I received a GSO 12" F/5 last fall around the Mars opposition as I was looking for cheap, large aperture, and an excellent mirror
The huge box arrived and appeared in descent condition but the OTA did have a couple small dents in it. Otherwise, everything appeared in good condition.
The focuser is the " LB upgrade" (Linear Bearing Crayford Focuser) but to be honest, while it does work okay, it doesnt feel like a great focuser. And for the price I guess that is to be expected.
The mirror takes a while to cool but it does include a fan. During the few times I have used it I dont think its ever been fully acclimated. Star testing appears to show slightly softer rings on inside focus and well defined outside focus.
I used a Ronchi eyepiece to check the mirror and I see straight lines, no signs of astigmatism, or TDE. Pretty sure I can identify TDE from my Orion 8" F/4.9 mirror. You can see the curve at the edge of the mirror.
I see zero of that in the GSO.
I've been wondering how good the secondary mirror is on this newt as I've read that they are the weaker link in some of the cheaper newtonians.
Another thing a little off with this one is the primary mirror cell can be shifted slightly as the screws dont appear to hold it well. I did try to tighten them but for the weight of that cell/mirror and the tubing, its just borderline useable/tolerable. I find I have to point to my object, then collimate and enjoy. If I move the scope in another direction my collimation is off again a little.
Does anyone know where to purchase 14" diameter tubing that might be better support? I'd spring for that if I could find some but I dont know where to get it. And I think I would prefer aluminum or metal.
At the tail end of the Mars opposition last fall I did get a few good images. I cant wait to try it on Jupiter and Saturn once they get higher.