When a low-mass star (less than 1.4 solar masses) dies, it creates incredibly fascinating structures. The mostly shell-shaped gas envelopes trace the shock front that is formed from the matter from the inner stellar regions. The planetary nebula moves rapidly through space at a speed of about 125 km/s (450,000 km/h), interacting with interstellar matter to create a sharply defined shock front in the ‚direction of travel‘. This leads to backward turbulence and the dissolution of the gas cloud (Gutermuth).
In the past, these objects looked like planets, which is why they were given their misleading name – planetary nebulas (PN).The PN are also such exciting objects because their lifespan is simply ‚ridiculously short‘ in astronomical terms – only a few tens of thousands of years.
Our PN, also known as Sh2-188, is located in the constellation Cassiopeia (CAS), directly below the star δ CAS.
The constellation CAS is circumpolar, so it can be seen all year round. However, ‘seeing’ it is not quite so easy: the PN is not visually visible and shines predominantly in H-alpha. In astronomy and physics, H-alpha or Hα refers to the brightest spectral line of excited hydrogen in visible light. It lies in red light at a wavelength of 656.28 nanometres. As an H-alpha emitter, Sh2-188 is normally a narrow-band target and is therefore usually captured with narrow-band filters and mono cameras (my mono camera is currently still in Singapore and will hopefully reach me at the end of November – filter wheel and L-RGB and narrow-band filters are already there :-)).
I just wanted to see what an OSC (colour camera, currently the ASI294MC Pro) can do here. With the standard gain of 121, which I normally use, you can’t see anything at all. Only at gain = 250 were the structures discernible in the 300s long exposures (see the above screenshot from ASIAIR).
As soon as the mono camera and the HSO filters are ready for use …
…the PN Sh2-188 will definitely be the first target. A foretaste of a really good result can be found with quite comparable equipment (250 Newtonian and the ZWO ASI 2600 MM Pro) on Astrobin. A total of 38 hours of integration with RGB (10,10,40min) and narrow band filters H-alpha (11h), SII (15h) and OIII (11h)
Test EcoFlow RIVER 2 Max (512 Wh) as power supply
For mobile use (i.e. usually somewhere in remote, dark places …), the entire equipment must be powered by a rechargeable battery. I now had the opportunity to test such a part (on my roof). The model mentioned above (a LiFePO4 battery) has 512 Wh and my expectation was that this should be enough for a photo session (i.e. one night).
I started at about 17:00 with the set-up – i.e. fan-assisted cooling, heating sleeves on the guiding camera and heated dew cap, as well as the usual consumers: cooled camera, ASIAIR and mount. The power consumption was initially between 42 and 45 watts and rose to 65 watts when the mount was swivelled (during polar alignment)!
Left: Start at 17:00 (95%, I unplugged the iPad straight away anyway …), Right: 20:30 (55%), so in 3.5 hours a whopping 40% less …
As things stand at the moment, I can just about make it past midnight… the ‘mobile’ power supply is cut off at 10.30pm with 30% remaining. For the remaining hours, the power comes from the socket again…
CONCLUSION: For mobile use, I would probably need at least a 1,000 Wh power station (especially as the temperature today was still a mild 6°C to 3°C…). With a full setup, I therefore reckon with approx. 60 W power (without reserve).
1. Session with OSC (color camera)
From 100 frames, 73% were integrated, thus achieving an exposure time of 6 hours. I was actually pleasantly surprised that this target was visible at all with an OSC. Seeing was also not particularly good (FWHM=3.668 in the median). Here is the first rough processing:
