The equipment used was an Altair Starwave ASCENT 60ED doublet refractor with field-flattener, a Pegasus FocusCube v2 focuser, an Altair Hypercam 533C 14 bit OSC CMOS camera and a PlayerOne Phoenix 2" filter wheel all mounted on a Celestron AVX GOTO mount. An SVBONY SV165 guide scope with a natively connected QHY-5II-M guide camera was used for PHD2 multistar pulse auto-guiding via an INDI server. The mount, and focuser were controlled by AstroDMx Capture via the INDI server and the Altair Hypercam 533C was controlled natively.
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The Equipment used
Altair dual-band 2" S2O3 and HaO3 filters were used.
AstroDMx Capture running on an Ubuntu mini computer was used to capture 5-minute exposures through each filter of the Rosette nebula and C50 the Harp cluster as well as of the Seagull nebula IC2177. A total of 1hour 30minutes worth of data: 45 minutes through each filter were captured of each nebula.
Pixinsight was used to stack and calibrate the data. The data were further processed in PixInsight, GraXpert, SetiAstroSuitePro and Gimp3
The Seagull nebula IC2177
Hubble palette
The Rosette nebula and the Harp Cluster
Hubble palette
Dual-band HaO3 and S2O3 are real game changers for narrowband imaging as they allow OSC cameras to be used properly for narrowband work. HaO3 dualband filters first made their appearance in 2018-2020 whilst S2O3 didn't appear until 2023-2025 as manufacturers waited to confirm the commercial success of HaO3 filters. We have found that the results from these dual-band filters and OSC cameras are as good as those produced by monochrome cameras and separate Ha, S2 and O3 filters. An advantage of using Dual-band filters and an OSC camera is that two wavelengths are captured simultaneously and twice as much O3 data is captured as would be captured with a monochrome camera and Separate Ha, S2 and O3 filters. Consider an imaging session of three hours on one object. With a monochrome camera and separate Ha, S2 and O3 filters: One hour would be spent capturing data on each element. With an OSC camera and dual-band HaO3, S2O3 filters, one and a half hours would be spent capturing Ha and S2 data and three hours would be spent capturing O3 data. It seems to us that these facts help to level up the capabilities of the two imaging systems.
Steve Wainwright and Nicola Mackin
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