Barlow lens and contrast

Started by MikeN202od, 04/11/2020 02:41AM
Posted 04/11/2020 02:41AM Opening Post
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.
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.
Posted 04/15/2020 06:48AM #2
I like the Powemates


http://www.televue.com/engine/TV3b_page.asp?id=53