Base System

I dedicate a computer for imaging and set it up to run lean and mean. I disable fancy power-sapping themes and animations but it does make some of the screen grabs look old-fashioned. A fresh install of Windows, without the bells and whistles, makes the most of battery power. After the software installation is complete, I create a power saving profile in advanced power management, which ensures the computer is never allowed to go to standby (including the USB system) and the screen, cooling strategy and maximum processor usage is scaled back as far as possible. I implement this for both battery and mains operation, since in my case, when I connect the external battery pack, the computer acts as though it were charging. For a 2.5 GHz Core I5 processor, I can run at 50% max processor usage during image capture. With care and a SSD hard drive upgrade, my laptop (a MacBook Pro) runs Windows 7/10 for about 2 hours longer than normal. By dedicating a machine for the purpose, I do not use it for e-mail or browsing. It connects through a hardware firewall and I disable Windows firewall and power robbing drive scanning. My software, utilities and drivers are downloaded via another machine and stored on a remote drive. These archives are kept up to date with the last two versions of any particular driver or application, just in case the latest version introduces bugs. I install these programs directly from an external drive or memory stick. For backup, I copy all imaging data to a dedicated external drive. When everything is working smoothly, I create a complete backup (for Mac OSX I use a utility called Winclone to back up the Windows partition).

Application and Drivers

There are no hard and fast rules but there is definitely a preferred installation sequence that minimizes issues. This follows up the data highway, from the hardware to the highest-level application. When I updated my system from 32-bit to 64-bit Windows 7 and on to Windows 10, the following sequence installed without a hitch, though it took several hours to complete, most of which were consumed by innumerable Windows updates. The recommended sequence is as follows and concludes with a system backup:

1 hardware drivers (PC system, cameras, filter wheels, focusers, USB-serial converters)

2 ASCOM platform (from ascom-standards.org)

3 ASCOM device drivers (from ascom-standards.org or the manufacturer)

4 image capture applications

5 utilities (focusing, plate solving, polar alignment)

6 planetarium

7 planning and automation applications

8 image processing applications

9 utilities (polar alignment, collimation, etc.)

In general, once you expand the zip file, run the installer and follow the instructions. There are a couple of things to note: Some applications and occasionally the installation programs themselves require to be run as an administrator or using an administrator account. I select this as the default for ASCOM, Maxim, Sequence Generator Pro, Starry Night Pro, FocusMax and MaxPoint. Some programs also require additional software to run, including the Windows .Net 4.0 & 3.5 frameworks and Visual Basic. The installation programs normally link to these downloads automatically. Other utility programs, such as Adobe Acrobat Reader and Apple QuickTime, are free downloads from the Internet. Some ASCOM savvy programs, such as Starry Night Pro require a modification to the ASCOM profile settings before they will install. This may change with time and you should check the ASCOM website or user groups for the latest recommendation.

At the time of writing, most astronomy programs are still 32-bit and do not require a 64-bit operating system (though they will run in one). There are a few 64-bit applications, PixInsight for example, and these will not run in a 32-bit version of Windows. This will increasingly be the case over the coming years and several mainstream applications will need to move over. Windows 7 has some tools to run Windows XP compatible software but I found a few programs, such as PERecorder, stubbornly refuse to run in a 64-bit environment. If you do upgrade operating systems, many astronomy programs store configuration and setting files that can be copied over to the new installation. You may need to check their contents with a text file editor and change any paths from “/Program Files/” to “/Program Files (x86)”. A number of programs have a finite number of activations and you must deactivate or de-register them before formatting the drive upon which they run. The most notable example is Adobe Photoshop. If, like me, you run Windows on a Mac and run the otherwise excellent Parallels, the Windows operating system repeatedly believes you are running on new hardware and demands a new activation. I gave up after the 5th activation. I resisted the change to Windows 8, but succumbed to Windows 10 as it offers a multiple screen remote-desktop facility.

There are a couple of things to watch with installing catalogs. The venerable General Star Catalog (GSC) is used by PinPoint for plate solving and also by planetariums for displaying stars. These often require the same astrometry data but in different compression formats. I normally put one version in a specific folder in My Documents and another, for plate solving, in the plate-solve program folder. Some planetariums have an associated catalog compiler that converts the otherwise disparate formats into a single version dedicated for purpose. C2A and others have extensive catalog management support and compilers for their planetarium, as does TheSkyX.

In Mac OSX, there is no such equivalent to ASCOM and all programs are required to support hardware directly. Thankfully, there is a degree of collaboration between companies and several different programs work with each other to support the bulk of popular equipment. Nebulosity, Starry Night Pro, TheSkyX and PHD2 are available on both platforms and offer some choice for a basic working system. Using Macs is not a crusade for me and I can live with PCs since Windows 7.

Communications

Communications can take several forms, including serial, USB and Ethernet. Sometimes those forms are a hybrid – for instance the SkyFi unit converts WiFi into a serial hardware interface and the computer issues serial commands through a WiFi link (fig.1). In Windows, this is done through a virtual COM port. The program thinks it is sending serial commands but in fact it is sending commands through USB or WiFi. Some USB to serial adaptors have virtual COM port utilities or you can use a free utility like “HW VSP3” from www.hw-group.com. One issue that arises with setting up the communications is Windows security. If you have enabled a software firewall, it may be necessary to grant safe passage for your programs in the firewall settings.

fig.1 This Orion WiFi control module is also sold as the Southern Stars SkyFi unit. It enables serial (RS232, TTL serial and USB) commands to be sent over a wireless network. A piece of software called a virtual COM port on the PC masquerades as a standard serial port but actually converts the serial data to transmit over Ethernet cables or WiFi. These units also allow a smart phone or tablet to connect to a telescope mount. There are similar units which use Bluetooth but these have less bandwidth and range (and use less power too) and can be used for non-time-critical applications.

Powering Up

With all the hardware connected and assuming the hardware drivers have been installed, the first power-up triggers Windows to register the different devices. (There are always exceptions; my video camera requires the camera to be plugged in for the driver installation.) This should be a once-only event but you may see the “installing new hardware” icon tray pop-up if you swap over USB port connections. Swapping USB ports between sessions can prompt for the hardware driver to be loaded again and can re-assign COM ports. (Consistent, fixed hardware configurations using an interface box prevent this from happening.) After all the hardware is physically connected, the next task is to initialize all the software settings. This is a lengthy task and I recommend listing the common settings and use as a handy reference. I have captured many of the common settings in fig.3. It is a case of patiently going through each of the programs in turn, through every settings dialog box and fill in the relevant information. There will be a few instances where programs will read data from other sources but having a crib sheet is useful. The good news is that most programs allow you to save program configurations: Maxim DL, TheSkyX, Starry Night Pro, Sequence Generator Pro, PHD2 and FocusMax can load and save complete configurations. In the case of my four combinations of focal length and field-flattener, I create one configuration and then duplicate it another three times. I then modify the few values related to field of view, focal length and angular resolution. The few that remain are updated by a subsequent calibration; for instance guider resolution and focus parameters.

fig.2 The inter-connectivity between applications can be quite confusing. In the example above the arrows indicate which is linking to which and a proposed “connection” order. The “A”s are links that connect programs automatically when the need arises. In this system FocusMax and MaxPoint can both work as a hub, but MaxPoint (a sky modelling program) is downstream of FocusMax so that all applications benefit from the sky model. For example, the first step is to connect Maxim DL “mount” to the FocusMax telescope hub. If FocusMax is already setup to call MaxPoint and MaxPoint is already set up to connect to the mount ASCOM driver, the instruction from Maxim DL 5 actually prompts FocusMax, MaxPoint and mount driver programs to load and run automatically. I found there are a number of alternative start-up sequences and after having some connectivity issues, some of which required a PC re-boot, I disabled the automatic connections and manually opened each application and connected to the other devices.

Finally there is the linking of the programs through their ASCOM interfaces (fig.2). This is a confusing subject for many users. It is possible to daisy-chain programs through others to a final piece of hardware. fig.2 shows an example of the ASCOM connectivity between programs and a suggested connection order. Those ASCOM drivers that accept multiple connections, are called hubs. ASCOM developed a multi purpose hub called POTH (plain old telescope handset) to satisfy multiple program connections to a mount. It has expanded since then to encompass other roles too. Many modern telescope drivers, MaxPoint, FocusMax and others also act as a hub for mount control. The configuration is a one-time only setup but one needs to take care; the daisies in the chain sometimes have to be in a certain order. For instance, to reap the benefit of accurate pointing for all connected programs, MaxPoint should connect directly to the mount driver and not be further up the linked chain. This program linking can also trigger multiple programs to start up and run when you connect say, Maxim DL to the mount. Fault tolerance is not astronomy software’s strong suit and I had issues with connection time-outs with Maxim DL 5, Focus-Max, MaxPoint and focusers. These time-outs often required a Windows Task Manager intervention or a full reboot to fix. Although FocusMax has options to automatically connect to focuser, telescope and camera system (in other words, it virtually boots the entire system), I manually connect Maxim to the FocusMax telescope hub and connect FocusMax to the focuser before connecting Maxim’s focus control to FocusMax (fig.2). Optec Inc. released an all-purpose hub called the Optec ASCOMserver which additionally allows two connections to like devices. This hub, unlike some of the original ASCOM platform packaged ones, is transparent to all commands and therefore can serve specialist equipment.

Plate Solving

Plate solving is one of those things I always marvel at. It’s a pretty cool idea but the different programs sometimes need a little assistance to get going. Some, like PinPoint, require an approximate starting point and pixel scale (or seek it from astrometry.net). Others also need the approximate orientation of the image. There are numerous free plate solving applications now that for general pointing purposes are fast and reliable, including all-sky solves, where there is no general positional information with the image. The catalog choice affects performance. The common GSC catalog is great for short and medium focal lengths but you may find it is insufficient for work with very small fields of view associated with longer focal lengths. In this case, you may need to set up an alternative catalog with more stars. Many imaging programs read the telescope position and use this as a suggestion to speed things up and minimize the chances of a false match. In the interests of time, I also limit the match to 50 stars and stars brighter than magnitude 15. I don’t believe matching to more makes it any more accurate for practical purposes and certainly takes longer. Model making may require many plate-solves and the time soon mounts up. For the same reason I use a short 2x2 binned exposure; the image is not only brighter but it downloads in a fraction of a second. Plate solving is particularly powerful when it is automated as part of routine to find and locate an image, at the beginning of an imaging sequence or after a meridian flip, to automatically carry on from where it left off. Sequence Generator Pro usefully has that automation built in (fig.4).

fig.4 With plate solving, the need for extensive sky modelling to achieve good pointing accuracy is removed. With just a basic polar alignment, Sequence Generator Pro will automatically slew to the target area, image, plate-solve and automatically center, image, plate-solve and confirm the positional error to the intended coordinates. It repeats this until the desired accuracy is achieved. In the case of the Paramount mounts they have to be homed after power-up before they will perform a slew command. Once my MX mount is homed, SGP will center the image to within a few pixels within one iteration of its automatic center routine.

Meridian Flips

Imaging through the Meridian can also trip up the unwary: The two main issues are aligning back to the target and guiding after a meridian flip on an equatorial mount (fig.5). Before we get to that, it is important that you have set the mount slew limits so there is no chance of crunching the camera or filter wheel into the tripod. The better mounts will place the object squarely in the frame once more (but reversed) after a meridian flip. Others may be a little off as the result of backlash and flexure. One neat trick is to use plate solving in Maxim (or the automatic center command in Sequence Generator Pro) to re-center the frame:

1 load the original image at the start of the exposure sequence and plate-solve it

2 instruct the mount to slew to that position

3 take a short exposure and plate-solve it

4 sync the mount to the plate-solved position

5 select the original image, plate-solve it and tell the mount to slew to the plate-solve center

fig.5 When a German Equatorial Mount flips, the autoguider program or the mount has to account for the image flip on the guide camera. If left uncorrected, the RA errors would increase exponentially. In the case of an autoguider program making the adjustment, the telescope driver is required to tell the software on what side of the pier it is sitting. In this example, the ASCOM profile settings show that “Can Side of Pier” is unchecked, which might effectively block meridian flip controls on some mounts.

fig.6 My current Windows setup is more streamlined and reliable. AstroPlanner feeds target data into Sequence Generator Pro (SGP). SGP automates targeting, focusing and sequenced acquisition with simple to use and powerful features, including fully automatic meridian flips. The automation is sufficient for all-night hands-free operation that, with Maxim DL, required an external control program or scripting to facilitate. PHD2, the latest version of this free guiding program, interacts with the mount and SGP to handle guiding, dither and takes care of DEC compensation and guider orientation after a meridian flip. PinPoint is one of a number of plate solving programs that can be called from SGP to facilitate centering and accurate mosaic alignment. In this setup TheSkyX is being used as a planetarium and a mount driver for a Paramount MX. (It also has its own guiding, focusing and basic sequence features too included in the camera add-on.)

The image should now be precisely centered as before, only flipped over. The mount’s sense of direction is flipped and so too are the autoguider corrections. The whole arena of meridian flipping is complicated by the fact that some mount drivers accurately report on the mount orientation, some applications work it out for themselves and in some cases, the polarity of the movement controls is reversed automatically by the mount driver. In the case of an EQ6 mount, I just need to select “Auto Pier Flip” in the autoguider settings to reverse RA polarity after a meridian flip. In Maxim, you also have the option to reverse one or both axis without re-calibration. To find out what works, choose an object in the south just about to pass over the meridian, calibrate the guider system and run the autoguider. Once the mount flips over (either automatically or manually), stop the guider, select a new guide star and start guiding again. Check the guider graph – if either the RA or DEC corrections have the wrong polarity, their error trace will rapidly disappear off the graph. Sequence Generator Pro automates this meridian flip sequence and can additionally instruct a rotator to orientate the camera to its prior alignment.

Autoguiding

Some premium setups may not require guiding if the mount has effective periodic error correction (gear tolerance correction) and no drift (as the result of extensive periodic error correction and polar alignment). Some of the latest mounts use a closed loop control system and, in conjunction with a sky model based on multiple star alignments, accurately track using both RA and DEC motors. For the rest of us, we normally require some form of autoguiding system. Even a perfect mount with perfect alignment will exhibit tracking issues as the object’s altitude moves closer to the horizon, due to atmospheric refraction. At 45°, the effect is sufficient to cause a 5 arc second drift over a 10-minute exposure. A sky model is designed to remove this effect.

The software setup for guiding is often complex though some programs, notably PHD2, do their best to keep things simple. It has to accommodate mechanical, optical, dynamic and atmospheric conditions and that is before it tries to work out which way to move! For those with well-behaved mounts, a few button presses is all that is required. When that does not produce the desired result a good deal more analysis is required. Although some mechanical aspects, for example balance and alignment have been already covered, this might not be sufficient and for that reason autoguiding, model building and tracking have their own dedicated chapter later on, that fully explore guiding issues and remedies.

fig.7 The free program FITSLiberator is shown here displaying the header file for a FITS image. It is a mine of information about the image, how and where it was taken and with what equipment and exposure parameters. This useful program has image processing capabilities too and in its last version (3), operates as a stand-alone utility.

Image File Formats

Most of us are familiar with the various camera file formats, the most common of which is JPEG. This is frequently deployed on consumer cameras and is a compressed, lossy 8-bit format, though it is always an option on high-end equipment too. For astronomy, the only time we use JPEG is perhaps to upload the final image to the web or to have it printed. The high-quality option on any camera is now the RAW file, an “unprocessed” file. These are normally 12- or 14-bit depth images stored in a 16-bit file format. TIFF files are less common as a direct camera format but usefully store in 8-, 16-, 32- and 64-bit lossless formats. Dedicated CCD cameras issue a true RAW file. When used with a dedicated image capture program these are commonly stored in a FITS format. The “flex-ible image transport system” is an open format extensively used in the scientific community and works up to 64-bit depth. Just as with the other image file formats, the file contains more than just the image. It has a header that contains useful information about the image. This allows details of an image to be stored for later use. In astronomy, this includes things like place, time, exposure, equipment, sensor temperature and celestial coordinates.

A typical imaging night may capture hundreds of files and the FITS header is often used to automatically sort and order the files into separate objects, equipment and filter selection by the image processing programs. During the software setup, it is a good idea to find the part of your image capture program that defines custom fields in the FITS header and check it is adding all the useful information (fig.7). It can save time during batch processing, as it helps group like-images together.

Video Capture

It is very satisfying to take short duration videos of what appears to be a hazy object and process them into surprisingly clear objects. The humble webcam produces a simple compressed video stream, the more advanced models have the ability to output RAW video data and at a shorter exposures and higher frame rates too (fig.8). A shorter individual exposure is useful to minimize the effect of astronomical seeing and is especially useful on bright objects such as Jupiter. There are a number of video formats (codecs), including BY8 and UYVY. The PC receives these and saves as a compressed or uncompressed AVI video format for later processing. Some video cameras already conform to the Windows standard (DirectShow) but others require drivers to control specific features and settings. The better software can record an uncompressed raw video file, rather than a processed, compressed and DeBayered color image. This is an expanding arena and the ASCOM.org website has some general purpose drivers and resources that might be customized for your camera model. The complexity and variety of various formats and models make coding, however, a challenge.

fig.8 Video sequences by their nature require control over shutter speed, frame rate, gain and gamma, as well as the color codec. At 60 fps, the DMK camera challenges a USB hub’s bandwidth and requires direct connection to a PC. Here, DMK’s own application software, IC Capture AS, is happy to run alongside an imaging program. Since the alignment between frames is carried out in software, there is no need to use autoguiding. It is quite straightforward to point to the planet or moon, acquire a short video and nudge the mount (to create a mosaic) and repeat at intervals to find the movie that has the best seeing conditions. At present, there are no ASCOM drivers for the DMK devices.