Confused about polar alignment!

[Starlord87]

Hi all i may make myself sound reaaly daft here but i have a question thats confusing the hell outa me! Basically i want to know why you need to polar align when you are just going to be moving the scope around the sky anyway looking for planets and stars etc etc. It just seems a bit pointless to me polar aligning a scope/mount which is going to end up pointing in a different direction:/ sorry if its a daft question i just cant get my head around it! Thanks all

[Tinker1947]

You don't need to Polar align, if its a EQ Mount point it roughly at Polaris and your set-up....

[Starlord87]

Aye but why do we need to point it at polaris when we are just going to adjust the scope so its pointing at say saturn or venus or other parts of the sky?

[Stu]

Because the idea of an EQ mount is that once it is set up correctly it only needs to move on one axis to track objects as they move across the sky (because of the earth's rotation).

Setting up the RA Axis so that it points at Polaris involves using the altitude and azimuth adjustments on the mount. Once done, you leave these fixed and move the scope in RA and declination.

You point the scope at your object, lock the clutches and can then track your object by moving the mount in RA, or by switching on the RA tracking motor if you have one. It just makes it easier to keep the object in view.

EDIT By the way, nothing daft about the question, EQ mounts are confusing [emoji3]

[graemlourens]

Hi Starlord.

You do not need to always polar align, i'll try to differenciate when you have to.

You do not need to polar align if

- you know where to find your object and do not require a computerized mount (goto system)

- you have an ALT-AZ Mount and just want to starhop and look around.

You need to polar align if

- a computerized mount will go to a location of an object. (also ALT-AZ mounts need to know where they are pointing originally)

- you have an EQ mount (vs an ALT-AZ Mount)

- you want to make longer exposure photograps (not the moon or planets for example that require very low exposure time)

Polar alignment is an initial alignment of the telescope with the earths axis (that is tilted). From that point onwards you can imagine that your scope is now perpendicular to the earths axis, and from that point onwards we have the RA & DEC 'Map' of the sky, so a computer will find objects - assuming your Polar alignment is correct - to a very high precision.

For Photography the Polar alignment is not only for 'goto accuacy' but if you don't have polar alignment, after between 15 - 30 seconds and depending on your focal length the object 'rotates' in the sky compared to your camera, and the image will not be sharp (especially in the corners).

Kind regards, Graem

[Scooot]

Aye but why do we need to point it at polaris when we are just going to adjust the scope so its pointing at say saturn or venus or other parts of the sky?

You point the mount at Polaris, and the mount stays pointing at Polaris when you move the scope.

To move the scope in right ascension you rotate it around the axis that is pointing at Polaris. You do this so your scope follows the path a star would take across the sky. If it wasn't polar aligned, when you rotated the scope it wouldn't track the star.

Sorry a bit slow typing

[ronin]

The polar alignment only really applies to a mount that has motors on it (not 100% correct but easier to consider as such).

When you ponit the scope at an object then let go of the handset/controller then the mount continues to track and on an EQ mount this is simply the RA motor continues to drive.

The movement is circular and the axis is the earths axis, so if you want the object to remain reasonably in the view you have to perform this polar alignment of the mount. Otherwise the mount can be moving one way and the object another, under that state the object disappears out of view very fast.

It is the presence of the motors and the requirement to keep the object in view for more then a few seconds that means that a half reaonable polar alignment is required.

If no motors then you have to keep moving the scope - manual dobsonian style - and on an EQ mount this is not really simple/easy.

The flexible items move the EQ in RA+Dec so they would follow the axial alignment of the mount which if not polar aligned means to track one object you have to apply both RA movement and a Dec movement.

[Stu]

The polar alignment only really applies to a mount that has motors on it (not 100% correct but easier to consider as such).

When you ponit the scope at an object then let go of the handset/controller then the mount continues to track and on an EQ mount this is simply the RA motor continues to drive.

The movement is circular and the axis is the earths axis, so if you want the object to remain reasonably in the view you have to perform this polar alignment of the mount. Otherwise the mount can be moving one way and the object another, under that state the object disappears out of view very fast.

It is the presence of the motors and the requirement to keep the object in view for more then a few seconds that means that a half reaonable polar alignment is required.

If no motors then you have to keep moving the scope - manual dobsonian style - and on an EQ mount this is not really simple/easy.

The flexible items move the EQ in RA+Dec so they would follow the axial alignment of the mount which if not polar aligned means to track one object you have to apply both RA movement and a Dec movement.

That is not correct really. Polar alignment is just as valid for a manual EQ mount as it simplifies finding things and makes tracking of the object by just turning in RA much easier.

[Starlord87]

Thanks all, those answers have cleared it up a bit for me its all starting to make sense now. Oh and i have a EQ mount with a motor drive attached

[Stu]

Hi Starlord.

You do not need to always polar align, i'll try to differenciate when you have to.

You do not need to polar align if

- you know where to find your object and do not require a computerized mount (goto system)

- you have an ALT-AZ Mount and just want to starhop and look around.

You need to polar align if

- a computerized mount will go to a location of an object. (also ALT-AZ mounts need to know where they are pointing originally)

- you have an EQ mount (vs an ALT-AZ Mount)

- you want to make longer exposure photograps (not the moon or planets for example that require very low exposure time)

Polar alignment is an initial alignment of the telescope with the earths axis (that is tilted). From that point onwards you can imagine that your scope is now perpendicular to the earths axis, and from that point onwards we have the RA & DEC 'Map' of the sky, so a computer will find objects - assuming your Polar alignment is correct - to a very high precision.

For Photography the Polar alignment is not only for 'goto accuacy' but if you don't have polar alignment, after between 15 - 30 seconds and depending on your focal length the object 'rotates' in the sky compared to your camera, and the image will not be sharp (especially in the corners).

Kind regards, Graem

Polar alignment is the process of aligning the mount, not the scope. The scope is irrelevant when aligning. Effectively it puts the RA axis parallel to the earth's axis, not the scope perpendicular to it.

[Stu]

Thanks all, those answers have cleared it up a bit for me its all starting to make sense now. Oh and i have a EQ mount with a motor drive attached

Good stuff.

That makes polar alignment useful as when you have centred the object and switch the motor drive on it will basically stay centred. It will drift slowly depending upon the accuracy of your PA and also other tolerances within the mount. I started out with a single axis driven EQ mount. Great way to learn

[graemlourens]

Polar alignment is the process of aligning the mount, not the scope. The scope is irrelevant when aligning. Effectively it puts the RA axis parallel to the earth's axis, not the scope perpendicular to it.

Darn, typo, i obviously meant aligning mount! scope does matter though because of cone error, but thats another story  (I got lot of that cone going on, every meridian flip i'm annoyed again about it!)

And perpendicular was obviously wrong word too. 'in line with' would have been correct.

sorry for confusion. Explaining this stuff is sometimes difficult

[Starlord87]

Thats alright i apreciate the help i understand much better now how it all works now if someone could just tell me how to get rid of cloudy skys??.....

[Stu]

Thats alright i apreciate the help i understand much better now how it all works now if someone could just tell me how to get rid of cloudy skys??.....

Ah, that's an easy one....... [emoji6]

http://www.firstlightoptics.com/misc/zarkov-cloud-gun.html

[MarsG76]

Think of it this way, the EQ mount has 4 "pivot" points, Altitude (Alt), Azimuth (Az), Right Ascension (RA) and Declination (Dec)... when you align the Right ascension bar using the Alt & Azimuth adjustments to be pointing at either Polaris or the location of the South Celestial pole (when in the southern hemisphere). You use Dec and RA to find your object in your eyepiece and you only turn or use the mount movement in the RA axis to keep your object tracked in the field of view.

Think of the movement on the RA axis as the actual movement of the stars in the sky as the earth rotates on its axis.

[Starlord87]

That looks an amazing piece of kit! Haha thanks

[RichM63]

Most everything has been covered, but if you are setting up and PA'ing on your own property, when you have done this mark the positions of the tripod feet on the ground, so that next time you can just more or less plonk it down for a visual observing session.

Ask all the questions you want to, it's how we all learn.

[Dentalal]

Thanks so much for all this info.

I've just got myself a EQ3 mount. Do you usually polar align before you put your telescope on the mount, or afterwards? I keep bumping my head with the scope on!

[Vox45]

Thanks so much for all this info.

I've just got myself a EQ3 mount. Do you usually polar align before you put your telescope on the mount, or afterwards? I keep bumping my head with the scope on!

then I would recommend this

It is recommended to do the PA before putting the scope on the mount as the weight makes it hard on the screws used to align the mount. For my part, I align after putting the scope on the mount because I use the drift alignment method and need the scope to do that

You don't need to Polar align, if its a EQ Mount point it roughly at Polaris and your set-up....

I agree, for visual no need to use the circles and PA application, just center polaris bang in the middle of the cross in the polar scope, that is more than enough.