Posts Tagged: astrophotography

Your Cameras and Lenses are Crooked and How to Adjust Them

Plus a bunch of tidbits about some of the challenges in making astro-landscape photographs

Contents
TLDR Preface
Introduction
Choosing lenses for astrophotography
Establishing some standards
Your camera’s sensor is crooked
Adjusting the camera

IBIS Variation
Adjusting the lenses
Yet more alignment pitfalls
Possibly another method
Conclusions

TLDR Preface

Photograph of Milky Way Core in 2017

Silver River Shimmers, 2017
Photograph notes: This image is a composite of 4 vertical frames stitched for the sky and another 4 vertical frames stitched for the land for a total of 93.8 million pixels, using a Sony a7R II at ISO 800 and Canon EF 35mm f/1.4L II USM. Each of the sky frames was stacked and averaged from nine 32-second exposures at f/2.8. The land frames were stacked and averaged from four 32-second exposures at f/4 made 23 mins later at predawn to avoid shadows from the sun. 52 exposures were used in all. The sky exposures were tracked with a Sky-Watcher Star Adventurer.

In December 2017, it was first suggested to me by my friend and esteemed colleague, Joseph Holmes, that my Sony α7R II’s (or more commonly written as a7R II) sensor might be crooked relative to its bayonet mount. Don’t laugh yet, it’s not a problem exclusive to Sony. I had previously known about the same problem with digital medium format backs from precisely the same person, who put out two extensive articles on the topic over a decade ago, here and here. Neither of us wanted to believe this initially. One would certainly like to assume that 35mm format camera manufacturers, making single-unit camera bodies rather than modular system digital backs, could hold the sensors to tight enough tolerances with today’s technology. Alas, we discovered that it was not quite good enough for what we wanted from our cameras.

A diffuse and complex story unfurls, necessary for the explanation of small details in great detail. For anyone wanting the very best out of their powerful, modern, wide-aperture, breathtakingly-sharp lenses, on equally modern, high-resolution (read: highly revealing of alignment errors) digital cameras, photographing the most optically demanding subject matter in the known universe – the starry night sky – you will want to sit up and pay attention. It’s entirely fine if one does not care about subtle differences between what’s in-focus and out-of-focus. I would not soon be forgetting how many failed to appreciate the camera-shake induced blurring from the original Sony a7R violent shutter mechanism. If one only wants photos displayed no larger than Instagram thumbnails, none of this is pertinent and you should stop reading now. Alright then, some good news! We have fortunately found reasonable solutions to the worst problems. I share them below freely.

Continue Reading…