I've decided to expand my photographer's art into astronomical photography. I have yet to purchase a tracking equatorial mount so my options are limited to begin with.

I do have a Sigma 150-600mm Sport lens which is competent for wildlife photography but in order to photograph deep sky objects I will need at least 1200mm so I purchased the Sigma 2X 2001 teleconverter. I now have in practical terms a 300-1200mm lens but optical performance is an issue.

A focal length of 1200mm is almost useless for bird photography except for distant slow feeding waders and other larger birds and I will use it for that purpose from time to time but how does it perform?

I took it out for a test run and took some quick photos using bean bags on the roof of the car or the window sill for stability. Foolishly I didn't turn off the image stabilizer so the auto focus wandered a bit which may have had a negative effect on image definition.

I had to shoot at high ISO (1600-6400) in order to get acceptable sharpness in my subjects. This will also be the case for astronomical photography and for wildlife photography so a high quality camera is necessary. I've got that issue covered with the superb Nikon Z7.

Now here's the thing which surprised me and which I needed to confirm with the test shots. The Sigma 150-600mm Sport lens at 1200mm is just as good as the best Nikon 600mm F4 or Canon 600m F4 at 1200mm. You doubt this? Well check Digital Lens Comparisons and compare the three lens setups at 1200mm shooting at two stops above wide open usually the sweet spot for most lenses. The Nikon and Canon setups would have a two stop advantage over the Sigma but this is less of an issue with modern camera bodies that can shoot competently at high ISO.

..................and yes the Sigma 150-600mm Sport lens with 2X Teleconverter autofocuses at 1200mm with the Nikon Z7.

This is the side by side comparison of Nikon 600mm f/4G AF-S VR at 1200mm and Sigma 150-600mm Sport at 1200mm, unedited captures from Digital Lens Comparisons.

Field Test Photos of Sigma 150-600mm with Sigma 2X 2001 Teleconverter, 1200mm Tested Focal Length

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