About Diffraction Spikes in Publicly-released Webb Images

[JanPalmer]

The Keck telescopes show six diffraction spikes in their images due to the secondary mirrors being supported by a six-strutted spider.

Hubble has four spikes in its images, as do all amateur reflector telescopes with four-strutted/veined spiders, mine included.

Webb has a three-veined spider, so we should expect to see images with three diffraction spikes in the publicly-released pictures. But, oddly, we don't see these.

NASA says there are six spikes in Webb images due to the hexagonal primary mirror – which is the same shape as the two Keck telescope mirrors. Yet no one mentions the absence of the three spikes caused by Webb's secondary mirror spider support.

However, as I see it, there ought to be THREE diffraction spikes dominant over the weaker six spikes from Webb's primary mirror's spikes.

The three spikes should be at the angles of the struts supporting the secondary mirror. In Webb's case, one diffraction spike should be at zero degrees, and the other two should be some 20 degrees on either side of the 180 degrees mark on the opposite side.

These dominant spikes are strangely absent in all Webb images.

How can this absence be explained?

Any suggestions will be most welcome.

[antosarai]

https://webbtelescope.org/contents/medi ... 1GAMSHKSSN

[JanPalmer]

Yes, that seems to make sense. The strut design is such that it produces eight-pointed stars, which is what we see in the publicly-released pictures.

Thanks.