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To
photograph Comet Lemmon under bright moonlight, which was the plan for this
imaging session, I intend to use short exposures combined with image
stacking and processing software. The bright moonlight (a waxing gibbous
moon around 80% illuminated tonight) will wash out fainter details, so I’ll need
to compensate with equipment and post-processing. Whilst the weather will
be dry for a change, it will be predominantly cloudy with strong breezes and
some big old gusts. All the apps are predicting a chance of a clear spell window
between 7 – 8pm.
So, in today’s
blog post, I
· Share the story setting of the night
· Outline how I set up for the shoot
· List the equipment I used
· Share the camera settings that worked
on the night
In a follow
up post, I will share what steps I took to stack and post edit the images
collected
As
always, if you have any questions, thoughts, tips or photos to share, just drop
me a comment in the box at the end of the post.
Let’s dive
right in then.
Chasing
Comet Lemmon – A Night on the Moors
The wind has
teeth tonight.
I’m high on the moors, parked in a puddled, muddy car park, off the Princetown
Road — Lowery Cross, a lonely outpost overlooking the dark sweep of the Tamar
Valley far below. Out on the horizon, Bodmin Moor rises like a sleeping giant
under a blanket of low cloud, Cornwall’s heart beating faintly in the distance.
The sun has
long slipped below the edge of the world, and the sky is in that magical
in-between — half night, half memory of day. I arrived 90 minutes or so ago to
survey the scene and select my final shooting position. I need a really clear
view of the western sky just above the horizon and inconveniently high gorse
bushes made it tricky to get that perfect view. Now, the stars above are beginning
to blink awake, timid at first, then boldly twinkling between ragged ribbons of
cloud that scuttle across the heavens.
Behind me,
the pine forest whispers and groans, the wind threading through it like a
restless spirit. When the gusts rise, it sounds like distant surf rolling on a
Cornish beach — a phantom ocean that exists only in the imagination.
And then the
moon climbs.
An 80% waxing gibbous — bright, brooding, and otherworldly. Its light spills
across the landscape, silvering the grass and turning the granite boulders into
glittering relics, each one flecked with mica that winks like frost under
torchlight. The clouds become ghost-ships, drifting through a lunar sea, haloed
by a faint, perfect circle of spectral rainbow
Off in the
Tamar Valley, fireworks ignite the night — a carnival of colour blooming
briefly in the darkness. Their echoes roll across the hills like the distant
rumble of battle; scarlet, emerald, and gold flares light up the undersides of
the clouds. Even the TV masts at Princetown and Kit Hill join the show, their
red beacons pulsing like cosmic heartbeats. Below, the headlights of cars carve
through the bends of the Princetown road — glowing orbs on a rollercoaster,
swooping and diving through the moorland gloom.
Up close, my
world is smaller — intimate, ritualistic. The soft, rhythmic clicking of the
camera shutter keeps time with the night. The Primus stove hisses nearby, its
blue flame bright and defiant against the chill, heating water that bubbles and
steams into the cold air. A mug of tea warms my hands, and Fox’s chocolate
cookies — a personal tradition — taste better than any banquet could up here.
Tonight’s
quarry is fleeting: Comet Lemmon, shy and sinking lower toward the
horizon with each passing night. My weather apps promised me one last hour of
clear sky around seven — a narrow window, a final chance. I’m fervently praying I have my calculations
right – the moon should be around 50 degrees plus from the comet position.
And so here
I am. Binoculars in hand, dipping in and out of the shelter provided by the
raised boot hatch, to scan for Arcturus, my ‘lead in’ star for the night.
Equipment has been set up on a grassy bank, tripod kept low to stop it
vibrating in the wind. Polar alignment finally done; Polaris proved evasive in
the small cloud gaps! The ASI air Mini is up and running, shooting details
programmed in. The lens is focused – x10 live view and a bahtinov mask.
And suddenly clear skies to the west – the promised gap! I can’t see the comet due to moonlight, by Sy Safari confirms its rough location. My rig is rotated and tilted to focus on a spot in the sky. A test image of 30”. And magically just like, a faint white streak appears on the green home screen of the ASIair app. Comet Lemmon. Gotcher!
Equipment
used tonight
Portability,
simplicity and quick set-up time is the order of the night given the conditions
and constraints. So, I opted for:
- Astro-modded canon 800D DSLR
- Wide-aperture lens – my Samyang 135mm f/2.0 to let
in maximum light.
- Benbo Carbon Fibre Sturdy tripod
- Skywatcher Star Adventurer 2i
star tracker (essential) - to track the movement of the sky and prevent
star/comet trails in individual shots.
- William Optics equatorial wedge
- ASIair Mini – for plate solving the sky ahead
of me
- Intervalometer - to avoid camera shake (although
I ended up using the ASIair Mini platform in the end)
- Celestron Lithium Battery Power
Tank
- Two power banks – to power the dew bands, should
they be needed
- Star chart app – I use Sky Safari Pro to
accurately locate the comet.
Camera
Settings
Shooting
in Manual Mode and RAW file format for
maximum control in post-processing, my other settings for this session were:
- Aperture: Set to its widest possible
setting (f/2.8), as I find it protects me from slight coma issues at f/2.
- (ISO: Did some test shots to
look at histogram and settled on ISO 800 due to the moonlight.)
- Shutter Speed: Always a balance to be had
between capturing detail without blurring comet nucleus. I opted for 15”
images; hoping that the star tracker will help keep the background stars
as pinpoints.
- Focus: Manually focused on a bright star (Vega) using camera's Live View mode and zoom function to get a sharp focus, then carefully panned back to the comet's location.
- Calibration Frames – depending on conditions, I’ll
aim to take thirty or so "dark frames" immediately after my main
images, using the exact same settings but with the lens cap on. Followed up
by thirty Bias and thirty flat frames.
The
end of the night’s story
For the
first hour, Comet Lemmon hides — stubbornly veiled behind an unyielding wall of
low cloud. I wait, sipping tea, feeling the night settle deeper around me.
Then, almost miraculously, the curtain lifts. The comet appears — faint,
ethereal, a traveller from the deep — and for twenty precious minutes the sky
opens like a gift. It’s a race now, a dance against time and weather. The wind
tugs at my jacket, the shutter ticks its steady rhythm, and above it all, Comet
Lemmon burns softly in the heavens — a tiny messenger from the edges of the
solar system, whispering across the void. I’m genuinely elated!
Settings on the night - Within the gap in the clouds, I managed to obtain 60 x 15” at ISO 800 f/2.8 along with thirty frames each for darks, biases and flat calibration frames. Whilst the camera was busy, I took the opportunity to record the precise dec and RA position co-ordinates – these will be needed for photometric colour calibration in SIRIL over the next couple of days. Throughout the shoot, I checked framing on each image collected.
Should I
have used a light pollution filter of some form to combat the moonlight?
I debated
all afternoon whether to use my Optolong L Pro clip in filter tonight. Marketed
for use with comets in light polluted areas, I was very much in two minds. On
the one hand, it’s great at supressing artificial light such as sodium/mercury
vapour, sky glow etc. it might well improve the contrast between the comet and stars
and the bright sky background.
On the other
hand, the filter could reduce signal strength and introduce artifacts like
halos or colour cast. In addition, the moon is a strong broadband light source which
the filter isn’t really designed to suppress. So, the background may well just
remain bright! There is a chance I might also wash out the comet tail details.
Given I was
in a dark sky area with very little artificial urban light pollution and was
aiming to use shorter exposures for later stacking, and throw in the use of a
fast prime lens and the fact that the moon was far to one side of my image
framing, I decided NOT to use the filter.
What
would you have done in these circumstances?
Have you had success shooting a comet image? What did you do differently
to me and why? Share
your thoughts and tips in the comment box below so that we can continue to learn
together.
As always, I
hope you have found this imaging post useful. Good luck in yours, stay safe,
have fun and clear skies to you all.
Steve
So here we are - three rough and ready initial edits of the images - quickly stacked in SIRIL and quick edits in Affinity Photo. I will spend some time on this later in the week and will do another post about my work flow.
Want to learn more on how to shoot a comet? https://undersouthwestskies.blogspot.com/2025/10/a-beginners-guide-to-photographing.html
