A telephoto lens has to incorporate a special lens group known as a telephoto group; nevertheless, non-telephoto lenses of long focal length are often informally referred to as telephoto lenses. The angle of view created by a telephoto lens is the same as that created by an ordinary lens of the same specified focal length.
Bower is known as an affordable lens manufacturer. So you can find any bower telephoto lens here.
Bower 500mm f/8.0 Manual Focus Telephoto Lens
Filter Size: 30.5mm (rear)
f/Stop Range: f/8.0 (fixed)
Minimum Focus Distance: 5.6′ (1.7 m)
Angle of View: 4.1° x 2.7° (WxH)
2.7° x 1.8° (WxH) w/ APS-C (15 x 22mm) cameras
Length: 3.5″ (88mm)
Maximum Diameter: 3.0″ (77mm)
Weight: 0.70 lb (320g)
Bower 500mm f/6.3 Manual Focus Telephoto Lens
95mm front, 34mm rear
Minimum Focus Distance
6.6′ (2.0 m)
Not Specified by Manufacturer
Angle of View
4.1° x 2.7° (WxH)
2.6° x 1.7° (WxH) w/ APS-C (15 x 22mm) cameras
1.55 lbs (705g)
Avalailable also in other mount for Telephoto Lens for Canon, Contax, Minolta MD, Nikon, Olympus OM, Pentax, Sony/Minolta, Canon FD.