Andrew et.al., Finally got a bright star just before it went over roof zenith out of window around 8:30 PM.
The Ronchi screens (2 different) that I made worked fantastic!. One with a film can the other wrapped on phenolic and hot-glued inside an empty EP. Subsequent test showed it doesn't matter(as you said)whether it is hand held outside or inserted except for scope stability and ease of viewing.
This is the test results(explained)..... The heavy dark lines going from 6+ down to 1 are SOooo close to straight GOING FROM EATHER SIDE OF FOCUS.... that it is extremely difficult to distinguish between them as you pass thru focus. The average "teeny-tiney" slight variations due to heat waves along the edges prevent noticing any difference in change before and after focus point.
I have the "trace impression" that outside of focus, the dark lines MIGHT be ever so slightly slimmer in the center.
The point of all of this is..... 1 to 5 extremely thin diffraction lines exist between the heavy dark lines ON BOTH SIDES OF FOCUS. These diffraction lines increase their NUMBER as you approach critical focus and the heavy lines get fewer. See the drawing, I think I may have a 1/8 or better, overcorrection(?) objective from Celestron.
It is really that hard to compare inside and outsde of focus. :-) :-) -Now I need a professional Ronchi for sure! -Larry
The Ronchi screens (2 different) that I made worked fantastic!. One with a film can the other wrapped on phenolic and hot-glued inside an empty EP. Subsequent test showed it doesn't matter(as you said)whether it is hand held outside or inserted except for scope stability and ease of viewing.
This is the test results(explained)..... The heavy dark lines going from 6+ down to 1 are SOooo close to straight GOING FROM EATHER SIDE OF FOCUS.... that it is extremely difficult to distinguish between them as you pass thru focus. The average "teeny-tiney" slight variations due to heat waves along the edges prevent noticing any difference in change before and after focus point.
I have the "trace impression" that outside of focus, the dark lines MIGHT be ever so slightly slimmer in the center.
The point of all of this is..... 1 to 5 extremely thin diffraction lines exist between the heavy dark lines ON BOTH SIDES OF FOCUS. These diffraction lines increase their NUMBER as you approach critical focus and the heavy lines get fewer. See the drawing, I think I may have a 1/8 or better, overcorrection(?) objective from Celestron.
It is really that hard to compare inside and outsde of focus. :-) :-) -Now I need a professional Ronchi for sure! -Larry
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