As I slowly piece together the dob structure for my 16" Royce conical, I have been playing around with spider designs, which has raised for me an interesting question.
It has been reported that wire spiders seem to yield less diffraction/scattering than conventional straight veined spiders of equal thicknes. It has been furthermore argued that this is largely due to the veins cooling to sub-atmospheric temp, and thus introducing an optically active boundry layer of cooler air.
But another thought occurs to me. Is it also possible that conventional veins - painted flat black - nonetheless reflect a significant amount of light at very low angles of incidence, therby increasing light scatter. (Recall that reflectance rapidly increases as angle of incidence decreases)
To check this out I took one of my protostar spiders and viewed a light source, holding the spider in proper position in fron of my eye. Despite the flat back finish, at this low angle of incidence, a surprisingly bright line of reflected light emerged along the vein.
I am wondering then: 1)Is the absence of such reflection in a wire spider (With far less surface area to refect such incident light) part of their advantage?
2) Are there better ways of blackeneing spider veins, without significantly increasing their thickness.
With regard to this last question, I have tried roughening the surface of a vein with sandpaper and then repainting. No good, with light source at low angles of incidence - as occurs in lunar, planetary mode - no improvement.
Thoughts?
Joe
It has been reported that wire spiders seem to yield less diffraction/scattering than conventional straight veined spiders of equal thicknes. It has been furthermore argued that this is largely due to the veins cooling to sub-atmospheric temp, and thus introducing an optically active boundry layer of cooler air.
But another thought occurs to me. Is it also possible that conventional veins - painted flat black - nonetheless reflect a significant amount of light at very low angles of incidence, therby increasing light scatter. (Recall that reflectance rapidly increases as angle of incidence decreases)
To check this out I took one of my protostar spiders and viewed a light source, holding the spider in proper position in fron of my eye. Despite the flat back finish, at this low angle of incidence, a surprisingly bright line of reflected light emerged along the vein.
I am wondering then: 1)Is the absence of such reflection in a wire spider (With far less surface area to refect such incident light) part of their advantage?
2) Are there better ways of blackeneing spider veins, without significantly increasing their thickness.
With regard to this last question, I have tried roughening the surface of a vein with sandpaper and then repainting. No good, with light source at low angles of incidence - as occurs in lunar, planetary mode - no improvement.
Thoughts?
Joe
16" F5 "Front Collimating" mirror cell
