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Screen Calibration

When I purchased a new laptop computer back in 2016 for image processing and video editing and was quickly reminded of the importance of having a well-calibrated computer monitor.

The brightness of my new laptop screen was intense. It appears to be about 25% brighter than my well-calibrated 23 Inch external IPS monitor.  

When it comes to editing and viewing astrophotography images, the screen you’re using can really change the appearance of your results. If it’s too dim, you may not see all of the hidden imperfections in your data.

This results in astrophotography images that are less than pleasing to the eye. I’ve had to re-process many of my own photos in the photo gallery after discovered that they did not look the way I intended them to on different screens.

Screen Calibration for Astrophotography

If you have been processing your astrophotography images on a dim monitor, you may be in for an unpleasant surprise when you see them on a bright screen for the first time.

This can be a bit of an unsettling moment, especially if you’ve never been through this exercise before.

When you upload your image to the web, you have to accept the fact that people from all over the world may view your work on monitors and screens that display images MUCH different than yours.

Having a monitor that is too bright will show all of the impurities in your background sky.

One of the most extreme examples of the “bright screen effect” is to view your image on a mobile phone with the brightness tuned all the way up. Most people do not leave their mobile screens at this intense level at all times, but its interesting to see a potential worst-case scenario.

astrophotography tutorial

A common tactic beginners use (myself included), is to decrease the brightness or contrast of the image to “hide” the imperfections present in the background sky.

Noise, color blotches, and a generally poor signal-to-noise ratio turn to black. Unfortunately, this method degrades image quality and you lose an incredible amount of detail in your image. Don’t hide your sky!

It is wise to make sure your computer screen is giving you an accurate rendition of the image you worked so hard to capture. There are many ways to calibrate your computer monitor settings, including online tools and dedicated devices that can match specific color profiles.

The device below (Spyder5 Colorimeter), helps you share and print your images with the look you intended.

colorimeter

The Dataclor Spyder5Pro color accuracy device

A colorimeter will usually have a room light sensor that measures the lighting conditions of your room. If there has been a change in lighting in the room, it alerts you to modify your calibration settings for optimal color accuracy.

This creates a unique color profile for each of your monitors, and it can help you get a better match between your photos on screen and in print.

Why should you calibrate your monitor?

By spending a little time adjusting the calibration settings of your monitor, you can help ensure that the colors and brightness of your astrophotos are represented accurately.

I’ve never used a Colorimeter myself, but I have spent a lot of time adjusting settings manually to find the right balance. When I decide to start printing my photos, I think the Colorimeter is a good idea.

In terms of photography, screen calibration can have a dramatic effect on your online experience whether you are processing astrophotography images or not. You can ensure that you are seeing the images displayed on screen as they were intended to be viewed.  

This is especially important for creative professionals such as Graphic Designers, Photographers and Video Production teams.  

The idea is to have your monitor conforming to a preset color benchmark such as the sRGB or Adobe RGB color space.

screen brightness for astrophotography

 

How do your astrophotography images appear on other screens?

How to Manually Calibrate your Screen for Astrophotography

The first step towards adjusting your computer monitor display settings is by using the interface on the unit itself. Some models have more in-built control options than others. 

If you use an external monitor like me, it will have a set of controls, usually at the front and under the screen.

My ViewSonic LED monitor has the typical bare-bones contrast, brightness, and color mode. You’ll want to make sure that you do not have any ambient lighting in the room affecting your views, so close the blinds and turn off the light.

Do not calibrate your monitor in a bright, sunlit room, or with reflections appearing on-screen.

For accurate results, face your screen head-on, with your eye lined up with the top of the screen.

Calibration Tools and Adjustments

It is necessary to have some reference material on-screen that will let you know if you’ve pushed your settings too far one way or the other.  See the grayscale chart from APCmag below:

screen calibration tool

You should be able to distinguish between each shade of white/black

Using the Color Calibration Feature in Windows 10

If you are using Windows 10, they have a nifty color calibration walk-through that is great for making adjustments called Display Color Calibration.  

It will take you through a number of tests to see just how far off your display is.  They call it “color” calibration, but it’s really an overall screen calibration test.  

You can get to it by following this command path:  Start Menu > Settings > System > Display > Advanced Display Settings > Color Calibration.  The following calibration images are used in the Windows color calibration test.

Have you Checked Your Gamma Today?

“Gamma defines the mathematical relationship between the red, green, and blue color values that are sent to the display and the amount of light that’s ultimately emitted from it.”

Adjusting the gamma on your screen

In the image above, you should not see any overly obvious “dots” within the circles.

The Brightness Effect

As I stated earlier, having a display that is too bright can absolutely wreak havoc on an astrophoto that has been stretched too far. I know about this phenomenon all too well, as I like to stretch my data to its full potential (and sometimes go too far).

The tell-tale signs of an astronomical image that has been stretched too far, or with serious gradient and vignetting issues – is a muddy, green/brown background sky.  

The sky may appear to have a nice neutral dark grey or black on your dim monitor, but on your nephews brand new ultra-backlit iPhone, it’s a multicolored mess. 

Even images on APOD can appear to diminish in quality under the scrutiny of an overly bright display.

Here’s an image you can use as a guide.  You should be able to distinguish between the mans shirt and the background.  The black “X” in the background should be barely visible.

monitor calibration test

 

Contrast – Don’t Overdo it

Using the image below, adjust the contrast settings of your monitor so that the background appears black and not grey. If you have lost details in the white shirt the man is wearing, such as the buttons and creases, you have pushed the contrast too far.

adjusting contrast

My Best Advice

My advice is to process the image on image on a screen that has been calibrated as best as possible.  If you have access to an overly bright, unforgiving display – maybe have a look at your image on that as well.  

It can be useful to see an exaggerated version of your subject and fix any issues that really jump out at you.

It may be helpful to view your processed image on several different screens (including your phone) to get a feel for the middle ground. I usually preview my images on at least 3 monitors before posting online.

Take a look a few example astronomy photos taken by professionals on Astronomy Picture of the Day. Use the color, levels and background sky you see in their photos as a guideline. Chances are, the photos you see here will look great, no matter which display screen you view them on.  

Horsehead Nebula

This is because they have taken the precautions needed to ensure that their images are an accurate representation of scientific data, including screen calibration.  Many of these astrophotographers have dedicated calibration tools to help them keep their displays accurate.

I have had many issues with uneven sky backgrounds in the past, primarily due to the lack of using flat frames.

The dim monitors hide this messy background making the sky to appear a nice dark grey or black. There is value in viewing your images on a variety on screens to learn how to better process your images.  

I hope that this write-up has opened your eyes to the importance of screen calibration when processing astrophotography images.  

As for getting your night sky photos printed? I’ll save that for another post.

Watch my Astrophotography Image Processing Tutorial (Photoshop)

 

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Selective Processing for More Detail

Staying Inside – Image Processing

The unseasonably cold weather and precipitation we have experienced here in Southern Ontario have given me the perfect opportunity to go through my old astrophotography images and reprocess the data.  I have been advancing my image-processing skills by studying current astronomy images taken by the pros.

Being a creative professional myself, I have always understood and appreciated the power of inspiration. I am always interested in new image-processing techniques, photoshop tutorials and new software that can enhance my work.  Through selective processing, I have been able to squeeze out the most amount of detail from my astro images.

Western Veil Nebula

The Western Veil Nebula – I reduced the stars to show more contrast in the nebula

My latest take on The Swan Nebula is my favourite version yet. Through selective processing, I was able to tame the background stars, while intensifying the gorgeous pinks and reds in the nebula itself.  I also recently reprocessed my wide-field image of the Western Veil Nebula, with a focus on reducing star size, and overall image contrast and color. The “witch’s broom nebula” is a tough process, especially if you have to deal with a severe gradient behind all of those stars. After assessing the gradient in photoshop, (mostly due to heavy light-pollution) I can easily even out the sky background using the Gradient Xterminator plugin.

I am quite pleased at my latest results of the Eagle Nebula as well.  I went through my astrophotography folders from the past 4 years (like I said, it’s been cloudy!)  and found a set of almost 2 hours of frames on M16 that I had not previously used!  I combined all of the data together from May 2012, and May 2013 in Deep Sky Stacker to create an image with over 3 hours of exposure time.  I decided to keep the extremely wide-field view captured by my 80mm telescope, rather than cropping the photo around the nebula. This image really benefitted from the selective processing technique. By reducing the stars on a separate layer, I was able to keep all of the detail found in the nebula.

Eagle Nebula - 80mm Telescope

Wide field image of the Eagle Nebula with my 80mm telescope

Image Processing Techniques

One of the processing techniques I have been implementing into my photos is to process different elements of the image separately. By this, I mean to process the background, the stars and the nebulosity on their own.  I am able to do this by selecting each element of the image and stretching the data without affecting the other areas. For example, I can boost the vibrance and saturation of the nebula or galaxy without adding additional noise to the background of space and stars.

As I have stated many times, I prefer to tame the stars in the image to be as small as possible.  Normally, I would run the “make stars smaller” action to the entire image in Photoshop. This actually starts to diminish the precious detail in your deep-sky object that you worked so hard to capture! Many other actions that are intended to correct issues with the background space and stars can take away from your subject as well.

You can also manually Remove the Stars Completely from your image using photoshop.

Swan Nebula - 8 Inch telescope

My latest version of the Swan Nebula

Selective Processing

There are several ways to accomplish the selective processing technique to your astronomy photos.  You can create multiple adjustment layers of your image in Photoshop, and apply the various actions to each element of the image on a separate layer.  Once you have applied your desired settings applied to each layer, you can use layer masks to combine all aspects of the photograph into one.  This means you will likely have layers for:

  • The Background Space – With a balanced black-point set

  • The Background Stars – Small, sharp and with lots of accurate colour

  • The Brighter Stars – Soft, or with Diffraction Spikes and Color

  • The Deep-Sky Object – Full of luminance, color and detail

  • The Core or Brightest Area of the DSO – reduced to show detail, not blown out

 

Selective Processing - Astrophotography

Processing the nebulosity separately from the background stars in Photoshop

You can also process the selected elements of your images as separate documents.  Sometime I prefer to do this to really focus on achieving the best possible result for my focus area, without the temptation to poke around at another feature.  Once you have processed each version of the image with your focus area maximized, you can then combine the images using layer masks.  The blending and layer masking is definitely the most delicate stage of the process.  You can really make a mess of an image by failing to inspect all areas of your image before flattening.

I find it helpful to use a reference image of your deep-sky target. This is the best way to make sure you have not overstretched your image data, and that your colors and details are an accurate portrayal of that particular deep sky wonder. I often look for inspiration on APOD!  To stay connected with me and my latest astrophotography images, please follow my Facebook Page.  I hope you are all excited about the wonderful deep-sky targets that will be gracing our night sky the coming months, I sure am!

Resources:

Astrophotography for Beginners – The Basics

How to choose an Astrophotography Camera – My Advice

Top 5 Telescopes for Beginners – My Advice

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M33 Galaxy – The Triangulum Galaxy

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M33 Galaxy

M33 – The Triangulum Galaxy

The Triangulum Galaxy

The M33 Galaxy is the third-largest galaxy in the local-group of galaxies, behind the Milky Way and Andromeda.  It’s large size from our vantage point makes my wide-field astrophotography 80mm telescope a great choice for imaging this target. Despite it’s size, the Triangulum Galaxy appears much dimmer than M31 – The Andromeda galaxy.  If you are new to astrophotography, chances are that the Triangulum Galaxy is one of the first few galaxy names you have learned.

M33 Galaxy Photo Details:

Telescope: Explore Scientific ED80 with WO Flat III 0.8x FR/FF
Mount: Skywatcher HEQ5 Pro Synscan
Guiding: Meade DSI Pro II and PHD Guiding
Guide Scope: Orion Mini 50mm
Camera: Canon EOS 450D (Modified)
ISO: 800
Total Exposure: 7 Hours (84 x 300 seconds)
Processing Software: Deep Sky Stacker, Photoshop CC
Support Files: 20 darks, 20 flats, 20 bias

Target Acquired – Messier 33

I have managed to image the M33 Galaxy from my backyard for multiple nights over the course of nearly a week. I can’t remember the last time we have had such a long stretch of clear night skies in the Niagara region. Mind you, these clear nights occurred during weekdays, and I have to be up early for work (and to walk the dog) early each morning. Needless to say, I haven’t been getting much sleep lately.  Luckily my astrophotography equipment can be set up and ready for imaging in about 30 minutes. This includes polar alignment, calibration, focus and guiding.  

M33 Galaxy - Astrophotography

My Telescope pointed at the M33 Galaxy

But first, the Elephant’s Trunk

My first imaging session was on the night of September 16th. Smack-dab in the middle of the work week. I didn’t originally intend to shoot the M33 galaxy that night, I started with IC 1396. The Elephant’s Trunk nebula is a concentration of interstellar gas and dust within IC 1396, located in the constellation Cepheus. You can view the results of this project below.

This area of the night sky is in a perfect spot for imaging at this time of year from my location, almost directly overhead. I captured 38 frames on this DSO on Wednesday night. The subs were 4 minutes each using ISO 800 on my aging modified Canon Xsi.

IC 1396 – Elephant’s Trunk Nebula

Elephant's Trunk Nebula

IC 1396 – Elephant’s Trunk Nebula – A tad noisy!

IC 1396 – Astrophotography Image Details

Telescope: Explore Scientific ED80 with WO Flat III 0.8x FR/FF
Mount: Skywatcher HEQ5 Pro Synscan
Guiding: Meade DSI Pro II and PHD Guiding
Guide Scope: Orion Mini 50mm
Camera: Canon EOS 450D (Modified)
ISO: 800
Total Exposure: 2 Hours, 24 Minutes (36 x 240 seconds)
Processing Software: Deep Sky Stacker, Photoshop CC
Support Files: 15 dark frames

The Elephant’s Trunk nebula can be seen in the top center-right of the photo above. It is a dark patch with a bright, sinuous rim. The rim is the surface of a dense cloud that is being illuminated and ionized by a very bright, massive star. Faint objects like this are difficult to image from light-polluted skies in the city. I found myself battling with horrible gradients and noise when processing this image. I will likely add more time to the Elephant’s Trunk Nebula during the weeks that surround the new moon in October. Another 4 hours should help me pull out more detail with less noise.

Canon 450D attached to my telescope

Canon Xsi 450D for astrophotography – attached to my telescope with the William Optics 0.8 FF

On to the M33 Galaxy…

After achieving a steady graph in PHD guiding, and a tight-focus on my reference star (Alderamin) I set BackyardEOS to take 50 frames, and I headed to bed.  I set my alarm for 2:00am, and managed to stumble back out to the patio to check on my results.  The Elephant’s trunk nebula was too far west, and my telescope would soon by aiming directly at my garage!  Because the sky was still crisp and clear, I figured I would add some time a second object for the night.  I imaged the M33 Galaxy back in 2012, but that was before I self-modded my 450D for astrophotography.  The Triangulum Galaxy contains some beautiful pink nebulosity within it that I knew I could now capture.

The following 2 nights of the week were also clear, and I took full advantage. This time, I shelved my plans for the Elephant’s trunk, and focused all of my efforts on Messier 33. I captured an impressive 49 subs the following night at 5 minutes each, and then I added another 17 light frames the night after that!

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M33 Galaxy

M33 – The Triangulum Galaxy

My total number of frames on this object was now over 100! That’s a lot of imaging in one week. All that was left now was to stack and process all of the data acquired. I set Deep sky stacker to use “the best 90% of frames” to register and stack, which resulted in a final stack of 84 images total, or exactly 7 hours. I even had success with my creation of flat and bias frames. I shot the bias frames through the telescope with the lens cap on, at the fastest shutter speed my camera allows (1/4000 of a second). The flat frames were created by shooting through the telescope, pointed at the early morning blue sky. These were shot with the camera in Av mode. I shot separate bias and flat frames for each night, except the first. Only dark frames were used for that imaging session.

Processing a photo with 7 hours worth of data is quite enjoyable.  There is less noise, and more detail than I am used to.  As with all of my astrophotography images, I am sure I will re-process my photo of Messier 33 several times until I feel like I have done the galaxy justice. Everyone has their own taste, and at the end of the day, you have to be happy with it.

BackyardEOS 3.1

I finally purchased a copy of BackyardEOS 3.1 Classic Edition. My trial period has ended, and I am very happy with the software. The focus and framing tab, dithering control, and file organization features are my favourite, and make me wish I had upgraded to this software a lot sooner. I always had a hard time getting accurate focus using the live-view function of my DSLR. The focusing function built-in to BackyardEOS allow you to view a digital readout of the star size in real-time as you focus your telescope. The lower number you see on-screen, the better your focus! The filename for each sub lists the ISO, object name, exposure time, date and even the temperature! This is extremely handy when stacking a large number of frames from multiple nights.

BackyardEOS

Screenshot of the BackyardEOS 3.1 Software

I would love to hear what you think of my results for this galaxy image.  You can also follow me on twitter to see more of the “behind-the-scenes” stuff from the backyard. As always, if you have any questions about the equipment I used, or my processing techniques, please leave a comment below.  Thank you so much for visiting my website.

Backyard Astrophotography

Another night under the stars in the backyard

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