This is another very low hanging fruit, which would immensely increase the usability of the S50 with a trivial amount of development effort. The ZWO boilerplate statement "It's on the todo list, but do not have an estimated date yet", which can be translated to "don't hold your breath, the chances of this happening before your S50 reaches its end of life are slim to none" is simply not acceptable.
You may think my position as a bit extreme, but think about it a bit, how many years do you expect to use the S50? My expectation is 2-3 years at most, and one year has already passed - any feature or improvement that happens beyond that is irrelevant to me. Also, some you you might be younger and wouldn't mind waiting, if you are in that group listen to the song Time by Pink Floyd https://www.youtube.com/watch?v=yl-Ms_ek-kE and you will better understand what I mean.
Getting back on topic, even without any kind of scripting and automation, the fact that if you are not literally there (and awake) to press the big red button and stop enhancing you will not get any image at all is simply mind boggling. Wasting hours of your customer's time and increasing their level of frustration is never a good business plan. This impacts not only the mosaics, which can take many hours, but even individual images, in fact anything with an exposure time of more than 10 minutes should have some kind of autosave feature built in.
Since I promised more constructive criticisms, here is my suggestion: no matter what kind of imaging you do, individual pictures or mosaics, Sun/Moon/Planetary, save an intermediate copy of the FIT and JPEG files every 5 minutes of accumulated exposure time. To minimize wasted disk space keep only the last five copies and delete earlier ones. This does not require any changes in the UI, no advanced testing or anything like that, it is literally ten lines of code. If ZWOs developers are overloaded while working on new features and do not have time for this, hire an unpaid intern and have him or her do it and everybody will be better off - ZWO would have a better and more competitive product (I am still waiting for my Dwarf 3 by the way, but I expect it will arrive before Christmas), every single customer will be happier to have autosaved backup images and not have minutes or even hours of their time completely wasted, and the intern will gain valuable experience.
Of course, it would be nice to have some kind of user control over the time increment and number of copies kept but that's icing on the cake - I would understand ZWOs statement for that request, it's a new feature, it requires UI changes, needs to be planned, implemented and beta tested so "It's on the todo list, but do not have an estimated date yet" would be an acceptable, or at least understandable response. But not having some kind of really basic autosave feature, after more than one year since the product was launched I do not think it is acceptable.
