Undersampling - Oversampling

Mark,

At the risk of stating the obvious, the ultimate judge is your experience under the night sky. To this end, do some testing with the scope pointed at zenith (ex. Cygnus) and go from there.

Personally I have been delighted with the results produced by my Mewlon 210 at 0.58"/pixel and I have no doubts I will be equally pleased when pursuing an even more aggressive image scale at 3710 mm focal length.

One comment which may have been overlooked when advising Brendan is the issue of guiding. As we increase our focal length, the choice of available guide stars diminishes "exponentially" and which may impact his proposed work. There are times with my Mewlon 210 (2415 mm focal length) I do not have a single guide star and irrespective of magnitude. Other times I have guided on mag 14 stars and at 280 ADU.

Anthony.

ayiomamitis wrote:

Other times I have guided on mag 14 stars and at 280 ADU.

:bigshock:

You're mad! Or a genius

I agree with you Anthony that local empirical data is de facto absolute. Under your sky conitions, with your optics, imager and mount, if it works, then that;s what works for you. And boy, are you lucky! Well, you and I know that it takes a long time and a lot of learning to get lucky Clearly your images are what they are - outstanding. So 0.58"/pixel and falling - it certainly works for you! Good points on focal length. One to be wary of. But matching your imager/OTA consists of both pixel size and field of view - and its usually a trade-off or compromise...

Mark - I think Stan's paper talks about the diagonal. I've not read it in detail myself yet but I'm sure it mentions it somewhere.

Dave