by AVAO » Fri Jan 20, 2023 9:04 pm
Ann wrote: ↑Fri Jan 20, 2023 8:23 pm
Holmberg IX has a low surface brightness in optical and infrared light. It is only bright in the ultraviolet. In optical light, it is much fainter than the bluish spiral arms of M81. But I disagree that this little galaxy is invisible in today's APOD. It is plainly there, below M81, in the 7 o'clock position.
...
Ann
Sorry Ann, but I don't agree with that either. The image has a relatively poor resolution and the galaxies shown are severely distorted on closer look. Holmberg IX is a nebula with no single star visible and no hint of blue for reference.
For me, however, some things become clear when I follow the author's original text on instagram. In honor of - that photographers, who define themselves as "beginners", are also making it onto the APOD throne. Congratulations.
"The real highlight in this image, however, is the integrated flux nebula (IFN, the faint nebulosity all over the image). This nebula lies beyond the main body of the Milky Way. It is a component of the interstellar medium, composed of dust particles, hydrogen and other elements. It is illuminated by the energy from the integrated flux of all the stars in our galaxy (hence it’s name). It is extremely difficult to shoot, as it requires very dark skies, long integration time and careful processing. Thus, I’m very satisfied that I could capture it as a beginner in my first attempt!"
![📸](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f4f8.svg)
: Canon EOS R6 (stock)
![🔭](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f52d.svg)
: Canon RF 100-500mm f/4.5-7.1L | EQ-modified Skywatcher AZ GTI
![⚙️](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/2699.svg)
: 110 x 60 sec (1h 50min, unguided) • f/8 • 500 mm • 3200 ISO
![📍](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f4cd.svg)
: Telfs, Austria
![🇦🇹](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f1e6-1f1f9.svg)
; Bortle 3
![🌔](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f314.svg)
: 28 % Waxing Crescent
![✍️](//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/270d.svg)
: SiriL; GIMP; Darktable, StarNet
[quote=Ann post_id=328628 time=1674246197 user_id=129702]
[quote=AVAO post_id=328624 time=1674239793 user_id=144694]
.
How to explain that Holmberg IX is almost invisible on today's APOD?
Compare to: [url]https://live.staticflickr.com/65535/52246306840_153c2f9cb7_o.png[/url]
[/quote]
Holmberg IX has a low surface brightness in optical and infrared light. It is only bright in the ultraviolet. In optical light, it is much fainter than the bluish spiral arms of M81. But I disagree that this little galaxy is invisible in today's APOD. It is plainly there, below M81, in the 7 o'clock position.
...
Ann
[/quote]
Sorry Ann, but I don't agree with that either. The image has a relatively poor resolution and the galaxies shown are severely distorted on closer look. Holmberg IX is a nebula with no single star visible and no hint of blue for reference.
For me, however, some things become clear when I follow the author's original text on instagram. In honor of - that photographers, who define themselves as "beginners", are also making it onto the APOD throne. Congratulations.
"The real highlight in this image, however, is the integrated flux nebula (IFN, the faint nebulosity all over the image). This nebula lies beyond the main body of the Milky Way. It is a component of the interstellar medium, composed of dust particles, hydrogen and other elements. It is illuminated by the energy from the integrated flux of all the stars in our galaxy (hence it’s name). It is extremely difficult to shoot, as it requires very dark skies, long integration time and careful processing. Thus, I’m very satisfied that I could capture it as a beginner in my first attempt!"
📸: Canon EOS R6 (stock)
🔭: Canon RF 100-500mm f/4.5-7.1L | EQ-modified Skywatcher AZ GTI
⚙️: 110 x 60 sec (1h 50min, unguided) • f/8 • 500 mm • 3200 ISO
📍: Telfs, Austria 🇦🇹; Bortle 3
🌔: 28 % Waxing Crescent
✍️: SiriL; GIMP; Darktable, StarNet