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lux eterna

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About lux eterna

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  1. John Herschel, what a coincidence. Interesting. Addictive yes, not understanding is like a never ending itch. Also the brain needs a little exercise now and then. Thanks.
  2. The inverse function was unknown to me, that is where I got lost but now I can see how to proceed. The coming days will be occupied with Excel exersices - a perfect corona timekiller. Thanks a lot for explaining !
  3. No, I am not sure how to interpret this. I was just thinking like 10 to the power -1 equals 1 / 10. But not sure if that is applicable here.
  4. @AKB Thanks, I think the answer may be there. I just have to spend a little time with it. @vlaiv To look up RA/DEC conversion to Alt AZ and use altitude component is not an option. I need to do the math from scratch (the reason for this is an Arduino based project). From your post : 1) sin(alpha) = sin(delta)*sin(phi) +cos(delta)*cos(phi)*cos(HRA) 2) sin(alpha) - sin(delta)*sin(phi) = cos(delta)*cos(phi)*cos(HRA) 3) cos(HRA) = ( sin(alpha) - sin(delta)*sin(phi) ) / ( cos(delta)*cos(phi) ) 4) HRA = arccos( ( sin(alpha) - sin(delta)*sin(phi) ) / ( cos(delta)*cos(phi) ) )
  5. Hi all, My trigonometry and mathematics skills are not quite up to this task, so I would appreciate if someone can show me how to proceed. I am trying to design a formula that can tell at what time the sun reaches a user selectable elevation (aka altitude, not to be mixed up with declination). For the specific case of alt = 0 (sunrise/sunset) I have found a formula that looks good except that I need solar altitude as an input variable. An example: At what time will the sun reach -18 degrees (under my horizon) for a specific date, at a specific location ? I have found two very in
  6. If you are interested in general photography as well, I would recommend Photoshop. If (when) you are ready for the next steps, there are some handy plugins for PS, some are free while some are commersial (noise reduction, green tint removal, star fixing, vignetting removal etc etc). After many years with PS, I took the step to PI, but I still need PS. I only use PI for the first steps, and it still makes me wonder how you can design such a non-intuitive user interface. On a learning curve scale from 0 - 10, I would put PS at 3 and PI at 15. Ragnar
  7. @tooth_dr This is an example, in "mask mode" I did Image-Adjustment-Brightness/contrast and inverted the mask (ctrl-I). This particular adjustment is "curves" but you can use the techniqe with whatever adjusment type you need. Ragnar
  8. I found this guide https://www.donastro.org.uk/basic-layer-masking/ This "image-as-mask" method can be used in different scenarios, one is selective stretching, another selective colour manipulation. I use it the most for selective noise reduction (targeted for the darkest areas = inverted mask ( = "ctrl-I" )). Remember that you can adjust contrast & brightness etc of the mask while you are in "mask mode" (ctrl-click on the mask thumbnail). Even a gaussian blur of the mask can be done here. You can also use a brush here to add / remove parts of the mask (but that is often better done
  9. I like the natural look, relaxing for my eyes. Ragnar
  10. This is good, but there is so much potential with layered processing using masks. I often use a workflow like @BrendanC described, I just want to add a tip: The overstretched image above is just perfect to use as a mask. If you invert this mask (galaxies are black), editing will not do much difference to the galaxies. Ragnar
  11. Can I have two please ? (what an idea... I love it !) The outer halo is very clear so this is promising. Ragnar
  12. Nice catch with the diffuse surrounding areas clearly visible. On my screen I see a little magenta bias so I gave it a try in PS to get a bit more colour separation (colour contrast). Used curves, selective colour, HLVG and hue/saturation (hope you dont mind). Ragnar
  13. It does not make sense with 4 + 3 pin connectors to each motor for just 4 channels used. What could be the reason to that ? Ragnar
  14. Hi all, About a year ago, I got the idea of making a portable mount without need for any counterweights. The main design is (almost) an English Mount with two tripods supporting a rotating bar pointing towards NCP. This is very stable, but one of the 6 legs must just barely touch the ground - otherwise it is not. A slider on a M6 threaded bar is pulling a braided fishing line that is connected to a "windshield wiper" type arm, which is anti-backlashed with a adjustable torsion spring. The lower tripod can easily be replaced with some kind of base kit that fits on a sturdy table or
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