Connect Your Telescope to a Laptop (January 16, 2011)

Posted: January 16, 2011 by tedbade in Apple Mac Tips, Space Exploration
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By Ted Bade, © Copyright 2011, All Rights Reserved.

If you have computer-controlled telescope and a decent Astronomy program, it’s a good idea to connect them. Astronomy software makes it easier to search and locate celestial bodies, plus it provides a lot more information about objects you might want to observe. Making the connection between your telescope and software is easy, and the results are rewarding. I will share a little of my experience and hopefully you will to give it a try.

First of all, I have a Meade LXD75 6″ telescope, which includes  a Meade Autostar controller. I use a Macintosh MacBook Pro laptop and for software I have Starry Night Pro Plus. Although the telescope’s computer does include a lot of objects in it’s database, I have had a number of issues with it over the years. The biggest one is that finding an object in it’s database is clunky and it provides little information as to where the object currently is, until you select it and find it won’t be in the sky until next winter!

With Starry Night Pro Plus, you get a simulated view of your sky, as it is right now, or how it will be tonight when you are out with your telescope. You can look at the screen and decide if an object is available for viewing or if it is occluded by a tree, the horizon, or other objects. Using the software during the day to make an observing plan for the night is always a good idea. We will take a look at connecting a Meade Autostar to Starry Night Pro Plus. The process described in this object works with other telescopes and even with other software packages.

Connecting the telescope’s computer to the laptop requires a bit of communication hardware. I expect, as time goes on, this will become easier and easier as amateur astronomy with a laptop becomes more popular. For now, we have to do a bit of engineering, but it’s simple and works well. The issue is that the Meade Autostar computer includes an older serial output while most computers (and especially Macs) only provide USB as a serial interface. The cable connection to the Autostar is a standard telephone connector.

This is an image from Wikipedia (http://en.wikipedia.org/wiki/File:Rj25_connector.jpg) This connector provides typical serial communication data (known as RS232). (If you want more detail on RS232, go here: (http://en.wikipedia.org/wiki/RS-232) On the computer end we have a USB connector. So to make the connection you need to find a way to convert USB to older serial and a way to change the connection to that found on the Autostar. This is easily done.

Note: even if you are working with a Windows machine that includes an older serial connection, you will need to interface the telephone connection on the Autostar to the standard DB9 connection. (For an image of a DB9 connection look at: http://en.wikipedia.org/wiki/File:9_pin_d-sub_connector_male_closeup.jpg ) The description for connecting to the USB port includes all the part you need to do this.

For converting USB to older serial, you can purchase a USB to serial adaptor. Several companies make them. The only important factor is that the computer you are using recognizes the adaptor. They are relatively inexpensive, generally under $30USD. I use one made by Keyspan. You will note that this adaptor has a standard USB connector on one side and a DB9 “male” connector on the other. The next item you will need is an adaptor to connect the DB9 output of the USB to serial adaptor to the telephone like connector of the telescope.

The LXD75 package I purchased from Meade included the adaptor, since the package includes some rudimentary software to connect the scope to a computer. If you don’t have this adaptor, a kit for connecting the telescope computer to a laptop is available from various astronomy supply stores. Alternatively, you can buy a kit that lets you build one and assembly is easy. You will however, need to find out which wires from the telescope computer need to connect to the wires going to the USB serial adaptor. I am not going to try to explain this process, since it can be a bit involved.

This might sound a little complex, but it isn’t. A USB cable from laptop to USB/serial adaptor, module to convert DB9 to telephone, then a longer telephone cable to connect to the Autostar’s Auxiliary connection (It’s the smaller of the two on the bottom of the Autostar.

With cables in hand, it’s time to take the scope and laptop outside for a night of observing. The Autostar will “tell” Starry Night where the scope it pointed,  so it is important to align the Autostar before connecting it to the laptop. For me, this part of setting up the telescope is the most time consuming, because I want it right. It can be frustrating trying to find a deep space object when looking in a part of the sky that is even little off from where it should be.

Note: A professional astronomer would use other means to locate an object, like guiding stars and general positions. This article is intended for amateur astronomers who want to use their Autostar devices with a laptop.

The LXD75 has what is called a German Equatorial mount. The first important step for aligning the telescope is to get it pointed exactly north and make sure it is level, then align the telescope with the sky. The Autostar offers two and three star alignment. I try to use the three star alignment when possible. This can be frustrating to people in the NorthEast US with lots of hills and trees. Often several of the stars the Autostar want’s to use for alignment are occluded by trees or houses. I know my yard and have a few “sweet’ spots that make it easier to align the telescope (at certain times of the year). I suggest that you check out the sky at your observation site before setting up the telescope. You might find a position that favors easier alignment. Other types of telescopes have other methods of alignment.

Once the alignment process is complete, you can connect your package of adaptors and cables to the laptop running Starry Night. After this is done, select the “Telescope” tab then click on the “Configure” button at the top of it’s Setup section. A menu opens asking you to select your communication port and your telescope type. On the standard MacBook Pro, there is a built in Bluetooth port, which will be on this menu. You should also see the USB/Serial adaptor you have plugged in. I see two items on my Mac: one is called KeySerial1 and the other is USA19H1d1P1.1 (This number is the model number of the adaptor). I usually select the USA19H1d1P1.1. Next select the telescope type. The Starry Night list doesn’t include my LDX75, but it does have a Meade ETX Autostar, which works fine with the Autostar on my LDX75. The menu lists telescopes by other manufacturers as well. I keep hoping that Meade will modify this list to either include the LXD75 or change the ETX Autostar to just Meade Autostar to reduce confusion.

If everything was done correctly, you now have Starry Night connected to the Autostar. The Starry Night display should change to reflect where the telescope is centered. If you haven’t moved it since you completed the alignment, Starry Night should be centered on your last alignment star. If the Starry Night display doesn’t move, move down to the bottom of the “Telescope” tab and be sure that the  “Follow Scope” check box is clicked. If it is not clicked, when you turn on this feature, the Starry Night display show move to center on the object the telescope is centered on.

Now, you should be able to right click on an object in the Starry Night screen and tell your telescope control to center on the object. In theory at least. Do not think that the alignment is precise. It might be, but more then likely it is close or just in the general area. There are many factors that can go wrong when aligning the telescope and plenty more can alter the alignment after the alignment process is complete. Luckily, using Starry Night is a great benefit when alignment isn’t perfect. So unless you have perfect alignment, the object you seek to observe will be somewhere in the field of view, rarely in the center of the view. Before you start increasing the power of your eyepiece, you should locate and center the object.

Some objects are obvious using a low powered eyepiece. But many fainter ones might not easily be seen until you have a higher powered eyepiece. In any case, when you you are looking for something in the center of the view and it is off to the left, you might never find it! Because Starry Night displays the sky, you can use the image on the screen to guide you to the object you are trying to view. Look at the Starry Night display noting the sky around the object of interest. There are probably some stars making a pattern nearby. If you can find them in the scopes eyepiece, you can make small adjustments to the scopes position to better center the objects location.

One very useful feature of Starry Night Pro Plus is a feature that lets you create different “Field of View” settings. The program comes with some sample ones, but I created a set that includes my 6” Meade telescope and several of my eyepieces. Using this feature I can change the field of view to match the 26mm Plossl that I typically use as the first eyepiece. If I do this, while centered on the object, I can get a view of the sky as it should look through that eyepiece. This makes it even easier to find a guiding star pattern to improve the position of the telescope. Once you do find and center on the object, you can make a correction to the alignment by telling Starry Night that the current position of the scope is really where the object is. The view on the screen will center on the object and future searches will be easier.

During observation sessions, I generally, turn the “Follow Scope” button off. I let Starry Night show me the position of the next object on my list, then slew the telescope to it. Sometimes, I will search the Starry Night display for objects of interest, then slew the scope to see them. One problem with an observing list is the timing. I might have to wait for an object to rise above the trees or a building.

The final aspect of this process, is good observing and creating a log of your observations: another good use for StarryNight. It provides the ability to make an observation log entry which can include your personal thoughts, the equipment you used (as well as the strength of the eyepiece), and the conditions of the sky. It’s fun to keep a log of the objects you view, making note of anything you notice that is special, then comparing this at a later date.

There is a Bluetooth based option which I have seriously considered but haven’t tried yet. This device plugs into the Meade Autostar and creates a Bluetooth connection to the Laptop. The big advantage of this is that there are no cables laying on the ground which you have to remember to avoid when moving about and that the computer controlling the telescope doesn’t have to be right next to the scope. Perhaps someday I will give it a try.

I hope this helps you. If you have any questions, you are welcome to contact me here.

- Ted

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Comments
  1. patirick jensen says:

    lap top what about your phone like head phones and make it also a camera port for a lense so you can take pictures reducing coast of production

    • patirick jensen says:

      you could also make it detachable lens so you could use it multiple like camera telecope night vision water vison poloarized
      slow motion etcc….

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