6. The Software

6.1 ASCOM Platform

With different manufacturers producing different products of all kinds that connect to computers - mounts, cameras, etc - there was a need to unify everything under one common interface. This interface would allow software to interact universally with these devices regardless of manufacturer. From this need, AStronomy Common Object Model (ASCOM) was born. 

ASCOM are a set of drivers through which all devices are able to communicate together and software can take control of them. All software these days are based on ASCOM and require these drivers to be installed in order to communicate with the respective devices. Manufacturers of devices that connect to computers will supply ASCOM drivers of their own, based on the same principles. The ASCOM platform for Windows is completely free and can be downloaded from this external link to the official ASCOM website

The ASCOM platform must be installed before any other devices can be installed and before software can communicate with these devices. 

6.2 Mount Control: EQMod

Mounts these days come supplied with Hand Controllers. These provide the user with an interface to tell the mount its location on the Earth, to align the mount to Polaris, to slew the mount in any direction along Declination and Right Ascension as well as provide a database of thousands of objects (planetary and deep space) to go to. When a mount is connected to a computer, the Hand Controller is entirely bypassed and software must then take care of all of the Hand Controller's jobs. This is where EQMod comes in. EQMod is mount control software based on ASCOM, which will use ASCOM to connect to the mount and communicate with it. EQMod provides everything the Hand Controller does, except the object database (this is provided by other software). EQMod allows the user to set the mount's location on the Earth, perform a polar alignment, manually slew the mount among many other functions. 

At first, the EQMod graphical user interface is a bit intimidating. It is however well sectioned and little needs to be paid attention to. Under Mount Position, the current coordinates of the mount are displayed. Slew Controls allows the user to manually slew the telescope in any direction, with rates of movement definable here as well. Under Track Rate, the automatic tracking of the mount can be either disabled or enabled at a specific rate (e.g. Sidereal for deep space, Lunar for the Moon, Solar for the Sun or Custom for other objects such as comets). Below all this is a button to park the mount to the home position, which is the default starting position when the mount is set up and switched on. 

Site Information is where the user defines his/her location on the Earth, via GPS co-ordinates. Multiple locations can be saved for future use without having to remember or re-enter GPS co-ordinates. Within this section, the user can also perform a polar alignment, whereby EQMod slews the telescope to precisely the Right Ascension co-ordinates needed to centre Polaris in the mount's polarscope's Polaris reticule. This allows for an easy- and quick-to-perform, accurate polar alignment. Under Alignment / Sync, the user can see how many stars have been used for Goto alignment. This data can also be saved or erased. Under Park / Unpark, the user can control how and where the mount actually parks when the button is clicked. 

ASCOM PulseGuiding Settings and AutoGuider Port (ST4) Guide Rate are used to define how the autoguiding port on the mount responds to correction commands, in terms of the tracking speed used to apply these correction commands. Mount Limits can also be enabled and disabled (to allow the mount to point beyond the Meridian or horizon). The remaining sections of EQMod can be used for Periodic Error Correction (PEC) and configuration settings. 

A particularly useful feature of EQMod is that when starting it, one can either connect to a mount that's currently connected to the computer and switched on, or start an ASCOM simulator session. This simulator session behaves like a mount currently connected to the computer and all other software can connect to this simulated mount. This allows the user to test software and other functions without needing a physical mount to be set up. Overall, EQMod is a software replacement for the Hand Controller and use of this allows for much greater control of the mount. EQMod, commonly known as EQASCOM, is completely free and can be downloaded from this external link to the official EQMod downloads page

6.3 Precise Polar Alignment: Alignmaster

Polar alignment is a procedure required by all equatorial mounts. Carrying this out is generally fairly simple, as mounts tend to come with integrated polarscopes and either the mount's Hand Controller or software such as EQMod can aid the user in performing the alignment. The idea is to precisely align the mount to Polaris so that rotation along both axes of the equatorial mount will allow the mount to properly account for the night sky's movement, as well as the apparent field rotation (something alt-azimuth mounts are incapable of doing by their very nature). When an equatorial mount is not precisely aligned to Polaris however, field rotation can be apparent in fairly long exposures (which are common for deep space astrophotography). The error in a polar alignment can be estimated by a fairly simple yet ingenious method. Alignmaster is based on this method. 

Alignmaster first and foremost requires the user to be controlling the mount on a laptop via ASCOM. The user then enters his/her precise location co-ordinates into Alignmaster, checks the time matches the laptop's local time and then clicks Next. What comes up next is a list of pairs of stars, with ratings of Best, Good, etc. The aim is for the user to pick a pair of stars that is clearly visible and has the best rating possible (nearest the top of the list). What Alignmaster then does is slew the telescope to the first star. Inevitably, it will miss. The user is asked to use the mount's slew controls (i.e. EQMod's N, S, E, W buttons) to centre the star in an eyepiece (a crosshair eyepiece is good for this). Once centred, Alignmaster will slew to the second star. It will again inevitably miss and will ask the user to centre it. Once both stars have been slewed to and centred, given the amount of slewing the user had to perform, Alignmaster calculates the error in the alignment to Polaris. In order to correct it, Alignmaster then purposefully off-centres the second star by the same amount as the error calculated. The user is then asked to centre the star again, but not with slewing, but with the mount's altitude and azimuth bolts (the same ones used to perform the polar alignment to begin with). 

This method essentially aims to present the polar alignment error to the user with a good reference to correct it (a star that needs to be centred), and allows the user to correct it using the mount's altitude and azimuth bolts. Alignmaster finishes by asking the user if he/she wishes to repeat the procedure to narrow down the error further. Doing so once more normally reveals the polar alignment error to be much, much smaller. The more iterations are performed, the more accurate the polar alignment is. Generally however, two iterations suffices. Use of Alignmaster allows the user to have a very precise polar alignment with minimal effort and time (in contrast to other methods such as the popular drift alignment - watching a star drift slowly off-centre in a crosshair eyepiece and correcting for it). Alignmaster is not free but at €19, it is an absolute bargain. A trial version can also be downloaded. To download Alignmaster (or buy it), follow this external link to the official page

6.4 Precise Goto Alignment: AstroTortilla

It is common for newly set up mounts to have a level of error in terms of goto accuracy. In other words, asking the mount to aim at a certain object will lead to it pointing at it, but not 100% precisely. Hand Controllers for mounts tend to guide the user through a multiple-star alignment procedure. The idea here is that the user asks the Hand Controller to slew the mount to a certain star and the user is then asked to centre it in an eyepiece (a crosshair eyepiece is good for this). Once centred, the Hand Controller calculates corrections for the next goto and tends to slew to a second star to repeat the process. Two- and three-star alignment procedures are commonplace in order to perform a good goto correction. Though this procedure is more than sufficient for visual astronomy, it may not be the case for astrophotography as your target may still be slightly off-centre in your imaging frame. Ultimately, two- and three-star alignment procedures are governed by the human eye and are therefore subject to errors and these errors translate to goto inaccuracy. Thankfully however, we can take advantage of computer-control of a mount (via ASCOM). This is where AstroTortilla comes in. 

AstroTortilla takes advantage of computer-control (via ASCOM) and plate solves images. Plate solving is a process by which an image of deep space is analysed by software in order to determine precisely what it is that appears in the image (in terms of known objects and stars). How does this help with goto alignment? Very simple - an image is captured, knowing what the mount intended to point at, and is analysed to determine what it is that the mount is actually aiming at. This then allows a calculation of error (how far off-centre the target is) and thus correction by sending a slew command to the mount. This is the purpose and function of AstroTortilla. 

By connecting AstroTortilla to the mount and camera control software, AstroTortilla instructs the camera control software to capture an image and then uses its downloaded reference files (called astronomical index files) to analyse the image. Since AstroTortilla knows what object or star the mount should be aiming at, it can be made to automatically slew the mount to correct the goto error. Best of all, AstroTortilla can add an alignment point to EQMod so that future goto commands have this error correction applied (to make the goto precise). This precise alignment is required for mosaics of deep space spanning a number of nights. This is the case because from one night to the next, the astrophotographer must ensure the starting point for the mount is the same in order to make slews between adjacent mosaic segments accurate from night to night. The astronomical index files required for plate solving are downloaded during AstroTortilla's installation. They are selected by the user and need to cover the user's field of view, in order to account for the kinds of objects and stars expected in the images used in analysis. The tutorials page has a tutorial for AstroTortilla's installation and usage. 

Due to its nature, AstroTortilla requires the mount be controlled via a laptop (through ASCOM). Ideally, the camera should also be connected to the laptop in order to allow access to the images, through this is not strictly necessary as an image can be imported into AstroTortilla for analysis. AstroTortilla is free software and can be downloaded from this external link to the official website

6.5 Planetarium and Goto: Stellarium and Cartes du Ciel

In absence of a Hand Controller, a mount does not have access to a database of thousands and thousands of objects for goto. Generally, it is the Hand Controller's job to provide this database and some provide larger databases than others. SynScan is a popular Hand Controller system used by numerous mount manufacturers, including Skywatcher and Avalon. There is however a major advantage in using ASCOM software as planetarium software and that is complete control. You would no longer be limited by only several thousand objects and more importantly, you would not be annoyed by awkward, text-only menu systems. Both Stellarium and Cartes du Ciel support mount control (the former requires an additional plugin program, Stellarium Scope) and present you the night sky in its entirety in an interactive, real-time form. With simple selection (or search) and key presses, you are able to control precisely what object the mount aims at. 

The above screenshots demonstrate Stellarium, a personal favourite for its simple and beautiful interface (though it is more processor intensive to run on your laptop). The entire night sky is presented from any location on the Earth (the user enters his/her precise location co-ordinates in the location settings). The time and date can also be set and it will track the sky (day or night) in real-time. Zooming in on the night sky reveals an increasing amount of detail, including entire nebulae and galaxies pictured as they are. Plugins are also integrated in Stellarium, and extra are downloadable. Some of the plugins available (that come pre-installed) include one for measuring angular distances between marked points on the night sky and an ocular plugin that allows you to gauge your field of view with any telescope and eyepiece or camera combination you add (see screenshot on the right as an example of the field of view with a telescope and CCD camera). 

In terms of goto control, simply selecting (manually or through a search) any star or object and pressing CTRL 1, sends the mount to the target. Stellarium can also be used for goto alignment, by sending the mount to a star, centering it in an eyepiece (a crosshair eyepiece is good for this) using EQMod's slew controls and then pressing CTRL 3 on Stellarium. This sends a synchronise command that centres your star in Stellarium and adds a star alignment point to EQMod (so that future goto is more precise given this error correction). This also demonstrates how easy it is to control one's mount with ASCOM software. Not only will EQMod and Alignmaster assist you in polar alignment (and a precise one at that!), but planetarium software such as Stellarium will afford you access to the contents of the night sky as well as providing full control of features such as star alignments (rather than the Hand Controller forcing you through an ordeal of a process that can be clumsy, at best). 

Stellarium is free software and is actually compatible with Windows, Mac OS and Linux. If you are interested in downloading Stellarium, for either mount control or even just to enjoy looking at the night sky, click this external link to the official website (see bar at the top for download links). Please note that for mount control, you will also require Stellarium Scope, a third-party program that is used to configure and run Stellarium (users have to run Stellarium Scope and in it, connect to the mount and then launch Stellarium via the button provided). Stellarium Scope is also free software and can be downloaded from this external link to its official website. Please note as well that the latest version of Stellarium Scope may not support the latest version of Stellarium! Read the release notes of Stellarium Scope to find out which versions of Stellarium are supported and on finding out, if you require an older version of Stellarium, use this link to the older versions downloads page of the official website

The above screenshot shows Cartes du Ciel, very popular planetarium software that is often used for mount control. An advantage of Cartes du Ciel is that it comes with integrated ASCOM support in order to control mounts, rather than needing an external program to handle it. The same controls apply in terms of slewing and synchronising as in Stellarium. Cartes du Ciel also offers pretty much the same features as Stellarium, is less processor intensive to run on your laptop and is also free software. Choice of which one to use is entirely up to the user, as a result. Though the interface can be thought of as more convoluted and perhaps less pretty to look at, the functionality is all there and nothing is lacking. To download Cartes du Ciel, please follow this external link to the official website

6.6 Autoguiding: PHD Guiding

As discussed in a previous section, it does not normally suffice to have an equatorial mount tracking the night sky when it comes to long exposures in deep space astrophotography. A form of guiding is required, whereby the astrophotographer monitors movement of a star near the imaging target and any such movements are then corrected in real-time via very fine slewing. Doing this manually would be an ordeal worthy of one's eyesight and patience. Nowadays however, given the advent of computer control, autoguiding has taken over manual guiding. Autoguiding involves a smaller CCD camera looking through a second, guiding telescope or an Off-Axis Guider (for details, please see previous section) in order to monitor movement of a star near the imaging target. Any movements detected are then corrected in real-time with correction commands sent directly to the mount. This frees the astrophotographer from his/her input in guiding and allows for more precise, more real-time guiding to take place. There are numerous programs available that handle this monitoring of star movement and sending of correction commands - PHD Guiding is one of them and a particularly good one at that. 

PHD stands for Push Here Dummy. It is meant to be extremely simple to get working and get excellent results from it, and indeed, after some minor configuring, it can really deliver. In the main, once configured (or if you are lucky enough to get excellent performance straight out), it is as simple to operate as connecting to your autoguiding CCD camera (via its ASCOM drivers list), looping short exposures (typically 1.5 to 2.5 seconds long), clicking to select a nice star near your imaging target and clicking the PHD button to start calibration followed by autoguiding. Looping exposure time is altered according to required star brightness, the sensitivity of the autoguiding CCD camera (and the focal ratio of the optical system it is looking through) and the night sky seeing conditions. 

As seen in the above screenshot, a graph can be enabled to verify the autoguiding in real-time, checking how corrections are being made and what kind of star movement is being detected. This graph also allows the user to check and fine-tune performance by altering the settings in the PHD Guiding configuration. A detailed account of these settings and what they represent (as well as how the graph links to them) is described in the autoguiding tutorial in the tutorials page (scroll to the bottom). Generally speaking, PHD Guiding will handle the autoguiding CCD camera control in terms of locking on to a star, monitoring it and sending relevant correction commands to the mount in order to counter any offset in the mount's natural night sky tracking. This allows for theoretically unlimited exposure length (subject to target object visibility, of course), depending on the quality and setup of the autoguiding system in use (see previous section for details). Autoguiding correction commands can be sent to the mount via either the mount's direct ST-4 Autoguiding Port (some mounts have these ports and the autoguiding CCD camera can plug into it directly) or via ASCOM PulseGuiding (sent through the normal ASCOM EQDirect USB cable that is used to connect to the mount to begin with). Either way, PHD Guiding requires you use a laptop in the field to communicate with the autoguiding CCD camera for image capture, monitoring, calculation and transmission of correction commands. 

Given PHD Guiding's international reputation, extreme simplicity and effectiveness, it is surprising that it is actually free software. It can be downloaded for either Windows or Mac OS from this link to the official website

6.7 Mosaic Construction: EQMosaic

It is fairly commonplace for astrophotography to take astrophotographers into encountering field of view problems in terms of imaging the targets they want to image. Wide-field astrophotography is a popular area of astrophotography that tends to involve small telescopes (or simply camera lenses) attached to the cameras. This tends to provide large fields of view that even then tend to not suffice. This is where mosaics comes in. Mosaics in astrophotography are exactly the same as in normal photography - the stitching together of numerous segments to compose a larger image encompassing a larger area. Astrophotograhy is not like normal photography in that the objects being imaged tend to be faint and a lot of the times, much of the image is not filled with high-contrast data. Stitching up of mosaics is something that is left to complex algorithms in post-processing software. However, gathering the images that will later comprise a mosaic need to naturally have some overlap between segments. This is not easy to do visually as your target is not visible to the naked eye and slewing manually can be severely imprecise. 

EQMosaic is a separate program to EQMod and can be used with other ASCOM mount control software but ultimately, EQMosaic requires the mount to be controlled via ASCOM on a laptop. EQMosaic's job is to slew to adjacent mosaic segments. The segments must be defined by the field of view of the optical system being used for imaging. This is easily calculated within the program by entering details such as the telescope focal length and the camera's CCD sensor details. A percentage overlap between mosaic segments is then defined by the user and EQMosaic is ready to do its job. 

By defining the present position of the mount as the starting point, adjacent mosaic segments can be defined and slewed to by clicking the adjacent segments in EQMosaic. Since EQMosaic knows your optical system's field of view and you have defined the percentage overlap, it knows precisely by how much to slew in order to construct a mosaic. Additionally, by performing an alignment to the same initial place using AstroTortilla, an astrophotographer can capture the data to construct a mosaic spanning several nights, with precise alignment and mosaic segment construction. The tutorials page contains a tutorial that goes over the details of using EQMosaic for mosaic construction. 

EQMosaic, like EQMod, is free software and can be downloaded from this link to the official EQMosaic downloads page

6.8 Image Capture: Nebulosity, MaxIm DL, AstroArt and Backyard EOS

Astrophotography with a DSLR can generally be done with from the DSLR itself, with use of a remote release cable (to prevent vibrations translating into your images and to automate the process a little). Computer control of your imaging camera however does have its benefits, including the automated use of it for tools such as AstroTortilla (see above). Dedicated astrophotography CCD cameras are always computer-controlled as they have little in the way of on-board electronics. These cameras therefore require you run software on your laptop to not only capture your images, but to set the imaging sequences and moreover, to control the CCD sensor temperature. CCD cameras tend to come with software designed by the camera manufacturer and though these are generally good (e.g. Artemis Capture by ATIK), there are others in the market that are third-party and can perform more tasks. 

Nebulosity is a very popular program for CCD camera control because it is so universal and has many nice features packed in a simple interface. It is designed by the same person who designed PHD Guiding (see above) and thus works very well alongside it (e.g. for dithering). In Nebulosity, you are greeted with a large list of ASCOM drivers for cameras allowing you to connect to practically any camera. It also features full temperature control by set-point, binning, filter wheel control, etc (for cameras that support relevant features). Generally speaking, it is a very able and very simple-to-use astrophotography capture program. More professional use of Nebulosity can be made with creation of scripts using its simple-to-create interface. These scripts can automate your image capture entirely, including control of multiple elements such as the camera, the filter wheel, PHD Guiding, etc. Please note that Nebulosity supports DSLRs as well as CCD cameras. Along with the capture features, Nebulosity is also advertised to be able to carry out your post-processing. Though not as capable as the likes of PixInsight, it is a welcome feature for those seeking quick results from their images. Nebulosity is not free but it is fairly cheap at $80. If you already have software such as Artemis Capture from ATIK, it may or may not be desirable to move on to Nebulosity. If unsure, there is a 30-day trial available as well. To download Nebulosity, see this link to the official downloads page. Purchase of a Nebulosity license can be done from the official website as well. 

MaxIm DL is a long-established program for all sorts of astrophotography-related tasks. It is designed for both purposes, image capture and image post-processing, though again not anywhere near as capable as the likes of PixInsight for post-processing. In terms of image capture, MaxIm DL does everything Nebulosity does and includes auto-guiding as well (removing the need to use a second program such as PHD Guiding). It is perhaps the most fully-featured image capture program out there, alongside AstroArt. The interface however is quite packed and may seem intimidating to start off. Do not mistake lack of simplicity with lack of power though - it is a very well-featured program. MaxIm DL even features plugin support, allowing the user to expand its capabilities through third-party plugins. One has to question however whether or not these features are necessary for one's own personal use, considering the price. MaxIm DL is not free and comes in numerous editions, with a comparison of features made here in the official page. Prices do however range between $199 and $599 depending on edition chosen. A 30-day trial of MaxIm DL is downloadable from this link to the official page. Purchase of a MaxIm DL license can be made from the official website as well. 

AstroArt requires a special mention because it is perhaps MaxIm DL's greatest competitor in terms of features and competes extremely well given its price point. AstroArt features pretty much what MaxIm DL features, including support for third-party plugins, complete camera control and image post-processing (though again not as capable as the likes of PixInsight for this). AstroArt costs €129 without VAT, which is a significantly lower price than MaxIm DL for what is essentially equivalent software. A 30-day trial version is also available. AstroArt can be downloaded from this link to the official downloads page. A license can be purchased from either the official website or a listed dealer, in boxed or digital form. 

For users of a Canon EOS DSLR, there is a fantastic program out there for you - Backyard EOS. This program is fully-featured in image capture and helps with focusing, sequencing your image capture and even recording the magnified Live View feed to produce an uncompressed AVI video for lunar or planetary imaging. Backyard EOS supports all Canon EOS DSLRs as from those featuring a DIGIC II processor. It has a very simple-to-use interface with everything you need to automate control of your DSLR from a computer, specifically designed for astrophotography. Images captured can be set to download to the DSLR's memory card and the computer, or the computer alone. Backyard EOS is not free but it is very much worth-while having if you have a Canon EOS DSLR, as it costs $35 to $50, depending on the edition chosen. A 30-day trial is also available. Backyard EOS can be downloaded from this link to the official downloads page, and a license can be purchased from the official website as well. 

6.9 Image Calibration: DeepSkyStacker

Astrophotography is a very precise hobby with a lot to consider, particularly for deep space. Since the targets are faint, long exposures are required to capture them in detail. With their constant motion across the night sky, this makes long exposures something of a science. With sensor thermal noise and other causes of noise introduced into images, faint targets (or areas of very faint detail), even in long exposures, can be hard to discern from the background noise. This is where we bring the question of Signal-to-Noise Ratio (SNR) into play. Since thermal noise is random, each and every image contains specks of noise in different locations. Therefore, if you capture multiple images of the very same target, you will notice the noise pattern is different from one image to the next, relative to your target object. This is where stacking comes in. If you were to add all your images together and then divide by the number added, it effectively averages out the images. The result is that your target will appear clearer and the image cleaner of noise (since the noise was not added together, due to its random location). This improves SNR and is therefore the de facto technique used in deep space astrophotography. There are programs out there that can be used to perform this stacking process, and DeepSkyStacker is a very well-established one. 

Where DeepSkyStacker does its job well is in bringing everything together under a very simple-to-use interface with a single job. The process carried out by DeepSkyStacker is called image calibration, as it takes multiple images of a target and stacks them to produce a clearer and cleaner result. In image calibration, there are other elements that come into it as well. These are known as dark, bias and flat images. Dark images are produced by setting off exposures of the same length and camera settings (ISO, temperature, etc) as your target exposures, but with the lens cap (or equivalent) placed. The result is an image that is only comprised of noise and hot pixels. Bias images are produced by doing the same but with the shortest exposure length allowed by the camera. This in effect is to reproduce only the noise generated by reading the sensor to produce the image. Flat images are produced by generally using the same camera settings but aiming at a uniformly illuminated surface (e.g. a wall, a sheet of card/paper, the early dawn / late dusk sky, etc) with the exact same configuration as used when imaging your target. What these flat images reproduce is the vignetting pattern of the optical system, with dust donuts and all. 

DeepSkyStacker takes all these calibration images and the multiple images of your target to produce one final resulting image that has had its SNR improved, hot pixels removed, sensor signal noise removed, dust donuts removed and vignetting cleaned. It is the first process to be carried out in astrophotography post-processing, before taking the image into the likes of Photoshop or PixInsight for further post-processing to bring out the detail, enhance contrast, etc. DeepSkyStacker is not exclusive in performing this task, but it is extremely user-friendly and does the job very well, even if your target images don't align one on top of the other initially (it aligns them together and then stacks them). A tutorial instructing in the use of DeepSkyStacker is available from the tutorials page. Best of all, DeepSkyStacker is free software and can be downloaded from this link to the official downloads page

6.10 Image Post-Processing: Photoshop, PixInsight and RegiStax

Post-processing is an integral part of astrophotography. Purists among photographers may feel otherwise but astrophotography without post-processing is not possible if one is to achieve professional results. Since deep space targets are generally faint, there is generally very little contrast in the images and this is shown by the very narrow histogram in raw images (after calibration). Post-processing involves stretching the histogram to massively enhance contrast and moreover, to clean up noise, bring out fine detail, produce HDR images, etc. Even with bright targets such as the Moon or the planets, post-processing is necessary to overcome seeing to some extent. Seeing blurs the image detail due to the atmospheric distortions and therefore a long uncompressed AVI video of the lunar surface or a planet can be post-processed to stack frames of coincidental good seeing and sharpen the result. The best astrophotographs out there all receive post-processing, even if it is fairly light work. Post-processing programs come in many familiar forms to photographers (e.g. Photoshop) and more professionally-oriented forms (e.g. PixInsight and RegiStax). 

Photoshop is an extremely popular program that is commonly used by photographers, graphic designers, website designers, etc. It is a well-established and very robust program for image processing. It is therefore natural for an astrophotographer to start using Photoshop for post-processing his/her images. Indeed there is not a lot Photoshop cannot do with photographs, but astrophotography is an extremely specialist form of photography and a very challenging form when it comes to software manipulating the images. Signal-to-Noise Ratio (SNR) can at times be an issue, with contrast being poor to start with, and noise possibly dominating a lot of faint areas of the images (which could indeed be much of the image if your target is small). Photoshop is well suited to doing the job but plugins may be required for it to perform adequately. Due to its popularity however, there is extensive documentation available online in the way of astrophotography post-processing tutorials based on Photoshop, both in text and video form. It provides a very good platform to learn but has its limitations. Moreover, the price can be prohibitive, especially compared to the more capable PixInsight (which costs less and is designed specifically for astrophotography). Photoshop can be downloaded from this link to the official website, where a license can also be purchased if desired. A trial version is also available. 

PixInsight has not been around for as long as Photoshop but is fast becoming the de facto standard in astrophotography post-processing software. Most professionals out there use PixInsight and there are even conferences hosted world-wide based on post-processing astrophotographs in PixInsight. Designed from the ground-up purely for astrophotography, it is an extremely capable program that is purely mathematical in the nature of its post-processing. Dozens upon dozens of complex algorithms take play in its large number of tools that perform incredibly well against all odds. Where PixInsight fails is when the user gets over-encouraged to post-process so much, it gives images a bit of a fake look but this is entirely user discretion. People first tend to feel PixInsight has an intimidating user interface, but in fact it is extremely watered-down in its initial screen. It is when you delve into the various tools that you realise how much one has to learn to post-process images, but this is not exclusive to PixInsight, but it is clearer to see in PixInsight because there is so much it can do. By far, it outweighs Photoshop and other post-processing programs out there in terms of capability and price to performance ratio. A 45-day trial is available upon request and PixInsight costs €220 with Spain's 21% VAT, or €182 without VAT, for a commercial license. Updates are frequent and notable. See this link if you wish to request a 45-day trial license or this link if you wish to purchase a commercial license. Please note we have an extensive set of PixInsight post-processing tutorials on our tutorials page

RegiStax is an absolutely incredible program when it comes to post-processing videos of the lunar surface or planets (generally uncompressed AVI videos). As detailed in a previous section, lunar and planetary astrophotography are hindered by atmospheric seeing on the Earth, due to the distortions introduced by air turbulence. This is the reason why quick snapshots of the Moon or planets are not sufficient to capture fine detail. In order to somewhat overcome this, an uncompressed AVI video of several minutes can be recorded at the highest frames per second possible by the camera. Each frame is effectively a snapshot and so the video contains numerous thousand snapshots. RegiStax is able to process this video to find the best frames, stack them together and provide an incredibly sharp result in only minutes of work. It is by far the most suitable program to post-process lunar and planetary astrophotography. Best of all, RegiStax is free software and can be downloaded from this link to the official downloads page