3 ms·

Interesting- If you look closely at the super bright objects, there are both hexagonally symmetric artifacts and cardinal up/down/left/right artifacts. I’d love

Interesting- If you look closely at the super bright objects, there are both hexagonally symmetric artifacts and cardinal up/down/left/right artifacts. I’d love to hear from someone with knowledge of how these arise and what optical tradeoffs prevent designs from eliminating them.

jwuphysics 4y ago
It's possible through deconvolution with a model of the "point spread function" aka PSF. There are techniques from radio astronomy (where interferometry necessitates some kind of Fourier basis model and deconvolution/imaging procedure) which has been extended to the optical domain. See for example: https://twitter.com/NGC3314/status/1582442367482634242?t=EaagiidNTh1Mgtozvm0q_w&s=19 https://twitter.com/NGC3314/status/1582442367482634242?t=Eaa...
- willis936 4y ago
  Isn't the PSF intensity-dependent? Can deconvolve high bit-depth data with a single filter? If not, aren't you limited by the distribution of intensities of the point sources present?
lgl 4y ago
You can read about their formation on several publications. For instance: https://bigthink.com/starts-with-a-bang/james-webb-spikes/ https://bigthink.com/starts-with-a-bang/james-webb-spikes/
Laremere 4y ago
There are 2 causes of diffraction spikes: 1. The hexagonal mirrors. Trade off is larger mirrors, and the ability to fold the telescope. 2. The struts holding the secondary mirror. Basically can't get rid of this without a very different telescope design. Causes of both are the best design for getting a lot of light into a space telescope's sensors. In practice has less impact on the science than you might think. The diffraction spikes are much fainter than the main image. It's only bright foreground stars - which the James Webb isn't trying to image anyways - that cause visible spikes.

3 ms·

Interesting- If you look closely at the super bright objects, there are both hexagonally symmetric artifacts and cardinal up/down/left/right artifacts. I’d love

by etrautmann 4y ago

jwuphysics 4y ago
It's possible through deconvolution with a model of the "point spread function" aka PSF. There are techniques from radio astronomy (where interferometry necessitates some kind of Fourier basis model and deconvolution/imaging procedure) which has been extended to the optical domain. See for example: https://twitter.com/NGC3314/status/1582442367482634242?t=EaagiidNTh1Mgtozvm0q_w&s=19 https://twitter.com/NGC3314/status/1582442367482634242?t=Eaa...
- willis936 4y ago
  Isn't the PSF intensity-dependent? Can deconvolve high bit-depth data with a single filter? If not, aren't you limited by the distribution of intensities of the point sources present?
lgl 4y ago
You can read about their formation on several publications. For instance: https://bigthink.com/starts-with-a-bang/james-webb-spikes/ https://bigthink.com/starts-with-a-bang/james-webb-spikes/
Laremere 4y ago
There are 2 causes of diffraction spikes: 1. The hexagonal mirrors. Trade off is larger mirrors, and the ability to fold the telescope. 2. The struts holding the secondary mirror. Basically can't get rid of this without a very different telescope design. Causes of both are the best design for getting a lot of light into a space telescope's sensors. In practice has less impact on the science than you might think. The diffraction spikes are much fainter than the main image. It's only bright foreground stars - which the James Webb isn't trying to image anyways - that cause visible spikes.