Help needed with a puzzle -- odd effect around star WR 153ab within the Lion Nebula

andrea tasselli:
Optical artefact quite common in fact in refractors/lens.

Spider, ants, tree branch, a bit of fluff. You’d be amazed at how many things in the wild can cause diffraction effects.

The answer is already definitive. It’s a diffraction spike.

You don’t see the spike on every other star in the image because light in the rest of the image did not pass over the debris. It’s not obstructing the whole path of light. If you dithered, or reframed the image, it would likely move to another star, or even possibly disappear.

Since the spike appeared on all your filters, logic dictates it will be on the corrector or the objective.

A simple test for the diffraction spike idea is to retake some more subs of the target with slightly different framing

Lee Pullen · Aug 16, 2025, 07:29 PM

Hi everyone, first time poster here so I hope I'm using the correct area of the forum!

I've got a bit of a puzzle, and I've been advised to seek out help from you good folks on AstroBin. I've just completed an image of the Lion Nebula (full write-up here) and when I zoomed into the star WR 153ab I noticed what look like jets coming out from it. I did some research but couldn't find any reference to this, and what's stranger, I can't seem to spot these "jets" in other images of the Lion Nebula that include this star.

• I don't think it's a filter issue because I see it in data I collected using my Optolong L-Ultimate filter; Askar E2; and no filter at all.

• I don't think it's a stacking artefact because it's just about visible in single subs.

• I don't think it's a tracking issue because it's not visible around any other stars.

So I'm running out of things that it could be. Obviously I'm hopeful that it's something new, but it's more likely that I've made a mistake somewhere or am missing something obvious. I wonder, if you've imaged this region of space before, would you be able to take a look at your data and see if there's anything present around the star? And if you've got a view of it on the next clear night, would you be able to take some pictures and see if the effect is there? I think that's the next step to work out if it's something old and known; is an aberration with my data; or is something genuinely new. 

FYI for the image I used an Askar 130PHQ telescope, and a ZWO 2600MC Pro camera. I image from a Bortle 8 city centre. The effect around the star is fairly bright; I can just about detect it in 2-minute subframes with no filter. So gathering new data should be achievable with relatively modest equipment.

Thanks in advance for any help that can be offered!

Here's it is seen in 30 mins of RGB data (no filter):


This is 10 hours of Askar E2 data:


And 10 hours of Optolong L-Ultimate.

Hi do you use OAG ?

Lee Pullen · Aug 28, 2025, 09:34 AM

No, I use a separate guidescope.

Where to look (bright WR star makes it obvious):

• Front element/corrector & dew shield lip (most common: hair/fiber, spider web, lint).

• Filter face(s) and tilt plate.

• Field flattener/reducer front.

• Less likely but possible: inside of drawtube/baffles.

Quick tests (5–10 min):

1. Defocus bright star (Vega/Altair). If the “spike” becomes a dark/bright radial line in the donut → obstruction in pupil.

2. Rotate camera + filter drawer 90°. If the feature rotates → on/after the rotator; if it stays fixed to the frame → near the objective/dew shield.

3. Dither or nudge framing. You already did this; disappearance confirms localized debris.

Fix (safe clean order):

• Rocket blower first (front element, reducer, filters).

• If still present: microfiber + distilled water mist on the cloth (never spray glass), light radial wipe.

• Stubborn: PEC*PAD + Eclipse/IPA, very light, single pass edges only.

• Inspect the inside dew-shield lip fibers there cause exactly this.

Why only that star?
Diffraction requires the star’s light cone to intersect the strand. A very bright star (WR 153ab in Sh2-132) makes the effect visible; fainter stars don’t cross the obstruction strongly enough, so no spike. Different framing shifts which rays hit the strand.

Clear Skies!