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So I recently got into astronomy and I am using my fathers old Meade EQ1-B reflector telescope. This is my first night using it and I have come across a few questions. To begin, the telescope was left alone for several years (the scope is a fairly old model) and may have become damaged over time, yet nothing too severe. We were cleaning it and got to the mirror to find that over the years the "mirror" cover on top of the glass had chipped away all over, giving the result of a patchy look.

We were testing the scope out during the day and the image was fine - the mirror didn't affect it. Now, I am looking upon stars and have noticed a couple of things. When viewing these stars the image sort of moves, not the scope, the image. As if it were an animation, the star isn't just a white blob, it looks like the sun, where the blob is moving - as if it were a liquid. No I am not stupid enough to point the scope at the sun... during night time. The stars just move like a liquid in the center, is this an effect of the mirror? I can't see why it would be as the image was fine during daylight. Is this how all stars work? I haven't had a chance to point it at the moon or any other planets so I can't test it on an object that isn't a star.

Also, as the scope is a reflector it has the "three lines" on the front, however this interferes with the object I am looking at as i can see the lines on the star. Is there any way to stop this, or is it just the result of using a reflector?

Thanks!

Image below: enter image description here

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The tag "refractor-telescope" is incorrect for this question. Please remove it (or let the moderators do it if you can't). –  Florin Andrei Apr 19 at 1:13
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3 Answers 3

up vote 10 down vote accepted

the "mirror" cover on top of the glass had chipped away all over, giving the result of a patchy look.

Optics can take a huge amount of damage (chipping, scratching) before it really starts to affect performance. You'll be surprised at the amount of abuse a telescope can take like that. As long as it's not properly cracked in two, don't lose any sleep over it.

The stars just move like a liquid in the center

The moving around is normal. It is due to atmospheric turbulence, which happens all the time. Unless you're in a vacuum, the images will always shimmer a little. Sometimes they will shimmer a lot. Other times not so much.

In astronomy we have a word for this - it's called seeing:

http://en.wikipedia.org/wiki/Astronomical_seeing

Also, as the scope is a reflector it has the "three lines" on the front, however this interferes with the object I am looking at as i can see the lines on the star.

You are way, WAY, WAY out of focus. The scope might also be completely miscollimated. The star must not appear like a big blob, with the "lines" and the image of the secondary mirror visible in the middle, like in your photo.

The "lines" are called spider vanes - they are parts of the assembly called spider, which holds the secondary mirror in place. The vanes, or the secondary mirror itself, must never be visible in the image.

First, do a rough, purely visual collimation. Do this in a place with plenty of light (inside the house). Take out the eyepiece. Look into the focuser. You'll see the secondary mirror. Reflected in it, you'll see the primary mirror from the bottom of the tube. Reflected again in the primary, you'll see the focuser, with your eye in the middle.

enter image description here

If things are more or less centered, like in the third diagram above, leave it alone. If they are way out of center, like in the first diagram, use the adjustment screws on the mirrors and center everything. Collimation is very important to performance. A miscollimated scope will perform miserably. This is FAR more important than all the scratches on the mirror.

Again, this is purely visual, no-tools collimation. This is all you need for now. You can get a laser collimator later, after all your problems are solved. This is the article where I copied that image from, if you need more info:

http://www.skyandtelescope.com/astronomy-resources/how-to-collimate-your-newtonian-reflector/

Also see this document:

http://www.etnaastros.com/documents/No_Tools_Collimation.pdf

Once collimation is done, you need to find true focus. Go outside at night. Point the scope at a medium-bright star. Polaris, if you can find it, is great because it doesn't move.

Now moving the focuser back and forth, try and determine which way you can make the image of the star appear smaller. Now keep adjusting the focuser until the image of the star is super tiny, then it starts to grow again. Then back off until you make it as tiny as possible. That's when it's in perfect focus.

Now point the scope at a very bright star. If your scope has 3 spider vanes on the secondary mirror, you may see 6 spikes coming out of the star. Like this:

enter image description here

If your scope has 4 vanes, then you should see 4 spikes, like this (it's really 8 spikes, 2 times the number of vanes, but in this case they are superimposed 2 by 2):

enter image description here

The diffraction spikes are easily visible on very bright stars. On medium-size and small stars, they are not easily visible, or not visible at all. This is normal.

Unless the stars are super-tiny dots like in the images above, your scope is not ready for use. Do your best to collimate it and find true focus. Make the stars super-tiny.

Good luck and let me know if you need more advice. It would help a lot if you could find an experienced astronomer nearby to help you fix the scope.

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I have removed the eye piece and looked at the secondary mirror. The 'Spider vanes' do not look off center and nor does the my eye when looking. Does this mean it is correctly collimated? Also, I am using a 25mm eyepiece and when viewing objects such as stars, they appear tiny, is this due to the magnification? –  Harry Kitchener Apr 19 at 1:25
    
Okay, that's good, it's probably well-enough collimated (for now). Stars must always appear tiny - if not, then your scope is not focused properly. But make me understand: when you look at a bright star (not a planet, neither Mars nor Jupiter), what do you see? Does it look more like in your image, or more like in one of my images? –  Florin Andrei Apr 19 at 1:28
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When you say 'move ' do you mean it travels across the view, this will be the earth rotating. Or is it sparkling, this will be the interference from earths atmosphere.

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It isn't moving, it looks like a ball of molten liquid, is this normal? Also, I'm having problems lining my sight up, is this a normal thing also? –  Harry Kitchener Apr 18 at 23:15
    
It does sound like like the atmosphere, try looking at the moon or another planet and it should be clearer. As for the sight, I find it a bit tricky, but I do mine during the day on something close, then again on something further away. It's not always dead centre but it gets the object into my view. –  taintedromance Apr 18 at 23:25
    
Ok, I shall have to wait till three in the morning to get the moon into sight, as my parents wont allow me to go outside due to all the hassle of moving the scope. Also, I can provide an image if necessary - it is a tad 'ghetto' in the sense that I just placed my phone over the eye piece. XD –  Harry Kitchener Apr 18 at 23:27
    
Also, I am only using a 25mm eyepiece as my father lost the others over the years... :( –  Harry Kitchener Apr 18 at 23:29
    
A single star won't have much, if any detail(they are literally balls of gas). I usually only look at stars if there is a cluster of them. Wait until you see the moon, that is amazing the first time. –  taintedromance Apr 18 at 23:34
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Florin's answer covers most of what I would have said, except one problem which I have faced and I think deserves mention.

The telescope assembly might vibrate. You don't need a gale for that to happen. Depending upon where you place it, even a slight breeze might make it vibrate. The solution is to fix your mount on a terrain which is flat for at least a 100 sq m area around it. It does seem cool in pictures, and perhaps movies to fix it on a high mound but a height gradient makes wind currents(local, of course) to turn an twist which causes the telescope to shake. I am sorry I couldn't find an image to support it.

P.S. This information came in the manual of my telescope which is a Skywatcher 8" Dobsonian

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