BSL Deep-Sky Imaging – ISO

1) ISO – Camera Sensitivity

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ISO controls how much the camera amplifies the light captured by its sensor.

High ISO (400–800 or higher):
Makes images brighter and allows you to capture objects with shorter exposures.

Low ISO:
Produces darker images but generally gives you less image noise.

Disadvantage of high ISO
It increases digital noise, making the image look grainy.

Important:
Increasing ISO does not make the sensor more sensitive to light ~ it amplifies the signal captured by the sensor.

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2. Camera Settings:

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Use Bulb (B) Mode:
When you need exposures longer than your camera’s normal shutter-speed limit.
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RAW:
Save photographs in RAW format rather than JPEG.
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Why RAW?
RAW files preserve more image information.
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This gives you greater flexibility when editing photographs, especially when adjusting brightness, contrast and details.

3. Turn Off Image Stabilisation:

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Stabilisation – Turn Off
When using a tripod, turn off lens image stabilisation.

Why?
The stabilisation system may try to correct movement even though the camera is already stationary.
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This can introduce unwanted vibrations and make your stars appear blurry.

4. Focusing the Camera:
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This is one of the most important steps in astrophotography.
The infinity symbol (∞) on your camera lens does not always give perfect focus.

Follow these steps:

• Point your camera towards a bright star or distant light.

• Turn on Live View if your camera has it.

• Zoom in digitally on the brightest star.

• Turn off autofocus because it struggles to focus in darkness.

• Set the lens approximately to infinity.

• Take a test photograph (around 20 seconds, as suggested by the book).

• Zoom into the photograph and inspect the star.

• Slowly adjust the manual focus ring until the star looks as small and sharp as possible.
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5. Why accurate Focus Matters

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Focus is extremely important because:
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• Blurry stars cannot easily be corrected during editing.

• Sharp photographs preserve more detail.

• Taking time to achieve accurate focus improves the final image.

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