3 replies to this topic

[psugrue]

OK so "everything" is working. I am doing a 2 star alignment and adding 4 calibration stars and then a ASPA then I am doing a precise goto then guiding via PHD2 and the images are stacking and I can stretch in GIMP and while I am not going to win any awards on AstoBin, I am pretty sure that my Sister and Mum don't actually believe that I took the pics that I email them from time to time due to their uncharacteristic "radio silence". So for me, that's about as good as it gets. Therefore this question is somewhat academic. Is ASPA chicken and egg? In other words, does a perfect (or as perfect as you can get) ASPA need a perfect 2 star + 4 calibration align? And does the 2 star + 4 star need a perfect ASPA. So if you had enough time and patience and the goal was to get the best ASPA and 2+4 align. Would you want to do multiple iterations? 2+4 then ASPA then 2+4 then ASPA etc ?

 

Regards,

 

Patrick

[Scdouglas]

It's not exactly a chicken and egg situation though you are right somewhat. ASPA can definitely improve iteratively to some degree but I've never heard of anyone recommending more than 2 or 3 iterations of it. Beyond that you get into diminishing returns. I have an AVX though and at this point a PHD2 drift align is faster for me than doing ASPA, though when I first started using the drift align method it took a lot longer. Do whatever works best for you, I find ASPA to be a bit too finicky for my liking but I know people swear by it, but I would say 2 iterations will get you almost all the way there and 3 if you're motivated. 

[SkipW]

 In other words, does a perfect (or as perfect as you can get) ASPA need a perfect 2 star + 4 calibration align? 

Yes.

 

 

And does the 2 star + 4 star need a perfect ASPA.

No.

[dmdouglass]

They are different "Tools", and each has a different "objective".

 

The 2 star + (x) calibration addresses two questions...

First, do I know where i am in the sky ?

Second, can i calculate the "cone" error ?

These two are most important for POINTING.

 

The ASPA is for Polar Alignment. 

 

Put the two together, and you have good POINTING and good TRACKING.

 

So....  the two compliment each other.

 

[EDIT ADD]

If you read the full instructions for ASPA... and "think on it for awhile...."

 

Do a 2+4 alignment...

Then do the ASPA

Then do a NEW 2+4 alignment

 

and repeat the cycle until you are happy with results (usually 2-3 times).

Edited by dmdouglass, 22 January 2021 - 03:28 PM.