[avandonk]

Thanks for the comments. This is the sort of quality my mosaics done with this lens has.

I routinely upsize my images by a factor of 1.6 before stacking. The image of the two Centaurus objects above is the result of stacking four sets of twenty 192MB tiff images. These four exposure stacks are then used to produce the HDR image which is then finally tone mapped to an LDR image. That is why you can see the core of OC without it being blown out as well as the very faint galaxies.

The Vela SNR mosaic is 11800 x 11200 pixel sized image and 770MB Tiff. I had to reduce it to 6000 pixels wide as some of my 32 bit programs just cannot manipulate such large files due to memory limitations.

Below is a map showing the positions of many of the faint galaxies. Some of these are quite visible in the image.

Chris I would not put up high resolution images if I was worried about what people with do with them. The images I take are for all to see and use for their own enjoyment and education. The usual acknowledgement is all that is expected if reproduced somewhere else. If for profit, I will generally give written permission if asked.


The external aperture has two effects.

1. It only allows light actually contributing to the image to enter the lens. There is then almost no scatter of light (from the interior of the lens) not contributing to the image which reduces contrast or signal to noise. The lens hood extension also really helps here. This is the same effect that baffles have in a high quality refractor.

2. No difraction effects from the lens aperture blades. The lens aperture is left wide open at f/2.8. I cannot stand unavoidable diffraction artefacts.

If weather and time permits I am going to try an external aperture and lens hood extension to a 50mm or 85mm lens. I am sure it would increase contrast and definitely get rid of those pesky difraction spikes.

I had not considered an improvement of less CA Bojan apart from eliminating the lens outer edges where most of the CA is produced. It could be that the internal lens aperture does not eliminate all off axis not image contributing light.

Bert