IC 410

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IC 410 IC 410
Sh2-365
Tadpole Nebula
Emission Nebula in Auriga

Click here for higher-resolution versions: 40% (1543x1478) 65% (2507x2402) 100% (3857x3695)

Click on image to cycle through the five versions of the image (described below and labeled on the lower left corner of each image)

IC 410 is an emission nebula, visually located in the constellation Auriga; it is part of a much larger star-forming region. The nebula, itself a star-forming region, is predominantly red in the true-color versions, because (i) ionized hydrogen emits in the red part of the spectrum; (ii) the dominant emissions captured in this photo are from hydrogen being ionized (stripped of its electron) by the energetic young stars being formed inside the nebula. Unusually, the emissions from ionized oxygen, which are blue-green in color, are quite strong, accounting for the bluish tint to much of the nebula. The young star cluster NGC 1893 is integrated within IC 410 (near the central part of this image), having been formed in that gas cloud.

The two squiggly shapes above and to the left of the center of the image are known as "the tadpoles" (giving the nebula its name), catalogued as Simeis 129 and Simeis 130. These are similar in origin to the famous "Pillars of Creation," and are being eroded by the stellar winds from the new stars being created; the "tails" point away from the star cluster, because they are gas being blown away from the "head" of the tadpoles. To see a high-resolution crop of the tadpoles, click here

The dark splotches are obscuring gas (gas dense enough to absorb all the light coming from the other side), somewhere between IC 410 and us.

The field is thought to be about 12,400 light years from Earth; at that distance, this field is about 136 light years across; the "tadpoles" are about 10 light years long. Visually, this field is about the width of a full moon (although very dim by comparison).

I imaged this nebula once before, 20 years earlier than this image was taken. I was (and still am) quite pleased with the old images; but to see what a bit of acquired skill and better equipment/software can do, compare this current image to my original one here.

I have presented this object in five different formats; I like each one in its own way. This is the order in which they appear as you cycle through (by repeatedly clicking on the photo, waiting for each to download; each is labeled in the lower left corner), starting with a reddish version:

(i) A true-color version (the top photo in the stack, labeled "LRGBNB" in the bottom left), with the color created by imaging through red, green and blue filters (with a significant amount of Ha and OIII data blended into various channels, in varying percentages; Ha emissions are in the red part of the spectrum, and OIII emissions are blue-green, so I have blended Ha into the luminance layer and the red channel, and OIII into the green and blue channels).

(ii) A true-color version (the second photo in the stack, labeled "LRGB" in the bottom left), with the color created by imaging through red, green and blue filters only (no Ha or OIII data included). It is interesting to see how much the addition of the Ha and OIII increases the detail, but I like the more-colorful stars in this version.

(iii) A version in the traditional Hubble palette (third in the stack, labeled "SHO" in the bottom left); a lot of the Hubble photos, including and especially the famous "Pillars of Creation," are made with this set of filters, since it's a useful set for scientists to see what's actually happening), which shows SII emissions as red, Ha emissions as green, and OIII emissions as blue. Because Ha emissions so dominate this nebula, I have significantly de-emphasized them in this rendering (but not as much as in the next photo in the stack, so there still is a greenish hue to the image). The OIII emissions on this object are very much in the same place as the Ha emissions, resulting in a lot of blue-green areas; the SII emissions in this nebula are often in the same place as the Ha emissions, which produces the yellowish color. Bright stars tend to be magenta in color with this palette; some people substitute "normal" colored stars, but I just leave them that way, since all the colors are false anyway. This form of combining results in magenta-colored stars, which I have significantly desaturated.

(iii) A version in a revised Hubble palette (the fourth photo in the stack, labeled "SHOtan" in the bottom left); a lot of the Hubble photos, including and especially the famous "Pillars of Creation," are made with this set of filters, since it's a useful set for scientists to see what's actually happening), which shows SII emissions as red, Ha emissions as green, and OIII emissions as blue. Because Ha emissions so dominate this nebula, I have very-significantly de-emphasized them in this rendering. The SII emissions in this nebula are very much in the same place as the Ha emissions, which explains the yellowish color. I like the clear blue when a nebula has significant oxygen emissions, as is the case here. This form of combining results in magenta-colored stars, which I have significantly desaturated.

(v) A version which is a mix of a grayscale Ha image and a grayscale SII image; unusually, the SII showed more structure in places then the Ha did, so I wanted to get some of that.

These are five of the most frequent ways images of emission nebulae are likely to be presented, so I thought it would be fun to include all of them, to be able to compare and contrast the different presentations.

Technical Information:

Ha:OIII:SII:L:R:G:B: 810:690:600:540:180:180:300 (a total of 55 hours of light-frame exposure time); here's a chart showing the various subexposures I used in the image:

Hydrogen Alpha: 27 thirty-minute
Oxygen III: 23 thirty-minute
Sulfur II: 20 thirty-minute
Luminance: 32 fifteen-minute, and 20 three-minute
Red: 12 fifteen-minute
Green: 12 fifteen-minute
Blue: 15 twenty-minute

The luminance layer is a mix of the luminance-filtered images, the Ha-filtered images and the SII-filtered images; the red channel is a mix of the red-filtered images and the Ha-filtered images; the green channel is a mix of the green-filtered images and the OIII-filtered images; the blue channel is a mix of the blue-filtered images and the OIII-filtered images. The SHO versions also use the SII data.

Equipment: RC Optical Systems 14.5 inch Ritchey-Chrétien carbon fiber truss telescope, with ion-milled optics and RCOS field flattener, at about f/9, and an SBIG STX-16803 camera with internal filter wheel (SBIG filter set), guided by an SBIG STX guider, all riding on a Bisque Paramount ME German Equatorial Mount.

Image Acquisition/Camera Control: Maxim DL, controlled with ACP Expert/Scheduler, working in concert with TheSky X.

Processing: All images calibrated (darks, bias and sky flats), aligned, combined and cropped in Pixinsight. Color combine in Pixinsight. Some finish work (background neutralization, color calibration, noise reduction with NoiseXTerminator; deconvolution using BlurXterminator, HDR combine of the luminance data) done in Pixinsight; some cleanup finish work was done in Photoshop CC.

Location: Data acquired remotely from Sierra Remote Observatories, Auberry, California, USA.

Date: Images taken on many nights in November and Decsmber of 2025. Image posted May 11, 2026.

Date: Image scale of full-resolution image: 0.56 arcseconds per pixel.

Seeing: Mediocre to poor

CCD Chip temperature: -25C

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