2x Kenko TC test

[Mickoid]

Tonight, after picking up a second hand Kenko Teleplus 2X Teleconverter, I thought I'd give it a test before moonrise. I coupled it with a 200mm Sun prime lens for an effective focal length of 400mm and shot 3 x 120sec unguided subs at 1600 iso using my modded Canon 550d and UVIR cut filter. Patchy cloud and the roof of my house prevented any further data being collected but I was relatively pleased with the result shooting jpegs with no calibration frames. Costing just $10, this TC was a real steal! :)

[AstroViking]

What a bargain...

Does the TC have much impact on exposure time? I've read that a 2x TC can "cost" you 2 or 3 f-stops under daylight photography.

Although I guess with astro, you can just bump up the ISO or stretch out the exposure time...

Cheers,
V

[Mickoid]

Steve, you're right, you lose two f stops with a 2X Converter. The Sun lens I used was a f 2.8 so it becomes f 5.6 with this converter. I've made a f 8 external aperture for this lens to reduce CA. I just increase the exposure to compensate.