Automated guiding with a Tom Osypowski equatorial platform

My custom equatorial platform from Tom Osypowski has finally arrived! It is absolutely gorgeous and is extremely strong and rigid. From his advice, I purchased a dual axis aluminum platform. This is the ultimate visual and imaging platform for a Dobsonian. The platform is operable manually with a hand control as well as automatically by an ST-4 port. This allows me to use a guide scope and laptop to automatically correct for tracking errors in real time while imaging. In the first night, I was able to immediately go for one minute exposures with barely any noticeable trailing or tracking error. It’s almost magic!

In preparation for the new family member, I poured a concrete pad in the yard to give it a nice, level place to rest. I still need to finish it with some self leveling floor finisher, but a couple shims got me going for some test runs.

The guiding setup consists of an Astromania 60mm guide scope and an Astromania/Touptek SGCMOS monochrome guiding camera with ST-4 port. The camera connects to my computer via USB, where the PHD2 software monitors stars in the guide scope for movement and sends correcting signals back to the camera, which then sends pulses to the platform to correct in two dimensions.

The current imaging setup consists of the Nikon D5300 that I removed the red/IR filter from. This is mounted to a Baader MPCC Mk III coma corrector, giving me a full frame of pinpoint stars. Depending on the target, I either run a Baader UHC or Moon and Sky Glow filter. Images are captured using APT, and they are lived stacked for preview and filtered for quality using DeepSkyStacker Live.

Setting up the scope is quite easy with the optional polar alignment tool. This is the fixture hanging off of the south side of the platform. It’s a red dot sight that you point at Polaris by moving and leveling the platform. This gets you in the ballpark of the celestial pole, and is probably plenty accurate for visual observing. For imaging, I go one step further by using the polar drift alignment tool in PHD2, which tracks a star, and through some kind of magic, tells you how to adjust the platform to get the polar alignment pretty much perfect. I don’t know the details of how it works yet, I just know that it works really well.

After that, I do a bit of focusing of the main scope on a bright star using a Bahtinov mask and the hand control of my electronic focuser. With the platform tracking, the star is perfectly still in the live view of the camera, making focusing a snap.

Once I pick my target and get it nicely framed, I simply hit the guiding button in PHD2. It runs a calibration algorithm to figure out the dimensions that the pulses correspond to, and then it begins adjusting the tracking for the target in real time. The grid overlay in the camera view shows the affect of the right-ascension and the declination dimensions. The chart on the right shows the tracking error and corrective pulses sent to the platform.

Being able to take one and two minute exposures right off the bat is incredibly encouraging, and as I learn more about the equipment and software, I’m sure it will only improve. Not bad for the first night out! Check out these stars!

Here’s an example image of the Triangulum galaxy, composed of 35 one minute long exposures. I don’t find this fit for it’s own post, as with these really long exposures, the need for quality flat images is becoming apparent. Learning to take quality flats will be the next step in my journey. I’ve purchased a studio softbox for taking hopefully better flats, but I have yet to try it. A post about that should come soon.

In the end, the Tom Osypowski platform is worth every penny, and I know I will have years of great nights under the stars with it.