No makers name but obviously Asian sourced, pretty sure it isn't Synta because of the finder bracket shoe.
Initially the view through it was AWFUL (caps on purpose), hazy, flowery, unsharp, poor contrast, a star test looked like a triangle outside of focus and a very fuzzy triangle inside of focus. Now I understand a 6" fast achromat will not give the greatest image on a star/planet or Luna, but this was way out.
I tried flopping the lens elements around in all combinations and found the front element had been installed backwards. That improved things but the view was still bad, stars were seagulls everywhere.
I noticed if I pulled the front element away from the rear (made tabs of tape) the image got steadily worse so I decided to thin out the spacer between the elements. The factory spacer in this case was a 9 thou (.009) thick plastic ring. I removed it and put in its place three evenly distributed pieces of Scotch tape (1.5 thou, .0015). This improved the image dramatically, bringing the scope into the realm of what I was expecting (sharp, some false color on bright objects).
Unfortunately this also allowed the center of the elements to touch each other (rainbow pattern in the center that expanded and contracted as you pressed on the front element) so tonight I am trying two layers of Scotch tape (for 3 thou, .003, 1/3 of factory spacing). I will let you know the results.
By the way as I was testing the new thin spacer material, and as I had tabs attached to the front element, I tried rotating the front element in relation to the rear in 15° increments. There definately was a position where a stars image was optimized, so if anyone is experiencing less than pinpoint stars you might want to try this. Just put a piece of tape shaped so a portion sticks up as a tab on the front element near the edge (so you can have some rotational leverage). Loosen the clamping ring (most scopes with this kind of issue will have a dew shield that just pulls off thus exposing a plastic ring you can loosen with your fingers). You need to make sure the spacers between the elements don't fall out or re-position themselves (they usually are stuck on one element) and also to make sure the rear element isn't just moving with the front. Usually there is a piece of dust on the back element that you can use to judge this. Don't worry about the tape damaging the coatings, todays coatings are very hard and a little lighter fluid on a cloth will clean up any residue. Of course I marked the sides of the elements (sticker with pen drawn line) to note this relationship. While you're in there you should paint/magic marker the sides of the elements.
So what I need to figure out is the focal length of this OTA. I am sure there are simple ways to do so but I don't know what they are. Can anyone advise?
Also, the scope is fitted with a 1.25" visual back that screws into the large adapter that screws into the focuser tube. The focuser tube is 2-15/16" OD (is this considered a 3" focuser?). The part that threads into the focuser tube has 2.825" fine threads. Might this be some sort of industry standard such that I can find a 2" visual back for it?
The part that screws into the focus tube has T-mount threads (interesting...) that the actual 1.25" visual back threads into.
Thanks in advance for any and all input.