Imaging Software

Arguably, it is software that has progressed most significantly. Towards the end of 2014, an increasing number of users discovered the elegant power of Sequence Generator Pro and the revamped guiding software PHD2. For me, these displaced Maxim DL5 as my acquisition software of choice and its ease and reliability enabled me to meet my publishing deadlines. In a poll of PixInsight users, SGP featured strongly as the imaging software of choice. Its functionality has continued to evolve and yet it maintains simple ergonomics and reliability. Increasingly, these acquisition applications are integrating free plate-solving software (Elbrus, PlateSolve2, Ast­rom­etr­y.n­et) to improve pointing accuracy and assist with meridian flips. Increasingly, at their respective levels of sophistication, these apps are great value and all that one needs, unless there is a compelling need to use a separate application to automate data acquisition or control complex observatory systems. Even here, armed with a little knowledge, custom designs are within reach of those with some technical skills. This is not the only application to improve; the authors of APT and Nebulosity have also been busy updating their data acquisition programs with added functionality and broader compatibility. At the same time Software Bisque has continued to develop TheSkyX and crucially, for some, slowly expanded the hardware compatibility for the Mac OS X platform. Maxim DL also released a version 6 with task multi-threading, to improve device responsiveness. Its extensive application interface often makes it the choice of professionals using automation programs such as ACP. As hardware prices tumble, increasing numbers of astrophotographers are using multiple systems to make the most of the weather and, on the horizon, is the prospect of acquisition programs being able to coordinate multiple imaging devices. BackyardEOS has also gone through several iterations and offer a fuller feature set, including a version called BackyardNikon.

PHD and FocusMax were two popular freeware programs. Time moves on and PHD2 is now an open-source program that has developed into a sophisticated fully-featured guiding program by expanding on its core strengths but without losing its “Push Here Dummy” simplicity. PHD2 development coincided with SGP’s and collaboration resulted in the two programs interacting seamlessly. FocusMax has been updated too, with a less cluttered interface and wider compatibility. It is now a commercial application though, available from CCD-Ware, and is more expensive than Sequence Generator Pro (that has its own improved focus algorithms). Not all software-assisted focusing works by minimizing the star diameter (FWHM or HFD value); software-assisted Bahtinov “grabbers” can now evaluate camera images and determine the optimum focus position. Some, like those from GoldAstro, have re-engineered the diffraction mask principle and optimized it for computer image analysis. In good seeing conditions, its enhanced design can discriminate within the depth of focus, as well as provide useful collimation information at the same time.

These data acquisition programs often benefit from plate-solving programs and the choice continues to expand. At the time of writing PinPoint was the paid application with Elbrus, AstroTortilla and Astrometry. net being the popular free apps (TheSkyX professional has a built-in one). Since then, locally served PC-based versions of Ast­rom­etr­y.n­et allow all-sky plate-solves without the need for an Internet connection and Plate-Solve2, generously provided by PlaneWave Instruments^® is another free alternative. PinPoint has evolved too, increasing its compatibility with different catalogs (USNO A2.0, UCAC 2,3,4) and using Ast­rom­etr­y.n­et to kick-start its own plate-solving algorithms that rely on an approximate starting position.

Most astronomy software at the time of writing is 32-bit, though the majority of operating systems they are currently running on are 64-bit. A transition is required at some point as applications need to access more memory, for instance to support scientific pursuits such as exoplanet hunting, which requires comparing multiple images. For older applications, that have evolved over several platforms, making the change is a big deal; others, with well-written C# code (pronounced C-sharp) may accomplish this with comparative ease.

Environmental Software

All these advances are somewhat irrelevant if the weather is poor, or the user misses an opportunity to make the most of a clear night. Weather forecasting has become ever more sophisticated and available. The Internet has dozens of specialized weather applications and websites, offering useful information for astronomers, including light levels, seeing conditions, humidity, cloud (of course), moon and satellite timing. Some specialize in short-term forecasting, up to 15-minutes ahead, that can offer warnings of approaching showers or squalls. It is now possible to get a weather feed directly into the imaging software from www­.op­enw­eat­her­map­.or­g through an ASCOM driver.

An Internet connection is not always available and on the hardware side, weather sensing has also become an integral part of the astrophotographer’s arsenal. High quality solid-state pressure, temperature and humidity measurements not only provide ancillary information for image headers but the data itself can be used dynamically by advanced mount systems to update the refraction parameters of its pointing or tracking model. Infrared, capacitive and ultrasonic sensors are now common place to measure sky temperature (and hence cloud cover), rain and wind speed respectively for safety systems. These monitor sky conditions and allow data acquisition programs to execute start-up or shut-down sequences to park equipment, warm up cameras and close roof systems. To enable this to happen effectively, collaboration between the ASCOM community and hardware providers recently agreed on standards to not only define common environmental parameters and protocols but also allow for future expansion as control systems become even more advanced. Environmental data is essential information for building a pointing and tracking model that accommodates changes in atmospheric conditions. Lastly, PC clocks are not particularly accurate and can drift by several seconds over a week. In order for a mount to point accurately, without closed-loop syncing, requires an accurate clock. On boot-up, an automatic internal clock adjustment, using any one of the web-served Network Time Protocol (NTP) servers, sets things up within fractions of a second.

Processing Software

The processing programs also continue to evolve. In 2015, the PixInsight program proposed a revised form of FITS file that promoted an extended capability (XISF). It is a bold move, the FITS file format has been around for 35 years! Individual tools in PixInsight continue to be refined, or dropped in favor of new tools, and just as importantly, enterprising users have found ways of combining these tools using scripts to implement advanced features, some of which will be familiar to Photoshop users. Adobe continue to develop Photoshop, slowly increasing the amount of 32-bit support. It suffices for many, but I prefer the optimized astrophotography tools offered by the dedicated programs. In the last year Serif, an established software company, has launched Affinity, an image processing application for digital photographers. It is keenly priced and available for both Mac, PC and iOS platforms. It is quickly picking up many admirers and for the astrophotographer, offers high-bit and stacking options. It is well worth investigating.

Mounts

Mount design has moved on too. At the top end, optical encoders are increasingly being used for high precision pointing and tracking or effectively removing periodic error. This technology is migrating downwards to give lower-end mounts a sense of direction at power up, improve pointing accuracy and to give the larger Dobsonian telescopes the ability to locate objects more easily. It used to be the case that a small mount was a “lightweight” performer too. With the growing number of amateur users, a number of manufacturers have produced more portable mounts that inherit the qualities of their larger siblings, Paramount, SkyWatcher and iOptron amongst others.

An increasing number of super-compact new models cater for camera users, typically with RA-only motors and with ST4 guider interfaces, ideal for wide-field imaging and travelling. Typically they assume the user will use a stout photographic tripod and tripod head. Even though some have polar scopes, drift arising from the typical alignment errors set an upper limit for the exposure time. In these cases, long exposures are only practical with wide angle lenses and proportionally less for longer focal lengths. With environmental imaging in mind, some units, like the SkyWatcher Star Adventurer offer partial tracking rates which provide a nice compromise for wide-field landscapes; by equally blurring the sky and landscape.

Some “out of the box” thinking has been applied by iOptron and Avalon to the geometry of the traditional German Equatorial configuration, which allow for compact systems and remove the traditional equatorial mount constraint of imaging through the meridian. With aircraft luggage restrictions and premiums, the AstroTrac^® system is another re-think that produces a very compact travel unit for wide-field imaging.

With wide-field imaging, periodic error is of lesser concern than overall drift. The QHY PoleMaster has turned polar alignment on its head and is an enabler for portable systems to polar align in minutes to an accuracy of a pier mounted system and without using plate solving. Its simplicity masks an ingenious and robust alignment procedure and it relies upon tracing a star’s rotation about either celestial pole to determine the true center, determines the hour angle and then provides a magnified view to center the alignment star using the mechanical adjusters on the mount.

Imaging Hardware

Not surprisingly, advances on the optical side are no less significant but less radical. There are an increasing number of affordable 5-element astrographs with modest apertures, Ritchey Chrétien prices continue to fall and more companies are concentrating on modified Dall-Kirkham reflectors, to improve on the usable field of a dual mirror configuration. As customers become more discerning, companies have responded to the criticism of poorly designed and assembled focusers and switched to precision rack and pinion designs to avoid slippage. (Focus control systems have proliferated too as folks work out that most stepper motors conform to a standard arrangement of four motor coils.) Takahashi are still the dominant player for quality wide-field, large aperture instruments but more affordable alternatives are closing the performance gap.

On the camera side, things become interesting. Many dedicated astrophotography cameras take advantage of CCD sensors, made for consumer cameras that had their brief moment of fame in the last decade. I cannot think of a current digital SLR or mirror-less camera model that uses a CCD. A new form of imaging, using thousands of short exposures from a high speed CMOS camera is finding favor with some, since it can be used to side-step guiding issues and seeing noise. CCDs are, however, still being developed, especially in the smaller sizes and almost entirely by Sony. These sensors have extremely low read noise and pack 9 or 12 MP into a sub APS-C chip. Full-frame SLRs using CMOS devices continue to drop in price and many opt for these for creating panoramas of the Milky Way. Up until recently, Canon was the only DSLR company to introduce astronomy-orientated products in the form of the APS-C chipped EOS 20Da and more recently the EOS 60Da. In the last year Nikon has entered the fray with its full-frame Nkon D810A camera. Though few telescopes support the field of view, full-frame digital SLRs continue to lower in price. The larger sensors have a high pixel count yet retain sensible pixel spacing. Although most digital cameras can be pressed into service, it really helps if the imaging applications support their operation over USB. At the same time small video cameras, suitable for solar planetary imaging are becoming increasingly available but the high data rate and USB3/Firewire interfaces pose a challenge for some computer hardware as well as the fact that some video capture devices do not readily comply with common media protocols.

Hardware (Other)

Moore’s law (from 1965!) is still resonant today. Current computing trends continue to shrink PCs. Of particular note to astronomers are the range of miniature PCs, designed for media use, that pack a full solid-state Core-I5 or I7 system in a small box just 4” square. At the same time, used with some care, they consume just 8 W of 12-volt power and are ideal for extended battery operation. Even smaller, PC sticks are capable of running Windows for data acquisition and control. The more enterprising engineers amongst us have also discovered the benefits of low-cost robotic computing units in the form of Raspberry Pi and Arduino units. These are being used in a number of configurations to control observatories and make remote operation a joy, a practical example of which is shared in a later chapter.

INDI

The Instrument Neutral Distributed Interface (INDI) provides a framework for the control of various devices relating to astronomy and astrophotography. It has been around for a while but only recently has started to gain momentum, notably by the PixInsight development team.

In very simple terms it tries to accomplish the same as ASCOM does for Windows, and more, since this open source library is based on XML and is uniquely cross-platform. Its library currently supports Linux, BSD and OS X. (Windows support is in progress.) Like ASCOM, it is heavily reliant on contributions by 3rd parties rather than being developed by a commercial entity. Unlike ASCOM, it is not universally supported by hardware manufacturers and at the moment the list of supported devices is modest, but increasing.

INDI is very compact too, with some users running full imaging systems from a Raspberry Pi credit-card sized computer. These units were designed to promote computer science in schools and developing countries, with a modest 1GHz clock rate and up to 1GB RAM. They run Linux and support programming in several languages. If one keeps things simple and the programming overheads low, it is amazing what one can accomplish with low power devices. Those astrophotographers with a science or computing background and with time on their hands may find product development a fascinating avenue in which to expand their hobby interests and to meet specific needs. Others may relish the possibilities for distributed systems and automation outside of the classic Windows environment. A glance at the website www­.in­dil­ib.­org­ is filled with jargon and obscure (to some) references and confirms that this is not yet a system for those who want to plug and play. I am confident that will change in time.

ASCOM Web

The motivation behind INDI is also stirring in the AS-COM community to address its outdated dependence on one operating system. It is hard to miss ASCOM in astrophotography, even if one is using a Mac and one of the few applications that has drivers for your hardware. ASCOM’s set of interface definitions have been around for many years but is limited to Microsoft Windows platforms. Today ASCOM clients and drivers communicate through a protocol called COM (and increasingly .NET). This allows the client application and drivers to be written in different languages, providing a considerable degree of flexibility. The drivers can run within the application process or outside in a server process (in process and out of process) but in both cases, the application and driver are constrained to run on the same PC. Remote operation is possible, as with all windows programs, using Microsoft Remote Desktop, TeamViewer or similar. In these applications, it is only the human interface that is remote and the application and driver are still on the PC and the applications run on the Windows platform.

The solution (yes, you guessed it) is the Internet. In this case the Internet (or local area network) is used to communicate between client applications running on any number of platforms and a PC server process that runs the COM driver and connects to the hardware. To do this securely, it is proposed that the communications between the applications and the driver use standard secure http protocols with JSON data encoding. This requires a little work at either end to encode and decode the data passed between the driver and the application, as well as other Internet software to ensure security and access control.

With a little ingenuity, this latest venture allows an application on virtually any portable or alterative platform to control astronomy devices via a PC hardware interface. By moving the resource-intensive applications to a remote device it additionally allows one to use local PC bricks or sticks at the observatory site, solely running the hardware interfaces via an Internet connection.