have you tried the skywatcher ones, shown in the video ?
will contact my local makerspace, about creating a binoviewer below 300g in weight.
http://www.makerspace.org.uk
Woodhornbirder...
No, unfortunately, I have not tried the Skywatcher binoviewers in the video. The only binoviewers I have tried are the William Optics and Televue Bino Vue.
I started with the William Optics binoviewer--they showed me enough to get me hooked--I wanted better optics so I tried the Tele Vue Bino Vue with Tele Vue 40mm plossl eyepiece twins--the views kept getting better with my observing patches--then I threw more money at the setup with a William Optics GTF81 5-element triplet APO.
The WO 70 mm doublet Ed scope (6-lb refractor scope) delivered the magnification and resolution I wanted in my nature views--however, it lacked the color rendering I was used to with my better binoculars. The WO GTF81 5-element triplet APO (8-lb refractor scope) delivers great color rendering to my eyes.
Weight--one of the down issues about binoviewing--but a binoviewing setup is portable--just not as portable as a pair of binoculars or a light spotting scope on a light tripod--and you need a good tripod and mount.
All in all--I am finding I prefer binoviewing to mono viewing (single eyepiece) for several reasons. A person just needs to experiment and settle upon a setup and enjoy their own type of nature observing. Nothing is perfect with binoviewing--that is for sure.
I am still tinkering with my preferred setup within my budget and abilities to grab and go--or maybe two or three grabs--need to stay close to the car for the two or three trips. Therefore, if a person prefers to observe nature in solitude--as I do--where I park my car needs not be a long hike.
Fortunately, I have some nice views from the front window in my home. Others I know have nice views from their back porch or yard. But if you do not have those views close to home--keeping the setup light is one of the keys to an enjoyable setup.
Regarding your quest for a 300-gram binoviewer--I wish you luck with the suppliers there in England--if you are successful, please make some posts to let us know how it goes.
...Bob