Question about Celestron NexStar 5 SE (300 x 44.45mm) Telescope

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Black spot in the center of the image viewed in telescope

I see a black spot in the eye piece when a viewing a star

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  • Anonymous Dec 14, 2008

    Celestron NexStar 5SE

  • nabdurrahman Jan 29, 2009

    Its a catadioptric Celestron NexStar 5SE.

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If this is a Newtonian reflector or a catadioptric scope (Schmidt Cassegrain or Maksutov) you may be trying to use it at too low of a magnification. Your magnification needs to be high enough that the exit pupil is less than 5 mm; to figure this divide the focal length of the eyepiece by the f-ratio of the optical tube. If this quotient is 5 mm or more the black spot you are seeing is the shadow of the secondary mirror.

Posted on Jan 28, 2009

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What type of telescope are you using?

Posted on Dec 14, 2008

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Hi, a few days back I purchased Nexstar 4SE. I set it up exactly how it says in the manual still I cannot see any magnifying views from the eye piece. While aligning the telescope I can find the moon from...


Stars will always appear as points. It is not possible to magnify them enough to see them as disks because they are all extremely far away. A telescope will however show you stars and other objects that are too dim to see with the naked eye.

You will be able to see the planets as disks, and even features on the planets, such as the bands on Jupiter, the rings of Saturn and the phases of Venus, and also moons around some planets. There are other objects that will show more detail when magnified, such as nebula. You will be able to see a lot of craters and other detail on the Moon.

Your problem is simply that you are not pointing the telescope at these objects. This seems to be one of those telescopes that "automatically" finds objects, but these so called "go to" scopes only do this when they are set up properly. I can't say what step(s) you have missed, but clearly even if the scope thinks it is pointed at the moon, if you can't see the moon, it is NOT pointed there. The Moon will fill the field of view even with the least powerful eyepiece. If you are seeing stars as points, then the eyepiece is focussed and working properly.

Jan 13, 2011 | Celestron NexStar 4 SE Telescope

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When viewing venus or other stars there a black spot in the center of the object. It appears to be the 2nd mirror refleting to the main miror. what have I done incorrect?


You are NOT in focus. Turn the focus knob a little until you see a perfect "disk" for the planet. Stars are always POINTS of light, with a telescope or without a telescope.

Aug 28, 2010 | Celestron NexStar 114GT (269 x 114mm)...

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Ditto


You bought what we call a toy "department store telescope". Put the eyepiece with the largest number written on it into the scope. DO NOT use any 2x barlow which might have been included.

Go outside during the daytime and practice focusing on a distant object. AND---- no you will not get 450 magnification from that telescope, even though it was written in bold letters on the box.

Sep 21, 2009 | Bushnell NorthStar 78-8831 (525 x 76mm)...

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When i view a star or small object through my reflecting telescope i can see the reflecting mirror in front of the image. this does not happen when viewing the moon.


You may need to realign the mirrors and the view piece. You can look at the mirror from the front and your eyeball should ne centered.

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Fuzzy bright stars with my Celestron CPC 1100 XLT


The image shows that the optics are not centered properly. The secondary may be tilted slightly to the 2 o'clock position. When not centered, a focused star will have an astigmatic shape, and not come to a full focus. Also check the mirror and corrector plate for dewing, that will also affect the views.

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Black dot.


Ensure focusing is spot on. if your image is a black dot surrounded by white light (like a doughnut) then your not in focus. Look at making a Hartmann Mask (really easy, just google for it), which fits over the front lens. It has 2 or more holes in it,this means when you look through the eye piece you will see double images, adjust focus until the images merge into one (if the images go further apart turn the focuser the other way), when they are merged remove the mask and presto you should be in optimum focus. Always remember telescopes are very sensitive and focussing requires delicate adjustments.
Regards and Clear Skies
Carl

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2 Answers

Viewing planets and stars


The problem is you are way out of focus. Turn the focus knob alot, until the star image gets much much smaller. Keep going until it looks like a pin point or a star!. The spider vane and center black dot will disappear. This black dot is actually the secondary diagonal mirror reflection in the primary mirror. The peace signs are the secondary supports. Use the lowest power eye pieces. I would not use the Barlow lens that comes with this scope as it very poor quality. Also, using this high power with this small an aperature (tube diamter) & unstable mount will be very difficult indeed. Invest in some wide angle, long eye relief low power lens. Use these for a while before going to higher powers.

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