Astro terminology and abbreviations
Are you also, like me, going nuts from the adds in YouTube videos and not finding the scene with the info you're looking for? Presenters that talk like having to catch the last train which can be really hard if you do not have a good comprehension of the english language let alone with all the accents?
How about any written documentation on terminology and abbreviations and other basic knowledge on astrophotography or just viewing that you can let sink in and compare and quickly search?
I don't have all information or answers, far from that... but that is the exact reason for building this page...
As I am growing into this myself this page will be frequently updated.
Example:
WTFATATA = What The Fuck Are They All Talking About...🤓.
Adapter (rings) = Also known as 'Spacers'. Rings to place between the telescope and the camera to get to the backfocus distance (more on this)
ADC = Analogue to Digital Converter. Photography parameter. Click the link for explanation in context.
ADU = Analogue to Digital Unit. Photography parameter. Click the link for explanation in context.
Alt(itude)azimuth Mount = Mount that does not align with the Earths rotational axis
Apogee = nearest point of an object to another object (like Moon to Earth)
Backfocus = the point behind the back port of the telescope where the focal plain is. Focussing takes place in this focal plain. So if the eyepiece or sensor is not in the focal plain you will have a challenge to obtain a focussed image.
Barlow = a lens to place between the telescope and the eyepiece or camera to double or triple the focal length. There are many types depending on the magnification and quality you want or can afford (more on this)
Bias frame = A very short exposure with the cap closed. The electronic read noise without any amplification by long exposure time or temperature etc. In night photography that is being enhanced excessively this shows up as an ugly pattern.
Calibration = Process of stacking the Light frames with the dark frames, the flat frames and the bias frames, register them, normalize them and composite them in order to further process the result.
CFZ =
The Critical Focus Zone (CFZ) of a telescope is the range within which the focus is acceptably sharp for astrophotography. Determined by the telescope's focal ratio, the CFZ is narrower in faster (lower f-number) telescopes, demanding precise focusing to capture clear, detailed images of celestial objects.
Circumpolar = Objects that stay above he horizon the whole day
Compositing = While stacked determining which values of the stacked pixels will be discarded. 10 stacked images means 10 values of every pixel. By discarding values that deviate to much, noise and trails of satellites and planes and meteors will be filtered out. This can be done in various statistical ways like Mean, Median, Sigma-clipping etc.
Dark flat frames = Special type of dark frames captured at the same exposure of flat frames. This is used to calibrate the flat frames.
Dark frame = A frame captured with the same settings as the light frame (same temperature, exposure time and binning) but with the cap closed so that no light reaches the sensor. This is used to record the electronic noise generated by the sensor without any light. This is used to remove noise from the light frames.
Declination = In astronomy, declination (abbreviated dec; symbol δ) is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or south (negative) of the celestial equator, along the hour circle passing through the point in question. When paired with right ascension, these astronomical coordinates specify the location of a point on the celestial sphere in the equatorial coordinate system.
Deep Sky = nebulae, galaxies, IFNs, big to huge objects in the sky so much less magnification than with planetary viewing/photography
Diagonal = Probably one of the winners of the SNC aka Stupid Naming Contest. It is the prism or mirror behind the telescope that reflects the image at a 90 degree angle so you can watch from the side of the scope or downward instead of using a huge tripod to lift the scope high enough to be able to look directly through it and way to high to get it there. A decent name would be something like side view mirror or something like that.
Dynamic range = Distance in bits between details in highlights and in shadows or between read noise and full well. Photography parameter. Click the link for explanation in context.
EAF = Electronic Automatic Focusser
EKOS is an advanced cross-platform (Windows, OSX, Linux) observatory control and automation tool with particular focus on Astrophotography.
ERF = Energy Rejection Filter. This is basically a lid with a hole to prevent to much sunlight from entering your scope while photographing or just observing the sun through a special device (quark). The example is an off-axis type for SCT type scopes.
Exposure time (optimum) = Exposure time resulting in maximum details and minimum read noise. Photography parameter. Click the link for explanation in context.
Eyepiece = the lens you look into at the end of the telescope. There are many types depending on the magnification and quality you want or can afford (more on this)
Equatorial Mount = Mount that aligns with the Earths rotational axis
Flat frame = A frame captured with the same settings as the light frame (same temperature, exposure time, and binning) but lit by a flat field light source (such as a LED panel). This is used to correct for optical things as vignetting and dust on the sensor
Focal length = A distance in (usually) mm of the focal point of the lens(system) being a measure for magnification factor.
Full well = Maximum amount of electrons to fill an ADU. Top border of Dynamic Range. Photography parameter. Click the link for explanation in context.
FWHM = Full Width Half Maximum. See "HFR".
Gain = "Sensitivity' regulator like ISO value. Photography parameter. Click the link for explanation in context.
Gain offset = extra added gain to rise above read noise in order to get more details in low light and prevent information less black pixels. Photography parameter. Click the link for explanation in context.
GEM = German Equatorial Mount
Guidance computer = Computer that is the centre of your system and that taker care of very many tasks and commanding camera and focussing and heating and mount and several other things. (more on this)
Guide scope = Separate small telescope parallel to the main telescope that provides the guidance computer with images of stars to hold on to. (more on this)
HFR or HFD or FWHM = Half Flux Radius/Diameter. The most tried and tested method is Half-Flux-Radius (HFR), which is a measure of the width in pixels counting from the center of the star until the accumulated intensity is half of the total flux of the star. As you move closer to the point of optimum focus, the HFR gets smaller, reaching a minimum at the point of focus before increasing as you start to move away from focus. This information is used for (calibration of) autofocussing. Search this page for the V-Curve.
hiPs: Hierarchical Progressive Surveys. The hierarchical tiling mechanism which allows one to access, visualize and browse seamlessly image, catalogue and cube data.
Hyperstar = Strong reducer that makes an SCT (only) very fast. (more on this)
IFN = Integrated (by all, not only near, stars) Flux (lighted) Nebula (dust cloud in this case without star formation)
INDI is an instrument neutral distributed interface control protocol that aims to provide backend driver support and automation for a wide range of Astronomical devices (telescopes, focusers, CCDs..etc)
ISM = InterStellar Medium
Kstars is a complete desktop planetarium working together with Ekos and Indi
Light frame = The regular image captured by your sensor. It is called light because it captures the incoming light.
Losmandy = wide type of rail to mount accessories on the telescope or the telescope on a mount.
Mount = the clockwork that the telescope or camera is on and that counters the Earths rotation (more on this)
Nadir = opposite of Zenith
Nebula = dust 'cloud' with star formation more or less brightly lit bij (relatively or very) nearby stars
N.I.N.A. = NIGHTTIME IMAGING 'N' ASTRONOMY. An astrophotography imaging suite.
Noise = Rogue electrons causing pixels that have no relation to the image. Photography parameter. Click the link for explanation in context.
Normalizing = Equalizing the densities of upcoming moonlight, atmospheric changes, sudden light pollution etc. in stacked images.
OAG = Off Axis Guider
Optical Train = The total construction of lenses, extenders, filter(rotator)s, etc, and the camera behind the scopes exit point.
Oversampling = Having more pixels available for the smallest details the telescope can capture. As opposed to undersampling where there are less pixels than details. Example: the same star will take 4 pixels in oversampling while it is even smaller than a pixel in undersampling and therefor may not be visible.
Park(ing the telescope) = Park the mount to its parking position. The parking position varies from mount to mount. Some driver support custom parking positions while others support only one static parking position. For GEM mount, parking position is usually with the mount looking toward the celestial pole with the counter weights down.
Perigee = farthest point of an object to another object (like Moon to Earth)
Planetary = aimed at planets, moon and sun. It requires high magnification as the object is tiny in a huge sky
Plate solving = Plate solving is a method used to determine exactly where the telescope is pointing in the sky by comparing the star field in an image to a database of star positions. Upon matching the image's stars, the plate solving application returns the right ascension (RA) and declination (Dec) of the center of the image.
QE = Quantum Efficiency. Ability of a sensor of how much of a photon of a particular wavelength will produce an electron. It is one of the cameras specifications and it is not very clear. There has to be a graph or table in which is clarified how much of the photons of a certain wavelength will be converted in electrons.
Quark = device with filter (in combination with an ERF!!!) to observe the sun.
Read noise = Electrons generated by the sensor/lowest measurable photon energy. Photography parameter. Click the link for explanation in context.
Reducer = lens to reduce the focal length of the telescope and to get more light on the sensor or in the eypiece (more on this)
Refractor = Telescope built from lenses only, no mirrors.
Register(ing) = Fitting the images on top of each other in the stacking process. Pixel 1 on top of pixel 1, pixel 2 on top of 2, etc.
Right ascension = Right ascension (abbreviated RA; symbol α) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the Earth. When paired with declination, these astronomical coordinates specify the location of a point on the celestial sphere in the equatorial coordinate system..
Rotator = device to rotate the camera on the scope. For composition only you can use a small manual rotator but when you use the ALT/AZ mothod you need a computer controlled device that rotates the camera with the rotating sky because the ALT/AZ method pans but doesn't follow the rotation. In the linked page is more explanation but in Dutch. The manual version is there too (also available in M42).
SCT = Schmidt-Cassegrain Telescope
Seeing = Another one going for the SNC (Stupid Naming Contest) trophy. The seeing is the clearness and stability of the atmosphere through which light has to travel to reach you. On a hot day you can see the air vibrating. You see that very clear over an asphalt road heated by the sun. That will give you a challenge. Better name would probably be anything like 'Clearness'. (more on this)
Sidereal (rotation/day) = daily rotation of the planet Earth corrected by its shifted position with regards to the sun. So the REAL rotation as seen at the position of the stars.
Spacers = Also known as 'Adapter (rings)'. Rings to place between the telescope and the camera to get to the backfocus distance (more on this)
Swamping the read noise = Exposing to a level that the read noise is 'swamped'. Photography parameter. Click the link for explanation in context.
Syzygy = a roughly straight-line configuration of three or more celestial bodies in a gravitational system.
Undersampling = see oversampling for example (but the same video).
Unity gain = Gain point that 'fills' an ADU with one electron. Photography parameter. Click the link for explanation in context.
V-Curve = A graph showing the HFR measures to achieve focus.
Vixen = narrower than Losmandy rail to mount accessories on the telescope or the telescope on a mount.
WCS = World Coordinate Systems (WCSs) describe the geometric transformations between one set of coordinates and another. A common application is to map the pixels in an image onto the celestial sphere.