ROAST ::

Update, June 13/14
Another go last night, and here’s a mega stack of the two sessions:

Some more detail, and the surrounding nebulosity has been brought out a bit more. I tried raising the gain to 70 and reducing exposure time to 15 seconds, mainly to see what diference it made; the increased noise is probably due to the extra gain, so I won’t be trying that again. There were 36 failed shots this time, some satellites but mostly because it was very windy resulting in smeared stars.

Details:
Target: C34, Witch’s Broom nebula
Time:
A: 2026-06-11 00:17..01:23
B: 2026-06-14 00:11..01:39
Equipment: Dwarf Mini, Duo-Band filter
Integration:
A: 49mins (98×30secs, +7 failures), gain 60
B: 66mins (264×15 secs, +36 failures), gain 70
Total: 1hr 55mins
Conditions: Clear but windy, Bortle 7
Processing: PhotoDesk equalisation, gamma (blue and rgb), balance

Original post
June 10/11, another few hours of clear skies. After doing the wide mosaic of the Veil Nebulae recently, we were intrigued by the colours in the Witch’s Broom part. They weren’t very prominent so here’s another go, this time concentrating on the Broom, Caldwell 34.

The Dwarf Mini has two main filters available: Astro, which enhances infrared and is mainly used for galaxies and solar system objects, and Duo-Band, which is designed to emphasise the Hα and O III parts of the spectrum — that is, ionised hydrogen at 656.3nm and oxygen at 500.7nm. These emissions are prominent in nebulae and are shown as reddish and bluish colours respectively. This filter also reduces glow from moonlight and general light pollution (street lighting and so forth), so is pretty useful.

I didn’t have time for many exposures, so this is intended as the first tranche of a mega-stack. It’s a fairly faint object and needs hundreds of shots — perhaps 3 or 4 hours of integration — to really bring it out. I’m also not too happy with the processing, but it’s a start.

Details:
Target: C34, Witch’s Broom nebula
Time: 2026-06-11 00:17..01:23
Equipment: Dwarf Mini, Duo-Band filter
Integration: 49mins (98×30secs, +7 failures), gain 60
Conditions: Clear, Bortle 7
Processing: PhotoDesk equalisation, gamma (blue and rgb), balance

And so to bed…