Focusing a webcam with Baader Barlow

[Vox45]

After getting my Baader clickstop and its barlow (see unboxing here) I was able to screw the barlow directly onto the webcam (demo here) nosepiece. I  then did some daytime tests on a pinwheel (no, not M101 but a real one some distance away) and here's what I got:

(1) Using a diagonal without the barlow

(2) Using a diagonal with the barlow

(3) At prime focuse without the barlow

(4) At prime focuse with the barlow

Observations:

(1) the sensor was dirtier than I realized ! so I cleaned it with a coton swab and 90% alcohol. You can see the difference in pic #1 (after) and pic #2 (before)

(2) using a diagonal inverts the image up/down but does not change left/right. Prime focus inverts left/right but does not change up/down. I was convinced that prime focus inverted up/down/left/right... learned something there

(3) I feel that when I use the diagonal, the object appears to be smaller on the sensor (pic #1) than when using prime focus (pic #3). I assumed that the diagonal would add to the focal lenght, thus making the object larger ? I feel I misunderstood some concepts there

Question on focusing:

I had the hardest time focusing when using the 2.25x barlow. Is this expected ? Does the fact that I screwed the barlow into the nosepiece has something to do with me having problem focusing ?

That is it for now, feel free to comment on this