Mosaics, binning or resample?

[jmtanous]

Hi,

I am planning to shoot a 4x3 mosaic this season.

It is likely that the finished mosaic will be resampled to 1/2 of the native mosaic's resolution.

I plan to shoot the Cygnus region in Ha so I will have enough time to finish shooting the 12 panels even if the weather does not cooperate.

My question is:

Is it better (more image details, etc), to:

-- shoot 4h per panel @ 1x1, assemble the mosaic and rescale the image to 1/2 of the native resolution

-- shoot 2h per panel @ 2x2, and assemble the mosaic at native resolution.

I mean if I know beforehand that I won't gain much by shooting at 1x1 I prefer shooting @ 2x2, it is faster to deal with smaller panels.

Cheers,

Jose

[Juan Conejero]

Hi Jose,

-- shoot 4h per panel @ 1x1, assemble the mosaic and rescale the image to 1/2 of the native resolution

-- shoot 2h per panel @ 2x2, and assemble the mosaic at native resolution.

With 2x2 binning you get a 4x sensitivity increase so you can go much deeper in less time. The mosaic will be much easier and faster to build because you'll have to deal with 1/4 of the data volume at 1x1. On the other hand, if you generate the mosaic at 1x1 then downsample 1:2 you'll get a more accurate result and better star shapes. Tough decision

These are the facts. It all depends on what you want to do. Let's see what others have to say.

[jmtanous]

Hi Juan,

Thanks for the answer. I am more or less aware of the 'theoretical' tradeoffs. For narrowband imaging 2x2 binning usually increase the SNR by 4 cause the major source of noise is the camera's read noise.

I am interested in the 'pragmatic' side of binning vs rescaling... Most of the time I am more comfortable processing oversampled data, not sure why...

Another factor that I didn't mention is that I am already undersampled @ 1x1 (3 arcsec/pixel)

Cheers,

Jose

[RBA]

It is likely that the finished mosaic will be resampled to 1/2 of the native mosaic's resolution.

While I'd suggest going for 1x1, I'd say go 2x2 (I know, that doesn't make any sense  8) ).

Then next time do 1x1 and compare!