On Mon, Nov 11, 2019 at 04:16 AM, <debojyoti.pal.007@...> wrote:
Vivitar 650-1300mm with multiple(3) 2x tele-converters giving me 2600mm, 5200mm and 10400mm focal lengths. Am I in the right path? Can I get high end telescope level photographs?The longer the focal length, the harder things become. Even with a 1300 mm 8 inch Celestron SCT, things are hard.
So, 2600mm is out of the question, and of course the higher focal length.
Stay below 1000mm or 800mm, and you can get good results.
Most amateurs use 500mm or 600mm, and get great shots.
Another thing is that a tele converter increases the F-stop.
So, if your zoom is originally F/5.6, it will be F/11, and requires double the exposure time (assuming everything else remains the same, aperture, ISO, ...etc.)
Usually no one attempts astrophotography with anything that dimmer than F/8. And for serious work, it has to be F/6 or F/4.