Al....a fact 'oft lost on camera lenses is they are not APO objectives.
They are designed for non-point sources illuminated in daylight.
You will find by using a UV+IR block filter and 2-3 F-stops, some very tidy camera lens, wide-field results are possible...such as here...
http://www.atscope.com.au/widefield/m16m17hXp.jpg
Baader and others make UV/IR block filters & they are well worth including in your CCD imaging train.