Friday, May 2, 2014

Planetary Imaging Without a Tracking Mount

At home, I used to do some planetary imaging with a basic CG-4 tracking mount, a digicam and a small 102mm Skywatcher maksutov telescope. Now that I am in a foreign land, imaging becomes a bit harder due to the absence of my equatorial mount. To make imaging possible, I bought an inexpensive stable tripod for the telescope - a standard video tripod.

The first thing I do is to make sure that the finder scope is aligned properly. Try to center the planet visually first with a low power eyepiece followed by a medium power eyepiece. Realign the finder to make sure that what is at the center of the eyepiece is also centered on the finder. An accurate finder is a must here, I use an optical finder with crosshair. Red-dot finder is probably not a good choice for this kind of imaging.

Once alignment is done, I attach the camera and set it in video capture mode. Make sure that the focus is as accurate as possible when the planet is in view. As most digital cameras do not have a manual focus while in video mode, I opted to focus with the telescope focuser instead. To give me a longer amount of time to focus, I point the telescope to a spot where the planet will drift in place all by itself. Depending on the magnification used, it takes the planet around 15 seconds (for my particular eyepiece) to drift from one edge of the camera frame to the other. The trick here is to center the planet first then nudge the tripod control a little bit in the proper direction. This step will usually take some time and effort to get right, especially if you don't have a slow-motion control, like I do.

Once focus is as close to perfect as possible, it is time to do the actual imaging. Do the previous step again to let the planet drift in place, but this time, also start recording before the planet even appears in the frame. This will avoid the shake that will occur if you were to press the record button when the planet is already in the frame.

I usually repeat the focus and capture steps to make sure that I have a clip that has the best focus.

Here is my setup.

After the hard part is done, it's time to pack up and start processing the image.