Do we know for sure if ALL lenses used in the erector tube are apochromatic or achromatic??? Or are there a combination of these types that make up the sum total of glass in any particular scope? Objective and occular would definitely be apochromatic lenses.
If there are any achromatic lenses used, it will give varying resolution to colour wavelengths in differing light intensities, which really goes hand in hand with temperatures, ie: cold mornings/evenings and hot mid days.
Apochromatic lenses are specifically designed to reduce/eliminate the error in focal length being discussed. The effort and expense gone to to use them in a rifle scope can be all wasted (for our FT rangefinding purposes) if just ONE achromatic lense is used in the erector assembly.
Also, temperature can affect the apochromatic glasss and layers to cause dispersion/refraction and manifest as the errors discussed. Cheap lenses = more shift, expensive glasses designed well = less to no shift.
Last edited by greyskullnz; 12th March 2013 at 06:10 AM.