[Placidus (Mike and Trish)]

Hi, David,

Thanks for the interesting and thought-provoking question. Here's what I think:

Our 20 inch scope collects 6400 times the photon flux of the human eye. With a one hour exposure, it's got perhaps 54,000 times the integration time of a living-room adapted human eye, and still a thousand times that of the darkest-adapted eye. So we are increasing the total number of photons collected by 64 million times. Dr Malin might think that is artificial, and cheating.

The scope has a resolution limited only by seeing, at say 2 sec arc, whereas the living-room adapted eye has a resolution of about 60 sec arc, 30 times worse. The dark adapted eye's resolution is pathetic. Using the scope is starting to sound like a disgusting conspiracy to pervert the beauty of the eye. Perhaps David might like to throttle down the aperture of the AAT to a quarter inch, to make the images more natural looking.

If Dr Malin uses a cheap spectrometer, he can distinguish colours separated by a few nanometers, and a good spectrometer hilariously better again (down to a femtometer is commercially available) whereas colourbind Mike can barely distinguish red from green.

As to the use of unsharp masking, well that is definitely unnatural, bordering on cheating.

I think it is completely sensible to enhance the colour differences to the point where they are easily distinguishable without getting a headache. It is more than sensible, it is a moral obligation to enhance them to the point where they are telling a valid story about the astrophysics, for example showing that the core of a galaxy is generally more orange, and the OB regions in the spiral arms generally more blue, or for example that ellipticals are generally more orange than tidally disrupted spirals.

But to go beyond that, to the point where they are lurid, like a National Flag, is at best art, and not necessarily even good art.

So I would argue strongly for artificially increasing the saturation just to the point where we are saying something sensible about what is up there, but no further.

If Dr Malin's definition of "pastel" is "no greater colour distinction than that of the dark adapted (but in my case colour-blind) human eye", then he is being wildly inconsistent and unscientific, making a personal aesthetic choice that is totally unjustifiable. He should set down his thermometer, and use only the palm of his hand; he should set his spark plugs by eye; he should diagnose a heart attack on symptoms and not cheat using an electrocardiogram or cardiac enzyme analysis. He should drive using only his gut feeling of how fast he is going, and avoid the unnatural distinctions that Constable Bookem might use with his Lidar.

Of course, they are the Malin Awards, not the Mike Awards, and he is perfectly justified in making a personal aesthetic choice, but we must not fall into the trap of thinking that it is based on logic, or that it is the last word, or that they should become official IIS Deep Sky Policy.

I personally shall continue to avoid lurid like a butcher's apron, lurid like a kindergarten landscape, lurid like a national flag, and aim for saturated enough to tell the one, true story about what is up there.

Very best,
Mike Berthon-Jones