It seems that amateur sized domes have been sidelined by much cheaper RORs.
Yet RORs offer little real shelter for the visual observer but do enjoy a bigger window on the sky.
At its most basic: An observatory is a building which opens to give a [fairly] unobstructed view of the sky.
It can be thought of as an adaptable weather shield. This is usually achieved by rotation and opening observing slits.
Most of the internal structure is to support the weatherproof shell and the resulting wind/snow loads.
If the shell can be arranged as a self-supporting skin then no other structure is required.
This is the basic GRP or moulded plastic dome usually found in smaller "amateur" sizes.
It is usually provided only a few construction panels sealed and bolted together.
Using GRP [fiberglass] as a weatherproof cladding over a heavier structure seems strangely illogical IMO.
The GRP would be far better arranged as a series of connected mouldings to achieve a suitable shell.
The supporting structure becomes merely superfluous weight and considerable extra expense and time consuming.
The downside is the thickness of the GRP shell required as dome size increases.
The Calf Igloo is a dome in every sense and remarkably affordable at 4.2m Ø or 14' in real money.
It comes in three curved and cleverly designed panels but has the disadvantage of considerable weight.
This hardly matters if the dome is to be power driven and properly supported on suitably low friction rollers.
No doubt the CaIf Igloo could be got moving by human force alone.
Just a good shove to overcome its inertia and considerable moment.
The one advantage of a gored dome is the ability to have complete drops from zenith to base ring.
However, the very [hemi]sphericity of a dome is a grave disadvantage using thin, stiff and flat materials and amateur tools and skills.
Custom car builders use forming "wheels" to literally curve flat panels but there can be few dome builders willing to go that route.
Which brings us to trapezium and triangular cladding panels of traditional dome shapes.
These provide the desirable, basic curvature for the [supposed] minimum material consumption of the basic hemisphere.
Trapezoid panels are far more user-friendly to the amateur builder who requires a sheltered window on the sky. Most do!
The tetrahedral type enjoys theoretical geometrical strength in comparison but requires a far more competent and creative builder.
The tetrahedral structure can be built lighter and in considerable sizes with the minimum of tools.
The downside of both is sealing the myriad panels. Many of which will be lying almost horizontal.
Any building with an asphalt roof covering requires structure to support the considerable weight and low strength.
As does roofing rubber. Think heavy! Think about the weight and thermal issues before embarking on a black 'felt' roofed dome!
From my own experience of building a trapezoid dome from wood and birch ply I'd seriously suggest an alternative.
Build one out of standard aluminium profiles and clad it with full drops of aluminium sheeting for weatherproofing.
The design readily lends itself to mass production and requires no special tools NOR ANY PANEL CURVATURE.
Even the base ring can be made multi-sided out of straight strips of metal with overlapping joints.
Laser or water jet cutting would provide a smooth ring if desired but the straight sided "gores" won't fit it without adaptation.
All that is required is a narrow, unobstructed, circular track for the support rollers. They won't know it's a smooth ring.
So have the base ring cut multi-sided too if you can afford it.
I used 16 sides and four tiers of panels @ 3m or10' diameter. This size is easily managed by a one man band with basic skills.
The ease and speed with which an all aluminium, trapezium paneled dome can be built should be obvious.
The trick is to ensure geometric accuracy to avoid cutting any individual component to size.
The barrel dome is also an obvious contender for the amateur's observatory.[See images above ;^]
Though it requires the edge profiles be rolled to a curve the covering panels are easily and gently bent without spherical distortion.
This observatory shape has the huge advantage of lots of headroom at "the shoulders" for observers on stepladders.
The flat ends could provide a normal doorway if erected directly on its base ring on the ground.
Surely an obvious candidate for the Newtonian/Dobsonian owner compared with any "normal" dome on a wall?