NGC6824

NGC 6824 is an SA(s)b: galaxy in northern Cygnus. Redshift puts it about 150 million light-years away. Tully-Fisher estimates run from 120 to 180 million light-years which brackets the redshift distance nicely. Most sources give a size of 1.7 by 1.2 minutes of arc. I find that way too small. I measure it at more like 2.9 by 1.9 minutes of arc. Apparently, they are measuring only the inner bright region. Assuming the 2.9 minute figure I get and the redshift distance it is about 125,000 light-years across, a bit larger than our galaxy.

The galaxy was discovered by William Herschel on September 16, 1792. It is on the Herschel 400 II observing list. That is what put it on my to-do list. Cygnus isn't a constellation I normally think of as a place to look for galaxies. Its location in the zone of avoidance means the field is little studied. It is the only galaxy in the image with redshift data. With so little data on the field no annotated image was prepared.

Seeing was very poor the night this was taken but transparency was much greater than usual. This allowed me to get its faint outer halo not often seen even if it meant giving up some detail. Maybe next year I can get an image with good detail and combine the two for both. It seems if transparency is great seeing isn't and vice versa. The uncertainty principle of imaging. This night a cold front cleared out the smoke that had been a pain for so long but left mixing air temperatures ruining seeing.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for NGC6824

NGC6826

NGC 6826 is apparently the only known triple shell, giant halo planetary. Considering there are only 3 in the first category and 6 in the second that isn't all that surprising. It is in northwestern Cygnus. Distances to planetary nebulae are very hard to determine. One paper cited two other papers giving a range from 2450 to 7385 light-years. It was discovered by William Herschel on September 6, 1793. It is in the second H400 program.

It is also known as the Blinking (Eye) Planetary Nebula. When you look right at the central star the nebula fades greatly only to reappear when you look off to the side. I have seen lots of observers blame this on the lack of sensitivity of the eye's fovea. It's been long known to visual observers that the center of our vision has fewer low-level rod cells so doesn't see faint objects all that well. This is involved but other equally faint planetary nebulae don't exhibit this trait nearly so strongly. Those though don't have 10.4 magnitude central stars. Theirs are several magnitudes fainter. I used a crosshair eyepiece to block the light of the central star. When that was done even looking at where it was the nebula only faded slightly. I think most of the "blink" is due to how our eye/brain handles the fainter nebula around the bright star. Something to test at your next dark sky star party.

You can read a bit more on it at: http://adsabs.harvard.edu/full/1981PASP...93..719F

The other unusual characteristic of this one (not mentioned in the above link) is the FLIERS (Fast Low-Ionization Emission Regions) seen in it. They are the two red regions seen in the HST image (link below). In my RGB image, they come out as bright blue regions on either side of the center shell (mostly hidden by the bright central star). Why they came out blue I don't understand but they did. These FLIERS may not be so "fast" however. There's some indication they are relatively stationary and somehow the gas of the second shell is speeding past them rather than pulling them along with the shell's expansion. Either way FLIERs are hard to explain with our current understanding of Planetary Nebulae.

The only galaxy with a redshift measurement in the image is the brightest in the field. It is west (right) of NGC 6826 and a bit north. It is CGCG 257-010 with a redshift that puts it some 330 million light-years away. All others in the field that NED includes are from the 2MASS survey, as is CGCG 257-010.

Due to the huge brightness difference between the central part of the nebula and the large halo I used two sets of exposures to record this one. The core was exposed using 14 2 minute exposures for the luminance and 2 5 minute exposures for the color data. The rest of the image used my "standard" 4 ten minute luminance and 2 10 minute color frames. The two were then blended together. As usual, all were binned 2x2. I really need a better night for the core. If it happens I'll redo the core region using 1x1 binning.

Hubble's image of the inner two shells using narrowband filters:
http://hubblesite.org/newscenter/archive/releases/1997/38/image/d/

14" LX200R @ f/10, L=4x10' and 14x2' RGB=2x10' and 2x5', STL-11000XM, Paramount ME

Related Designations for NGC6826

NGC6827

NGC 6827/Berkeley 048 is an open cluster in Vulpecula about 5.5 degrees east of the far more famous Coathanger asterism. It is also known as Berkeley 48. It is classified as a type I3m cluster. It was discovered by Édouard Stephan on October 16, 1878. WEBDA puts its distance at 13,000 light-years. Reddening dust can be seen across most of the image, especially to the upper right. Areas rather dust free can be seen to the lower left though even there reddening dust crosses part of the image. The lack of stars to the upper left is likely due to dust obscuring them rather than a real lack of stars in that part of the galaxy as that is toward the plane of the galaxy. WEBDA says the dust results in a full magnitude of reddening for the cluster which explains some of the redder than normal stars that appear to populate the cluster. WEBDA puts its age at about 800 million years which also means its bluest stars have long since died leaving a cluster that is somewhat reddened by age alone. A quick search of Google and AstroBin turned up no color images of this cluster.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for NGC6827

NGC6829

NGC 6829 and NGC 6831 are a pair of possible interacting galaxies in Draco. Though the lower left corner of the image lies in Cygnus. NGC 6829 is listed as an Sb galaxy by NED and the NGC Project. Seligman says Sb?. Redshift puts it at 144 million light-years. The CGPG says of it: "Red 'sandwich' galaxy, heavy absorption line, twisted tips, internal compact knots." To me the entire southern part of the galaxy is weirdly distorted showing two dust lanes rather than just the "sandwich" lane. It is surrounded by a large halo that extends further to the southwest than the northeast. I measure its size at 95,000 light-years.

NGC 6831 is a truly strange beast. It is classified by NED and the NGC Project as S0 while Seligman says S0?. What very few images of it I find show only the core which indeed looks to be an S0 galaxy but my exposure picked up an outer region that paints quite a different picture. It has an odd blue loop that as it comes across the galaxy it appears to change into a red dust band. But a closer look shows these to be two separate features with one ending near where the other starts. Still, such features are normally seen in S0 galaxies. Are they evidence of a polar ring? Are these features due to interaction with NGC 6829? I found nothing on either of these galaxies. NED's redshift puts it 151 million light-years distant which makes it 83,000 light-years across its long axis. Though if this is a true oval galaxy with an unknown orientation its true size may be larger.

Both of these galaxies were discovered by Lewis Swift on September 3, 1886.

Actually, these are two of a trio of galaxies. I was so taken with how odd NC 6831 was I totally missed this. The third galaxy is UGC 11475. It is out of the field to the south though its very northern outskirts show as a blue glow on the very bottom edge of my image a bit right of NGC 6829. It is listed as SBd at NED with a redshift placing it at a distance of 142 million light-years. The trio is known as UZC-CG 268. If my brain had been in gear I could have included it in the image. I don't know how I missed this.

This field is within the Zone of Avoidance which is little studied for galaxies. As a result, these are the only ones with redshift data. With so little to annotate, I didn't prepare one. This is my first image finished in October. I'm only 3.5 months behind and with December and so far January a dud that's more like 2 months behind. I may get caught up if this horrid weather continues.

14" LX200R @ f/10, L=4x10', RGB=2x10' STL-11000XM, Paramount ME.

Related Designations for NGC6829

NGC6835

NGC 6836 is a rather odd spiral galaxy in northeastern Sagittarius. It's a rather featureless low surface brightness galaxy with a few scattered blue star clusters. Any hint of arms in the featureless disk is so faint I can't really see any. The RC1 (Reference Catalogue of Bright Galaxies -- 1964) Describes it: "Bright middle, no bright nucleus. Very faint spiral arms or arcs. Very poorly resolved. Low surface brightness. Non-interacting pair with NGC 6835 at 7.5 arcmin." I find the "...no bright nucleus" part hard to understand as my image shows a tiny but bright nucleus. It is classified as SABm with a redshift distance of 65 million light-years. At that distance, it would be about 29,000 light-years in diameter so a near dwarf. Unfortunately, that's about all I was able to find on it. Thanks to the odd gap in its disk filled by three bright field stars in our galaxy it looks like a glutinous Pac-Man that is eating three pellets at a time.

It's companion to the northwest is NGC 6835. It appears to be an edge on spiral. The 1994 Carnegie Atlas of Galaxies Vol. 1 says of it: "The classification of NGC 6835 is uncertain. From the asymmetry in the pattern seen in the short-exposure image at the top right, one guesses the presence of spiral structure ... No resolution into components of the stellar content is seen ... the Amorphous? classification is suggested." NED classifies it as SB(s)a? with some spectral lines. Its redshift is similar to that of NGC 6836 putting it 64 million light-years from us. This indicates they are likely true companions. It's much larger angular size gives it a diameter of 45,000 light-years, rather typical of many spirals.

Both NGC galaxies were discovered by Édouard Stephan on the night of August 2, 1881.

Sloan indicates about 0.54 magnitude loss in green light and 0.4 magnitudes in red. Another source puts blue's loss at 0.62 magnitudes. I applied these adjustments to the two galaxies. Stars and other galaxies were adjusted to G2V standards. Usually, I don't adjust galaxies separately but without this NGC 6836 was mostly white and NGC 6835 too red. They looked more "natural" with the adjustment.

NED had redshift data for only one other galaxy in the image. It is shown on the annotated image. I'd ordinarily not prepare one for a field with so little in it but two of the three asteroids wouldn't be found without one.

Conditions for this one, as usual, were very poor. The third frame of 4 was mostly lost to conditions as shown by the gap in the asteroid trail. Seeing deteriorated and was really bad for the red frame. This results in some red halos around brighter stars as their size was nearly double the blue stars. It didn't help that this field is at my southern limit for even a very good night. But considering how poor conditions have been all year I've have little to do if I waited for good conditions.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for NGC6835

NGC6842

NGC 6842 is a planetary nebula in Vulpecula. It was discovered by Albert Marth on June 28, 1863. Determining the distance to planetary nebulae is difficult. Most posts of this one don't list a distance. I found several ranging from 4400 to 8800 light-years. The later one has an error bar of 3000 light-years. In other words, the distance is still pretty vague. Most papers on this one were behind paywalls so I was unable to learn much.

14" LX200R @ f/10 L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for NGC6842

NGC6852

NGC 6852 is a blue planetary nebula in east-central Aquila. I found distance estimates ranging from 5,100 light-years to 13,800 light-years. The most recent I found said 7,400 light-years and gave reasons why the others were wrong. http://adsabs.harvard.edu/abs/2004MNRAS.353..589P

I was surprised at how many distant galaxies were in the image being the field is on the east edge of the Milky Way and thus quite heavily obscured. Or so I thought. Seeing all these faint fuzzies makes me think it isn't nearly as obscured as I suspected. However, none of these are in the NGC, IC or PGC catalogs that I could find. NED showed no redshift data for anything in the field.

What few images of this one I found on the net all show the central star very easily. Half show a second star that's somewhat red to the northeast. Half don't show it. In some images it is nearly as bright as the central star, for most, it is fainter but still obvious. Yet in the other half, there's no sign of it. In some cases, the resolution is too low but others with sufficient resolution don't show it. I see a hint of it in the original FITS file. My resolution was poor this night but it should at least have shown as an elongation to the NE but doesn't. Could it be a variable star with a deep long minimum? Or is it just too red for my camera's weak red response? The nebula was found by Albert Marth on June 25, 1863.

14" LX200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Related Designations for NGC6852

NGC6882

NGC 6882/6885 is a star group in Vulpecula. It may be made up of several groups. WEBDA has nothing on it but a position. It is Trumpler class III2p so little to no concentration, made up of stars covering a wide brightness range and star poor. I find no distance for it or much of anything in fact. It carries two NGC numbers since it was found by William Herschel on two consecutive nights. September 9, 1784 and September 10, 1784. There's nothing of interest at the position of NGC 6882 but there is for NGC 6885. The position for 6882 lies at a bare region within 6885. To me, the cluster is made up of several groups as mentioned above and it may be Herschel saw one of these groups as 6882 but got the position wrong. He got several other objects positions wrong that night. As Dr. Corwin says "WH was clearly not up to snuff that night..." I've had too many of those nights so I'll cut William some slack here.

The first Herschel 400 lists both clusters as two separate objects. This confused me to no end it appears from my notes from May 20, 1985. I wrote of NGC 6885 as seen in my 10" f/5 scope: "Large scattered, open cluster of stars of all magnitudes. Mostly west of 20 Vulpecula (that's the bright blue star in my image). Dimmer stars seem to be centered about 4' north and more condensed than the very widely scattered brighter stars. This may account for its two numbers in both catalogs. Dim stars center is about that of 6882." My comments for 6882 written at the same time read: "See 6885 as I was unable to distinguish a second cluster anywhere in the area. 6885 is listed as 20' across and this one only 4' north so inside the other. Burnham, the Becvar catalog and Tiron make no mention of this object! Why not pick another Herschel object to replace this one -- say H-14-5 which is the bright arc of the Veil complex?" I'd forgotten all about this until I went to research this object after processing it.

I had to move the cluster low in the field. 20 Vulpeculae was sending horrid ghosts across the frame when placed higher in the field. Why moving it slightly south solved them I never did figure out. There are three rather bright stars just out of the frame to the north. They sent some nasty gradients into the frame as by moving the field south they almost came into frame. Fortunately, GradientXTerminator pretty much eliminated the problem.

As mentioned I couldn't find any distance for the cluster. Three of the brighter stars have Hipparcos data in The Sky which put them only about 120 light-years distant. 20 Vulpeculae is 10 times that at 1,140 light-years.

The weather was a problem while imaging this one. I had to sort through several nights of images to find those used here. Only one green image survived the cut as all others were lost to haze and clouds. Fortunately, the one had no satellite and I was able to make it do.

14" LX200R @ f/10, L=4x10' RB=2x10' G=1x10', STL-11000XM, Paramount ME

Related Designations for NGC6882

NGC6883

This field is in Cygnus a bit east of the neck of the swan. It is in H alpha emission that dominates along the axis of the Milky Way in this constellation. Here it is quite weak and I needed to use the H alpha filter to pick it up but the weather has been so bad that couldn't happen.

There is a lot going on in this field but unfortunately, I couldn't find much on what I show. NGC 6883 itself is confusing. Most catalogs give its location as that of the double star a bit below center in my image. To the upper right, is what appears to be another star cluster but it isn't in any catalog. Then I found catalogs that show the size of NGC 6883 sufficient to cover most of this field. WEBDA doesn't list any detail for it though does give its coordinates and a photo that includes much of my image but not the nebulae to the far left. I can't tell if they consider it an asterism or cluster. I suspect asterism but that's just a guess.

Below the double star at its usual coordinates is a dark nebula with 3 stars in it. That isn't in any catalog I checked. To the upper left is an area with two reflection nebulae and a dark nebula below the brighter reflection nebula. I did find the smaller reflection nebulae in SIMBAD. They list it as GN 20.10.7. It is centered on the apparent illuminating star. I find nothing on the bright nebula though some sources seem to consider the whole area with the name. But list it only as a reflection nebula so must not include the dark nebula. Just to the east of the star illuminating GN 2.10.7 is a smaller reflection nebula around a fainter star. It is[B77] 20. It is listed as a bright nebula so again misses the dark nebula. Some catalogs seem to include both under the GN 20.10.7 designation. The large reflection nebula isn't in any catalog I looked at. Simbad lists the illuminating star as an emission line star but otherwise is silent about the nebula. It too may be part of GN 20.10.7 though that is nearly centered on another reflection nebula sort of discounts that idea.

Due to issues with lots of clouds, especially during the red filter portion, the nebulosity barely shows and is a rather odd color. I processed for the star's color and let the faint emission nebula in the background to fall where it did. I need to do this one on a better (smokeless) night but that's not happening. Between Canadian fire smoke (limiting some nights to only seeing Vega through it) and clouds, the rest of the time that you can't tell from smoke visually though my cloud sensor can as the IR signature of clouds is very different from smoke -- which the sensor is blind to in fact. So I know both are involved as the clouds aren't thick enough to kill all stars but Vega. I'd expect the smoke to kill blue and let red through but the reverse seems true here or else in balancing star color for the smoke I killed red. The histogram for this one looks awful. I think the smoke is to blame. I need to try this another year without the horrid smoke. As I write this we are under a 4 day air quality alert due to the smoke at the highest alert level. Manitoba must have it even worse. We are also seeing a bit of smoke from British Columbia fires and the California fires.

The cluster or asterism was discovered by William Herschel on August 19, 1828. I didn't expect any of the other bright or dark nebulae when I took the image. I have no idea why I took this image. It isn't in either H400 program nor do I find it on my to-do list the computer looks to for targets. I had to have interrupted the computer and entered it manually. Was I trying to avoid the lousy weather and it was in a hole? I have no idea.

14" LX 200R @ f/10, L=4x10' RGB=2x10', STL-11000XM, Paramount ME

Rick

Related Designations for NGC6883

NGC6888

NGC 6888 is a bubble blown by a Wolf-Rayet star in Cygnus. It was discovered by William Herschel on September 15, 1792. It is in the second H400 observing program. It may be about 5000 light-years distant. Seligman has a good write-up on this one so I'll save my fingers and paste in his words.

"The Crescent Nebula is an emission nebula caused by the collision of two waves of gaseous emissions by the "bright" (7th-magnitude) star near its center, WR 136. The star is an approximately 4.5 million year old Wolf-Rayet star of perhaps 40 to 80 solar masses. Wolf-Rayet stars are very massive, extremely hot stars (originally O-type Main Sequence stars) which are near the end of their lives. A few hundred thousand years ago the star swelled up to become a red super-giant and ejected a few tenths of a solar mass of gas at about 20 thousand miles per hour. About 200 thousand years later, it heated up to several hundred thousand degrees, and began ejecting about a solar mass of super-heated gas per ten thousand years, at nearly 1% the speed of light (3 to 4 million miles per hour). As the faster moving, the hotter gas reached the slower-moving, cooler gas previously released, it created a supersonic shock wave, causing the nebula to emit visible (primarily red H‘) light, as well as ultraviolet and X-radiation. The complex filamentary structure of the nebula is real, but its spherical structure is tissue-thin in comparison to its size. Only the surface of the structure is glowing; the hot gas streaming away from the star is essentially invisible. Within a few thousand years the current nebula will fade away, as its gas disperses into the surrounding space; but within a hundred thousand years, a new and even more spectacular nebula will form when the star supernovas. WR 136 and its nebula are about 4700 light years away. Given that and the approximately 18 by 12 arcmin apparent size of the nebula, NGC 6888 is about 25 light-years across."

This was my first attempt at merging H alpha with color data back in 2007. I didn't do it right as I was working in ignorance. Nor did I take the data correctly for such a combine. This is another image I need to retake but over 10 years later that hasn't happened. Due to my errors, I'm reproducing this one at 2" per pixel rather than my normal 1" per pixel as it hides some of my errors.

14" LX200R @ f/10, Ha=3x30', RGB=3x5', STL-11000XM, Paramount ME

Related Designations for NGC6888