The Helix Nebula
The Helix Nebula
NGC 7293, large planetary nebula in Aquarius
<– My first encounter with the Helix nebula was with a C11 SCT (F/10). It was one of the 1st DSOs I imaged after adding a guide scope to my setup. Expectations were high, and the end result less impressive than expected. (22,5 min at F/10)
When offered the opportunity to image with a 10″ Orion Astrograph (F/3,9) 1000mm focal Length beginning August 2013, the Helix was the 1st target on my list. Faster optics with a more appropriate FOV made it ideal for the Helix, to combat coma the Astrograph was fitted with the Baader MPCC.
My workflow on the image:
Acquisition, calibration and integration:
Nebulosity:
I captured 11x 240sec before switching to 9x180sec (with the target descending into LP the histogram was getting over-exposed)
Darks: I was making the most of the imaging opportunity and did not shoot darks on the night. Taking note of the temperature, I shot darks with the camera placed in the fridge a few nights after.
Bias Frames: 100 Bias frames (10 for each dark)
Flats: No flats shot (not ideal, but something DBE in PixInsight can correct)
PixInsight:
1.) The 240 and 180 sec lights were calibrated with corresponding darks/bias
2.) All calibrated files registered together, then integrated
Editing (PixInsight)
I’m still fairly new to PixInsight and this is the current workflow I follow:
1.) DynamicCrop
2.) DBE
3.) Colour Calibration
4.) Histogram Stretch
5.) HDRmultiscale (Star mask)
6.) Curves Transformation: Saturation
7.) Histogram Stretch
*I opted for noise reduction in PhotoShop (not usually)
Finishing off in PhotoShopCC
1.) Noise reduction
2.) Image layers / Helix:
a- ansharp mask
b- Image dodge
c- noise reduction
d- unsharp mask
e- curves
3.) Global curves & levels
4.) Global saturation
5.) Individual slight saturation on a few stars / sharpening
My opinions:
This is a perfect entry-level telescope at its price point (A smaller 8″ is also available). Fitted with the MPCC the stars remained round in the corners. It’s difficult to comment on the scope’s detail capturing ability as my PHD graph was less than ideal, but despite this I’m impressed with the level of detail I was able to extract. It’s fast at F/3,9 – but a watchful eye on the histogram is needed as it’ll be easy to overexpose the image in light polluted skies (or use filters)
The crayford focuser was a pleasure to use, smooth and with fine focus and ability to lock focus down it proved to keep the target in focus the entire imaging session. I find that my stars lacked colour, my APO triplet is renowned for capturing excellent colour & detail, but comparing the 2 OTAs would be like comparing oranges with apples.
Good acquisition and editing techniques will greatly bridge the price gap between an affordable OTA like this and other more renowned scopes (to a point). First priority should be to understand and master the fundamentals of imaging and editing before investing in a high end telescope or camera.
About the Image:
10″ Orion Astrograph
Celestron CGem DX
Canon60Da
Guiding SSAG & PHD
Acquisition: Nebulosity
Processed with PixInsight & PhotoShopCC
71 Minutes (9x 180Sec: 27 Min + 10 Darks / 11x 240Sec: 44Min + 10 Darks)
ISO800
100 Bias Frames
4 August 2013 / Magalies Mountain Sanctuary, South Africa
Flickr: http://www.flickr.com/photos/astro-tanja/9534770287/in/photostream/
Also imaged with the Orion Astrograph that night, the Sculptor Galaxy:
http://www.flickr.com/photos/astro-tanja/9519906810/in/photostream/
