The star test is the ultimate method to test and collimate all kinds of your telescopes, reflectors, catadioptric, refractors, and the Hubble Space Telescope in space. 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 that 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 conditions.
-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 head.
-You can mask out any 4 of the 5 stars with a provided magnetic mask.
-Please make sure the cleanness of the mask, and only put it on when needed to prevent the possible blockage of the pinholes.
-The unit should be kept in a clean Ziploc bag when not used; separated from the magnetic mask.
-It is powered by 3 AAA batteries (Not Included).
With Hubble 5-star Artificial Star(s), telescopes are truly easy to test and collimate!
Our Hubble 5-star Artificial Star(s) is priced affordably at the special introduction offer at $19.95 + $5 (S&H).
Ready to ship!
Q1: Where do you place the 5-star?
The 5-star can just sit on a tripod top, on a table, or even on a rock; you only need to aim the star roughly towards (no precision aiming needed) to your telescope; then aim your telescope to the 5-star. The 5-star provides a very wide angle for a very easy usage.
Q2: How far should the 5-star be placed from the telescope?
The 5-star should be placed in distance to you scope about M times of the focal length. 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 diameter of the mirror (in inches) and the F is the focal ratio. E.g., if your scope is 10" F/5, then the M is 336*10/5^3 = 336*10/(5*5*5) =26.88. So the 5-star need to be M * (D * F) = 26.88 * 10 * 5 = 1344" away, or about 34 m away. In general, a minimum of 20 for the value of 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.
Q3: Which of the 5 stars to use for the star test?
Choose the smallest possible star, but which still give you clear defocused image. You may need to dim the stars with the new batteries by twisting the LED head cap. Basically you change the brightness by adjusting the alignment among the LEDs and the pinholes. You need to change batteries if all stars are too dim to see clearly.
In theory, the diameter of the pinhole should not be larger than the M * Airy disk = M * 1.22 * l * f /D (where M is the distance factor (see Q2), l is the wavelength, D is the aperture diameter, and f is the focal length)
Q4: How to 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 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 scopes diameter (in inches).
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 50X of your scope's diameter (in inches). Use a 2X, or 3X Barlow lens if necessary;You should see an uniformed, 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 the final judgment of the collimation of your telescopes and all other collimation tools and methods! Due to the seeing limit, you will most likely not be able to see the Airy disk with a real star!
Q5: How to 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.
Q6: After batteries are inserted, why the unit cannot be turned on?
Please make sure all cells are inserted in the right direction, spring with the negtive end. You may try to reinsert the cells to make sure all are in good contact.
Q7:How was Hubble Space Telescope Tested and Collimated in Space?
Of course, the star test!
We are grateful to the feedbacks from our customers:
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-Item as described (actually, even better), packed well, - thanks!
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-...achieved the best collimation I have had in a long time. I like using an artificial star.
-This is exactly what I have been looking for...
-** Best seller of all! ** Thanks for advice about Item handling!! Thanks a lot!!
-Thank you very much about your new Star-item. It works very well. I am so happy. Clear skies to you and may your summer days be warm and full of sales!
-Works a treat! Great Astro bargain. Highly recommended. Very Fast delivery!!!
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-This little thing is fabulous value for the few dollars you are charging. I've been contemplating various other types of artificial star gadgets, but, they all seemed so expensive. This little guy is simplicity in itself, and does the job fabulously. Extremely good value at the price you are selling it for.
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-Great product... AMAZING CUSTOMER SERVICE!!!! Highly recommended!
-I am wondering why I didn't get one of these long ago...
-The best $20 astronomical investment I have ever made
-Every telescope user should have one
To order: www.hubbleoptics.com/artificial-stars.html