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#1
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Help with reflecting telescope
Hi,
I am complete newbie to telescopes, I just bought a reflecting telescope (Astro-Nova 100 Telescope 300x) by Edu Science at Toy'r'us shop. I have done a very careful handling and setup, nevertheless, there definitely is a problem because the image I see in the eyepiece is blocked (at the center of the image) by the shape (shadow) of the internal diagonal mirror. Am I missing something? Is my telescope somehow broken? Could you please shed some light on my issue? Thank you very much in advance for any help. |
#2
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Help with reflecting telescope
I have done a very careful handling and setup, nevertheless, there
definitely is a problem because the image I see in the eyepiece is blocked (at the center of the image) by the shape (shadow) of the internal diagonal mirror. Am I missing something? Is my telescope somehow broken? Could you please shed some light on my issue? You should only see this effect during the day. If you look at night, the shadow of the secondary will disappear. To put you at ease: no, you haven't done anything wrong, and this is not a defect of the scope. -- Curtis Croulet Temecula, California 33°27'59"N, 117°05'53"W |
#3
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Help with reflecting telescope
Curtis Croulet wrote:
I have done a very careful handling and setup, nevertheless, there definitely is a problem because the image I see in the eyepiece is blocked (at the center of the image) by the shape (shadow) of the internal diagonal mirror. Am I missing something? Is my telescope somehow broken? Could you please shed some light on my issue? You should only see this effect during the day. If you look at night, the shadow of the secondary will disappear. To put you at ease: no, you haven't done anything wrong, and this is not a defect of the scope. The original poster may be wondering how that could be. For him: it has to do with the size of your pupils - small in daylight, large in the dark. |
#4
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Help with reflecting telescope
Marco Dorantes wrote:
Hi, I am complete newbie to telescopes, I just bought a reflecting telescope (Astro-Nova 100 Telescope 300x) by Edu Science at Toy'r'us shop. I have done a very careful handling and setup, nevertheless, there definitely is a problem because the image I see in the eyepiece is blocked (at the center of the image) by the shape (shadow) of the internal diagonal mirror. Am I missing something? Is my telescope somehow broken? Could you please shed some light on my issue? Thank you very much in advance for any help. Perhaps you are not using an eyepiece in the telescope. I will assume you have a newtonian reflector (cold be wrong). small inch or 2 inch (ok, 0.96x", 1.25" or 2" for the purists). If you have no eyepiece then the scope will be useless. Make sure you have an eyepiece. Second thing that could be wrong is that you are looking at a star and the focus is way off. Out of focus stars look like fuzzy donuts. Somehow I suspect the first scenario. |
#5
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Help with reflecting telescope
lal_truckee wrote:
Curtis Croulet wrote: I have done a very careful handling and setup, nevertheless, there definitely is a problem because the image I see in the eyepiece is blocked (at the center of the image) by the shape (shadow) of the internal diagonal mirror. Am I missing something? Is my telescope somehow broken? Could you please shed some light on my issue? You should only see this effect during the day. If you look at night, the shadow of the secondary will disappear. To put you at ease: no, you haven't done anything wrong, and this is not a defect of the scope. The original poster may be wondering how that could be. For him: it has to do with the size of your pupils - small in daylight, large in the dark. looking at a bright moon may show the secondary mirror for the same reason given for daylight. Not a defect. |
#6
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Help with reflecting telescope
On Mar 3, 4:48*pm, Marco Dorantes wrote:
(snip) I just bought a reflecting telescope (snip) there definitely is a problem because the image I see in the eyepiece is blocked (at the center of the image) by the shape (shadow) of the internal diagonal mirror. Am I missing something? Is my telescope somehow broken? Could you please shed some light on my issue? To provide added support to what others have already stated: You're not missing anything other than experience with a reflecting telescope. Your observation is *not* indicative of a broken telescope. Your reflecting telescope has a diagonal (often referred to as a secondary) mirror in the middle of its optical tube assembly (OTA). When you look *at* the eyepiece from a distance when the telescope is pointed at any bright, daytime-illuminated object you *will* see a bright disk of light with a smaller, dark disk in its center. This is the telescope's "exit pupil", and this appearance is perfectly normal. Apart from the exit pupil, when you point the telescope at the night sky each star will take on the same appearance -- a disk of light with a smaller, dark disk in its center -- *until the telescope's focus is properly adjusted*. As the telescope arrives closer to a proper focus these disks will shrink. When the telescope reaches a proper focus the stars will take on the expected appearance of tiny, pinpoints of light *without* dark spots in their centers. Under most circumstances the dark central spot in the telescope's exit pupil (when looking through the focussed telescope) will fall in the center of your eye's pupil. The surrounding light will enter your eye and form a more or less flawless image on your retina. The dark spot will have no visible effect most of the time when the telescope is used for astronomy. It's only visible effect will occur when low or very low magnifications are used when looking at bright or daytime objects. This is because the dark central spot increases in size as the magnification is lowered -- *and* the eye's pupil *decreases* in size when looking at brighter objects. At low enough magnifications, when looking at bright enough objects the spot can block most of the light from the eye's pupil and create an undesirable 'shadow' effect, but under most normal circumstances, particularly when using the telescope astronomically, this effect will be completely unnoticeable. Bill Greer To sketch is to see. http://cejour.blogspot.com http://www.rangeweb.net/~sketcher |
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