I purchased yet another T2 extension tube at AstroFest, this time a 7mm one. Finally, I can get to focus on the Sigma 10-20mm zoom with the QHY9 camera. It may indicate 0.6m on the lens scale but I’m not worried about that.
I set it on 20mm for some wide field pictures of Orion with 300 second exposures at f/3.5. The cropped result is shown here after some use of GradientXterminator to remove some of the light pollution in the frame.
There’s some pretty bad spherical aberration with this lens but that can be expected with such a short focal length.
2 replies on “Orion widefield”
Weird colours. But it’s revealed a lot. And the spherical abberation looks to be only in one direction. Was this an enlargement of one edge of the field? Otherwise it looks like your lens is on the huh (although I’m sure it’s not).
Dan
The colours are largely due to some background flattening and equalisation to remove the light pollution gradient. This is an enlargement of a field corner. I did expect Barnard’s loop to be more pronounced than it appears in this image but it is a very faint structure and Orion wasn’t very high in the sky.