20" f/4 Dob build

[swamp thing]

1367187604[/url'>' post='1917273']

Nice

I've got a partially finished 10" mirror and a 16" blank laying around for years. The 20" doesn't look too unmanageable so I may get around finishing the 10 and 16 off some time in the distant future

I will put up some pictures of it next to my 10" Dob at some point, that should give you some idea of scale.

[Daniel-K]

wow steve looking great

[Optical Dob]

Looks fantastic Steve. Can you knock me one up for next week thanks

[swamp thing]

1367449407[/url'>' post='1920750']

Looks fantastic Steve. Can you knock me one up for next week thanks

Cheers buddy.

You order the parts and we'll see what we can do eh?

[swamp thing]

Started on the rocker box this evening. Cut out all the panels, and started on the dovetails. After cutting all the tails, I started on the pins. Hmmm! That bit'll be blunt then Pick up another cutter tomorrow. Should get the rest of the pins cut at the weekend.

The outer 5/8 ply will be dovetailed with the inner 3/4 ply biscuit jointed or doweled. Judging by how strong the mirror box is, this should be incredibly strong. Keeping the scope boxes as rigid as possible should make high power tracking a synch, with zero play and flex.

Any movement should be transferred through a rigid structure straight to the bearings rather than being soaked up by flexing boxes, only for the scope to rebound when pressure is lifted.

This, I've always seen as important in a large scope after using cheap chipboard and MDF large Dob mounts that just don't cut it IMO

I'm also thinking of a prototype wheelbarrow idea with a single wheel at the front, this is only in my head at the moment but having one wheel will make it much more manoeuvrable when negotiating doorways and other obstacles.

[estwing]

learning form errors its what's it about..on a big scope like yours steve..you want the piece of mind that its been done right and by the sound of things its bang on mate.

[Rustysplit]

A "Dyson Dob" would bring much kudos

[swamp thing]

Just finished all the dovetail pins for the rocker box. Here is the box before assembly.

Here it is together. Not glued yet though it has to come apart to do some more work on.

[estwing]

thats a mighty box..did you tidy the garage,or just shut the door steve!

[swamp thing]

Tidied the garage of coarse.

[mapstar]

Looks a fantastic job, and makes me get itchy hands thinking about starting a build myself!!!

[Moonshane]

looking great Steve. Am I reading it right that you are laminating 18mm sheets on the inside of the box shown? that would indeed be a very strong box - just right.

I love the look of the dovetails. might try them again on my current project. as with anything it's the setting up that takes the time.

[swamp thing]

That's correct Shane. I may be over engineering it, but better to be too strong than too weak.

I am very pleased with how the dovetails have come out. Routing them gives a very manufactured look. Which I like.

It seems many people struggle to do these with a router. It does require a little care, and a sharp bit

As I've said before, if you keep the dovetails large and the pins small, you should be okay

[swamp thing]

Here's the rocker box with the laminated 3/4 ply on the sides. The bottom is 1.5" thick. One strong little box.

I've cut out the alt bearing seats, sanded the outside. Here she s with a coat of varnish on. Four more to go. The inside will be mat black again as it can be seen inside the mirror box.

I'll try and get it set up next to my 10" Dob later today and get a pic to give you some idea of scale.

Nearly there now. Just the ground board, feet, and some laminate etc

[swamp thing]

Here's the few pics I promised of it set up next to my 10" dob for scale. My 10" has an oversize tube and is probably closer to an 11" or 12" with a regular tube.

It will need a few more coats of varnish on the rocker box before its the same shade as the mirror box. Hopefully get that done in the evenings this week.

[crashtestdummy]

wow nice build.what the eyepiece heigh of this at zenith?about 7 1/2ft?

[Rustysplit]

Beautiful work Steve. Not long now!!

What diameter are your trusses? Did you decide on heat shrink or anodising?

[estwing]

..."its alive,its alive!..you've created a monster...that will destroy you"..call it Frankenstein,pls steve!! lookin awesome

[swamp thing]

1367949755[/url'>' post='1926740']

wow nice build.what the eyepiece heigh of this at zenith?about 7 1/2ft?

No, not that high. The focal length isn't that long (80")

1367950388[/url'>' post='1926760']

Beautiful work Steve. Not long now!!

What diameter are your trusses? Did you decide on heat shrink or anodising?

These are 1.5" trusses. I'm gonna go with heat shrink..........I think still not sure TBH

[mapstar]

First light will be one hell of an event.Fantastic build and thread.Well done

[Moonshane]

great build mate - looks totally rock solid.

[swamp thing]

Cheers guys. Today was the first time I put the scope together on my own, it was actually easier than with help.

I remember reading David Kreige,s comment that a well built 25" scope can be set up by one person in about ten minutes, or if he has help, about half an hour

This would seem to be very true.

[Naemeth]

Steve, I didn't realise Apple made scopes .

[Moonshane]

I thought it was an Apple Mak but now I realise it's a newt - an iDob.

[Optical Dob]

Looking great Steve. Makes me want to get back into woodworking. Looks as solid as a rock.