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Can't see anything through a refractor Astromaster...


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Hi everyone,

a work colleague of mine has bought his son a refractor Celestron Astromaster - but can't see anything through it. All he sees is white, whether during the day or night. He says he can't see anything obviously wrong and thinks it may be faulty. I said I would ask the wonderful folk on SGL if they had any answers.

Let me know if you have any solutions or need any more info to help solve the problem.

Thanks

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It's a focussing issue, on my first cheap refractor I had the same problem. First thing to check is to make sure he's not using the barlow or a high power eyepiece, Human nature I suppose but us newbies always go for the highest mag thinking it's somehow better. 2nd thing to check is to make sure he is using an eyepiece. Some people think the eyepiece is just for magnification and don't realise its part of the optical train. ok you've checked the obvious silly things. make sure you are looking at an object a long way away. 1/2 to 1 mile is fine. now SLOWLY rack the focus in and out till focus is reached, don't forget you will be using your lowest power eyepiece and the image may be upside down. If this fails then you may have a dud and you need to send it back. rather than have him taking the thing apart to see where it's come out of alignment.

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Just curious,

Can you try one of your own eyepieces on your friend's scope?

Also, is the diagonal intact? I have seen some instances with cheap scopes with mirror diagonals where the mirror inside the diagonal has some loose or even gone missing. You would see some brightness in that case, but obviously no image.

If the scope has enough focus travel, you might wish to try assembling the scope without the diagonal. Obviously it would focus about 1.5 inches farther out, but even if you didn't quite get to focus, you could see if an image was starting to form.

Dan

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the diagonal on the latest astromasters are prisms. so you get a right way up image. if its a plastic ball shape like mine,its a prism diagonal. can be unscrewed so you can see inside the main tube.

to see if its the diagonal thats the problem, just remove it and place a working e/p inline with the main optics ( like a trditional telescope) but like i was told, you may need to make a temperarry cardboard tube to extend the distance.

was it new ? or second hand?

they are great telescopes for the money, im very pleased with the glass and mount. only the finder is pants,oh and the fine adjusters are just way to small.

good luck...

Edited by rory
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might be worth him taking everything out and looking through the bare scope from the objective and end from the drawtube end to see if he can see through. this rules out one part. the next is can he see an image when holding the diagonal in his hand (not when in the scope).

next put the diagonal in the scope and can he still see light through the diagonal?

finally, look through an eyepiece in his hand and assuming he sees light coming through (presumably though not a sharp image) put it in the scope.

this process should at least identify the exact aspect that's creating the bother.

daft question. he is taking the cap off?

check by the way that it is actually a refractor.

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Hi guys,

One other idea occured to me - although it is a bit off the beaten track, I have seen it happen before.

Has the eyepiece been disassembled at all? I have seen people (not you lot, of course!) who have disassembled an eyepiece for cleaning, then been "surprised" by all the different lenses inside! :eek:

If the lens elements weren't reassembled in the right order, or switched about (front to back), the scope may not focus at all. The only easy way to test this is to put a different eyepiece in and see if that works.

I'm probably thinking about Zebras when I should be looking for horses.... :)

Dan

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I've been away for Easter, but shall share all these pearls of wisdom next week when back at work. Thanks once again for the great responses. I'll update again to let you know if anyone hit the jackpot as it were...

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  • 3 weeks later...

SGL has triumphed again - I pasted all the comments into an email and sent them on, and low and behold he has fixed his problem - it was a focussing issue after all. Thanks everyone for your input.

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