Nexstar Scope + Palm Handheld + Astromist + Bluetooth =
Wireless Observing Freedom
By Rick Unland

Being a techno-freak, I just can’t help but try to merge all my hobbies with computers and new technologies. Having recently acquired a Celestron NexStar 11 and being a Tapwave, Zodiac 2 (Palm based handheld) user, I naturally wanted to put them together. This article will cover what it took to get my Zodiac connected to and controlling the NexStar, and how it may wirelessly replace my laptop-based system in the field. While my article is specific to both the Zodiac and a NexStar 11, I believe that any other Palm PDA capable of running Astromist should work quite well. For those Palms not having Bluetooth built-in, there are quite a few cards available which provide this capability. If Bluetooth is not available for your Palm, then a direct serial connection should be; this might require a custom cable for your specific device.

Some time ago I purchased a Palm based planetarium program for my Zodiac 2 (www.tapwave.com) called Astromist (www.astromist.com). I purchased it to help plan observing sessions with my binoculars and to re-familiarize myself with the sky after a hiatus from amateur astronomy of almost ten years. In the manual and on the website the developer (Cyrille Thieullet) made mention of the built-in telescope control features and their compatibility with Bluetooth devices. With my new NexStar 11 sitting downstairs and another 10 weeks of cloud cover forecast J, I decided to see how cool a wireless control system would be.

Starting with a Handheld

My handheld is the Zodiac 2 from Tapwave (http://www.tapwave.com/), one of the more unique Palm based handhelds available. Standard features include a 480x320 screen, Bluetooth, joystick, game pad like trigger buttons, and a Stereo Mp3 player. Dual SD memory card slots allow for a huge amount of storage and the 200Mhz Arm processor really rips through calculations. There is even software available which allows me to play Divx video from the memory cards in awesome quality. I was actually listening to music from the Zodiac speakers while running Astromist and having it send goto commands to the NexStar 11; rarely was the music interrupted due to processing of the goto. A last minute update is that Tapwave is now defunct and if you want a Zodiac you better get one quick! This all happened suddenly around the 25^th

Next Comes the Software

First a short description of Astromist is called for. Astromist is the work of Cyrille Thieullet and is an amazing piece of software. Taking full advantage of the Zodiac’s 3.8” 480x320 color LCD, Astromist’s planetarium display renders remarkably well on such a small device. The Zodiac’s 200Mhz Arm processor & ATI graphics adapter make quick work of the calculations and screen updates are quite timely even with a 2.5 million star catalog working from the SD memory card.

Cyrille states on his website the following:

“Everything in the palm of your hand and always in your pocket

Like inside a real planetarium, you will be able to browse the whole sky, focus your attention on planets or any other object and discover more and more of details and informations. No added descriptions are needed: the screen copies speak for themselves.” Sic

Many screen shots for the application can be found at http://www.astromist.com/. I have included a few captured myself with which to illustrate this article. The first is the Wizard screen whereby you can access settings, preferences, and display properties for the sky, as you would like to see it. The wizards allow you to select object categories such as Nebulas, Solar System objects, Double stars, and other object categories for display in the planetarium mode. There is also a planetary assistant, a comet assistant, a moon assistant, and others that are perfect when using binoculars or with a scope.

This second screen shot shows the planetarium mode in a 480x320 format. The Zodiac is capable of rotating the screen between portrait and landscape mode. In landscape mode the screen is very easy to read and very intuitive to control. Tapping an object centers it within the viewing window. You may also elect to have the “Object Chooser” dialog open after the object is centered which displays information about the chosen object. With the premium version, you can also have hundreds of photographic images available for a great many objects that can be displayed, both from the Object Chooser or the Planetarium. The software contains many, many more features and benefits than can be mentioned here, as this article is about using the software to control a scope. I highly recommend Astromist if you have a Palm based handheld. I have found nothing even close to its display quality and speed on this platform. I highly recommend a large memory card be used to store the databases as most of the larger ones will NOT fit into the handheld’s memory. As stated earlier, I use the 2.5 million star Tycho catalog from a 512Meg SD memory card and the screen refreshes are quite fast.

One last thing, when you purchase Astromist, request from Cyrille a coupon for purchasing the Aircable; the company that sells them will give you $10 off the $69.00 price when they bill you.

NexStar 11 GPS

Since this is the only scope I have capable of doing any computer hookups at all, this is what I will be referring to. Except for specific wiring and connectors, I see no reason why the following information might not be applicable to other makes and models of Goto scopes which use a RS232 interface and are supported by Astromist. There are two connections on the NexStar 11 that allow you to connect your scope to the PC or a handheld. One is on the base of the unit and the other at the base of the handheld controller. The connector at the base of the hand held is a 4 conductor RJ11 and the base unit uses the RJ12 connectors. This is a 6-wire connector similar in shape to an RJ11 phone jack with 6 leads or contacts. A standard computer control cable can be purchased from Celestron and the part number is Celestron #93920. This cable is a DB9 female to RJ11 connector. It plugs into a socket at the base of the handheld controller and is meant to connect from a computer’s serial port to the NexStar.

Getting your Scope to Talk Bluetooth!

Once you have a compatible RS232 cable for the NexStar (or your specific scope), you need to purchase a Bluetooth to Serial adapter, the one recommended by Cyrille and that I also chose to use is by Wireless Cable and is called the AirCable http://store.aircable.net/aise3.html. This device converts serial RS232 signals to Bluetooth communications in real time. While you can get a male or female DB9 connector on the end of your AirCable, it is recommended that you purchase the female version. This allows you to directly connect to a computer’s serial port for parameter setting of the AirCable. When my unit came, I had to make a power adapter for it. I chose to Velcro a 9-volt battery to the back of the AirCable. If you wish to do this as well, you can get a 9 volt battery terminal from Radio Shack for $1.99; its part number is Catalog #: 270-325. Next you need a Catalog #: 274-1571, which is a 3.4x1.3mm power adapter and is $2.99 for a two pack. Solder this to the end of the Battery terminals with the tip positive and it should power the AirCable for quite some time. My AirCable wasn’t working properly when it arrived; the power light never came on. I called and talked with tech support and they issued an RMA to replace the unit. It seems like a good company to deal with; as they were very helpful and said they would ship a replacement when mine arrived. I was able to get the unit to work with the scope successfully, though, so it may have just been a loose connection due to shipping. Other Bluetooth serial adapters can be found here http://www.thewirelessdirectory.com/Bluetooth-Product/Serial%20Port%20Adapters.htm. I haven’t used any but the AirCable so if you need to try the others, you may want to let me know how it goes and I can update this document to show which ones work and which ones don’t

Getting the AirCable Connected to the NexStar

The last cabling item required is a male to male DB9 (9-9MMNM ) null modem connector. This can be purchased online at http://www.computercablestore.com/SearchResult.aspx?CategoryID=697 for $4.98. I bought two, just in case I lost one. This company was quite speedy in delivery and everything came through as ordered. This connector goes between the AirCable and the DB9 connector on the end of the Celestron RS232 cable. This device is needed if you use a standard serial cable to connect to the AirCable. The device only reverses the Tx/Rx lines so that two devices can talk to each other directly. If you are handy with a soldering iron, you may wish to build all these cables and the Null modem connector as well. Plans to do this are in multiple places around the net and also available from Cyrille himself. If I were to build the cable myself, I would consolidate the null modem wiring into a direct connection cable from the AirCable to the NexStar plug, thus eliminating the null modem/gender changer.

Setting Things Up!

First you need to setup the AirCable, you do this by connecting it to a serial (db9) port on your computer. If you purchased the female AirCable, then the unit will mate directly to the computer without the need for any adapters. While Cyrille recommends using Hyper term for setting up the parameters, I have never had much luck with Hyper term and was unable to get the AirCable to program properly with it and decided to use Simple term Gold. You can download a 30-day version here: http://www.softpedia.com/get/Programming/Debuggers-Decompilers-Dissasemblers/SimpleTerm-Gold-RS232-Monitor-RS232-Analyzer.shtml

Once installed, you just need to setup the Term program as stated in the AirCable documentation. One thing that seems to have changed since Cyrille wrote his documents on the AirCable is that he tells you to do everything with Caps Lock On; this will not work and the AirCable will not respond if it is on. Once the device is connected to your term program, you need to set the following attributes:

1) AirCable must be set to discoverable (This allows other Bluetooth devices to see the AirCable) You might want to keep in mind here that keeping the unit discoverable means anyone with a Bluetooth receiver can see and add the device to their list.

2) Set the AirCable to generate a Pin ID, (this will generate a unique ID and add the ID number to the AirCable discovery label, when other devices see the AirCable, the name will display as (AirCable #####))

3) Next, you want to set the AirCable into Slave mode

4) Lastly, disable authentication on the AirCable, as you will be setting the AirCable up as a trusted device on your handheld in its Bluetooth settings when you pair it.

Putting it All Together;

Now that we have all the parts, you can connect them as follows. With all devices turned off, just go down the list:

1) Plug the Celestron control cables RJ11 end into the connector at the bottom of the NexStar Handheld Controller.

2) Attach the male-to-male Null Modem adapter to the DB9 end of the Celestron control cable.

3) Plug the AirCable into the other side of the Null Modem Adapter.

4) Plug the 9-volt battery into the AirCable and Velcro the battery to the back of the AirCable. (The green power LED should be lit at this point and the Blue LED blinking)

5) Turn on your NexStar Scope

6) Start your Palm handheld and go to your Bluetooth preferences. Turn the radio on and select the Trusted Devices button. Once in Trusted Devices, you should select Add A Device; after a bit of searching, you will see the AirCable listed. Its name will include a number; select the AirCable and when asked for the pin number to pair, enter this number into the requester.

7) The device will now be added to your Trusted Devices list and you should not need to do this again.

8) Finally, go into Astromist, select preferences, and choose your scope in the Scope drive drop down.

9) In the Scope Port drop down, select Bluetooth, and then OK.

That’s it, you can now go into the drop down menus in Astromist and choose the “Scope Control” menu item, or you can click the scope icon on the main wizard’s page. Either way, the control software will run, showing you the Right Ascension and Declination of the scope at present and allow you to choose a slew speed and direction. On the Zodiac, there is a great Joystick, which makes slewing the scope around the heavens effortless, to say the least.

In the planetarium, you can select planets, stars, galaxies, etc… and the scope will slew right to them. In the object chooser, you can search for items by their list category, name, or position in the sky. After playing with this setup for a few nights, I can honestly say it’s amazing. The ability to walk around without having to worry about tangled wires, to use a beautiful interactive planetarium, and to be able to search different databases, all at the same time, is really wonderful.

A last minute addition;

As an update to the above, after using this system for a bit I found another remarkable software program called AstroPlanner, which is also AirCable compatible, there is a group for it at http://groups.yahoo.com/group/astroplanner/. AstroPlanner is a fantastic, comprehensive observing planner that will blow you away with its capabilities. The blurb from the Yahoo group reads as follows;

“AstroPlanner is a software application for Macintosh and Windows computers that facilitates astronomical observation planning, visualization and logging as well as control of Meade telescopes that use the LX200, LX200GPS or Autostar controllers, Celestron NexStar scopes, SkySensor 2000, Astro-Physics GTO mounts, ServoCAT, as well as Argo Navis, Magellan and Sky Commander DSCs. It also incorporates the Best Pair functionality for selecting optimum telescope alt-az alignment stars and other features to assist with polar alignment. New in V1.4 are various enhancements for variable star observation planning and logging..”

Paul Rodman the author is live on the Yahoo group supporting his users personally. When I found the software I asked about Bluetooth support for the AirCable, Paul ordered one on his own to test it out. Within a day or two everything was working and Paul had written even a small application that he posted to the forums to configure the AirCable with. I heartily suggest you download this software and purchase it, the features and benefits are many and it is an excellent tool for both new and old astronomers. The AstroPlanner web site is at http://www.ilangainc.com/astroplanner/index.html

In conclusion,

Astromist gets:

5 Shar Pei’s for;

· Beautiful accurate displays,

· Ease of use with an incredible feature set

· Fantastic price performance at $39.00

· And a great interface

The AirCable gets:

5 Shar Pei’s for;

· Simple and easy to use device

· Great price performance at $69.00 - $59.00 with Astromist coupon

· Fantastic performance, I used it up to 25 yards from the scope!

· Programming the unit is quite easy

· A very cool blue LED (too bright though)

· Eliminating obnoxious wires I trip over in the dark

NexStar 11 GPS gets:

5 Shar Pei’s J for;

· Being the scope I have dreamt of having for so long.

The Tapwave Zodiac 2 gets:

5 Shar Pei’sfor;

· Awesome Hi-res screen

· Super Fast processor

· Dual SD card slots to hold lots of star catalogs & images

· Great price performance at $399.00

· Incredible Joystick to drive the NexStar around the sky with Bluetooth

· Letting me Play Joust during cloudy moments

· Ability to play my MP3’s over the built-in stereo speakers

· Playing back Divx videos of “The Astronomers” from PBS

AstroPlanner gets:

5 Shar Pei’sfor;

· Incredible Feature set

· Ability to share observing Plans

· Incredible customer support

· Great price performance at $20 to $35.00

· Full scope control with Bluetooth AirCable compatibility

· Contains all the Best Pair functionality of Best Pair II

· Plan Object and Observation import with PDAs

Clear Skies to all!

Rick Unland

All images are by the Author and are copyright!

Updated August 3, 2005