar align

> assist feature requires more preparation and care than you might

> suspect. As it is currently implemented (v1.x), Polar align assist

> does NOT adjust modelling parameters with each "pass". Nor does it

> following any other particularly "intelligent" algorithm. Polar

> align assist merely does an initial alignment every time you hit

the

> menu button after the mount slews to one of the two stars.

> Basically, the polar align assist is a time saving feature - you

> don't have to press all the buttons you normally would to do a GOTO

> and an Initial Alignment.

>

> I am not aware of any "tested" procedure for using the polar align

> assist. The challenge is to devise an algorithm which is reliable

> and efficient (like the drift method). Because polar align assist

> does an initial align at each step, any algorithm for polar

aligning

> requires that the optical axis be well collimated with the RA axis

> and that the RA axis be perpendicular to the DEC axis. If you

can't

> assure yourself that your telescope and mount meet these two

criteria

> then I would not try to use the polar align assist feature.

> Furthermore, I would not try to use the polar align assist if your

> telescope shows any tendency for "mirror-flop" or other optical-

> mechanical aberrations while slewing across large parts of the sky.

>

> I believe the following procedure should work if the telescope and

> mount meet the colimation and stability requirements. But, I

haven't

> had the time and clear weather to verify this procedure yet. I

> welcome anyone to try this procedure and let us know how it works.



> If I get some clear skies again, I'll try it myself.

>

> 0) Begin by getting the polar alignment as close as you can with

your

> eye and/or a polar alignment scope.

>

> 1) Star 1: Choose a star near the celestial equator

>

> 2) Star 2: Choose a star near the celestial pole

>

> 3) Aligning on Star 1 (equatorial)

> Use the hand controller to center the star and hit menu (initial

> align)

>

> 4) Aligning on Star 2 (polar)

> Use only the altitude and azimuth adjustments of the RA axis to

> center the star as well as possible, then hit menu.

>

> 5) Aligning on Star 1 (again)

> Use the hand controller to center the star and hit menu.

>

> 6) Aligning on Star 2 (again)

> Hopefully, this slew would up closer to the polar star and you

center

> it with minor adjustments to the altitude and azimuth of the RA

axis.

>

> ... repeat steps 5 and 6 until you are either happy with the

> alignment or tired.

>

> Steve







----------------------------

#3523 Apr 6, 2001

comments below... --- In Losmandy_users@y..., gnowell@w... wrote:

> You don't state what system you're using. The system you describe

> below is EXACTLY the NGC Max polar alignment algorithm (for

> digital setting circles, not go-to) where you

> do a 1-star alignment, go to where the computer "thinks" polaris

> is, then ADJUSTING THE MOUNT (not the ota) center polaris in the

> FOV, enter polaris location, then return to original star and

> align on it again.

>

I'm not familiar with the NGC max but it makes sense to me that the

same algorithm would work for any 1-star alignment system (GEMINI,

NGC Max, or just about any DSC or GOTO system).



> This system can't work, I don't think, if the optical axis is

> grossly off the RA axis, and if after repeating hte procedure

several

> times you're not "dead on," it most likely is due to lack of

> agreement between the tube and the mount as to where N is.

>

Yes, this is what I meant when I said that the Optical axis should be

well colimated with the RA axis. Also, note that mirror-flop (common

large schmidt-cassegrains) will also limit accuracy.



Steve



>

>

>

> --- In Losmandy_users@y..., stevepr@a... wrote:

> > I've noticed a couple of postings regarding Polar Align Assist

> > recently so I thought I would step in and post a few comments.

> > Hopefully, Rene will step in and correct me if I say something

> dumb.

> > I've been intending to do a writeup of polar alignment, in

general,

> > as a starting point for Rene but I've been very busy lately. In

> the

> > meantime, I'll share what I've learned about the Polar Align

Assist

> > feature.

> >

> > Polar Align Assist

> > -------------------

> > In a nutshell, I think most people should avoid this feature and

> use

> > a polar alignment scope and/or the drift method. The polar align

> > assist feature requires more preparation and care than you might

> > suspect. As it is currently implemented (v1.x), Polar align

assist

> > does NOT adjust modelling parameters with each "pass". Nor does

it

> > following any other particularly "intelligent" algorithm. Polar

> > align assist merely does an initial alignment every time you hit

> the

> > menu button after the mount slews to one of the two stars.

> > Basically, the polar align assist is a time saving feature - you

> > don't have to press all the buttons you normally would to do a

GOTO

> > and an Initial Alignment.

> >

> > I am not aware of any "tested" procedure for using the polar

align

> > assist. The challenge is to devise an algorithm which is

reliable

> > and efficient (like the drift method). Because polar align

assist

> > does an initial align at each step, any algorithm for polar

> aligning

> > requires that the optical axis be well collimated with the RA

axis

> > and that the RA axis be perpendicular to the DEC axis. If you

> can't

> > assure yourself that your telescope and mount meet these two

> criteria

> > then I would not try to use the polar align assist feature.

> > Furthermore, I would not try to use the polar align assist if

your

> > telescope shows any tendency for "mirror-flop" or other optical-

> > mechanical aberrations while slewing across large parts of the

sky.

> >

> > I believe the following procedure should work if the telescope

and

> > mount meet the colimation and stability requirements. But, I

> haven't

> > had the time and clear weather to verify this procedure yet. I

> > welcome anyone to try this procedure and let us know how it

works.

>

> > If I get some clear skies again, I'll try it myself.

> >

> > 0) Begin by getting the polar alignment as close as you can with

> your

> > eye and/or a polar alignment scope.

> >

> > 1) Star 1: Choose a star near the celestial equator

> >

> > 2) Star 2: Choose a star near the celestial pole

> >

> > 3) Aligning on Star 1 (equatorial)

> > Use the hand controller to center the star and hit menu (initial

> > align)

> >

> > 4) Aligning on Star 2 (polar)

> > Use only the altitude and azimuth adjustments of the RA axis to

> > center the star as well as possible, then hit menu.

> >

> > 5) Aligning on Star 1 (again)

> > Use the hand controller to center the star and hit menu.

> >

> > 6) Aligning on Star 2 (again)

> > Hopefully, this slew would up closer to the polar star and you

> center

> > it with minor adjustments to the altitude and azimuth of the RA

> axis.

> >

> > ... repeat steps 5 and 6 until you are either happy with the

> > alignment or tired.

> >

> > Steve



----------------------------

#9334 Mar 26, 2002

My G11/Gemini arrives in about 2 weeks, so I've been boning up on the

Gemini manual...I guess that makes me a newbie :>)



Anywho, I'm reading the section on Telescope Alignment and I have a

procedural question concerning Polar Align Assist. The manual is

clear that this menu item is not available until you do the Initial

Alignment. What is not clear is whether you should do this

immediately after Initial Alignment, or after doing several

Additional Alignments. The manual states that the first two

Additional Alignments are used as an estimate of the polar axis

alignment. My question is, do I want Gemini to calculate this model

as a necessary precursor to Polar Align Assist, or does Polar Align

Assist ignore the model and point to where the star (e.g. Polaris)

should be for the date, time, location, etc?



Another confusing statement in the manual is: "You can also use the

HC for additional corrections." If I'm doing a Polar Alignment why

would I want to make corrections with the hand controller? If I'm

being a dunderhead here, just say so ;-)



My next question relates to the accuracy of this method. How

accurate can I get with this? Will I still need to do drift

alignment if I'm doing imaging? How many iterations are required?

Does it converge, and how fast?



Any of you experienced users use this method? Is it any good?



Thankx in advance, Frank







----------------------------

#9336 Mar 26, 2002

--- In Losmandy_users@y..., "starcrazed28056" frankb02@b...> wrote: > My G11/Gemini arrives in about 2 weeks, so I've been boning up on

the > Gemini manual...I guess that makes me a newbie :>)



There are a lot of us out here. :-)

> Anywho, I'm reading the section on Telescope Alignment and I have a

> procedural question concerning Polar Align Assist. The manual is

> clear that this menu item is not available until you do the Initial

> Alignment. What is not clear is whether you should do this

> immediately after Initial Alignment, or after doing several

> Additional Alignments. The manual states that the first two

> Additional Alignments are used as an estimate of the polar axis

> alignment. My question is, do I want Gemini to calculate this

model > as a necessary precursor to Polar Align Assist, or does Polar Align

> Assist ignore the model and point to where the star (e.g. Polaris)

> should be for the date, time, location, etc?



I haven't actually gone through this with the G11/Gemini, so

you can take my response with a grain of salt. I have tried

iterative methods with other mounts, however.



I believe the Gemini alignment is done because the assistance

that Gemini provides involves pointing. So you need some

accuracy in the pointing for this to be useful. I would guess

you would want to do at least 3 alignments. Unfortunately,

once you finish the iterations, you may have to redo the

Gemini alignments due to the change in position of the mount.



However, if you first use the polar scope, you can then finish

up with a drift alignment and do the Gemini alignments last.

I'm really not sure how the Gemini would speed things up, though

some people so prefer iterative methods over drift.

> Another confusing statement in the manual is: "You can also use the

> HC for additional corrections." If I'm doing a Polar Alignment why

> would I want to make corrections with the hand controller? If I'm

> being a dunderhead here, just say so ;-)



I'm not sure what they mean, but when you use an interative

method, you use mount alt-az adjustments on one star (e.g.

polaris), and hand controller adjustments on the other, leading

to a convergence to correct alignment.

> My next question relates to the accuracy of this method. How

> accurate can I get with this? Will I still need to do drift

> alignment if I'm doing imaging? How many iterations are required?

> Does it converge, and how fast?



I can only say that iterative methods never converge for me

(and all that slewing is annoying and may put wear on the mount),

but drift is easy, straightforward, and gives you time to set

up your other stuff, get your dark vision, etc while waiting.



Alan



----------------------------

#10843 Jul 7, 2002

Ok, so now I'm hearing some kinda conflicting views. Which is

the "best" (if there is such a thing) method of using the Polar Align

Assist?





1. Center "southern" star with Azimuth control, center "east/west"

star with Altitude. DO NOT move the mount with the hand controller.



1a. Move "southern" star with Azimuth control, "east/west" star with

Altitude, only go half-way to center. DO NOT move the mount with

hand controller.



1b. Move "southern" star with Azimuth control, "east/west" star with

Altitude, only go half-way to center. Center stars with hand

controller.



2. Center one star using alt/az controls, the other star with hand

controller



3. Center both stars in alt/az - don't think this works...



There appear to be several variations/combinations - which one

actually works?



Also, once the polar align assist is done, should you do a fresh

Initial Align? or does the PAA (polar align assist) properly update

all the internal variables of the model?





-=b=-



--- In Gemini_Users@y..., "saunders_ron" ron@p...> wrote:

> Not true in my case. When the mount stops at a star, the 4 move

> buttons work just fine. After you center the star using them, you

> press the menu button to go back to the other star. Now the 4 move

> buttons are live, but don't use them. Center using the Alt/Az

knobs.

> Press menu, etc. To get out hit one of the move buttons while it

is

> slewing. If you try to use one of the move buttons before it has

> finished centering, it will exit the align assist mode.

>

> BTW, I've found that it works best not to completely center the

> star. Each time it stops, correct the position of the star to

about

> half way to the center. If you fully correct, you can get into a

> loop that doesn't converge.

>



----------------------------

#27594 Oct 27, 2005

Sorry about cross post from Gemini group, but I did not get a

response there.



I used PAA for the first time last night. I have used PAC with my G-

11 Gemini succesfully before when I new I was close to alignment, but

now I have a new scope and cant use a polar scope to get close, so I

have used compass etc.. to get close and now want to use PAA to get

closer before using PAC.



I notice that the list of stars you can choose is very limited which

means the chances of one of those stars being near east or west

horizon and dec 0 are almost nill.



How close do the stars have to be to dec 0 and east or west and also

near merdian for this to work ?



I also got a little confused with the process. You suppose to do an

initial goto bright star and then sync and then choose PAA select 2

stars and then adjust using alt and az knobs of the scope.



The instructions are to centre the star. So if slewing to object on

east or west then you use AZ control knob to centre the star. What is

meant by centering the star ? I am using a ccd camera with xhairs

displayed in CCD soft. If using only azimuth know I can centre the

star vertically (y axis) in the ccd chip, but its not at the centre

of the chip. After centering with AZ knob you then are supposed to

centre the object using hand paddle. I assume this now means just

centering in one axis (X axis), because you all ready centred it in Y

axis using AZ knob.



I did this iterative process several times using 2 stars and

eventually the star would end up centred vertically (y axis) every

time on both slews, but it would never by be centred in both X and Y

is this normal ? Maybe I am not sure what is meant by centre the

object.



Best Regards

Chris







----------------------------

#27597 Oct 27, 2005

Hi Chris,



You can only center the star using both adjusting possibilities and

those are the elevation knob as well as the azimuth knob.



No other way to do that. I hope this answers your question



When you use PAC you also use both adjusting possibilities.



IMO the function PAA is just a subproduct from PAC.



I see more sense in using PAC rather then PAA.



By the way I have never used PAA so far :-)



regards Rainer



--- In Losmandy_users@yahoogroups.com, "Chris" vman_69au@y...> wrote:

>

> Sorry about cross post from Gemini group, but I did not get a

> response there.

>

> I used PAA for the first time last night. I have used PAC with my G-

> 11 Gemini succesfully before when I new I was close to alignment,

but

> now I have a new scope and cant use a polar scope to get close, so

I

> have used compass etc.. to get close and now want to use PAA to get

> closer before using PAC.

>

> I notice that the list of stars you can choose is very limited which

> means the chances of one of those stars being near east or west

> horizon and dec 0 are almost nill.

>

> How close do the stars have to be to dec 0 and east or west and also

> near merdian for this to work ?

>

> I also got a little confused with the process. You suppose to do an

> initial goto bright star and then sync and then choose PAA select 2

> stars and then adjust using alt and az knobs of the scope.

>

> The instructions are to centre the star. So if slewing to object on

> east or west then you use AZ control knob to centre the star. What

is

> meant by centering the star ? I am using a ccd camera with xhairs

> displayed in CCD soft. If using only azimuth know I can centre the

> star vertically (y axis) in the ccd chip, but its not at the centre

> of the chip. After centering with AZ knob you then are supposed to

> centre the object using hand paddle. I assume this now means just

> centering in one axis (X axis), because you all ready centred it in

Y

> axis using AZ knob.

>

> I did this iterative process several times using 2 stars and

> eventually the star would end up centred vertically (y axis) every

> time on both slews, but it would never by be centred in both X and Y

> is this normal ? Maybe I am not sure what is meant by centre the

> object.

>

> Best Regards

> Chris

>



----------------------------

#27598 Oct 27, 2005

now I have a new scope and cant use a polar scope to get close, so I

> have used compass etc.. to get close and now want to use PAA to get

> closer before using PAC.

>





How comes that you can not use your poalr scope anymore with the new

scope ?



I do not understand that ? What is now in your setup that the

polarscope can not be used anymore ?



regards Rainer



----------------------------

#27599 Oct 27, 2005

--- Rainer rsbfoto@...> wrote: > I see more sense in using PAC rather then PAA.

>

> By the way I have never used PAA so far :-)



Me neither. I'd be interested in hearing if PAA is a useful supplement

to PAC.



Alan



SCT Astrophotography: www.pbase.com/avoetsch/astrophotography

FS-102 G-11/Gemini: www.pbase.com/avoetsch12952/tak_fs102

& www.pbase.com/avoetsch12952/fs102

& www.pbase.com/avoetsch12952/takpf









---------------

Yahoo! Mail - PC Magazine Editors' Choice 2005

mail.yahoo.com



----------------------------

#27600 Oct 27, 2005

My new pier I have had made is about 4" lower than G-11 tripod. My

polar scope used to JUST be able to se eover the edge of the

observatory. Now that its 4" lower i just see the wall :-(



Hence then need for PAA before doing PAC.



Regards

Chris --- In Losmandy_users@yahoogroups.com, "Rainer" rsbfoto@r...> wrote:

>

>

> > now I have a new scope and cant use a polar scope to get close, so

I

> > have used compass etc.. to get close and now want to use PAA to get

> > closer before using PAC.

> >

>

>

> How comes that you can not use your poalr scope anymore with the new

> scope ?

>

> I do not understand that ? What is now in your setup that the

> polarscope can not be used anymore ?

>

> regards Rainer

>



----------------------------

#36599 Mar 2, 2008

I've read the manual, but would like to check my interpretation of

it.



I'm aligning a G-11. Last night, I did a Polar Axis Correction using

Sirius, shut down the mount, and did a cold start, and then built a

new model with about ten stars, using both sides of the mount. Then

I did a series of "goto's" and found my objects quite easily,

centered at about 70 power......



My question is about the mount parameter report that I got after

each "additional align." After each align I got the report:

Something to the effect of " 3' -60'" The numbers were ever so

slightly different from one star to the next, but that was about it.



I am interpreting this to mean that my polar axis on the mount is

about 3 minutes east of where it should be, and about one degree

(sixty minutes) below (Closer to the horizon) where it should be. )



Several questions:



Is this a correct interpretation?



What should I do to correct? (Just turn the elevation knob to

correct one degree higher.)



Any ideas why the Polar Axis Correction did not get the right

results in altitude?



Alex







----------------------------

#36600 Mar 2, 2008

You might get a better response by postin this on the Gemini site.



Larry



--- In Losmandy_users@yahoogroups.com, "alexmcconahay"

alexmcconahay@...> wrote: >

> I've read the manual, but would like to check my interpretation of

> it.

>

> I'm aligning a G-11. Last night, I did a Polar Axis Correction

using > Sirius, shut down the mount, and did a cold start, and then built a

> new model with about ten stars, using both sides of the mount. Then

> I did a series of "goto's" and found my objects quite easily,

> centered at about 70 power......

>

> My question is about the mount parameter report that I got after

> each "additional align." After each align I got the report:

> Something to the effect of " 3' -60'" The numbers were ever so

> slightly different from one star to the next, but that was about it.

>

> I am interpreting this to mean that my polar axis on the mount is

> about 3 minutes east of where it should be, and about one degree

> (sixty minutes) below (Closer to the horizon) where it should be. )

>

> Several questions:

>

> Is this a correct interpretation?

>

> What should I do to correct? (Just turn the elevation knob to

> correct one degree higher.)

>

> Any ideas why the Polar Axis Correction did not get the right

> results in altitude?

>

> Alex

>



----------------------------

#36601 Mar 2, 2008

Hi Alex,



I guess you mean A: 3 and E: -60



Then you are in Azimuth too far East and you have to move the front

of the scope to the West and with E:-60 you are too high so you have

to lower the front of the scope.



Look at my message dated Sunday April 16th 2006 # 12148



saludos Rainer

>

> I've read the manual, but would like to check my interpretation of

> it.

>

> I'm aligning a G-11. Last night, I did a Polar Axis Correction

using > Sirius, shut down the mount, and did a cold start, and then built a

> new model with about ten stars, using both sides of the mount. Then

> I did a series of "goto's" and found my objects quite easily,

> centered at about 70 power......

>

> My question is about the mount parameter report that I got after

> each "additional align." After each align I got the report:

> Something to the effect of " 3' -60'" The numbers were ever so

> slightly different from one star to the next, but that was about it.

>

> I am interpreting this to mean that my polar axis on the mount is

> about 3 minutes east of where it should be, and about one degree

> (sixty minutes) below (Closer to the horizon) where it should be. )

>

> Several questions:

>

> Is this a correct interpretation?

>

> What should I do to correct? (Just turn the elevation knob to

> correct one degree higher.)

>

> Any ideas why the Polar Axis Correction did not get the right

> results in altitude?

>

> Alex

>



----------------------------

#36602 Mar 2, 2008

Hi Alex,



Sorry. The message I am referring to, is in the Gemini users group.



saludos Rainer



>

> Hi Alex,

>

> I guess you mean A: 3 and E: -60

>

> Then you are in Azimuth too far East and you have to move the front

> of the scope to the West and with E:-60 you are too high so you

have > to lower the front of the scope.

>

> Look at my message dated Sunday April 16th 2006 # 12148

>

> saludos Rainer

>

> >

> > I've read the manual, but would like to check my interpretation

of > > it.

> >

> > I'm aligning a G-11. Last night, I did a Polar Axis Correction

> using

> > Sirius, shut down the mount, and did a cold start, and then built

a > > new model with about ten stars, using both sides of the mount.

Then > > I did a series of "goto's" and found my objects quite easily,

> > centered at about 70 power......

> >

> > My question is about the mount parameter report that I got after

> > each "additional align." After each align I got the report:

> > Something to the effect of " 3' -60'" The numbers were ever so

> > slightly different from one star to the next, but that was about

it. > >

> > I am interpreting this to mean that my polar axis on the mount is

> > about 3 minutes east of where it should be, and about one degree

> > (sixty minutes) below (Closer to the horizon) where it should

be. ) > >

> > Several questions:

> >

> > Is this a correct interpretation?

> >

> > What should I do to correct? (Just turn the elevation knob to

> > correct one degree higher.)

> >

> > Any ideas why the Polar Axis Correction did not get the right

> > results in altitude?

> >

> > Alex

> >

>



----------------------------

#45083 Feb 18 3:12 PM

I would like to accurately polar align my G11 for astrophotography. Are the Polar Align Assist and Polar Axis Correction routines in Gemini accurate enough for astrophotography, or should I skip those and go straight to a drift

alignment?

joel







----------------------------

#45084 Feb 18 3:13 PM

Do the Drift align first, then refine pointing model. TY dave H.



jkeshort wrote: >

> I would like to accurately polar align my G11 for astrophotography.

> Are the Polar Align Assist and Polar Axis Correction routines in

> Gemini accurate enough for astrophotography, or should I skip those

> and go straight to a drift

> alignment?

> joel

>

>



----------------------------

#45086 Feb 18 6:41 PM

I do the opposite. I build a model, polar correct and sheck guiding,

Often, I can guide at sub-pixel quickly. If not, I do 2ndcorrection then drift

align.



Bob





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



----------------------------

#45087 Feb 19 10:18 AM

Joel,



I add another step the polar align assist and then I do a Polar axis correction and rebuild the model.





greetings.

--- In Losmandy_users@yahoogroups.com, "jkeshort" joelandkarenshort@...> wrote:

>

> I would like to accurately polar align my G11 for astrophotography. Are the Polar Align Assist and Polar Axis Correction routines in Gemini accurate enough for astrophotography, or should I skip those and go straight to a drift

> alignment?

> joel

>



----------------------------

#45088 Feb 21 10:53 AM

A couple iterations of PAC can get you within a couple arc minutes of the celestial pole.



If you believe your initial alignment error to be more than a degree or so, Polar Align Assist (or any other two star iterative method) is a quick method to reduce large errors. If you can see Polaris, simply sighting up the RA axis can get you close, too. Then run an iteration of PAC or two and you are good to go for AP.



I personally use PoleAlignMax to measure the error and my own home brewed PAC-like procedure to correct the error. Takes less than 10 minutes. You can read about it here:



www.celestialwonders.com/articles/polaralignment



Frank Barrett

celestialwonders.com

--- In Losmandy_users@yahoogroups.com, "jkeshort" joelandkarenshort@...> wrote:

>

> I would like to accurately polar align my G11 for astrophotography. Are the Polar Align Assist and Polar Axis Correction routines in Gemini accurate enough for astrophotography, or should I skip those and go straight to a drift

> alignment?

> joel

>



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