Thank you, Rex and Cam. This capture has better focus than the other done in 2013 :
http://astronomia-e-astrofotos.10697...26-td1070.html
No, Kevin. My FOV is around 44.8' x 29.8' and at that day and hour Mars was very more distant.
The FOV is a big limitation of my set: 305 mm f/4.7 + GSO 2" Coma Corrector (with barlow effect of 1.14x), Skyglow filter with a little barlow effect and sensor Canon T3 (1100D).
My actual focal distance is around 1700 mm.
I can not to use focal reduction because of focal distance. With one of 0.5x 2" the camera Canon needs to be inside the telescope !
And I already did a cut of 35 mm of OTA, to get focus with standart set of Canon.
The thin OAG and filter wheel do this task more difficult !
Some DSOs only with mosaic ressource.