Editing tutorial: Guide to how I post edit my milky way images

Beginner's Guide: How to Edit Your First Milky Way Landscape Photograph

My first ever attempt at imaging the milky way 

So, you’ve just uploaded your Milky Way photos from last night’s shoot. Whether it’s a single landscape shot or multiple sky and foreground images, you’re now staring at the “morning-after” dilemma: How do you edit these photos to capture that awe and beauty you felt while out under the stars?

In today’s post, I’ll walk you through:

• How I plan a Milky Way shoot with post-editing in mind (from start to finish). I have also created a ‘decision making sheet’ and written several other blog posts about starting out on milky way photography – all these can be accessed here at: https://undersouthwestskies.blogspot.com/2025/08/a-beginners-guide-to-post-editing-your.html

• The step-by-step editing workflow I use to enhance my Milky Way landscape images, depending on what type of shots I’ve taken. You can find all these details in the post below.

Before we dive in, let me share my preferred approach to shooting Milky Way landscapes:

• Sky shots: I prefer to take multiple sky photos, either untracked or tracked, for stacking.
• Foreground shots: I follow up with separate long exposure foreground images.
• Stacking and processing: I then stack the sky images, process them, process the foreground image separately, and finally blend them together to create a cohesive composite.
• To edit my photos, I use a combination of programs like Sequator, DeepSkyStacker, SIRIL, GraXpert, and Affinity Photo.

The planning a shoot posts and workflow I’m sharing here come from limited personal experience and a lot of research and note taking. I’ve learned so much from watching YouTube tutorials and participating in free online astrophotography courses by Kristina Rose Photography and Dan Zafra Photography – which I thoroughly recommend by the way. What I have then done is organise and write up my notes, observations and practical experiences for future reference and adaptation/amendment.

 As always, I am open to feedback, so if you see areas where improvements can be made, feel free to leave a comment! Please!

Another early effort - horrible!

This was a stacked sky - and separate foreground shot - blended  together, very badly I might add!

I think it was also the first milky way shot I had done using my new astro-modded canon 800D

1. Plan Your Milky Way Shoot with Post-Editing in Mind

Good planning while you're shooting can make your post-editing process faster and more enjoyable. Here’s how to get started:

Shoot for the Edit: Visualize the Final Image - Start with the end result in mind. What feeling or story do you want to convey through your final image? If you nail the “vision” during your shoot, it will make the editing process much easier. Your planning should directly influence WHAT camera settings you choose and WHAT  type of shots method you go for.

 

Choose the Right Image Type: One Shot or Composite?

When you’re out shooting, you’ll need to decide whether to capture everything in one shot or use a composite approach (sky and foreground images combined later). As beginners, it’s common to make the mistake of exposing for the sky, which leads to a dark foreground, or exposing for the foreground, which then washes out the Milky Way. So, what are the options available to you?

Some common shot types include:

• Single shot (sky + foreground in one)
• One foreground shot + one sky shot (blended in editing)
• One long exposure foreground + stacked sky shots (blended in editing)
• One focused foreground + stacked sky shots (blended)
• One tracked sky shot + one foreground shot (blended)

 

Assess Your Equipment and Scene

Understanding your gear and the conditions you’re shooting in is essential and it will help you decide which of the approaches above to use – so:

• Camera & lens: What’s your sensor size? How well does your camera perform in low light? What’s the aperture of your lens? (Remember: APS-C cameras might be less sensitive to light than full-frame ones.)
• Scene details: Is your location truly dark, or is there light pollution? What’s the source of any light pollution, and how does it affect shadows and highlights?
• Ambient light: Is there enough light to reveal details in the foreground, or will you need to do some light painting?
• Foreground details: Do you want the foreground to be visible in detail or as a silhouette? If it’s the latter, how will you light it?

My first ever long exposure milky way selfie - using a tracker 

 

2. Keep It Simple: Start with a Foreground and Sky Composite

If you're new to editing Milky Way images, I recommend starting with something simple: two images - one of the foreground - and one of the sky. Process them separately and then blend them together in post-production. Software like Affinity Photo or Photoshop can make this process easier.

I hope you find the above (and the other associated posts I listed) useful if you are taking your first steps in milky way photography. The rest of this post now focuses on:

 

3. How to post process your milky way images

 

Here I share my personal approach and work flow which I hope you find helpful.  

Let’s start by reiterating something I mentioned above - a simple, clear, scene setting OVERVIEW of my approach:

I aim to get the most out of my Milky Way landscape photos by:

1. Stacking the Sky: Using software like DeepSkyStacker, Sequator or SIRIL, I combine multiple sky shots to reduce noise and improve the overall clarity of the Milky Way.
2. Foreground Processing: I process my foreground and sky images separately - paying attention to exposure, contrast, and colour balance to ensure they will blend seamlessly together at the end. I do this initially in Affinity Photo ‘Develop Persona’.
3. Blending the Images: After processing the sky and foreground, it’s time to combine them into one final image. This is where the magic happens - using layer masks in Affinity Photo, carefully blending the foreground with the Milky Way sky to create a smooth, natural-looking scene.

 

Editing Milky Way photos is a learning journey.

There’s no one "perfect" way to do it. The key is practice, learning from others, and refining your workflow over time. Don’t be afraid to experiment and find what works best for you! If you’ve got any questions or suggestions based on your own experience, feel free to leave a comment below. Let’s help each other get better at capturing the beauty of the night sky!

A tracked, stacked image from a couple of years ago 

- this isn't a separate sky and separate foreground image. 

I used a tracker and took 10 longer exposures of the scene and then stacked them in Sequator. I then used selection and masks to do separate edits on the sky and then the background. 

What theory underpins my post editing workflow?  

Before diving into sliders, masks, and layers, it’s important to understand the editing theory behind how Milky Way images are processed. Having this foundation will make everything you do later feel far less random and far more intentional.

Learning From the Best: Why Theory Matters

First, a big shout-out to Kristina Rose Photography. If you ever get the chance to join one of her free annual Milky Way editing courses on Facebook, grab it with both hands. I can’t recommend them highly enough. I gain nothing financially from saying this - but after taking several of her courses, they’ve been the single biggest factor in progressing my very limited understanding of Milky Way photography and post-processing.

Another huge leap in my learning came from reading Photographing the Night Sky: Technique, Planning and Process by the legendary Alyn Wallace. I’m an avid reader, and this is genuinely the most expensive book I’ve ever bought - and it’s worth every single penny. It’s an outstanding resource for anyone serious about night sky photography.

Together, these two influences shaped how I now think about Milky Way photo editing, not as a chaotic set of tools, but as a logical, layered process.

A first effort at light painting

Didn't understand any of that theory did I? 

But, still a good learning opportunity even if the end result leaves much to be desired. 

Big Idea #1: Think in Layers (The Acetate Sheet Analogy)

Kristina encourages her students to imagine a Milky Way image as a stack of transparent acetate sheets, layered one on top of another. This is a powerful mental model - and one that makes editing far easier to understand. She really is a ‘quality’ educator to the core.

Each “acetate sheet” represents a layer in your editing software (such as Affinity Photo or Photoshop). A single image file can contain multiple layer types, including:

• Pixel layers
• Adjustment layers
• Text layers
• Smart object layers
• Group folders

All of these appear in the Layers Panel on the right-hand side of your editing workspace.

A Simple but Powerful Habit

From the very beginning, get into the habit of creating two main layer groups in your layer stack on the right hand side of your editing panel:

• One group for sky layers
• One group for foreground layers

This keeps your Milky Way edits organised, readable, and far easier to adjust later - especially when working with composites.

 

Big Idea #2: Use Selections for Local Editing

Once you understand layers, the next step is learning how to work on specific parts of your image, rather than the whole thing at once.

You can select parts of a single layer and then apply edits only to that selected area. This allows you to isolate:

• Specific areas of the Milky Way
• Parts of the foreground
• Bright stars, dark dust lanes, or horizon glow

Common selection tools include:

• Marquee Tool
• Lasso Tool
• Magic Wand Tool

At this stage, you are working locally, not globally - a key principle in good Milky Way photo editing.

 

Big Idea #3: Turn Selections into Masks (Non-Destructive Editing)

Selections become truly powerful when you turn them into masks.

Masks allow you to continue editing non-destructively, meaning none of your original image data is permanently changed.

Here’s the core rule to remember:

• White reveals
• Black conceals

A white mask allows that part of the layer to show through.
A black mask hides that part of the layer.

How to Create a Mask

1. Make a selection (you’ll see the “marching ants”).
2. Click the Mask icon in the Layers Panel.
3. Your selection is now converted into a mask.

From this point on, you can refine and adjust your edits safely, knowing you can always go back and change them.

 

Big Idea #4: Use Adjustment Layers for Targeted Control

The final foundational concept is learning to work with Adjustment Layers. These allow you to make precise changes to your image without altering the original pixels.

Adjustment layers can be applied globally or clipped to specific masks and grouped together for organisation.

Common Adjustment Layer Types in Milky Way Editing

1. Luminance and Tone Adjustments
These affect brightness and contrast:

• Brightness / Contrast
• Levels
• Curves
• Exposure

Use these to:

• Brighten or darken areas of the sky
• Increase contrast in the Milky Way core
• Control highlight and shadow detail

2. Colour Adjustments
These affect hue and colour balance:

• Vibrance
• Hue / Saturation
• Colour Balance
• Black & White sliders

Colour adjustments are especially useful for:

• Correcting colour casts
• Reducing blue tones in blue-hour foregrounds
• Fine-tuning Milky Way colour without oversaturating stars

 

Why This Theory Matters

Once you understand layers, selections, masks, and adjustment layers, Milky Way editing becomes far more intentional and far less overwhelming. Instead of guessing which slider to move, you’ll know why you’re making each adjustment - and where it should be applied.

In the next section of this guide, I’ll show how these ideas come together in a practical step-by-step Milky Way editing workflow, which you can take away and try on your own images.

Another early milky way effort

This was a separate sky and separate foreground image shoot.

The sky was tracked and stacked - I vaguely remember it being around 15 images of around 60" each.

The foreground - can't remember much other than the bright light was a real pain.

The overall image is therefore a tracked, stacked composite blend.

This was the night I was out in the wilderness of Utah. With warnings from the locals about watching out for mountain lions ringing in my ears - I nearly died of heart failure when a local domestic moggie suddenly appeared between my legs meowing! 

Closest the Missus has got to collecting the life insurance payout! Actually, maybe not - this year's encounter with wild Bears and Wolves in a Croatian forest clearing come pretty high up the 'heart failure' list as well. 

How to Edit a Milky Way Landscape Photo in Affinity Photo: A Step-by-Step Workflow

Ok, its now time for the walk through of my detailed process for editing Milky Way landscape photos using Affinity Photo. Whether you're working with a single sky image, a stacked set of sky images, or separate foreground and sky photos, this workflow will hopefully help you bring out the best in your astrophotography.

I’ll break it down into two main parts: RAW edits (in Affinity Photo’s Develop Persona) and global edits (in the Photo Persona).

Let’s dive in!

Step 1: Basic RAW Edits in the ‘Develop Persona’

Before you dive into the global adjustments, the first step is setting up your image base. This could be a single sky image, a stacked sky image, or even a series of images that will be stacked later. The goal here is to gently adjust some fundamental settings, so the rest of your editing can build on a solid foundation.

1. Load the Image into the Develop Persona

• Open your image in Affinity Photo's Develop Persona one at a time.
• Take a look at the histogram and assess if the exposure needs adjustments. I may want to adjust exposure to see what it is I am working with in the image whilst editing it. If the histogram is too far left, shift the exposure slightly to the right to avoid clipping, especially in the bright parts of the Milky Way. I always do some final readjustment exposure at the end of the workflow to ensure that everything looks correct and that I haven’t blown out stars etc.

 

2. Adjust the White Balance

The aim is to neutralize the sky and avoid any unnatural colour casts (like too much blue or yellow).

• Start by:
• Increasing Vibrance and Saturation sliders to 100% to exaggerate colour differences.
• Adjust the White Balance slider for neutrality (watch for the Milky Way’s core - it should stay neutral).
• Fine-tune the Tint to balance magenta/green tones.
• Return Vibrance and Saturation to 0% once the balance looks right.

 

3. Refine the Dynamic Range

• Use the Shadows and Highlights sliders to recover important details in the image:
• Increase Shadows slightly to reveal foreground details, but don’t overdo it to avoid adding noise. This may well also reveal more of the milky way details too.
• Lower the Highlights to bring out faint stars, and prevent overexposure in bright areas.

o   If there is severe light pollution in image – decrease luminance slightly

 

4. Correct Optics

• Go to the Optics panel and apply Profile Corrections for your specific camera and lens. This will automatically remove lens distortion and vignetting.
• Adjust the Distortion slider to zero if necessary, and enable the Vignetting Correction.

 

5. Increase Contrast (Carefully!)

• Adjust Contrast to separate the Milky Way from the background sky -
• In the Highlights: Increase slightly until you see the contrast but avoid losing star detail or over brightening the foreground OR
• In the Shadows: Lower slightly to darken the sky without losing foreground detail.
• Could also use a Curves Adjustment for a subtle ‘S-curve’ to fine-tune the light/dark areas.

 

6. Final Touches on the Base Image

• Make small tweaks to Vibrance, Saturation, and Highlights.
• Gently increase Clarity and Texture to bring out more fine details, especially in the Milky Way’s dust lanes.
• Apply initial noise reduction if necessary.

 

Important Tip: Avoid Using the ‘Dehaze’ Tool!

I highly recommend NOT using the Dehaze tool during these RAW edits. It tends to introduce unnatural blue hues and colour casts, which is particularly problematic in astrophotography. Stick to the basic adjustments outlined above.

 

Taken just after dusk fell 

Overlooking Wembury Mill cafe towards the Great Mewstone Island

This was a single image of around 15" at ISO 1600 F/2.8 - I think it was my canon 22mm lens

What if You Have Separate Sky and Foreground Images?

If you're working with separate sky and foreground images, you’ll follow the same RAW editing process for both images before blending them together in Affinity Photo.

• Edit both images individually in the Develop Persona using the steps outlined above.
• Then, in the Photo Persona, you’ll use layering and masking techniques to blend the foreground and sky images.

 

For a Single Image with Both Sky and Foreground:

If you have a single image that includes both the foreground and the sky, you’ll need to split the image into two parts for separate edits:

1. Duplicate the Original Image into two separate copies.
2. Work on the Sky in the First Copy:
• Apply all the sky adjustments in the Develop Persona, and save the file.
3. Work on the Foreground in the Second Copy:
• Do the same for the foreground, ignoring the sky portion, and save the file.
4. Combine the Two Images:
• Open both files in separate canvases and copy the foreground layer into the canvas with the sky image.
• Stack the foreground layer above the sky layer.
• Use selections and masks to blend the two images seamlessly.

 

Step 2: Global Edits in the ‘Photo Persona’

Once your image is set up with the RAW edits, you can move to the Photo Persona for further adjustments, working with layers and masking to fine-tune specific areas.

1. Duplicate the Image Layer

• Immediately duplicate the image in the layer stack. Rename one layer to “Foreground” and the other to “Sky”.
• Make sure the Foreground Layer is on top of the Sky Layer in the stack.

2. Edit the Foreground

• Select the Sky using the Selection Tool, then invert the selection to focus on the foreground.
• Click the mask icon in the layer panel (WHITE REVEALS).
• Use Curves and Levels to adjust midtones, increase contrast, and brighten the foreground.
• Apply a subtle S-curve adjustment for extra contrast.
• Use further black point/white point adjustments in Levels if required

 

3. Edit the Sky

• Select the Foreground using the Selection Tool, then invert the selection to focus on the sky.
• Click the mask icon again to make sure only the sky is affected. (WHITE REVEALS)
• Use Curves and Levels adjustments to adjust the sky's brightness and contrast and midtones in the image (shallow ‘S’ curves at dark and light ends of histogram line OR try high pass/ unsharp filters on selected masked areas to achieve further local contrast adjustments)
• Apply Clarity to enhance details in the Milky Way.  
• some level adjustments to clip unwanted blacks and to brighten sky without burning out highlights can also be applied  

 

4. Noise Reduction & Star Control

• At this point, you can either:
• Save the file as a TIFF and use GraXpert for noise reduction. OR
• Use SIRIL and Starnet++ for star separation, creating a starless image for easier Milky Way enhancement – I work to draw out colours and structure of the milky way.
• If you're using SIRIL above, then on the starmask image, reduce star size or adjust their intensity. Then complete the star recomposition process. You should end with an image where the milky way isn’t overpowered by surrounding stars.

 

5. Colour Grading

• Use Gradient Maps or Selective Colour adjustments to subtly add hues like purple or magenta to the Milky Way (a light touch is key here).

6. Final Touches

• Perform a crop if needed.
• Remove any distractions such as trail marks.
• Add final sharpening to the Milky Way core for extra detail.

 

 

A composite image - separate sky and separate foreground blended together

The sky was a stack of 15 images of 15" each at ISO 1600 F/2.8 Samyang 14mm lens

The foreground was same lens and aperture and from memory I think it was ISO 200 and 20" with quick light painting

What If You Have Multiple Sky Images to Stack?

If you’re using multiple sky images (e.g., 10+), stacking them reduces noise significantly. Here’s how to handle it:

1. RAW Edit Each Sky Image:
• Apply the same adjustments to each RAW image in ‘Develop Persona’ (white balance, dynamic range, etc.) but avoid any contrast adjustments.
2. Stack the Images using software like Sequator (don’t forget to use the “freeze ground” option).
3. After stacking, compare the stacked image with an unstacked one - there should be less noise in the final version.
4. Finally, combine the stacked sky image with the foreground image in Affinity Photo, following the previous steps outlined above.

 

What if you have a separate foreground image and a separate sky one which you want to blend together?

·       Open both images one after the other in RAW ‘Develop Persona’ and complete the general edits outlined earlier.

·       Save each edited image and return to photo persona - duplicate one of them and copy that duplicate layer into the other image’s layer stack. Make sure you name one of the layers SKY and the other FOREGROUND

·       Remember - your stack order has foreground on top and sky at bottom

·       Now align your two photos so that they line up correctly

·       Create a selection on the foreground layer by selecting the sky and inverting the selection to get the foreground – turn into a mask using the layer icon and remember WHITE REVEALS

·       Make use further layer adjustments to target different bits of the foreground to correct/enhance those specific areas

·       Repeat the above for the sky but remember to select the foreground and then invert it to get the sky

 

Final Thoughts:

While you can get great results from editing a single image of the Milky Way, for the most stunning and detailed compositions, it’s best to capture separate foreground and sky images. Blending them in post-production allows you to control every aspect of the final image.

By following this detailed workflow, using layers, selections, masks, and adjustment layers, you can start to create breathtaking Milky Way landscape photos that pop with detail and vibrant colour. Good luck – it’s a great learning journey. Happy editing! 

As always, if you have any thoughts, tips or corrections for the above workflow - drop me a comment in the box below. 

Clear skies, stay safe and have fun

Steve 

one of the very first milky way selfies I did

There is so much wrong with this image - that I genuinely don't know where to start.

However, at the time, I was chuffed to bits with it! I was so easily pleased then, wasn't I!

As 2025 draws to a close

 Here are some of the images I've taken this year. 

This will be my last post of 2025.  If you have been following the blog I hope you have found it useful and inspiring; that it has helped you in a small way on your astronomy/astrophotography journey

I wish you and your family a happy Festivity, holiday and New Year. 

Clear skies, stay safe and have fun out under the night sky

Steve 

NGC 1499 The California Nebula

Comet Lemmon

NGC 869

IC 63 The Ghost of Cassiopeia

IC 1318 Sadr region 

IC 1396 and The Elephant Trunk Nebula 

IC 1805 Heart nebula 

M13 globular Cluster

M 92 Globular Cluster 

NGC 7000 The North America Nebula

NGC 6888 The Crescent nebula

M42 and The Flame and Horsehead Nebulae

The \Milky Way above the National Trust Mill cafe 

The Milky Way above Wembury Church 

equipment - building a simple flats panel for a tablet

 A Simple DIY Flats Panel Holder for Astrophotography (That Actually Works!)

Taking flat calibration frames can be one of the more frustrating parts of astrophotography - especially for beginners. Ask ten astrophotographers how they shoot flats and you’ll probably get ten different answers.

Like many newcomers, I started with, and continue to use, the classic stretched white T-shirt method. And while it works… in theory… the reality is often less elegant.

If you’ve ever tried to balance a glowing tablet against a stretched T-shirt while simultaneously firing a remote shutter - all with frozen fingers at the end of a long winter night imaging session - you’ll know exactly what I mean.

I can never keep my flats tablet still after a long night of imaging - especially on cold winter nights! 

So, in today’s post, I’m sharing a cheap, lightweight, homemade flats panel holder that solves those problems and makes capturing flat frames far less painful.

 

Why I Needed a Better Flats Panel Solution:

Until now, my process looked something like this:

• A white T-shirt stretched over an embroidery hoop
• The hoop balanced on the front of my refractor dew shield
• One hand holding a tablet with a white screen
• The other hand operating a remote shutter

It worked… most of the time. But it was fiddly, unstable, and downright annoying after a long imaging session – especially when my cold hands were shaking.

I wanted something secure, repeatable, and easy to use - without spending a fortune.

 

I want a flats tablet that won't need me holding it in place with one hand! 

Something that will fit onto the dew shield and stay snuggly in place!

What I Set Out to Build:

The goal was simple:
A DIY flats panel holder that would securely hold both:

• a diffusion panel (embroidery hoop or white paper)
• a tablet displaying a white screen

…on the dew shield of my Samyang 135mm lens and William Optics Zenithstar 61 II  - which, by happy coincidence, have almost identical dew shield diameters.

Key Design Requirements:

• Lightweight
• Snug fit for tablet and diffusion panel
• Stable on the dew shield
• Easy tablet insertion and removal
• Cheap and quick to build

 

Materials You’ll Need:

Build Materials

• One sheet of A2 foam card (5mm thick – model-making grade)
• Parcel tape
• Double-sided sticky tape
• Suitable strong glue

Tools:

• Sharp craft knife
• Cutting mat or board
• Pencil
• Ruler
• Right-angled set square

 

My Flats Panel & Tablet Dimensions:

• Tablet size: 210mm × 125mm × 8mm
• Finished holder size: 270mm × 155mm × 30mm

This thickness gives the panel enough rigidity while keeping the weight down.

 

The base panel which formed the template for others. The next panel up was identical to this one. 

Step-by-Step Construction:

1. I already had an embroidery hoop slightly larger than the outer diameter of my lens and telescope dew shields. This was fitted with white T-shirt material, which I ironed flat before mounting.
2. I measured and marked out the bottom panel on the foam card.
• There would be six stacked panels in total
• The first panel acted as the template for the others
3. After tracing the outline of the tablet and embroidery hoop, I carefully cut out the hoop opening in the first panel.
4. I repeated this process for the second panel, adding a small finger notch to both panels to make tablet removal easier.
5. Panels three, four, and five were identical - cut to the tablet outline only, with no hoop opening.
6. Panel six had no cut-outs at all, apart from the finger notch.
7. Once all panels were cut, I stacked them and bonded everything together using a combination of glue and double-sided tape.
8. Finally, I wrapped parcel tape around all exposed edges, adding durability and protecting the foam card.

 

Panels 3, 4 and 5 were shaped like this - a big cut-out for the tablet. 

Build Time & First Impressions:

• Build time: ~2 hours
• Weight: Very light
• Fit: Snug and stable

Unfortunately, the weather hasn’t yet allowed me to test it under the stars - but once I do, I’ll add a PS update at the bottom of this post with real-world results.

 

Panels 3 and 4 stuck in place

What Do Flat Calibration Frames Do?

If you’re new to astrophotography and want a deeper understanding of flat frames, what they correct, and why they matter, I’ve covered that in detail in a separate post here:

 

Trial fitting of the tablet 

Total Cost of the Project

• Foam card: £4.00
• Double-sided tape: £2.00
• Embroidery hoop & fabric: donated by my wife (she’s into dressmaking and quilting - very handy!)
• Glue & parcel tape: already in the garage

Grand total: £6.00

Not bad for a custom astrophotography accessory!

 

All the panels securely in place - image shows the slot for the tablet. 

The embroidery hoop is in place in the bottom two panels 

Final Thoughts:

If you decide to give this DIY flats panel holder a try, I’d love to hear how you get on. Drop a comment below with:

• your method
• any improvements
• how well it worked with your setup

As always - clear skies, stay safe out there, and keep enjoying the journey under the stars.

Steve

Vecro straps slide out of the way to allow the tablet to be inserted and then slide back into place to hold it securely

Should we be using a white T shirt method for taking our flat calibratiuon frames? 

Advantages and Disadvantages Explained

The white T-shirt method is one of the most common ways beginners take flat calibration frames in astrophotography. It’s simple, cheap, and widely recommended - but it isn’t without its limitations.

Advantages of the White T-Shirt Method

1. Extremely Low Cost

The biggest advantage is obvious:

• You probably already own a white cotton T-shirt
• No specialist equipment is required

For beginners just getting started with calibration frames, it’s hard to beat the price.

2. Easy Entry Point for Beginners

The method is conceptually simple:

• Stretch a white T-shirt over the telescope aperture
• Point the scope at a bright, evenly lit surface (sky, tablet, laptop, or light panel)
• Take exposures that place the histogram around the middle

This makes it an excellent learning tool for understanding how flat frames work.

3. Good Light Diffusion

Cotton fabric acts as a natural diffuser, helping to:

• Smooth out uneven light sources
• Reduce hotspots from tablets or LED panels

When done well, it can produce surprisingly usable flats.

4. Flexible and Adaptable

The same T-shirt can be used with:

• Refractors
• Camera lenses
• Newtonians (with some creativity)

It’s also easy to add or remove layers to adjust brightness.

5. Portable and Lightweight

Perfect for:

• Field imaging
• Travel setups
• Quick sessions where minimal gear is desirable

Disadvantages of the White T-Shirt Method

1. Inconsistent Tension = Inconsistent Flats

This is the biggest drawback.

If the fabric isn’t stretched evenly:

• You can introduce gradients
• You may create subtle brightness variations
• Dust motes can be blurred inconsistently

Each setup can produce slightly different results — which reduces repeatability.

2. Fabric Texture Can Be a Problem

Not all T-shirts are created equal.

Potential issues include:

• Visible weave patterns
• Uneven thread density
• Logos, seams, or worn areas

These can imprint subtle artefacts onto your flat frames, especially with high-resolution sensors.

3. Susceptible to Wind and Movement

Outdoor astrophotography often means:

• Cold temperatures
• Wind
• Fatigue at the end of the night

A shifting T-shirt can:

• Move during exposure
• Change diffusion characteristics mid-sequence

This is particularly problematic when taking longer flat exposures.

4. Awkward to Use in the Cold

Anyone who images in winter will recognise this problem:

• Cold hands
• Shaking arms
• Balancing a tablet or light source
• Trying not to disturb the imaging train

It works - but it’s rarely comfortable or elegant.

5. Not Ideal for Automation

The white T-shirt method is fundamentally manual:

• Requires hands-on setup
• Difficult to repeat precisely night after night
• Unsuitable for remote or automated observatories

More advanced workflows benefit from flat panels or sky flats taken automatically.

6. Colour Balance Can Vary

Depending on:

• Fabric thickness
• Material type
• Light source used

The spectral transmission may not be perfectly neutral, which can affect colour calibration - particularly with mono cameras and filters.

When Is the White T-Shirt Method a Good Choice?

The white T-shirt method is best suited for:

• Beginners learning astrophotography
• Casual imagers on a tight budget
• Portable or travel rigs
• DSLR and widefield setups
• Occasional imaging sessions

It’s a perfectly valid method - just not the most consistent or convenient one.

When Should You Consider an Alternative?

You may want to move on from the T-shirt method if you:

• Want repeatable, high-quality calibration frames
• Image frequently or remotely
• Use narrowband filters or mono cameras
• Value speed and ease after long sessions
• Are building a more permanent setup

DIY or commercial flat panel solutions offer better consistency and long-term convenience.

Final Thoughts

The white T-shirt method has earned its popularity - it’s accessible, effective, and forgiving. An excellent starting point for taking calibration frames. But as your astrophotography skills grow, its limitations become more apparent.

Many astrophotographers start with a T-shirt… and eventually build or buy something better.

Clear skies, and happy calibrating