How to polar align your mount using the polar scope - a video tutorial [Deep Sky] Acquisition techniques · Piotr K. · ... · 8 · 225 · 2

Hi guys, recently I made a tutorial on how to correctly polar align your mount using the polar scope. Reading across the internet I found out that there seems to be a lot of confusion about this method, despite it's really easy and fast to do. Here's the video:

Polar alignment using the polar scope - in 7 easy steps

I hope it will be helpful, and if you have any questions - feel free to ask!

Brian Puhl:
There is really no need to level an EQ mount.

You do if you are rotating your polar scope so that 0 is straight up.  Otherwise your "clock" position of polaris would be off.

I would say that levelling your mount will make it easier to perform the polar alignment, but it isn’t necessary. The desired end result is that your mount is aligned to the north or south pole, and that can be achieved with a mount that is not leveled accurately.

How do you level your mount? By eyeballing how level it is, or by accurately measuring it? If there’s no real difference in both approaches, then how necessary is levelling? 

Another question I have: by using this technique, how good is your polar alignment if you measure it? Does it work for long focal lengths?

Rick Krejci:
You do if you are rotating your polar scope so that 0 is straight up.  Otherwise your "clock" position of polaris would be off.

In fact, it doesn't matter which number is up. It can be any, 0, 3, 6 or 9. The important thing are the lines of the cross - they need to be aligned with physical vertical and horizontal directions, because only then positioning Polaris on the appropriate spot on the circle will point the RA axis towards the celestial pole.

Kristof Vandebeek:
I would say that levelling your mount will make it easier to perform the polar alignment, but it isn’t necessary.

Depends on how you polar align. If one uses the polar scope, then leveling will ensure that the vertical and horizontal lines on the cross are aligned with physical vertical and horizontal directions. If one uses other methods, like the procedures in ASIair or NINA (I think there is a PA procedure in NINA, right?), then levelling is not necessary, because one doesn't need physical vertical and horizontal directions as a reference.

Kristof Vandebeek:
How do you level your mount?

I use bubble levels built in the heads of my EQ3-2, EQ5 and CEM25p mounts.

Kristof Vandebeek:
Another question I have: by using this technique, how good is your polar alignment if you measure it?

I never measured it, because I don't see any need to do it

Kristof Vandebeek:
Does it work for long focal lengths?

What does the focal length to do with it..?

In fact, the only (important) issue caused by not very accurate PA is a slight drift in Dec axis, easily corrected by guiding. The periodic error (PE) in RA axis, at least in my mounts, is orders of magnitude bigger than this drift, so without guiding it wouldn't matter if I polar align precisely or not, because my subs would be ruined by PE, anyway   But I use guiding, and I routinely achieve 480 s subs on my EQ3-2 and CEM25p mounts, with imaging scales being 1,85"/px and  2,46"/px, respectively. Here's a log from one of my sessions on EQ3-2:

Rick Krejci:
For a polar scope, it's more important since you are placing Polaris on the "clock" and particular East/West leveling is necessary.

EXACTLY!! In fact, only leveling in East/West matters, and levelling in North/South is not necessary, because (from the mount's point of view ;) ) it's equal to being located on higher / lower latitude. I'm really happy to see that there are still people around who understand this!! (maybe there is a lot of them, actually? But here in Poland the understanding of PA seems to be extremely low, especially since all these software-aided procedures entered the market... ).

BTW, what is "RAPAS"...?

Piotr K.:
EXACTLY!! In fact, only leveling in East/West matters, and levelling in North/South is not necessary, because (from the mount's point of view ;) ) it's equal to being located on higher / lower latitude. I'm really happy to see that there are still people around who understand this!! (maybe there is a lot of them, actually? But here in Poland the understanding of PA seems to be extremely low, especially since all these software-aided procedures entered the market... ).

BTW, what is "RAPAS"...?

RAPAS - Right Angle Polar Align Scope.   It's Astrophysic's excellent Polar align scope that you don't have to get on the ground to use since it has a right angle lit viewfinder.    Has a nice app to tell you exactly where to put Polaris.   As I said, can usually get within about 1 arcminute confirmed by Nina's 3PPA.