Can SGP Run My Equipment?

  • Alex McConahay
Part of the The Patrick Moore Practical Astronomy Series book series (PATRICKMOORE)


Sequence Generator Pro works with most of the equipment you will find in observatories and at star parties frequented by amateur astro imagers. To start with a basic setup you will need a telescope on a GOTO mount, an imaging camera, a guiding system, and of course a computer to coordinate it all. To get even more out of SGP, add a motorized focuser. And to really optimize SGP, consider a flat screen panel, a rotator, a cell phone to wake you up when something goes wrong, and even a full observatory with a weather sensor to close the roof when the clouds come in. One major requirement is that any equipment that does not work with SGP native support should be ASCOM compatible, as nearly all amateur astro equipment is.

Overview of an SGP Imaging Rig

Sequence Generator Pro works with most of the equipment you will find in observatories and at star parties frequented by amateur astro imagers. To start with a basic setup you will need a telescope on a GOTO mount, an imaging camera , a guiding system, and of course a computer to coordinate it all. To get even more out of SGP, add a motorized focuser. And to really optimize SGP, consider a flat screen panel, a rotator, a cell phone to wake you up when something goes wrong, and even a full observatory with a weather sensor to close the roof when the clouds come in. One major requirement is that any equipment that does not work with SGP native support should be ASCOM compatible, as nearly all amateur astro equipment is.

Of course, any book would have a hard time keeping up with the changes in what equipment SGP can use. After all, the SGP website ( itself is very generic and is frequently in need of an update. It says rather sweepingly that “ Sequence Generator Pro is compatible with a wide variety of Astronomy’s most popular brands!” It lists some compatible popular equipment and programs, and then invites anyone with a specific inquiry to contact them by email. For now, just remember that if you want to know if your hardware can be used with SGP, just ask if there is an ASCOM compliant driver for it or it has SGP native support. Or write directly to Main Sequence Software. Their address is on the webpage given above.

This chapter will discuss in some detail what to look for in this equipment. The next chapter will discuss details about how to connect it and get it to work together.

ASCOM and Star Trek’s Universal Translator

Let us take a moment to consider how equipment communicates. The various pieces of equipment are manufactured by dozens of companies from around the world. Each company, whether from the United States, England, China, Japan, Germany, Italy, or another country, speaks a native language. This could be confusing enough. But each manufacturer generally runs the product in that company’s software language, not their competitor’s or some universally agreed upon standard language. We are not talking about Japanese and Chinese and Italian here. The software that runs a Canon camera is not the same as runs a Sony or Nikon. And both differ from SBIG or Starlight Express.

SGP can communicate with some devices in their native language, but for much of this polyglot, if SGP is going to communicate, it needs Star Trek’s universal translator for imaging equipment. Luckily, with a few assumptions, we have just that in the ASCOM system.

Fig. 2.1

The third column of this illustration, from the ASCOM website, describes how ASCOM works. Control programs (A) such as SGP and others communicate with the ASCOM driver layer (B). This is a universal translator. This layer in turn can speak to each device (C). In traditional schemes, monolithic and extensible, manufacturers must write different drivers for each different program.

Let’s assume for a moment that each of the cameras does the same thing. In whatever language the manufacturer uses, every camera must have a command that says something to the effect of “Start an exposure…” And another that says, “Continue the exposure for X seconds….” And another that says, “End the exposure.”

Along comes ASCOM. It is a universal translator that has its own list of commands, as it were. To oversimplify, each manufacturer supplies a translation table that translates the language of the manufacturer into an ASCOM command. Now, SGP can just speak ASCOM, and the computer translates this ASCOM command into something understood by the manufacturer’s device.

However, that simple assumption is not enough. A second assumption is that the equipment itself is different. So, different equipment can do different things, and some can respond to a larger set of ASCOM commands. For instance, with the development of CMOS (versus CCD) technology users can more often select gain when planning their shots. Other differences include that some cameras can be binned, and others cannot. DSLR users can specify ISO settings. SGP must know this and expand the range of commands it can send to these devices.

This is all done through drivers. Manufacturers (or sometimes individuals) provide drivers for each of the devices. Users must download these drivers and use them to configure the device for their computers. It is as if the user must download a translation table for each of the devices he or she is to use with the computer. The driver knows the capabilities of the device, can inform SGP of the capabilities, and has a way to translate the SGP (or other program) commands into the native instructional language of the device.

Although this all sounds very simple it is, in fact, very complex. New devices, especially devices with new capabilities, can present problems. Device and ASCOM drivers may simply not yet be released when the product is. It takes a while for them to come down the pipeline and get through the testing and trials to which any new product is subject. And, if there are new capabilities, the developers at SGP may be required to rewrite part of their interface to deal with the new capabilities.

However, before long, all this happens. A manufacturer cannot long survive if the equipment cannot be managed. So, it becomes imperative to have an ASCOM driver. When it is developed, SGP can run your equipment.


SGP, of course, needs a computer. Luckily, it does not need much of a computer. The demands on the central processor are relatively small. The computer spends much of its time sitting doing nothing while waiting for the camera to absorb photons. Even guiding, which is constantly taking small pictures, analyzing them, and issuing corrections, takes very few processing cycles on a computer. SGP and all its friends do not take a fast processor, or lots of memory.

Fig. 2.2

SGP does not demand much in the way of a computer. Here are the author’s observatory computers. At home, the “Outhouse Observatory” is run from a twelve-year-old Lenovo (A). At GMARS, the rig runs off a refurbished desktop (B). The nice thing about old desktops is the native RS232 and lots of slots (C) for other cards.

Computer Suitability

Any Windows compatible laptop or desktop from the past ten years or so can run it. Although it is generally a good idea to update to newer software releases for compatibility and security reasons, the SGP Forum specifies that program will be supported at least through 2020 on Windows 7, and until 2025 on Windows 10. And, as with all programs, once a program is working on a computer, it tends to stay working. So, even though Microsoft may be updating Windows, and Main Sequence Software is updating SGP, your own copy of SGP on your old computer will continue to run as it always has even if you skip updates. (Well, as long as you use the same equipment and nothing breaks, etc.)

Data Storage

One function of the computer is to store the collected data. A night’s imaging can easily run to perhaps a gigabyte of data. This should not challenge any modern computer with a modest hard drive. However, if you tend to store the data on the acquisition computer, or if you use the machine for other functions, a hard drive can fill up. Those with smaller hard drives should consider removing the data occasionally to a larger storage system by means of a USB thumb drive, flash card, or some other method. Another solution that has worked for some, but not for others, is to save the data files directly to a thumb/flash drive during the imaging session. Then the thumb drive data is transferred to a larger, more powerful processing computer. Give it a try if you have limited hard disk storage. But be prepared to make room on the hard drive if the thumb/flash drive does not work well with SGP on your machine.

Ports and Connections

Another consideration for the computer is how it can connect to the various devices SGP manages. At a minimum, you would have an imaging camera , a guide camera, and a mount interface. Perhaps your system would also have a separate filter wheel. As the system develops, the imager would add focus motor control, temperature sensors, weather sensors and observatory control cables, and various other cables to the computer. The world of imaging hardware is still very traditional, with good-old RS-232 connections found on many devices. Other devices run on USB ports, both 2 and 3. Your computer should have as many native USB ports as possible, and if you can find a computer with RS-232, you can be ahead of the game. But, let’s face it, finding a laptop that can go into the field with four USB ports is rare enough, and RS-232 – virtually impossible nowadays.

RS-232 ports can be connected to USB ports through serial converters. There are many on the market. Some work all the time, others may work only when they feel like it. In general, avoid the bargain brand. By sticking to the Keyspan, with the FTDI chips, the imager can avoid many frustrations.

Another way to make up for lack of ports is to use a multi-port USB adapter. These also come at a variety of price and quality points. Some are powered (with a separate power supply) and some rely on the power from the computer itself. A four outlet splitter can be had for as little as $5. Or one can spend $65 for the same number of ports. If you want to avoid trouble in the long run, in general spend about $30 or more, and make sure any multi-port adapter has its own power supply.

Many imagers have found the greatest success by connecting the imaging camera to a dedicated port, the guide camera to its own dedicated port, and then using a splitter to accommodate the other devices as necessary. But no matter what one does, experience and experiment is often required to get all those cables connected to the machine.

Fig. 2.3

In choosing your computer, also do what is necessary to control light at your imaging site. Any computer screen puts out too much light for an observing field. The screen need not be all that large. Be careful with your computer screen to see it is fully shielded and covered so that excess light will not escape.


For a monitor, consider the situation. The imager will be out on a dark night. Perhaps the imager is alone and does not mind a glaring screen. But, often, the imager is at a star party with lots of dark sky enthusiasts, or even letting SGP run the imaging scope while he or she is snuggled up to a big telescope star hopping across the sky. No time for more light than necessary. A netbook does not have a big enough screen, in general, to see all the details of an SGP session. A 27-inch-wide-screen makes a very impressive display but is totally unnecessary and probably counterproductive. The main advantage is that you can have full-size planetarium programs, the full PHD2 Guiding screen, and the SGP screens and windows all operating at the same time. However, it is not necessary to have these separate programs visible at the same time during an imaging run. The simple 17-inch laptop-sized screen is more than adequate. But, at a dark sky site even its screen should be darkened (dim the brightness control) and shielded with a red screen to prevent light leak to the imager’s camera system and to all the dark-adapted eyes at a star party.

Non SGP Requirements

Finally, it should be said that the computer described above is for running SGP, and not for processing images or other tasks. SGP users often load other programs into the computer and use them while imaging. Some surf the web while imaging. Others process images. It is not at all unusual to load PixInsight ® and Photoshop® into the acquisition computer so that the imager can do interim processing just after the images come in. What if the imager simply wants to use the same computer for finish work? No problem for SGP. It can run in the background while the user is doing those other things. But those other things will undoubtedly require more powerful computers and more storage. So, in selecting the computer, be sure to factor in other uses besides SGP.


The next few pages give an overview of the types of software that must be loaded into this computer to run SGP. After this brief introduction, this handbook will spend a chapter commenting more specifically about how to download, install, and coordinate these software packages.

What software should one load into the computer? Well, Sequence Generator Pro of course. But there are other packages that the imager will want.

Fig. 2.4

Sequence Generator Pro comes in two versions, as described on their website.

And even with Sequence Generator Pro, there is a choice to make. It comes in two editions: Sequence Generator Lite , and Sequence Generator Pro. This book is about the Pro edition so we will only refer to Lite by referring you to the website (, which has a long list of features available in both editions. You may peruse it at your leisure. Both can be used to take a series of guided pictures on various targets on a given night. But the Lite edition requires more attention during the session, requires re-entering of hardware data, and misses out on meridian flips, automated focusing, the power of plate solving, and other tools and wizards.

The software downloads with the Pro edition and becomes Lite after 45 days if one does not upgrade to the Pro. The Pro edition offers full functionality for 45 days for free. If you do not license the Pro edition at the end of the 45 days, it is possible to get an extension by writing a request to SGP.

Behind the scenes at SGP, the program is calling on subroutines in the operating system, add-ons to that operating system, and apps that allow the various programs to work together. These programs are generally highly dependent on one another. Before using one’s computer to run SGP, one must install these other programs, and if they are already installed, they should be updated so they are all at the same level of compatibility. These include Microsoft.NET and the ASCOM PLATFORM.

Plate Solver

Sequence Generator Pro relies on a plate solver. A plate solver is a program that analyzes an image and picks out the stars. It finds patterns among those stars, analyzing the angles and distances between sets of stars. It then matches this data to information in its database. When it finds patterns that match, it knows where the picture is in the sky. Plate solving is critical to the imaging session because with it, SGP points the camera, rotates it if necessary (and possible), makes sure the composition is what the imager wants, completes a meridian flip so that all the subexposures are centered at the same point of the sky, and so on.

SGP can be used with various plate solvers, including PlateSolve2 from Planewave, Pinpoint from DC-3 Dreams Software, , Local Astronomy.NET server (ANSVR ), and Elbrus . PlateSolve2 is free, included in the SGP package, and very fast and powerful. Since the PlateSolve2 included with SGP interfaces directly with SGP, the user should not separately download the program itself. However, the user must download the appropriate database that PlateSolve2 uses. The user may also want to do blind solves, which do not need much in the way of hint (information about image scale and probable location). With an Internet connection, no additional software is needed. But the functionality can be obtained without an Internet connection when ANSVR is loaded into the computer. More about the different options in plate solving can be found in Chapter  18.


To make sure the imaging camera points to precisely the same place in space, and does not wander around, and to make it dither (move slightly between subexposures to reduce noise), SGP calls on an autoguiding program. Again, the imager has a choice of several, including PHD2 Guiding, Astro Art , and MetaGuide . Unlike PlateSolve2 for plate solving, the SGP download does not include any particular guide program. The SGP user must download and install the user-preferred program separately. Most SGP users opt for PHD2 Guiding. Chapter  3 will show more about downloading and installing it, and Chapters  16 and  17 will talk about other possibilities.

Drivers and Equipment Specific Software

Individual pieces of hardware will probably require a manufacturer-supplied driver, and perhaps an ASCOM driver. These are specific to the hardware, come on a disk from the manufacturer, or can be found on the manufacturer’s website, with a Windows automatic configuration system, or on the ASCOM website. Note that even four way USB adapters and USB-232 converters often require such drivers, not just the cameras and mounts. In the same sense, most imaging hardware will come with its own control program. Most of their functions are subsumed into the SGP interface. But at times, it is easier to simply enter the focuser or mount control program directly to carry out some functions.

Planetarium and Other Ancillary Programs

You may also want to install a good planetarium program like Cartes Du Ciel , or Stellarium , both free, and both able to control one’s mount. Starry Nights , The Sky X , and other such programs can be more powerful and useful but are more expensive. These planetarium programs can be connected at the same time as SGP and can look up target references, determine visibility of targets, help visualize and compose shots, pick targets, and so forth. Furthermore, since they can control the scope, they can park, slew, and so forth with more flexibility than the limited controls in SGP.


Having Internet connectivity is helpful at times. One can look up what other imagers have gotten out of a target, coordinates, and other information about a target, and so forth. Also, for SGP the Internet is useful in some blind plate solving and essential to the Mosaic and Framing wizard and some other target selection functions. Sometimes, an imager starting out may need to download a driver. So, of course, any computer should have a browser. However, once set up, SGP does not need an Internet connection.

Image Processing

Finally, most imagers will want do a little processing. So, go ahead and load in a favorite image stacking and processing program. Many SGP acquisition computers have a copy of PixInsight , or Deep Sky Stacker /Photoshop, or MaxIm to do some quick and dirty processing while they let SGP acquire more photons.


The minimum mount for an SGP installation should have the following:
  • GOTO capability: It must have the software, sensors, and motors that allow it to know where it is pointed, and the ability to move that pointing location on command. The pointing capability does not have to be all that accurate because plate solving will iteratively image and correct until the target is appropriately centered. On the other hand, it may be difficult to get a consistent pointing correction if the movement is not accurate enough (that is, repeatable – if told to move 12 arc seconds, it moves 12 arc seconds, not 5 or 17).

  • Computer connectivity: This requires a proper set of drivers and some kind of connection from the computer to the mount. This connection is usually in the form of a cable, and often a serial cable based on RS-232 protocol or USB. Often these ports are labeled “Aux” on the mount control panel. To get SGP to communicate with the mount, the mount must understand ASCOM.

Fig. 2.5

Astroimaging mounts come in all shapes, sizes, and budgets. (Google and the Google logo are registered trademarks of Google LLC, used with permission.)

Now, over and above these two minimum requirements are a number of quality criteria that the mount should meet. This handbook will contain some hints about what is needed in a mount for unattended imaging in Chapter  15, so we will not here discuss periodic error, weight capacity, balance , and other things that have to do with the mount’s contribution to the quality of a finished image. Although that is beyond the scope of this chapter, it is important to say that many times SGP is accused of failing when SGP is doing exactly what it is supposed to do. But the mount (or some other piece of hardware) is not performing as expected. If a mount is not balanced, guiding commands may never move the camera to where it is supposed to be. If the mount has serious orthogonality issues, a meridian flip will not work reliably. A mount that bounces around will fail to produce good images regardless of what a session manager tells it to do.

The mount does not need a separate guide port. This is often called an ST-4 port because it was originally used with that venerable guider. It allows a connection directly from the guide camera to the mount. After taking a guide image, the computer analyzes it and determines how long the mount needs to move and in which directions(s). It sends a signal to the guide camera just long enough to attain that goal, which in turn relays it on the ST-4 cable down to the mount. This system can be used, of course. But most SGP users prefer to use a direct connection from the computer to the mount. ASCOM takes over. ASCOM and PulseGuide contain much more information, including the RA and declination of the object, and side of the pier. You must already have this ASCOM connection in place to control the GOTO and pointing, so the ST-4 connection is redundant. You can skip attaching another cable to the system and get more information more easily.

SGP must treat some mounts differently from others. A classical SCT in a fork mount on a wedge, for instance, can image from horizon to horizon. It never needs a meridian flip. A German equatorial mount , however, often has a limit at a point where, if it goes any further, the tube will crash into the pier. To control this, it has safety stops, and sometime in the middle of the night, it must do a meridian flip – stop imaging, turn itself around, re-point to exactly where it should be, rotate the camera and/or change the configuration of the autoguider software, and so forth. SGP can be configured to handle the needs of most mounts.


Sequence Generator Pro does not care much about what type of telescope holds the camera. If it works for the camera and imager, it will work for SGP. Once upon a time, obstructed tubes (Newts, SCT’s, and their cousins) may have had some trouble with Smart Focus that refractors did not have. But Smart Focus has been improved and can be turned off. So, this is rarely a problem.


SGP does not require a motorized focuser. The imager can use a Bhatinov mask or feedback from SGP itself to focus the tube and camera by turning the focuser knob manually. However, motorized automated focusing is one of the great things about a session manager.

Motorized focusers come in two general flavors. One contains a simple direct current motor. The other contains a stepper or other digital motor and perhaps sensors. The first is a “relative” focuser. Start at a given position and move it in a few microseconds, and it should be a specific distance in from where it started. Move it out the same number of microseconds, and it should be back where it started. But it does not necessarily work that way. DC power ramps up and down. There could be slippage. Things happen.

The second type of focuser is an “absolute” focuser. Tell it to move a few steps in and it does. Tell it to move back that same number of steps and it is back where it started. The sensors or stepper motors tell it to do that. (Note that there still could be some slippage depending on quality and adjustment, but usually much less than with a relative focuser.) SGP will not work as well with the relative focuser. It works well with the absolute focuser, particularly a well-adjusted one with no slippage.

The simplest motorized focusers come with no control except a hand paddle with push buttons for “in” and “out.” These cannot be automated by SGP. The next step up also includes some provision for connection to a computer and some sort of control program. If you have such a control program, and it is compatible with ASCOM, SGP will be able to work with it. Focusers will be discussed in more detail in Chapter  13.

SGP can also work with temperature compensation . Many tubes shrink as they get cold. This alters the physical distance from the main optic to the sensor. However, this shrinkage (or growth as it warms) is generally at a fixed rate. For every degree of change, there is a specific shrinkage distance. SGP can use special thermometers to sense the temperature change and direct the focuser to move a certain distance to compensate for these length changes, keeping the stars in focus. Temperature compensation is not a requirement for SGP. And one does not need a special “temperature compensating focuser” to have SGP apply compensation. SGP can read the information from a separate sensor and make the appropriate changes.


One needs two cameras to get the most out of SGP. The imaging camera gathers the data while the guide camera keeps the imaging camera pointed at the right place.

Imaging Camera

Imaging cameras can be any single-shot camera that can talk to SGP with its native drivers or is ASCOM compliant. This includes DSLR’s, or dedicated astro cameras with CCD- or CMOS-based sensors. They can be one-shot color , or mono with (or without) a filter wheel. They can be cooled or uncooled. The single-shot requirement means that the cameras are designed to collect data for some time for each shot, and then send that data to the computer. This generally eliminates video-based cameras.

Guide Camera

Guide cameras can be any ASCOM compliant single-shot or video camera that works with PHD2 Guiding, MetaGuide , or AstroArt. This includes, at one point or another probably any camera that could be considered a guider. The list for PHD2 Guiding (at contains 26 names of cameras, some of which are “categories” of cameras. Surely camera compatibility with the guiding software will not be a problem.

Filter Wheels

To take color pictures with a mono camera, as many dedicated astro cameras do, one needs separate colored filters. When combined in proper proportions, these grayscale pictures take on color. To move the colored filters and hold them in place, the imaging system must have a filter wheel. These filter wheels hold anywhere from four (luminance , red, green, and blue) to seven, eight, and more (to allow for narrow bands and other filters). Once again, we simply apply the rule that if the filter wheel has an ASCOM driver , then SGP can be taught to work with it. A manual filter wheel could be used, of course, by telling SGP to pause whenever human intervention is required to change the filter. This, however, limits the automation of SGP.

Other Hardware

Sequence Generator Pro can control your mount, camera, guider, and filter wheel. This is what most imagers have in the basic imaging kit. But advanced imagers have a myriad of other devices to gather data and control the imaging session. These include weather sensors, thermometers, camera rotators, roof closure controls, observatory slit hardware, error notification systems, and such. In general, if it is ASCOM compatible, SGP can probably work with it. But this book does not cover some of these more rarely seen devices.

Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Alex McConahay
    • 1
  1. 1.Moreno ValleyUSA

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