[gregbradley]

This is really a test image. I was testing the theory that lenses with a larger aperture make for deeper more noise free images.

So I took 17 x 6 seconds ISO5000 photos at F1.8 with a Zeiss 55mm lens.

Processed them in Lightroom to taste then aligned and stacked them in Pixinsight then final colour in Photoshop cc.

No noise reduction has been done.

So 55m at f1.8 = 55 divided by 1.8= 30.56mm.
Compare that to the Irix 15mm F2.4 image at ISO6400 x 10 second exposures (less overall exposure as only 5 images but its a lot noisier).
15 divided by 2.4 gives 6.25mm. So the 55mm lens is nearly 5X more light and it shows.

Whether or not you are patient enough to take a 26 image panorama with a 55m lens is another story.

So the bottom line seems to be if you use an ultra wide angle lens you are not getting in a lot of light and need to expose longer or take more subexposures and stack to compensate. Or use a longer faster lens (the longer the lens the less the coma is an issue it seems) and take a lot more panels to compose a panorama but they will be very deep. Or use a tracker and use longer exposures on the UWA lenses.

Greg.