My 20 inch dobsonian

[Bodkin]

A rather unusual, heavyweight dob. Luckily the wheels provide easy movement in and out of the barn.

[John]

Thats one serious looking scope !.

Was it manufactured or is it of your own make ?.

Do you find you need a light shroud with it ?

Thanks for posting the pic

[russ]

Very impressive looking scope. Being able to wheel it out of a barn definitely helps with a scope that size.

[Doc]

Unusual design at the bottom, tell us a little more about it please.

[Bodkin]

It was made for me by Barry at Beaconhill. I had bought a nice mirror some time before and decided that I fancied a truss tube telescope. It ended up being more Mount Palomar than than the Obsession-style scope I originally had in mind. However, I am very happy with it, though moving it any distance requires a van with a motorised tail-lift. Also, I could mount the tube on an equatorial, if I can find one that will cope with about 130kg!

I have a home made shroud of black nylon that does the trick with unwanted light, though it isn't too bad without it.

[russ]

That will be some mount that can cope with 130Kg.

How are you skies from home? If there is no real need to take it anywhere, it looks perfect. Certainly won't get blown around if there is a breeze.

[Bodkin]

The design at the bottom is a little unusual. Instead of the normal teflon and formica azimuth bearing, it has a two foot wide bearing that is used for things like a rotating car display. It has no problems with the weight of the scope, but doesn't give the feel of a top quality standard dobsonian design. It is the one thing I am a little unsure about, but Barry thought it was the best way to go.

[Bodkin]

Until a month ago the scope was in France at a very dark site. My wife and I are currently in London, so it is in pieces. However, we are hoping to move to mid Wales this autumn. A location that can accommodate the scope is a must.

[zedock]

What a beauty!!

[russ]

I bet the views through it from France were mindblowing. But Mid Wales will be a great location to get the most from the scope.

[Keiran]

Wow... very nice... and wales will be the ideal place for it, hope the skies stay cloud and rain free for you though

[michael.h.f.wilkinson]

Really nice. On the down side, my aperture fever is playing up again

[RobH]

Very impressive indeed

I just got hold of a 20 inch dob, and have considered asking Barry to build a lightweight rigid skeleton tube for the optics in order to use it as an imaging scope.....did you ask him specifically for this construction, or did you ask for as light a weight as possible?

I was thinking of aluminium for everything.

My mount will carry a lot, but not that sort of weight....for that you need a mountain instruments or AP3600 or similar, and they're a pretty penny!

Cheers

Rob

[Bodkin]

The truss tube approach was heavier than Barry's alternative; a simple aluminium skeleton tube. I am not sure on the precise weight of this one, but it is certainly quite a bit heavier than me. One of the problems is that the mirror cell is particularly hefty to ensure that the rocker box is not too tall. In all, I felt privileged to be able to specify something and see it come to reality. It was a sort of present to myself after thirty years of observing. Working with Barry on it was great fun too, though it took quite a time.

[RobH]

Thanks for that, very interesting.

I met Barry back in '87, and have talked on and off over the intervening years....lovely chap.

I'll give him a call and discuss it with him.

Cheers

Rob

[HD-AP]

Hi rob

I'm sure barry is your man to make you a lightweight alloy skeleton tube .

He made me one a couple of years ago it consisted of alloy u channel welded to several alloy hoops very light yet strong .

However i didn't like how it looked and my mirrors are heavy so i went with a true serrier truss design which although made from alloy weighs 2-3 times the weight of the old one.

Barry also constructed an equatorial fork for it ,which is so massive you could hang half a dozen people of it .an observatory instrument .

the base made from steel weighs hundreds of pounds but is stable .

see nottingham astronomical society's newtonian fork mounted mine is simular.

Alternative makers would be orion optics but that would be a solid rolled tube or david lukehurst.

Anyway like your dob wish you all the best with it's conversion.

regards

clive

[darkly]

That really is something else - nice one.

It would be something else to have it in its own observatory ready set up in your garden in wales, no wheeling around - just straight to viewing.

I am jealous of course !!!

[brantuk]

I think you need to join the dob users group - click the link in my signature below - nice scope

[Bodkin]

Thanks for the posts! The medium term aim is to set it up permanently and give free access to anyone who is interested, including any amateur astonomers holidaying locally of course. This will mean sticking to John Dobson's original ethos of a simple telescope. My main worry is how to prevent people from falling off a tall ladder. If anyone has any ideas for a viewing platform that would be safe for all ages please let me know.

[michael.h.f.wilkinson]

So is a 20" a cure for aperture fever?

[Bodkin]

It is for me I think, though this may change. At this size observing becomes more of a logistical challenge. The observing ladder is quite long and a fall could be painful so I tend to just pick a small area of the sky and stay put. Nevertheless, seeing stephan's quintet clearly and my first sighting of M101's spiral arms are experiences that will never leave me. What I did not expect was that I would spend as much time observing with my binoculars, six inch and ten inch telescopes as the 20 inch. Each has its own character and in the end observing for me has become less about ticking off targets and more about enjoying some quality-time with the universe.

[johninderby]

Hi rob

Alternative makers would be orion optics but that would be a solid rolled tube or david lukehurst.

Anyway like your dob wish you all the best with it's conversion.

regards

clive

Orion Optics does a 20" truss tube dob so they would have the parts needed, but probably wouldn't be cheap.

John

[michael.h.f.wilkinson]

It is for me I think, though this may change. At this size observing becomes more of a logistical challenge. The observing ladder is quite long and a fall could be painful so I tend to just pick a small area of the sky and stay put. Nevertheless, seeing stephan's quintet clearly and my first sighting of M101's spiral arms are experiences that will never leave me. What I did not expect was that I would spend as much time observing with my binoculars, six inch and ten inch telescopes as the 20 inch. Each has its own character and in the end observing for me has become less about ticking off targets and more about enjoying some quality-time with the universe.

Well put! I got myself a 15x70 this summer, and I use it as much as I use the C8. I am planning on getting something like 12-14" later, but do not intend to sell my trusty C8, precisely for the reasons you give.

[Beulah]

Thanks for the posts! The medium term aim is to set it up permanently and give free access to anyone who is interested, including any amateur astonomers holidaying locally of course.

:)

What about those who live close by?!

[Bodkin]

Absolutely. Nothing better than sharing the skies with neighbours.