Editing Astrophotography (section)

=== Media ===
Images are recorded on many types of media and imaging devices including [[single-lens reflex camera]]s, [[35mm format|35 mm film]], 120 film, [[digital single-lens reflex camera]]s, simple amateur-level, and professional-level commercially manufactured astronomical CCD and CMOS cameras, [[video camera]]s, and even off-the-shelf [[webcam]]s used for [[Lucky imaging]].

The conventional over-the-counter film has long been used for astrophotography. Film exposures range from seconds to over an hour. Commercially available color film stock is subject to [[Reciprocity (photography)|reciprocity failure]] over long exposures, in which sensitivity to light of different wavelengths appears to drop off at different rates as the exposure time increases, leading to a color shift in the image and reduced sensitivity over all as a function of time. This is compensated for, or at least reduced, by cooling the film (see [[Cold camera photography]]). This can also be compensated for by using the same technique used in professional astronomy of taking photographs at different wavelengths that are then combined to create a correct color image. Since the film is much slower than digital sensors, tiny errors in tracking can be corrected without much noticeable effect on the final image. Film astrophotography is becoming less popular due to the lower ongoing costs, greater sensitivity, and the convenience of [[digital photography]].

[[File:Milky_way_-route_292_shiga_kusatsu_road-_1920x1080.webm|thumb|left|Video of night sky made with [[DSLR camera|DSLR camera's]] [[Time-lapse photography|time-lapse]] feature. The camera itself is moving in these shots on a motorized mount.]]

Since the late 1990s amateurs have been following the professional observatories in the switch from film to digital CCDs for astronomical imaging. CCDs are more sensitive than film, allowing much shorter exposure times, and have a linear response to light. Images can be captured in many short exposures to create a synthetic long exposure. Digital cameras also have minimal or no moving parts and the ability to be operated remotely via an infrared remote or computer tethering, limiting vibration. Simple digital devices such as [[webcam]]s can be modified to allow access to the focal plane and even (after the cutting of a few wires), for [[Exposure (photography)|long exposure]] photography. Digital video cameras are also used. There are many techniques and pieces of commercially manufactured equipment for attaching [[DSLR camera|digital single-lens reflex (DSLR) cameras]] and even basic [[Point-and-shoot camera|point and shoot]] cameras to telescopes. Consumer-level digital cameras suffer from [[image noise]] over long exposures, so there are many techniques for cooling the camera, including [[cryogenics|cryogenic]] cooling. Astronomical equipment companies also now offer a wide range of purpose-built astronomical CCD cameras complete with hardware and processing software. Many commercially available DSLR cameras have the ability to take long time exposures combined with sequential ([[Time-lapse photography|time-lapse]]) images allowing the photographer to create a motion picture of the night sky. CMOS cameras are increasingly replacing CCD cameras in the amateur sector.<ref>{{cite web |title=CCDs, CMOS, and the Future of Astrophotography |url=https://skyandtelescope.org/astronomy-blogs/imaging-foundations-richard-wright/ccds-cmos-and-the-future-of-astrophotography/ |website=Sky and Telescope |publisher=American Astronomical Society |access-date=1 March 2023}}</ref> Modern CMOS sensors offer higher quantum efficiency, lower thermal and read noise and faster readout speeds than commercially available CCD sensors.<ref>{{cite web |title=CMOS VS CCD data. Which one is the best?  |url=https://telescope.live/blog/cmos-vs-ccd-data-which-one-best |website=Telescope Live |publisher=Telescope Live Ltd |access-date=8 November 2024}}</ref>

====Post-processing====
[[File:Bob Star - M45 Carranza Field (by).jpg|thumb|left|The Pleiades Star Cluster photographed with a 6 megapixel DSLR connected to an 80mm refracting telescope piggybacked on a larger telescope. Made from seven 180 second images combined and processed in Photoshop with a noise reduction plugin.]]

Both digital camera images and scanned film images are usually adjusted in [[Digital image processing|image processing]] software to improve the image in some way. Images can be brightened and manipulated in a computer to adjust color and increase the contrast. More sophisticated techniques involve capturing multiple images (sometimes thousands) to composite together in an additive process to sharpen images to [[Astronomical seeing#Overcoming atmospheric seeing|overcome atmospheric seeing]], negating tracking issues, bringing out faint objects with a poor [[signal-to-noise ratio]], and filtering out light pollution. 

Digital camera images may also need further processing to reduce the [[image noise]] from long exposures, including [[dark frame subtraction|subtracting a “dark frame”]] and a processing called ''image stacking'' or "''[[Shift-and-add]]''". Commercial, [[freeware]] and [[free software]] packages are available specifically for astronomical photographic image manipulation.<ref>{{cite web|author=Chan, Maria|year=2022|title=Best Astrophotography Stacking Software [Ultimate Guide]|url=https://dopeguides.com/astrophotography-stacking-software/|access-date=2022-08-14}}</ref>

"[[Lucky imaging]]" is a secondary technique that involves taking a video of an object rather than standard long exposure photos. Software can then select the highest quality images which can then be stacked. <ref>{{Cite book|last=Gladysz|first=Szymon|title=Adaptive Optics Systems |chapter=Lucky imaging and speckle discrimination for the detection of faint companions with adaptive optics |editor-first1=Norbert |editor-first2=Claire E |editor-first3=Peter L |editor-last1=Hubin |editor-last2=Max |editor-last3=Wizinowich |date=2008 |chapter-url=https://www.researchgate.net/publication/329770189 |volume=7015 |pages=70152H |doi=10.1117/12.788442 |bibcode=2008SPIE.7015E..2HG |s2cid=121543131 |series=Proceedings of SPIE}}</ref>

==== Color and brightness ====
Astronomical pictures, like [[observational astronomy]] and photography from [[space exploration]], show astronomical objects and phenomena in different colors and brightness, and often as composite images. This is done to highlight different features or reflect different conditions, and makes the note of these conditions necessary.

Images attempting to reproduce the [[False color#True color|true color]] and appearance of an astronomical object or phenomenon need to consider many factors, including how the human eye works.  Particularly under different atmospheric conditions images need to evaluate several factors to produce analyzable or representative images, like images of space missions from the surface of [[Mars]],<ref name="Don Davis Space Art t191">{{cite web |title=Martian colors |url=http://www.donaldedavis.com/PARTS/MARSCLRS.html |access-date=2024-05-04 |website=Don Davis Space Art}}</ref> [[Venus]]<ref name="Singapore 2021 g242">{{cite web |last=Singapore |first=AFP |date=2021-01-24 |title=This image has been enhanced from a photo of Venus taken by Soviet spacecraft Venera 13 |url=https://factcheck.afp.com/image-has-been-enhanced-photo-venus-taken-soviet-spacecraft-venera-13 |access-date=2024-05-04 |website=Fact Check}}</ref><ref name="Mitchell j874">{{cite web |last=Mitchell |first=Don P. |title=Images of Venus |url=http://mentallandscape.com/V_DigitalImages.htm |access-date=2024-05-04 |website=Don P. Mitchell}}</ref><ref name="Mitchell 1959 f372">{{cite web |last=Mitchell |first=Don P. |date=1959-10-07 |title=Soviet Space Cameras |url=http://mentallandscape.com/V_Cameras.htm |access-date=2024-05-05 |website=Don P. Mitchell}}</ref> or [[Titan (moon)|Titan]].