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.
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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.
Sky-Watcher 100ED reduced from 900 mm to 565 mm focal length (from f/9 to f/5.65)
M42 Orion Nebula
DIY reducer from a Vixen telescope
Composite of actual test images, with and without DIY reducer
Center crop showing sharp details
Eastern Veil Nebula
Helix Nebula
Horsehead Nebula
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.
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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.
First-surface mirror from a DSLR
Webcam’s sensor receives light via a small 45 deg mirror
0.33″ best guiding performance
300 sec test shot at 900 mm
DIY Off-Axis Guider
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.
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.
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.
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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.
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.
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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.
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I have been using a Baader Neutral Density 5.0 Solar Safety Film filter for several years now in solar photography and visual observation. According to the specifications, it reduces solar intensity by a factor of 100,000.
The filter looks like a thin reflective plastic sheet, about A4 size (20 cm by 29 cm). When used with binoculars or telescope, it must be cut to the right size to cover the whole aperture of the optical instrument and installed securely on a rigid frame. Alternatively, the filter may be used without a telescope. Based on my experience, while the solar film may look very delicate and fragile, it is very durable and does not easily get damaged. Special attention, however, must be given to ensure that the film does not get stretched or folded to retain its properties.
Sunspot AR12192 | Sky-Watcher 4 in f/9 refractor
The Baader ND 5.0 solar filter produces sharp images with good contrast without changing the white balance. The filter I purchased in 2011 which has been used extensively in almost every solar event visible in my locality is still in excellent condition.
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I’ve built a DIY dedicated flat field panel using a repurposed LED light fixture. The flat field panel is a light source with relatively uniform brightness. The panel attaches directly onto my telescope and can be used for taking flat frames.
If a telescope with camera captures a target that is known to have a uniform brightness or illumination (such as this DIY flat field panel), the unevenness in the illumination of the field such as vignetting or presence of dusts are revealed. When a flat frame is applied to an image, any variation in brightness or illumination across the frame is leveled out, thus, vignetting and dusts are removed in the image.
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I have performed a filter modification on a Fujifilm X-A1 for a colleague. 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 Fujifilm’s X-A1’s standard (stock) filter blocks this part of the spectrum.
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I have been testing this 2-inch Celestron OIII (oxygen III) narrowband filter, which according to the specifications, isolates 496 nm and 501 nm lines emitted by planetary and emission nebula.
Celestron 93624 OIII filter
The filter looks like a polished mirror that allows some green light that corresponds to the light emitted by emission and planetary nebula to pass through but blocks everything else including most light pollution. It results in enhanced contrast between the sky and the nebula.
An OIII filter reveals an emission nebula in Milky Way’s central region
I have used this filter extensively in visual observation by “blinking” it in and out between the eye and the eyepiece, a technique used in observing emission and planetary nebula. I wanted to know if I could also use this filter to photograph OIII targets with an unmodified DSLR and a telescope and the results look good.
Veil Nebula in OIII, captured with a 4 in f/9 refractor and an unmodified DSLR, 30 minutes single exposure. Image converted to grayscale.
I am only beginning to discover narrowband imaging and I hope to use this OIII filter to photograph targets even in severely light-polluted sky.
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I’ve built an electronic automatic focuser (EAF) for my Sky-Watcher Equinox 100ED refractor for automated and precise focusing.
The focuser was built with a stepper motor from an old printer, a gearbox from an electronic screwdriver, A4988 stepper motor driver, and an Arduino Uno. It runs on the firmware developed by R. Brown (2021).
The focuser is ASCOM compliant and works with astronomy software such as the Nighttime Imaging N Astronomy (NINA) for automated focusing during unattended imaging. When the autofocus command is called, NINA takes a series of photos (with a Canon 50D DSLR) at various focus distances and measures the diameter of stars for star fields or the highest contrast for moon and planets. It then calculates the proper distance travel for best focus, and then moves the focuser to focus. An automatic focuser ensures that stars remain focused during unattended imaging runs while you are away from the telescope.
Autofocusing with a DIY Electronic Focuser
This DIY electronic focuser attached to a standard Crayford focuser features 50,000 focus positions, with buttons for manual focus adjustment and calibration. The controller keeps track of the draw tube’s current position and saves this information even when the focuser is powered off.
Precise focusing of Jupiter using an Electronic Auto-Focuser
I have tested the focuser on several imaging runs now and it appears to be working fine, especially with planets in which I image at 3600 mm focal length.
To view posts on DIY projects and astronomical equipment, click here. To get a copy of the sketch, please email eteny@nightskyinfocus.com.
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.
To view posts on DIY projects and astronomical equipment, click here. To get a copy of the sketch, please email eteny@nightskyinfocus.com.
I’ve built a wooden tripod for my Vixen 80 mm f/11 telescope on an altitude-azimuth mount. The tripod legs were built using 2 inch by 1 inch wood, with length that approximates the length of the optical tube assembly (1 meter). I’ve also built a crate that will hold the telescope and tripod as one unit, for easy transport and storage.
This is a 1990s Vixen 80 mm f/11 achromatic refractor on an altitude-azimuth mount. I cleaned the lens, repainted the optical tube assembly, and adjusted the mount. This telescope is primarily used for public stargazing events. It is easy to transport, easy to use, and well suited for viewing the moon and planets such as Jupiter and Saturn.
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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.
To view posts on DIY projects and astronomical equipment, click here. Related link: Field Battery
I repurposed my old dash camera (Polaroid N302) as a planetary camera. The lens was removed and replaced with a webcam-to-telescope adapter and then mounted on to a 4 in diameter, 900 mm focal length Sky-Watcher 100ED telescope on a tracking mount.
A pair of 2x Barlows were used to further magnify the image (3600 mm effective focal length). To watch a video about this dashcam planetary camera, click here.
I have performed filter modifications on a number of DSLR cameras 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 Canon’s standard (stock) filter blocks this part of the spectrum.
Here are sample images taken with the modified cameras. Take note of the shift in white balance (reddish hue), which is to be expected in this type of modification.
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