But the 40-year-old amateur snapper got more than she bargained for when she captured the moment a fireball from the Taurid meteor shower fell from the sky, combined with the heavenly aurora glow.
The shower is notorious for producing fireball flares, and experts said this year would be the best chance to witness them yet.
Comment: Interesting comment about it being the 'best chance yet' - is that perhaps because of the incredible uptick in meteor fireball activity?
Mrs Mitchell's photograph has been viewed thousands of times since it was taken in the very early hours of Saturday morning, and shared across social media in every corner of the globe. Meteorologists across the world have also praised the stunning image, saying she captured a once-in-a-lifetime event.
She said it was a phenomenon she never expected to see, and that she had simply been in the right place at the right time.
"I'm a keen aurora chaser so I'm out with the camera at any opportunity," she explained.
"I often visit Pitfour during the day as it's a wonderful place with the camera. I checked recently with my phone compass what angle north would be over the lake with an aurora shot in mind. Myself and my husband are radio amateurs so we follow the space weather sites online and keep a keen eye on the data. Friday and Saturday were looking good so we headed up to Pitfour around 8.30pm, but nothing exciting was happening so we headed back home. More data came through around midnight so we headed back up around 12.30am to get some good colour from the aurora.
"I started shooting and from nowhere a bright streak of light came down over the lake in front of us and a green fireball lit up the whole sky then burned out. Thank goodness the camera was shooting a 30 second exposure and captured the shot.
"I guess we were in the right place at the right time."
Sightings are so often casually noted by the press as being part of the "_____ meteor shower" (The "Taurid" in this case, though, I'm not sure how such a thing is so deftly and accurately determined).
-All in an effort to reassure that these are regular-like-clockwork, perfectly normal, "nothing to see here, citizen" events best relegated to the cute cat pics section of the internet.
For the calendar months when there are no pre-scheduled meteor showers on record to blame, there are handy fill-ins like, "Space Junk!" and "Once in a lifetime!"
Right now it seems that it's there are a lot of fliers and leaflets falling from the sky, precursors to the billboards.