Introduction to Robotic Astronomy - Part II
In Part 1 of this discussion, I talked about the objectives and basic components for home robotic astronomy and presented a couple of different alternatives to accomplish some armchair astronomy - or at least enough to give you some distance between you and the telescope. In the second half of this topic I want to explore some choices for your own robotic setup.
Let's review: The first stage of robotic astronomy is to get some separation between your telescope and a control location. This approach relies on one or many extended cables. For the most simple equipment and short runs, it can work. However, it doesn't scale well and it has some limits to range.
The second stage of robotic astronomy relies on two computers attached by a network. One computer controls operations at the telescope site with direct cabling to the camera(s), and telescope. The second computer at a distant site controls the telescope computer. This approach doesn't get any more complicated (or expensive) as the complexity increases at the telescope (for example: guidescopes, focusers, filter wheels), but of course the second computer adds to the initial expense.
Let's just take a simple "next step". Presuming we can setup a laptop computer at the telescope site (with telescope, camera and other device control), we can run a long length of Ethernet cable between the laptop and an indoor computer - a desktop system or laptop. This allows us to have a simple two-computer network using a single long (enough) cable. A length of appropriate Ethernet cable is inexpensive (a 50' length is less than $20). Most computers have built-in Ethernet adapters. Or you can buy inexpensive PCMCIA or USB interfaces to Ethernet. For the two-computer network, you can just buy a "crossover" cable (<$20). (OR YOU CAN GET A ROUTER THAT CAN CONNECT MORE COMPUTERS FOR $10-$40.)
With this setup, you connect the telescope, camera and other bits to the laptop that stays at the telescope site. Then you string your Ethernet cable inside to the control and monitoring computer inside. (If you use a router, connect the outside computer and the inside computer to the router.) Once you've established the network connection between the computers, you can then use "remote control" software to allow the indoor computer to monitor and control the telescope computer. Remote control programs show the screen of a remote computer and your mouse and keyboard commands are passed to the remote computer. For Windows XP/Pro, Microsoft provides remote control software. For other setups, you can use inexpensive or free third party products (The most popular free product is (Real) VNC and its variants (TightVNC and UltraVNC). Some newer free products like LogMeIn and RemoteIT offer basic systems for free as a gateway to more sophisticated retail products).
In the original example of Stage 2 robotic astronomy, I suggested an Ethernet cable. It's inexpensive and fast. However, many people have a wireless LAN at home primarily for sharing a high-speed Internet connection. If you have a wireless LAN, you don't need the Ethernet cable - you can use the existing wireless LAN if your telescope computer can contact the indoor wireless LAN. If the telescope computer cannot, you might be able to extend a long Ethernet cable from the wireless LAN access point to the telescope computer. (Most wireless AP's include a built-in Ethernet router.)
Let me give an example of how my Stage 2 setup works at home. It should help clarify some of the details. First, the basics:
In my backyard, let's say I set up my Meade LXD-55 mount (GEM) mount. The mount has a serial cable for telescope control for a PC. On the PC, I used the popular (and free) planetarium software Cartes du Ciel for telescope control. For a primary imager, let's presume I'm using my Starlight Xpress MX716 camera attached to a camera lens and this assembly is mounted on top of an 80mm telescope. I use MSB's AstroArt for camera control. (AA also can communicate with the telescope to record the coordinates of the image.) The SX camera requires a USB connection. For this basic setup, I can attach the USB and serial cables from the camera and telescope to my laptop (a 2002 vintage Toshiba laptop running Windows/XP home). Naturally, I can control operations from the telescope site, but I want remote control.
I've experimented with different free remote control software packages. The one I use today is "RealVNC", part of a family of products based on "Virtual Network Computing". To use just about any remote control products, you install "server" bits on the remote computer - in this case the telescope computer - and "viewer" or "client" bits on the controlling computer - in this case, the desktop computer in my family room. These computers can communicate using my existing wireless LAN. I have a Netgear 802.11G wireless LAN that operates at peak speeds of up to 108mbps. Wireless "G" products are very reasonably priced because they are on the downside slope of their lifespan. (In other words, one or two later product generations are on the market or nearly there.) The "G" networks are the first to have the kind of longer effective range needed for astronomy. My household uses the 802.11G network to provide wireless Internet access to 5 different computers and allow file and printer sharing. After 18 months, we're still satisfied with the product and I expect another year or two of service out of the setup.
Of course, my regular operations are slightly more complicated. For example, I like to use a webcam for autoguiding (through the 80mm telescope). I use the free GuideDog program to autoguide the telescope. (Other programs like K3CCDTools and AstroSnap can also do webcam guiding.) The webcam also requires a USB connection. My laptop has two USB (1.1) connections so I'm ok if I stop with just the two cameras. If I decide to add more stuff, I'd need to add a USB hub at the telescope site.
(Note that I have three programs that want to communicate with the telescope mount: Cartes du Ciel, AstroArt and GuideDog. But only one program can control the computer's serial port at a time. So how can this work? Via ASCOM. ASCOM is a free software suite that makes it easier for programmers to write programs to control telescopes - that's its primary purpose. But it also provides a software "hub" that allows many programs to talk to the hub while the hub has exclusive control over the telescope's serial port communication. My three programs connect to the ASCOM hub and the hub connects to the telescope mount.)
I need to align my telescope and focus the camera(s) manually at the site. However, once I've done that, I can ignore the computer at the telescope site and retreat indoors. There I can aim the telescope roughly using Cartes du Ciel. CDC can track the telescope's motion across the sky to the object I've chosen.
I can verify the position using the camera (with short exposures). I can tweak the position of the telescope using CDC, GuideDog, AA or other tools. I can identify a guide-star and let GuideDog start the autoguiding process. Then I can use AA to start a sequence of images. Normally, I like to take about 70 minutes of images for a deep sky object so a sequence of 12-24 3-minute exposures is typical.
After one sequence, I can locate another object and command the telescope to move to the next target. So what do I do while waiting? Sometimes, I start planning the next object to image. Next, I monitor the operations to be sure the autoguiding is operating correctly and the images are clean. Sometimes I sneak a cup of coffee and a little snack. Also, I can do some preliminary stacking on the images that have already been captured by the camera. Finally - and most popularly - I can do some eyelid observing: a 45-minute nap is very appreciated around 1 AM ! One other choice I've done a few times is set up a second telescope for the other kind of astronomy - the kind where you LOOK through the eyepiece.
So what can I do with this kind of setup? I've used the remote control for monitoring the sequence capture for a few years. But I've started doing more and more object acquisition so that I can operate inside for almost an entire night. My most successful night was in September 2005, when I captured several objects, including a 4-frame mosaic of the North American Nebula (http://www.frisk.org/jshuster/displayimage.php?album=14&pos=10) and also the California Nebula (http://www.frisk.org/jshuster/displayimage.php?album=14&pos=9 ). You can see these on my gallery site (http://www.frisk.org/jshuster/index.php?cat=10003) .
This setup can also be used for more sophisticated operations. When I prepare for a target, I use the basic goto capabilities of the telescope but I "manually" refine the position of the scope because the LXD-55 mount isn't perfectly accurate. With a more accurate mount you can actually script or program a series of targets for capture. Some amateurs are routinely surveying galaxies looking for supernovae. The robotic setup is not much more complicated than what I've described here.
There are other things you can do that go beyond the initial Stage 2 setup I describe. You can add a computer controlled motorized filter wheel. This can allow you to capture red, green and blue images from a monochrome camera by rotating a different filter into place under computer control. You can also use manual or automatic focusing software if you have an electronic focuser (I just discovered that the LXD55/75 telescopes can use a Meade accessory (APM909) that allows remote control focusing if you have a motorized focuser). And reasonably priced digitally controlled dew heaters are available. There's a growing market of integrated interface products to help reduce the clutter of cables and specialty interfaces such as AstroHub (http://www.aquest-inc.com/AstroHub/AHhotos.htm). In addition to hardware products, there is increasingly sophisticated software integration to control object acquisition, centering, focusing, filter management, etc. You can see that robotic astronomy is appealing to the gear jockeys among us.
But I need to issue a serious warning about robotic astronomy. DANGER, DANGER, WILL ROBINSON!! When you are out of sight and sound and reach of your telescope and camera, you lose some important cues about how things are going and you lose your ability to quickly intervene if something goes wrong. Telescopes have been known to wildly slew. Cables can get tangled. Cameras can crash into forks or tripods. Operators can fall asleep while the telescope gracefully continues tracking until ramming itself into the mount at the speed of one revolution per day. So if you choose to set up a robotic astronomy environment, you need to be careful to ensure cables are properly held in place, away from tangle points. You need to be sure that no slew command will cause a collision with the mount. And you need to be sure that an operator asleep at the switch won't cause a problem. If you don't take care you can damage expensive cameras, optics and mounts.
So far, I've kept the discussion primarily to telescopes, mounts and cameras. Looking way beyond the "introductory" stage there are "Stage 3" features like automatic roof/dome controls, sky quality sensors, Internet observatory control, and more cool stuff everyday. Meanwhile, groups like the ASCOM group are making it easier for software developers to integrate the control of virtually every device related to astrophotography including domes, rotators and weather stations. Literally, the sky's the limit.
If you are interested in getting started with robotic astronomy, you need to assess your equipment capabilities and requirements, and establish some specific objectives. Then you can decide whether to reach for the basic solutions or the intermediate. Perhaps you have many of the components in place for a Stage 2 setup. If you're eager to experiment or seek out the missing pieces, don't hesitate to ask members in person or on the LCAS group. If you have questions about the suitability for a specific camera, telescope, or software product, you might find a broader experience base on a corresponding Yahoo! group or other vendor forum. I also want to mention additional resources. Some of the challenge in finding things on-line is the ambiguity of "robotic", "remote control" and other terms. Many seemingly helpful sites refer to professional observatories that can be controlled via the Internet. It's very difficult to narrow the search only to the sites that discuss information about personal robotic or remote control setups, especially for folks just getting started. However, I did find an interesting paper by Technical Innovations (dated 2002) called the Remote Control Astronomy Handbook. (Some of the information is a little dated, but still helpful for background.) Also, on the Meade Advanced Product Users Group (MAPUG) I found a lot of general (and some Meade-specific) information in the Topical Archives. For information on the other products I've mentioned, I recommend googling the product name and if that isn't productive, ask the LCAS Yahoo! group for some help.
Hopefully you have enough information to start taking some small steps on your own. Be sure to share your experience and recommendations to the other club members.
MAPUG Remote Control: http://www.mapug-astronomy.net/AstroDesigns/MAPUG/Remote_Control.htm
Remote Control Astronomy Handbook: http://www.menkescientific.com/rcabook.htmlPublished in the May 2006 issue of the NightTimes