Useful astronomy links for reference I have included here . They cover a range of subjects from Planetariums to processing software and are all free

http://astronomy.tools/calculators/field_of_view/   Field of View calculator based on camera , scope  combination

http://www.stellarium.org/     Planetarium

http://apod.nasa.gov/apod/astropix.html    Astronomy images

http://www.astrobuysell.com/uk/     Astronomy buy and sell

http://www.ideiki.com/astro/      Canon camera control

http://starizona.com/acb/ccd/advimnarrow.aspx   Image processing

https://www.gimp.org/        Free download image processing software

http://dso-browser.com/    Night sky object suggestions based on location etc

http://www.howardedin.com/articles/fov.html  Designed for Canon , gives Field of View with all camera / lens combination

http://deepskystacker.free.fr/english/index.html  Stacking and post processing software

 https://www.reddit.com/r/astrophotography/comments/2acnqb/the_great_list_of_astrophotography_software/    A comprehensive list of all usefull astronomical imaging software . From image processing, Capturing ,EQMod and Planetary software. Free