Polar alignment - nope, just do not understand it.

[BrendanC]

Hi all,

So, when I first bought my scope (Sky-Watcher Explorer 130P SynScan AZ GOTO) the nice lady in the shop told me that, to align it, I should choose two-star alignment.

Several months later I'm all fine with that. I often find that daytime alignment with Saturn or Jupiter just as it's going dark tends to be sufficient for quick viewing, but I have used two-star and it all works well.

However, polar alignment has always bothered me. I keep coming across it. It isn't available as an option in my Synscan. I've read plenty about it, but really, just do not understand why it's necessary. Sorry, I'm sure this has been asked before many, many times, but it's just not making sense to me.

So my two questions are:

1. Why is polar alignment necessary if, say, you can align yourself with two (or even three) stars? If someone could answer this in, say, fewer than 50 simple words that would be great.

2. Furthermore, even if it's necessary for a manual mount., it is necessary if you're using a mount that tracks automagically like mine?

That's all. Again, apologies if this is numbingly familiar to you all but it's something that bothers me, a bit like vague toothache that you know you should do something about sooner or later.

Thanks, Brendan.

[Adreneline]

14 minutes ago, BrendanC said:

Why is polar alignment necessary if, say, you can align yourself with two (or even three) stars? If someone could answer this in, say, fewer than 50 simple words that would be great.

I can't do it in less than 50 words but this is a useful guide to read and pages 10 (diagrams) and 11 seem to answer your question.

Adrian

[Kn4fty]

To polar align in an equatorial setting will allow your scope to track your target using only one axis, the RA. This makes for easier tracking especially for astrophotography. 

Tracking in the alt az mode means the computer must make adjustments in two axis to stay on target. You might not notice it visually, but some cameras might .

Personally, I use a manual equatorial most of the time for viewing. I just prefer it.

Rob

[Captain Scarlet]

There are 2 main types of mount, AZ and EQ. For a beginner, AZ is the most intuitive, it’s what terrestrial photographers call “pan/tilt” - you rotate side to side and up and down to point. To track things in the sky as the earth rotates, both axes need to be changing: a bit sideways and a bit up or down.

The other sort is EQ, which can be imagined as the same as AZ, except the whole thing is tilted so the side-to-side axis is tilted towards the North or South pole. This means that once you’ve pointed the scope at a celestial object, only the (tilted) side-to-side axis needs to be moving to match the earth’s rotation. The other one stays locked. There are other considerations (eg “field rotation”) but they only really affect things if you’re talking very long-exposure photos.

The process of pointing the axis towards the pole is called “polar alignment”.

Your mount is an AZ mount, which the goto controller recognizes, and which means it doesn’t offer it as an option since it’s not relevant.

OK more than 50 words but I did my best.

[Cornelius Varley]

48 minutes ago, BrendanC said:

Hi all,

So, when I first bought my scope (Sky-Watcher Explorer 130P SynScan AZ GOTO) the nice lady in the shop told me that, to align it, I should choose two-star alignment.

Several months later I'm all fine with that. I often find that daytime alignment with Saturn or Jupiter just as it's going dark tends to be sufficient for quick viewing, but I have used two-star and it all works well.

However, polar alignment has always bothered me. I keep coming across it. It isn't available as an option in my Synscan. I've read plenty about it, but really, just do not understand why it's necessary. Sorry, I'm sure this has been asked before many, many times, but it's just not making sense to me.

So my two questions are:

1. Why is polar alignment necessary if, say, you can align yourself with two (or even three) stars? If someone could answer this in, say, fewer than 50 simple words that would be great.

2. Furthermore, even if it's necessary for a manual mount., it is necessary if you're using a mount that tracks automagically like mine?

That's all. Again, apologies if this is numbingly familiar to you all but it's something that bothers me, a bit like vague toothache that you know you should do something about sooner or later.

Thanks, Brendan.

Your AZ mount doesn't require polar aligning, only equatorial mounts (manual or goto) need to be polar aligned. The purpose of polar alignment in an equatorial mount is to align the right ascension (RA) axis of the mount with the north celestial pole (northern hemisphere) or south celestial pole (southern hemisphere). 

[BrendanC]

Outstanding. Thanks all. I love it when I'm told it's something I don't need to worry about.

And I think I'd missed the bit about it being just for EQ mounts, so I think I actually understand it with respect to EQ and not AZ.

What a relief. Toothache gone.