Super wide field Crescent Nebula, 2021

NGC 6888

A super wide field image of Crescent nebula in Cygnus constellation, 4,700 light years away. This is just 25 mins of data I took in a short and bright hot summer night (July 2021). I used a D810A on a FSQ-85ED and its flattener guided with a Lacerta MGEN-II Superguider.

Capturing the Light

The seeing was excellent and the temperature around 20C. As, this was a very short imaging session as summer nights here in UK are very bright and true astronomical nights don't last more than an hour every night (sometimes even less!), I didn't have to re-focus during the 5 shots.

I used the Takahashi FSQ-85ED dedicated 1.01x flattener and for the first time the excellent Lacerta MGEN-II Superguider. I had trouble finding guiding stars at the beginning due to the bright sky, but situation improved when astronomical darkness happened. 5 images of 5 minutes each at ISO 1250 were taken. Dithering was enabled as well, and the operation of the Nikon D810A exposures was done via the autoguider.

To focus, a simple bahtinov mask was used using the DSLR's zoom function in Live View mode.

Processing Details

PixInsight

  • ImageCalibration

  • Debayer

  • StarAllignment

  • DynamicCrop

  • ScreenTransferFunction

  • HistogramTransformation

  • BackgroundNeutralization

  • ColorCalibration

  • MultiscaleLinearTransform

  • CurvesTransformations

Lightroom

  • Initial post processing

Photoshop

  • Further post processing

Tech Card

Date / Location

18th July 2021, Warwickshire, GMT+0, United Kingdom, TEMP: 20C, Bortle Class 4 ~SGM: 21.20 mag./arc sec2

Equipment

Camera: Nikon D810A

Imaging Telescope: Takahashi FSQ-85ED

Correcting Lens: Takahashi Flattener 1.01x (composite focal length at 455mm and focal ratio at f/5.4)

Mount: iOptron CEM25EC guided with Lacerta MGEN-II Superguider

Image Quality

14 bit RAW (NEF)

Exposure time per image / number of composities and sensitivity

ISO 1250, 5 x 300" subs

Total Integration Time

25mins

Calibration Frames

16 Darks, 16 Bias, 24 Flats

Software

PixInsight 1.8.8-8

Lightroom

Photoshop