PixInsight Forum (historical)

PixInsight => General => Off-topic => Topic started by: Hans Pleijsier on 2010 August 18 13:00:09

Title: when the pixel aspect ratio is not equal to 1
Post by: Hans Pleijsier on 2010 August 18 13:00:09

Hello PI-friends,

My question is:

What are the (pro's and) con's of a CCD camera with non-square pixels?
Any special considerations during image processing?

Thanks in advance,

HP

Title: Re: when the pixel aspect ratio is not equal to 1
Post by: Nocturnal on 2010 August 18 13:18:28

Hi Hans,

PI generally doesn't care about the aspect ratio of your images but I can imagine there's a chance that wavelet based processing may produce a different result depending on whether the image was resized before or after.

- resample to square the image
- wavelets

vs.

- wavelets
- resample to square

You could try this yourself to see. I think the decision you need to make is whether you resample as the first or final step in PI. Generally I'd say resample as late as possible but given scale based processing with wavelets it may be better to resample first.

Judging by your name you're probably Dutch so perhaps the expression 'lead or old iron' 'lood om oud ijzer' means something to you. In other words it probably doesn't matter.

That said I had non-square pixels (DSI) and I'm glad they're square now. Star registration works much better for starters.

Title: Re: when the pixel aspect ratio is not equal to 1
Post by: Hans Pleijsier on 2010 August 19 12:07:34

Sander,
Thanks, I understand that the non-square-pixel is not a show-stopper for PI.
HP