M42/43 from very short exposures

An ALTAIR STARWAVE 60 ED Imaging Refractor with an 0.8 reducer/flattener at f/4.8 was mounted on an AVX mount. An Altair Quadband, narrowband filter was placed in the optical train in an Altair magnetic filter holder. An SVBONY SV605CC OSC cooled CMOS camera was mounted on the scope. This camera produces no significant amp glow.

An extension cord was used to connect the mount to the Hand controller which was indoors with the Imaging computer. The hand controller was connected to the imaging computer via USB to connect to the INDI server on the virtual Linux machine.

As usual, the mount was placed on marks on the concrete base which give a reasonable polar alignment. AstroDMx Capture passed the time, altitude and location coordinates to the hand controller via the INDI server. The hand controller which now contained all of the correct information was set to its previous alignment and was unparked by AstroDMx Capture.

These data were obtained during experiments on the spacing for the focal reducer and exploited a short period of relatively clear sky.

AstroDMx Capture for Windows was used  to send the mount/scope to the star Rigel for focusing using a Bahtinov mask, and then to the Orion nebula. The field was plate solved and the object centred.

AstroDMx Capture was used to capture 50 x 5s exposures of the Orion nebula. This exposures enabled the capturing of the trapezium region without overexposing this region

The data were stacked and partly processed in Siril and post processed in the Gimp 2.10 and Neat Image.

The stack was of a total exposure time of only 250s but nevertheless, when the resulting image was stacked, considerable detail was revealed.

The Orion Nebula

The RGB image was derived from quadband narrowband data. By working with colour curves and channel mixing it is possible to produce pleasing alternative renderings

Alternative rendering

It is interesting to note the amount of detail that was captured by 250s worth of 5s exposures. It would have been better to capture 100 images as this would have resulted in an increase in S/N by a factor of 10 rather than the 7.07 that was produced by the 50 images. Also if a number of significantly longer exposures had been captured, considerably more interstitial nebulosity would have been detected whilst overexposing the centre of the nebula. The construction of a high dynamic range image would have been possible, to combine the fine structure of the trapezium region with the billowing nebulosity at the extremities of the nebula and the surrounding region