Project:
Sigma APO 150 mm f/2.8
vs
Pentax SMC 67 165 mm f/2.8

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

Content:

1. Camera lens vignetting
2. Histogram and vignetting
3. Analyze of Sigma APO 150 mm f/2.8 vignetting
4. Analyze of Pentax SMC 67 165 mm f/2.8 vignetting
5. Analyze of Pentax 67 at f/2.8 and at f/4.0
6. Pentax 67 165 mm lens mounted on a Canon full frame camera
7. Pentax 67 and Sigma APO star test at center
8. Pentax 67 and Sigma APO star test at corner

Note:
I take no responsibility or liability for what are written here, you use the information on your own risk!

8. Pentax 67 and Sigma APO star test at corner

It's amazing how good stars both of these lenses creates at the corners.

This is a crop of the extreme upper right corner of both full frame photos from both lenses, pixel scale 1:1.

Pentax 67 lens:

The lens is set at aperture f/2.8. The last mm in the corner the stars look a bit elongated, otherwise it looks sharper then the Sigma APO.

Sigma APO lens:

The lens is set at aperture f/4.0 . This lens is 30 years younger and stopped down to f/4.0, still it's not much better, or? Maybe worse then the older Pentax lens.

Conclusion:

I shall take more photos with the Sigma APO lens later now when I have more experience from it. The tracking wasn't very good when I took the Sigma photo. Now with the angled view finder connected to the polar scope it shall be much better. And I shall also reduce the exposure time to 30 seconds and take more of them.

Read here about the test I did with 30 and 120 seconds exposures:
../../tutorials/tutorial-dynamics/tutorial-05-dynamics.html

I have updated the M45 photo with an image with back ground cancelation of the Pentax image:
../../my-astronomy-photo/open-clusters/m45-open-cluster.html

Very cloudy these days, but I really hope to get a clear night so I can take photos of the comet 46P/Wirtanen, it come close to M45, that can be a very nice photo. To this I will use the Sigma lens.