This site is to document how to track satellites - computerized mounts and telescopes help. It might be called "how to track satellites more easily, using common cameras or even computerized tracking systems" but that name is too long. At first this site is going to describe how to track with a commonly available camera and it will also cover (in a linked page) the use of a Meade drive and their Autostar software (see below for why that was chosen). Probably people with these systems know a lot about them, including how to observe astronomical objects, but the techniques and sources of tracking satellites may be new. The Meade user's manual has pretty pathetic instructions for people, and it could have easily included far better web page URLs. Hopefully one day I can include how to add a telescope on the Meade drive, this allows a site to track much fainter satellites. 

There are a number of sites that talk about tracking and even show the history or results, but I have not yet found one that tells someone how to set up a site and get started. I got hints about Astrometry.net, I got hints about FITS files, I got hints about SAO Image DS 9 - but putting that all together has been very frustrating. So I created this site, with inexpensive cameras and available software anyone can track satellites and generate observations. 

By the way the REAL trackers use video cameras, they allow you to produce many observations per night. But it requires more money and more expertise, I might get around to documenting some of that. 

Now there are a few older sites that show the early results using custom software, hand built drives, etc - we owe a LOT to the pioneers. 

Caveat

You can take observations with common hardware - a digital camera, a smart phone, a laptop, and a tripod. This will only let you track the brighter satellites, later I will describe how to find them. I have a used Nikon D300s with a 50mm fixed focal length 1.8 lens (after starting with a 1:3.5-45 35-105 zoom lens) and a (not needed after all) GP-1 (GPS) unit. My total cost so far is about $385 - I should have started with the faster lens but thought that I might need to use a longer focal length like 70mm. But when you zoom out like that the lens is very "slow" and the images are very dim. I upgraded to a D300s so I can record video; I started with a D200 which cannot take video but I have not figured out if the video is usable. I will certainly keep the D200 as well since it works great. To point my camera I use an application on my iPhone, Orbitrack. It shows me the path that the satellite will take and helps me find a star to point at, one that the satellite will go past. I actually just hold the camera against the back of the camera to get started pointing. I am now working with Satellite Chasers as well, it is different but gives some good options. 

You need to know, within a tenth of a second, the time. That is a real challenge. The GPS unit does not help with that, the GPS has turned out to not be necessary but it is darn handy if you are moving and want to record your location (when you are tracking satellites you do not move!). 

If you are doing this and want to know how to get accurate time - send me an email. A pal of mine built a shutter timer that gives me very accurate time of shutter opening from GPS. 

I use the shutter timer to get the precise exposure duration and start time.  To accurately record my location I use an application on the iPhone. 

So I use Orbitrack to look at a short list of satellites that I am interested in, I go out several minutes before one passes overhead and get the shutter timer set up. Then when the satellite comes by I use Orbitrack to point the camera and then I manually take photos.

I hope to update these pages over time to tell people how to calculate an orbit for a satellite and to later update that orbit. 

My efforts are all using Macintosh computers but many people use Unix or the other major operating systems, see the Hardware/Software section below for more explanation of the satellite prediction software. 

Motivation

Governments that launch satellites have a responsibility to ensure that people on the ground below are notified if objects that they launch are about to impact the ground. The US government took it on itself to be the world's authority on what is in space and along with that came the ability (and perhaps the responsibility) to alert the world when objects are known to be reentering. One of my tasks, early in my career, was to track the Skylab space station and help predict its reentry. I want to track satellites to gather more positional information which will help predict impact times (and general locations) of some objects that will NOT appear in the available warnings of reentering satellites. Our government pretends that a whole class of satellites does not exist and so they do not warn people when they are about to reenter. The following article is one that I wrote to point out that the US government needs to do a better job of warning people about satellites that are likely to survive to hit the ground. 

https://www.thespacereview.com/article/3397/1

Overlap

This site does overlap somewhat with a couple of other sites and projects I have, and I will (when appropriate) link to those sites. But the intention here is to help people get started tracking satellites.

Hardware/Software

A simple system could consist of a tripod, a digital camera, a smart phone, and a computer. I have gotten some very acceptable results (I have had to wait weeks until the sky was clear enough to see any stars). You need software to tell you where and when to look, see the link to another of my pages just below; I use Macintosh computers in this effort. The Mac records the time from the shutter timer using a serial interface. 

With the complicated setup that we are using, it could help to have some satellite prediction software running, the software I use is on my Macbook Pro, it's Gpredict. The site linked next tells you how to get Gpredict running. This may one day help me to plan observing sessions but I don't use it today. 

How To Use Macintosh Computers To Track Satellites

When I have the photos I use a web Astrometry program and an application like SAO Image DS 9 (see below), I will continue to update these directions. 

Now Let's Take Photos Of Some Satellites

I use the Orbitrack app that shows me the sky above with the stars and the satellite - it is good for "instantaneous" tracking. It shows the satellites that are very interesting , with Orbitrack you can see the path that the satellite will take, and I pick out bright stars near that path that I use to point my camera. 

Camera settings: I need to get a new application for my iPhone to get the most accurate time and then set the camera clock manually. I had one but the authors stopped supporting it. This way you know the approximate time of the exposure. Set your camera to take a 5 (or 10 or 15) second exposure, after a 2 second delay. So when you push the button to take a photo there is a 2 second delay to allow the camera vibrations to damp out. ISO rating should be set at 400, this is pretty high. But you will have dim satellites and stars in the image and they will not show up unless you use a high ISO. When you get the image, there is software (to read the EXIF data) that allows you to get the approximate time of the exposure. By the way do not synch the time between your computer and the camera, if you have a high speed connection you will synch all right but even then the time is accurate within a second or so. The shutter timer gives me the actual time of the exposure and the shutter duration. 

Select an upcoming object that has a good elevation pass - like 20 degrees or more - and will be visible for several minutes. In the evening, if the satellite is East, North, or South of you that can easily provide good illumination. In the evening, passes to the West will be back lit, those have not been useful. Higher elevation passes are better but I have gotten some good photos at low elevations to the North and South. 

Use a camera on a tripod, point the camera towards a point that you know the satellite will pass through. I often pick a bright star that the object will go close to (using Orbitrack of course) and point the camera towards the star so I can see it in the view finder, then I sometimes have to nudge the camera towards the satellite track.

I am hoping to track more distant satellites, but have not yet. 

When the object should be coming into the field of view, push the button to take a photo. The idea is to NOT follow the satellite, we want a photo where the stars are points but the satellite is a streak. So the camera will NOT follow the satellite (in the below 20 second exposure I don't see any smear due to "sidereal" movement in that short time). I think that there is some other reason that the stars show short streaks. 

The photo below is USA 281, Future Imagery Architecture Radar, NROL-47, going by; satellite number 43145.

In this sample you can see stars in the photos as well as the streak from satellite number 43145, in the top center. I used "Photos" to brighten the photo to help me see the streak. This was shot at ISO 400 and that produces an acceptable photo. 

We have a lot of light pollution in my area, to get any usable photos I have to wait for a cold front to come through and then take advantage of a few clear nights after it. 

The photo below is more typical, the streak is in the bottom right and is dim. You have to look at these in a darkened room. 

Generating Observations

Once I get usable photos I need the exact time of each end of that streak and this has been a big challenge. 

The shutter timer gives me the time of the shutter opening in my D300s (while with the Nikon D200 it would give the time of the shutter closing). 

Then I upload them into nova.astrometry.net and this "resolves" the image; it identifies stars and gives angles to them. It is an image with the angles to recognizable stars imbedded in it. A pal wrote a Bash script for me which loads a folder of images and gives me the needed results quickly. 

Next I go to SAO Image DS 9 (which is an application on my Mac), that gives me a window with the image in it. I had to get that application, expand it, and install it on my Mac. With the output from nova.astrometry.net I just double click on the image results file and SAO Image DS 9 opens. 

The small window on the upper right is an expanded view, put the cursor on the ends of the trail in that window and note the FK5 numbers - these are Right Ascension and Declination of that point. You can get RA and Dec for the beginning end of a streak like this and figure the time of each point. 

Next you format the observation to mail it - I am using the IOD format - and type the observations into an email. Send that email to the SeeSat list, Mike McCants, and Ted Molczan. After MUCH experimentation I am still trying to get the right combinations to get usable observations. 

So after a lot of looking around and getting software and installing it and making lots of mistakes, this process is getting more automated. Yes I am going to add some illustrations here! Sorry that I am updating this when I have available time. 

This site is NOT complete but it might help people get started - you might be able to fill in the gaps that I have left. I continuously update this site as I improve my techniques. 

If you have a Meade computer controlled drive system and the Autostar software, go here.

Of course this site is copyrighted by Charles Phillips, you may not use any part of it without permission.