top of page
Single Unprocessed CMOS Frame of Jupiter

Single Unprocessed Frame

4,600 Stacked and Unprocessed CMOS Frames of Jupiter.

4,600 Unprocessed Stacked Frames

(removes most noise)

Stacked and processed photo of Jupiter

Stacked and Processed Frames

(detail now appears)

Here's a set of performance examples of the 1000 Oaks mild light-pollution filter model LP-1

M57, no filter, 5 second exposure.

NO filter, 5 seconds exposure.

M57, no filter, 7.6 minute exposure.

NO filter, 7.6 minutes exposure.

M57, with filter, 5 second exposure.

WITH filter, same 5 seconds exposure.

M57, with filter, 7.6 minute exposure.

WITH filter, same 7.6 minutes exposure.

Here's The Effect Of Stacking Multiple Same Frames.

M57, full gain, 2.5 seconds exposure, 1 frame.

Full gain, 2.5 seconds exposure - 1 frame.

M57, full gain, 2.5 seconds exposure, 50 frames.

Full gain, 2.5 seconds exposure - 50 frames.

M57, full gain, 2.5 seconds exposure, 11 frames.

Full gain, 2.5 seconds exposure - 11 frames.

M57, full gain, 2.5 seconds exposure, 100 frames.

Full gain, 2.5 seconds exposure - 100 frames.

Below is an example of how to shoot long-exposures and go deep even in heavy light pollution.  The photos were done without any celestial tracking using just a camera on a stationary tripod.  The secret is to shoot multiple short exposures and then "stack" them together.

The stacked photo on the right was shot at an ISO of 3,200 but it actually has significantly less noise than the left photo shot at an ISO of 800.  Despite the right photo having an integrated exposure of 5.3 minutes on a stationary tripod using a 400mm lens, there are no star trails.

The limiting magnitude in the ISO 800 photo reached 14.8 and the ISO 3,200 photo reached 15.5 both for the same 5.3-minute exposure.  The skies had a limiting magnitude of just 3.5 and all photos used the same DSLR camera and 400mm lens (though with a different F-stop to balance the different ISOs).  There was no photo processing other than stacking.

Polaris - single unguided exposure
ISO=3,200 Exp=32x10 400mm F6.3 LM=15.3.j

The chart shows how to get the same limiting magnitude with your city telescope as with your same dark-sky telescope, by increasing your magnification.  A star is a point so it will not dim with magnification but the field's background darkens as its light spreads out.

CMOS telescope limiting magnitude in light pollution.

100% crop of the single-frame ISO 800 photo showing several hundred hot-pixels due to the long single exposure.

100% crop of the stacked ISO 3,200 photo.

Crop - ISO=800 Exp=1x320 secs.jpg
Crop - ISO=3,200 Exp=32x10 400mm F6.3 LM

Below is a 100% crop of each photo.  Because of stacking the ISO 3,200 multiple exposure photo has...,

  • only 3% of the original digital noise

  • reduced chromatic aberration

  • no chroma noise

  • no hot pixels

  • no star trailing

  • fainter stars

The ISO 800 single-shot photo has none of that.

ISO = 3,200, exposure = 32 x 10 secs, 400mm lens.

ISO = 800, exposure = 1 x 320 secs, 400mm lens.

The White Zone

An Urban Astronomer's Light Pollution Guide to Balcony Imaging

bottom of page