Barlow & SLR on Telescope

[Scott M]

Hi
I have an interesting question...I took some photos for the 1st time through my christmas pressie telescope (8" reflector) using a DSLR with T-adapter screwed into the back of a 2X barlow. I took photos of the moon (as it was pretty much full and I couldn't see a lot else, besides, I had yet to buy batteries for the motor, so was limited to short exposures). I also took photos piggybacked using a 300mm lens.

When I compared the piggybacked photos to the barlow photos, the moon was 10x bigger. This means that I was getting a focal length of 3000mm through the 2X barlow.

Since it was a 2X barlow, and the telescope focal length is 1000mm, why wasn't I getting 2000mm??

cheers

[interstellaryeller]

All I can say is that a 2x barlow will double your power while cutting the light by 2x, and your t adaptor without a lens also acts like a barlow to some extent.