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Re: Polar Align Assist(ance)


Mar 26, 2002

 


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#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



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#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



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