DIY Rotator with 4-element Yagi

I’ve recently finished building a DIY rotator with 4-element dipole Yagi antenna tuned at 145 MHz VHF.

DIY Rotator by DU1AU

The rotator consists of a worm drive in which a worm from an old copier machine meshes with a wheel from an old drill. The shaft is a stainless steel rod that is held in place by two pillow block bearings. The whole assembly is housed in a waterproof metal ammo box. It has an oil ring gasket to seal the hole at the bottom where the shaft goes through. The screws used to mount the pillow blocks are stainless steel to resist corrosion, with rubber gaskets to prevent water entry. The rotator uses a 12V geared DC motor to drive the worm gear. With the current load, it consumes only 200 mA when slewing. The rotator was tested to carry a VHf Yagi with up to 7 elements. It takes 10 seconds to slew the antenna from north to south.

DIY 4-element Yagi mounted on a DIY rotator

In the next iteration of this project, I will increase the separation between the antenna and the metal box enclosure to minimize the effect to the radiation pattern of the antenna.

RX preamp and TX amplifier installed in the rotator’s weatherproof box

I’ve also installed a Tokyo Hy-Power HL-726D 50-watt TX amplifier and 12-14 dB gain RX preamp, which helps in receiving weak signals (when placed near the antenna) and allows my radio to operate at a lower power level since only 5-25W is needed to drive the amplifier. During initial tests (no RX preamp and TX amplifier used), the antenna worked with excellent transmit and receive signals as reported (and video recorded) by DW3QEA, a net control station in Nueva Ecija, over 120 km distance from my location in Bacoor.

Elevation motor added recently to the rotator for satellite tracking

To watch a video about this homebrewed rotator, click here.

Related links:
DIY Satellite Tracker | SARCNET
DIY Satellite Tracker | SATNOGS

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Canon 700D and 1200D Modification

I have modified two DSLR cameras for my colleagues, for astrophotography use. It involves the removal of the stock UV-IR filter, making the camera more sensitive to H-alpha wavelengths, as Canon’s standard (stock) filter blocks this part of the spectrum.

To view posts on DIY projects and astronomical equipment, click here.

Related link:
View posts on camera modification projects

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

NOAA 19 Satellite | October 2021


NOAA 19 satellite image of tropical storm Maring (Kompasu) received with an inexpensive amateur radio equipment on October 11, 2021 with an AirSpy Mini SDR on GQRX SDR app and a DIY satellite antenna. The signal was recorded in WAV sound format and then decoded (converted to image) with the NOAA-APT decoder. NOAA satellites (15, 18, and 19) transmit weather images in APT (Automatic Picture Transmission) format at 137 MHz which may be received using just a VHF antenna, a software-defined radio (SDR), and an APT decoder.

NOAA 19 satellite image of tropical storm Maring (Kompasu) received with an inexpensive amateur radio equipment

Related link: Tracking Typhoons with NOAA Satellites

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Orion Nebula M42 | October 2021

Orion Nebula M42 imaged with an ASI 533 cooled astronomy camera, a ZWO dual-band filter, and a 210 mm focal length f/4 Tamron lens, for a total of 19 minutes exposure. Tracked and guided using an ASI 174 guide camera and DIY tracker. This image was stacked and processed in SIRIL.

Orion Nebula M42

For a complete list of astrophoto images, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Andromeda Galaxy M31 | September 2021

Andromeda Galaxy M31 imaged in September 2021 with a Celestron Travel Scope 70, UV-IR cut filter, and an ASI 533 astronomy camera, guided with a DIY off-axis guider (OAG) and an ASI 174MM guide camera. A total of 25 minutes exposure stacked and processed in SIRIL without calibration frames.

Andromeda Galaxy M31

For a complete list of astrophoto images, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Pleiades M45 | September 2021

Pleiades M45 imaged in September 2021 with a Celestron Travel Scope 70 , UV-IR cut filter, and an ASI 533 astronomy camera, guided with a DIY off-axis guider (OAG) and an ASI 174MM guide camera. A total of 10 minutes exposure stacked and processed in SIRIL without calibration frames.

Pleiades M45

For a complete list of astrophoto images, click here.

Related link: Eastern Veil Nebula

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Triangulum Galaxy M33 | September 2021

Triangulum Galaxy M33 imaged in September 2021 with a Sky-Watcher Equinox 100ED, UV-IR cut filter, and an ASI 533 astronomy camera at 565 mm focal length (using a 0.63x DIY focal reducer, guided with a DIY off-axis guider (OAG) and an ASI 174MM guide camera. A total of 10 minutes exposure stacked and processed in SIRIL without calibration frames.

Triangulum Galaxy M33

For a complete list of astrophoto images, click here.

Related link: Eastern Veil Nebula

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Lagoon Nebula M8 | September 2021

Lagoon Nebula M8 imaged in September 2021 with a Sky-Watcher Equinox 100ED, UV-IR cut filter, and an ASI 533 astronomy camera at 565 mm focal length (using a 0.63x DIY focal reducer, guided with a DIY off-axis guider (OAG) and an ASI 174MM guide camera. A total of 20 minutes exposure stacked and processed in SIRIL without calibration frames.

Lagoon Nebula M8 in Sagittarius

For a complete list of astrophoto images, click here.

Related link: Eastern Veil Nebula

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Trifid Nebula M20 | September 2021

Trifid Nebula M20 imaged in September 2021 with a Sky-Watcher Equinox 100ED, UV-IR cut filter, and an ASI 533 astronomy camera at 565 mm focal length (using a 0.63x DIY focal reducer, guided with a DIY off-axis guider (OAG) and an ASI 174MM guide camera. A total of 30 minutes exposure stacked and processed in SIRIL without calibration frames.

Trifid Nebula M20 in Sagittarius

For a complete list of astrophoto images, click here.

Related link: Eastern Veil Nebula

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Sun | September 2021

Sun imaged with a 4 inch f/5.65 refractor, a Baader ND 5.0 solar filter, UV-IR cut filter, and an ASI 533 camera.

Active regions AR2871 (lower center), AR2872 (center left), and AR 2873 (upper right) are visible in this image.

For a complete list of astrophoto images, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Moon | September 2021

After having recently modified my telescope by installing a DIY 0.63x focal reducer, which involves cutting the optical tube assembly and reattaching the focuser, I took a test shot with the moon to determine if the optical elements are properly aligned (collimated) and whether or not the reducer lens introduces color (chromatic) aberration. The image appears sharp, and I did not notice any chromatic aberration (no chromatic aberration reduction applied on this image, not even RGB alignment). To further check proper collimation, I will need to perform a star test soon.

Moon | September 2021

For a complete list of astrophoto images, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Horsehead Nebula| September 2021

The Horsehead Nebula (IC 434) imaged in September 2021 with a Sky-Watcher Equinox 100ED, ZWO duo nebula filter, and an ASI 533 astronomy camera at 565 mm focal length (using a 0.63x DIY focal reducer, guided with a DIY off-axis guider (OAG) and an ASI 174MM guide camera. A total of 20 minutes exposure stacked and processed in SIRIL without calibration frames.

The Horsehead Nebula in Orion

For a complete list of astrophoto images, click here.

Related link: Eastern Veil Nebula

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Helix Nebula | September 2021

Helix Nebula imaged in September 2021 with a Sky-Watcher Equinox 100ED, ZWO duo nebula filter, and an ASI 533 astronomy camera at 565 mm focal length (using a 0.63x DIY focal reducer, guided with a DIY off-axis guider (OAG) and an ASI 174MM guide camera. A total of 38 minutes exposure stacked and processed in SIRIL without calibration frames.

Helix Nebula

For a complete list of astrophoto images, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Eastern Veil Nebula | September 2021

First light image of a DIY off-axis guider OAG fitted to a Sky-Watcher Equinox 100ED using an ASI 174MM as a guide camera, imaging at 565 mm focal length (0.63x DIY focal reducer). This image was taken in September 2021 with an ASI 533 cooled astronomy camera and a ZWO duo nebula filter, for a total of 2.4 hours. Stacked and processed in SIRIL without calibration frames.

The Eastern Veil Nebula (Caldwell 33), a supernova remnant in Cygnus

For a complete list of astrophoto images, click here.

Related link: Western Veil Nebula

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Transit of Europa, Ganymede, and Callisto| August 2021

When you look at Jupiter through a telescope, you usually see four moons lined up with the planet. From time to time, a moon may pass in front of Jupiter’s disc in an event called a transit. A transit is a rare event since it occurs only when at least one moon lines up with Earth and Jupiter. On August 15, 2021, however, three of Jupiter’s four largest moons—Europa, Ganymede, and Callisto—passed in front of Jupiter, a very rare event which I have observed and captured using a small telescope.

Three of Jupiter’s four largest moons passed in front of Jupiter on August 15, 2021 (Legend: 1-Europa, 2-Europa’s shadow, 3-Ganymede, 4-Ganymede’s shadow, 5-Callisto, 6-Io). Image taken with a 4 inch f/9 refractor and an ASI533 camera, Philippines.

Related link: View all posts about transit
For a complete list of astrophoto images, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Clavius Crater | August 2021

Clavius crater imaged with a Sky-Watcher 4 in f/9 refractor, 25 mm eyepiece, and an ASI 533 camera. Registering and stacking done in SIRIL.

Clavius crater imaged with a 4-inch telescope and an astronomy camera

For a complete list of astrophoto images, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

DIY Projector Lens Telescope

Projectors have lenses that may be used to build low-magnification telescopes. I happen to have found an old 70 mm diameter LCD projector lens with focal length of 105-210 mm which I paired up with an eyepiece to build a DIY telescope.

This projector lens, while not designed to be used as a telescope lens, may still provide good views. I measured the proper focus distance and used a DIY adapter to attach a 2-in diagonal mirror and a 40 mm lens to it. This combination produced a 2.6 by 70 to 5.25 by 70 finder scope (wide field of view with ability to zoom). Focusing is done by sliding the eyepiece in and out of the diagonal’s eyepiece holder. I then made an improvised reticle (cross hair) to finally complete the setup. I will be using this DIY projector lens telescope in star-hopping to deep-sky targets and scanning large areas of the sky.

To view posts on DIY projects and astronomical equipment, click here.

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

Western Veil Nebula | September 2021

First light image of a DIY 0.63x focal reducer fitted to a Sky-Watcher Equinox 100ED. This image was taken in September 2021 with an ASI 533 cooled astronomy camera and a ZWO duo nebula filter, for a total of 14 minutes, tracked and unguided. Stacked and processed in SIRIL without calibration frames.

The Western Veil Nebula in Cygnus, a supernova remnant


For a complete list of astrophoto images, click here.

Related link: Veil Nebula (wide-field)

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

DIY Focal Reducer

I have built a DIY focal length reducer (focal reducer) by inserting a converging lens from an old telescope along the optical system of a Sky-Watcher Equinox 100ED . The telescope’s native focal length is 900 mm at f/9. With the DIY reducer, the focal length is reduced to 565 mm at f/5.65 (actual focal length as measured by SIRIL’s plate solver function). The lens used was the objective of a Vixen 80 mm f/11 achromat, reducing the native focal length of my telescope by 0.63x.

Focal reducers are optical elements (usually a convex lens or lens group) that converge light from a telescope’s objective. It shortens the focal length and in effect, produces a faster telescope (lower f/ratio) and widens the field of view (larger portion of the sky is seen or captured). Any decent quality converging lens should work as a focal reducer. It works opposite to a Barlow lens which increases the focal length by using a concave lens or diverging lens. Unlike dedicated focal reducers designed to maintain optimal image quality, DIY focal reducers may introduce aberration and must be considered when attempting this modification.

I had to shorten the optical tube by about 200 mm to reach focus, and then reattach the focuser. To see how long the telescope is prior to the modification, click here. The focuser’s draw tube was also shortened by 55 mm to prevent it from obstructing the light and stopping down the objective lens when moved inward. The telescope’s optical tube has an inner diameter of about 100 mm which has enough space to accommodate the lens cell of the Vixen 80 mm lens. Only the central 60 mm part of the reducer is used due to the presence of a light baffle in the telescope’s optical tube assembly.

To view posts on DIY projects and astronomical equipment, click here.

Related link:
Sky-Watcher Equinox 100ED (100 mm f/9 )
Vixen Achromat (80 mm f/11)

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines

DIY Off-Axis Guider (OAG)

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. The critical component in this DIY is a high-quality mirror, which 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 (webcam) in or out to achieve focus.

I have tested the off-axis guider to work with the SPC900NC web camera, Kenko NES mount, Sky-Watcher Equinox 100ED, and an ASI 533, with best guiding performance at 0.33″ (arcseconds) at 900 mm focal length. I tried using the ASI 533 as a guide camera and found out that the mirror fully illuminates the full width of the sensor, which means a dedicated OAG camera with large sensor (such as those using the Sony IMX 174 sensor) should be fully-illuminated as well.

To watch a video showing this DIY off-axis guider, click here. To view posts on DIY projects and astronomical equipment, click here.

Related link: Kenko NES Mount

Night Sky in Focus | Astronomy and Amateur Radio
© Anthony Urbano | Manila, Philippines