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16" f4 Orion Optics UK Dobsonian Project

Moonshane

By Moonshane
in DIY Astronomer

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Moonshane

Moonshane

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cheers Mark and Alan

yes, the Meade would possibly be a lot taller as it's f4.5 (so about 8" more focal length) and also as the bearings are smaller, the base needs to be much taller. my base is only 22" high including the ground board and feet.

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MjrTom

MjrTom

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Ah cheers Shane, I realise I have been assuming the Meade was an f/4 not f/4.5. I must have been thinking about the skywatcher one maybe. :)

There is definately something magical about looking through one of these big Dobs :D

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Moonshane

Moonshane

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Ah cheers Shane, I realise I have been assuming the Meade was an f/4 not f/4.5. I must have been thinking about the skywatcher one maybe. :)

There is definately something magical about looking through one of these big Dobs :(

I think the SW one is f4.4 but the base is a 'little' wider at 34 inches compared with my 21 inches and I suspect a 'bit' heavier.

I am loving having a big scope again. :D

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  • 1 month later...
Moonshane

Moonshane

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finally got round to fitting my fan.

I used a cheapie 80mm 12v fan off Ebay - about £5 delivered and it works a treat.

First I made a baffle from some thin ply I had in the shed (a common theme - I never throw anything away that might be useful in the future). I am informed that it's important to have a baffle otherwise there's a danger the fan will just recirculate the same air and not blow it up the tube.

This was made to fit my cell and had an appropriate aperture for the fan and holes for the fixings etc.

I sprayed it matt black with a can I had (yes in the shed).

then I fitted the fan with some M4 countersunk bolts and checked all me connections before soldering and using some heat shrink on the joins. there are some foam blocks between the baffle and the cell to reduce vibration (although this is a low vibration fan and very quiet) and the whole thing is held on with cable ties for convenience.

The wire is long enough to connect directly to the 7ah 12v battery that will power it and will sit in the base of the dob.

I had previously made a tube cover for the bottom end from black garden matting (guess where from) and some elastic (from Morrisons!). This works in a number of ways - it allows air in and out, stops insects and spiders and also acts as a filter for the fan.

the whole thing works very well and you can certainly feel the air flow up the tube.

here's some pics.

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Moonshane

Moonshane

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well, the fan works well and no issues after a prolonged run tonight. no obvious adverse effects during use (no vibration etc) other than a couple of mini scares and exlamations of 'what the!!??' when my fingers touched the fan during collimation! I am never sure about the better seeing aspect of fans but it certainly go the scope to an observing status much quicker than previously. so, it's a good result!

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MjrTom

MjrTom

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Time for a fan grill I think. :)

John

I probably have one or two kicking about in the house in my box of PC parts if you want one for the cost of a Jaffa cake or two :)

Will have a look for you and PM you if I find it.

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  • 5 years later...
Moonshane

Moonshane

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Well, I thought I'd resurrect this thread as my next phase of evolution is about to begin. Although I can just about get the scope as one unit into my car, I am usually towing the caravan as I use it as my main dark site scope and need to consider loading positions and weights for safe towing. That said, I hope to use it more often (not used it in anger really for a year or so) and hope that this project will encourage that too.

So, what I am planning is a little scary but really quite simple, a split tube dob. Similar and somewhat inspired by 

I have ordered some adjustable toggle clamps and also a spare tube ring to I intend to use the top ring of the two currently attached to the alt rings to be the bottom 'collar' and the spare attached to the top half of the tube as the other collar. I will then have two half tubes of approximately the same length and it will allow me to put the top one (which will be light) inside the van and the other in the back of the car but with the weight forward of the rear wheels like a passenger (possibly even on the back seat). I am debating whether to use rivets or bolts to fix the position on the tube rings and edging toward rivets for now. I can use the two rings either side of the jigsaw to act as a guide channel to ensure a straight and square cut.

I hope to end up with a job a bit like the really neat effort in the thread linked above. The overall cost to do this should be about £10.

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