Diffraction spikes with refractor

[PKay]

I have never seen this before.
The bright star has distinct spikes.

Any ideas?

Image details:
NGC1531
23 X 300s = 2 hrs

Equipment below.

[Startrek]

I don’t think they are diffraction spikes could be a Galaxy on its horizontal plane or maybe a UFO ??

[Atmos]

If this is moving towards the edge of the frame then it’s likely to be caused by an intrusion in the lens cell. Completely normal, sometimes the spacer (wedges) separating the lens’ intrude a fraction into the optical path.

[PKay]

Hi Martin
Ruled out a galaxy after plate solving.

Hi Colin
The image is a crop, the galaxy and star are near centre.
Also I have done about 20 images with this scope and never seen this effect.

[sunslayr]

Maybe it was a ballooning spider that landed across the lens :lol:

[PKay]

OK, so far we have UFO's, galaxies, OTA intrusions, spiders...

I researched an image taken of NGC1532 with a
Takahashi 150b refractor.
It indeed had spikes albeit more than 2.

So there you go, refractors can add diffraction spikes.

Learn something new every day!

[DavidTrap]

Ditto for what Colin said.

There are three 0.1mm thick aluminium spacers about 10x4mm that sit between the crown and flint of a Tak doublet. Have seen similar effects on bright stars with that scope.

DT

[Merlin66]

I found not diffraction spikes, but three "flares" on an old ED80 I got.
After investigation I tracked it down to the collimation screws (which acted on the edge of one of the elements) Easing these screw solved the problem.
Been 100% for the last few years.

[LostInSp_ce]

I thought that maybe one of Muskies reindeer had blown up. There's so many of those things going up at the moment that one of them is bound to have a collision with something. :lol:

[PKay]

Possible causes's now stand at:
UFO, Galaxy, OTA intrusion, spider and exploding satellite.

Guys an girls, we have to get serious.


So I looked at the Zernike model of aberrations.

Circular wavefront profiles associated with aberrations may be mathematically modeled
using Zernike polynomials.
Developed by Frits Zernike in the 1930s, Zernike's polynomials are orthogonal over a circle of unit radius.
A complex, aberrated wavefront profile may be curve-fitted with Zernike polynomials to yield a set of fitting coefficients
that individually represent different types of aberrations....

Sorry, no i didn't, just fibbing :-)

[multiweb]

+1 What Colin said. I get these occasionally on my old Q with bright stars in the ~75% range off axis. Nothing to worry about.

[The_bluester]

I used to see some diffraction spikes with my old ASI294, which turned out to be a tiny scratch on the sensor chamber window.

https://www.astrobin.com/full/4vt2c5/C/

[PKay]

Nice image Paul.

Yes I can see 2 spikes on the bright star.

Thanks all for the input.

Artefact is now SOLVED.

It was actually a UFO that collided with a satellite, that had spiders on board...