Reducer spacing to CCD

[Astroblagger]

Hello 

Im just wondering how critical the spacing between my Atik 460ex and sw reducer is i basically need a spacer T2 of 14mm i see ones that are 15mm on first light optics do you think that will be ok? or is it really that critical? 

[kirkster501]

At the focal length of a reduced ED80 - if that's what you meant? - I do not think it will be that critical withn a mm as long as you are thereabouts.    I did have your exact combination and sometimes I used to not bother with a certain spacer that put me between 1 and 2mm out and it didn't appear to make any difference to my eyes.  However, as you get shorter and shorter in FL with faster scopes and reducers allied with larger CCD chip sizes it becomes increasingly critical.  Indeed at F4 and lower even parts of a millimetre can make a difference, especially at the edge of the field.  There are members here, imaging at those FLs that have detected spacing inaccuracies to within microns.