I have built a DIY off-axis guider (OAG) using a mirror from a DSLR camera, some tube extenders (2 in and 1.25 in diameter), and a webcam. Best guiding performance currently at 0.33″ (arcsecond) RMS error, at 900 mm focal length, using a mount with DIY controller.
In off-axis guiding, the telescope functions both as an imaging scope and a guide scope. In this configuration, a mirror or a prism receives a portion of the light without blocking the main imaging sensor, sending the light to a guide camera. In this build, I used a high-quality mirror I happen to have found in a non-working Canon 1100D. To build the OAG, I removed the lens from a Barlow so I could get a 1.25 inch barrel for the webcam attachment, and then fastened it perpendicular to a 2 inch extender, where an appropriate side hole has been made. I then fabricated a small mirror mount (like a secondary mirror mount in a Newtonian) using some brass material, to send the reflected light on to the side. The placement of the mirror and the proper spacing to achieve focus required trial-and-error. To use the OAG, focus the main camera first, and then slide the guide camera in or out to achieve focus.
When imaging targets using a DSLR lens, achieving proper focus may be difficult even when using a Bahtinov mask. Focus adjustments involving very small and precise steps can be achieved using a microfocusing mechanism. In this DIY project, I have modified a Canon 50 mm f/1.8 lens and tapped onto its built in electronic microfocuser. It uses an L293D stepper motor driver and an Arduino Uno.
The focuser is ASCOM compliant and works with astronomy software such as the Nighttime Imaging N Astronomy (NINA) for automated focusing during unattended imaging. The modification should work with any lens with built in electronic focusers.
I’ve built a simple DIY intervalometer for deep-sky imaging, to enable my DSLR camera to take a series of photos of galaxies and nebula. It features a rotary dial with preset exposure times. When used with an autoguider setup, the intervalometer allows taking unattended exposures, while the telescope tracks a galaxy or nebula.
I’ve built a remote shutter switch for my Canon 50D to enable it to take exposures longer than 30 seconds, which is essential in astrophotography. Since the camera already has a battery grip, I just bypassed the battery grip’s shutter button and put an external switch. To make it removable, I used a wire that plugs into a socket hidden neatly in the battery compartment.
I’ve built a DIY battery adapter for a Canon 1100D using a 12V power connector, a power supply regulator, and housing of an old battery. The DIY adapter provides power to the DSLR from a DIY field battery for extended use during imaging sessions.
I have performed filter modifications on a number of DSLR cameras (Canon 450D, 700D, 1200D, 500D, 1000D, 1100D, Nikon D3100, and Fuji X-A1) for me and my colleagues. It involves the removal of the stock UV-IR filter, making the camera more sensitive to H-alpha wavelengths. This modification is helpful only when shooting targets with H-alpha emissions, as most DSLR camera’s standard (stock) filter blocks this part of the spectrum.
Take note of the shift in white balance (reddish hue), which is to be expected in this type of modification. Focus will be affected, your camera may no longer focus with compatible lenses unless you add a filter between the lens and the sensor, to address the shift in focus and to filter out UV-IR. If used with telescopes, you need a DSLR-to-telescope adapter and achieve focus using the telescope’s focuser.
Here are sample images taken with the cameras I have modified (posted with permission).
During an exposure, the imaging sensor of a DSLR warms up, resulting to noisy images. By cooling down the sensor, it is possible to eliminate or somehow minimize this thermal noise.
I have made a number of attempts to accomplish this with a Canon 450D and a Peltier module, however, it appears it is very difficult to implement without running into problems such as condensation and frosting.
The Logitech 4000 webcam is capable of imaging planets and can be modified to take long exposure images to serve as a guide camera. The modification requires a serial port to externally control the camera’s exposure time using a guiding software such as GuideMaster and PHD Guiding.
The long- exposure modification allows the camera to detect faint guide stars, which is a useful feature for a guide camera. The diagram shown here was a modified version of M. Burri’s (2002) parallel port interface for a Logitech 3000 which I have adapted to work with the newer Logitech 4000 and a serial port.