On this page a 25°×35° wide-field view of Milky Way in the constellations Taurus, Auriga and Perseus is presented in different color composites.
The region south of the galactic plane is full of Molecular clouds.
Some (probably not all) of these unexplored nebulae have been collected in the list below. Click on the following links for a presentation.
Objects that are not cataloged by now and objects the are related to them (the list does not contain objects that are only minor extensions of known structures):
Uncataloged HII rings and arcs. Some of these structures may be random, some may be projections of spherical shells (bubbles).
Such structures are always circular in the image because stereographic projection was used.
The outlines of these structures are completed to circles.
It may be helpful to toggle these plots on a off by pressing the '2' key in order to improve the visibility.
Huge HII region, labeled CA1,
that lies behind Molecular clouds in Taurus and Perseus because it is only visible in the voids and less dense regions of these molecular clouds.
The brightest part is the California nebula (NGC 1499). Since the whole region has a similar filamentary structure, it seems to belong together. The apparent diameter is at least 24° (the width of the field of view).
There are two other HII regions that seem to lie in front of CA1, labeled "LBN 749A" and "LBN 749B" here. They are at a similar position as LBN 749 (coordinates of LBN catalog are often inaccurate), which is categorized as a HII region, and together they have similar dimension as LBN 749.
The brighter part, here labeled LBN 749A is most likely ionized by HD 278942 at a distance of about 383pc (=1250ly, Gaia EDR3, +/-14pc).
That nebula is partly obscured by molecular clouds: some dark nebulae lie in front, the molecular clouds that obscure CA1 lies in background.
The foreground nebula is the Perseus molecular at a distance of about 305pc, see . At this distance the diameter of LBN 749A is about 30pc (6° apparent), which means that it is almost impossible that this nebula lies within the Perseus molecular cloud.
Thus, the background nebula must belong to another Molecular cloud which has a minimum distance of about 380pc. The existence of two molecular cloud in that region is consistent to , a CO radio survey which observed double lines in that region. That survey also measured the northern parts of the molecular cloud that obscure CA1.
The fainter part of LBN 749, LBN 749B, is most likely ionized by omi Per. Most exact distance estimations are from Gaia EDR3: 290pc to 380pc. That does not lead to additional information. Also, it is not clear whether
IC 348, the nebula south of omi Per and whose distance is about 320 pc (long baseline measurements from  and Gaia EDR3 data) lies in front of LBN 749B or not.
Near VdB 24 there are two young stellar objects that may belong to the molecular cloud that lies between CA1 and LBN 749A, BD+38 811 and 2MASS J03494092+3859051, both in a distance of about 430 pc (=1400ly).
Unfortunately it cannot be safely detected from visual inspection, whether the large HII region lies in front of that star formation region.
Furthermore the Taurus Molecular Cloud obviously lies in front of CA1. Distance according to  is 130pc to 200pc, much closer than LBN 749A.
Thus, the only constraint that can derived from the given data is that the minimum distance of the molecular clouds that lies in front of CA1 (and behind LBN 749A) is about 380pc.
The brightest part CA1, NGC 1499 or the California nebula, is assumed to be ionized by Xi Persei. Distance estimations are 370pc to 460pc (Gaia EDR3) and 320pc to 470pc (Hipparcos).
At least the farther end of the confidence interval would be consistent with the lower constraint of 380 pc. But is is not likely that that star ionizes the whole region CA1 because it lies close to the boundary.
A alternative ionization candidate for CA1 is the high-mass X-ray binary X Persei, which lies almost in center of CA1. Its distance according to Gaia EDR3 is 600pc to 630pc.
At this distance the diameter of CA1 would be about 260 pc (apparent diameter 24°). It is therefore possible that both stars ionize parts of a larger HI region (similar filamentary structure) where the northern
structure of the ionized part (containing NGC 1499) is closer than the rest of the HII region.
False color images containing H-alpha and continuum:
H-alpha is mapped to red, blue continuum is mapped to green and red continuum (without H-alpha) is mapped to blue.
Color of molecular clouds and reflection nebulae in the false color image is something between green (bluish in reality) and blue (reddish in reality).
HII regions (ionized hydrogen) appear red to orange, depending on the amount of OIII (doubly ionized oxygen) which is detected by the blue continuum filter.
HII regions can be obscured (i.e. their radiation is scattered and/or absorbed) by Molecular clouds that lie in front of them. But Emission nebulae do not obscure Molecular clouds.
That means, a HII region lies farther away if it seems to hidden by a visible molecular cloud or a dark nebula. If molecular clouds and HII regions look somehow mixed, the HII region is either nearer or the molecular cloud is very thin.
The latter aspect is the reason why it is difficult to determine whether a HII region that is not obscured lies in front of the molecular cloud.
An improved visualization of the correlation between HII regions and molecular clouds is planned as soon better data are available, namely NIR data which better indicate regions that are optically thick for H-alpha emission.
A repository with the discoveries can be found at GitHub
Images where captured with a camera array which is described on the instruments page.
Image data are:
RA: 4h36', DEC: 32°
North right (exactly)
10 arcsec/pixel (in center at maximum resolution)
35°×25° (RA×DEC, through center)
Sum of exposure times of all frames used to calculate the image.
All image processing steps are deterministic, i.e. there was no manual retouching or any other kind of non-reproducible adjustment. The software which was used can be downloaded here.
Image processing steps where:
Bias correction, dark current subtraction, flatfield correction
Alignment and brightness calibration using stars from reference image
Stacking with masking unlikely values and background correction
Denoising and deconvolution both components (stars and residual)
RGB-composition (same factor for stars and residual for the true color composite)
Dynamic range compression using non-linear high-pass filter