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jetstream

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jetstream last won the day on July 8 2019

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About jetstream

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  1. My "best newts" have 19%-21% obstruction but they also have vg optics on vg mirror cells that will cool and collimate easily. I've played around with a truly non scientific experiment, going from 19% to 37% obstruction using various scopes. Up to about 25% all seems well and 30% and up shows contrast loss on the moon, on certain size features. All optics have .91 Strehl or higher.
  2. I just focus other TV EP's using the PCII after setting it up for a 21E- or any other TV EP.
  3. My 24" and the Delos do not produce eye reflections for me- YKSE, a respected member here mentioned lens cleaning in that CN thread- have you tried cleaning this eyepiece?
  4. I have tried piles of eyepieces and the Delos has never done this eye reflection- my 10mm Luminos was famous for it. Do you have a link to the CN thread?
  5. As long as there is enough room when the screws are partially backed out it should be able to be skewed in either direction and tape is a good idea. The OP could line the scope on something with the finder screws loose a move it to see if it lines up and how much is needed. Obviously there there is no burr or plastic moulding holding it out?
  6. In the long past John I've used shims to align hunting optics because of poorly drilled mounting holes. You can use anything thin for the shim- I used to have dedicated brass shims made just for this but any thin plastic or even paper, matchbook cover can be used. It can be placed just on a quarter of the shoe at the front or back depending on the direction needed. Usually only a very thin shim is required to skew the finder to work.
  7. yes, perceived by us. The actual contrast is fixed between the brightness of the sky and the object. As we use filters, up mag lower mag it changes how we see things through the system.We are trying to "please" the brain so to speak.
  8. I believe there is a "range" of exit pupils that work, somewhat based on the individual. I can't give a mathematical reason or physics reason but it boils down to the tradeoff between magnification and image apparent brightness through the eyepiece. Too much mag will kill a filtered view, way too dark. The wider pass UHC lets more light through so a bit more mag can be used, the Hb less light so less mag and is much more fussy. Hbs have a narrow exit pupil range around 5mm-6mm- my VX10 shows the HH easily at 5.2mm exot pupil, stray a small amount from this and it disappears. Go up and the HH gets small in the EP, go down too dark. Blackwell and Clarks ideas at play. For others: contrast is a fixed between the brightness of the sky and the brightness of the object. The only variable in our control is the darkness from which we observe from.
  9. ie my 24" f4.1/PCII @1.15x gives f4.7 which is close enough to compare my nominal f4.8 15" to. Using the same 20mm eyepiece for a ~4mm exit pupil the 24" gives 125x mag the 15" 91x mag, the difference in views is huge.
  10. FOV? Going from 40x to 50x at the same (appropriate) exit pupil is huge regardless of the FOV IMHO.
  11. Thinking about this I recall finding the dot can be challenging at times and we need to be in the right spot physically for it to work right- I assume the OP is lined up himself? My Rigel will throw "ghosts" in the screen when viewing off axis. Shim?
  12. More mag at the same eye illumination in general. Mag matters ie Blackwell and Clark and eye illumination matters as we all know. This is pretty much it IMHO and its hugely important again IMHO.
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