Big black dot?

[Jack123456]

Hi,

I've got an adapter to mount my camera for afocal photography and i have been taking some test shot during the day.

I couldn't help but notice a big black dot in the middle of the shots.

could someone tell me what they are, and how to get rid of them?

i was using a fujifilm s1600 with my 150p and a stock 25mm ep

[Jack123456]

oops, forgot the photo

[Cornelius Varley]

The big black dot is the out of focus reflection of the primary mirror. You won't see it when imaging at night time.

Peter

[Jack123456]

Thanks Peter

Thats just what i wanted to hear

[swag72]

The big black dot is the out of focus reflection of the primary mirror. You won't see it when imaging at night time.

Peter

Presumably though, even when imaging at night that dark reflection will affect anything right in the middle of the frame? Just wondered as I use a refractor, so not really seen this phenomenon before.

[Cornelius Varley]

In the example picture the doughnut is an out of focus highlight and the telescope is focused on something close to. The source of the doughtnut is out of focus and the highlight resembles the shape of the aperture, in this case the primary with the secondary shadow. In a normal camera, with an aperture ring, the out of focus highlight would look like the shape of the aperture ring. Normally the out of focus highlight wouldn't show up in astrophotography because the telescope is focused at near infinity.

Peter

[davidlf]

Theres me thinking it might be the worlds first photo of a black hole....