Week three of first telescope and Astrophoto, Reducer question

[jerfish]

I purchased my first Telescope three weeks ago yesterday. The first picture is from a week ago in May using Celestron nexstar 6SE, stock star diagonal, Nikon D90 DSLR, 2x barlow, and stacking 500 frames with registax at 40% limit. The second one is from May 14th using same setup but with a neximage 5 with no barlow and 1000 frames at 40% limit. The third one is from last night, May 15th, but now with a focal reducer/corrector and losing the star diagonal (again no barlow). My question is, why the difference between may 14th and the 15th? Last night's image floored me, and that was a quick stacking without spending much time and I have a few other vids to try yet, may be able to boost quality. Is it 1). the focal reducer 2). losing the star diagonal 3). the night quality 4). luck 5). all of the above????? I'm extremely happy with the last three weeks and that image especially. Then I put away the laptop and did a little, well, stargazing. Saw Iota cancer (lovely two colors on that binary!), ghost of Jupiter as a little cloud in the periphery of my eye, castor, and a bunch of others. A meteor even streaked as a meteorite just to top it off. Awesome. What an awesome three weeks!