A DIY Amplifying Eyepiece for Astrophotography

When it comes to observing nebulae, galaxiesand other deep space objects, amateur astronomers on a budget had two options. They can see with the naked eye through telescope and perceive these impressive objects as faint blobs that don't even convey their grandeur, or they may take long exposure photos astrocameras and display the results on a viewing screen or computer, making it impossible to directly observe the stars.

Self-contained active light enhancement telescope eyepieces exist for real-time viewing, but commercial products are expensive and cost hundreds to thousands of dollars. I needed something that I could use for the public astronomy observation nights that I host in my community. So I decided to build an inexpensive one DIY an amplifier eyepiece to make it easier for visitors to observe deep space objects, but without requiring a large financial investment on my part.

I quickly realized that there was already an industry rife with low-light equipment: the security camera industry. Faced with the problem of monitoring areas with different lighting, often using cameras scattered throughout a large facility, closed loop system manufacturers TV (CCTV) cameras have created a video standard that uses digital sensors to capture images and then transmits them as HD analog signals over coaxial cables. Using this Analog High Definition (AHD) standardyou can connect new cameras to existing long cables and still get high-quality images.

CMOS image sensor module from CCTV camera [top left]A USB capture card [bottom left]And OLED viewfinder [right] process analog video data.James Provost

While I didn't need the long-range capability of these cameras, I was very interested in their low price and ability to work in low light conditions. The business part of these cameras is a module that combines CMOS image sensor with supporting electronics. After some research I settled on module which combined a 2 megapixel Sony IMX307 sensor with support Chipset NVP2441.

The key factor was choosing a sensor and chipset combination that supports something called Starlight or Sensitivity mode. This makes the camera more sensitive to light than the human eye, although at the cost of a slight reduction in speed. Images are created by integrating the exposure time at the sensor into approximately 1.2 seconds. This can result in choppy footage from CCTV cameras, but it is not noticeable when observing nebulae and other astronomical objects (unless something is wrong, of course). Really strange things are happening in the sky!)

From Astronomy To and from surveillance cameras

The existence of Sens-up mode is actually part of the technical heritage digital image sensors CMOS there were sensors designed as successor to charge-coupled devices (CCDs), which have been eagerly awaited accepted by the astronomical community after their introduction in 1970, replacing long-exposure photographic plates. However, the ability to capture one-second exposures is rarely what security cameras are designed for: it can be more of a disadvantage than a feature, resulting in blurry images of moving objects or people.

As a result, this feature is rarely mentioned in product descriptions, so finding the right module was the hardest part: I had to buy three different camera modules before finally settling on one that worked.

The camera module output signal is sent to digital viewfinderwhich displays the video menu and control menu created by the module. These menus are navigated using a four-way selectable joystick that connects to a dedicated header on the module.

The camera output is also sent to capture card which converts analog signal to digital and provides a USB-C interface that allows you to view and save images using a smartphone. All electronics can be powered by a battery for complete autonomous operation or from the mains. USB cable connected to the capture card.

The analog HD module can be controlled directly using the joystick to navigate through the on-screen menus. Power can be supplied externally via the USB-C connector on the capture card or via an optional battery.James Provost

The components fit into a housing I made from 3D printed parts that fits the diameter of most 32mm telescope eyepieces, making installation easy. All of this cost less than $250.

Checking the intensifying eyepiece

I took out my new eyepiece amplifier along with Celestron C11 telescope to try. The Dumbbell Nebula, also known as Messier 27/M27, which is usually quite difficult to see, soon appeared in the viewfinder. It was significantly brighter compared to observation with the naked eye. Of course, the difference was not as noticeable as in the case of a commercial installation equipped with noise-reducing cooling for the sensor electronics. But it was still a huge improvement and at a fraction of the cost.

Orion A nebula located at a distance of about 1340 light years from us.Jordan Blanchard

The amplifier is also more versatile: it can be removed from the telescope, and with a 2.8mm HD lens mounted on the camera module's sensor, it can be used as a night vision camera. This comes in handy when working in the dark outdoors on starry nights!

In the future, I would like to upgrade the USB-C capture module to one that can directly process the sensor's digital output, rather than just the analog signal. This will give a noticeable increase in resolution when recording or streaming to your phone or computer. In addition, I am interested in finding another low-cost camera module with a longer shutter speed and improving the 3D printed housing so that it is easier to build and adapt to other observing setups. This way the eyepiece will remain affordable, but people will still be able to push it into more serious electronically assisted astronomy.