Gina's Mini Dome Observatory for Widefield Imaging Rig

[Gina]

Yes, that was one idea but more work that a 3D printed one.

[Horwig]

Can i please make a suggestion, and I'm fully prepared to be shot down in flames. Since you have started considering something along the lines of the skypod, why not a clamshell?

Since you are looking at two foot dia, you would get away with three sections not the four in the photo. All three of slightly different dia, so they slide into each other, and then if they all open in the one direction, there's no difficult vertical seal at the top.

How are your fibreglass skills Gina?

Edited May 3, 2017 by Horwig
can't spell

[Gina]

I am happy to consider any suggestion   My NEQ6 mini observatory used a form of clamshell but cylindrical rather than spherical.  It also used relatively heavy aluminium and 12mm marine ply.  With the fork mount I can get away with a 24" spherical covering which is 3D printable and hence very light.  The 2 part horizontally rotating system fails due to lack of upwards view.  A conventional dome is complicated.  So your suggestion could be the answer   It is much easier to drive an axle - even concentric tubes - than a "middle-missing" ring gear, let alone two of them!

Regarding glass fibre construction, I have done it in the past but wouldn't want to do it again - the fumes are horrific!!

Edited May 4, 2017 by Gina

[wimvb]

How about this simple setup? Came across it in the indilib forum

http://www.indilib.org/forum/general/1014-post-your-indi-setup.html#7313

Sure looks simple enough

[Gina]

I am going to investigate the clamshell system.  See how it can be sealed etc.  If the dome axis is east-west there is a wide angle of operation available.

[Gina]

10 minutes ago, wimvb said:

How about this simple setup? Came across it in the indilib forum

http://www.indilib.org/forum/general/1014-post-your-indi-setup.html#7313

Sure looks simple enough

Yes, I've seen that one before in a thread on here.  It doesn't allow imaging down to the horizon though.

[Gina]

Here is a diagram showing a cross-section of dome and mount.  Dotted lines show the range of possible dome movement.  The 0° line is where the dome wants to open to allow imaging down to the southern horizon.  The other limit that dictates how far the sections can open is the mount support at 304°. 

If two sections were used the farthest the dome could open would be 152° with the two section stacked against the mount support.  This is almost enough  and might be a possibility if the PoleMaster was suitably mounted.  The question is whether I would want to do any imaging that far north - it is above the trees but only just.  To allow for this possibility three roof sections would be required.

 

Edited May 3, 2017 by Gina

[wimvb]

Yes, found it too:

If you have a somewhat higher roof/lid, the scope can sit a bit higher as well, allowing imaging down to the horizon. But imaging to the north is more difficult.

[Gina]

This is not a standard dome where the imaging rig must always be within the roof space, this roof opens right up and as long as the rig is parked suitably, the lens hood could project above the line of the "dome".  This means that the dome axis could be below the rig pivot level allowing a clear view not only to the south but to the east and west too (though trees to the west limit the view in that direction.  As shown in the modified diagram below, two sections should be enough.

[Gina]

Here are cross-section diagrams showing the roof open and closed with lips on the sections keeping rain out when closed.  There is only one moving part.

Edited May 3, 2017 by Gina

[Gina]

Um...  The design above is not right!  The base gets wet!  I'll try again...

[Gina]

For the roof to open the moving part must be the smaller section  this presents a problem with sealing.

[Gina]

If I use three sections for the roof - one fixed and two moving the sealing is sorted out.  Each section is a little over 90°

Edited May 3, 2017 by Gina

[Horwig]

49 minutes ago, Gina said:

If I use three sections for the roof - one fixed and two moving the sealing is sorted out.  Each section is a little over 90°

That's the one, now could you print one of about 2.5 meters for my obsy?

[Gina]

That would probably keep my biggest 3D printer busy for the next five years

[Dr_Ju_ju]

Another thought.....

Add a Laser cutter to your big printer, then you can cut acrylic sheet, which could then be formed into a dome with welded edges....

 

[Gina]

Interesting thought Julian

Next to do some 3D modelling...

[Dr_Ju_ju]

I think another Gina project coming on....

I bought one of these http://www.ebay.co.uk/itm/445nm-2-5W-2500mW-Blue-Laser-Module-With-Heatsink-For-DIY-Laser-Cutter-Engraver-/322497845897?hash=item4b165e9a89 then together with a Mostly Printed CNC machine (https://www.vicious1.com/assembly/ & http://www.thingiverse.com/thing:790533) but obviously any machine that can move X & Y (Z movement to achieve fine focus), can be used.

Control of the laser is done with the 'hot-end cooling fan' control, 10% to switch it on & 100% to cut...

 

[Gina]

Basically the design for the moving sections is the same as the dome twin horizontally rotating parts plus the fixed section with hubs and lips added.  Then there's the south side fixed part which I think is just curved in one plane and could be aluminium but I'll need to model this to confirm.

[Gina]

13 minutes ago, Dr_Ju_ju said:

I think another Gina project coming on....

I bought one of these http://www.ebay.co.uk/itm/445nm-2-5W-2500mW-Blue-Laser-Module-With-Heatsink-For-DIY-Laser-Cutter-Engraver-/322497845897?hash=item4b165e9a89 then together with a Mostly Printed CNC machine (https://www.vicious1.com/assembly/ & http://www.thingiverse.com/thing:790533) but obviously any machine that can move X & Y (Z movement to achieve fine focus), can be used.

Control of the laser is done with the 'hot-end cooling fan' control, 10% to switch it on & 100% to cut...

 

Could be   I already have a CNC machine in mind for later.  Do you know what that laser will cut?  I would imagine only fairly thin thermoplastic and possibly thin wood.  I think the unit would need a fume cabinet or other fume extraction system.

[Dr_Ju_ju]

I've used it to cut 3mm acrylic & copper pcb's, not tried anything else yet, I use it in a well ventilated room, but not in a fume cabinet.

[Davey-T]

I got some parts made out of 1mm stainless steel recently, laser cut and a very neat job, not much more than the cost of buying the stainless steel.

Just sent off a drawing.

Dave

[Gina]

I've modelled the closed clamshell as closely as I can in SketchUp.  The moving parts are modelled in one piece and the fixed part slightly smaller.  There remains the other fixed part that is attached to the fixed clamshell piece and goes up under the moving part.

[Gina]

These diagrams show where the extra fixed parts go.  I've yet to work out how to model the actual shape of these.

[Gina]

I'm printing some scale models of the pieces on my Pilot printer so that I can see how things look.  I'm afraid SketchUp has beaten me in modelling the extra parts.  I probably wont print them anyway unless I can't use aluminium or plywood.