Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schiefspiegler,60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4" f/12, 4.5" f/16 & 6" f/12 Schupmann Medial refractors, 4" Celestar, 19 Stellafane awards 9 in optics Engineering = Taking what you have and making what you need.
-philip doutreligne -ETX 90 -Orion Atlas mount -70/1300 coronagraph -Kutter catadioptric Schiefspiegler 200/4000 -102/1500 white light solar refractor http://users.telenet.be/philipdo
Quote:hi Alex, yes the two lens are plano-convex. you can test them with the négative disk (wich one have realised this lens) you polish the negative disk to get a spherical mirror and you place the two lenses under a Fizeau control with monochromatic light. (sodium lamp) + three paper holds among which more thick one to create finges. the deformation of the front lens is not very important, you can be satisfied by a spherical one...at F/15 or F/20 the second lens have to be aspherised, very difficult to do ! all my coronographs have been designed by a specialist wich worked with Bernard Lyot ! all the elements are optimized, also the position of diaphragm. A good coronograph must have less lens as possible (ideal 3 or 4) +h-alpha filter 5Å i dont know the Rondi's model, sorry, but i think it's also good...
Quote: - The second lens (called lens of field) is much more difficult to realize that the first one(night) because smaller and more open. She too, must be surfaced in the micron before being cut. His(Her,Its) diameter (65 mm) is rather important for having the biggest possible field, its opening is 2.15 (raw(gross) drilled glass BK 7) A hole of 5 mm a summer realized by the company(society) before cutting the lens, what avoids the breakage at the end of polishing … The work of size is rather painful, because of the very pronounced curvature and quite as the main lens, it is necessary the asphériser with a tool in crown.
Quote:I made a coronagraph based on DAVIDG design a few minor changes my blocking cone is covered in 24K gold to reflect IR - it stays a lot cooler
Ed Jones ........... The best data is an interferogram, the best analysis is from an honest optician.
Quote:Philippe that's an awesome prominance shot! Dave: Where do you get narrow band Ha filters? How much?
Quote:Quote:Philippe that's an awesome prominance shot! Dave: Where do you get narrow band Ha filters? How much? Ed, My prototype used an Andover filter with 10A bandpass. They are about $300 but Omega optics on Ebay has them from time for about 1/2 that. You just need to be sure that the filter is visual grade vs sensor grade. The sesnor grade filters will show multiple images. If the sky is very clear and the optics scatter free you can see proms with a coronagraph with just a red eyepiece filter but that takes really clear skies. I tried a couple of 10nm (100A) bandpass filters but I couldn't see proms with them from my location. If the bandpass drops down to 1.5A you don't need a coronagraph just a scope working at F/30 and the proper energy rejection filters along with 1.5A filter. So inexpensive 60mm f/15 refractor and 2x barlow works pretty well. - Dave