Opteka's extreme budget telephoto kit — the 650-1300mm with 2x converter for maximum reach.
The Opteka 650-1300mm f/8-16 with 2x Converter is a budget extreme telephoto zoom providing up to 2600mm reach with the teleconverter. Opteka produces ultra-budget photography accessories. The f/8 is already very slow; the 2x converter makes it f/16 — essentially unusable except in the brightest conditions. A novelty extreme telephoto.
The 650-1300mm at f/8-16 is extremely slow — requiring very bright conditions. With the 2x converter at 2600mm f/32, it is essentially a novelty specification. Image quality is basic at best. The extreme reach sounds impressive but practical use is severely limited by the very slow aperture. A budget curiosity rather than a practical photographic tool.
Mount varies via T-mount adapter. Weight very heavy for the cheap construction. Build quality budget. The T-mount adapter system enables mounting on various camera systems. Manual focus at 1300mm+ is extremely difficult. A tripod is absolutely essential. The 2x converter degrades already basic image quality further.
Very cheap — the cheapest path to extreme telephoto. Image quality is poor. The extreme specifications are a novelty. Not recommended for any serious photography. A fun curiosity at minimum cost. The practical limitations of f/8-16 at these focal lengths make most shots impossible except in bright daylight.