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Found 11 results

  1. Hello Astronomers, During the week when I was imaging the Helix Nebula, I was exposing it when it was east of the meridian. So as it hit 15 degrees past the meridian and the meridian flip happened, there was no guide star in the OAG FOV so I had the option to pack up and continue imaging another day or try for another object and hope for a guide star. As the sculptor galaxy was close to the location I slewed to it (with favour western horizon selected in the CGEM settings) and to my joy when the sculptor galaxy was framed a 1/3rd of the frame to the edge there was a guide star in the OAG... WOO HOO ... and so a second object imaging continued. After getting 3 nights worth of ISO400 10 minute RGB subs, I found that after processing the image was very amber at best.. almost sepia... and no matter what I done to it it always looked too green or purple at certain parts... just didn't look right. When I eventually got a chance, I was going to image some pure blue subs to add to the image to correct for the amber look, but as luck would happen, forecast was for at least a week of clouds and rain... this week was no better BUT I did see a break in clouds the other day with a 3/4 FULL MOON!!!! I couldn't afford to let this opportunity go to waste so I imaged NGC253 through a Halpha filter to cut out the moon glow... remembering that when imaging through Halpha in the 40D there is a lot of data in red (of course) and about 30% as bright in the blue channel.... I thought that I could use that added to blue as well as add some halpha to red and perhaps reveal some nebulosity. I only managed 8 x 15 minute subs before clouds started coming and 4 out of those were usable... here is the result. Thanks for reading my babble.... MG
  2. Observations of the Sculptor Galaxy ( NGC 253 ) by William and John Herschel ......... Part 2. Observations of "Caroline's Galaxy" by Sir John Herschel, 1830's Sir John Herschel, the only child of Mary Baldwin and Sir William Herschel, was born in 1792 when his father was in middle age and already famous as one of world's leading astronomers. Having excelled in school, and no doubt inspired by his famous elders, John Herschel decided upon a career as a 'man of science' and set out to pursue a wide range of interests; with one particular focus being a continuation of the study of the heavens commenced by his father and aunt, Caroline Herschel. In 1820, with the assistance of his father, John Herschel supervised the construction of a new telescope at Slough in England. As described in the extract below ( from a paper presented to the Royal Society in 1826, titled "Account of some observations made with a 20-feet reflecting telescope ... " ), the telescope had a polished metal mirror with clear aperture of 18 inches, focal length of 20 feet and was modelled on the same design created by his father. It is this telescope, in the 1820’s and early 30’s, following the death of his father and the return of his aunt Caroline to Hanover, that John Herschel used to 'sweep' the night sky and extend the catalogue of nebulae and clusters of stars that was published by his father ( see W. Herschel's Catalogue of One Thousand new Nebulae and Clusters of Stars ). On the 1st of July 1833, having complied sufficient observations, John Herschel presented to the Royal Society an updated list of the positions and descriptions of the Nebulae and Clusters of Stars that he had thus far observed. As noted in the introduction to the paper published in the Philosophical Transactions, he had planned to wait before publishing until he had complied a fully comprehensive general catalogue of objects visible from the south of England. However, due to his expectation of “several more more years additional work” needed to complete the task and his assessment that he now was in a position to address, at least in part, the then current “... want of an extensive list of nebulae arranged in order of right ascension ...”, he elected to present his list, “ ... simply stating the individual results of such observations as I have hitherto made ... “. It was not until October 16, 1863, some thirty years later, that Sir John would deliver to the Royal Society his General Catalogue of Nebulae and Clusters of Stars. As well as introducing many objects that had not previously been recorded, Sir John’s list of 1833 included a re-examination of, and in some cases a small correction to, the positions of many of the deep sky objects observed by his father and noted down by his aunt. One of these re-visited objects was, unsurprisingly, the large and bright nebula discovered by Caroline Herschel in 1783 and recorded in Sir Williams’s catalogue as V.1 / CH 10 ( object number one, of class five ( very large nebulae ) / Caroline Herschel #10 ). In total, John Herschel records around 2500 observations of nebulae and clusters of stars in his 1833 paper; with observation #61 being V.1, the “ Sculptor Galaxy “ . The measured position of V.1is given in RA and the angle from the north celestial pole ( all reduced to epoch 1830.0 ). The description can be interpreted by reference to the legend in the paper. Thus, “ A vL mE vB neb “ becomes “ A very large, much extended, elliptic or elongated, very bright nebula “. He also notes that in addition to this observation, #61, noted down from sweep #306, V.1 was also observed in sweep #292, “but no place was taken”. The figure to which he refers , figure 52, is included towards the back of his paper and is a sketch he made of the Sculptor Galaxy. to be continued ...
  3. The Discovery of the Sculptor Galaxy by Miss Caroline Herschel in 1783 On the 23rd of September 1783, sitting before her telescope in the field behind the house she shared with her brother William in Datchet near Slough in the south of England, Miss Caroline Herschel "swept" the sky searching for new comets and never before seen star clusters and nebulae. On this occasion, way down in the sky, not far above the Southern horizon, Miss Herschel saw and noted down a very bright and large nebula where one had never before been recorded and that was later recognised by her brother, Sir William, as the discovery by Caroline Herschel of the nebula he listed in his catalogue as H V.1. ( circ. 1825-33, Sir John Herschel, beloved nephew of Miss Caroline Herschel ) Today we know this 'nebula' to be, not as some thought then, a swirling mass of stars and gases within our own galaxy, but rather, a galaxy not unlike our own but way more distant than the outer reaches of of own Milkyway galaxy. Given various names, Silver Dollar Galaxy, Sliver Coin Galaxy or simply by its number in the New General Catalogue, NGC 253, it is most commonly called the Sculptor Galaxy and we owe its discovery to the first female professional astronomer. Caroline Herschel ( 1750 - 1848 ) ... ( link ) ( 1782 - 1783 ) ... ... ... H V.1 Observed ( by WH ): 30 Oct 1784 128 minutes, 17 seconds following and 1 degree, 39 minutes north of referenced star Description: - cB: "confidently bright" - mE: "much extended: - sp: "south preceding" - nf: "north following" -mbF: "much brighter middle" - size: 50' x 7 or 8' from: ( link ) ............................... The location reference to H V.1 ( NGC 253 ) in William Hershel's catalogue is in relation to a star found in Flamsteed's Catalogue, 18 Pis. Aust., which is #18 in Piscis Austrainus or Epsilon PsA, the 4th magnitude star HD214748 ( HIP111954 ) ( source ) ( Plate from "Atlas Coelestis" by John Flamsteed, 1646-1719 ) ------------------------------------- William Herschel found favour with the King and was granted a position as Royal Astronomer to George III in 1782. Shortly after, William and Caroline moved from Bath to Datchet ( near Windsor ) and took up residency in a rented house which, whilst somewhat delapadated and damp, had ample accommodation and fields for William to construct and deploy the large telescopes he wished to build. It was in these grounds that Caroline set up her "Sweeper" to look for comets and doing so also discovered a number of 'nebulae' including ( in 1783 ) what was later to become known as the Sculptor Galaxy. ( The Herschel house at Datchet near Windsor ) ( The Lawn, Horton Road, Slough ( Datchet ) - Google Maps ) ............. Caroline Herschel's "Sweeper" was a 27" focal length Newtonian telescope that was supported in a kind of altitude-azimuth mount consisting of a rotating table and a small gantry and pulley system that was used to effect altitude adjustments by sliding the tube up and down against a board used to provide stability. There has been some conjecture as to the exact details of the construction, however the image below, even if perhaps not the actual instrument, gives an indication of the overal design philosophy. Late in her life Caroline Herschel recorded details of her telescope in a booklet titled "My little Newtonian sweeper": In her memoir, Caroline Herschel describes the performance of her observations as the conducting of "horizontal sweeps"; from which one might assume the task consisted of setting the altitude in accordance with the plan for the night's observing and then slowing rotating the top of the table in azimuth as one observed and noted down the objects that passed across the view in the eyepiece. However, with the arrival of this new "telescopic sweeper" in the middle of 1783, Caroline Herschel added the new method of sweeping in the vertical, as noted below in an extract from her observing book ( source for both extracts: "Caroline Herschel as observer", Michael Hoskin, Journal for the History of Astronomy, 2005 ) .... The achievement of her discovery of the 'nebula' in the Sculptor constellation was remarkable in so many ways; not the least of which being the low path in the sky that the Sculptor galaxy follows when observed from Datchet in southern England - which on the night of her observation would not have exceeded 12 degrees or so above the horizon. Today, 234 years later, and blessed with 21st century luxuries and conveniences, I write on my IPAD and flip over to my planetarium application, SkySafari, and model the sky as it was seen by Caroline Herschel from near her house on the 23rd of September, 1783 ... ( SkySafari by Simulation Curriculum )
  4. The Sculptor or Silver Coin Galaxy ( NGC 253 ) in the Sculptor constellation - re-processed from the original subs The Sculptor Galaxay ( NGC 253 ) ( Please click / tap on image to see larger and sharper ) .................... The Silver Coin Galaxy ( NGC 253 ) in the Sculptor constellation ( aka the Silver Dollar or Sculptor Galaxy ). Caroline Herschel in 1783 was the first to recordthis bright ‘nebula’ in an area of the southern sky that Nicolas de Lacaille had called the “Apparatus Sculptoris” or “the sculptor’s studio”. Whilst relatively close to us compared to the billions of far more distant galaxies in the Universe, the great size of the “Sculptor Galaxy” and the huge distances involved are still hard to comprehend. To put this into some perspective, the light that is just now reaching one edge of the great disc left the opposite edge when the Earth was in the grip of last great Ice Age 70,000 years ago and the light we now see has been travelling towards us for over 11 million years. Details: NGC 253 - "Silver Coin" or "Sculptor" galaxy. Catalogue location: RA 00 48 23, DEC -25 11 52. From Image Solver: Image centre: RA 00 47 33.4 Dec. -25 17 11.1 Focal length: 1008.5 mm Field of view: 1d 19' 2.2" x 53' 0.3" Skywatcher Quattro 10" f4 Newtonian telescope. Skywatcher AZ Eq6 GT Mount. Orion Short Tube 80mm guide scope & auto guider - PHD2. Baader MPCC Mark 3 Coma Corrector & no filter. Nikon D5300 (unmodified). Field of view (deg) ~ 1.35 x 0.90. 20 x 180 sec ISO 800, long exp noise reduction on. Pixinsight & Photoshop. November 4, 2016 re-processed from original subs ( including Photometric Colour Calibration ) - September 9, 2017 ........... Details of Sculptor Galaxy from SkySafari for the 4th of November 2016 around 10pm local time ............. Annotated version ( using Pixinsight ImageSolver and Annotation scripts ) Sculptor Galaxy ( NGC 253 ) - annotated The cyan tags ( 35 or so ) relate to galaxies recorded in the Principal Galaxies Catalogue. The white tags are brighter stars as recorded in the Tycho-2 Catalogue. The number beneath is the magnitude of the referenced star. .......... Link to previous version below ...
  5. Halloween Observation Night Date: 31 October/ 01 November 2016 @ 22:30-01:00AEDT Location: Robertson Equipment: Celestron 8SE on CGEM, Televue 31mm Nagler Type-5, 17mm Ethos, 2X 2" Powermate, Astronomik UHC Filter I finally had a clear moonless night of observation, it just happened to be on Halloween night. I was looking for a new spot in the mountains where I could setup and a couple of months ago I came across a nice little oval miles away from the city and light sources so I was hanging to check it out. When we arrived, there were people having a BBQ and playing tennis with all of the court lights on, this was a bit of a bummer but I figured that they won't be forever and eventually we'll have a clear night of viewing, they left just after 22:30. Once they left and lights were off we had some nice views of 47Tuc, Tarantula Nebula area, Orion Nebula, The Sculptor Galaxy, NGC362 Globular Cluster, The Helix Nebula, an Open cluster in the south near/around Theta Carnia, Uranus and Neptune. 47Tuc: The globular cluster clearly stood out with its millions of glistening stars becoming denser toward the core. As I was observing the cluster in the 17mm Ethos, a slow moving and bright satellite flew past it. Those views are an event that makes a already great view even better. The view of 47Tuc were all awesome using both 31mm Nagler and 17mm Ethos with and without the 2X powermate. NGC362: This globular was a lot smaller and fainter than 47Tuc but still had a lot of individual stars all around it and individual stars visible within the core. Not as impressive as 47Tuc but still a nice view through the 17mm Ethos that's very easy to see with direct vision. NGC 2070: The Tarantula Nebula was a very nice view in all powers. The loops around a obviously brighter tentacular center were faintly visible, especially when observing it using the averted method. I started the viewing using the 17mm ethos through which I saw a fair bit of detail on a quite big tarantula nebula in the eyepiece. The surprising view was when I had a look at it through the 31mm T5 Nagler. The FOV was large enough and magnification low enough for being able to position the Tarantula in left lower with nebulosity amongst hundreds of stars to the right visible where a bit of the large Magellanic cloud was coming into the FOV. There was some fuzziness and nebulosity above it, I thought what a great view, this would make a great photo. The view of the tarantula system through the Nagler was amazing, I saw nebulosity, hundreds of stars and it was all easy to see. M42/43/Running Man: Orion Nebula was a bit of a disappointment. Granted that I was waiting for the Orion nebula to come above the trees and it was not very high in the sky at the time, but I am comparing it to the view I had in the past. The shape was visible, with the trapezium clearly visible with the stars being very stable and sharp points of light, so I figured that the seeing was good, so why do I not see more detail in Orion Nebula? I saw way more nebula and detail in the past. I added the UHC filter in the eyepiece and sure it faded the stars but it did not bring out more detail like it did before, actually it made the view worse! Using both the Nagler and Ethos, in both magnifications the nebulosity was not as defined and clear as in the past but definitely there. M43 was not as defined as I saw from the dam at the start of the year, back then the "comma" shape was clearly visible and even detail visible with in it, not tonight, I was struggling to see the comma shape. The Running Man was nearly visible, I actually think that at times I saw the running man shape, about as good as I remember seeing it at the beginning of the year, so seeing was (most likely) good so why am I not seeing the nebula like before? I started to investigate. First I checked to make sure that the corrector plate was not fogged over, it was not, that I removed the real cell filter in the back of the scope on the visual back thread, thinking that maybe it takes away from the view. When comparing with and without it, I saw no difference, even suspected the dew shield perhaps causing some kind of a slight blockage and compared with and with out it, no difference, finally I re-collimated the mirrors, they were slightly out, but after collimation it again made no difference. I put it down to a combination of Orion nebula being too low in the sky just above the trees and in the direction of the city. Here I'll mention that the sky did seem quite bright, I thought that maybe my eyes were dark adapted and it seemed like it but maybe not, more on this later with my experience when I was packing up for the night. I guess I have no choice than to try again and see if a darker/more transparent sky will make a difference next observing session. NGC253: The Sculptor Galaxy was relatively easy to see, whether inverted or direct vision I could see a brighter center in a squashed oval, cigar, shape. Occasionally I think I saw some darker "cracks" through the brighter core along with 3 to 5 faint stars glistening within the elongated shape. Sculptor is big in the FOV so I kept it on the 31mm Nagler, the Ethos did not make the view any better or easier to see. I could see the galaxy clearer the more I looked at it and feel like I didn't spend enough time looking at it. NCG7293: The Helix Nebula was a faint but a big ghostly smoke ring in the 31mm Nagler. It is very faint but the smokey ring can be made out using averted vision, or slowly moving the view with the keypad set to "3". I could make out the central neutron star, very small and faint but definitely there. Next time I observe this object I'll have to try looking at it through various filters instead of just bare, maybe more will be visible. Southern open star cluster: visible with eye as fuzzy patch closer to a dust cloud rather than stars but in binoculars and in the scope was visible as heaps of scattered stars, Looking at a star map it seems to be the cluster around Theta Carina. Looked like hundreds of pin point stars were spilled into the FOV. Quite a nice view, no nebulosity visible within its vicinity. Uranus: It is a pale greenish tiny disc that's discernible from the stars around it due to its color and a little disc as opposed to a point of light, I saw no moons. Neptune: Neptune was a pale tiny grey-blueish disc barely bigger then the two stars next to it. As with Uranus, I didn't spend much time on it since there's no hope of seeing any more detail. As a last object due to its late rising this time of the year, I wanted to see the rosette but it wasn't above the trees by 01:00 when we left. Still I found it in the eyepiece and identified the 7 stars located in the center making a rhomboid shape. I read online that this nebula is one where a UHC filter really makes it stand out, so I had to try it. The center stars were still behind tree tops and sad to say that with and without the UHC filter I did not spot any nebulosity. This object will have to wait a couple of months for a darker night and when it's higher in the sky. The 31mm Nagler, 17mm ethos, 2" 2X Powermate and the Astronomik 2" UHC filter is all we took... Honestly you don't need any more than this to observe using a 8" SCT. This combination covered various magnifications and limited fumbling around in the dark for eyepieces or filters allowing more time at the eyepiece. We had some great views tonight and I can't wait to be in a dark site when the seeing is even darker with less or no sky glow. Surprisingly the Astronomik UHC made the views worse on all occasions. Not like the Lumicon that gave me the wow views on the past, unfortunately the Carina Nebula was below the horizon so I couldn't test on it, the Carina is really breathtaking through the Lumicon UHC. Next time I'm going to compare the Astronomik 2" to the Lumicon 1.25" which I didn't have with me, I'm hoping that it was just the seeing otherwise I'll eBay it and get the 2" Lumicon. Another combination I want to try the 2" TVs with is through the f6.8 reducer. It seemed like there was heaps of skyglow. We made sure that we were in total darkness, no lights except purely red lights. Yes lots of objects and stars were visible, more than from home but when we were packing up when I turned on the car head lights and we were hit by white light destroying our night adaptation. After we were packed up, I turned off the head lights and I looked up and to my surprise the sight was similar to "dark adapted" eyes!!! Perhaps it was a night of bad seeing after all, which would explain the lack of nebulosity and detail within. The skyglow was obviously quite severe and it wasn't the best I've seen in a dark site, but still an awesome night of observing, leaving me with a hunger for more. Thanks for reading, clear skies, Mariusz
  6. Observations of the Sculptor Galaxy ( NGC 253 ) by William and John Herschel The very large and bright 'nebula' discovered by Caroline Herschel in 1783, that we now know as the Sculptor Galaxy, was observed a number of times by her 'dear brother' Sir William Herschel and by her 'beloved nephew' Sir John Herschel, Baronet. Some of these observations were recorded and published in the Philosophical Transactions of the Royal Society and, with respect to those by Sir John in South Africa, in the book of Astronomical Observations at the Cape of Good Hope. ......... Part 1. Observation of the 'class V nebula', H V.1, by Sir William Herschel, 1783 In 1782, with the fresh patronage of King George III, William Herschel, together with his sister Caroline, undertook the not inconsiderable task of transferring his astronomical equipment from Bath to Datchet ( near Windsor ) in England. Shortly afterwards, in 1983, Sir William began a "sweep of the heavens" with the very large Newtonian telescope of his design and construction. With this mighty telescope's twenty foot focal length and clear aperture of a little over eighteen and half inches, William was able to see fainter objects and smaller detail than any other astronomer of that time. ( source: The Scientific Papers of Sir William Herschel, Vol.1 ) ...... On the 30th of October, 1783, in the course of one of his "sweeps" with the twenty-foot telescope, Sir William Herschel observed Caroline's 'nebula' and noted down ( or perhaps more likely, dictated to Caroline ) a description of what he saw and a reference to its position relative to a 4th magnitude star in the Piscis Austrainus constellation, #18 Pis. Aust. ( with reference to Flamsteed's Catalogue ( or HD 214748 , HIP 111954 as we might call it )). Over the course of the next three years, Sir William would go on to view the Sculptor Galaxy a total of seven more times; as recorded in his paper "Catalogue of One Thousand New Nebulae and Clusters of Stars", presented to the Royal Society on the 27th of April 1786. ( Source ) Sir William's somewhat cryptic notes can be translated by reference to the key provide in his paper and doing so reveals the following: Class: V. ( very large nebula ) Number: 1 Observed ( by WH ): 30 Oct 1784 Reference star: 18 Piscis Austrainus ( Flamsteed's Catalogue; the best reference for the time - we might use epsilon Pis. Aust. or HD 214748 / HIP 111954 ) Sidereal direction rel. to star ( following or leading ): following star Sidereal time rel. to star: 128 min 17 sec Declination direction rel. to star: north of star Declination amount rel. to star: 1deg 39min Observed: 8 times ( up until April 1786, the date of the paper ) Description: - cB: "confidently bright" - mE: "much extended" - sp: "south preceding" - nf: "north following" - mbM: "much brighter middle" - size: 50' x 7 or 8' " CH" denotes that it was discovered by his sister Caroline Herschel The note he refers to expands on details of Caroline's discovery ... ...............................................
  7. I finally got around to get myself a 8" f/5 Newtonian with a GSO coma corrector and had my first go at the Sculptor galaxy (NGC253). The picture was taken from 33 frames, 180sec at ISO800. First off, I was impressed with how much light the scope collects compared to the ED80. I could already see the dust lanes on the individual frames. I noticed that I still had coma in the corners of the full image and searching the internet found that the coma corrector requires a 15-20mm spacer to work with DSLRs - Bummer! The stars are wider than what I am used to. According to the Bhatinov mask, focus should have been pretty spot on but compared to the ED80 my star width went from 3.6 to 5.6 pixels. Is this due to the missing spacer ring, still not perfect focus or that my mount (HEQ5) is struggling with the weight, or do I have to live with it? Just trying to understand what is normal for a reflector and what I can improve. Thanks in advance and clear skies! HJ
  8. From the album: Deep Sky Imaging

    This is a reprocessed image of the Sculptor Galaxy Data I captured and posted previously. During the week when I was imaging the Helix Nebula, I was exposing it when it was east of the meridian. So as it hit 15 degrees past the meridian and the meridian flip happened, there was no guide star in the OAG FOV so I had the option to pack up and continue imaging another day or try for another object and hope for a guide star. As the sculptor galaxy was close to the location I slewed to it (with favour western horizon selected in the CGEM settings) and to my joy when the sculptor galaxy was framed a 1/3rd of the frame to the edge there was a guide star in the OAG... WOO HOO :grin: ... and so a second object imaging continued. After getting 3 nights worth of ISO400 10 minute RGB subs, I found that after processing the image was very amber at best.. almost sepia... and no matter what I done to it it always looked too green or purple at certain parts... just didn't look right. When I eventually got a chance, I was going to image some pure blue subs to add to the image to correct for the amber look, but as luck would happen, forecast was for at least a week of clouds and rain... this week was no better BUT I did see a break in clouds the other day with a 3/4 FULL MOON!!!! :mad: I couldn't afford to let this opportunity go to waste so I imaged NGC253 through a Halpha filter to cut out the moon glow... remembering that when imaging through Halpha in the 40D there is a lot of data in red (of course) and about 30% as bright in the blue channel.... I thought that I could use that added to blue as well as add some halpha to red and perhaps reveal some nebulosity. I only managed 8 x 15 minute subs before clouds started coming and 4 out of those were usable.

    © Mariusz Goralski

  9. Hello all, Due to the rain and clouds I reprocessed the Sculptor and Helix Nebulae. A mate came over and found a astrophotography processing method in photoshop using the "high pass" filter... I gave it a go and it seems like I got a bit more detail out of the Sculptor Galaxy and Helix Nebula data... What do you astronomers think... improvement or too much? Thanks for looking, MG
  10. Hi all, This is my first post in this forum. I just received a HyperStar for my C14. Weather has natrually not cooperated, but I did manage to get out to take these shots last week. 80 x 20 second subs using a modified Canon T2i 16 flats 16 darks 16 dark flats 16 bias Stacked with ImagesPlus and final tweaking in Photoshop. I still need to work on the collimation for the Hyperstar. I also need to get my polar alignment nailed down so I can increase the exposure times. So far, I really like this f2 imaging! Hope you enjoy the photos. As always, comments and criticisms welcomed. Cheers Tim
  11. A new High Dynamic Range image of the Sculptor Galaxy ( NGC 253 ) captured over a number of nights in mid-September 2017 and processed with PixInsight using the DrizzleIntegration and PhotometricColorCalibration tools. The Silver Coin or Sculptor Galaxy ( NGC 253 ) in the Sculptor constellation. ( please click / tap on image to see larger and sharper ) On the 23rd of September 1783, sitting before her telescope in the field behind the house she shared with her brother William at Datchet, near Slough in the south of England, Miss Caroline Herschel "swept" the sky searching for new comets and never before seen star clusters and nebulae. On this occasion, way down in the sky, not far above the Southern horizon, in an area of the southern sky that Nicolas de Lacaille had called the “Apparatus Sculptoris” or “the sculptor’s studio", Miss Herschel saw and noted down a very bright and large nebula where one had never before been recorded. This event was later recognised by her brother, Sir William Herschel, as the discovery, by Caroline Herschel, of the nebula he listed in his catalogue as H V.1. In later years, her 'beloved nephew', Sir John Herschel, William's son, would record this 'nebula' as entry # 138 in his General Catalogue of Nebulae and Clusters of Stars ( eventually becoming the 253th entry in the New General Catalogue, NGC 253 ). Whilst relatively close to us compared to the billions of far more distant galaxies in the Universe, the great size of the “Sculptor Galaxy” and the huge distances involved are still hard to comprehend. To put this into some perspective, the light that is just now reaching one edge of the great disc left the opposite edge when the Earth was in the grip of last great Ice Age 70,000 years ago and the light we now see has been travelling towards us for over 11 million years. ........ More information on the discovery of the Sculptor Galaxy by Miss Caroline Herschel, as well as the later observations by both Sir William and Sir John Herschel, can be found in my Stargazerslounge blog, “The Sculptor Galaxy ( NGC 253 )” ......... This image was captured over a number of nights in the middle of September 2017 and processed on the 23rd; exactly 234 years from the day of its discovery by Caroline Herschel. With over 18 hours of total exposure, this HDR image attempts to capture the huge range of brightness levels; from the brightest stars and the core of the galaxy through to the numerous 'tiny' galaxies scattered throughout the image ( the total magnitude range is from around mag 8.8, for the brightest star, to 22+ for the faintest stars and galaxies visible in the image). Mike O'Day ...................... Capture Details: Telescope: Orion Optics CT12 Newtonian ( mirror 300mm, fl 1200mm, f4 ) Corrector: ASA 2" Coma Corrector Quattro 1.175x Effective Focal Length / Aperture : 1410mm f4.7 Mount: Skywatcher EQ8 Guiding: TSOAG9 Off-Axis-Guider, Starlight Xpress Lodestar X2, PHD2 Camera:Nikon D5300 (unmodified) (sensor 23.5 x 15.6mm, 6016x4016 3.9um pixels) Location: Blue Mountains, Australia Moderate light pollution ( pale green zone on darksitefinder.com map ).. Capture ( 16, 17, 19,20,22 Sept. 2017 ) 8 sets of sub-images with exposure duration for each set doubling ( 2s to 240s ) all at ISO800 273 x 240s + 10 each @ 2s to 120s total around 18hrs Processing Calibration: master bias, master flat and no darks. Drizzle Integration in 8 sets. HDR combination PhotometricColorCalibration Pixinsight & Photoshop 23 Sept. & 8 Oct 2017 Image Plate Solution ( this cropped image ) =============================================== Resolution ........ 1.324 arcsec/px Rotation .......... -180.00 deg ( South ^, East > ) Field of view ..... 57' 57.5" x 38' 40.1" Image center ...... RA: 00 47 32.809 Dec: -25 17 04.48 =============================================== .................... Designations and alternative names for the Sculptor Galaxy: CH10 ( Caroline Herschel # 10 ) H V.1 ( William Herschel, Class V ( very large Nebulae ) # 1 ) H 61, H 2345 ( John Herschel observations identifiers ) GC 138. ( John Herschel’s - A General Catalogue of Nebulae and Clusters of Stars # 138 ) NGC 253 ( John Herschel’s catalogue updated by Dreyer - The New General Catalogue of Nebulae and Clusters of Stars # 253 ) Caldwell 65 Leda 2789 ESO 479-29 Sculptor GalaxySilver Coin GalaxySilver Dollar Galaxy .................. Annotated image of the Sculptor Galaxy ( NGC 253 ) - showing the brighter stars ( from the Tycho-2 catalogue ) as well the galaxies recorded in the Principal Galaxies Catalogue ( PGC ). I have yet to complete identifying and annotating the very large number of ‘tiny’ galaxies in the image. ( please click / tap on image to see larger and sharper ) .........
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