Pickering Scale

Following some useful advice in another thread I was checking out the Pickering Scale.

This link is excellent uk.geocities.com/dpeach_78/pickering.htm but I looking for more details on the technique.

Should I select any magnitude star near the object I wish to view?

OR

Would it be better to always use the same star (e.g. Polaris) to measure seeing over several nights?

Should I use my highest power EP?

Can I expect seeing to vary a lot over a night?

As usual, any advice appreciated.

I usually pick a random mag 2-ish star at between 45° and 70° of altitude. Polaris would work, but it doesn't need to be the same star each night.

Yes, you should probably use your shortest EP, perhaps even with a Barlow. I'd recommend somewhere between 50X per inch and 80X per inch for a refractor. An obstructed scope (Newt or Cat) will throw more light into the first diffraction ring, and so can probably get by with 40X to 60X per inch.

The original Pickering scale was developed with a 5" refractor, so as close to that as you can get helps (I use a 4", which seems to be close enough).

On most nights the seeing stays within the same Pickering number or perhaps varies between two adjacent numbers. But I've seen it move as much as 3 steps on the scale when a front is moving in.

Cheers,
-- Jeff.