Thanks everyone for your thoughts and the info on the Optoma not being native. Budget wise they're all within scope.
Viewing distance wise it will be circa 4m and the PJ will be around 5m from the screen. Other kit currently it's a Yamaha 3040 receiver so an older model. Not sure if it can pass through the 4k or not.... so this would be a future upgrade therefore I wouldn't want that to be such a limiting factor to the decision making exercise.
Player wise this is up for discussion as I've not selected a 4k unit yet.
Thanks again for your thoughts.
Are you limited to just those models?
If the room is not treated then getting a projector with good blacks like the VW270 and the TW9400 will be wasting that feature.
Is the starscape a window?
Because if it is, it would let in a lot of light during the day and make projection very difficult if not impossible.
For screen size the projector should be used for a few weeks on a wall, or something attached to a wall to determine ideal size.
That being said, 120" from 4m/13.12' is a bit on the small side.
A very general recommendation is 10-12" inch in diagonal for every foot in distance. That would give you a screen of 130 to 155" screen.
Again, this is very general and subject to user preference.
There are 3 4K models that can be recommended in this scenario: Epson TW7000, TW7100, and TW7400.
From another thread:
The TW7400 covers DCI-P3 for HDR movies. The filter that enables the extra coverage cuts the brightness, but the unit should have sufficient brightness (in the dark).
The HC4010 has motorized lenses with memory for a 2.35:1 format screen. If your screen is not this format then this feature is not really useful.
The HC4010 has better lenses and other components and is a better movie projector.
The TW7000/71000 are brighter.
They have an 18GB HDMI chip. The HC4010 has a 10GB HDMI chip, so no 4K HDR 60Hz, 4K HDR (30)24Hz at the most. Most video is at 24Hz anyway, the 4K HDR 60Hz is primarily for gaming.
They are also lighter at ~12lbs, which the current mount might support. The TW7400 is ~25lbs. which would require a more expensive mount or a shelf.
Use these links for calculating dimensions:
Find screen size and throw distance for the Epson Home Cinema 3800 projector.
www.projectorcentral.com
Find screen size and throw distance for the Epson Europe EH-TW7400 projector.
www.projectorcentral.com
HC3800=TW7100
The TW7100 and TW7000 have the same specifications throw range wise.
Both have lens shift for easy placement, the HC4010 has more.
If the projector can be placed closer to the screen a DLP unit might be an option.
A small number of people are sensitive to a DLP effect called RBE (rainbow effect). You have to see a DLP projector to see if that is the case.
DLP's are better and handling motion.
The Optoma above would be an ok option for DLP.
Also the Viewsonic LS700-4K.
LG HU70LA 4K is a less bright.
The Epsons have something most DLP's don't, which is lens shift. Lens shift allow the image to be moved up and down, or the projector up and down, giving it more placement flexibility.
If the screen is going to be larger than 130", especially being AT, a brighter projector would be required, like the TW7100.