Focal Ratio

focal ratio Ratio between the focal length of a lens or mirror and its effective aperture. The focal ratio is often called the f-number. For example, a mirror of diameter 100 mm and focal length 800 mm would have a focal ratio of eight. This is often written as f8 or Jj8. It is a measure of how quickly light rays at the edge of the aperture converge as they approach the focus; astronomers sometimes refer to optical systems with low f-numbers as 'fast' and those with high f-numbers as 'slow'.

Suburban Messier project–gear? rules? company?

…magnification pretty fast. My one reservation about using the 90mm Mak is the long focal ratio–1250mm, or two inches longer than the XT10 even–which means…
Woodstock vs. Yoda: The Thrilla in Possum Swamp

… with the f/11. I still thought the image in the higher focal ratio scope was sharper, but maybe it was only a little sharper…

…just as your field of vision narrows as you look at something farther away. Focal Ratio is focal length divided by aperture. I think my telescope has…
Experiments and Failures

…: My primary imaging scope is an achromat with a fast focal ratio (f/5), which means there is significant chromatic aberration (CA) in …
A little question about my telescope?...

The magnification is the focal length of the telescope divided by the focal length of the eye piece. A 5m eye piece will give to x80 but I wouldn’t bother.Divid

The magnification in a refracting telescope is calculated in what way?...

A. Compute the ratio of the focal length of the eyepiece lens to the focal length of the objective lens


What is the angular magnification due to the microscope?...

to be practical–angular magnification through two focal points—is un important —for the brain–compensates—however angular magnification can be achieved

Which telescope would be best for beginners?...

Whatever you buy, get one that can be used as a spotter scope later on a larger telescope, should you decide to pursue the hobby. I bought a Celestron that I w

College Astronomy - Calculating the F-Ratio of a lens?...

Hi. The focal ratio is explained here. Sorry, too tired to type. ratio (F-number) of a lens is

What is the most important function of a telescope?...

c.)A — light gatheringThe usual answer is a)
but I think it is a tie between a) and b).

c) is really only a byproduct of b) or maybe enabled by b)

d) is not

Meade LightBridge

AMAZON CANADA NEW OFFER Product Description Meade LightBridge Aperture: 10-Inch. Focal Length: 1270mm. Focal Ratio: f/5. It’s not just a big telescope. It’s a big telescope that goes any

Canon 5D Mark II 2 HD Video: Moon Dec 03 2008 Mike the Teacher

The Moon through a Canon 5D Mark II [2] in HD Video Mode. Camera is T-Mounted to a Celestron C6-A Telescope: Optical Design :Schmidt-Cassegrain. Optical Lens Diameter :6.0” (152mm). Focal Length :59.

Grinding a 12.5-inch telescope mirror with 5-micron Aluminium Oxide

Last stage of grinding a 12.5-inch telescope mirror blank with an 11.5-inch tool. The tool consists of ceramic tiles arranged on a convex surface that matches the curve of the mirror (roughly f/4 foca

moon lab :) oct 2011 moon watch in

i used no barlows just my HD cam sony on the back of my scope Primary mirror diameter 250mm Focal length 1700mm Focal Ratio f6.8 *Tube Weight (inc. mount plate/dovetail) 12kg

10 Things: Connections, coaching pedigree led Kirk Olivadotti to Georgia

…“She's doing well,” said Olivadotti, who also has a 3-year-old boy named Kruz. “She's still being actively treated, but she is going to start kindergarten this year and we're all excited about that. In between being a cancer patient she's just a 5-year

My first D3x Image.

focal ratio

Virgin Air Ambulance

focal ratio

fountain-II Nora City

focal ratio

Scale comparison, spotting scope, lowest zoom

focal ratio

Voigtlander 15-35mm Zoom Finder, Black
Voigtlander 15-35mm Zoom Finder, Black Focal Length: 15-35mm Macro Ratio: 0.22-0.47 Diopter: -1.0 ~ -0.3 Lens Construction: 7 groups 8 elements Diopter adjustment: +1.3/-2.8 Parllax distance : 1m Eye point: 15mm from the last element Eye poi

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Tamron AF 70-300mm f/4.0-5.6 Di LD Macro Zoom Lens with Built In Motor for Nikon Digital SLR

The Tamron 70-300mm f/4-5.6 Di LD Macro Autofocus Lens is a quality, compact ultra tele zoom which covers the 70mm to 300mm telephoto range, with a ma

Celestron 21035 70mm Travel Scope

Travel Scope 70 was designed with traveling in mind. Highest quality materials used to ensure stability and durability. Minimal maintenanceThe Celestr

Evertech CCTV Security Camera SONY EFFIO – 700 TVL, 36 IR, 2,8~12mm Wide Angle Z

With robust weatherproof and vandal resist casing, this indoor/outdoor camera is ideal for your surveillance applications and it works well in the are

The Golden Ratio, How To Use It In Photography

…ch has been around for a very long time.

It wasn’t, however, until the Renaissance Period that architects, artists and even designers took to using the infamous “divine proportion”. They did so to make their work more aesthetically pleasing. By using some mathematical principles they determined where to …