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I remembered that I had a spare Orion[UK] 8" tube ring. These are an unusual design being a flat strap. Albeit with a hinge and the usual thumbscrew locking when closed.
I could clamp this on the tail end of the 8" diameter tube of the 7". Then arrange a light tube to support the H-alpha optical train alongside.
The advantages are only one ring to loosen and rotate if need be. Better lateral support than cantilevered out from the tail of the 6" for greater stiffness.
The support 'arm' can have a tube ring to clamp the H-alpha extensions. This will avoid having to rotate the support with changing OTA attitude.
The downside is the already 'busy' tail end of the 7". There are two U-shaped handles, a tube balance weight, slide rail and a finder base in the way. Which means the removal of the tailpiece to allow access to the internal nuts.
I'd like to find a more angular tailpiece. i.e. A sturdy, aluminium saucepan with much more of a right angle at the base. Rather than the present one with softly tapered sides and gently rounded corner between the base and the sides. I shall have to search for another pan in the charity shops and flea markets.
Cost is almost nothing but requires very little work to produce a really solid and strong tailpiece. My present 'pan' jams on the end of the main tube before collimation can be achieved. Saucepans come in every shape, size, thickness and weight. Fortunately, for me, aluminium has gone out of fashion since Alzheimer's was invented. Which means some of them reach a cheap outlet rather than being scrapped.
I just need to ensure a few millimetres clearance over the main tube so that it it doesn't jam tight. 203mm minimum ID. Stainless steel is much more commonplace but much harder to work. Such pans usually have a pointlessly deep and heavy base to spread the heat of cooking.
Stop laughing at the back, Philistines! 😊 Can you even imagine what it would cost to have a casting made and bored out to this size? The geometry and material of the pan provide all the stiffness without the weight.
Success! A visit to the village, Sunday flea market produced a fairly sharp cornered, aluminium pan for the princely sum of 20 Kroner. That's 10p a cm and still less than two quid in Olde Money. It was one of those old and solidly built pans. With two handles for lifting it off the range.
It took a bit of a search to find a non-standard, oversized 20cm +. Though they all taper to some degree this one doesn't much. Which I really like. It looks more the part when on the end of the telescope. Rather than a rather obvious, sawn off pan.
Now I just need to bore a large hole in the base to clear the inward movement of the drawtube. Then chop off most of the height. One in the eye for those who think nothing of spending hundreds of your local currency on a simple, CNC'd focuser adapter that's been dipped in a pot of anodizing. Mine's an 8" What's yours? 😉
Once I am satisfied with the dimensions I shall spin it in the lathe with a Scotchbrite pad to produce an evenly smooth finish. In the past I had the whole pan tilt to collimate against springs. Now I'm going to screw the pan to the end of the main tube and add a sturdy, 10mm[?] collimating backplate [with push-pull screws] on which to mount the focuser.
Stop laughing at the back, Philistines! 😊 Can you even imagine what it would cost to have a casting made and bored out to this size? The geometry and material of the pan provide all the stiffness without the weight. Success! A visit to the village, Sunday flea market produced a fairly sharp cornered, aluminium pan for the princely sum of 20 Kroner. That's 10p a cm and still less than two quid in Olde Money. It was one of those old and solidly built pans. With two handles for lifting it off the range.
It took a bit of a search to find a non-standard, oversized 20cm +. Though they all taper to some degree this one doesn't much. Which I really like. It looks more the part when on the end of the telescope. Rather than a rather obvious, sawn off pan.
Now I just need to bore a large hole in the base to clear the inward movement of the drawtube. Then chop off most of the height. One in the eye for those who think nothing of spending hundreds of your local currency on a simple, CNC'd focuser adapter that's been dipped in a pot of anodizing. Mine's an 8" What's yours? 😉 Once I am satisfied with the dimensions I shall spin it in the lathe with a Scotchbrite pad to produce an evenly smooth finish. In the past I had the whole pan tilt to collimate against springs. Now I'm going to screw the pan to the end of the main tube and add a sturdy, 10mm[?] collimating backplate [with push-pull screws] on which to mount the focuser.
Click on any image for an enlargement.
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