Strange moving object in Dolphin Head Nebula data - Forums

Topic starter

Dec 30, 2025

Hi All,

I was just going through some recent data I have acquired on the Dolphin Head Nebula (Sh2-308), and while blinking through the data I noticed this weird spot that kept bouncing erratically around in my subs.

It shows up in slightly different spots in each of my 5 min sub exposures in both my Ha and Oiii data. I captured the data on the 29 and 30th of Dec, I also went back through some data from last year and could not see it present in the older subs.

My setup is

William Optics FLT120

AM5N mount

asi2600mm Pro

Antlia 3NM filters

I was hoping if anyone could shed some light on what this may be?

📷 Blink00012_2.gif

Engaging

bigCatAstro

Dec 30, 2025

Ryan Benbow · Dec 30, 2025 at 09:35 PM
Hi All,
I was just going through some recent data I have acquired on the Dolphin Head Nebula (Sh2-308), and while blinking through the data I noticed this weird spot that kept bouncing erratically around in my subs.
It shows up in slightly different spots in each of my 5 min sub exposures in both my Ha and Oiii data. I captured the data on the 29 and 30th of Dec, I also went back through some data from last year and could not see it present in the older subs.
My setup is
William Optics FLT120
AM5N mount
asi2600mm Pro
Antlia 3NM filters
I was hoping if anyone could shed some light on what this may be?
📷 Blink00012_2.gif

The first thing to analyze and rule out is some sort of internal reflection—off of the corrector or filters. That’s where I’d start off first.

There’s a bright star on the middle left of your frame that is drifting in and out of your subs. The object seems to be moving in a similar pattern with the drift of that star in the frame.

Ryan Benbow

Topic starter

Dec 30, 2025

Thanks BigCatAstro,

Yeah , I think your right. Slowing it down and looking at it more closely frame by frame, it consistently matches the relative movement of the bright star Udra (cropped out of frame of the gif)

Thanks for your help.

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