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Sticky with terms, phrases, shorthand and other things a person new to Astrophotography should know

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#1 GaryCurran

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Posted 17 June 2015 - 12:32 AM

I'm looking through these threads, and I don't recognize a lot of terms.  Now, I've been reading and researching this stuff for a while, but I admit, I don't even know 1% of what I should.

 

So, would it be possible to create a sticky, or even use this one as a beginning, for terms we don't know, or should know?  I can start it, if people want to add to it.

 

A

AP.  Short for Astrophotography.

 

Auto Guiding.  The process of controlling a motorized mount to keep an object, usually a star, in a stationary position in relationship to the imaging camera.  Auto Guiding is used for long term photography where it is essential to keep the image in the same place.

 

Auto Guider.  A device, usually a camera, that detects the presence of an object, usually a star which is used as a Guide Star.  The camera or device detects movement of the star away from a fixed and known position, and via software, often running on a computer, moves the motorized mount that the device or camera is mounted on back into the original position.  

 

B

Bias Frames.

C

Camera.  A device to record photons to a recording medium.  For much of the recorded history of Astrophotography, the recording medium was film.  However, with the advent of digital electronics, the medium may now be a sensor with converts the photons into electrons for electronic storage and manipulation.

 

CCD.  Charge Coupled Device.  A type of electronic sensor for conversion of photons to electrons in a digital camera.  CCDs were often the first generation of sensors in Digital cameras, having now been replaced with CMOS sensors.  CCD sensors are still used in high end Astrophotography Imaging cameras.

 

CMOS.  Complimentary Metal-Oxide Semiconductor.  A type of electronic sensor for conversion of photons to electrons in a digital camera.  CMOS sensors are the primary sensor types in most consumer digital cameras.

 

Coma.  A monochromatic aberration of a lens or other optical system in which the image from a point source cannot be focused.

 

Coma Corrector.  A device that fits in the optical pathway of certain types of telescopes to reduce the effects of coma on images.

D

Dark Frame.  An image that is captured where no light is allowed to reach the sensor or medium.  This is used in some programs to determine if the sensor has any defective pixels, in the case of an electronic imaging camera.

 

DSLR.  Digital Single Lens Reflex.  A type of camera derived from the Single Lens Reflex camera, where the images are bounced off a mirror, to another mirror and into the viewfinder.  When the shutter release is pressed, the mirror pivots up and out of the way, the shutter opens, and the medium is exposed to the light.  Sony Corporation has done away with the Reflex design, instead replacing the mirror with a translucent device that allows the light to pass through while reflecting a small portion of the light to a secondary sensor which feeds a small monitor in the viewfinder.  Sony refers to these cameras as SLT, or DSLT.

 

DSS.  Shorthand for DeepSky Stacker.  A program that will take multiple images and stack them together to increase the quality of the images.

 

Duration.  The length of time the camera is recording information.  It is also called Exposure

E

Exposure.  The length of time the camera is recording information.  It is also called Duration.

F

Field.  The area covered by the telescope/camera combination.  Often referred to as 'The Field of View.'  In terrestrial photography, it may also be called the "Depth of Field", but that does not apply to Astrophotography.

 

Field Curvature.

 

Field Flattener.  An optical device that fits in the optical pathway that is designed to reduce or eliminate field curvature in certain styles of telescope.

 

Filter.  A device, usually optical, that blocks certain wavelengths of energy.  Filters may fall into several categories, including Broadband, Narrow band, and Emission.  There are also Neutral Density Filters which block all wavelengths to a degree to reduce the amount of light entering the eyepiece or imagine device.

 

Flat.

 

Focal Reducer.  An optical device that fits in the optical pathway of a telescope to reduce the image size.  As a byproduct of reducing the size, it also increases the 'speed' of the telescope.  Typical Focal Reducers are f/6.3 for a Schmidt Cassegrain f/10 telescope.  Your imaging duration will be shorter, by possibly up to 50%.

 

Frame.  A single image.  Often used in reference to videos, a frame is one image out of many.  It may also be used for a still photo to indicate one image out of several if the photographer is shooting multiple images of the same object.

G

GEM.  A shorthand term for German Equatorial Mount.

 

German Equatorial Mount.  A type of mount that once Polar Aligned, will allow you to move the two axis' to a specific location.  Once there, only one axis, the Right Ascension axis, then needs to be moved to track an object across the sky.

H

Hά  Hydrogen Alpha.  A spectral line that shows Hydrogen-Alpha emissions.  The Hά emission is 655nm and shows as RED.  In additiona to Oxygen-III and Sulfur-II, they make up the 'Hubble Palette.'

 

Hubble Palette.  A series of 'false color' filters, consisting of Hά, O-III and S-II.  These spectral emission lines are mapped to Red, Blue and Green.  They present an image which would not normally be seen by the human eye as an image that can be seen.  In combination with RGB, or Red, Green, Blue colors, they can combine to present surrealistic images.

I

Image.  The output of a camera after an exposure to light.

 

Integration.  The total time of imaging.  If you take 10 subs or images of an exposure of 60 seconds each, your Integration time is 600 seconds

 

Intervalometer.  A device that controls when a camera will take a photo, and how many times.  Often used with a DSLR, or DIgital Single Lens Reflex camera, they allow the operator to set the number of exposures, length of exposure and time between exposures.  This allows the photographer to set the camera up for a 30-45 minute imaging session and not need to worry about the camera.

J

K

L

Light.  Energy in the form of Photons.  Our rods and cones of our eyes are stimulated by such energy, allowing us to see.  Electronic imaging sensors and film medium also are effected by such energy to create an image.

M

N

O

O-III.  Oxygen Three.  An Emission Spectrum that is caused by the Oxygen III molecule.  An O-III filter allows only that emission to pass through.  It is part of the Hubble Palette used for False Color images.

P

Pixel.  The smallest part of an imaging sensor.  A sensor may have millions of pixels.  Pixels are combined together to form a complete image.

 

Post Processing.  The workflow in any variety of software programs used to enhance your image or images into a final image.  It may involve 'stacking', 'layering' or other processes.  Software might include DeepSky Stacker, Photoshop or other software titles.

Q

R

RegiStax.  A software program to take a video file, usually planetary video, and sort and combine frames to deliver a single image.

S

S-II  Sulfur II.  An Emission spectrum that passes light from the Sulfur-II molecule.  It is used as part of the Hubble Palette for False Color Imaging.

 

Stacking.  A process of layering several subs to create one image, blending the images together.

 

Subs.  'Sub Exposures.'  One of many images taken of your subject that will be stacked together in Post Processing to create the final image.

 

T

U

V

W

X

Y

Z
 


Edited by GaryCurran, 18 June 2015 - 07:46 PM.


#2 Madratter

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Posted 17 June 2015 - 06:47 AM

I have a small FAQ on my site that covers some of the issues.

 

http://astroimages.w...-questions.html



#3 GaryCurran

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Posted 17 June 2015 - 11:50 AM

Mad,

Thanks for the link.  What my hope is that this turns more into a Glossary instead of a FAQ.  You did answer my question on 'subs' though.  :)  I mean, I basically knew what they were, but I didn't know why they were called that.

 

If you can add terms that an Astrophotographer uses that someone who is totally new to AP probably wouldn't know, that would be totally awesome.  That way, someone who doesn't know what a sub is can look and say 'Oh, alright, now I know what that person is talking about when they said they did 50 subs.'

 

My hope, anyway.  :D

Gary



#4 pjmulka

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Posted 01 January 2017 - 04:24 PM

RDF - Red Dot Finder
Telrad - Similar to a red dot finder where a larger bullseye is projected onto a small piece of clear glass.
RACI - ???

#5 Jerry Lodriguss

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Posted 01 January 2017 - 05:09 PM

Here's my glossary of astrophotography terms:

 

http://www.astropix....OP/GLOSSARY.HTM

 

Jerry



#6 MikeKy

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Posted 01 January 2017 - 05:16 PM

RACI = Right Angle Correct Image.  Refers to a finder with a 90 degree (right angle) diagonal with a view that is not inverted.



#7 RandallK

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Posted 01 January 2017 - 10:29 PM

Don't forget Gary,

 

M is for MONEY.....Lots and lots of money!!


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#8 Michael Covington

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Posted 01 January 2017 - 11:13 PM

OSC - One-shot color camera (one with a Bayer matrix, giving alternating red, green, and blue pixels)



#9 Phil Hosey

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Posted 02 January 2017 - 08:28 AM

FPN?  I'm guessing from context it's Fixed Pattern Noise?


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#10 APshooter

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Posted 02 January 2017 - 09:36 AM

B Mask:  Bahtinov Mask.  The Bahtinov mask is a device used to focus small astronomical telescopes accurately. It was invented by Russian amateur astrophotographer Pavel Bahtinov in 2005.

 

ADC:  The ADC, or Atmospheric Dispersion Corrector, reduces prismatic smearing during planetary imaging, resulting in images with finer details.



#11 Michael Covington

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Posted 02 January 2017 - 09:56 AM

FPN?  I'm guessing from context it's Fixed Pattern Noise?

Right.  Comprising PRNU, Pixel Response Non-Uniformity, as well as fixed-pattern bias.



#12 UlteriorModem

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Posted 02 January 2017 - 10:53 AM

ADU = Analog to digital units (I think) a unit of conversion for measuring pixel saturation in ccd type cameras,

 

While were at it "Full Well capacity" - The point of 'maximum saturation' for a pixel

 

SGP - Sequence Generator Pro

 

DSS - Deep sky stacker

 

SAD - Starless Astronomer disorder (Caused by clouds)


Edited by UlteriorModem, 02 January 2017 - 10:54 AM.


#13 PLShutterbug

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Posted 20 August 2020 - 07:26 PM

Not sure if this glossary is still being maintained. It almost looks like “no” ...

 

Vanguard, your definition:

 

”Field.  The area covered by the telescope/camera combination.  Often referred to as 'The Field of View.'  In terrestrial photography, it may also be called the ‘Depth of Field,’ but that does not apply to Astrophotography.”

 

... is not quite correct. I’m a long, long-time photographer, brand-new to astrophotography.

 

I have learned your definition of “field of view” for astronomy is essentially what you say: it is the apparent angle of view, or angle covered by the imaging system.

 

In terrestrial photography it has the same meaning. A particular lens has a field of view measured in angles. The shorter the lens, the wider the angle it captures and this is essentially the field of view. However, this has basically nothing to do with “depth of field” (DOF). DOF is the distance in front of, and behind, the principal point of focus that remains “acceptably sharp.” DOF is a function of the aperture, or f-stop chosen. The lower the f-stop, the less DOF. As the lens’s focal length increases relative to the size of the sensor (or film ...), and as the distance to the subject decreases, DOF decreases.

 

Assuming you are keeping up this glossary, a better definition would omit the final sentence that discusses terrestrial photography.


Edited by PLShutterbug, 20 August 2020 - 07:28 PM.



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