Astronomical Equipment – Night Sky in Focus

DIY Battery Grip for Pentax KP

I have fitted my Pentax KP with a Neewer BG-E8 battery grip (intended for Canon cameras). While I also have the dedicated Pentax D-BG7 grip, I have made this modification to explore alternative battery options for the Pentax KP. In this modification, some filing is needed to flatten out the curved surfaces to flush the camera nicely to the grip. A new hole was then drilled in the grip since the tripod shoe locking screw was not aligned. A dummy battery was then used to connect the power to the camera. The grip’s buttons are non-functional since I have yet to figure out and map the proper connections!

I have tested my Pentax KP to work with various power supplies ranging from 7.2V to 8.4V. For instance, it was tested to work with 6 NiMH AA batteries in series at 1.2V each, it works with a Fujifilm 7.2V NPW126S batteries, it works with Canon CA PS700 7.4V power adapter, and even works with two 3.6V to 4.2V 18650 cells in series.

Alternative battery option for Pentax KP

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Autofocus for a Celestron 8 inch SCT

I wanted to test if it is possible to tap onto a DSLR lens’ autofocus system and use it to move the focusing knob of a telescope. I happen to have an old Pentax kit lens that works with the Pentax Screw Drive focusing system. It uses a motor in the DSLR body which is connected to the lens through some mechanical linkage. I have removed the lens elements of the kit lens and used improvised adapters to attach it to a Celestron 8 inch telescope. I then used a belts and pulleys to link the moving part of the lens with that of the focusing knob of the telescope. It did a few tests and it appears to work on some of the targets, like distant towers and the moon.

DIY Autofocuser for Celestron C8 using the Pentax Screw Drive focusing system

To view how I used a Pentax kit lens to add autofocus capabilities to my telescope, click here.

DIY Carrying Handle for Telescopes

I have used door handles to serve as my telescope’s carrying handle. A carrying handle allows for easy transport of a telescope, especially for mobile setups that need to be assembled and disassembled with each imaging session.

The carrying handle was attached directly to the mounting rings, secured with two screws flushed underneath.

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

Bathinov Mask

A Bathinov mask is a focusing tool for checking precise focus by observing the diffraction pattern formed around stars. Placing the mask in front of a telescope’s objective produces spikes: a perfectly focused star shows symmetrical pattern in contrast to an asymmetrical pattern produced by an unfocused star.

A Bathinov mask for a 4 inch refractor. When not in use, the mask is placed inside the lens cover.

Ideally, the mask should cover the whole aperture of the telescope. Recently, however, I’ve successfully used an undersized mask for a larger telescope. A Bathinov mask allows you to evaluate whether precise focus has been achieved.

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Clip-In Filter for DSLR

I have built a DIY clip-in filter holder for use with my DSLR. I used a spare T2 to 1.25 inch adapter supplied with my astronomy camera. I noticed that my Canon 50D has space to accommodate this adapter. I then drilled a small hole in the camera and used a small screw to fasten the DIY clip-in filter in place.

DIY clip-in filter for DSLR

The clip-in filter works best with modified DSLR cameras with the stock filter removed. It can be used to mount 1.25 inch filters such as a dual band filter and a UV-IR filter. I have also made a clip-in stock filter so I could still use the modified DSLR for daytime photography.

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

Off-Axis Guider | Askar

An off-axis guider (OAG) is particularly useful for my imaging setup since my telescope is an 8 inch Celestron SCT. SCTs focus by moving the main mirror, thus, susceptible to mirror shift as it tracks the sky. Since OAGs receive light directly from the main mirror, it can account for any mirror shift.

AOG setup by Askar for my 8 inch SCT, with ASI 174MM as guide camera and ASI 533MC as the imaging camera

I tried to minimize the components by removing the supplied helical focuser (focusing is done by sliding the guide camera instead). The OAG is placed before the filter drawer. Here’s a sample photo of M51 Galaxy imaged with a setup using the OAG at 1140 mm, f/5.7 (with a DIY reducer). To view other photos taken with this OAG, click here.

DIY Meade LXD75 OnStep Conversion

The original controller of this Meade LXD75 mount has failed and a DIY OnStep controller was used to repair the mount and restore its tracking and go-to capability. I have installed RA and declination motors and used an Arduino microcontroller to control the motors. Just like the mounts typical of this class and era, it has a 144:1 main shaft gear reduction, and looks very similar to the Vixen Great Polaris mount. It takes 144 full rotations of the worm to rotate the RA or declination shaft 360 degrees.

I used NEMA 17 stepper motors on an L-brackets with 16-teeth and 60-teeth pulley and belt drive system for each axis. The total steps are 200 steps * 60/16 reduction * 144/1 teeth worm drive with 1/64 micro-stepping, at 6, 912, 000 per 360 degrees, or 19,200 per degree.

The mount uses 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). It is powered by a 12V 12A power supply. To watch a video of this Meade LDX75 OnStep conversion during testing, click here.

Related link:
DIY Controller for Vixen Great Polaris Mount

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Pier Extension

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.

To watch a video of the telescope performing a successful meridian flip without hitting the tripod legs, click here.

Related link: Converting the Vixen Great Polaris mount into a Go-to mount

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Controller for Vixen Great Polaris

I have built an OnStep go-to telescope controller for a Vixen Great Polaris mount. 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.

OnStep will have very accurate pointing and tracking even with just one-star alignment, if properly polar-aligned.

Related link: Meade LXD75 OnStep Upgrade

Night Sky in Focus 
© Anthony Urbano | Bacoor, 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.

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Focal Reducer

Focal reducers are optical elements (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 imaged). Any decent quality objective lens from an achromat telescope or a finder scope could work as a focal reducer. DIY focal reducers may introduce aberration (coma) and must be considered when attempting this modification.

Using a Vixen 90 mm Objective Achromatic Lens

I have built a DIY focal length reducer (focal reducer) by inserting an objective lens from a 90 mm Vixen achromat along the optical system of a Sky-Watcher Equinox 100ED . The telescope’s native focal length is 900 mm at f/9. Using the objective lens of a Vixen 90 mm f/14 achromat, the focal length of the Sky-Watcher Equinox 100ED is reduced to 557 mm at f/5.57. To reach focus, I had to shorten the optical tube to about 55 mm. The focuser’s draw tube was also shortened to prevent it from obstructing the light and stopping down the objective lens when the draw tube moves inward. Varying the distance between the main lens and the reducer lens affects the resulting effective focal length. From 2020 to 2024, I have tried placing the DIY reducer at various distances until I finally found one configuration that produces stars with acceptable sharpness. To view a sample photo with a DIY reducer using a Vixen 90 mm achromat objective lens, click here.

DIY focal reducer using an objective lens from an achromat refractor with an improvised lens cell

Using a Threekor 40 mm or 50 mm Finder Scope Lens

Finder scope lenses can also be used a reducers. I have used the objective lens of a 40 mm Threekor finder scope as DIY reducer for my 8 inch Celestron SCT. I just removed the finder scope’s lens and then placed it at the threaded end of the 8 inch SCT, where you would attach a visual back adapter. I used a spare tube extender (I use M42 spacers) to mount the lens and insert it into the optical path. Upon testing, it reduced the focal length from 2000 mm to 1140 mm. I have also successfully used a 50 mm finder scope achromat lens as a DIY reducer. To view a sample photo with a DIY reducer using a 40 mm finder scope achromat objective lens, click here.

DIY focal reducer using a finder scope lens attached to a tube extender using super glue

Night Sky in Focus 
© Anthony Urbano | Bacoor, 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. 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.

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 use the improvised OAG, focus the main camera first, and then slide the guide camera in or out to achieve focus.

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

Baader ND 5.0 Solar Filter

I have been using a Baader Neutral Density (ND) 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 Baader ND 5.0 solar filter produces sharp images with good contrast without changing the white balance.

Baader film solar filter mounted on a telescope

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. 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.

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

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Electronic Focuser

I have built a few electronic focusers for various telescopes. Here are some of the focusers built with stepper motors, stepper drivers, and an Arduino Uno microcontroller. These focusers work with astronomy software such as the Nighttime Imaging N Astronomy (NINA). When the autofocus command is called, NINA takes a series of photos at various focus distances and then 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 that position. An automatic focuser ensures that stars remain focused during unattended imaging runs while you are away from the telescope.

This DIY electronic focuser attached to a standard Crayford focuser. The controller keeps track of the draw tube’s current position and saves this information even when the focuser is powered off.

Here is an electronic focuser for a Vixen R114 reflector for automated and precise focusing.

DIY microfocuser for a telephoto lens using a Vixen’s alt-az mount azimuth lock mechanism

DIY electronic focuser for an 8 inch SCT using a motor drive from a Vixen Super Polaris mount

DIY Autofocuser for Celestron C8 using the Pentax Screw Drive focusing system. To view how I used a Pentax kit lens to add autofocus capabilities to my telescope, click here.

Electronic focusers can be quite useful especially in unattended automatic focusing. There are instances, however, when I would still prefer a mechanical non-electronic focusing, since electronic focusers tend to be slow, and it requires power. In all these DIY focusers, I have always included a clutch mechanism, to disengage the electronic focuser and still allow manual focusing.

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Intervalometer

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.

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Battery Adapter for DSLR

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.

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Planetary Camera

By attaching a webcam or a dash cam to a telescope using a special type of adapter, it is possible to take up-close photos of planets.

Web Camera | Replace the webcam’s lens by a special type of adapter called a webcam-to-telescope adapter. Insert the webcam with an adapter into the eyepiece barrel of the telescope’s focuser.

SPC900NC webcam attaches to a telescope with webcam-to-telescope adapter

Dash Camera | I repurposed my old dash camera as a planetary camera. The lens was removed and replaced with a webcam-to-telescope adapter and then mounted on to a telescope.

Polaroid N302 dash camera repurposed for planetary imaging

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

Pentax Binoculars

This is a Pentax 10 by 50 S-series waterproof binoculars for terrestrial and astronomical use. It features high quality multi-coated optics, waterproof build, multi-coated lens, internal focusing mechanism with focus lock, diopter adjustment to accommodate variations in focusing of the eyes, and equipped with socket for mounting with a tripod.

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

Telescope Travel Cases

Here are some of the hard travel cases I use in moving my telescope and its accessories, especially when travelling to remote observing sites. These are repurposed standard cases for audio equipment. The dimensions in length, width, and height are within the allowable limit for local air travel.

Modified Sky-Watcher Equinox 100ED on an improvised telescope hard case. I’ve customized the foam paddings using improvised nichrome hot-wire cutter. I also use egg crate shaped foam paddings from a local foam supplier. Recently, we went to a dark sky site with these hard cases protecting the telescope.

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

Night Sky in Focus 
© Anthony Urbano | Bacoor, Philippines

DIY Smartphone-to-Telescope Adapter

Smartphones can be used to image the moon by holding it next to the eyepiece of a telescope. For smart phone cameras, a mid-power eyepiece such as a 25 mm eyepiece yields good results. 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. An inexpensive smartphone-to-telescope may be built using inexpensive materials using a piece of plywood, hose clamp, screw, and rubber bands. Secure the hose clamp onto the plywood using screws. Use the hose clamp to hold the eyepiece in place. Use rubber bands to hold the smart phone camera and adjust as necessary.

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