Making a glass optical dome for all sky camera

[Stefan Buda]

Originally Posted by Leo.G

I figured it out, it's one of those off axis rotational chucks used on milling machines. I've yet to purchase one. I'm yet to weld up a stand for a milling machine which came as an attachment to a lathe. I purchased a separate cross slide table and the milling machine still sits in it's box until I get a suitable stand welded up. I didn't want it bolted to the lathe when I read the notes stating it may either need packing to fit properly or, machining of the milling machine upright mounts. That would have been a big pain so I purchased a separate compound table to set it up as a stand alone machine.

It is an ordinary dividing head, tilted upwards. Very useful for generating spherical surfaces.

[Stefan Buda]

Mission accomplished!
I have two polished domes and two unbroken blanks left.

[Rainmaker (Matt)]

Originally Posted by Stefan Buda

Mission accomplished!
I have two polished domes and two unbroken blanks left.

Excellent work Stefan !

[Leo.G (Leo)]

They look amazing mate!

[Stefan Buda]

Thanks Matt and Leo!

Now I have to figure out how to mount them.
I'm thinking of gluing each into a 2mm deep groove using polyurethane or silicone rubber.

[bratislav (Bratislav)]

Originally Posted by Stefan Buda

Thanks Matt and Leo!

Now I have to figure out how to mount them.
I'm thinking of gluing each into a 2mm deep groove using polyurethane or silicone rubber.

No groove. Make a step where outside is flush with glass bottom, so any water runs away, not inside. And machine/print that area to slope down, to drain water away.

[Terry B]

Now you need to find away of stopping dew when using it.

[Stefan Buda]

Originally Posted by bratislav

No groove. Make a step where outside is flush with glass bottom, so any water runs away, not inside. And machine/print that area to slope down, to drain water away.

The reason for wanting to use a groove is that I think this way I can avoid turning the gluing job into a mess. If I put just the right amount of glue into the groove, spread evenly around, and then put the dome on, hopefully the glue will just fill the space between the glass and the metal plate without oozing out. I also want to drop three short pieces of wire into the glue, at 120 degree locations, prior to inserting the glass, to act as raisers.

Originally Posted by Terry B

Now you need to find away of stopping dew when using it.

I'm hoping that the RPi will generate enough heat to keep dew away.
That seems to be the case with the ASV prototype, but that one is in a plastic housing with a plastic dome and my version will have aluminium housing with a glass dome. I may have to add insulation to the housing.

[Leo.G (Leo)]

The aluminium housing will draw (and hold) the cold won't it?
I guess if the Raspberry Pi emits enough warmth it will counteract the cold.
There's always a Peltier cooler used on the reverse side but it would likely steam the glass up. I think last time I played with one I may have burnt my finger on the hot side.


Still, the domes look amazing and I can only imagine how much work went into making them.

[Stefan Buda]

Leo,
The ASV prototype ASC is reporting a Pi CPU temperature of 38 degrees at the moment while the ambient temp is about 10 degrees. So, I think there is plenty of heat being generated inside the housing. It is just a matter of managing it so that the whole thing doesn't overheat on a hot summers day.

[Stefan Buda]

I mounted the domes using black silicone rubber.
The groove is only 1.5mm deep and I used 3 tiny u shaped spacers at the bottom of the groove, made from 0.4mm diameter nichrome wire.

[Leo.G (Leo)]

They look amazing but seeing some of the other things you do I shouldn't be at all surprised.
Still, I worked in the industry (glazing for a short period of time which was still too long) and had to polish the pencilled edges on large sheets and the slightest twist and you have a large sheet of glass now in little shards on the floor and an angry boss. The diamond grinding wheel pencilled the edge, the cork belt/wheel polished it to a clear edge.


I even have a circle cutter here I've never bothered trying out because unlike the movies it's not as simple as scribe a single line then pull the centre patch out. I learnt how to do that and it involved a lot of scribe (cutter) lines and a lot of broken glass, including occasionally the one I was trying to cut the circle out of (mainly for exhaust fans in old people's homes (aged care)).


But the ability to cut glass has come in very handy over the years.

[Stefan Buda]

Originally Posted by Leo.G

I even have a circle cutter here I've never bothered trying out because unlike the movies it's not as simple as scribe a single line then pull the centre patch out. I learnt how to do that and it involved a lot of scribe (cutter) lines and a lot of broken glass, including occasionally the one I was trying to cut the circle out of (mainly for exhaust fans in old people's homes (aged care)).


But the ability to cut glass has come in very handy over the years.

I can barely cut straight lines and won't even contemplate circles, so I'm lucky to have a shop nearby where they make all sorts of glass art objects.

[Leo.G (Leo)]

I've in the past repaired a leadlight cabinet from the 1940s I used to keep my camera collection in. All freehand cutting of some quite complex shapes along a marker line traced on the glass to keep it as original as possible.


Since then my once young son (Turns 30 in 13 days, HOPEFULLY (severe depression)) put a toy truck into a panel and I simply covered the crack line with silastic so no sharp edge for him to cut himself on and while in storage till I get to redo the few cracks a cat knocked a suitcase over and made a huge mess of several panels.
One day, maybe.
I'm not lazy I just don't get to half the stuff I should get to with chronic migraines on a daily basis. No actual shed to work in doesn't help, not everything can be done in the yard and the house I rent is way too small to do it in here.

It's actually a valuable cabinet if I get to doing the work.