Atik 314L – First Light: Rosette Nebula in Ha – 18/04/2018
I recently acquired an addition to my astronomical imaging arsenal. A mono Atik 314L (not the 314L+), came up for an extremely good price on an astro-classifieds site, and finally, I bit the bullet and took the dive headlong into CCD imaging. I’ve always said I would stay away form CCD imaging until the time was right. Finally, the stars (ahem) aligned, and this offer was too good to resist!
The Atik 314L is basically identical its well-used and well-loved (in the astro community) successor, the 314L+, in all aspects except one – the cooling system. Both have cooled CCDs that go down to about 25 degrees Celsius below ambient temperature, reducing the noise in the captured images significantly. However, whereas the 314L+ has ‘setpoint’ cooling (where you can control the temperature), the 314L has fixed cooling (where it’s always on maximum). To me, this has absolutely no bearing on anything, as I would always use the camera with the cooling on full anyway. The only real reason I’ve seen for using variable cooling is where you want to take darks at a specific temperature. However, a big part of the draw of this camera for me is the very low noise images it produces – and some testing by a good friend has basically worked out that using darks with this particular sensor can actually introduce ‘negative’ noise, and you end up with a worse result. Dumping darks is one of the reasons for going for this particualr camera (more time for grabbing photons!), so I’m hoping he’s right!
On my first night out with it, I decided to go the whole hog, and try some Ha imaging, as I’d also had an Astronomik Ha-CCD filter that I’d bought a long while back for use with the Lodestar for live viewing. I have, for now, decided to keep with the tried and tested formulat of APT for capture, and PHD for guiding. APT works well on a touchscreen tablet, as it’s interface buttons are, in general, a decent size for prodding with cold fingers on a freezing night…! Its very cheap to buy and works with multiple different cameras. Go to https://ideiki.com/astro/Default.aspx for more details…
Setting up the Atik in APT was a breeze, and I was soon grabbing 5 second shots to focus (using Beetlegeuse and a Bahtinov mask). A Bahtionov mask, which you place over the front of your scope, allows focussing by the alignment of three spikes. When all three are in perfect symetrical alignment (as in the shot to the right), you know you’re in about as good focus as you can be. This is vital for all types of imaging, as being out of focus os one of the most annoying ways that data can end up being less usable.
With PHD guiding the scope via the Lodestar and the Altair 10×60, I grabbed a few of what I considered at the time test shots, and managed to get lovely round stars on a 5-min exposure, so increased 10-min exposures, and captured four with no issues, giving a total of 45 minues on the Rosette.
I didn’t really have any intention of processing these. I’m not used to 10-minute exposures, and kind of didnt expect them to come out with round stars. Turns out that they were fine. I usually grab 4-minute or maybe 5-minute subs, so 4.5x 5 minute wouldnt give enough data to really get anything good out of. 45 minutes, however, is a different prospect, especially with the increased QE (Quantum efficiency – basically how good the sensor is at converting photons to electrical signals), plus the lack of a bayer matrix on the mono CCD sensor. A Bayer matrix is the component of colour sensors that filters the colours of light into RGB before it hits the sensor, and just the presence of the Bayer matrix reduces the actual amount of light recieved at the sensor surface massively.
I stacked in MaximDL (using the SD Mask stacking method), and then used the digital development facility to do the initial strethcing of the linear image. I then process in Photoshop CC (making use of Steve’s Astro Actions and Annie’s Astro Actions) and Lightroom CC. I find Lightroom’s noise reduction fantastic, and it’s sharpening and ‘clarity’ fucntions, when used sparingly, can really make an image pop!
Anyway – I ended up with the following result:-
I’m blown away by the quality of this image. The Bok globules (the dark lanes to the bottom-right of the ‘donut’ are gorgeously clear considering the small aperture of the scope used. For just 45 minutes of data, the image itself is very low in noise. The most amazing thing to me about this image, is that it required NO calibration frames….! This is a massive deal. The taking of dark images, when you have to break doan your kit after each session, is a real pain, and generally means less time for taking lights, as I have to plan in time to do the darks before I power everything down and put it all away.
Im looking forward to developing my imagin via this new route. The ability to image in moonlit skies in Ha is also exciting. Very often, good clear nights fall on exactly the same ones that the moon happens to be sat there high in the sky, washing everything out! Hydrogen Alpha filtering is much more tolerant to this moonlight. Can’t wait to start taking advantage of the increased imaging time.
As usual – watch this space!