Jump to content

Banner.jpg.b89429c566825f6ab32bcafbada449c9.jpg

AusGuy

Members
  • Posts

    38
  • Joined

  • Last visited

Posts posted by AusGuy

  1. A couple of nights ago I tried to view Cederblad 122 which is a large bright-ish emission nebula just to the south-east of The Coalsack, the prominent dark nebula which is itself to the east of the Southern Cross. Things did not go particularly well. Despite my fairly large imaging field of view of 82 x 56 arcmin the nebula was much too large to fit into a single frame. So I resorted to wandering about the area hoping to find a region that would show up nicely as a single frame. By the time that I had moved the telescope's aim 7 times I was about to give up when, on the eighth attempt I noticed a tiny but striking blue object just within the top of the camera's frame (see image 1 below). This was unexpected. I had not seen it before. So, giving up on Cederblad 122, I concentrated on this “new” object which, because of its colour, seemed likely to be a planetary nebula.

    Cranking up the zoom level to 200% of the camera's native resolution (see image 2 below) produced a reasonable view of this strange looking object that seemed to have a definite “s” shaped central region surrounded by some arcing filaments. The following day I spent time on the internet to identify the object and it turns out that it is a well known planetary nebula having the NGC catalogue number 5189. It is located 1,780 light years away in the constellation Musca (the Fly). Its angular size is about 2 arcmin and that translates into a linear size of about 1.2 light years. To quote from NASA's HubbleSite “Most of the nebula is knotty and filamentary in its structure. As a result of the mass-loss process, the planetary nebula has been created with two nested structures, tilted with respect to each other, that expand away from the center in different directions. … Its double bipolar or quadrupolar structure could be explained by the presence of a second star orbiting the central star and influencing the pattern of mass ejection during its nebula-producing death throes.” Recent Observations with the Southern African Large Telescope have finally found a white dwarf companion in a 4.04 day orbit around the rare low-mass Wolf-Rayet type central star. There are a number of fine amateur images of NGC 5189 on Astrobin and a spectacular image on the HubbleSite can be found at

    https://hubblesite.org/contents/media/images/3870-Image?keyword=Uranus

    It just goes to show how rewarding just wandering around the sky can be. You never know what you are going to find (even if many others have long since found it before you).

    Image 1 - The "discovery" image

    Stack_4frames_240s.thumb.png.17aaa2f2787b48ba07bc7e88b3150e43.png

    Image 2 - 200% resolution

    386029122_CapturepnnearCederblad122.thumb.JPG.68ed02f14d83d6bce56706555dbc7632.JPG

    Vixen R200SS; SW AZ-EQ6 Pro; ZWO ASI294MC Pro; Baader MPCC III; Bortle 4.5

    SharpCap livestack using 1 minute exposures at 300 gain

    • Like 7
  2. Tucked away in a far northern corner of the Eta Carinae Nebula are some deep sky objects that are well worth a live image view. Here's a screenshot of the region that includes both bright red emission nebulae and a couple of star clusters. There's even a hint of some blue reflection nebula although that's better seen if you know beforehand that it's there.
    1453430307_CaptureGabriellaMistralNeb.thumb.JPG.3a6ec725e1015119a33eb086f73d46d5.JPG

    To give some context to the live image view, here's a low resolution image of the Eta Carinae Nebula with the region of the live view outlined in white.

    953456929_EtaCarinaeNebulawithGabMistframed.jpg.c20c05810ec3dd3ef555dfe08ca769ce.jpg

    And here's the stacked live view after saving and applying some minor stretching with Photoshop followed by a marked-up version of the same.

    571794286_GabriellaMistral27May2022.thumb.jpg.f337adc5b1d0b7d60ae4d650ff30486f.jpg

    512113596_GabriellaMistral27May2022labelled.thumb.jpg.a6f184a028f2fb39691cdabf69e6db9c.jpg

    Starting with the Gem Cluster NGC 3293, its most prominent stars are type B blue supergiants having apparent magnitudes of 6.5 to 6.7. But there's also a 7th magnitude pulsating red giant, V361 Carina which is noticeable by its pinky red hue even in the live view screenshot. The cluster has more than 100 stars brighter than 14th magnitude. A recent survey using deep x-ray and infrared data revealed that the cluster contains 3,600 stars most of which are below 2 solar masses making it one of the most populous clusters in the Carina Nebula Complex (CNC). Its distance is 8,000 light years. As to its age, it is 8 to 10 million years old which is quite young although it seems that it is the oldest of the large clusters in the CNC. Just above the top of the cluster you may notice a bluish tinge. Longer exposure images show that it is an obvious blue reflection nebula.

    Just to the lower left of NGC 3293 is quite a prominent dark nebula which is best seen in the Photoshopped image.

    In the lower right of the images is the red emission nebula called the Gabriela Mistral Nebula. Strictly speaking its catalogue designation is IC 2599 but it is often referred to as being NCG 3324 which is actually the designation for the star cluster embedded within it. It appears that the star cluster is creating the prominent shock wave on the right of the nebula and it is that shock wave that gives rise to the nebula's popular name. It looks very like the profile of the late Nobel Prize winning Chilean poet Gabriela Mistral.

    To the left of IC 2599 is the large curving complex of emission nebulae that forms part of the CNC. The curving shape reveals a deformed ring that surrounds the active Wolf-Rayet star WR23.

    Vixen R200SS; SW AZ-EQ6 Pro; ZWO ASI294MC Pro; Baader MPCC III; Bortle 4.5

    SharpCap livestack using 1 minute exposures at 300 gain.

    David

    • Like 4
  3. It just goes to show that one should not write in haste in the wee hours after midnight. In preparing the second post above the wrong star was marked D causing an error in the measurement. Oops.

    The better representation is given below. When I set the measuring circle's size to 10.72' it does not fully enclose the galaxy's outer arms. But enlarging it to 11.2' (11'12”) gives a much better fit although arguably just a little too small. Thus it seems that the size values given in the second source reference quoted above are the more correct. So unfortunately for the galaxy it has had to revert back to its usual size!

    1322141062_ScreenshotNGC1365Measuringrev.thumb.jpg.547325d6d1afc29f523fa93badaccdff.jpg

    David

    • Like 1
  4. Thanks for your feedback Mike and Martin. As regards size, in the original post I had initially thought to expand on the uncertainty of quoted values for angular measurement and linear size but decided against it in the interests of brevity. But since you mention the LEDA and Simbad values Martin I'll give it a go now.

    In the image attached below I've used a screen display measuring tool that I have to evaluate the EAA image. It would have been nice to have been able to use the APOD image for this purpose since it is much clearer but it is copyrighted so the EAA image will have to suffice. I have marked various stars with letters. For those marked A and B I have determined their angular separation by using the measuring tools in SkyTools3 and Cartes du Ciel. They both agree on a value of 9'54”. The measuring tool has a base (or calibration) circle which I've coloured red, placed it over the image so that it exactly spans stars A and B and set its angular value to 9'54”. The tool has a secondary measuring circle which I've coloured yellow. When I set its size value to 10.72' or even 11.2' I found that it did not fully encompass the galaxy's outer arms. So I've enlarged it so that it does. You can check this by referring to stars marked C and D and finding them on the APOD image. The resulting value for the enlarged measuring circle is 12'22”. But with an accepted distance of 60,700,000 ly that angular measurement results in a computed size for the galaxy of 218,382 ly which is significantly larger than the usually quoted 200,000 light years. Now it probably seems brave to the point of being foolhardy to challenge the linear size value quoted by so many eminent sources but that's the way the cards seem to fall. Could the measuring tool be inaccurate? Possibly, but I doubt it. It uses the simple arithmetical logic :

    Calculated measurement angle = Entered calibration angle x M/B

    where :

    M = number of screen pixels across the horizontal diameter of the measuring circle

    B = number of screen pixels across the horizontal diameter of the calibration circle

    And, as I mentioned, both SkyTools3 and Cartes du Ciel agree on the value of the calibration angle.

    988730095_ScreenshotNGC1365Measuring.thumb.jpg.4a974ee5751380fe1346bfc9a8a6846d.jpg

    David

  5. NGC 1365 has appeared a few times in the Deep Sky forum but, so far as I can determine, it has not yet made an appearance here in this EAA forum. Popularly known as The Great Barred Spiral, it is a beautiful galaxy and well worth observing but a bit of a challenge for visual observers unless they have a fairly large telescope. But for EAA it's a cinch. The image below is a screenshot from an observing session with my 8 inch Newtonian and I think that I can confidently say that it displays most of the galaxy's visual components. It's shown at 100% resolution. With my imaging system, when the camera's full frame is displayed the galaxy appears quite small although it's then possible to frame it together with some of its adjacent galaxies. The live view is not a patch on long exposure images, of course, but that's not the point. Being able to see this level of detail quite painlessly is a reward in itself. Each exposure was only 2 minutes at 400 gain but it took quite a few additions to the stack to bring out the fainter parts of the spiral arms.

    743302644_CaptureNGC13657.thumb.JPG.94206d1f40669cc52178d5bfa642fc79.JPG

    Located in the constellation Fornax, NGC 1365 is part of the Fornax Cluster of galaxies. Its distance is generally quoted as being 60 million light years (NASA, ESA, ESO) and its diameter as being 200,000 light years (but see below). There are many articles on the internet describing the nature of this galaxy and its active central black hole and they are easily found. So I won't bore you with the same details here. Rather I'll confine this to what can be seen or reasonably determined from the EAA view.

    Generally referred to as a double-barred galaxy, the fainter main bar runs pretty much horizontally across the centre in this image. I measure its angular size to be 2' 40” making it 43,550 ly long. The brighter inner core is set obliquely across it. At first sight that inner core looks to have a rounded “Z” shape but closer inspection shows that it is in fact a 21,600 ly long ovoid with obscuring dust lanes coming in from top left and bottom right. “Proper” AP images (such as https://apod.nasa.gov/apod/ap210108.html ) show that the two dust lanes are simply the left and right sides of an almost continuous dust lane that runs right across the front of the main bar. But here the overexposed core of the galaxy washes out the dust lane's middle part.

    The dust lanes themselves show some structure with wisps stretching downwards at the left and upwards at the right. They are much better seen in the APOD image and seem to relate to the ends of various spiral arms that are starting there.

    The two brightest opposing spiral arms show evidence of many star forming regions strung out along them. Our view only shows hints of the red colour of the emission nebulae that are evident in the APOD image. We can see other arms as well all following the galaxy's general spiral shape. But that brings up what seems to be an obvious question – why do the outer arms seem to curve back towards the centre of the galaxy? It seems as if the whole galaxy has been warped and the arms are being bent away from the plane of a straight-forward flattened disk. Or is it just an optical illusion? So far I have not found the answer to that conundrum. But maybe you know the answer?

    As to distance and size, most sources seem to follow each other in quoting figures of 60 mly and 200 kly respectively but these are suspiciously round and it seems probable that the actual values (as best as can be determined) are somewhat different. Is that important here? Probably not. The Fornax Cluster is located well beyond our local group and the fact that NGC 1365 still displays the size and detail that it does must mean that it is extremely large (as galaxies go). But some internet sources are annoyingly inconsistent in their description of its distance and size. For example, Wikipedia quotes a distance of 56.2 mly, a size of 205 kly and an angular size of 11.2 arc minutes. But simple trigonometry shows that at that distance 11.2' subtends only 183 kly. However, there is one source that goes into the matter is some detail. It can be found at https://ned.ipac.caltech.edu/level5/Lindblad/Lind2.html where values are shown as distance 18.6 mpc (60,707,000 ly), angular size 11.2' and long axis 61 kpc (199,092 ly). So it seems that NGC 1365 really is twice as large as our Milky Way galaxy's disk.

    • Like 8
  6. Thank you very much for your responses. There is so much about this region that I don't really understand. For example, why the blue reflection nebula surrounding NGCs 6726 and 6727 takes on the shape that it does. Reflection nebulae are caused by light bouncing back in our direction off dust particles. The wispy filaments seem to radiate away in all directions from the two central concentrations and it looks like the dust there seems to be preferentially organised along those filaments. But why? Is it because they reveal some local magnetic lines of force? A puzzle.

  7. Generally, for personal casual viewing, I set my camera to bin 2 mode (effectively creating 9.26 square pixels) and set a fairly aggressive gain of 400+ so as to get quick results – usually with a maximum exposure time of 1 minute. But because I wanted to get as much detail for this field's fainter objects as realistically possible I reverted back to bin 1 mode (4.63 square pixels), upped the exposure time to 2 minutes and cut back the gain to 270.

    Image 1 is a view of the full field.

    424460039_Image1CrA.thumb.jpg.36fd366e6fd600c9d2cfd6a93861ac89.jpg

    Image 2 is the same but with the brighter objects labelled.

    5483682_Image2CrA.thumb.jpg.e1c4820f78829c87586bbb74f024ca81.jpg

    Image 3 is a zoomed in view of the diffuse nebulae.

    695515725_Image3CrA.thumb.jpg.2a81bcf3bac1c962c0470b7ba32a8ffc.jpg

    And Image 4 is further zoomed in to show the fainter objects in more detail.

    869106116_Image4CrA.thumb.jpg.86c36c85da30ad2c61a1ae52ce5fa2aa.jpg

    Bernes 157

    The elephant in the room is clearly the dark nebula which swoops down from top-right to hook up and left in the centre of the frame. Most sources put its distance at 420ly away from us. This molecular cloud is a region of cold gas and dust that is so dense that its central part almost totally obscures the background stars of the Sagittarius arm of the Milky Way some 4,500ly behind it. We can see that the darkest parts fade away quite abruptly into a fringe of less dense clouds that generally impart a brownish hue to the background stars. At the location where the dark nebula hooks upwards its width including the fringe seems to span at most ¾ degree which at 420ly distance equates to about 5ly. Without knowing how deep the clouds are there it's not unreasonable to assume that the depth is also about 5ly. Overall, this dark nebula provides a dramatic backdrop to the other actors on the stage.

    The naming of this dark nebula has a fascinating history which you can find at www.surastronomico.com/sec-58-shedding-light-on-bernes-157.html Stretching across almost 8 degrees of sky it is mostly out of frame off to the upper right and here we see only one end of it. Its total mass is equivalent to about 50 times that of our Sun. If you look at images that show the full extent of Bernes 157 you can see why it has the nickname “The Anteater Nebula”. The two patches of blue reflection nebulae form its eyes and the curved bit at the end is its long snout. Here we see only its head and shoulders.

    IC 4812

    This is an easy object that you can't miss. Being so obviously sited in front of Bernes 157 it looks at first sight like it may simply be part of the nearer edge of that dark nebula. But is that really so? It seems fairly clear that this reflection nebula is caused by light emitted by one or both of the two bright stars associated with it (HR 7169 and HR 7170 - but also collectively known as BSO 14). Whether it is just one of of those stars or both must depend on how far away they are. Finding a sensible answer by searching the internet has proved to be extremely problematic but I have finally relied on Cartes du Ciel which says 139ly and 252ly respectively. That means that although they are separated by only 13 arc seconds they cannot be gravitationally bound and thus they are only an optical double. They have almost the same visual magnitudes (6.4 and 6.6). But sources agree that they are of different spectral types. HR 7169 is B9V and HR 7170 is B8V-IV. Thus HR 7170 is the brighter of the two which figures as it is 113ly further back. It seems that each is itself a multiple star system consisting of 2 and 3 members. Since both stars seem to be well in front of the 5ly deep Bernes 157 behind them it looks like the blue nebulosity is not in fact part of that dark nebula - which runs counter to most descriptions that I've read. And there's still the question of whether just one is creating the nebula or both. A puzzle for solution by someone who is better able to cope than I am.

    NGCs 6726 and 6727

    Also easily seen is the spidery blue reflection nebula created by these two objects. Although only just hinted at in our view, long exposure images confirm that this nebula forms a continuum with IC 4812 and overlies the hook part of dark Bernes 157. Again, the question arises as to whether this nebula simply illuminates the nearer part of the dark molecular cloud or whether it is closer to us, like IC 4812. Its two sources seem to be distinct stars (clusters?) embedded in bright nebulosity.

    NGC 6729

    This designation is given to quite a large region to the right of the blue reflection nebulae. It includes the bright fan shaped emission/reflection nebula which is quite obvious in our screen view. It also contains various Herbig Harro objects (see below). The following description of that brighter part is clipped from a NASA article. “Caldwell 68, also known as NGC 6729, is located roughly 400 light-years away in the constellation Corona Australis, making it one of the closest star-forming regions to Earth. It is a small part of the larger Corona Australis Molecular Cloud. It was discovered by the German astronomer Johann Friedrich Julius Schmidt in 1861 and has an apparent magnitude of 9.5. The fan-shaped nebula appears to extend out from the star R Coronae Australis ... toward the star T Coronae Australis. The star that illuminates Caldwell 68 is known as a T Tauri star - a type of young star whose brightness fluctuates over time. Often, T Tauri stars have circumstellar disks. These debris disks surround some young stars and could develop into solar systems much like our own.”

    Another description of R CrA from Universe Today is “Here we have another unusual one – a “Herbig Ae/Be” pre-main sequence star. The star is an irregular variable with more frequent outbursts during times of greater average brightness, but it also has a long-term periodic variation of about 1,500 days and about 1/2 magnitude that may be linked to changes in its circumstellar shell, rather than to stellar pulsations. Although R Coronae Australis is 40 times brighter than Sol, and about 2 to 10 times larger, most of its stellar luminosity is obscured because the star is still accreting matter.”

    HH 100

    A real challenge for EEVA! This Herbig Haro object is really small and faint. Nevertheless it can just be seen on screen as an upside-down and back-to-front comma. You'll notice that I've also labelled a tiny red patch of nebulosity to its upper left as “!!”. Apparently that patch was the object first named Bernes 157 before the name was transferred to the dark molecular cloud. It may now be labelled HH 101? It seems that both objects are associated with R CrA and a detailed view and explanation can be seen at https://www.eso.org/public/news/eso1109/ - you will need to turn the image there upside-down to match our view.

    NGC 6723

    This globular is much, much further away than the other objects in our view. In fact it's so far away that it is located below the bulge of the Milky Way's central core. Even so it is bright and presents a fine sight in our on-screen view although it is just below naked eye visibility at mag. 6.8. As seen it spans about 9 arc minutes but Simbad quotes it as being somewhat larger at 11½ arc minutes. At 28,400ly distant this gives a diameter of 98ly. In our view the inner part is well overexposed so it's not easy to see that in fact, as globulars go, this is a fairly open one with little evidence of core concentration. It is of intermediate metallicity meaning that it contains many younger stars with higher metallicity content. If you enlarge our image you can see that the outer regions of this globular contain many deep blue stars.

    Epsilon CrA.

    At only 98ly away this star dominates the upper left part of the frame. It is a main sequence class F4V yellow-white dwarf star with a mass of 1.23 times that of the Sun. In fact it is an eclipsing binary varying in brightness between mags. 4.74 and 5 over a period of 14 hours. Two very similar eclipses take place within each orbital period. First a faint star passes in front of the bright one that gives us 95 or so percent of the light, and then the bright one passes in front of the fainter.

    HD 175714

    It's not surprising that this single star is dimmer at mag. 7.7. It is 592ly distant putting it quite a bit further away than Bernes 157. So it is shining through that dark nebula's fringe. That is unless the nebula itself is receding away from us there. Also it is a class K5 star so quite a bit dimmer and redder than the Sun which probably explains the colour that we see.

    HD 176617

    According to Simbad this star's class is M3III, putting it well into the red dwarf end of the main sequence, and its magnitude is 8.2. The only distance value that I can find is 250ly +/- 240ly! So it's probably closer than Bernes 157.

    HD 176423

    Being of spectral class A1 this star is intrinsically very bright but has a visual magnitude of only 9.5, even dimmer than HD 176617. Thus it must be further away and probably lies behind the fringe of Bernes 157 although it does not seem to have been reddened appreciably by that dark nebula.

    In conclusion, it seems that EEVA is viable for this target region, even for the dimmer objects and I'll look forward to sharing it with visitors at some time in the future when we are released from Covid19 lock-down.

    Vixen R200SS; SW AZ-EQ6 Pro; ZWO ASI294MC Pro; Baader MPCC III; Bortle 4.5

    SharpCap livestack using 2 minutes exposures at 270 gain.

    • Like 5
  8. If you frequent the Sky and Telescope website you may have noticed a recent article on 14th July about the Ptolemy Cluster M7 and some nearby objects. It's a good read and I recommend it. You can find the article at https://skyandtelescope.org/astronomy-news/in-heaven-with-m7-a-portal-into-the-deep/

    Since M7 is high in the evening sky at the moment I thought that it would be fun to recreate the main image included in that article. However, my current EAA viewing fov is too small to include all of the mentioned objects in one frame. So I had to wander around the sky a bit to find them all. This allowed me to make up a mosaic of 5 frames (2 x 2 + 1 central superimposed). Each frame was a SharpCap livestack of 30 x 8 seconds at 400 gain. The on-screen view of the central section is shown below.

    95348177_CaptureM7.thumb.PNG.9ab43306db7346b5d1b967cbfdde7642.PNG

    To find the mosaic as posted in Astrobin use the following link : https://www.astrobin.com/ide14h/ In addition to the plain mosaic image there I've added a labelled version (version B which you can select to view) because Astrobin's hover-over labels miss a couple of the objects mentioned in the article. In particular the tiny blue planetary nebula Cannon 2-1 as discovered by Annie Jump Cannon of OBAFGKM fame.

    • Like 4
  9. On 1st April I viewed a few objects including this one in Puppis (the Stern Deck part of the old broken-up constellation of Argo Navis). At the time it did not seem worthwhile posting the result here, the nebula at first being somewhat underwhelming. But it's an interesting region and I thought that it might be worthwhile to see what a little brightening with Photoshop could achieve. Usually when the NGC 2467 region is displayed in amateur images on the internet you'll find that the total integrated time totals a few hours. This one was 4 minutes (4 x 60 seconds livestack). So there is a big difference in quality and detail. Nevertheless the brightened EAA view does show the basics.
    1602723260_NGC2467Region.thumb.jpg.050eeb176063d5a2fd48c713de2cbfd0.jpg

    2051337135_NGC2467Regionlabelled.thumb.jpg.a6aae50446bb1a0e55dbc756a5acbb34.jpg

    The central section is an active star forming region of which the brightest part (NGC 2467) clearly shows an ionised HII stellar nursery. Most articles on the internet say that the main contributor to this red emission nebula is the massive O6 star HD64315 which is lost in the bright area circled in the annotated image. However a recent (2017) analysis concludes that that may not in fact be the case. It finds that the star is a multiple star containing at least two binaries with a likely total mass over 90 times that of the Sun and that it was formed without an accompanying cluster. So, on that basis, it is not part of NGC 2467. Who to believe? All sources agree that the two star clusters Haffner 18 and Haffner 19 are not immediately associated with NGC 2467 being just line of sight objects. 1 million years old Haffner 18 contains about 50 stars some of which are massive but short lived. Haffner 19 is a compact cluster with a Strömgren sphere (like the Rosette Nebula) where the cluster is surrounded by an ionised HII region. Its age is estimated at 2 million light years and yet Wikipedia says that the two clusters may be considered to be a binary cluster. Go figure.

    You would think that it would be an easy internet search to find the distances to NGC 2467 and the two Haffner clusters but not so.

    The ESO puts the nebula at 13,000 light years but Simbad says 1,355 parsecs (i.e. 4,422 light years). Wikipedia quotes both 4,420 and 20,500 light years on the same page! Given its size in the image I'm more inclined to believe the smaller figure. As to the two clusters, the ESO says that Haffner 18 is between 25,000 and 30,000 light years away, Wikipedia says 19,200 light years and Simbad says 19,264. A SAO/NASA paper suggests that Haffners 18 and 19 lie at about the same distance at 22,500 light years (which might tie in with Wikipedia's reference to the two clusters being a binary cluster were it not for the age discrepancy). So at the very least it would seem that both clusters are much farther away than NGC 2467.

    HD 64568 is a hot, extremely massive main sequence blue-white star that is the prototype of the O3 V((f*)) spectral category.”

    The bright star HD64455 is a foreground B8 IV subgiant. Its distance is somewhere between 1,300 and 4,000 light years. And, of course, the other brighter stars are foreground objects too including OR Puppis which at only 900 light years distance is an M7 variable star having a brightness range of 6.85 to 7.10.

    The area is popularly known as the Skull and Crossbones Nebula but good luck finding out why from this image!

    Vixen R200SS; SW AZ-EQ6 Pro unguided; ZWO ASI294MC Pro; Baader MPCC III; Bortle 4.5

    SharpCap livestack 4 x 60 seconds at 400 gain

    • Like 13
  10. The presentation seemed to go quite well. It started with a shortish illustrated slide show followed by the video mentioned in this thread. Answers to audience queries were helped by using further slides that were organised by topic. Since the presentation (explaining to a general public audience the history and use of EAA) is possibly suitable for other audiences and since it seems a pity to throw away the materials that were used, I've put together a folder containing the slide show and the video mentioned earlier in this thread. If you are interested, let me know by pm giving an email address and I will arrange to send a copy of the folder to you. Feel free to modify the slide show and / or substitute your own video as you like.

  11. I was recently asked to demonstrate the use of EAA at an upcoming meeting at a famous old 19th century observatory arranged by a local historical society. It was suggested that in case outdoors viewing was not possible because of inclement weather I might give an indoors presentation instead. The attendees will be the general public who's astro knowledge is expected to be minimal. So any presentation will need to be quite basic. I thought it might be useful to include a short video demonstrating how EAA works and so last Saturday night I recorded a session viewing M83. It probably won't be of much interest to most viewers of this forum who will already be experienced in EAA use but some newcomers to EAA may possibly get something out of it.

    The YouTube link is https://youtu.be/C1Dgev063eE

    • Like 2
    • Thanks 1
  12. Mike - based on past experience when using an uncooled Sony IMX178 camera I bought a 2” version of the Baader filter to go with the then new ZWO ASI294MC Pro. But in the hurly-burly of getting to grips with the new camera and new (to me) software SharpCap I never could quite get things to work properly when using the filter and eventually I put it aside. Some 8 months later I thought that I'd try it again and after creating some new flats it immediately worked like a charm. As they say, “go figure”. The consequence has been that for the last few months I have mostly avoided viewing when more than an eighth Moon is up due to the sky glow it creates but now I'm quite comfortable getting out under most Moon conditions. So using the filter allows me to greatly extend my viewing time. And even on moonless nights in my Bortle 4.5 area it does quite a good job of suppressing the effect of the light dome that rises over my neighbouring city. Also, I haven't noticed that it adds the need for much, if any, extra exposure time when viewing. So, although a bit pricey, I do recommend using the filter as a very productive unit.

    David

    • Thanks 1
  13. Old enough to recognise the heading to this post? Leslie Philips' catch phrase in The Navy Lark a radio program which ran from 1959 to 1976.

    If you start at the Lagoon Nebula showing in its usual orientation and move about a degree to one side and down a bit you'll come to this very interesting patch of sky. Located in the Sagittarius arm of the Milky Way and floating in front of the myriad background stars there is this mix of dark, emission and reflection nebulae.

    Last night the Moon was waxing gibbous being 78% lit. Normally I wouldn't have bothered to view this kind of object in such conditions but I wanted to see what difference a new Baader Neodymium (Moon and Skyglow) filter could make and it sure didn't disappoint. With the camera set to bin-2 mode, gain set to 400 and exposure set to 60 seconds the 8 inch Newt picked up quite a respectable on-screen view. Not a patch on long exposure images of course but satisfying nevertheless. This is one more target to add to the public outreach viewing list when, one day, we can once again get out among the public.

    This was the last target viewed for the night and after shutting down I noticed that the main mirror was slightly dewed over, Did that affect the quality of the image? Hard to say. I'll try again and compare in a few weeks time when the object will be higher in the early evening sky at a time that is less prone to dew. What was certain was the the outside of the observatory's dome was quite literally streaming with dew run-off. It's quite remarkable how the dome creates its own favourable mini-climate even 'though it has an extremely wide up-and-over viewing slot.

    1604938419_CaptureM83.thumb.PNG.ab01d26e8bbd09977290ceb12fe3198d.PNG

    The later processed image better displays the emission and reflection nebulae.

    1587470013_IC4685.thumb.jpg.19f2bfe4ad66e0be6d56c6a7d150d0c8.jpg

    The labelled version identifies some of the many distinct objects in view and gives some background information as to distance and size. The main part of the diffuse nebula is IC 4685 across which you can see dark nebula segments snaking their way. One of them is catalogued as Barnard 303. I couldn't find catalogue numbers for the other parts. NGC 6559 is given to both the bluish reflection nebula surrounding a small group of stars and the bright red shell-like emission nebula close by, probably because the same stars are making both nebulae visible. The separation of the two lobes IC1274 and IC1275 is caused by the superimposition of the dark nebula Barnard 91 which is simply part of the much larger cloud of cold dark gas and dust that runs from top to bottom through the frame. Clearly this is closer to us than most of the background stars unlike the smaller and fainter dark streak further over to the right. That is at least partly covered by the background stars. IC 4684 near the bottom of the frame is another reflection nebula.

    1129037617_IC4685laballed.thumb.jpg.2ab4fd54ca10033870e6441bba6296e4.jpg

    As to distance and size, it was somewhat difficult to find out precisely how far away these objects are. Most internet sources quote either 4,000 ly or 5,000 ly but they were not what I would regard as authoritative typically being postings of amateur images. One outlier was an image taken from Namibia and that quoted 5,800 ly. Given the excellent nature of that image and the painstaking care that must have gone into creating it, it is reasonable to give more credence to the distance value it quotes. So it seemed reasonable to use a distance of 5,000 ly here with this image. On that basis the image spans 121 x 82 ly. The size of IC1274 is 11 ly, the length of the red emission nebula part of NGC 6559 is 13 ly and IC4684 is 4 ly across ( Sol to Alpha Centauri).

    Vixen R200SS; SW AZ-EQ6 Pro, ZWO ASI294MC Pro bin-2; Baader MPCC; Baader Neodymium (Moon and Skyglow) filter, Bortle 4.5

    SharpCap livestack 17 x 60 seconds exposures at 400 gain. Later adjustment in Photoshop.

    • Like 5
  14. Last night was a rare event. No Moon all night. No clouds. Very little light pollution. And no dew. My theoretical Bortle 4 skies don't often perform to specification but last night they certainly did. And it's M83 season! It rises just before dark, transits just after midnight and sets just after dawn. And when it transits it's just 3 ½ degrees away from zenith. What more could one want?

    For EAA work M83 is big, bright and splashy. At a public event it's best to use it to end one's viewing session. It is such a showstopper that most everything else that might follow would be a bit of a come-down. So what makes it so easy to view? The answer is primarily that it is very close – well at least as far as galaxies go. Just shy of 15 million light years. It's almost face-on to us so it's easy to make out its central bar and its spiral arms. And it is undergoing a massive amount of starburst activity which makes for an interesting juxtaposition of its many bright HII knots and clusters with the blue of the myriad stars in the body of the arms. This starburst activity is clearly located mainly along the leading edges of the arms. Add in the yellow glow from the core and you have got quite a colourful display.

    Of course there are many articles about, and amazing images of, M83 on the internet and they are well worth looking at. M83 is about half the size of the Milky Way. Apparently it is at the centre of a group of galaxies and it is possible that tidal interaction with its near neighbour NGC 5253 has caused the starburst activity that we now see. That it is a turbulent region is confirmed by our having detected six supernovae there in the last 100 years.

    It seems that M83 was first discovered by Nicolas Louis de Lacaille in February 1752 when in South Africa. With our experience using our fancy modern equipment we no doubt blithely assume that he saw something like what we now can so easily see. But that was not the case at all. His description was “Small nebula, shapeless”. His discovery must have encouraged Messier to look for it from Paris in February 1781 even 'though it was so low in his sky – it is the southernmost galaxy in his catalogue. Messier's description was “Nebula without star ... it appears as a faint & even glow, but it is difficult to see in the telescope, as the least light to illuminate the micrometer wires makes it disappear. One is only able with the greatest concentration to see it at all”. Even James Dunlop in 1827 had difficulty in determining was he was looking at from Australia. He described it as “a very beautiful round nebula, with an exceedingly bright well-defined planetary disk or nucleus, about 7" or 8" diameter, surrounded by a luminous atmosphere or chevelure, about 6' diameter. The nebulous matter is rather a little brighter towards the edge of the planetary disk, but very slightly so. I can see several extremely minute points or stars in the chevelure, but I do not consider them as indications of its being resolvable, although I have no doubt it is composed of stars”.

    Vixen R200SS; SW AZ-EQ6 Pro; ZWO ASI294MC Pro; Baader MPCC; Bortle 4.

    SharpCap livestack 20 x 60 seconds exposures at 400 gain. Minor adjustments in Photoshop.

    M83 Screenshot.jpg

     

    M83.jpg

    • Like 8
  15. The Tau Canoris Majoris Cluster is currently well placed for viewing in the early evening. It's such an easy target that it shows up well in my SharpCap display even when using the 2 second exposure interval that I typically employ for GoTo slewing and framing. Visually, it's not particularly large, occupying only a small part of the camera's frame. But zooming-in to the 100% resolution display level produces a very satisfactory view.

    This is an interesting cluster – particularly if and when we can ever get back to public viewing at outreach events – as it has a number of talking points that can keep viewers involved. Overall it's roughly the same size as the Pleiades (15 light years). But whereas the Pleiades is only 430 light years away the distance to NGC 2362 is 5,100 light years which is why it looks so much smaller. It is very young. 4 to 5 million years seems to be its age. This is only about 4% of the age of the Pleiades. We know this because most of what we see in the cluster are massive class O or B type stars which (in astronomical terms) quickly change into red supergiants. But there are few red supergiants to be seen indicating the the cluster is not yet old enough for most of them them to have changed. One would expect to see evidence of the molecular cloud of gas and dust from which such young cluster stars were born but there is none in their immediate surroundings. This is probably because such massive stars have the energy to very quickly disperse their nascent cloud. However, that energy does seem to be energising the giant HII region Sh2-310 one degree to the east (out of frame in the image below).

    Of course the star of the show (pun intended) is Tau Canoris Majoris itself. Clearly it outshines all of the other cluster members. Although it's very young, being so massive (see below) it has still had enough time to evolve away from the Main Sequence and change into a very hot and blue class O9 supergiant. But it's wrong to refer to Tau as a single star. It is in fact a very complicated multiple star system as indicated in the labelled enlarged crop from the full frame image. Initially components A to D were observed and catalogued by John Herschell in the 19th century **. In 1906 it was discovered that component A was a spectroscopic binary (components Aa and Ab) which was eventually visibly resolved in 1951. Then in 2010 component E was discovered lurking less than 1 second away from component Aa. Even more recently Ab itself has been found to be an eclipsing binary (Ab1 and Ab2). Thus there seem to be seven members of this remarkable star. Component A is thought to have a mass 86 times that of the Sun (Aa 50 + Ab1 18 + Ab2 18). Aa has a temperature of 32,000 degrees Kelvin and shines 280,000 times as brightly as the Sun. Factor in the brightness of the other components of A and you have a truly bright and massive star. It is said to be amongst the hottest known stars in the Universe.

    ** Looking at the image below I wonder how it was that Herschell determined that component D was a member of the multiple star. It's not too hard to see why he catalogued components A to C. But D seems so far away from A and although slightly brighter than its surrounding companions is otherwise pretty much indistinguishable from them. I've found no source questioning his decision but still I wonder.

    I had supposed that this cluster being observable from the northern hemisphere would have already had an entry in this forum but I haven't been able to find one. My apologies if that is not the case and the information given now is redundant.

    Vixen R200SS; SW AZ-EQ6 Pro; ZWO ASI294MC Pro; Baader MPCC; Bortle 4.5

    SharCap livestack 6 x 30 seconds at 300 gain; minor processing and labelling in Photoshop;

    Stack_6frames_180s PS.jpg

    Stack_6frames_180s PS 100 pct.jpg

    Stack_6frames_180s PS labelled.jpg

    • Like 5
    • Thanks 1
  16. Hi

    First of all, congratulations on your first live-stacked image. It gives a fine view of the PN and one that you will remember in days to come long after you have honed your skills further.

    I'm fairly new to SharpCap too so please don't think that the following is in any way authoritative. You say that half of the screen was brighter than the other half. There could be a number of reasons for that including the possibility that stray ambient light was entering the telescope's view from off to one side. But the thought that more immediately comes to mind is that you may not have been using a flat-field image when doing your live stack. The right hand side of your screenshot of SharpCap's display does not extend down far enough to see if you were using a flat in the preprocessing section. If not, you would be well advised to try that. Doing so is quite easy – there are many articles on the internet showing various ways to set your telescope up to take flat images. In SharpCap you use the Capture menu to select Capture Flat … and then follow the simple instructions given there.

    I hope that this helps. Keep up the good work.

    David

    • Thanks 1
  17. Face towards the centre of the Milky Way and then turn right around and face away from it. You are now looking in the direction of the globular cluster Messier 79 which lies in the constellation Lepus. This, and the fact that its distance is 42,000 light years makes M79 atypical of most globulars which are grouped around the galactic centre. Its size is about 118 light years. Dipping into popular commentary on the internet, it seems that M79 (in company with three other globulars) has immigrated from the Canis Major dwarf galaxy which is being torn apart by its close encounter with the Milky Way. However, the globular itself is zipping away from us at 720,000 kph.

    At 8 seconds individual exposures this image can only hint at the wealth of stars the globular contains as shown in much longer exposure images. Apparently most of its brighter stars are red giants but in this image there seem to be quite a few faint blue stars scattered around. It would be tempting to assume that they are blue stragglers but apparently not. Only 39 blue stragglers were detected in a 2007 study and they were concentrated at the core.

    The bright star at the lower right goes by many catalogue names including HR 1771 and ADS 3954. It is a multiple star system. The bright A component as seen here is magnitude 4.98. The next brightest component B is magnitude 6.56 but it is currently so visually close to A that it's lost in A's glare. However magnitude 9.2 component C is currently 3” away from A and can be seen to A's left.

    Vixen R200SS; SW AZ-EQ6 Pro; ZWO ASI294MC Pro cooled to -10 deg; Baader MPCC.

    SharpCap livestack 11 x 8 seconds at 400 gain with later minor processing in Photoshop.

    Stack_11frames_88s PS with inset.jpg

    • Like 4
  18. Very impressive image of the Eskimo, especially for your first try. Being new to SharpCap, have you found the sharpening tool in the livestack's enhancement page? If not you might want to try it out - in particular the Gaussian Blur section where you can play around with the two sliders and get immediate feedback. You may find that you can extract even more on-screen detail of the Eskimo's fur hood and the shape of his face.

    David

    • Thanks 1
  19. The night of the 18th January was as near perfect as you could want. It was only marred by having to wait until 10 o'clock for the Moon to set completely. But both clouds and dew were completely absent and the sky glow from my nearby city was quite subdued. A rare occurrence indeed. There are a couple of fairly easy diffuse nebulae visually quite close together in Carina and they made a good target for honing EAA skills with the new camera and software. NGC 3576 on the right of the image goes by the popular name of the Statue of Liberty Nebula and with a bit of faith you can just about see why. It is located at about 9,000 light years distant in the Sagittarius arm of the Milky Way (the next one in from us). By contrast the seemingly insignificant NGC 3603 to its left is 20,000 light years away and, according to Wikipedia, "is the most massive visible cloud of glowing gas and plasma, known as a HII region, in the Milky Way”. The bright central cluster (barely resolved here) contains three of the most massive and most luminous stars known.

    Vixen R200SS; SkyWatcher AZ-EQ6 Pro; ZWO ASI294MC Pro cooled to -10C; Baader MPCC.

    SharpCap livestack 30 x 15 seconds at 420 gain; cropped and minor processing in Photoshop.

    Capture NGC 3576 4.JPG

    NGC 3576 Stack_30frames_450s_WithDisplayStretch PS.jpg

    • Like 6
  20. Since this is a mosaic of 12 panels I don't think that it will qualify for the EAA forums even 'though each panel was acquired by using SharpCap's live stacking feature.

    Reduced resolution attached. A full 5,684 x 4,107 pixels resolution version can be viewed at https://www.astrobin.com/full/374poi/C/

    Vixen R200SS; ZWO ASIMC Pro; Baader MPCC, SkyWatcher EQ-AZ6 Pro.

    12 panels each 28 x 4 seconds unguided exposures at gain 420.

    SharpCap Pro; Photoshop;

     

    Eta Carinae Nebula Mosaic mid.jpg

    • Like 11
  21. Never say never Mike.

    Since an image of M42/M43 occupies just about as much real estate in my camera frame as this image of the Eta Carinae Nebula, its tempting to think of the two nebulae as being roughly the same size. But while M42 is about 1,500 light years away the Eta Carinae Nebula is 5 times further away at about 7,500 light years. So the Eta Carinae Nebula is much the bigger of the two. Knowing the angular dimensions of my camera frame and applying a little basic trigonometry I calculate that the part of the Eta Carinae Nebula shown in the image spans 176 light years horizontally and 123 light years vertically. The diameter of the round Keyhole Nebula is 6½ light years and so from one side to the other it is a bit larger than the 4 light years distance from us to our nearest star Alpha Centauri and yet, you can see that the Keyhole is packed with nebulosity and stars. What would our skies look like if we were located at its centre? Even the little dark squiggly dust pillar complex extending out from the cold dark gas and dust cloud at 8 o'clock from the Keyhole is 5½ light years long and so is a bit larger than the 4 light years Pillars of Creation in the Eagle Nebula M16. This is a land of giants.

    • Like 3
  22. The Eta Carinae Nebula is so big and bright that it is an easy naked eye object provided that local light pollution is not too bad. The best view of this object that I have ever had was at the eyepiece of a little 5 inch Newtonian some years ago. The sparkling display of star clusters was dazzling and the structure of the nebulosity was very well defined. Of course – no colour. Fast forward to now and a live stack of 15 second exposures easily produces all the colour that you can want albeit at the expense of star sparkle. This view of the inner part of the nebula was snapped last night before the clouds rolled in. Hope you like it.

    Vixen R200SS; SW AZ-EQ6; ZWO ASI294MC Pro cooled to -10C; Baader MPCC

    SharpCap live-stacks at 500 gain. Adjusted in StarTools.

    739624290_CaptureEtaCar3.thumb.JPG.be5ecad50f51db5933a118940c992669.JPG

    And a little adjustment using StarTools maybe better brings out some of the details. Eta Carina is the large over-exposed star near the bottom of the frame. The Keyhole Nebula is just below it to its left.

    79541396_Stack_8frames_120sST.thumb.jpg.cd14515a100e1d85dd12befa6851565c.jpg

    David

    • Like 5
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.