Merlin66 wrote: ↑Sun Apr 08, 2018 2:08 am
Whoooo You're very lucky to be able to test so many PST etalons!
In my experience over the past ten years, the PST etalon has a 10/80/10 quality distribution.
10% should never have left the factory
80% are, well, "OK" and do the job - just!
10% are excellent and give tremendous potential for mods.
Just my 2c
Hi Ken,
Hah! Your distribution curve reflects my experience. I have looked through many PST and I tried more than 30 of them to find the one which is as good as our friend Jean Pierre Brahic works with. And I found 3 samples that are excellent. One of them is same good as two others, but not so luminous - requires about 2x longer exposure time which is very critical to image with high resolution with a larger aperture telescope(s).
Two others from these three leave nothing to wish better - unless they will be just larger in aperture! These are very luminous and with my older BF10 Coronado (somewhat rusted), DERF, 2x Barlow, IMX174 and on a typical SCT - allows 2-2,5ms exposures with a mild gain. This is enough for high resolution - short enough to freeze the seeing and quick enough to get a good fps speed - enough frames within a movie cadence.
These two may be still not as narrow as Jean Brahic's one, but very close behind. I was not able to find better than these two.
And one of them is for Alfred Tan - here is the picture taken with this etalon installed on my C11 telescope. It is easily seen how narrow this etalong and how good it's finesse. Too bad Meade can make all the PST etalons this good.
Valery
"Solar H alpha activity is the most dynamic and compelling thing you can see in a telescope, so spend accordingly." (c) Bob Yoesle.
Largest full size 185 - 356mm Dielectric Energy Rejection Filters (D-ERF) by ARIES Instruments.