Hubble Optics Artificial Collimation Star Reviewed

Periodic collimation is critical for the best optical performance. But clear nights are for observing, while telescope maintenance is a cloudy night activity. Unfortunately, the all-important star collimation isn’t something you can do when it’s cloudy.

Collimation lasers are great for getting telescope optics close to their best alignment, but for peak optical performance, a star test is needed for the final collimation tweaks, such as centering the Airy disk in the star’s diffraction pattern. For this crucial final step, both clear sky and good seeing are necessary, but commodities often in short supply.

The Hubble Optics artificial star is a 5-LED flashlight with an aperture mask instead of a standard flashlight clear lens. Credit: Robert Reeves

The Hubble Optics artificial star is an effective, simple, and inexpensive solution for performing periodic star collimation without the need for clear night sky and excellent seeing conditions. Additionally, collimating with the Hubble optics artificial star does not require a telescope drive to track a moving star in the sky. This simplifies “chasing the star” as it moves within the eyepiece view with each collimation adjustment.

For years, amateur astronomers and telescope makers have created artificial stars by piercing aluminum foil with a pin and shining a flashlight through the small aperture. While this seemingly creates an effective artificial star, the optical reality is that the pinhole size must be based on the telescope aperture and its distance from the telescope. The Hubble Optics artificial star solves the imprecise pinhole dilemma by providing five precision pinholes, measuring 50, 100, 150, 200, and 250 microns in size, in the artificial star’s opaque mask.

The key to the usefulness of the Hubble Optics artificial star is the precision 50, 100-, 150-, 200-, and 250-micron mask apertures. Credit: Robert Reeves

The Hubble Optics artificial star does not come with any instructions. Determining the proper pinhole size and test distance from the telescope can be roughly determined by selecting the smallest pinhole that provides a clear and well-defined out-of-focus star image in the telescope. Or you can use the mathematical formula for the optimum star-to-telescope distance on the Hubble Optics FAQ website.

For the non-mathematical pinhole and distance selections, a rule of thumb can be applied. Most telescopes utilizing the artificial star test will be in the 5- to 14-inch aperture range. For the 50-micron artificial star, the star-to-telescope distance is slightly less in meters than the telescope aperture in centimeters. For example, with the popular 8-inch SCT’s 20-centimeter aperture, the telescope should be about 17 meters from the 50-micron artificial star. Similarly, for an 11-inch SCT (28 centimeters) the distance should be about 24 meters, and for a 14-inch (35.6 centimeters) the distance would be 30 meters. For 5- to 8-inch aperture telescopes, an average home with a long hallway will allow indoor use of the Hubble Optics artificial star.

The Hubble Optics artificial star is easily mounted on a tripod with rubber bands. Credit: Robert Reeves

The Hubble artificial star is basically a small AAA battery-powered five-LED flashlight. But what you are paying for is the precision size of the artificial star pinholes overlaying the light source. These known pinhole sizes allow for maximizing the effectiveness of the artificial star in collimating your telescope. If needed, the intensity of the pinhole illumination can be varied somewhat by rotating the front barrel to offset the pinholes from the LED under them. A supplied small magnet is sized to cover four of the pinholes, allowing only the desired size artificial star to shine through.

The Hubble artificial star is simple to use; strap it to a camera tripod with rubber bands, turn it on with its push-button switch, and aim it at the telescope. Of course, stable thermal conditions are needed. An expanse of hot driveway will hamper fine collimation tuning. The Texas heat forced my testing indoors. I quickly found out how temperature-sensitive the artificial star is. Even down a long indoor hallway, the central air conditioner had to be shut off for at least 10 minutes before the interior air was stable enough to sufficiently resolve the tiniest Airy disk.

The proper pinhole aperture is chosen by selecting the dimmest aperture that can be clearly seen. Credit: Robert Reeves

While the typical SCT concentric out-of-focus “doughnut” star image is easy to achieve, seeing conditions often prevent the high-magnification centering of the Airy disk within the star’s diffraction pattern for greatest precision. This is where the Hubble artificial star shines brightest. By examining the Airy disk at high magnification under controlled circumstances, you can make the final high precision collimation tweaks necessary to get maximum performance from your telescope.

When the Hubble Optics artificial star is used under controlled conditions, tiny Airy disks can be seen that aren’t visible with real stars under poor seeing conditions. Credit: Robert Reeves

A word of warning: store the Hubble Optics artificial star in a plastic Ziplock bag. The effectiveness of the tiny 50- and 100-micron apertures will be compromised if dust or debris clogs the tiny openings. Also, do not store the artificial star with the occulting magnet on the pinhole mask. Over time, magnet particles will flake off and accumulate in the pinhole apertures.

In a nutshell, I am impressed by the usefulness of a simple device like the Hubble Optics artificial star. After almost 60 years of telescope use, I wish I had one much earlier!

Plus:       Inexpensive, reliable, easy to use

Minus:   Utilitarian plastic construction, easy to cross-thread components on battery installation

                Thermal stability is needed over the entire star-to-telescope test distance 


MSRP: $27



About Robert Reeves

Robert Reeves has been exploring the Moon since 1958 and took his first lunar photograph in 1959. He began telescopic astronomy with a four-inch Criterion Dynascope. Today, Reeves uses a Celestron 11 Edge HD, a Sky-Watcher 180mm Maksutov, and a Sky-Watcher 20-inch Stargate Dobsonian for lunar photography, and a Celestron C-14 with a Hyperstar for deep-sky photography from his Perspective Observatory located in central Texas. Robert has published over 250 magazine articles and 200 newspaper columns about astronomy and has authored several books, including The Superpower Space Race, The Conquest of Space (co-authored with Fritz Bronner), Wide-Field Astrophotography, Introduction to Digital Astrophophotography and, most recently, Introduction to Webcam Astrophotography. Although Robert Reeves is an accomplished deep sky astrophotographer, his current passion is re-popularizing the Moon with the public and the amateur astronomy community. He enjoys speaking to astronomy conventions and spreading his passion for the Moon.

Related posts