NGC6976

Hickson 88 consists of only 4 galaxies at a distance of about 260 million light-years. All four are spirals with three nearly face on. All are of unusually low contrast making details rather indistinct. It didn't help that there was a weak aurora this night and even though it the field is low in the southern sky it was still a 6 times brighter sky than I normally have. From left to right (top to bottom) they are NGC 6978, NGC 6977, NGC 6976 and 2MFGC 15807. The latter being a flat galaxy per the 2 micron survey rules. That gave me two reasons to image this group, its a Hickson Compact Group and there's a flat galaxy in the image. This group is in northwestern Aquarius.

NGC 6976 is classed as SAB(r)bc? with HII emission by NED while the NGC Project says Sbc in its simpler system. It has a dual entry in the NGC catalog also listed as NGC 6975. It was "discovered" twice. First by Albert Marth in 1864 then by Guillaume Bigourdan in 1886 who later realized he made a positional error and was off by 180 degrees. Both "findings" made it into the NGC catalog. I used the 6976 name since it came first. It is also HCG 88C using Hickson's numbering scheme.

NGC 6977 is classed as SB(r)a pec: dSy2 by NED and simply SBb by the NGC project. They don't quite agree. It was found also by Albert Marth but in 1863. How he missed 6976 at that time I don't know. It is HCG 88B by Hickson's labeling.

NGC 6978 is classed as Sb AGN by the NED and Sb without mention of the AGN by the NGC Project. Like 6977 it was discovered by Albert Marth in 1863 and is HCG 88A

The fourth member of HCG 88 is HCG 88D or more commonly MCG -01-53-14 and is classed simply as S? by NED. It's the only one of the 4 that doesn't seem disturbed. The three NGC galaxies all show signs of being stirred up by interaction with each other.

The field has set a record for me for quasar candidates with 16 of them in the field and several more just outside it. None, however, have been confirmed spectroscopically, at least as far as I can tell from their NED listings. All are based on photographic red-shift measurements. In a few cases, the Sloan survey says they are only stars. Arp always considered quasars as nearby objects with their redshift being due to other factors than distance. He considered them as being emitted by active galaxies. He loved to point out active galaxies with lots of quasars (4 or 5 was "a lot") as proof of his ideas. He tended to ignore active galaxies without them saying they just hadn't emitted them yet. Everyone else sees this as just random distribution. I wonder if he knew of this field? Seems to be just what he'd want. Three active galaxies with 5+ quasars apiece. Now that he is gone maybe his idea will finally fade away as well. It might have seemed somewhat plausible 40+ years ago but not today. A couple of the quasar candidates are so close to other stars you will need to double or triple the size of the image (unless your monitor has unusually large pixels) to separate them from the star. A line has been drawn to the quasar candidate in these cases. UvES stands for Ultraviolet Excess Source for those new to my annotations. Such objects, when starlike usually prove to be quasars.

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

Related Designations for NGC6976

NGC6985

NGC 6985 and NGC 6985A are a pair of peculiar galaxies in southwestern Aquarius 2.5 degrees northwest of M72. It is a quarter of a billion light-years distant. While the pair are at about the same redshift I can't find anything on whether they are interacting or not. NGC 6985 is classified as SB:(s)a: pec. The colons are about the same as question marks in that they note there's some debate about it being a barred spiral and it being a class a spiral which refers to how tightly the arms are wrapped. It is also a very red spiral. Its companion is shown as IB(s)m: pec. Considering most irregular galaxies are strange I don't know what it takes to make one peculiar. In any case, they do make a strange pair. It was discovered by Francis Leavenworth on June 11, 1886.

The rest of the field has nothing with redshift data and very few of its galaxies even listed in NED. All that are shown in the annotated image. Normally I'd not annotate an image with so little in it but it has four asteroids, 3 of which are very faint. They show how poor the night was. Note the trail of the brightest just northeast of NGC 6985. At magnitude 17.8 it should be much brighter with the color images strong enough to color the background but it is very faint with a somewhat broken trail of varying brightness due to the constantly changing transparency this night. Makes me wonder how much of these galaxies, especially NGC 6985A was lost to the poor skies.

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

Related Designations for NGC6985

NGC6991

IC 5076 is a reflection nebula seen against a large open cluster known as NGC 6991. The problem is there are two clusters with the NGC 6991 designation. Both are in my image. William Herschel described the cluster as the one in the center around which is the reflection nebula IC 5076 which is illuminated by the 6th magnitude star. I can't determine if that star is related to the cluster or not. John Herschel, William's son described a cluster seen to the lower right of the nebula. Yet others consider NGC 6991 to not only be both clusters but a much larger region of bright stars centered up and to the right of the nebula. WEBDA agrees to the latter while Seligman says it is the cluster just to the southwest of the nebula. And you thought astronomy was an exact science. In any case, my target is the reflection nebula. That object's location isn't up for debate. The nebula was not noted by either Herschel. I've seen no common name for this nebula. I could find only a very few images of it on the net. It is located in Cygnus, a constellation that is full of emission nebula but only a very few reflection nebulae.

IC 5076 was discovered by Isaac Roberts on September 13, 1895. He was an English astronomer working at his private observatory with a 20" reflector. He used photography to find 35 IC objects, 34 of which were new.

The discovery of NGC 6991 is not known very well. If you mean the cluster to the southwest of the nebula then it was found by William Herschel on September 27, 1788. If you mean the cluster around the nebula it thought John Herschel was the discoverer but no date is known. It was much later that the entire area (larger than my image) was first considered as the cluster. WEBDA sees it as about 45 minutes in Right Ascension and in declination. They claim it is about 2,300 light-years distant and 1.3 billion years old. They give a reddening value of zero which likely means undetermined.

This is a reprocess of a 2008 image starting from the TIFF file rather than raw data as that wasn't easily available being on a drive in a fire safe in the basement and at a bank's safe deposit box. Getting to the safe is difficult as it is in a compartment under the stairs where my back doesn't like to go.

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

Related Designations for NGC6991

NGC6992

The Cygnus Loop is a huge bubble of gas blown by a supernova some 15,000 years ago about 2600 light-years from us according to the HST website. APOD says 7500 years ago and 1400 light years distant. Other sources give other figures but the ratio stays rather constant. In other words, this one is still rather unknown as to distance and time though the trend is making it smaller and nearer. It was said to be over 100,000 years old when I first learned of it nearly 60 years ago! Various parts of it go by various common names. Veil, Witches Broom, Pickering's Triangle and others. It also has several NGC and IC numbers. You need a system with over a three degree field of view to see the entire bubble, 6 times the size of the full moon. Like most bubbles, it is the edges that are the easiest to see as the gas there is thicker from our perspective. The portion in my frame is of the northeastern edge of the bubble known as NGC 6992. My field is way too small for even that so I have just part of it. I'd need at least four such images to cover all of NGC 6992. That was my intent last summer but weather prevented it from happening. It took several nights just to get this one part.

What you are seeing is not pieces of the super nova's star. It blew in a rather "dense" region of the galaxy's disk. The explosion's shock wave hits this gas and causes it to glow much like ultraviolet light from a bright star can cause gases to glow. In this case, the energy comes from the shockwave, not light. It compresses and heats the gas it is going through creating a bubble of light we see as the Cygnus Loop. Hydrogen atoms glow with a very red color (a little blue as well but it is weak compared to the red) while oxygen glows with a cyan color somewhat between green and blue. The heat energy needed to excite the cyan OIII radiation is a bit different from that needed to create the red of H alpha and H beta. It is this difference in energy that is mostly responsible for seeing the red of hydrogen in one area and the cyan of oxygen in another rather than the elements being segregated in space. Notice that all around the loop it is the very front of the shock wave that has the most cyan from OIII with the Hydrogen mostly appearing a bit back from the shock front. This effect is seen completely around the edges of the loop. In the center where we aren't looking at the edge, such as Pickering's Triangle the colors pretty well mixed since we don't see that portion edge on.

Most images of this object are seen in narrowband images to better separate the elements in the shock front. I didn't begin to have the clear sky time needed for this so went with my normal LRGB image format. Still, the elemental separation is quite obvious. This part of the nebula was found by William Herschel on September 6, 1784. It is in the second H400 program.

As far as I can determine no one has found any remnant of the star that is causing this.

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

Related Designations for NGC6992

NGC6995

The Cygnus Loop consists of many separate NGC, IC and other designations, some with common names as well. NGC 6995 is the portion in this image with the start of IC 1340 at the bottom. The Cygnus Loop is about 3 degrees across. While sometimes called a supernova remnant that isn't quite correct. It is caused by the shock wave of a supernova that happened some 5,000 to 8000 years ago (old estimates say up to 100,000 years ago). It seems to get younger with every new study. The distance is rather uncertain but a measurement by FUSE puts it about 1470 light-years away. If correct that means the 3 degree bubble is over 76 light-years across. Obviously, the debris of the supernova couldn't be seen spread over this vast area. In fact, no debris or other sign of the supernova is to be seen other than the shock wave itself. That is compressing interstellar gas ahead of it. The energy from the shock wave causes it to glow with the Hydrogen showing as mostly red and the OIII being rather blue (I'd have expected more cyan but it came out blue for me so something else is also involved I'd think, H beta probably). Its diameter of a bit over 76 light-years gives an average speed of 1.5% the speed of light or about 2800 miles per second or 10 million miles per hour! You might expect that motion to be visible. Remember the material isn't moving with the shock wave. It is just the compressed gasses excited by the shock wave as it passes through them. Instead, new shock features will become visible as old ones are left behind. That will take time though by comparing very old images some features on the outside of the bubble might be expected to brighten and hints of new ones develop as those toward the center dim and fade away. Comparing an image I made (very poor) in 2006 to one made last year I found no obvious change though the exposure times and acquisition techniques were so different real brightness changes are hidden.

Note the distant faint, apparently dust reddened galaxies on the left side of the image, especially toward the bottom. Oddly they aren't seen on the right side in the middle of the loop though some are on the western side of the loop. None had redshift data and many weren't listed at all in NED which has only picked up those with strong 2 micron emission to make the 2MASS catalog. The biggest and brightest (near an orange star) isn't listed at all. Thus I didn't bother making an annotated image.

I had hoped to work on a large mosaic of the east side of the bubble. But thanks to the highly variable weather that didn't happen. I did get lucky for a couple hours of far better than usual (for this year) conditions which allowed me to capture this part of the eastern loop. At this rate, I should finish the mosaic by 2020! As usual, this is a pure LRGB image, no narrowband data was used and I only had good skies for my usual short 40 minutes of luminance and 60 minutes of color data. Far less what most would use for this object. Still, it is one of my best images for 2013.

The NGC part of the nebula was found by John Herschel on September 7, 1835. The IC 1340 portion was seen by Truman Safford on September 13, 1866.

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

Related Designations for NGC6995

NGC6997

NGC 6997 is an open cluster inside the famous North American Nebula near the "Ohio and West Virginia border" as Sue French put it. I see it closer to the "East Coast". Its Trumpler Classification ( http://www.astrophoton.com/trumpler_class.htm ) is III2P. That means it can be separated from background stars even though it has no noticeable concentration, has a moderate range of star brightness but has less than 50 stars. WEBDA puts it at a distance of about 2000 light-years with an age of 100 million years. Others have a different distance with 2500 light-years the most recent I found. I doubt it is connected with the North American Nebula, just that they are in the same line of sight from our location. Most put the nebula further away than the cluster making it a foreground object. But with the uncertainties involved, I'm just playing the odds here.

The cluster was discovered by William Herschel on October 24, 1786 and is in the second Herschel 400 Observing Program. My notes from that got lost in my move to Minnesota but I see I mentioned it in my first Herschel 400 notes on NGC 7000, the North American Nebula which he is also credited with finding the same night. My notes from that include "NGC 6997 was prominent on the East Coast". I used both my 6" f/4 at 24x and my 10" f/5 at 65x. Which generated the comment I didn't say.

Nearly all images of the North American Nebula use an H alpha filter which makes it quite red. I was rather surprised to see it has both blue and red regions with blue rather bright. This had me rechecking my color calibration but it appears correct.

It had been so many years since I put this one on the to-do list I'd forgotten its connection to the North American Nebula. The raw FITS files showed only a hint of nebulosity so when I stacked them, at first I thought I did something wrong, the nebula was so bright.

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

Related Designations for NGC6997

NGC7006

NGC 7006 is the other globular in Delphinus is much more distant, being far beyond the normally considered radius of the galaxy's halo. It is thought to be about 125 thousand light years from the galaxy's core and over 135 thousand light years from us. Still, it is a surprisingly bright object, easily seen in a 6" scope. But at its great distance, I've never seen even a hint of resolution of any of its stars in my 10" scope. It is just a ball of light visually. Again, like NGC 6934 I imaged this one at 0.5" per pixel, but on a slightly better night. It was discovered by William Herschel on August 21, 1784. It is in the original H400 program. My log from June 14, 1985 on a fair but humid night with my 10" f/5 at up to 180x reads; "Small blobular cluster, rapidly brighter toward the core. No hint of resolution. Seems brighter than the H400 writer indicates. I've seen it easily in my 6" f/12."

It is the distant spiral galaxies that make this shot interesting. Surprisingly, to me anyway, several bright ones are not cataloged by any catalog I can find. MGC+03-53-011 is the spiral west (right) of the globular and is about 340 million light years distant. MGC+03-53-010 is the vertical spiral at the very bottom of the page and is a tad over 500 million light years away. Unfortunately, I didn't realize its full extent and left some of it out of frame. Above it and slightly to the right, just above an arc of stars is another spiral AGC 300174 and it like MGC+03-53-011 is about 340 million light-years away. They are likely members of the same group. Near the lower left corner is the rather bright elliptical galaxy MGC+03-53-012. Like MGC+03-53-10 it is just over 500 million light years away. So those two are also likely related. Another spiral, again partly cut off at the bottom of the image is 2MASX J21012393+1605343 ID. I can find no data on it. The rest of the galaxies are in no catalog I have access too.

At the top of the image just left of center is a blue star. Below it is a curving arc of fainter stars. The first one is about the same shade of blue as the first star, just fainter. Actually, it isn't a star at all. It is another quasar, QSO B2059+1604 and is listed by NED as being 10.221 billion light years away. It is blue, contrary to the oddly red one in my last post that was also at about the same distance.

14" LX200R @ f/10, L=4x10' binned 1x1, RGB=2x10' binned 2x2, STL-11000XM, Paramount ME

Related Designations for NGC7006

NGC7008

NGC 7008 is a fascinating planetary nebula in Cygnus. It was discovered by William Herschel on October 14, 1787. It is in the original H400 program. My log entry for that dated June 14, 1985 using my 10" f/5 at up to 180x on a fair but humid night reads; "Large, round, planetary nebula. North edge is much brighter. Apparent 13th magnitude star seen at center. Hard to view due to the bright double star on the east edge." That gave me fits in processing this image as well.

Last year I had some, for me, great seeing and got 9 20 minute luminosity frames of NGC 7008 binned 1x1 for 0.5" pixels. But the color data was weak and under less than average seeing. I'd planned on getting more color this year but the weather and seeing had other ideas. Seeing, what few clear nights we had was just not sufficient even for color to go with the luminosity data. Using the weak color data gave a washed out color image. Upping the saturation just made it plain ugly and blotchy. I tried all the tricks I'd heard of to help saturation but nothing worked very well.

A couple days ago I came upon a presentation Adam Block made at the AIC conference a couple years ago. It included a single slide saying use Lab color and adjust the a and b layers via contrast to up saturation in these cases. A adjusts mostly the red-green side while b the blue-green. So I gave it a try and it does work very well. Not like good color data in the first place but sure did improve my image. I'm still looking to get more color data but wanted to get this method out as it worked, on this image at least, far better than the other ways I'd learned. It also preserved more sharpness in the overall image. Before I had used some light unsharp masking to get back the detail lost when the fuzzy color was added. None was needed using this method. In fact, there's nothing but a stretch applied to the luminosity data but for a slight amount of background smoothing but even that was very light. I doubt many would see the difference.

Edit: I now do nearly all my color processing in Lab color rather than RGB. Most of the older images however still use RGB. I don't have time to go back and process hundreds of these older images.

14" LX200R @ f/10, L=9x20'x1 RGB=2x10', STL-11000XM, Paramount ME

Related Designations for NGC7008

NGC7013

NGC 7013 is a rather nice spiral galaxy that is often overlooked since it hides in plain sight but in a constellation not known for galaxies -- Cygnus the Swan. It is less than 2 degrees from the southeast edge of the Veil Nebula complex in fact. This means it is rather heavily obscured and its color balance severely altered. It is much redder in my image than it really is. 60% brighter in red light than green and 60% dimmer in blue light than green light. Twice as much of its blue light is blocked than its red light giving it a rather red color. The arms are likely far bluer than they appear in my image. The extinction appears to vary quite a bit across the galaxy. At least my attempts to correct for this extinction resulted in a very uneven color effect. I could have forced the colors but decided to just go with what hit the sensor as adjusted for its known light curves. Most of the stars in the image are in front of the absorbing dust so are mostly correct.

Redshift puts the galaxy only about 22 million light-years distant. The only Tully measurement of its distance puts it at 46 million light-years. I suspect this is closer to correct but its error bar is rather large.

NED and the NGC Project classes it as SA(r)0/a and notes its a LINER galaxy. The (r) refers to the apparent ring that forms its brightest region around the core. Outside the ring, the arms are faint, diffuse and mostly featureless. While I show a rather interesting color pattern to this outer disk I suspect that is due to differences in dust absorption by our galaxy rather than real. Note I said apparent ring. While no official Hubble image exists of this galaxy they did take a very few (2) mono images with WFPC2. It shows the ring is mostly due to poor resolution from ground based telescopes of the extensive dust structure of the galaxy and is not real at all.

There is a nebula at the top of the image which is in the general direction of the Veil complex. I can't find it listed in SIMBAD. As the data came in I figured it was H alpha from some far-flung piece of the Veil or maybe of the large HII complex of central Cygnus not far away. But its color suggests it is dim dust and thus possibly galactic cirrus illuminated by the light of our galaxy rather than some individual star as is the case with most reflection nebula. If anyone knows more please let me know. Searching the net I've found a couple others noting the nebula but also unable to pin it down.

While NED lists a handful of strong IR emitting background galaxies none have any distance data and are mostly very faint I didn't prepare an annotated image.

In processing this image the quite red (b-v=2.28!) star at the north end of the galaxy was a pain to deal with. I failed rather miserably to do so. While the HST image was framed to omit the star its glare is severe in their images as well so I don't feel quite so bad failing to deal with it like I wanted to.

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

Related Designations for NGC7013

NGC7023

NGC 7023 is a reflection nebula about 1300 light years from us. If the distance is correct then the nebula is some 6 light-years across. It has a few hints of emission pink in it. Like all my images of late it is bothered by moonlight so doesn't go as deep or show as strong color as I'd like. Being in Cepheus it is too far west until next winter. To help with the moonlight I used 110 minutes of luminosity data but only 20 in each color. That's not enough to pick up subtle color hues of the fainter HII regions in this nebula. The nebula was discovered by William Herschel on October 18, 1794. It is in the second edition of the Herschel 400 Observing Program. My log of that vanished in the move up to Minnesota from Nebraska. The illuminating star is HD 200775 a Be (emission line) star. It has been contracting some 100,000 to become a main sequence star and is thought to have 5 to 15 times the sun's mass. Once it reaches the main sequence it will likely live about 100 million years. If at the higher mass then it would live a shorter life which could end in a supernova.

14" LX200R @ f/10, L=11x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Related Designations for NGC7023