How Good Does My Polar Alignment Need To Be?

[mbalkham]

So I'm now in NZ and the scope has finally arrived (in the same number of pieces as it left the UK in September!). Managed to get out last night for a quick go. Quickly realised I should face South now, but wait no Polaris!

So I had done a little prep and knew it would be different here. Not really sure where to start I roughly pointed the tripod to the south, pointed it up at about the right angle and headed to Alignmaster.  Did a couple of 2 star alignments pretty easily (guess it must have been nearly south and nearly right angle) and managed to point the scope at a bight ish part of the sky (in this case trusty old M42). Rattled off a few quick shots without tracking and they came out pretty well (new coma corrector and focuser making life much better already!).

So here's the question, how good does the alignment need to be once I turn on the PH2 tracking (few technical issues with that last night then the clouds came rolling in before the pad could find the guidescope)? Navigation is a little tricky if I'm off with the alignment/home position but I just go to a bright ish star nearby (to my target), moving the scope with the pad to centre the star in the finder scope and then main scope (and focussing here normally using the mask) and then re-centre Cartes du Ciel to match the scope. Then when I ask C2C to slew to the deep space object I want to image it is usually pretty close to centre at this point and I can re-compose/re-frame the image before I start tracking and shooting.

Will PH2 be able to make enough adjustments if I'm not all that well aligned? Or do I need to spend more time/effort getting a better alignment (I'm on a tripod so am doing this everytime I go out not once and leaving the scope set-up in an observatory). And if so how do I achieve this in the Southern Hemisphere?!

Thanks in advance

[Merlin66]

sounds like you're close enough to get results....

The (lack off) PA accuracy when it comes to guiding, only affects field rotation.

PHD will keep the target star "locked on" but the outer edges of the FOV will show the effects of misalignment.

It's up to you to judge what is acceptable.

[kens]

It's worth stating also that alignment for the purpose of navigation ("star alignment")  is quite different to polar alignment for accurate tracking. You can have a perfect polar alignment but still not navigate accurately to objects due to non-level tripod, cone error etc... 

Alignmaster can get you a good polar alignment as youve found and/or you can drift align in PHD. The trick is to get the tripod and mount set up as closely as possible each time to minimise the adjustments you need to make.