Astrophotography: It's All About the Details!

The DSLR Viewfinder: A Hidden Reflection Trap!

Yesterday, while testing my new optical divider with the SX LodeStar autoguider, I had a sudden “aha!” moment about the critical importance of a viewfinder cap on a DSLR!

With the optical tube closed, during the day, and the observatory door open, without the viewfinder cap in place, a distinct reflection was clearly visible on my test image from the Lodestar through the optical divider:

Same test, but this time with the viewfinder cap securely in place:

The reflection is strikingly obvious in that first image. Imagine this at night: an unsuspecting computer screen or even a distant street light next to your DSLR could easily contaminate your final image with a nasty gradient or a bright spot, making post-processing a real headache.

Of course, lucky owners of dedicated astro CCD cameras don’t have to worry about this particular issue.

This quick little test just goes to show, yet again, that in astrophotography, every single detail truly matters! Don’t forget that little cap!