Polar alignment when Autoguiding

[Robert_Tee (Robert)]

Hi All,

My first post.

If i want to photograph the night sky and i have an EQ6 and and Autoguider setup how important is Polar alignment?

Is close enough good enough if the Autoguider is working?

Cheers

Robert

[adman (Adam)]

Generally, the better your alignment the better your final images. If you are too far out the autoguider may not be able to keep up, and if the DEC axis is always correcting in one direction (as it will when your polar alignment is out), the your images will slowly but surely rotate through the night, so that they can be difficult to align nicely (or even at all) with each other when you stack them.

The good news is that if you have an autoguider, then you can use it to speed up your polar alignment. Have a search on IIS for polar alignment with PHD or something like that. There are a few good resources on the internet if you hunt around also.

Cheers
Adam

[Robert_Tee (Robert)]

Hi Adam,

Many thanks buddy!!

I have PHD and will have a look now here in IIS

Again Thanks

Robert

[adman (Adam)]

try this thread that contains this link

Adam

[adman (Adam)]

heres another one on basic initial alignment of your mount

[Robert_Tee (Robert)]

ARRR!!

I spent 3 hours last night tring to polar align. I must be stupid coz i just cant get my head around the concept!!!

I envy all who can do it!!!

[vanwonky (Dave)]

Originally Posted by Robert_Tee

ARRR!!

I spent 3 hours last night tring to polar align. I must be stupid coz i just cant get my head around the concept!!!

I envy all who can do it!!!

Robert, I don't think there is a better way to feel dumb than taking on polar alignment! You are in good company. Despite all the posts, websites and methods out there out there I still find it frustrating and confusing.
Cheers
Dave

[adman (Adam)]

The first few times you do it it tends not to make much sense, but after a while it just becomes 2nd nature - honest!

Which part are you specifically having trouble with?

Adam

[Robert_Tee (Robert)]

HAHAH

All of it. I have a Newt and i cant work out which is up down when its reversed. I think i got pretty close last night but not as close as i wanted. and i wanted to photograph M42 but by the time i thought i would get at least 1min exposures it went behind the trees. it was 12:30 by this stage and i could hear the pillow calling otherwise i would not have been able to get to work and spend all day posting and searching the net for issues i am having with autoguiding also.

The problem i had was which direction to adjust the scope when the star drifts up/down and left and right.

but like you said practice makes perfect my problem is i understand things better when things are shown to me. I will see it done and it will stay in my mind, when im read how to do things my simple brain does not conpute!!

Robert

[adman (Adam)]

so you are wondering which way is north, south etc when you are looking through the eyepiece? The best way is to gently push the skywards end of your scope either towards the north while you are looking through the eyepiece. If pushing it northwards corrects the DEC drift, then then star is drifting north, and if it makes it worse then the star is drifting south.

When you are pushing the scope north - you only need a very slight movement - usually not even enough to turn the axis, just to kind of stretch the scope on its mount in that direction slightly.

Are you using an illuminated crosshairs type eyepiece or are you just eyeballing the drift?

Adam

[OzRob (Rob)]

I gave up on manual alignment pretty quickly. I now use Pempro to do alignments. The package is a bit pricey but does some other things too. There is a good program available for less than $20 that achieves fairly accurate alignments quickly called Alignmaster. You can try it for 30 days for free.

[Robert_Tee (Robert)]

Hey Adam,

Im using an illuminated eye piece. So when you say push it north you are saying If im standing next to the South facing leg of the mount facing North i push in that direction? or are you saying while looking through the scope facing west pusing the scope from the botom up?

This is what confuses me i think. Sorry for the dumb question.

Robert

Robert

[Poita (Peter)]

Give PHD a go, you will never look back.
Or try align master.

PEMPRO has a free trial, it is worth a go too, try its polar alignment wizard.

http://www.ccdware.com/products/pempro/features.cfm

[swannies1983 (Dan)]

Robert,

I hear your frustration. I remember when I first learnt to polar align. Many hours of cursing.

There are several ways to polar align. I used to use PhD as it gives you a pretty quick guide as to whether you're aligned or not. Recently, I have moved over to using a free program called EQAlign. Basically the program identifies a "safe zone" on the meridian and east/west. You then pick a known star within this safe zone and let the mount track for 10mins. The program will calculate drift and then will tell you how far you need to move the mount in azimuth (meridian alignment) or altitude (east or west alignment). I find it to be pretty accurate after one iteration but I like to do it twice. I generally now only worry about the azimuth adjustment and skip altitude.

[adman (Adam)]

Originally Posted by Robert_Tee

Hey Adam,

Im using an illuminated eye piece. So when you say push it north you are saying If im standing next to the South facing leg of the mount facing North i push in that direction? or are you saying while looking through the scope facing west pusing the scope from the botom up?

This is what confuses me i think. Sorry for the dumb question.

Robert

Robert

OK. When you are drift aligning you are looking at stars in one of a few positions. Either the eastern or western horizon - or close to it, and on the meridian nearish to the celestial equator.

If you are looking at a star in the east (to adjust your altitude/latitude), the DEC axis will be rotated 90 degrees from its home position counterclockwise as you are looking down on it from above, and the RA axis will be up say 20-30 degrees. Now stand at the rear of the scope - so you be facing east - to push the scope north you will either push the end of the scope nearest to you to your right (which is south), or the end furthest from you to the left (towards north). Or to put it another way, you want to push the scope so that it rotates the DEC axis counterclockwise when viewed from above.

The, if you are looking at a star on the meridian near the equator, the DEC axis doesn't change position much, but now the counterweight shaft should be horizontal, or close to it. Then, still standing in the same position you were (still facing east with the scope in front of you), again to move the scope north you will need to push the top end of the scope left, or the bottom right - so counterclockwise as you are looking at it.

I could never figure out looking through the EP of my new which way was which either...

When you get going with PHD for polar alignment, you will be able to point to a star in the east and say "if the DEC trace in PHD is moving up the screen, that means I need to turn the altitude adjuster this way, and if the trace is moving down then I need to turn it the other way" and same for the star near zenith - except you will be adjusting the azimuth. Thenyou will be able to forget all the directions and what they mean.

Adam

[swannies1983 (Dan)]

Originally Posted by adman

When you get going with PHD for polar alignment, you will be able to point to a star in the east and say "if the DEC trace in PHD is moving up the screen, that means I need to turn the altitude adjuster this way, and if the trace is moving down then I need to turn it the other way" and same for the star near zenith - except you will be adjusting the azimuth. Thenyou will be able to forget all the directions and what they mean.

Adam

Good advice. I wrote these as notes in my mobile so I had my reference handy when polar aligning using PHD.

[Robert_Tee (Robert)]

Ok Cool, i will give it a crack tonight.

Thanks so much Adam and all who had advice.
I will keep you posted

Robert

[adman (Adam)]

I found that when aligning manually, the best thing to get in your head was what you were actually trying to achieve. The goal of polar alignment is to get the mount/scope to describe the same arc as the stars do when they move.

Then you can see easily that the movement in DEC is due to your mounts arc not lining up with the star's arc, and you can also see which way you need to adjust azimuth/altitude.

One of the best visual aids in this regard was this youtube video (the sound is terrible, but the visuals are worth 1000 words). Just be aware that this is for the northern hemisphere, so you will need to swap directions N <--> S

Adam

[Robert_Tee (Robert)]

Ok i will have to concentrate on getting my SPC900NC working with PHD first then i can give it all a go.

Too much too learn!! LOL

Thanks Again mate

Robert