Hubble 5-star Artificial Star(s)

The star test is the ultimate method to test and collimate your telescopes. The most and very much the only difficult part of doing the star test is that you need a star. Sadly, a real star is not always available, and you really may not want to spend your precious observation time doing star test even when it is available. Of course, you will also need a good tracking system for doing star test with the moving star. After all the troubles, due to the turbulence, the real star may not even reveal the true quality of your telescopes or give you a perfect collimation.

An artificial star will provide you an excellent alternative mean to do the star test anytime and anywhere you want, without all the drawbacks of the real stars. However, the problem with the artificial star is that you really need different size of artificial stars for different telescopes of different apertures with different F/#, and even for the same telescopes but at different distances, and under different lighting environment.

The innovative Hubble 5-star Artificial Star(s) is a perfect solution to this problem. It has 5 bright white LEDs with 5 precision pinholes (50/100/150/200/250 microns). It will enable you to test practically all the telescopes of different apertures with different F/#, from any reasonable distances needed, and under different lighting environment We are not suggesting that you should stop using any other methods or any collimating tools you feel comfortable with. You can continue your current practice, but after that always use the star test to validate or confirm your scope is indeed in perfect collimation; no other method (except the star test) can guarantee a perfect collimation. If your scope is still not in a perfect collimation after your current practice, you need to use the star test to fine-tune the collimation to its perfection. However, if you do not have any other collimating tool yet, then a star test with Hubble 5-star Artificial Star(s) alone will enable you to reach a perfect collimation with your telescopes.

You can instantly find out which star is best for your particular telescope at that particular distance under that particular lighting environment by simply choosing the smallest possible star, but which still give you clear defocused image 

You can even adjust the brightness of the stars by twisting the LED cap. 

You can mask out any 4 of the 5 stars with a provided magnetic mask. With Hubble 5-star Artificial Star(s), telescopes are truly easy to test and collimate!

Hubble 5-star Artificial Stars

To most accurately test and collimate  telescopes, reflectors, catadioptric,  and  
refractors, you must perform a star test. However, to do so, you need a star. Sadly, a real
star is not always available due to poor weather conditions or location. Even when a star is
available, you will need a good tracking system for doing star test as the star is always
moving. Also air turbulence may affect your test, and the real star may not even reveal the
true quality of your telescopes or give you a perfect collimation.

However, an artificial star is an excellent alternative  to do the star test. With an artificial star,
star tests can be accurately conducted anytime and anywhere. However, the problem with
the artificial star is that you need many different sizes of artificial stars for different
telescopes of different apertures with different focal ratios, and even for the same
telescopes but at different distances, and under different lighting environments.

The innovative Hubble 5-star Artificial Stars is the perfect solution to the star test problem. It
has 5 bright white LEDs with 5 precision pinholes (50/100/150/200/250 microns). The
HUbble 5-star Artificial Stars enables you to test virtually all telescopes, regardless of
aperture size, focal ratios, distance, and lighting conditions.

• You can instantly find out which star is best for your particular telescope at any
  particular distance and lighting environment by simply choosing the smallest
  possible star that still gives you a clear and defocused image.
• You can even adjust the brightness of the stars by twisting the LED cap.
• You can mask out any 4 of the 5 stars with a provided magnetic mask.

With Hubble 5-star Artificial Stars, telescopes are now easy to test and collimate!

• Please make sure the mask is clean, and use it only when needed to prevent the
  blockage of the pinholes.
• The unit should be kept in a clean Ziploc bag when not used, and should be
  separated from the magnetic mask.
• The Hubble Optics 5-star Artificial Stars is powered by 3 AAA batteries (Not
  Included).

Please note that there are NO printed instructions in the package. To setup, you simply
need to insert 3 AAA battery cells, and turn it on.

Here are some very useful online helps on star test:

Telescope Collimation via Star Test by Thierry Legault
Aberrator, an extremely useful star test simulator by Cor Berrevoets

A must have book by Harold Richard Suiter:
Star Testing Astronomical Telescopes, Second Edition
There is also a brief but excellent chapter on the star test in Richard Berry’s
Build Your Own Telescope

Q1:  Is there a printed document for the Hubble 5-star Artificial Star(s)?
There is no printed document. But we will maintain this online FAQ up to date as a brief
document to the 5-star.  Here is the printable version of this FAQ.
For complete and detailed instruction on the collimation and star test, please refer  the
must have book by Harold Richard Suiter,   Star Testing Astronomical Telescopes, Second
Edition

Q2: Where do you place the 5-star during the test?
The 5-star can just sit on a tripod top, on a table, or even on a rock. You need to aim the
star roughly towards (no precision aiming required!) to your telescope; then aim your
telescope to the 5-star. The 5-star provides a very wide angle for a very easy usage.

Q3: Which of the 5 stars do I use for the star test?
Choose the smallest possible star that still gives you a clear defocused image. You may
need to dim the stars with the new batteries by twisting the LED head cap. You change the
brightness by adjusting the alignment among the LEDs and the pinholes. Change
batteries if all stars are too dim to see clearly.

Q4: How far should the 5-star be placed from the telescope?
The 5-star should be placed at a distance from the telescope about M times of the focal
length of FL; M is 336*D/F^3, or 336*D/(F*F*F) for a Newtonian(May, 1991, Sky and
Telescope, Roger Sinnott), where D is the Clear Aperture  (in inches) and the F is the focal
ratio. E.g., if your scope is 10" F/5, then the M is 336 x 10 / 5^3 = 336 x 10 /(5 x 5 x 5) =26.88.
So the 5-star need to be M x FL = M  x  D x F = 26.88 x 10 x 5 = 1344" away, or about 34 m
away.  In general, a minimum of 20 for the M is suggested by Suiter.

The above distance is for the real star test, for the collimation purpose; about 70% of
above distance is good enough.

As long as you have enough back focus to focus on the close by object,  you will be
surprised how close you can get for the collimation. You may need to add one or two
focuser extension tubes.

Q5: How do I perform the collimation with the 5-star?
First you should check if the scope is in rough collimation by observing a strongly
defocused star image (about 10 wavelets, or move focuser in or out until seeing about 5-
10 rings). All rings and shadows should be concentric; if not, please perform the
collimation according to the instruction of the telescope until all rings and shadows are
concentric. You should do this at a magnification of 25X of your scope’s diameter (in
inches).

Coma due to misalignment of a 10" F/8 scope:

Then you need to do a fine and final collimation by observing the focused 50 microns
star image, the famous Airy disk with a magnification of at least 50X of your scope’s
diameter (in inches). Use a 2X, or 3X Barlow lens if necessary.  You should see a
uniform, complete, and concentric Airy disk and diffraction rings if the scope is in
perfect collimation. Follow the same procedure to do minor adjustment on your scope
until you reach a perfect collimation.

This is most accurate method to collimate your telescope. In a real star the seeing
limit make it unlikely for you to see the Airy disk or to achieve this level of
collimation.

Q6: How do I perform the star test with the 5-star?
Choose an appropriate star for your scope (Q2). After making sure the scope is in
perfect collimation(Q4), follow the normal Star Test procedure to perform the test.

Q7 After inserting the batteries, why isn't the unit turned on?
Please make sure all cells are inserted in right direction, the spring to the negative.
Please re-insert all the cells if necessary to make sure all cells are contacting the
nodes.  Try some new cells in necessary

Here is a description (F. Roddier, C.Roddier, Appl. Opt. 32, 1993) on how the star
test was conducted on the Hubble Space Telescope (HST) , “we requested that the
highly defocused images be taken in flight by HST so that the method (the Roddier
method) could be applied to estimate the exact amount of spherical aberration.
Because defocusing the imaging also defocus the telescope tracking system, it
was not possible to obtain images sufficiently defocused for the method to apply.
However, defocused images recorded by the HST are not blurred by the
atmosphere and can be taken through narrow-band filter. In this case the wave-front
information is still preserved and can be recovered by using phase-retrieval
algorithm”

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