The Pacman and Rosette nebulae were imaged with AstroDMx Capture, a William Optics Super Zenithstar 81mm ED Doublet APO refractor at f/5.5 with x 0.8 reducer/flattener, and an Altair 2" magnetic filter holder v2 fitted with a 7nm H-alpha, or a 6.5nm OIII filter or a 7nm SII filter. An SVBONY SV605MC monochrome, cooled CMOS camera was placed at the focus.
The equipment used
Part way through the imaging session we found that the ZWO AEF had failed likely due to the cold temperatures. A cursory internet search revealed that this is common and that the EAF incorporates domestic components rather than industrial components; it is not guaranteed to work at temperatures below minus 5 degrees C. This was a disturbing discovery. Whilst the 5 volt focuser that receives its power via the USB (in our case via an active, powered cable) is more convenient than the more powerful 12 volt version that it replaced, which required a separate 12 volt power supply, (as does the Pegasus FocusCube 2 that we use on a different telescope); the convenience is completely negated if it is necessary to do what we did to solve the problem, to fit a powered lens-warming, anti-dew strip to keep the focuser warm:
The lens-heater strip fitted to the AEF
As usual, the mount was placed on marks on the concrete base which give a fairly good polar alignment. AstroDMx Capture passed the time, altitude and location coordinates to the hand controller via the AstroDMx Capture integrated INDIGO client, and server which was running on the imaging computer. The hand controller which now contained all of the correct information was set to its previous alignment and was unparked by AstroDMx Capture.
AstroDMx Capture was used to send the scope/mount to a Altair to check focus with a Bahtinov mask.
AstroDMx Capture plate-solved and sent the scope/mount to the Pacman nebula and captured 6 x 5-minute exposures through each of the H-alpha, OIII and SII narrowband filters, giving a total exposure time of 90 minutes.
AstroDMx Capture capturing Data on the Pacman nebula through the H-alpha filter
AstroDMx Capture capturing Data on the Pacman nebula through the OIII filter
AstroDMx Capture capturing Data on the Pacman nebula through the SII filter
The data were registered and stacked in Deep Sky Stacker. The OIII and SII light frames were registered with the best H-alpha light frame so that the three channels would be perfectly registered. The data were processed in Gimp 2.10, the Starnet++ Gimp plugin, Neat image and Photoshop CS2. The Channels were balanced in the Gimp 2.10, combined into false colour image palettes and gently selective colour processed to achieve the required colours of the Palettes used.
The Pacman nebula SHO, Hubble Palette
The Pacman nebula HOS, Canada, France, Hawaii Telescope Palette
AstroDMx Capture plate-solved and sent the scope/mount to the Rosette nebula and captured 6 x 5-minute exposures through each of the H-alpha, OIII and SII narrowband filters, giving a total exposure time of 90 minutes.
AstroDMx Capture capturing Data on the Rosette nebula through the H-alpha filter
AstroDMx Capture capturing Data on the Rosette nebula through the OIII filter
AstroDMx Capture capturing Data on the Rosette nebula through the SII filter
The data were registered and stacked in Deep Sky Stacker. The OIII and SII light frames were registered with the best H-alpha light frame so that the three channels would be perfectly registered. The data were processed in Gimp 2.10, the Starnet++ Gimp plugin, Neat image and Photoshop CS2. The Channels were balanced in the Gimp 2.10, combined into false colour image palettes and gently selective colour processed to achieve the required colours of the Palettes used.
The Rosette nebula SHO, Hubble Palette
The Rosette nebula HOS, Canada, France, Hawaii Telescope Palette
All of the procedures produced the required results and the integrated INDIGO client in AstroDMx Capture worked well for mount and focuser control. It was disappointing to discover that the ZWO AEF was so susceptible to the cold, but the heated lens anti dew strip solved the problem. In fact on the highest heat setting, the temperature of the AEF reached double Celsius figures despite the cold environmental temperature with enhanced radiative heat loss due to the clear sky.
