Ok, here goes. A barlow lens increases magnification by making the apparent F ratio of the telescope higher. Being a minus lens it makes the primary mirror, or objective lens appear farther away. Wondering if it does anything for contrast. It is well known that higher F rations give objects better contrast. Wondering if the apparent F ratio increase with a barlow lens can do the same? Reason for question is I'm leaning towards a low F ratio OTA for photography but, it would be used on occasion for visual observing, hence a barlow in the focal path for contrast, if that works.
Barlow lens and contrast
Started by MikeN202od, 04/11/2020 02:41AM
Posted 04/11/2020 02:41AM
Opening Post
Posted 04/11/2020 03:13AM
#1
I don't believe you'll see an increase in contrast but along with an increase in the magnification of the eyepiece you're using in your fast OTA, you'll likely see a decrease in the comatic aberration at the edge of the field, similar in effect to a coma corrector.
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