Hubble 5-Star Artificial Star FAQ - Star Testing and Collimation

Q: How should the 5-star be aimed and positioned relative to the telescope?

Place the 5-star on a tripod top, table, or other stable surface, aim it roughly toward the telescope, and then point the telescope at the artificial star for normal focusing. Precision aiming is not required because the illuminated stars have a wide viewing angle.

Q: What distance should be used for placing the artificial star?

For a full star test, place it as far away as practical. A common estimate is M = 336 * D / F^3, then Distance = M * focal length, with additional guidance that SCTs may require roughly M = 20 or more for true star testing.

Q: What is the collimation workflow using the 5-star?

First do rough collimation with a strongly defocused view until about 10 rings are visible and the rings and central shadow are concentric, then adjust collimation per the telescope manufacturer. Finish with fine collimation by observing the focused 50 micron star image and Airy disk around 50x per inch of aperture, making small adjustments until the diffraction pattern is concentric.

Sep 15, 2026

Upload by Adam

Hubble 5-Star Artificial Star FAQ provides practical guidance for setting up an artificial star to perform telescope collimation and star testing. It explains proper placement and aiming, including distance estimates linked to telescope focal length and aperture, plus how to choose pinhole sizes based on image clarity and lighting. The document details rough and fine collimation methods using defocused ring patterns and focused Airy disks, offers star-test procedure steps, and includes usage and battery troubleshooting. It also discusses how the Hubble Space Telescope used star testing after launch.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages8

Reading Time20 min

AccessFree to download

Q1: Where do you place the 5-star?

Q2: How far should the 5-star be placed from the telescope?

Q3: Which of the 5 stars to use for the star test?

Q4: How to perform the collimation with the 5-star?

Q5: How to perform the star test with the 5-star?

Q6: Can I store the magnetic mask against the pinhole mask?

Q7: Why will the unit not turn on after inserting batteries?

Q8: How was the Hubble Space Telescope tested after it had been launched into the space?

Hubble Optics Copyright, 2026 Hubble 5-Star Artificial Star FAQ Hubble Optics | [https://www.hubbleoptics.com](https://www.hubbleoptics.com) Updated April 15, 2026 Q1: Where do you place the 5-star? The 5-Star Artificial Star can sit on a tripod top, a table, or another stable surface. Aim it roughly toward the telescope; precision aiming is not required because the illuminated stars have a wide viewing angle. Then point the telescope at the artificial star and focus as usual. Q2: How far should the 5-star be placed from the telescope? For a full star test, place the artificial star as far away as practical. A commonly used estimate is to place it at about M times the telescope focal length: M = 336 * D / F^3 In this formula, D is the aperture diameter in inches and F is the focal ratio. For example, for a 10 inch f/5 telescope: M = 336 * 10 / (5 * 5 * 5) = 26.88 Distance = M * focal length = 26.88 * 10 * 5 = 1344 inches, or about 34 meters The artificial star must at least be far enough away that the telescope can reach focus. Roger W. Sinnott derived this distance estimate for Newtonian reflectors in Sky & Telescope (May 1991), based on ray tracing included in Harold Richard Suiter's Star Testing Astronomical Telescopes. Suiter notes that the same calculation gives an "incorrect distance" for SCTs. For SCTs and general use, his guidance is roughly M = 20 or more, and about M = 24 for an 8 inch f/10 SCT when doing a true star test. For final, critical optical testing, go as far away as practical and verify by experiment with your own telescope. For collimation, a shorter distance can still work well. If space is limited, you can do a preliminary test at a closer distance as long as the star can be focused and you understand that close distances can introduce spherical aberration. Q3: Which of the 5 stars to use for the star test? Use the smallest star that still produces a clear focused or defocused image in your telescope. The five precision pinholes are 50, 100, 150, 200, and 250 microns, giving you practical choices for different apertures, focal ratios, distances, and lighting conditions. If the image is too dim, use one of the larger pinholes or reduce the distance if practical. If all five stars are too dim to see clearly, replace the batteries. Current units are designed to be used without twisting the LED head cap. Use pinhole size, distance, and normal telescope magnification to select the best image for your setup. In theory, the pinhole diameter should not be larger than the artificial star's magnified Airy disk: pinhole diameter <= M * 1.22 * lambda * f / D Hubble Optics Copyright, 2026 Here M is the distance factor from Q2, lambda is wavelength, D is aperture diameter, and f is focal length. Q4: How to perform the collimation with the 5-star? First check rough collimation by observing a strongly defocused star image. Move the focuser in or out until about 10 rings are visible. The rings and central shadow should be concentric. If not, collimate the telescope according to the telescope manufacturer's instructions until the rings and shadows are concentric. A useful magnification for this rough check is about 25x per inch of aperture. Hubble Optics Copyright, 2026 In focus Out focus 1 wave front coma due to misalignment Hubble Optics Copyright, 2026 1/2 wave front coma due to misalignment 1/5 wave front coma due to misalignment Hubble Optics Copyright, 2026 1/10 wave front coma due to misalignment 1/10 and 1/5 wave front comas due to misalignment Then do fine collimation by observing the focused 50 micron star image, the Airy disk, at about 50x per inch of aperture. Use a 2x or 3x Barlow lens if necessary. A well-collimated telescope should show a uniform, complete, and concentric Airy disk and diffraction rings. Make small adjustments until the pattern is concentric. Hubble Optics Copyright, 2026 This focused Airy disk is the final judgment of collima

FAQs

How should the 5-star be aimed and positioned relative to the telescope?

Place the 5-star on a tripod top, table, or other stable surface, aim it roughly toward the telescope, and then point the telescope at the artificial star for normal focusing. Precision aiming is not required because the illuminated stars have a wide viewing angle.

What distance should be used for placing the artificial star?

For a full star test, place it as far away as practical. A common estimate is M = 336 * D / F^3, then Distance = M * focal length, with additional guidance that SCTs may require roughly M = 20 or more for true star testing.

What is the collimation workflow using the 5-star?

First do rough collimation with a strongly defocused view until about 10 rings are visible and the rings and central shadow are concentric, then adjust collimation per the telescope manufacturer. Finish with fine collimation by observing the focused 50 micron star image and Airy disk around 50x per inch of aperture, making small adjustments until the diffraction pattern is concentric.

Sep 15, 2026

Upload by Adam