What is a Harvest Moon, and and are they really worth the hype?
Harvest Moon is the name given to the full Moon closest in date to the first day of autumn, known as the autumn equinox.
The autumn equinox is when day and night are the same length.
The last Harvest Moon occurred on 10 September 2022 and the next will occur next week on 29 September 2023.
The September 29 Harvest Moon will also be the last supermoon of 2023.
Find out how to see and photograph the Harvest Moon, heralding the return of autumn.
Origins of the name Harvest Moon
A Harvest Moon’s proximity to the September equinox means that the rise times for the near-to-full phases of the Moon are nearly the same on the days before and after.
So, the Harvest Moon is so-called because the difference in rise times from one evening to the next after this date is the smallest for the year.
This means the bright, fuller phases of the Moon appear at approximately similar times, lighting the way to collect the harvest.
Indeed, it was the abundance of bright early-evening moonlight on those consecutive days that traditionally lit the fields for collecting the harvest.
Measure the Harvest Moon
A good exercise is to note the rise time of the Moon on in the days before and after the Harvest Moon, calculating the differences.
Waiting for the fuller phases of the Moon to rise is a great way to experience the visual effect of the Moon illusion, which makes these phases appear enormous when close to the horizon.
You can also observe the next full Moon after the Harvest Moon and you should see a similar pattern in rise times for its fuller phases.
The period close to the March equinox represents the opposite situation, with the difference between successive moonrises for the fuller phases of the Moon being the largest of the year.
A good experiment during the Harvest Moon is to make a note of the rise times for the Moon from the date of the full Moon onwards (find them at www.timeanddate.com/moon) and calculate the difference.
Try to remember to do this next March too, when the difference is greatest.
Is a Harvest Moon bigger?
Some believe the Harvest Moon is much bigger or brighter than other full Moons in the year. This isn’t true though.
This belief may have come about due to a complex optical illusion that makes the Moon look bigger when it’s lower down near the horizon.
How to observe a Harvest Moon
Around the time of year that the Harvest Moon appears, the Sun goes down almost due west, so the full Moon will be rising near to due east.
As the Moon rises, see if it has a wonderful ochre red colour, especially when it’s low on the horizon.
This is an effect of the Moon’s light being filtered, as it travels through more of the Earth’s atmosphere than when it’s overhead.
Since red light is scattered least by the Earth’s atmosphere, the Moon takes on this lovely red colour.
Find out more about this in our guide on why the Moon sometimes looks orange.
The lower and less built-up your horizon, the better your chance of seeing the Harvest Moon rising in all of its glory – a fantastic sight that heralds the start of autumn.
How to photograph a Harvest Moon
The sight of a big, bright, almost-full Moon is still pretty impressive. When it’s low in the sky, the ’Moon Illusion’ makes our nearest neighbour look much larger than normal and this is where nature plays a cruel trick on photographers.
With the full Moon having just risen and looking enormous, an average camera shot of it will show that it’s actually pretty tiny.
To see any detail on it, you’ll need at least a 200mm or longer focal length lens or telescope.
A Harvest Moon presents the perfect opportunity to catch that detail. The easiest way to do this is to use a long focal length lens or telescope with a DSLR fitted.
Alternatively, if you have a steady hand, afocal photography (the technique where you point a camera or smartphone down the eyepiece) can work surprisingly well.
For more info on lunar astrophotography, read our guides on how to photograph the Moon, how to photograph the Moon with a smartphone or how to use a DSLR camera.
Capturing detail and colour on the Moon
If your lens or telescope’s focal length is long enough, say above 700mm, you can capture plenty of detail on the lunar surface.
But examination of your shots will reveal two issues: the image is virtually monochrome and detail is a little blurry.
You may think the Moon is fairly colourless and grey, but you’d be wrong. There’s actually quite a lot of subtle colour on offer.
One way to reveal it is to super-saturate your shot.
But this needs to be done with care because it can bring out noise and produce artefacts (features that aren’t actually there).
When you’ve finished the saturation process (outlined in the step-by-step guide below), the result will typically be pretty gaudy.
There’s a trick to improve things.
Use the saturated colour image to provide the colour information and a sharper luminance image for the tone and detail.
If you’re using just a DSLR shot, the luminance component can be provided from your original image of the Moon.
Convert to a greyscale image or, if available, use your graphics editor to turn it black and white.
Load the saturated colour image into a layer-based graphics editor and make a safety duplicate of the layer. To remove excessive noise, simply apply a reasonably strong Gaussian blur.
Making the Moon look natural
Your aim is to produce an image showing relatively smooth areas of colour, free from random splodges of unnatural colour. Don’t worry about losing detail – that’s what the luminance image is for.
It may take a few attempts to get the right amount of blurring, but this is why you’re working on a duplicate layer.
If things go wrong, just delete and start again on another duplicate of the original colour saturated version.
To restore the missing detail from the image, load the greyscale luminance image as a new layer above the saturated and blurred colour image.
Set the greyscale image’s blend mode to luminance and you’ll then have a beautifully detailed image of the Moon showing enhanced colour.
If you have access to a monochrome high-frame-rate camera, use this to produce a sharper, highly detailed luminance image via stacking software such as AutoStakkert! or RegiStax.
For more on this, read our guide on how to stack DSLR images of the Moon.
Recommended equipment
- DSLR camera
- Lens or telescope of at least 700mm focal length
Photograph a Harvest Moon, step-by-step
Step 1
The quickest way to produce a detailed colour image of the Moon is to attach a DSLR camera to a telescope.
A 2-inch adaptor works best and, with the appropriate t-adaptor and barrel for your camera model, simply slots into the eyepiece holder of the telescope.
A tracking mount will make the imaging process easier.
Step 2
Fit the camera and use focus assist (LiveView) to focus, setting it to maximum zoom while looking at the Moon’s edge or a shadowed region.
Bring the scope to its sharpest focus and centre the Moon. Choose a low ISO and adjust the exposure so the Moon looks well defined but isn’t overexposed to pure white anywhere on its disc.
Step 3
When you have a good shot, transfer it to a computer and make a copy of it. Load the copy into a layer-based editor. Duplicate the base layer and work on the upper duplicate.
Open your editor’s saturation control and boost the image saturation to about 50%. Repeat the process until clear colour information is shown.
Step 4
Strong edge blues or reds arise from atmospheric dispersion effects and sometimes aren’t obvious in the original image. Select these colours and reduce their saturation to avoid unwanted false colour bands in your final image.
Once you’re happy, apply a mid-strength Gaussian blur to remove any unwanted colour noise.
Step 5
Put the colour image aside and open the original, unmodified image file. Change the mode to greyscale to lose its colour information.
At this point you can apply an unsharp mask sharpening process to the image to crisp up the detail. Be careful not to overdo this, otherwise you’ll bring out unwanted noise.
Step 6
Select the greyscale (luminance) image and copy it to the clipboard. Paste it in as an upper layer into the colour-saturated blurred image and set its blend mode to ‘luminosity’.
The colour will be added to the sharp luminosity data to give you an enhanced colour image of the Moon.
Pictures of a Harvest Moon
Below is a selection of images of Harvest Moons captured by BBC Sky at Night Magazine readers and astrophotographers.
If you manage to capture an amazing image of the Moon, don’t forget to send us your images or share them with us via Facebook, Twitter and Instagram.
