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M20 the Trifid Nebula and M8, the Lagoon Nebula, a composite image consisting of a luminance image taken in hydrogen alpha light, and a colour image.

First light with an Orion 80ED refractor. See below for more comments and detail on the performance of this telescope.


Image info

Telescope:  Orion 80ED apochromatic refractor at f/7.5

Focus:  Prime focus

Filter:  Astronomik Hydrogen Alpha 13nm FWHM (Luminance), LPR Filter (RGB)

Mount:  Vixen GPD with Skysensor2000

Camera:  Modified Canon EOS 300D, at ISO800

Guiding:  700mm refractor guidescope, SAC7 camera, autoguided with Guidedog software

Exposure:  Total 70 mins (Luminance) and 38 mins (RGB)

Date:  28th & 29th July 2005

Processing:  RAW file conversion, Offset and Dark subtraction, flat fielding, registering and stacking done in IRIS.  Used the asinh function to enhance colours.  Curve stretching and a little unsharp masking in Photoshop CS.  Composited with the Luminance image using a technique described by Rob Gendler (Method 2) then colour saturation enhancement with Luminance Layering.  Noise reduction in Neat Image.


I'm impressed with this inexpensive telescope, at least for narrow-band imaging!  At the centre of the field, stars are tight and sharp.  With rescaling to 50% (not enough to squeeze 6 megapixels onto the screen), the image shows very good sharpness.  Note the fine detail visible.


Below are crops, from left, the centre of the field, top left, and bottom left - all at 100% scale.

The centre is superb.  Stars are often just 2 pixels across.  However coma is evident at the corners at 100% scale, but look acceptable at 50%.

I'll reserve judgement on RGB performance, however.  I noticed that the blue and green frames showed out-of-focus stars, whereas red was in focus.  This may be due to IR light leaking through the microlens filters and into the G and B frames.  I have placed an order for an IR block filter and will soon see if this hypothesis is correct.


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