Hi All,
I tried M15 a few nights ago but this time with a X2 barlow - I wanted to see how it compared with my image from about a week ago that was at prime - effective focal length 1500mm.... Imaging at this FL is a whole lot trickier than just imaging at prime.. Focusing is really tough & I lost lots of frames due to movement even though exposures were only 6 secs. The image is a bit fuzzy... I think full moon & lack of guiding didn't help but I suspect collimation & focus was off. I don't think longer focal length gained me anything...Anyway image below along with my earlier (wider field) for comparison.
Cheers, John
(http://homepage.ntlworld.com/john.punnett/graphics/oas/m15_X2barlow.jpg)
(http://homepage.ntlworld.com/john.punnett/graphics/oas/m15.jpg)
I like the non barlowed version because it shows the two bright stars which are really vivid in colour.