Making my own Dob mount: Easy/hard/not worth it?

[pipnina]

My EQ2 mount for the SkyWatcher 130 is annoying me to the ends of the earth. It can't point close to the zenith because the tube/slow-mo collide with the mount, the dec slow-mo has limited movement (it runs out going both ways, very annoying) and it's very... wobbly. Add to this that I'm not intending to do imaging with anything but my DSLR for now and I really don't think the EQ2 is good for me.  All od this could have been avoided in the first place if I'd done more research but I'm past that point now...

To the point: I'd like to build a dobsonian mount of my own to get my 900mm SkyWatcher 130 off its current crummy mount. How would I go about designing and building this? I understand many DIY dobs are made of wood; how will I make sure the scope can turn on the azimuth without sanding itself? How will i keep it in place? How will I adjust for the earth's rotation? And most importantly will this be worth it both in terms of usefulness and saving money?

At some point (when I'm a little more well off) I'll be looking at getting a 250/300mm dob anyway, but that's probably a year or two off from now.

    Opinions on the matter appreciated!

            ~pip

[JamesF]

It's not hard given access to a few woodworking tools and there are quite a few examples posted here.  If you browse back through the DIY section for a while you'll probably find dozens of examples.

James

[ronin]

Look through these see if anything appeals:

http://www.scopemaking.net/

http://stellafane.org/

http://www.garyseronik.com/

[Ajohn]

I'd hope that an eq4 would cope with a scope like that but best let some one else comment. Frankly I feel some of the mounts shouldn't be available but scopes tend to be sold at various budget levels rather than on the base of usability - that applies to bigger ones too really.

If you build a dob I suspect you will want to put it on some sort of stand to raise it up some what as it may be rather low to use. Personally I am not too thrilled with dobs for higher magnification use. To me an equ mount with a star drive is not all that far off essential and the equ aspect a lot more so. The latitude can be set by eye on the scale, levelled, pointed north and the whole thing swung round or the adjustment used until it tracks to an acceptable level for visual use.  People with dobs often get interested in equatorial platforms for them at some point. There main gain really is in the bigger and bigger mirror area but there are complications such as the one I just mentioned.

It's worth having a look what is around on here, this one for instance

http://www.astrobuysell.com/uk/propview.php?view=96856

Earlier versions of the GP-DX's crop up as well. People used to put F6 10in newtonians and bigger on those along with a short tripod or pier - well past what they were intended for really. There is also a goto version about. It's a bit noisy - stepper motor ticks and all bronze gears - but easy to use.

A lot of the shake you have is probably down to the tripod. It usually is. There is a thread on here on making timber ones. I think Beconhill sell some tripods but you would probably need an adapter. I recollect seeing the Tal wooden tripod  offered there but don't know how good it is.  Actually there are several good rigid older mounts such as the meade LXD 650 and 750, both usually goto  but I have never seen one for sale. Also the one that they used on the cardboard tubed newtonians - it was even used on 16in scopes.  I've looked at several of the 1/2 fork mounts that are about. Mixed feelings personally and in any case probably not up to your length of scope.

There are a lot of alternatives but the need for a decent mount eventually crops up with most people.

John

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[pipnina]

Look through these see if anything appeals:

http://www.scopemaking.net/

http://stellafane.org/

http://www.garyseronik.com/

I've had a look at http://www.scopemaking.net/dobson/dobson.htm and I'll suggest it to my dad. Because it's held together mainly by gravity, I guess it's going to be very easy to assemble. Although my scope is 20mm less in diameter than what this is designed for so I'll need to alter the design slightly?

This should be fairly easy to build, though, looking at it.

I'd hope that an eq4 would cope with a scope like that but best let some one else comment. Frankly I feel some of the mounts shouldn't be available but scopes tend to be sold at various budget levels rather than on the base of usability - that applies to bigger ones too really.

If you build a dob I suspect you will want to put it on some sort of stand to raise it up some what as it may be rather low to use. Personally I am not too thrilled with dobs for higher magnification use. To me an equ mount with a star drive is not all that far off essential and the equ aspect a lot more so. The latitude can be set by eye on the scale, levelled, pointed north and the whole thing swung round or the adjustment used until it tracks to an acceptable level for visual use.  People with dobs often get interested in equatorial platforms for them at some point. There main gain really is in the bigger and bigger mirror area but there are complications such as the one I just mentioned.

It's worth having a look what is around on here, this one for instance

http://www.astrobuysell.com/uk/propview.php?view=96856

Earlier versions of the GP-DX's crop up as well. People used to put F6 10in newtonians and bigger on those along with a short tripod or pier - well past what they were intended for really. There is also a goto version about. It's a bit noisy - stepper motor ticks and all bronze gears - but easy to use.

A lot of the shake you have is probably down to the tripod. It usually is. There is a thread on here on making timber ones. I think Beconhill sell some tripods but you would probably need an adapter. I recollect seeing the Tal wooden tripod  offered there but don't know how good it is.  Actually there are several good rigid older mounts such as the meade LXD 650 and 750, both usually goto  but I have never seen one for sale. Also the one that they used on the cardboard tubed newtonians - it was even used on 16in scopes.  I've looked at several of the 1/2 fork mounts that are about. Mixed feelings personally and in any case probably not up to your length of scope.

There are a lot of alternatives but the need for a decent mount eventually crops up with most people.

John

-

While at some point I'm likely to end up with an EQ mount, I don't think I'll need one for a considerable amount of time. When I find a job, though, you can be sure I'll be saving for something lovely in the scope department.

[Joseki]

Hi, I'd say it was worth building btw, especially if you or someone you know has a few tools.  Depends on what you have lying around but cost might be a low as £20 for a sheet of plywood (but costs tend to escalate).  

I've had a look at http://www.scopemaking.net/dobson/dobson.htm and I'll suggest it to my dad. Because it's held together mainly by gravity, I guess it's going to be very easy to assemble. Although my scope is 20mm less in diameter than what this is designed for so I'll need to alter the design slightly?

This should be fairly easy to build, though, looking at it.

btw, all your dimensions come from your telescope tube.  (as is discussed in "The Dobsonian telescope" book, "epilogue: making a small telescope"), start by making the wooden box (cradle) part of the mount that the telescope tube fits in.  Make this about 1/8 " larger internally than the telescope tube (later wedge the tube in place with cardboard).  Make the radius of the circles (azimuth bearings and base) about 1.8 times the radius of your mirror.  Once you've made the cradle find where the balancing point is with your heaviest eyepiece and finderscope etc attached (or you can just guess at the start - it's simply easier to balance when the tubes in the cradle with side bearings attached).  This will allow you to work out how tall the rocker sides need to be, though with the 130 you might want to make it taller than needed. 

edit: those plans online suggest using particle board.  Most people use plywood.

[MAN or ASTROMAN]

I  can't understand why no manufacturer produces ready made Dobsonian mounts.You have to buy the whole shooting match.A ready made would be ideal for us cackhanded folk.Speaking of which-it's Bank holiday Monday- I bet A&E departments are on alert for DIY inflicted injuries!

[Cornelius Varley]

This one looks simple to make http://www.homebuiltastronomy.com/downbino/HomeBuiltAstronomyProjects-KidPeekII.html