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hi guys,

i have a skywatcher skyliner 150p (6 inch dobsonian), and i took the bottom out to clean the mirror, before this happened my optics were fine. but since i have taken the bottom of the telescope apart i have noticed a double image on my optics, i dont know if there is problem with my eyepieces or the mirror. if any of you know what will have caused it and if you know how to fix it please could you reply to this messsage.

reagards

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Hi Maximillion

To be honest i have'nt seen or heard of a double image before, what i would check is both your primary and secondary mirrors are clear and not chipped, you say you've removed the primary mirror, all i can think of and suspect is that the mirror alignment is out and could need re-collimation.

Sorry i couldn't be of anymore help.

Simon

Edited by Si W
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Are the 2 images equal in brightness, and how far separated.

First thought was secondary reflection off of the glass surface but that only occurs on rear silvered mirrors - like those hung on walls and in bathrooms. Scope mirrors are front silvered.

Presume that since replacing you have fully centered and recollimated it the whole thing.

Did the disassembly include any other action? As in did you clean anything else like the side walls? Reflection off of these is what I am thinking.

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thank you for replying. yes i did remove the bottom, the counter weight from the mirror, and just used soap and water to clean the it. i thoroughly wiped the mirror and there were no scratches or chips. but when i put the mirror back in i didnt realise you had to re-collimate the mirror. i thought cleaning it was the right thing...but obviously not. i will try collimating my mirrors now and thats helped a great deal, thank you. the double images are not far apart at all, nearly touching. but you have a very detailed one and one that is fainter and less brighter than the detailed image, it is just a blurry blob on the field of view.

regards

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There's nothing wrong with cleaning your optic's every now and again, but as soon as you start removing your primary mirror, or secondary for that fact, you will always need to re-collimate your optic's. What i would say is there's nothing wrong with a bit of dust on the primary mirror as long as it's collimated, it will work better than a sparkling clean primary thats out of allignment, a bit of dust and the odd little dew stain will do no harm.

Simon

Edited by Si W
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again thankyou for the reply. and may i ask how you can re-collimate the mirrors because i have never come across this before and i dont know how to do it. i have seen off websites that you can buy a Cheshire collimation eyepice and a deluxe laser collimater. which one would you say is better and how would you re-collimate ?

reagrds

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Here's astrobaby's collimation guide......

Astro Babys Guide to Collimation

Cheshire collimators are easy to use and pretty accurate, and also quite cheap.

Laser collimators are a bit hit and miss. The cheaper ones can be out of collimation themselves, and even expensive ones like the Hotech rely on your focuser being absolutely square on to the tube. If it isn't, your collimation will be out.

EDIT.....you beat me to it Si !!!

Cheers

Rob

Edited by RobH
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Here's astrobaby's collimation guide......

Astro Babys Guide to Collimation

Cheshire collimators are easy to use and pretty accurate, and also quite cheap.

Laser collimators are a bit hit and miss. The cheaper ones can be out of collimation themselves, and even expensive ones like the Hotech rely on your focuser being absolutely square on to the tube. If it isn't, your collimation will be out.

EDIT.....you beat me to it Si !!!

Cheers

Rob

But sound advice Rob :rolleyes:

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Have you tightened the clips holding the primary mirror in its cell? There should be clearance between the mirror and clips equal to the thickness of a piece of paper, the mirror should be able to rotate. If the clips are tight they could cause the double image you describe.

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thank you to everyone that replied. it has been a massive help. me and my dad collimated the primary mirror, but without using a collimator and now the mirror seems to be aligned perfectly with the second mirror. if this still doesnt help, i know a friend who has a collimator and i will fix it with him. all i need to do now is wait for clear skies and hope for the best that the double image has improved or gone away. thanks for your help.

regards

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