IC1396 in narrowband, 2 panel mosaic

[symmetal]

Taken over the past two months in many sessions as the weather's been very uncooperative.

Each panel was 1 hour each of Ha, Oiii and Sii. Processed in PI using a blend of SHO and ForaxX palettes and finished off in PS. I usually add just the Ha stars back in as mono, but with Erakis, (Garnet Star) showing significant circular diffraction rings from the semi-circular cable routing of the RASA, StarXT wouldn't touch it in Ha or Sii, though did remove it in Oiii, the rings being closer together in this case, possibly helping. I therefore processed the three separate star images the same as the starless images as far as the colour palettes went, and added them back in PS. The range of colours produced don't look too abnormal and Erakis doesn't look so out of place now.

RASA 11 and ASI6200MM with Astronomik FastFR 2" filters on an EQ8. Binned 2x2 to keep final image size down. I notice that none of the filters give halos either which is good. 🙂 A full frame camera gives a 3 deg x 2 deg FOV at 620mm FL so can manage fairly large targets. Not wanting to rotate the camera for framing, I opted for 2 panels instead. As the image is fairly noise free, I think for binned mosaics 30 mins of each filter may be OK. I'll do test stacks of just half the frames taken to see.

I did find that StarAlignment in PI gave poor stars using 'auto' resampling where it uses Lanczos-3 when little to no resizing is needed. Oiii was the worst for this. This gave good backgrounds but the stars were smaller and squarer with undershoots giving black lines around bright stars. The 'clamping threshold' to reduce the undershoots had little effect.  Lanczos-4, also gave bigger square stars and Lanczos-5 gave large diamond stars. In the end I used Bicubic B-Spline which was the best for not messing with the star shapes but did make the whole image noticibly softer. Adding Ha back as luminance tended to mitigate this.

StarXT can give round patches on the Oiii background around bright stars where Lanczos resampling was used, but not when using Bicubic B-Splines.

Note the colourful planetary nebula top right of Erakis and the lone small blue patch half way down on the left. The bright star at bottom left is actually a double star rather than an odd optical distortion. 🙂

Alan

 

Edited September 3, 2023 by symmetal
Added name to image

[windjammer]

Beautiful.  I love the Foraxx palette. Bracken has this as 2.6o x 3.4o, an enormous FoV! Spectacular - how many hours went into this ?

Simon

[symmetal]

55 minutes ago, windjammer said:

Beautiful.  I love the Foraxx palette. Bracken has this as 2.6o x 3.4o, an enormous FoV! Spectacular - how many hours went into this ?

Simon

Thanks very much. 😊A full-frame camera helps with getting a larger FOV if the scope can handle it. 🙂 Six hours in total. One hour per filter per frame.

This is Foraxx mixed 50:50 with standard SHO palette. Foraxx on it's own gives more red rather than the orange/yellows seen here.

Alan

[symmetal]

Apparently, just one star, HD206267, shown on the left of the crop below, is responsible for all of IC1936's appearance. It's ionizing radiation compressing the gas to form the circular edge. The trunk itself is a source of star formation and 'winds' from these stars pushing back against this radiation have formed the dense compressed left edge of the 'trunk'. HD206267 is actually a double star as can be seen.

Alan

[tooth_dr]

On 03/09/2023 at 18:30, symmetal said:

HD206267

Wonderful image Alan, and fantastic FOV.  I read this about the star too, fascinating science