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Ok... Rokinon 135mm f/2 lens. I have a step down ring of 58mm on the front as an aperture mask. No clue what that brings my lens down to aperture wise. If I use a normal L-eXtreme filter will it work? Camera is a 294mc if that matters and the actual aperture ring on the lens well be set wide open at f2. Trying to get rid of those starbursts I got when stopping the lens down with the aperture ring to f4... Thanks! Benjamin |
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| Ok, I just went ahead and tried it. On the flame and horsehead I got signal, heart and soul I got signal, spaghetti nebula I got nothing in a test shot at 2 minutes and gain 400. So I think it works, not sure how much signal loss there might be but I'm not getting nothing... |
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Hi, With a 58mm step down ring you will basically get an aperture of 2.3. It won't much improve your results. Reducing the aperture in front of the lens will improve your stars shape (less diffractions), reduce achromatic aberrations, but won't improve the sharpness. From my experience, best results can be achieved by closing the front aperture with 49mm stepdown ring, resulting in a f2.7 aperture. You can also try by closing the diaphragm at f2.8 and compare the results. David |
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| @Benjamin DeHaven I have been shooting with Rokinon for the past 3 years with good success. I stop my aperture down to f2.8 for star qaulity and still get great signal. I normal shoot with a efw with LRGB and SHO narrow astronomik 6nm filters. As long as your band pass is greater than 5 nm with single or multiple pass , it should allow for band pass shift at this focal ratio. My narrow band subs using a 294mm are usually 3 to 5 min. Hope that helps -Brandon Below are examples with the 135 and 294 mc osc  RHO Ophiuchi Complex Complete Redo Edit  The Giant Blue Squid (aka The Blue Horse Head) Rokinon 135 MM OSC Here are examples of different narrowband images with the 294 m.  The Head of the Orion Constellation: Sh2-264 Angelfish Nebula HOO Rokinon 135 mm  The Head of the Orion Constellation: Sh2-264 Angelfish Nebula SHO Rokinon 135 mm  SH2-171 & 170 : A Questionable Post (modified SHO) Rokinon 135 |
