Stellarium with a Celestron NexStar 8SE

Using it for the first time during the 2018 Perseid meteor shower


A brief history of my interest in astronomy....

When I was much younger, my parents did their best to get me things for Christmas that might spark an interest in various things.  Music, astronomy, computers, chemistry, and electronics.  STEM stuff, basically.  Many of these kits ended up in the land of forgotten toys.  Which was the early fate of my first telescope.

About 25 years ago, during Summer break before my last year of college, I found myself living in a fairly remote town in Washington and a little bit bored.  With some renewed interest, I decided to get my old telescope out and set it up to see what I could see in the night sky.  I was so amazed at being able to see planets like Saturn and Jupiter and the Horsehead Nebula in Orion's belt.  The scope my parents got me was simple.  It was a very basic Tasco 851TR telescope.  It had a 900mm focal length and an equatorial mount.  As it turns out, it had a really really good equatorial mount on that model and it sounds like later products were not as good.  


I taught myself about how to align it with Polaris and then use the right ascension and declination in some celestial object charts to find them.  There was no motor so I had to manually turn it to the right location in the sky.  In order to keep tracking the object in the eyepiece I would have to manually turn the position knobs on the mount (the two parts marked "D" in the above diagram).  It was so much fun!  I would stay up so late into the night that the lens on the scope would start to have condensation on it from the dew in the atmosphere as it cooled off.  I would stay out from 10PM to about 2AM or 3AM sometimes.  The telescope also had some panels to allow safe viewing of the Sun during the day (two parts marked "J" in the above diagram).  Which allowed a magnified view of the Sun that would reveal sunspots.  After years of sitting in storage, my scope finally got some use.  And then I put it away again.

Fast forward to 25 years later, after a career and lots of big things happening in life, I recently found the financial ability and desire again to get a new telescope.  I did my research about how to buy your first telescope.  There are so many options for beginners it was a little overwhelming.  The basic goal was to find a scope that would be used and not put into storage.  Not too expensive, not too small, not too difficult to transport, just right.  The telescope I chose was a popular 8" Schmidt-Cassegrain Celestron NexStar 8SE.  I also got the basic lens kit to go along with it since I wanted more than only the 25mm lens that sells with the telescope.  



Enter Stellarium....

Stellarium is a free GPL software which renders realistic skies in real time with OpenGL. It is available for Linux/Unix, Windows and MacOSX. With Stellarium, you really see what you can see with your eyes, binoculars or a small telescope.

I've been using Stellarium for a while now to see what is in the sky on any given night.  It's a cross platform application actively maintained and used by amateur astronomers everywhere.  It was a happy discovery that Stellarium has a nice telescope control plugin that is NexStar compatible.  NexStar is basically the motor controller for the telescope mount that has all the software needed to align and track objects in the sky.  Because it can communicate with Stellarium, the process of finding things to look at and track is much less time consuming.  The software/telescope sync allows centering on an object on a computer screen and then to automatically move the telescope to the precise location of the object.  In real time.  This is very exciting given my experience manually tracking objects.  This kind of setup helps amateurs to spend more time seeing deep sky objects, planets, star clusters, and nebulae.

There are a lot of videos about how to sync and setup the scope that are a little old but still relevant for this telescope.  The biggest change with the NexStar 8SE controller is that it now has a mini USB port instead of an RS232, or serial port adapter.  Modern laptops no longer have a serial port so it is a much needed improvement.  Here is a great video from 2013 that shows how to set up Stellarium to work with the serial connection to the telescope. "How to Connect a Telescope to Stellarium". Note that in that video from 2013, special USB adapter cables were required.  Even with the newer micro USB port, a virtual serial port is used to communicate between the software and the telescope.  However, the cable is much more common.  When using Windows 10, the Device Manager is used to discover what COM port needs to be assigned in the Stellarium telescope plugin setup dialogs.  This was not well documented in the telescope manual.  Here is one source about how to set that up in Stellarium on the telescope control plugin wiki page.  After a little research into how to set this up for my software/hardware configuration (Windows 10 running Stellarium with the USB 2.0 NexStar adapter cable) I was able to pretend to align the scope to stars while in my living room and try out the automated tracking control.  The idea was only to see that selecting an object in Stellarium, when connected to the telescope, that the scope would track.  It worked better than expected.  A good way to describe what Stellarium looks like when the telescope is slewing (moving into position) is how the reticle moves on the star map from the movie Stargate.



Perseid Meteor Shower of 2018....

In what has now become sort of a tradition, I get together out in the country with folks around August 12th to visit and stay up late to watch the Perseid meteor shower.  After years of experimenting with different ways of sitting, laying down on the deck with sleeping bags, and various lawn chairs, we've discovered a type of chair called a "gravity chair".  Gravity chairs are really great for allowing comfortable reclining to look straight up at the starry night sky.  Depending on the desert temperature the chairs also work with sleeping bags when it's cold.

This year was supposed to be a very big year for the Perseids since the New Moon was happening at the same time as the predicted peak of the meteor shower.  Which meant very dark skies.  There was a lot of excitement from the astronomy community such as this post by This looked like the best graphic of the event I saw on social media.  It showed where to look in the sky, what day, and what time.


I had my telescope and laptop ready to add to the excitement of the meteor shower.  

Setting up the telescope....

There are instructions in the NexStar manual for aligning this telescope and I found that after researching forums and through trial and error that the best alignment approach for me was the Auto Two-Star Align method.  I chose Polaris and Deneb as my two alignment stars because at this time of year and at my latitude they are the best and brightest available.  The instructions are detailed and aside from making sure the tripod is level, the one tip that helped a lot was to use the manual motor direction keys in a specific way.  Move the star into view first with the Down and Left arrow keys, but always only use the Up and Right arrow keys for the final movement that aligns the stars in the center of the eyepiece.  There is some accuracy loss when not following that guideline due to the nature of how the gears can backlash as the telescope slews into position.  I found this to be very true and with some practice, I've been able to almost perfectly align an object in the center of the eyepiece every time.  Of course, do not trip over the tripod after an alignment.  If that happens, it is very likely that alignment needs to be done again.

After alignment with the NexStar is complete, the USB cable can be connected to a laptop running Stellarium.  The telescope plugin can be started, provided all the COM port settings are accurate.  Then the fun of slewing to deep sky objects and planets can begin.  

At this year's meteor show, I did in fact see one meteor pass through my field of view while looking through the telescope eyepiece.  That was very unexpected and unlikely!  As for the normal viewing of the meteor shower, I think the best part was seeing two meteors come into the atmosphere in roughly the same direction and at the same time.  With very long tails.

Using the Stellarium application, I recommend use of the Bookmark feature so that you can create a log of the objects that were viewed, when and where.

Everyone this year really enjoyed seeing Saturn and its rings.  The Globular Cluster in Hercules wasn't bad either.  Not to mention the Perseid Meteor Shower.

Clear skies!