Advice on pronounced diff spikes

[BrendanC]

Looking for advice! This is just over an hour's worth of LDN 1251, the Anglerfish Dark Nebula, and I was surprised to see such pronounced diff spikes. They reach right across the FOV (they're not sat trails, I checked). I recently had the Backyard Universe spider fitted. I know this needs many more hours' worth of exposure, so if press on, will this mean I need to stretch the background less, and the spikes should recede? Or, should I be thinking about flocking the spider vane? Any other recommendations if I continue to gather data on this object? This is with a 130PDS and ASI533MC Pro. Thanks.
 

[vlaiv]

I'd say - leave them as they are.

They contribute a certain charm to the image - they emphasize how strong that star is and add very interesting "compositional twist" to the FOV.

Flocking spider won't help. Diffraction happens because of light / no light situation (blockage) not because of any sort of reflection. Using completely dark spider that reflects no light will produce the same effect.

Only thing that you can do to change appearance of spike is to change the thickness of spider vane. Spider acts as sort of diffraction grating (it is single groove diffraction grating) and spike that you see is different orders of diffraction - each being longer then the other.

If you zoom on the spike itself - you will see that it is "series of rainbows" - each next longer than the one before it:

This is why you seem to perceive spike being far away from the star - it is there all the way - but you've hit rainbow part where camera is less sensitive and rainbow color fits with background in that part. In any case - changing spider thickness changes how dense are these rainbows (how much dispersion there is in diffraction grating).

Thin spider wane produces longer rainbows and thick produces shorter but more concentrated rainbows. That is about it what you can do without staring to curve vanes to affect how dispersion works.

[ONIKKINEN]

These could be easy to remove with simply lassoing them out with content aware fill in Photoshop.

I say could, because it depends on whether starXterminator (or Starnet) dumps the spike to the starless layer or the star layer. If in the starless layer, should be easy because it will be so easy to lasso out. If in the star layer then its a lot more work to dodge the stars.

[BrendanC]

Thanks both!

@vlaiv I take your point about them adding interest to the composition, but I was just very surprised at how pronounced they were. I can't see any other similar effects on Astrobin versions of this object. Still, if you like them, then that's cool. Cuiv the Lazy Geek has also fitted this vane, which came with flocking (of a kind) already applied by Backyard Universe because he's a VIP (!), which is why I thought this might help, see https://youtu.be/I5C0bjwfL_w?si=fur-KTFWGqw-GE6L&t=808

@ONIKKINEN I separated out the stars with StarXTerminator, and this is in the starless layer. I take your point that I could probably edit them out, but I'd rather not. Actually I'd rather they were in the star version because then I could just stretch the stars less and could potentially mitigate this.

Edited September 11, 2023 by BrendanC

[Mandy D]

@BrendanC Curved spider vanes might remove or lessen the diffraction effect.

[BrendanC]

I got a great response from Michael, the maker of the spider vanes, and in fact just realised he's accounted for this on his website too. From https://www.backyard-universe.de/en/i/installation-secondary-spider

[wimvb]

Diffraction spikes is one of the reasons I bought the MN190. I'm so relieved to no longer being bothered by them. Instead of flocking, you could try black matte paint.

[andrew s]

I love them. They are made by real telescopes not toys. 😊 Regards Andrew 

[ollypenrice]

AstroArt has a feature called 'remove line' in the Cosmetic toolbox. You put a point at the end of each line and it disappears with a click. I wouldn't use it to remove all diff spikes but those which seem disembodied (from out of shot stars) or over-extended could probably be removed. Other software may have something similar.

4 hours ago, andrew s said:

I love them. They are made by real telescopes not toys. 😊 Regards Andrew 

Right, that's it! Feather dusters at 400 yards!!

lly

[saac]

4 hours ago, andrew s said:

I love them. They are made by real telescopes not toys. 😊 Regards Andrew 

I'm with Andrew on this, they are also part of the physics of light, there is a story and reason for them being there.  I know it is personal preference but I must admit I do like diffraction spikes being present. 

Jim 

Edited September 12, 2023 by saac

[andrew s]

12 minutes ago, ollypenrice said:

Right, that's it! Feather dusters at 400 yards!!

Is dueling still legal in France? @saac will you be my second? Regards Andrew 

[saac]

6 hours ago, andrew s said:

Is dueling still legal in France? @saac will you be my second? Regards Andrew 

Count me in, but can't be on a school day

Jim 

[michael8554]

See me in my office after Prayers........

Michael

[doublevodka]

There are other methods to minimize them if they really bother you, curved vanes is one although after buying a new spider that might not be preferable...

The other one I've seen kicking around is this which is quite interesting - 

Originally from here by the look of things - http://serge.bertorello.free.fr/antiaigr/antiaigr.html?fbclid=IwAR3l0WvslKTU49PKQiNtBLhXC0AVQHef0bGOcA-1tgVNJGkGfBZ9ga8sBIY will need to translate from French in the browser

[Ouroboros]

I’ve got the remnants of diffraction spikes on the StarXterminator starless version of an image I’m just working on of the crescent nebula.   Below  is a highly zoomed in crop to illustrate.  Should I try and eliminate them or carry on processing regardless?  The diffraction spikes in the stars only image will presumably overlay the remnant diffraction spikes when I add the stars back in at the end anyway.

[ollypenrice]

Regarding matt black paint, it must be pigment-based rather than dye based, the dye-based paints being reflective in some wavelengths. Buying stove or BBQ-type heat proof paints will exclude dye-based ones.

Olly

[GalaxyGael]

On 11/09/2023 at 19:39, BrendanC said:

I got a great response from Michael, the maker of the spider vanes, and in fact just realised he's accounted for this on his website too. From https://www.backyard-universe.de/en/i/installation-secondary-spider

This approach solves this particular problem. That CNC milled spider vanes is mechanically sound, but has significant reflectivity. You should see what happens when the moon is up, even with a dew shield. Big elliptical blueish orb in the frame shown below (this is a sharpstar hypergraph 6 aka sharpstart 15028hnt).  As Olly mentioned, stove paint or non-dye based ones are best. Takahashi epsilons use their concoction that is somewhat similar, but it can be brittle if banged or hit with an allen key by accident, fyi. Easy to remedy.

Here is the moons reflection from the spider.