Basic Photography Terms And Concepts

In a shot to raised and additional totally perceive the word related to photography and ultimately, astrophotography, I complied temporary} list of common terms and their definitions similarly as some brief samples of their applications. enclosed area unit specific samples of my hardware setup and the way these terms apply to them directly.

Term <tl;dr>
Definition. extra data.

ISO <Gain>
Basically, gain. The trade-off being noise; the upper the ISO, the additional noise. A photographer’s rule of thumb is to ne'er bit the ISO till you can't get enough lightweight victimisation the aperture and shutter speed. For astrophotography, the upper the ISO (usually) the higher as a result of the sunshine is thus feeble and since ‘stacking’ and standardisation frames will counteract the noise.

Aperture <Size of lens/mirror>
The aperture is that the diameter of the first lens or mirror.

Focal length <Field of view; Longer distance, smaller FOV / shorter distance, wider FOV>
Focal length is that the distance (given in millimeters) between the telescope’s primary lens or mirror and therefore the purpose wherever the sunshine rays close focused . distance determines the FOV and magnification. distance determines image scale (for a given camera). Longer focal lengths and larger scopes area unit tougher to guide exactly (because of a smaller field of view).

Focal ratio <The lower the better; the quicker the pictures are often captured>
The f number is that the distance divided by the aperture. The f number is largely a live of however steep the sunshine cone is within the telescope or lense. It helps to link f number and F-stop; they’re similar concepts and have similar impact.  If you go from Associate in Nursing F8 scope to Associate in Nursing F5.6, you’re dropping a full Fstop and every sub can take 1/2 the time. f number determines how briskly you'll capture the image. Associate in Nursing f/9 scope goes to be higher for breakdown detail in galaxies, wherever as Associate in Nursing f/4 scope goes to be higher for imaging expansive swaths of sky full of immense nebula. F-ratio could be a matter of resolution, in the end. quicker (lower F number) scopes area unit difficult/expensive to form.

F/stop <The lower the better; the quicker the pictures are often captured>
Lenses area unit marked with a series of f/stops, all allows 0.5 the maximum amount lightweight because the previous one. The light-gathering ability of a lens is set by its space, and f/stops area unit determined by diameter. space is expounded to diameter square. The progression of f/stops, 1 – 1.4 – 2 – 2.8 – 4 – 5.6 – eight – eleven – sixteen – twenty two – thirty two, area unit powers of the root of two. the world of the outlet doubles and halves, it’s simply delineated  by a magnitude relation on the lens. The smaller the f/stop, the additional lightweight the lens gathers and therefore the ‘faster’ the lens is; the larger the f/stop, the less lightweight is gathered and ‘slower’ the lens is. once the f/stop is listed as a part of the specifications of a lens, the tiniest f/stop is given (i.e. the widest aperture the lens will achieve).

Photography ‘f/stop’ versus telescope f number
-In regular photography, the f/stop is technically identical issue because the f number (like telescopes), however you think that of it additional in terms of the ‘aperture,’ as a result of you'll manipulate the aperture in camera/lens photography and you can't with telescopes. Basically, for utilisation, the f/stop are often tho't of as substitutable with aperture – or what quantity lightweight is being let in (even though technically it’s completely different for various focal lengths and cameras).
-In physical science and with telescopes, the f number is vital as a result of it determines how briskly you'll capture a picture.

–Magnification / not very important—
Magnification
Focal length is that the major decisive issue of any given telescope’s magnifying power. At lower magnifications, the image is tiny, bright and well-resolved, however an excessive amount of magnification makes for nothing over a giant, fuzzy image. Telescopes will solely gather most lightweight and high magnification suggests that you’re simply spreading that very same quantity of sunshine over a bigger space – leading to useless or “empty” magnification. verify a telescope’s sensible magnification limits: Multiply the target lens or mirror’s diameter (in millimeters) by a pair of. for instance, a 100mm telescope would have a sensible magnification limit of 200X.

How To verify Your Telescope’s Magnifying Power
Divide the distance of the telescope by the distance of the ocular. for instance, if you've got a telescope that features a 1000mm distance and you're employing a 20mm ocular, you'll be obtaining 50X (1000mm/20mm = 50X). If you place a 20mm ocular in a very telescope with a 500mm distance, you’ll get 25X (500mm/20mm = 25x). that's why identical ocular seems to behave otherwise in several telescopes.

A longer f number means:
-A narrower field of read (see less of the sky at once), victimisation constant lense. Quality long f-ratio scopes ar typically nicknamed “planet killers”
-The scope contains a additional forgiving “depth of focus” (a wider sweet spot of focus)
-The telescope is usually longer and heavier than shorter focal ratios of constant scope sort (folded styles, like catatropic scopes, ar AN exception). so needs a sturdier, costlier mount.
-Longer focal ratios have a wider tolerance in style and manufacture. this implies that they're typically cheaper (for an identical quality of optics)
-Longer f number telescopes ar additional forgiving for lower-quality eyepieces
-Longer f number reflectors ar easier to collimate as a result of they need a wider tolerance for error

A shorter f number suggests that (basically reverse all of these points):
-A wider field of read (see additional of the sky at once), victimisation constant lense. betting on the precise f-ratio, these ar typically referred to as “wide-field” or “rich-field” scopes.
-The scope contains a additional unforgiving “depth of focus” (harder to urge the sweet spot of focus)
-The telescope is usually shorter and lighter than longer focal ratios of constant scope sort (so easier to move and handle, permits a lighter mount)
-Shorter focal ratios have a tighter tolerance in style and manufacture. this implies that they're either costlier (apochromatic refractors) or provide less excellent views (achromatic short-tube refractors that show millions of false color)
-Shorter f number telescopes ar less forgiving for lower-quality eyepieces, and usually need costlier eyepieces to urge the most effective views
-Shorter f number reflectors ar tougher to collimate as a result of they need a narrower tolerance for error

-My Telescope Examples-

Zhumell:
Focal length: 1250mm
Mirror diameter: 10in (254mm)
Focal ratio: f/5
Practical magazine. limit: 127x
Eyepiece: twelve.5mm – Magnification: 100x
Eyepiece: 9mm – Magnification: 139x

AT6RC:
Focal length: 1370mm
Mirror diameter: 6in (152mm)
Focal ratio f/9
Practical magazine. limit: 76x
Eyepiece: twelve.5mm – Magnification: 110x
Eyepiece: 9mm – Magnification: 152x

Images of my completely different setups let's say FOV:


Canon Greek deity T3 Rebel / 18mm-55mm Lens:
Photography terms


Canon Eos T3 Rebel / 75mm-300mm Lens (don’t mind the dust):
Photography terms


Canon Eos T3 Rebel / AT6RC FL: 1370mm, FR: f/9:
Photography terms

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