I’ve built an electronic automatic focuser (EAF) for my Tamron 80 to 210 mm telephoto (zoom) lens for automated and precise focusing. The focuser was built with a stepper motor, an A4988 stepper motor driver, an Arduino Uno, and a repurposed azimuth adjustment mechanism of an old Vixen mount.
DIY microfocuser for a telephoto lens
Vixen’s alt-az mount azimuth lock mechanism happens to be wide enough to fit a telephoto lens. It allows fine movement using the fine adjustment knob attached to a stepper motor with 60:16 pulley and belt system. It features a clutch mechanism that allows for manual focusing. The lens and the camera are held in place with mounting rings from an old 80 mm Vixen refractor. An aluminum baseplate is used to mount together as a unit the lens, camera, focuser, finder scope, and guide scope. The controller for the focuser was housed in a project box. A dovetail bar connects the whole assembly to the telescope mount.
I have tested the focuser on several imaging runs now and it appears to be working fine, especially with wide-field targets such as the Lagoon and Veil Nebula. To watch a video showing the microfocuser in action, click here.
The moon imaged with a 4 in Sky-Watcher Equinox 100ED refractor at 0.65X DIY focal reducer and an ASI 533MC camera. Registering and stacking done in SIRIL.
The moon imaged with a 4-inch telescope and an astronomy camera
For a complete list of astrophoto images, click here.
I have installed a Kenko polar scope to a Vixen Great Polaris (GP) mount. I modified the polar scope’s coupler to fit the Vixen GP mount. Instead of the standard threaded coupling, I used three screws to attach the polar scope onto the mount. A separate set of centering screws allow alignment of the star map overlay with that of the actual stars in the sky.
Kenko polar scope attached to a Vixen Great Polaris (GP) mount
A polar scope is helpful in aligning the mount’s polar axis with that of the Earth’s axis of rotation, but it lacks the precision required for astrophotography. When imaging at longer focal lengths, I recommend not relying on a polar scope, but instead use the declination drift alignment method for polar alignment. It looks at two stars, one in the eastern or western horizon, and another in the meridian near the celestial equator, allowing for better polar alignment even without the view of Polaris.
I have a 1980 Tamron 80 mm to 210 mm telephoto (zoom) lens that I intend to use for astrophotography. I could not find a dedicated astro camera adapter for this particular lens so I just improvised one. I used epoxy to connect a Tamron to Canon EOS adapter and an M42 connector for my ASI 533 astro camera.
After several imaging sessions with the Lagoon and Veil Nebula, the DIY adapter appears to work.
Veil Nebula in the constellation Cygnus imaged with an 80-210 mm Tamron telephoto lens set at 210 mm f/5.6, an ASI 533MC cooled astronomy camera, dual band H-alpha and O-III filter, with an ASI 174MM guide camera on a 30 mm f/4 guide scope. I used the StarNet++ to reduce the stars and highlight the nebula.
Lagoon M8 and Trifid Nebula M20 imaged with an 80-210 mm Tamron telephoto lens set at 210 mm f/5.6, an ASI 533MC cooled astronomy camera, dual band H-alpha and O-III filter, with an ASI 174MM guide camera on a 30 mm f/4 guide scope. This photo was imaged and tracked using a DIY go-to telescope controller.
I’ve built an electronic automatic focuser (EAF) for my Vixen R114 reflector for automated and precise focusing. The focuser was built with a geared stepper motor, A4988 stepper motor driver, and an Arduino Uno.
DIY Electronic Focuser for a Vixen R114 reflector
The focuser is ASCOM compliant and works with astronomy software such as the Nighttime Imaging N Astronomy (NINA) for automated focusing during unattended imaging. To watch a video showing the focuser’s movement, click here.
In the Philippines, the Milky Way is most prominent in the sky during months of March to May each year, visible to the unaided eye in the southeastern horizon at around 1 to 3 am.
Milky Way in Coron
Any DSLR camera or smartphone with good camera may be used to photograph the Milky Way. To capture the Milky Way:
Set the lens’ focal length to wide-field (18 mm). Milky way is a large target.
Due to Earth’s rotation, objects in the sky appear to move from east to west. Taking a long-exposure photo of stars using a camera on a non-tracking mount will produce trails. To compensate for the Earth’s rotation, a tracker as simple as a geared stepper motor can be used. This tracker is controller by a simple Arduino-based stepper controller.
Milky Way imaged with an 18 mm lens at 90 seconds exposure, with and without tracking.
Any geared stepper motor with sufficient torque can be used as a drive mechanism. For this project, I used a stepper motor with a built-in 1:500 gearbox.
Ultra-portable tracker for DSLR cameras
I simply attached an aluminum plate to the end shaft of the stepper. A ball head mount was then used to connect a DSLR to the plate. All the components can fit easily in a small camera bag. It is designed to carry only a very light payload such as a DSLR with a wide-field lens.
Component parts of the DIY portable tracker
To test it further, I also tried it with a more demanding lens: 55 mm. Without tracking, stars appear as streaks, but with tracking, stars remain as fixed points.
Milky Way imaged with a 55 mm lens at 120 seconds exposure, with and without tracking.
Even with a 55 mm lens, the tracker is capable of accurate tracking up to 120 seconds, which should be accurate enough for Milky Way shots.
Calibrating the DIY Tracker
The tracker’s ‘tracking speed’ needs to match the actual movement of the sky. Calibrate your own tracker by making sure that the stepper does not rotate a bit too fast nor too slow. Align the tracker’s axis of rotation (or what is called the polar axis, which in this case, the stepper’s main shaft) with the north star Polaris (for observers in the southern hemisphere, point the tracker’s polar axis in the general direction of the Earth’s southern polar axis). Point the camera to any bright star. Turn the tracker on and start tracking the sky. Take a series of shots (with just enough exposure to reveal the position of stars). By looking at the live view images or photos taken, you should be able to tell whether or not the tracker is moving too fast or too slow.
Polar Alignment
Before attempting this method, make sure that you have already calibrated the tracker, that is, you’ve managed to achieve a correct tracking rate. When pointed to a star in the east, minimize the north-south drift by adjusting the polar axis higher or lower (altitude adjustment). When pointed to a star in the celestial equator (near meridian), minimize the north-south drift by adjusting the polar axis to the left or to the right (azimuth adjustment). The east-west drift is corrected by adjusting the tracker’s speed.
Clock drives are simple tracking mechanism that move a telescope’s RA axis one rotation every one sidereal day (23 hours and 56 minutes) to effectively compensate for the Earth’s rotation. It allows precise tracking of planets, galaxies, nebula, and other sky targets.
Telescope clock drive controller based on L293D and Arduino Uno board
An inexpensive Arduino Uno board and L293D-based stepper motor driver can be used to control a telescope. Attach a stepper motor on a telescope’s RA adjustment knob, then find the correct motor speed that will match the movement of the sky. Below is a sample sketch for a simple telescope clock drive controller.
//Simple clock drive controller by Anthony Urbano 06 September 2021. It uses an Arduino Uno and an L293D.
#include <AFMotor.h> //Go to SKETCH > INCLUDE LIBRARY > then lookup "Adafruit Motor Shield Library"
AF_Stepper motor1RA(24, 1); //Initializing motor's steps per one full rotation; Connect the motor to M1 port
void setup()
{
}
void loop()
{
motor1RA.setSpeed(100); //Change the value to speed up or slow down the tracker
motor1RA.step(1, FORWARD, DOUBLE); //Motor takes 1 step forward; to reverse direction, replace FORWARD with BACKWARD
}
With proper polar alignment, a simple clock drive is capable of imaging deep-sky objects, such as the Flame and Horsehead Nebula. This image was taken with a telescope at 565 mm focal length.
Flame & Horsehead Nebula imaged with a telescope mount with a simple clock drive mechanism
The Celestron Travel Scope 70 has a front lens diameter of 70 mm and a focal length of 400 mm. A telescope with these specifications works well for terrestrials observations, both for daytime and nighttime.
Celestron Travel Scope 70 with modified focuser, upgraded tripod and accessories
Due to its size, however, it has a very limited use for astronomical observation. Note that the telescope showed signs of chromatic aberration, typical in low cost telescopes.
Moon imaged with a Celestron Travel Scope 70, an ASI 533 astronomy camera, and a Vixen GP tracking mountLagoon Nebula M8 imaged with a Celestron Travel Scope 70, an ASI 533 astronomy camera, and a Vixen GP tracking mount
A universal camera adapter allows any camera to be attached to a telescope or binoculars. This imaging method is called afocal imaging, in which a camera with its lens is mounted next to another image-forming optical system such as a telescope or a pair of binoculars. This adapter was built in 2008 and still in use today.
A universal camera adapter for connecting any camera with any telescope
A T-ring is a metal adapter with one end that fits on a lens mount and with the other end that connects to a T-adapter. Each camera brand has it’s own T-ring design. The T-adapter connects any T-ring to a telescope.
The Canon EOS T-ring shown in this setup is produced by Celestron, while the T-adapter was fabricated in a machine shop. Some telescopes have threaded focusers that may accept a T-ring directly, thus, eliminating the need for a T-adapter.
Over the years, I have used various types of batteries, but the one I use most often is the deep-discharge lead-acid type. They are robust, low-cost, can be charged with almost any compatible power supply, and most importantly, can double as a vehicle jump-start kit when not being used in the field. I use four 12V 9Ah deep-discharge lead acid batteries connected in parallel, to power the laptop, and another 12V 9Ah battery for the telescope’s tracker. These batteries remain usable for 2 to 3 years.
A modular field-battery to power my equipment during remote imaging sessions
A moderately-sized field battery has more than enough power to last an overnight imaging session.
I have built a DIY pier extension to allow my DIY go-to telescope to move without hitting the tripod legs. It consists of three 12-inch L-bars (which I later shortened to 7.5 inches, after measuring the minimum clearance required) that lift the tripod head. I repurposed a tripod head from an old tripod to serve as the base where the L-bars and the tripod legs connect to. The pier extension allows unattended imaging without the risk of damage to the mount or telescope.
DIY Pier Extension
To watch a video of the telescope performing a successful meridian flip without hitting the tripod legs, click here.
Omega Nebula M17 imaged with a Vixen R114 reflector, an ASI 533MC cooled astronomy camera, dual band H-alpha and O-III filter, with an ASI 174MM guide camera on a 60 mm guide scope. This is one of the brightest deep-sky objects in the Milky Way region, in the part of the sky where you can also find the Eagle Nebula. M17 is visible even with binoculars or small telescopes. You may use the bright stars of Sagittarius to find this target.
Omega Nebula M17, 40 min exposure
For a complete list of astrophoto images, click here.
Eagle Nebula M16 imaged with a Vixen R114 reflector, an ASI 533MC cooled astronomy camera, dual band H-alpha and O-III filter, with an ASI 174MM guide camera on a 60 mm guide scope. This is one of the bright deep-sky objects in the Milky Way region, in the part of the sky where you can also find the Trifid Nebula and Lagoon Nebula. You may use the bright stars of Sagittarius as pointers to find this target.
Eagle Nebula, 2 hours exposure
For a complete list of astrophoto images, click here.
Trifid Nebula M20 imaged with a Vixen R114 reflector, an ASI 533MC cooled astronomy camera, dual band H-alpha and O-III filter, with an ASI 174MM guide camera on a 60 mm f/5 guide scope. The dark dust lanes that divide the nebula into three sections are visible in this photo. This photo was imaged and tracked using a DIY go-to telescope controller.
I have built a controller for my Vixen Great Polaris mount using the OnStep go-to telescope controller. I used an Arduino Mega 2560 as the main controller board, a pair of LV8729 stepper motor driver, and an HC-05 bluetooth module (which connects to the OnStep Android app).
I also built a Smart Hand Controller (SHC) using an ESP32 module, an OLED display, and a button array. The SHC connects to the same serial communication lines (Rx and TX pins) used by the HC-05 bluetooth module. I use a toggle switch to select between the HC-05 Bluetooth module for the Android controller and the Smart Hand Controller with ESP32 module.
I used a pair of 200-step-per-revolution stepper motors paired with 60-teeth and 16-teeth pulley and belt drive system to motorize the Vixen Great Polaris mount with 144:1 worm drive. In this configuration, the total steps are 200 steps * 60/16 reduction * 144/1 teeth worm drive = 108,000 steps per 360 degrees at full stepping. Actual testing showed that accurate tracking is possible even at just 1/64 microsteps (as evident in a 60 second unguided exposures at 900 mm focal length). This brings the total steps per revolution to 6, 912, 000 per 360 degrees, or 19,200 per degree. You need to configure these values in the OnStep code.
The OnStep telescope controller can be connected to NINA to enable automatic slewing to targets and use plate-solving to validate and refine its pointing accuracy. It also connects with Stellarium to display real-time the telescope’s current position.
Unguided 60 sec exposures at 900 mm with an OnStep-controlled mount, Dumbbell Nebula (1 hour)
OnStep will have very accurate pointing and tracking even with just one-star alignment, if properly polar-aligned.
M57 Ring Nebula imaged with a Vixen R114 reflector at 1800 mm focal length (using a 2X Barlow), OIII and H-alpha dual band filter, and an ASI 533MC astronomy camera. The planetary nebula looks like a small faint circle but relatively easy to find by scanning the region between the two bright stars in Lyra.
M57 Ring Nebula, 1 hour exposure
For a complete list of astrophoto images, click here.
Night Sky in Focus 