Post by BrƎИsꓘi on Jan 17, 2022 10:37:16 GMT
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Most of the Deep Sky Objects [DSOs] that you see in astrophotography (as a rule) require a tracking mount focused around Polaris using long exposures - in order to pick up finer details.
However, there are some brighter DSOs that are said can be imaged using shorter exposures on a standard (untracked) tripod mount.
A word about Night Sky Imaging basics:
When imaging the night sky, longer exposures capture the movement of stars resulting from the rotation of earth. Longer exposure times give longer star trails and if you're after creating some star trails - that's the easy way to do it. However, if you're looking to capture specific detail from the night sky we have to look to obeying some rules.
♦ The precise (and costly method) is to purchase an equatorial tracking mount. These will do the heavy lifting for you, allowing you to grab (depending upon your camera lens) 1-4 minute exposures.
♦ Alternatively, if we know where our target is (and it's bright enough) we can take lots of shorter exposures. The length of your exposure time is dictated by something called the "500 Rule". This states that the longest exposure time (in seconds) = 500 / (lens mm x crop factor). This is what we'll be doing here.
For example - using my Canon 200d (crop = 1.6) and Samyang 135mm lens, my maximum exposure time = 500 / (135 x 1.6) = 2.3 secs. So in theory, I can target DSOs with that equipment for 2secs without seeing any star drift/trails.
Based on this, I've created a workflow that explains how I captured the images found here:
Astrophotography Images
Anyhow, for those wishing to have a go (my workflow is below), here is all the gear you need:
♦ DSLR Camera
♦ Lens any ebtween 50 and 200mm should be fine
♦ Tripod
♦ Remote shutter release cable (intervalometer is more convenient)
♦ Deep Sky Stacker Software (it's freeware)
♦ Photoshop CS2 (or later) CS2 is free if you can still find the download link as Adobe disabled the activation server for this version.
Note: other imaging software is available; GIMP, Affinity eTC and if you know your way round your application of choice then my guide should still apply.
Right, no further delays, let's dive in...
WORKFLOW:
CAPTURE:
♦ Set Camera Image Format to RAW
♦ Equipment: Canon 200d, Samyang 135mm lens, Tripod (untracked mount), Hahnel Captur intervalometer (any intervalometer or manual shutter release cable will do)
♦ Camera settings: F/2.0 (aperture), 1600 (iso), 1sec (exp) - if your lens doesn't have an F/2.0 aperture, don't worry - set it to the lowest value you have. Additionally, the iso value may need to increase beyong 1600 (32000 or 6400) to compensate a little.
♦ Camera and Lens set to Manual.
♦ Manually focus the camera on the brightest star closest to your target. Star focussing is tricky - if you camera has an LCD - you're aiming to make the star look as small as possible (use LCD zoom if you have one)
♦ Images Required: 200-600x images, 10x dark frames, 10x flats
(using the above settings, dark are images taken with lens cap on, flats are usually taken with a clean white tshirt or similar over the lens)
♦ make sure your camera is set to capture Raw images - Jpegs are redundant for this exercise.
(In the bitter cold I completely forgot to take "flats")
Although I captured 600 image files, 200-300 should be plenty.
♦ Position Your targeted DSO (in this case Orion) slightly left of centre - this will save you having to adjust the camera position as the target slides off the right of frame.
(if using a manual shutter cable ignore the next four steps and instead hit the cable button for each exposure)
♦ set intervalometer @ delay = 00:00'00", long = 00:00'01", interval = 00:00'02", shots = 300 (or desired value) -
♦ press Start button
♦ if you've opted to capture 600 or so, remember to STOP intervalometer at 300 and reposition camera/tripod
♦ press START again.
when done press STOP and proceed to Stacking.
STACKING:
I use Deep Sky Stacker [DSS] and Sequator – they’re freeware and remove all of the hassle from the process - when compared to trying to stack from within your imaging application.
These take your image files and subtract your darks and flats to "average out" noise while "averaging in" signal, thereby increasing the signal to noise ratio.
Before we begin, copy the all of your captures to your computer – including any Darks or Flats. Note this only needs to be done once - use either Sequator or Deep Sky Stacker - whichever you prefer.
Sequator [workflow]
♦ Click File > Star Images > navigate to folder and select all captured sky images
♦ Click File > Base Image > from same folder select which image you want to be your main image
♦ Click File > Noise Images > from same folder select your Darks
♦ Set Composition to Align Stars
♦ The only other settings to change are: Remove Dynamic Noises = On and Reduce Light Pollution = On
♦ Click File > Output and assign a name to your output file. Test.tif is easy to find later.
♦ click START and Sequator will do its thing, when completed click CLOSE popup
♦ ♦ We're now done with Sequator - close the app.
Deep Sky Stacker [workflow]
♦ click Open picture files - select all Raw images from your folder
♦ in the lower window > highlight top image > scroll to bottom > using left-shift click bottom image and click Open.
♦ Right-click and select Check
♦ You also need to load in your calibration frames, repeat the above selecting Darks and Flats separately (no need to select Check this time)
♦ From menu, select Register Check Pictures
♦ In popup box ensure all three tick-boxes are checked and set Select the best to 95%
♦ Click Advanced > Click the number of detected stars button > ideally you'll need around 100. If more or less are found, move the slider and try again (80-120 is good).
♦ Click Recommended Settings > Where any item is shown in Red Click the blue link immediately below it to automatically/instantly fix these. Once done, click OK - this returns you to previous menu, click OK again
♦ This returns you to the Stacking Steps screen, click OK and away we go!
This could take a couple of hours or more. If there's loads to stack and your pc is a little older - you can leave it overnight, or alternatively go and have several cups of tea while you wait. When done DSS will have created an autosave.tif image (usually around 100-250mb). Make a note of the file location (top status bar).
♦ We're now done with DSS - close the app.
PROCESSING:
PROCESSING:
I have two old versions of PhotoShop - CS2 & CS3 - both work fine for this. I've also got Affinity and although I've not used it for this, the process is very similar - using the same functionality. The same processes can be applied to GIMP too.Y ou will need to be familiar with the equivalent instruction/menu item/icons for your own app.
♦ Open your autosave.tif or Test.tif file in Photoshop – or your own app.
♦ Crop the image so that your 3x3 grid occupies only the point of interest and 8 identically-sized spaces around it. Ideally, you're looking at a width reduction of around 2/3 and height reduction of around 1/3.
♦ Once you have your cropped image create a duplicate layer > Always apply edits to your Working Layer - this makes it easier to back out any changes you're not happy with.
♦ Now - the fun part: bringing out the Nebulosity
♦ Image > Adjustments > Levels
> move the right-hand slider to the far right point of the histogram data display > click Ok
♦ again...Image > Adjustments > Levels
> now move the left-hand and centre sliders closer to the main histogram display - do this a little at a time. click OK
♦ Repeat the above two Levels adjustments as often as you like until you're happy with the result - but only a little adjustment each time.
♦ if the sky colour looks wrong you can adjust this by; Image > Adjustments > Levels > select middle eyedropper > find and click a part of the sky where it should be completely black > click OK
♦ Create a new layer
♦ at this stage you can adjust the hue/saturation/vibrance to suit selecting
♦ Image Adjustments > Brightness & Contrast or Image Adjustments > Hue/Saturation - do not over-egg this
Some final adjustments...
♦ next to bring out more detail click...Image Adjustments > Curves
♦ click (newer versions with Ctrl) eyedropper somewhere that the nebula appears more faint.
♦ click the histogram and pull the band up slightly (from middle-ish) to adjust the nebulosity.
♦ in the same histogram click slightly further down the band and drag it below the line > this will help to rectify the sky tone altered by previous step. when happy click OK
♦ some final fixes: create a duplicate layer and again...Image > Adjustments > Levels
♦ move the centre slider to the right to darken the sky
♦ make any final desired adjustments to hue/saturation and vibrance.
This image was achieved using the above workflow.
Good luck and clear skies, folks.
Most of the Deep Sky Objects [DSOs] that you see in astrophotography (as a rule) require a tracking mount focused around Polaris using long exposures - in order to pick up finer details.
However, there are some brighter DSOs that are said can be imaged using shorter exposures on a standard (untracked) tripod mount.
A word about Night Sky Imaging basics:
When imaging the night sky, longer exposures capture the movement of stars resulting from the rotation of earth. Longer exposure times give longer star trails and if you're after creating some star trails - that's the easy way to do it. However, if you're looking to capture specific detail from the night sky we have to look to obeying some rules.
♦ The precise (and costly method) is to purchase an equatorial tracking mount. These will do the heavy lifting for you, allowing you to grab (depending upon your camera lens) 1-4 minute exposures.
♦ Alternatively, if we know where our target is (and it's bright enough) we can take lots of shorter exposures. The length of your exposure time is dictated by something called the "500 Rule". This states that the longest exposure time (in seconds) = 500 / (lens mm x crop factor). This is what we'll be doing here.
For example - using my Canon 200d (crop = 1.6) and Samyang 135mm lens, my maximum exposure time = 500 / (135 x 1.6) = 2.3 secs. So in theory, I can target DSOs with that equipment for 2secs without seeing any star drift/trails.
Based on this, I've created a workflow that explains how I captured the images found here:
Astrophotography Images
Anyhow, for those wishing to have a go (my workflow is below), here is all the gear you need:
♦ DSLR Camera
♦ Lens any ebtween 50 and 200mm should be fine
♦ Tripod
♦ Remote shutter release cable (intervalometer is more convenient)
♦ Deep Sky Stacker Software (it's freeware)
♦ Photoshop CS2 (or later) CS2 is free if you can still find the download link as Adobe disabled the activation server for this version.
Note: other imaging software is available; GIMP, Affinity eTC and if you know your way round your application of choice then my guide should still apply.
Right, no further delays, let's dive in...
WORKFLOW:
CAPTURE:
♦ Set Camera Image Format to RAW
♦ Equipment: Canon 200d, Samyang 135mm lens, Tripod (untracked mount), Hahnel Captur intervalometer (any intervalometer or manual shutter release cable will do)
♦ Camera settings: F/2.0 (aperture), 1600 (iso), 1sec (exp) - if your lens doesn't have an F/2.0 aperture, don't worry - set it to the lowest value you have. Additionally, the iso value may need to increase beyong 1600 (32000 or 6400) to compensate a little.
♦ Camera and Lens set to Manual.
♦ Manually focus the camera on the brightest star closest to your target. Star focussing is tricky - if you camera has an LCD - you're aiming to make the star look as small as possible (use LCD zoom if you have one)
♦ Images Required: 200-600x images, 10x dark frames, 10x flats
(using the above settings, dark are images taken with lens cap on, flats are usually taken with a clean white tshirt or similar over the lens)
♦ make sure your camera is set to capture Raw images - Jpegs are redundant for this exercise.
(In the bitter cold I completely forgot to take "flats")
Although I captured 600 image files, 200-300 should be plenty.
♦ Position Your targeted DSO (in this case Orion) slightly left of centre - this will save you having to adjust the camera position as the target slides off the right of frame.
(if using a manual shutter cable ignore the next four steps and instead hit the cable button for each exposure)
♦ set intervalometer @ delay = 00:00'00", long = 00:00'01", interval = 00:00'02", shots = 300 (or desired value) -
♦ press Start button
♦ if you've opted to capture 600 or so, remember to STOP intervalometer at 300 and reposition camera/tripod
♦ press START again.
when done press STOP and proceed to Stacking.
STACKING:
I use Deep Sky Stacker [DSS] and Sequator – they’re freeware and remove all of the hassle from the process - when compared to trying to stack from within your imaging application.
These take your image files and subtract your darks and flats to "average out" noise while "averaging in" signal, thereby increasing the signal to noise ratio.
Before we begin, copy the all of your captures to your computer – including any Darks or Flats. Note this only needs to be done once - use either Sequator or Deep Sky Stacker - whichever you prefer.
Sequator [workflow]
♦ Click File > Star Images > navigate to folder and select all captured sky images
♦ Click File > Base Image > from same folder select which image you want to be your main image
♦ Click File > Noise Images > from same folder select your Darks
♦ Set Composition to Align Stars
♦ The only other settings to change are: Remove Dynamic Noises = On and Reduce Light Pollution = On
♦ Click File > Output and assign a name to your output file. Test.tif is easy to find later.
♦ click START and Sequator will do its thing, when completed click CLOSE popup
♦ ♦ We're now done with Sequator - close the app.
Deep Sky Stacker [workflow]
♦ click Open picture files - select all Raw images from your folder
♦ in the lower window > highlight top image > scroll to bottom > using left-shift click bottom image and click Open.
♦ Right-click and select Check
♦ You also need to load in your calibration frames, repeat the above selecting Darks and Flats separately (no need to select Check this time)
♦ From menu, select Register Check Pictures
♦ In popup box ensure all three tick-boxes are checked and set Select the best to 95%
♦ Click Advanced > Click the number of detected stars button > ideally you'll need around 100. If more or less are found, move the slider and try again (80-120 is good).
♦ Click Recommended Settings > Where any item is shown in Red Click the blue link immediately below it to automatically/instantly fix these. Once done, click OK - this returns you to previous menu, click OK again
♦ This returns you to the Stacking Steps screen, click OK and away we go!
This could take a couple of hours or more. If there's loads to stack and your pc is a little older - you can leave it overnight, or alternatively go and have several cups of tea while you wait. When done DSS will have created an autosave.tif image (usually around 100-250mb). Make a note of the file location (top status bar).
♦ We're now done with DSS - close the app.
PROCESSING:
PROCESSING:
I have two old versions of PhotoShop - CS2 & CS3 - both work fine for this. I've also got Affinity and although I've not used it for this, the process is very similar - using the same functionality. The same processes can be applied to GIMP too.Y ou will need to be familiar with the equivalent instruction/menu item/icons for your own app.
♦ Open your autosave.tif or Test.tif file in Photoshop – or your own app.
♦ Crop the image so that your 3x3 grid occupies only the point of interest and 8 identically-sized spaces around it. Ideally, you're looking at a width reduction of around 2/3 and height reduction of around 1/3.
♦ Once you have your cropped image create a duplicate layer > Always apply edits to your Working Layer - this makes it easier to back out any changes you're not happy with.
♦ Now - the fun part: bringing out the Nebulosity
♦ Image > Adjustments > Levels
> move the right-hand slider to the far right point of the histogram data display > click Ok
♦ again...Image > Adjustments > Levels
> now move the left-hand and centre sliders closer to the main histogram display - do this a little at a time. click OK
♦ Repeat the above two Levels adjustments as often as you like until you're happy with the result - but only a little adjustment each time.
♦ if the sky colour looks wrong you can adjust this by; Image > Adjustments > Levels > select middle eyedropper > find and click a part of the sky where it should be completely black > click OK
♦ Create a new layer
♦ at this stage you can adjust the hue/saturation/vibrance to suit selecting
♦ Image Adjustments > Brightness & Contrast or Image Adjustments > Hue/Saturation - do not over-egg this
Some final adjustments...
♦ next to bring out more detail click...Image Adjustments > Curves
♦ click (newer versions with Ctrl) eyedropper somewhere that the nebula appears more faint.
♦ click the histogram and pull the band up slightly (from middle-ish) to adjust the nebulosity.
♦ in the same histogram click slightly further down the band and drag it below the line > this will help to rectify the sky tone altered by previous step. when happy click OK
♦ some final fixes: create a duplicate layer and again...Image > Adjustments > Levels
♦ move the centre slider to the right to darken the sky
♦ make any final desired adjustments to hue/saturation and vibrance.
This image was achieved using the above workflow.
Good luck and clear skies, folks.