|Designation: Caldwell 92, NGC 3372, in constellation of Carina.|
|Visual magnitude: +1.0.|
|Apparent size in arc-minutes: 120′ x 120′.|
|Diameter in light years: 349.|
|Distance in light years: 10,000.|
One of the most prominent nebulae in the night sky, the Eta Carinae Nebula lies thirty degrees from the South Celestial Pole. It includes several star clusters, the dark Keyhole Nebula and the Homunculus Nebula – the remnants of an outburst from the star Eta Carina nearly two centuries ago.
Here’s an image I took earlier of the Homunculus Nebula. No I didn’t. It’s a Hubble image:
This is my first two hour exposure and I think it helped bring out some of the detail. With twilight ending at 9.20 pm and the still bright Last Quarter Moon rising at 11.20 pm that was all I had available.
It was great to be outside again under a clear night sky, after nearly three months of raging bush-fires – which were mostly doused by torrential rain last week. Only twenty-three fires are still burning in NSW now – and they are all classified as “under control”. The wind and rain has swept away the hazardous air pollution at last!
The “imaging holiday” has enabled me to improve some methodology.
One improvement I’ve made is subtracting flat/bias frames for the first time, as many of my images have been showing signs of pollution from dust particles. The following image shows the flat image taken just prior to my imaging session:
This crud in my optics has been showing up on all of my images recently and hopefully I can make it a thing of the past, by improving my flat subtraction technique and making it part of the regular setup routine.
I’ve also made some improvements to my polar aligning techniques, lubricating the mount to smooth the alt-az adjustments and swapping my PoleMaster camera and software for the polar aligment routine in SharpCap.
The latter was forced on me after replacing my old lap-top with a new one, only to find the PoleMaster camera and software wouldn’t work properly on the new one. I’ve reported this to QHYCCD but don’t hold out much chance of a favourable outcome anytime soon, with China in a lock-down over the Corona Virus Covid-19.
However the result using SharpCap was the most accurate polar alignment I’ve ever had, with SharpCap telling me the alignment achieved was 00° 00′ 06″. If I can do that every time, I’ll be happy!
|Date: 2020-02-14||Sky brightness (e/px/sec): 0.89|
|Exposure: 68×106.6 sec = 120 min.||Gain setting: 10|
|Camera: ZWO ASI 071 MC Pro||Type: CMOS 28.4mm 16 Mpx|
Location: outer suburban. Conditions: clear sky, no Moon
This image was not cropped.
My images are captured with Sharpcap-pro software using the live-stacking feature, with dark subtraction and in-the-field image processing. Guiding by PHD2, using Orion 80mm guide scope and ZWO ASI120 camera. Image post-processing is carried out using GIMP freeware.
Also in image:
Follow this link to see my image with Astrometry.net annotated overlay.
|SkyWatcher Esprit 120 mm apochromatic 3-element refractor.|
|840 mm focal length @ f/7 with field flattener.|
|Baader L-Booster UHC-S light pollution filter 2458276.|
|SkyWatcher EQ6-R Pro mount, with a polar error of 00′ 06″|
|ZWO ASI120 guide camera, using PHD2 software.|
|QHYCCD PoleMaster polar aligning camera.|
Images © Roger Powell
|I’m one of the founder members of Macarthur Astronomical Society, Australia. 🙃|
|[ZWO ASI071MC Pro]|
Output Format=FITS files (*.fits)
Frame Rate Limit=Maximum
White Bal (B)=99
White Bal (R)=60
Auto Exp Max Gain=300
|Auto Exp Max Exp M S=30000|
Auto Exp Target Brightness=100
Anti Dew Heater=On
Apply Flat=C:\Users\powel\Desktop\SharpCap Captures\2020-02-14\Capture\flats\20_28_31.png
Subtract Dark=C:\Users\powel\Desktop\SharpCap Captures\darks\ZWO ASI071MC Pro\RAW16@4944×3284\106.6s\gain_10\dark_6_frames_-10.0C_2020-02-14T10_27_56.png
Display Black Point=0
Display MidTone Point=0.5
Display White Point=1