I’ve always been fascinated by astrophotography and I decided that my retirement hobby will be learning all I can about this challenging field.
My First Telescope
In 2011 I bought an 8″ Dobsonian telescope and enjoyed looking at the moon and Venus. Almost immediately I wanted to take pictures of them. I cobbled together some black plastic plumbing pieces and a Sony point and shoot camera. It was good enough to get some great pics of the moon and I was hooked.
I tried to use my telescope as much as possible but I quickly realized I was being eaten alive by mosquitoes. I also realized that looking at grey fuzzies in my eyepieces was not very interesting to me. So I set about putting together a new system that would accomplish two goals.
a)Allow me to take astrophotos.
b)Allow me to do this from inside my house.
My Current Set-up
I did a lot of research and decided that I would buy a Nikon D5300 camera. I think this camera performs well and I was happy that other astrophotographers were also using this camera. During the winter of 2017/2018 I had the camera Ha Modified by Kolari Vision.
I also decided I would buy a German Equatorial Mount. I discussed this with my local Telescope store and decided, in 2014, to purchase a Celestron CGEM. I like the size of this mount. It’s relatively easy for me to lug in and out of my house. I knew I would never have an observatory. I still use this mount for all of my astrophotography. It has lots of mechanical quirks which make it a challenge to guide with, but I found that with my programming skills, I was able to create programs that counteract most of it’s short-comings.
I decided to buy two telescopes. A Skywatcher BK80ED refractor and a Celestron 8″ EdgeHD SCT. Along with the BK80ED I bought it’s 0.85 Flattener/reducer and I bought a Moonlite high resolution stepper motor focuser and controller. Along with the 8″ EdgeHD I bought it’s 0.7 Flattener/reducer. I also invented a stepper motor focuser for the 8″EdgeHD which interfaces to the Moonlite controller.
I also bought a 2″ Moon and Skyglow filter and a 2″ OIII filter. I could only use these filters with my BK80ED and, for most of my Nikon D5300 imaging, I used neither.
I knew I would be autoguiding so I bought a 50mm guidescope and a QHY5II-M guidecamera. This gives me a guidecamera resolution of 6 arc-seconds/pixel which is a bit too large. The folks at PHD2 Guiding like to see guidecamera resolutions closer to 1 arc-second/pixel. I did some testing, in my basement, where I had the guidescope focused on a distant laptop screen displaying a black screen with only one pixel lit. PHD2 guiding was able to create a guiding graph that showed the image from the camera had a 0.1 arc-second or less resolution. I like to think that this was a test of the camera/PHD2 solution without the influence of atmospheric seeing. I concluded that the camera/PHD2 solution is quiet enough for guiding.
So what about controlling everything from inside the house?
When I bought everything, I also bought a 20 metre long USB2 powered extension cable. I combined this cable with a 7 port powered USB hub which is located at the mount. I typically use a 2 metre USB2 extension cable to extend a USB2 port from my laptop thru an open window where it plugs into the 25 metre long USB2 cable. I can easily replace the short USB-2 cable should it get damaged as I close the window onto this cable. The 25M powered cable costs significantly more.
In 2020 I bought a QHY294C OSC camera, a filter slider for 48mm filters, some extension rings and a L-eNhance Narrowband filter. I have the camera cooler powered by the Celestron 5 Amp supply. This 5 Amp supply powers everything except the Nikon D5300(when it’s used). Power consumption is usually 2 amps. I have a 5 amp in-line fuse installed just in case something screws up. I plan to post some articles about specific aspects of my set-up.
What’s in that wooden box I have on my mount?
There is a fair bit of kit in that wooden box. I made the box and it has the following bits and pieces inside of it.
-Celestron 5 Amp 12v power supply
-7 port powered USB-2 Hub
-Arduino Uno (Anybody out there an Arduino fan?)
-Moonlite Focuser controller
-USB2 to RS-232C converter for communicating to the handcontroller
Mounted to the outside of the box is a Kendrick 4 channel dew heater controller.
There are a few more devices that I have connected to my set-up. They primarily interface to the Arduino Uno and give you some insight of how I like to tinker with electronics. Please use the following link to learn more about how I have integrated an Arduino Uno into my set-up.
What software do I use?
I already mentioned that I wrote a program to interface to the Arduino mounted in the wooden box. This program has grow over the years to include lots of utilities which help me polar align, calibrate, focus, guide, provide periodic error correction, plate solve and sequence my cameras etc. All of them have been written in LabVIEW.
I began using LabVIEW by National Instruments in 1996. LabVIEW is a graphical programing language that has tons of mathematical functions and can interface to pretty much any kind of hardware or 3rd party software.
If I get time, I plan to repackage some of these utilities so that others can benefit from them. I explain the various utilities that are in the queue to make public on my Software page. CaLIGHTs is the first astrophotography specific program I have made public.
The first utility I created is for periodic error correction. This is a very complicated utility which went thru several versions. The latest has very high accuracy…so much so that PHD2 Guiding does not make any corrections for PEC. I have PHD2 Guiding tuned so that it is very sluggish and only corrects very slow trends.
The next utility I created was to compliment the Nexremote 2+4 align/calibration routine. I use Nexremote to calibrate my mount because I do virtually everything from inside my house. I have Nexremote running and my utility running. Nexremote will select the star and move the mount to the star’s location. My Search utility allows me to “see” the guidescope live video as my remote “eyepiece”. I can slew the mount in a square spiral search pattern and when the bright star pops into view I can stop the spiral search. I can then click on the star and press a Centre Star button which will move this star to the exact centre of my guidecamera’s field of view. I then tell Nexremote that I have the star centred in the “eyepiece” and Nexremote will advance to the next align/calibration star. It’s ends up working very well and it’s fun to do.
This technique causes my mount to be calibrated to the guidecamera and not the imaging camera. I normally correct this with the first alignment star by calling up a liveview of the imaging camera and centering the star in the field of view. Then I switch back to the guidecamera view and make manual adjustments to the guidescope at the mount so that both cameras are concentric.
I also needed some way to focus the telescope so I wrote an autofocus utility. I designed this utility to screen capture the live video of any app running on my computer. For my DSLR I use Digicamcontrol because it will give me a liveview from the camera via it’s USB connection. My autofocus routine allows me to position my mouse over a star in the liveview. If I then press the spacebar my autofocus utility will lock onto the star and performs a pseudo FWHM calculation that updates continuously.
This utility also communicates to my Moonlite focuser controller and allows me to adjust the focus position via ASCOM. Using an antibacklash technique my utility will sweep the focuser thru a range of values while it samples the FWHM values obtained from the live video displayed on my computer screen.
The focuser positions and FWHM values are then used to determine the optimum focuser position. Finally, the focuser is moved to the optimum position using an anti-backlash technique.
After trying to polar align using the Celestron All-Star-Polar-Align method I got frustrated trying to use it. After some research, I decided I could write my own Polar Alignment utility. It only requires a clear view of Polaris.
I’ve also written programs which interface to the QHYCCD SDK available for my dedicated astrocam (QHY294C).