So, we did it. The team went around last night to give this rare beast a thorough shake down along side my 20" f5 with exquisite craftsman figured optics.
Despite the appalling weather of late, the sky was beautifully clear and the seeing very good. Not perfect but certainly the nicest I've seen in a long time. From early evening, my SDM was resolving all six of the four stars of the trapezium even on low power views!
So to the Stargate. I was amazed by the mirror. It's not 'normal' by any means, but in fact a composite conical-ish affair with glued vanes between two disks of glass. The largest disk is of course the f4 optical surface and the smaller rear disk allowed the mirror to be attached to the mount and provided the surface against which the collimation screws would rest. I have to admit to thinking 'that's never going to work'.
In the pre-dark sky we star tested against some brighter stars and noticed something a little strange; the airy disk pattern had a noticeably pinched look to it and tool a slightly triangular form. Hmm. Checked the collimation screws, all seemed ok. When focussed the stars were tight but the effects of scintillation showed some asymmetric spikes. The optical error was actually very slight, and unlikely to be noticed at all to the less critical eye, but it was certainly there.
But then something interesting happened...
We continued to observe into the evening, enjoying wonderful views of the Great Orion Nebula showing plenty of colour and bags of lovely contrast befitting a light-bucket, and we started checking out the globulars and galaxies there to entertain us. And it became evident that the mirror was performing better and better as the night progressed. Each time we bothered to de-focus the scope and check the airy disk, it was rounder and rounder. By mid evening, the mirror had reached thermal equilibrium and the image was quite perfect, with text book airy pattern and absolutely pinpoint star images. The mirror was certainly so good in performance that it was difficult to distinguish the view from my SDM that has a mirror that would cost new about the same as the whole of the Stargate!!!!
So, we can certainly conclude that the optics are indeed excellent but just remember that they are only performing at 'very good' until the primary has properly equalised. There are pre-cast positions for three cooling fans in the base. I suggest filling them if you get one of these.
Mechanically, the scope more than met my expectations. The whole thing was solid, held collimation all night, and slewed and tracked perfectly well. One thing that surprised me was how well it works in manual mode. Slip the clutches and it's very smooth and perfect for just cruizin'
So all the features of a traditional dob at half the cost. Yes there are compromises and shortcuts, but you get a heck of a lot for your money.
Nice one Skywatcher, it's a keeper
BTW: It's f4, so there is a ton of coma. My Paracor fixed that perfectly and the stars were tight right across the fov. Factor it into the cost, you really need it!