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Sling adjustment on obsession classis 18"

[email protected] All Messages By This Member #303 Hello I have since years (2008) a classic 18" Obsession and I just love it. But it's time to recoat the mirror and this makes me a bit scared to move the mirror in and out of the mirror box (although I've done it myself in 2008 but now I feel less confident about it). So here is the question:? is there besides the instruction in the manual a video available on how to install the mirror in the mirror cell and on adjusting the sling? Or a post with pictures?? Also, in the manual it's recommended? to put double sided tape. Will I be able to reuse the curent one ? If not how do I get a good one (I live in Europe, Belgium)? What's the optimum position of the sling? I mean, where should the centre (of the width) of the sling be positionned? In the middle of the mirror edge? Or a bit more to the bottom because that's the direction of the Centre of Gravity? I guess it's also important to install the mirror in the centre of the mirror cell to make sure the supports are placed on the right positions on the mirror. How critical is this to avoid astigmatism? Thanks for the feedback Olivier ??
Linton Guise All Messages By This Member #304 开云体育 Olivier, It’s much less of a problem than you may think. Slide the mirror away from the sling to give a little room to release the double sided tape from between the sling and the mirror edge (you may need a thin knife). Let the sling drop off the mirror turn the three mirror clips well out if the way (you may need a spanner to loosen them). If you can get someone to help you lift the mirror out you may feel more confident, but an 18” is fine for one person. There’s enough room to get your fingers under the mirror while keeping your palms away from the reflective coating. Lift out carefully and place it in a box. I made one from wood with carpet on the bottom to support the mirror. When you come to replace it any double sided tape will do, it only has to stop the sling from falling off. Attach about 4cm of the tape to the edge of the mirror, but leave the top tape coating on until you have the mirror in place. Now remove the top coating and with the mirror pressed away from the sling to give yourself some room, slip the sling up and onto the tape ( this can be a bit of a fiddle as there’s not much room.? Don’t forget to turn the mirror clips back into position! The mirror should hang free of any of the black acytl supports so that all the weight is on the sling when the scope is tipped right down. Whenever I collimate my obsession I always press the mirror from the back first to check it is still swinging free. My fabric sling is pretty much the full size of the mirror edge, one day I will get round to buying one of the Glatter metal slings that ride up and down with the mirror when collimating etc. These sound a great idea, but to be honest I have not had a problem with my fabric sling. I only once had an astigmatism problem and I traced this to one of the triangular mirror supports which had got stuck and was not supporting the mirror properly (this was not an obsession scope) once I released it the mirror settled back into shape and the problem disappeared, it’s amazing what glass can do! I hope it all goes well for you, I just had my Obsession 20” recoated here in England for the first time. The original USA coating from 2006 lasted very well and the firm here had real problems dissolving it off! Best wishes, Linton L.J.Guise Physics Dept. Bedford School. www.bedfordschool.org.uk/observatory On 30 Oct 2021, at 09:37, Ovanaelst via groups.io <Ovanaelst@...> wrote: ?Hello I have since years (2008) a classic 18" Obsession and I just love it. But it's time to recoat the mirror and this makes me a bit scared to move the mirror in and out of the mirror box (although I've done it myself in 2008 but now I feel less confident about it). So here is the question:? is there besides the instruction in the manual a video available on how to install the mirror in the mirror cell and on adjusting the sling? Or a post with pictures?? Also, in the manual it's recommended? to put double sided tape. Will I be able to reuse the curent one ? If not how do I get a good one (I live in Europe, Belgium)? What's the optimum position of the sling? I mean, where should the centre (of the width) of the sling be positionned? In the middle of the mirror edge? Or a bit more to the bottom because that's the direction of the Centre of Gravity? I guess it's also important to install the mirror in the centre of the mirror cell to make sure the supports are placed on the right positions on the mirror. How critical is this to avoid astigmatism? Thanks for the feedback Olivier ?? This message has been sent through the Bedford School email Server, and is intended for the addressee(s) only. If you have received this message in error, please contact the sender, or administrator@..., and delete the email. The views expressed are the views of the sender, and not necessarily the views of the School. The information in this message may be confidential and should not be read, copied, or otherwise distributed unless permission is given. Bedford School is part of The Harpur Trust: a company limited by guarantee. Registered in England: Company No. 3475202. Registered Office: Pilgrim Centre, Brickhill Drive, Bedford, MK41 7PZ. Registered Charity No. 1066861

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