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

Copernicus and Montes Apenninus | August 2021

Copernicus crater and the Montes Apenninus mountain range imaged with a Sky-Watcher 4 in f/9 refractor, 25 mm eyepiece, and an ASI 533 camera.

Copernicus crater and the Montes Apenninus imaged with a 4 inch f/9 refractor

For a complete list of astrophoto images, click here.

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

DIY Declination Motor

Using a gearbox from an electronic screw driver and a stepper motor from a printer, I’ve built a declination motor drive (direct drive and using gearbox).

The electronic screw driver has a DC motor which I removed and swapped with an old printer’s stepper motor. The gearbox attaches to the declination worm screw using an improvised coupler. I designed it to feature a clutch knob to disengage the motor drive in case I need to slew manually, using the fine adjustment knob.

The stepper motor is driven with an A4988 stepper motor driver board and controlled with an Arduino Uno microcontroller. Two push buttons are used to slew the telescope north or south. I had to perform a field test in order to correctly set the motor’s speed to match the slew speed of the RA motor. The declination motor can be used for declination guiding. I have also tested it to work with a DIY go-to controller.

To watch a demo video about this DIY declination motor project, click here. To view posts on DIY projects and astronomical equipment, click here.

Related link: DIY Telescope Controller

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

Jupiter Opposition |2021

The best time to image and observe Jupiter (and Saturn or any other outer planet) is during opposition, when the planet, as viewed from Earth, is opposite the Sun (as the Sun sets in the west, the planet rises in the east), hence, the term opposition. Two conditions favorable to imaging happen during opposition: (1) Jupiter and Earth will be at their closest point in their orbits around the Sun, thus, making the planet appear largest when observed from Earth, and (2) Since the Sun is opposite Jupiter as viewed from the Earth, the planet is well-illuminated, thus, faster exposures can be taken resulting to sharper images. The Jupiter photo below was taken on August 7, two weeks before the 2021 opposition.

Jupiter imaged during the August 2021 opposition with a 4 inch f/9 refractor, 4x Barlow, and an ASI 533 camera. One of its large moon, Io, the cloud bands, and the Great Red Spot, are visible in this photo. Image processing done in SIRIL.

August is particularly rainy (and stormy) in the Philippines, and we seldom get treated with clear skies at this month.

For a complete list of astrophoto images, click here.

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

Saturn | Eyepiece Projection

In eyepiece projection, an image is projected onto the camera’s sensor using an eyepiece. In this Saturn photo, I used a 4 in f/9 refractor and a 25 mm eyepiece to project an image onto the sensor of ASI 533 astronomy camera. The magnification of the image depends on the focal length of the telescope, the focal length of the eyepiece, and separation between the eyepiece and the camera’s sensor. While longer telescopes, higher-power eyepieces, and wider separation between the eyepiece and the camera will produce more magnified images, the amount of detail that can be resolved will still depend on the aperture or the diameter of the telescope’s objective mirror or lens.

Saturn imaged through eyepiece projection during the August 2021 opposition with a 4 inch f/9 refractor, a 25 mm eyepiece, and an ASI 533 camera. Image processing done in SIRIL.

For a complete list of astrophoto images, click here.

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

Transit of Io | August 2021

The Galilean moons may sometimes cross the disc of Jupiter as viewed from the Earth in an event called a transit. This image of the moon Io transiting Jupiter was taken on August 8, 2021, from Bacoor, Cavite, using a 4-inch f/9 refracting telescope and an ASI 533 astronomy camera.

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For a complete list of astrophoto images, click here.

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

Moon | July 2021

This is probably my sharpest moon capture to date, taken with a ZWO ASI 533 camera and Sky-Watcher 100ED 4 inch f/9 refractor. This is a stack of 800 frames from a 25-second video, which I had to cut short since the file size is already 6 gig! Registered and stacked in SIRIL.

Moon imaged with an ASI 533 and a 4 inch f/9 refractor

For a complete list of astrophoto images, click here.

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

DIY Counterweights Set

Equatorial telescopes near the equator have polar axis with very low elevation and as a result, the counterweights may hit one of the tripod legs. With this new set of DIY counterweights, I was able to reposition the weights just enough distance to clear the north-side tripod leg, while at the same time, shift the weights closer to the polar axis, making the whole system more stable.

Each counterweight measures 145 mm by 16 mm, and fabricated from unused plates I’ve found in a local metals supply shop.

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

Related links:
DIY Counterweights
Kenko NES Mount

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

DIY Electronic Microfocuser

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.

The focuser is ASCOM compliant and works with astronomy software such as the Nighttime Imaging N Astronomy (NINA) for automated focusing during unattended imaging. It runs on the firmware developed by R. Brown (2021). The modification should work with any lens with built in electronic focusers. To watch a demo video about this microfocuser project, click here.

To view posts on DIY projects and astronomical equipment, click here. To get a copy of the sketch, please email eteny@nightskyinfocus.com.

Related link: DIY Electronic Automatic Focuser for Telescopes

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

Veil Nebula in Cygnus

A filter such as a dual band Oxygen III (OIII) and H-alpha filter inserted along the optical train lets the light from the nebula (and the stars) pass through, but block out everything else, particularly light pollution. This image was taken in Bacoor, Cavite in July 2021, with an ASI 533 cooled astronomy camera and a 50 mm f/4 Tamron lens (at 210 mm focal length), with 27 frames of 240 seconds sub-exposure, for a total of 1.8 hours of exposure, tracked and guided using a DIY tracker. Only light and flat frames were used in this image, no darks and bias frames. This image was stacked and processed in SIRIL.

The Veil Nebula in Cygnus

For a complete list of astrophoto images, click here.

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

DIY Antenna Rotator | DU1AU

I’ve built a DIY motorized antenna rotator using a geared DC motor, a pair of metal gears taken from a laminating machine, bearings, and a power window switch. The large gear is free to rotate and is attached to the mast with metal bearings. The antenna attaches to the large gear using a clamp. The small gear is attached directly to the geared DC motor. A metal bar attached to the mast is used to fix the drive motor in place, so that the gears mesh perfectly. The motor is powered by a 4.5V to 15V variable power supply to allow adjustment of the slew speed of the rotator. A 5-pin power window switch is used to control the clockwise and counterclockwise movement of the rotator. Paint is used to weatherproof the whole rotator assembly.

The DIY rotator is low cost and can be made with simple tools and materials. It is relatively easy to scale up using larger motors and better gear combination.

Inexpensive homebrewed antenna rotator

I have tested the rotator to carry a 3-element by 4-element VHF-UHF Yagi antenna but it should be powerful enough for larger loads such as an 8-element VHF Yagi.

To watch a video showing how I built the rotator, click here.

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

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

SSTV from the International Space Station | June 2021

The International Space Station (ISS) recently conducted a week-long radio transmissions test by sending encoded signals in Slow Scan Television (SSTV) image transmission format to be decoded by anyone with the proper amateur radio equipment tuned at 145.8 MHz and an SSTV decoder app such as Robot 36. This activity is part of the program Amateur Radio on the International Space Station or ARISS.

Certificates are given to stations who have successfully decoded SSTV images from ISS

SSTV images are sent and decoded line by line, much like how scanners and printers work. To watch a video showing an SSTV image being decoded as the ISS passes above the Philippines on June 25, 2021, 2:30 am, click here.

Related link:
Amateur Radio on the International Space Station (ARISS)
PSAT2 SSTV Images

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

The Big Dipper and Polaris

The Big Dipper is a prominent star pattern in the constellation Ursa Major. It is visible to the unaided eye and best observed in the Philippines in January to March each year. You may use the Big Dipper’s two bright stars to locate Polaris, The North Star.

For a complete list of astrophoto images, click here.

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

Albireo

Double star Albireo A (top) and B (bottom) in the constellation Cygnus, imaged with a Canon 450D DSLR and a 4 in refractor at 1800 mm focal length (f/18). Note the striking color contrast between the two stars.

For a complete list of astrophoto images, click here.

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

California Nebula NGC 1499

NGC 1499 California Nebula imaged with a 50 mm f/1.8 lens and a Canon 450D DSLR on a motorized mount with DIY controller. This photo is a stack of 12 frames at 20 seconds sub-exposure, for a total of 4 minutes, processed in SIRIL.

For a complete list of astrophoto images, click here.

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

M31 Andromeda Galaxy

M31 Andromeda Galaxy, imaged with a 50 mm f/1.8 lens and a Canon 450D DSLR on a motorized mount with DIY controller. This photo is a stack of 12 frames at 30 seconds sub-exposure, for a total of 6 minutes, processed in SIRIL.

For a complete list of astrophoto images, click here.

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

DIY Equatorial Wedge

I have fabricated a customized equatorial wedge for a colleague. An equatorial wedge is simply a platform that is tilted to precisely match the latitude of a place. When used with a wedge, an altitude-azimuth telescope mount may be used in equatorial configuration.

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

DIY Counterweight

I have fabricated an additional counterweight for my equatorial mount. It did not cost much since it was made from repurposed iron weight and was relatively easy to make.

Do not go beyond the mount’s maximum payload capacity when adding new equipment along with the corresponding counterweight.

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

Related link:
DIY Counterweights Set
Kenko NES Mount

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