yes, i have. calculating it in advance only yielded an approximate value, the true FL was measured by comparison with other known FL eyepieces (i literally measured the size an object had in the image, at 100%, in one eyepiece and the other, and multiplied by the ratio i found between the two)
@DavidMFChapman well, you can try for the 30-40 RDP. the 30mm lenses have ~120mm FL, and the 40mm ones have ~160mm FL. spacing usually takes into consideration the optical center along the lens axis, so this might be a little bit of an estimate, rather than a true measured value. however, i could tell you the spacing at the edge of the lenses (~5mm), and from the lens thicknesses then derive the optical centers. the 30mm ones are 8-9mm thick, and the 40mm ones are 12-13mm thick (some doublets were thicker, some thinner)
@@Items_I_Find_Interesting i start by measuring the geometrical features of each lens, and based on that i model the entire assembly in CAD, where i carefully design the size of the spacers so that at least 1-2mm will result between each pair of opposing glass surfaces (also taking into account thermal contraction for the 3d printed spacers)
i"m not sure exactly what you mean by "holders". all lenses are housed inside the eyepiece bodies freely, spaced apart by some 3-4mm thick rings that are also 3d printed (like the rest of the casings). so, effectively, the entire eyepiece acts like a lens holder :) not sure i managed to answer your question properly
@@DK-df2hi well that i could do :) however, the inner diameters depend greatly on the actual lens diameters. and so in some cases the final print can turn out to be perfect fit, in other cases either too tight or too loose. so, that's why it is pretty tricky to do so, as it's not exactly universal solution. plus, it matters what kind of filament one will use - not all have the same contraction coefficient, so the dimensional tolerance will need to be adjusted accordingly.
@@DK-df2hi with 3D printing technology being so easily available to the general population, it would hardly be profitable to sell anything 3d-printed :) unless you have your on 3D print workshop (which i don't - i just design the parts, then i send them to a friend who owns a printer).
pretty hard to tell :) most of these were giveaways, some of them i bought as second hand / used / damaged units (i'm talking about the host binoculars, where these lenses came from). so, i guess you can scour ebay for such things, or local SH market (like OLX or similar - depending on your location)
Very well done! And great video graphics. I made one of these myself with 4 identical achromats from 2 unrepairable binos.
Did you measure the effective focal lengths? I have been working on formulae to calculate EFL from the focal lengths and spacing of the achromats.
yes, i have. calculating it in advance only yielded an approximate value, the true FL was measured by comparison with other known FL eyepieces (i literally measured the size an object had in the image, at 100%, in one eyepiece and the other, and multiplied by the ratio i found between the two)
@ I would be interested in applying my formulae to your designs if you could supply the parameters: four focal lengths and three spacings.
@DavidMFChapman well, you can try for the 30-40 RDP. the 30mm lenses have ~120mm FL, and the 40mm ones have ~160mm FL. spacing usually takes into consideration the optical center along the lens axis, so this might be a little bit of an estimate, rather than a true measured value. however, i could tell you the spacing at the edge of the lenses (~5mm), and from the lens thicknesses then derive the optical centers. the 30mm ones are 8-9mm thick, and the 40mm ones are 12-13mm thick (some doublets were thicker, some thinner)
How do you figure out the spacing between the lenses? Thanks
@@Items_I_Find_Interesting i start by measuring the geometrical features of each lens, and based on that i model the entire assembly in CAD, where i carefully design the size of the spacers so that at least 1-2mm will result between each pair of opposing glass surfaces (also taking into account thermal contraction for the 3d printed spacers)
Really appreciate the video. Can you document more about building the holders for the lenses.
i"m not sure exactly what you mean by "holders". all lenses are housed inside the eyepiece bodies freely, spaced apart by some 3-4mm thick rings that are also 3d printed (like the rest of the casings). so, effectively, the entire eyepiece acts like a lens holder :) not sure i managed to answer your question properly
Could you make the files you send to the printer available
If you could mass produce lens bodies and describe some good designs they might sell well enough on eBay
@@DK-df2hi well that i could do :) however, the inner diameters depend greatly on the actual lens diameters. and so in some cases the final print can turn out to be perfect fit, in other cases either too tight or too loose. so, that's why it is pretty tricky to do so, as it's not exactly universal solution. plus, it matters what kind of filament one will use - not all have the same contraction coefficient, so the dimensional tolerance will need to be adjusted accordingly.
@@DK-df2hi with 3D printing technology being so easily available to the general population, it would hardly be profitable to sell anything 3d-printed :) unless you have your on 3D print workshop (which i don't - i just design the parts, then i send them to a friend who owns a printer).
where can i find these kind of lens like this?
pretty hard to tell :) most of these were giveaways, some of them i bought as second hand / used / damaged units (i'm talking about the host binoculars, where these lenses came from). so, i guess you can scour ebay for such things, or local SH market (like OLX or similar - depending on your location)
thank you@@mihaisaiph1