The is a crop from a 170 min. integration of 60 sec subs. 585mono, Ha 6nm, simple histogram stretch.
I only see this around very brightest stars in the image. It looks like diffraction rings from the star but I'm not sure.
Any ideas?
What's this?
The is a crop from a 170 min. integration of 60 sec subs. 585mono, Ha 6nm, simple histogram stretch.
I only see this around very brightest stars in the image. It looks like diffraction rings from the star but I'm not sure.
Any ideas?
They certainly look like Diffraction rings.
Onion rings, maybe… Or you got holes in your coatings.
andrea tasselli:
Onion rings, maybe... Or you got holes in your coatings.
Now you're just making me hungry...
I am inclined to believe that is Fraunhofer Diffraction, an effect of the optical design of a Newtonian or Ri-Ct telescope, visible even with poorer seeing. Alternatively, there is the possibility that it is fully fledged seeing-related diffraction ringing from an undisturbed wavefront (really good seeing).
V:
I am inclined to believe that is Fraunhofer Diffraction, an effect of the optical design of a Newtonian or Ri-Ct telescope, visible even with poorer seeing. Alternatively, there is the possibility that it is fully fledged seeing-related diffraction ringing from an undisturbed wavefront (really good seeing).
The seeing was excellent so maybe. I've just never seen this before when shooting OSC.
Plenty of discussions about this on CN; what worked for me was to make the camera face the "other" side of the filter.
V:
I am inclined to believe that is Fraunhofer Diffraction, an effect of the optical design of a Newtonian or Ri-Ct telescope, visible even with poorer seeing. Alternatively, there is the possibility that it is fully fledged seeing-related diffraction ringing from an undisturbed wavefront (really good seeing).
I'm not quite sure what you mean by Fraunhofer Diffraction in the context above. At most it could be Fresnel rings in the near field. Same stuff you get when you get to the opticians to get your eye tested.
As for the onion rings, they are a different optical phenomenon, not edible alas...
I've seen the same thing with my 585. No idea if it's filter-related or not, but I can assure you in my case, it is not due to excellent seeing. lol
Plenty of discussions about this on CN; what worked for me was to make the camera face the "other" side of the filter.
I'm not sure I can do that with my filter wheel as the camera bolts on to the housing. Anyway, all the filters are facing the proper way, reflective side towards the sky. and that's never been an issue before.
andrea tasselli:V:
I am inclined to believe that is Fraunhofer Diffraction, an effect of the optical design of a Newtonian or Ri-Ct telescope, visible even with poorer seeing. Alternatively, there is the possibility that it is fully fledged seeing-related diffraction ringing from an undisturbed wavefront (really good seeing).
I'm not quite sure what you mean by Fraunhofer Diffraction in the context above. At most it could be Fresnel rings in the near field. Same stuff you get when you get to the opticians to get your eye tested.
As for the onion rings, they are a different optical phenomenon, not edible alas...
I believe my vocabulary may be mixed up, Fresnel is what I was referring to, Fraunhofer refers to the diffraction patterns provided by an optical design, like how most reflectors create a donut shape when out of focus.
Ok, update on this. I can see the rings most strongly in the Ha
I can also see them in the Oiii frame but the spacing is closer
There is a very, very slight suggestion of them in the red frame and none in the green and blue
This pretty much convinces me that what I'm seeing is an extension of the normal diffraction pattern that all scopes create. The nearly monochromatic light from the filtering just makes it more visible, just like when fringe testing flats and lenses. It doesn't show in the RGB filters because of the wider filter bandwidth. The wider range of frequencies just smear together. I haven't measured the spacing but if it is indeed diffraction, I would expect that the spacing with the lower frequency filter would be wider and this is exactly what I observe.
My conclusion is that it's nothing to do with filter orientation or anything else in the system. In other words, nothing I can fix. it's just the physics of diffraction doing it's thing.
I can also see them in the Oiii frame but the spacing is closer
There is a very, very slight suggestion of them in the red frame and none in the green and blue
This pretty much convinces me that what I'm seeing is an extension of the normal diffraction pattern that all scopes create. The nearly monochromatic light from the filtering just makes it more visible, just like when fringe testing flats and lenses. It doesn't show in the RGB filters because of the wider filter bandwidth. The wider range of frequencies just smear together. I haven't measured the spacing but if it is indeed diffraction, I would expect that the spacing with the lower frequency filter would be wider and this is exactly what I observe.
My conclusion is that it's nothing to do with filter orientation or anything else in the system. In other words, nothing I can fix. it's just the physics of diffraction doing it's thing.
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I wanted to update this thread with some good news. Touptek has decided that the diffraction pattern I was seeing is caused by defective narrowband filters. They are sending my a new set of Ha, Oiii and Sii filters. Hopefully that will correct the issue.
I also want to say that since my purchase of the ATR585 bundle, Touptek customer service has has been second to none. The response is always very helpful and they usually respond in 24 hrs. Can't say enough about quality and speed of their support.
I'll provide an update once I have the new filters in hand.
I also want to say that since my purchase of the ATR585 bundle, Touptek customer service has has been second to none. The response is always very helpful and they usually respond in 24 hrs. Can't say enough about quality and speed of their support.
I'll provide an update once I have the new filters in hand.
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So the interference filters had "holes", as I first argued.
None that I can see without optical aid but it's possible. They didn't say what the cause is. Once I get the new filters I'll take a very close look at the defective ones. What do you think the best way to examine them?
Scanning Electron Microscope
lol, well that's not going to happen!
Trying to think about how this would work. A tiny pinhole on the reflective (sky side) of the filter would admit broadband light that's usually rejected. That gets into the interference space between the coatings and interacts with the nearly monochromatic light inside the filter. Is that the right way to think about it?
Trying to think about how this would work. A tiny pinhole on the reflective (sky side) of the filter would admit broadband light that's usually rejected. That gets into the interference space between the coatings and interacts with the nearly monochromatic light inside the filter. Is that the right way to think about it?
Got the same artifact on a RC8 GSO. Even before BXT.
Tony Gondola:
lol, well that's not going to happen!
Trying to think about how this would work. A tiny pinhole on the reflective (sky side) of the filter would admit broadband light that's usually rejected. That gets into the interference space between the coatings and interacts with the nearly monochromatic light inside the filter. Is that the right way to think about it?
*Not necessarily on one side but if I had to put my money it'll be more on the camera side. On one of the many layers of metallic dielectric.