I have one of the Polaris 127 scopes also. Unfortunately, with the scope being what I call a boosted Newtonian, meaning the actual primary mirror has a very short focal length mirror and then a booster lens in the focuser, it is the most difficult scope I own to get a totally precise collimation on. By concept, the scope is known as a catadioptric, meaning that both a mirror and a lens is necessary to get a viewable image, like a Smidt Cassegrain, Maksutov Cassegrain, It is actually a very close cousin to a Maksutov Newtonian. Both a Maksutov Newtonian and our scopes have s short focal length spherical mirror and have a lens that makes all the corrections for spherical error, and a short focal length spherical mirror has a lot of that. The difference is that a Mak Newt has the correcting lens in front of the primary mirror, while our scopes have it after the secondary mirror, at the true focal point of the primary mirror. At that point, any slight error in positioning or in the angle the image cone deviates from exactly straight on, messes up the spherical correction.
The over-all scope roughly has a focal ratio of 8.0. The primary mirror on mine has a truly reflective diameter of 128mm by actual measurement and, to the best of my ability to tell, the focal length of the primary mirror is 450mm. That gives in a focal ratio of 3.52. The negative effects from collimation error, from information I have researched, goes up inversely to the square of the focal ratio. So the primary mirror is a little over five times more sensitive to collimation error than a true f/8 mirror. Then, the booster lens enters the picture with its own sensitivities to collimation error, which I have no idea how to calculate, even if I did now what the focal ratio of it is.
Getting rid of all the coma that you are seeing takes a lot of work and even more patience. At one point, when I first started working on mine....maybe three days into it, I was ready to throw the thing across the room, then stomp on it. The most likely problem is that the secondary mirror is not lined up exactly as it should be with the booster lens. I found several potential sources:
1. The position of the secondary mirror along the primary mirror's optical axis. You can move this back and forth using the center screw and the normal three collimation screws. The center screw works opposite the other three, allowing you to move the whole secondary mirror at a tedious pace. Once you make a move, you then get to redo the rest of the collimation of both the secondary mirror and the primary.
2. On mine, I found a base piece that has the screws for the finder (located on the inside of the main tube) has a smaller radius of curvature than the metal tube of the mirror. With the finder mounted tight enough not to move around, it tends to warp the optical tube. With the scope in its rings, mounted on the tripod, the error can be collimated out. However, do not loosen or rotate the optical tube in its rings or the collimation will be adversely affected. On mine, I took that piece out and shaved out some of the plastic to change the radius of curvature to more closely match that of the scope. I suspect that plastic piece is built for a 114mm scope, but is being used in the 127.
Another way of approaching this problem is to leave that part alone, and shim between the focuser base and the main tube. This is a trial and error process. I used pieces of cardboard from the back of a note pad for my experimentation.
3. The last item will probably not affect you when using the light weight eyepieces that come with the scope, but will if you use much heavier ones. This issue has to do with the way the draw tube (the tube the eyepiece actually fits in) is supported in the focuser body. There is a strip of slick material in the base of the focuser opposite the rack and pinion. This strip and the rack and pinion are the only contacts the draw tube makes with the focuser base. It is adequate for light eyepieces, but with heavier ones that I use, there is no support in a direction running perpendicular to a line from the existing support strip and the pinion. This situation is true in all entry level mass produced reflector scopes currently made by any company that you will find being sold in the world today.
What I did was to make some strips out of a file folder that had wax impregnated thin cardboard for its material. These were slightly wider than standard double sided tape. I alternated double sided tape and strips of the folder material, a couple layers of each to start with, down the length of the focuser base tube. There are three different places where I put the strips: One across from the rack and pinion "ditch" in the tube, and the other two on either side of that ditch such that they formed an equilateral triangle. There is a supporting strip every 120 degrees around the circumference of the tube. At first, I had a strip of double sided tape, then a strip of folder material, then double sided tape, then another layer of folder material. This worked for a while, until the materials compressed and the draw tube started wiggling (sideways) again. I opened up the focuser, pulled the draw tube out, and the lower level of folder material, being slick and being curved in a way it was not made, popped loose. This happened with all three of the combined strips, leaving one layer of double sided tape stuck to the focuser base material, and the rest of the material loose as three cardboard and tape sandwiches. I put an extra layer of double sided tape inside the focuser body, on top of the existing pieces, stuck the cardboard sandwiches back on top, and hurriedly put the draw tube back in place. During the draw tube insertion, I had some trouble holding the cardboard in place, as it wanted to slide some with the draw tube. Later, I had to do this whole thing again. Now there are three pieces of tape under the cardboard strips. There seems to be enough material in there now that the whole thing seems to be permanent. It is able to support my 82 degree Meade eyepieces well.
With some experimentation, I found that the light energy in the coma I was seeing was coming from light that was being reflected off of tube walls and other surfaces inside the scope that were not supposed to be reflecting surfaces. The intensity of the coma was also affected by the amount of haze in the sky that was reflecting light pollution back downward. I ended up buying some material normally called "flocking" or "light trap", which absorbs over 99% of the light that hits it. I ended up covering every surface except for a few screw heads that would require very small pieces. The flocking has a sticky back, but I did not want small pieces coming loose and falling on the primary mirror, so the screws were painted with flat black paint instead of shiny black. I also used a black sharpie pen (cone tipped and not the fine point) to blacken the bevels of the primary and secondary mirrors. I made the equivalent of a lens hood out of a gallon paint can, sprayed it flat black, then lined it with flocking on the inside.
By the time I was done, contrast was approaching that of a good refractor. The scope is now good to 225 or 250X on the Moon with my high end eyepieces and no Barlow lens. (4 to 5 mm eyepieces). The scope especially likes an old 4.7mm Meade 82 degree eyepiece...they don't make that any more.
The focal position for the booster lens in the focuser seems to be just right when observing the Moon. When looking at deep sky, the focuser has to be adjusted inward with just the lenses, which take it away from its best position. I found a 2X Barlow, a Meade No 140 (can only be obtained second hand) that requires about 5mm out focus, which seems to be just about right. With that particular Barlow, the scope is capable of splitting two six magnitude double stars with a separation of 1.1 arc seconds, which is about as good as a good refractor that size gets. On double stars and minimal haze, I do not see any coma on double stars at all. If the sky is really hazy, I will start seeing bits of it in some cases of really bright stars, but not the big stuff that makes a star look like a comet.
For deep space objects, resolution is not quite as good as I would like without the Barlow, but they don't call those "dim fuzzies" for nothing. I am keeping my eye out for eyepieces that have more back focus than most to sharpen the image a bit for deep space, but I am fairly content with things as they are.
Well, you probably do not need all of this, but once I opened the closet door, everything came spilling out. Just pick through the items and take what you want. If you have any questions, Holler!