Canon 17-55mm f/2.8
A zoom lens with a big range, from slightly wide-angle to long telephoto. The 20 measures the range, some lenses are not so strong, say 10x.
There is not a specific cleanser that you need to use on your sony camera lens. You can use any that is made to clean camera lens' As long as they say that they are camera lens safe and that is what they were made for then you can use it!
Most photographers would consider an slr to be "normal". If it's not an slr or a tlr, then you must be referring to a range finder camera or monorail camera. I presume range finder. Thus the major difference is that an slr system presents to the viewing eye pretty much everything that the lens is bringing to the film (minus the parts where the circular image lies outside the film rectangle). A range finder attempts to do this with a separate small viewing lens usually mounted on the camera face off to one side of the lens. The angle of view of the main lens is not the same as the angle of view of the viewing lens, which is usually not a problem. But if you are close enough to a subject such as a flower and you place the camera according to what you see in the viewfinder, you will be too far off to one side and will get less than the whole flower in the picture. This effect is known as parallax.
The short focal length of a camera lens is so that the image the lens forms is small and can be focused on a piece of light-sensitive film.
its all about the glass (lens)
When taking long-distance nature photos, your lens is more important that the megapixels of the camera. Any DSLR (digital single-lens reflex cameras) should work well, paired with a good lens like a 600mm F4.
Your typical 35 mm SLR is designed to have the lenses changed while the film is in the camera, so it won't hurt a thing. I suppose it's possible that there is a camera out there that doesn't allow the lens to be changed mid-roll, but it's not likely. Usually the shutter is behind the lens, so no light will fall on the film from changing the lens.
Reflecting telescopes use mirrors to gather and focus light, while refracting telescopes use lenses. Reflecting telescopes are generally more compact and easier to manufacture at larger sizes, making them popular for modern astronomical research. Refracting telescopes are simpler in design and are commonly used for terrestrial observing and amateur astronomy.
Galileo created his first telescope in around two months in 1609. It was a refracting telescope with a convex objective lens and a concave eyepiece. This instrument revolutionized astronomy and allowed Galileo to make groundbreaking astronomical observations.
That is a tricky question, but it would be best to use two cameras, at the very least. Use one with long lens, something within the range of 70-200mm. Partner that with another camera with a wide angle lens, since this one would be great for candid shots and tight spaces.
I've used a 200 mm lens on a 35 mm camera for track events and football. It is a little long for portrait work, but may work OK for random candid people shots.