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alan4908

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Everything posted by alan4908

  1. Hi Vlad I thought you might be interested in seeing the Pixinsight screen show (below) which I've taken with the cursor hovering over part of the green blob located at x= 51 and y = 40. The image is after I've performed DBE but before any PCC. This shows what happens to the linear RGB values as they are put through the non-linear stretching function (called Histogram Transformation in Pixinsight). So, for example, the red value before the stretch is 0.0066 and goes to 0.48 when it is stretched. If you make a table of the values you get: DBE (linear) DBE(non-linear) R 0.0066 0.4800 G 0.0071 0.5678 B 0.0068 0.5221 With R normalized to unity DBE (linear) DBE(non-linear) R 1.00 1.00 G 1.08 1.18 B 1.03 1.09 So, at the linear stage the green blob is 8% more peaky than the red whilst introducing a non-linear stretch makes the Green component 18% more peaky than the red. At this point it looks green. This is without any increase of saturation, application of PCC etc. In subsequent processing I would boost saturation, perform noise reduction etc to create a final image, these steps further increase the differences between the values (in my case the final image as a green component that is 60% more than the red component. My point is that even a very small percentage differences when in the linear stage can lead to very large percentage differences in the non-linear stage. Alan screen shot
  2. Here's some documentation of the Pixinsight Photometeric Color Calibration tool which might help answer your question: https://pixinsight.com/tutorials/PCC/index.html I presumed this was the consequence of the various non-linear operations performed between the linear to the final processed state. Alan
  3. If I look at the data at the stages after Pixinsight's DBE (image is linear), Photometric Colour Calbibration (image is linear) and the Final (LRGB non linear) I get these RGB values: DBE PCC Final R 0.00664 0.00679 0.40200 G 0.00707 0.00727 0.64300 B 0.00683 0.00679 0.62000 RGB ratios with R normalized to unity DBE PCC Final R 1 1 1 G 1.06 1.07 1.60 B 1.03 1.00 1.54 So, this particular green blob has quite a peaky spectrum with respect to the red. Hmm interesting, I don't recall seeing anything green in my M33 images but I shall go back and check ! Alan
  4. Thanks for the response Adam and highlighting more green blobs...However, I'm still somewhat puzzled about what these green blobs actually are. Alan
  5. Hi Vlaiv Yes, the colour is definitely interesting. Here's the image from Adam Block taken through a 20inch RC at the top of a mountain, I think he won an APOD for this so, I'm assuming that the colours are accurate. I've used Registar to align with my own attempt and marked the location of the green blob. As you can see very green. Yes - that is a thought.
  6. The Galaxy NGC3938 is located in the Ursa Major Cluster and is approximately 60 million light years from Earth. It has a large number of H II regions showing as pinkish regions on the LRGB image below. I've also shown an annotated image which has identified some of the background galaxies that are also in the frame. The galaxy doesn't seem to be often imaged, which perhaps is because it is relatively small, with an apparent size of 5.4 x 4.9 angular minutes. The image below represents just over 13 hours integration time and was taken with my Esprit 150. What is somewhat intriguing is the green(ish) blob which I've highlighted below. Since you don't often encounter green objects in deep space, at first I thought it might be a processing artifact but I checked a higher resolution image from Adam Block and sure enough it is there, looking even greener. The only thing that I could find at this location is the NED object SSTSL2 J115300.08 +440700.8, however, I not entirely sure what this object is - can anyone assist ? Alan NGC3938 NGC3938 (annotated) Mysterious green blob LIGHTS: L:32, R:11, G:21, B:15 x 600s, DARKS: 30, BIAS:100, FLATS:40 all at -20C.
  7. Five images from 2019. All taken with my Esprit 150 in combination with a Trius 814. Alan M76 NGC1333 NGC3344 NGC4157 NGC6995
  8. A close up of the open star cluster IC1848 which is embedded within the Soul Nebula (Westerhout 5). The LRGB image below, represents just over 21 hours integration time and was taken with my Esprit 150. To capture the detail of the emission nebula, I gave it an Ha blend into both the Lum and Red channels. Alan LIGHTS: L: 24, R: 17, G:20, B:11 x 600s, H: 19 x 1800s. DARKS:30, BIAS:100, FLATS:40 all at -20C.
  9. Thanks. I was quite impressed with the amount of detail revealed on NGC4216, as I mentioned above, I think this was mainly helped by a application of deconvolution on the lum data. Thanks for the information on the ASTAP program, I shall investigate further ! Alan
  10. Thanks for the comment ! Thanks, yes IC771 does look interesting, I was quite surprised how blue it came out. Thanks Bob - I think the deconvolution on the stacked Lum data helped to bring out the detail. Alan
  11. The galaxy NGC4216 is in the Virgo Cluster about 55 million light years from Earth. It is shown in the center of the LRGB image below with two main companions NGC4206 (top) and NGC4222 (bottom). Also displayed are a few background galaxies. The inclination of NGC4216 is 89 degrees so, it is almost edge on, making the revelation of dust lanes difficult, so I was quite pleased that I managed to capture a few details. I've also inserted an annotated version which shows the location of the background galaxies (if there are any PI experts who know how to stop PI writing different annotation identifiers to the same object please let me know.....). The image represents 12.5 hours integration time and was taken with my Esprit 150. Alan LIGHTS: L:19, R:12, G:14, B:30 x 600s. DARKS:30, BIAS:100, FLATS:40 all at -20C.
  12. alan4908

    Deep Sky III

    Images taken with a Trius 814 and a Esprit 150
  13. alan4908

    Vdb24

    From the album: Deep Sky III

    Vdb24 is a blue reflection nebula in the Perseus constellation which is embedded within the larger dark (reddish/brown) nebula LDN1442. It seems quite a rarely imaged object, I found only two examples on Astrobin and zero on SGL. It's quite an interesting image to process since the dark (brown/reddish) nebula tends to distort the star colours, particular the blue stars, pushing them towards the red end of the spectrum. It also has quite a few very bright blue stars, including one that acts to illuminate the reflection nebula itself. Anyway, here's my effort which represents just over 14 hours of integration time. The image is an LRGB and was taken with my Esprit 150.
  14. alan4908

    IC2087

    From the album: Deep Sky III

    Here's one you don't very often - the reflection nebula IC2087, which is embedded in the dark nebula Barnard 22. Since reflection nebula's are normally blue, I'm not too sure why this one is orange(ish)....I guess it must be the combination of the light from the bright blue star (out of frame), which is makes the background blue/purple, interacting with the dark brown/red of the dark nebula. IC2087 is also known as the little flame which seems appropriate since the stars above it appear like sparks from a small fire. For those with keen eyes, you'll also see a small red blotch above the fire, this isn't a processing artifact but a Herbig-Haro object which is a patch of nebulosity associated with newly born stars. So, you get quite a few interesting features in this image which was taken with my Esprit 150 and represents just under 10hours integration time.
  15. alan4908

    SH2-112

    From the album: Deep Sky III

    SH2-112 is an emission nebula in Cygnus and responds very well to Ha imaging, so I decided to blend the result of my 3nm Ha filter into the Lum and Red channels in this LRGB image. As you can see, there's quite a bit of detail within the nebula which is mainly from the Ha component of the image. It was taken with my Esprit 150 and represents just under 16 hours integration time.
  16. Thanks for the comment. Yes, I agree about the tidal tale, I was a little surprised about the length ! Thanks - yes, it took me quite a long time to acquire this, just below 7months..... Thanks - looking at my captured data my imaging started at 13th May and finished 5th December, so quite a long acquisition period which is not helped by the fact that I'm surround by trees which limits my local horizon. Since I have to dodge trees, certain phases of the moon and bad weather, I just let ACP work out when to image it. FYI, at my location gets to about 75 degrees at dark end. Alan
  17. Here's one you don't see often: - Arp297 which consists of four galaxies NGC5752, NGC5753, NGC5754 and NGC5755 all of which are located in Bootes. NGC5754 and NGC5752 are approx 200 million light years distance whilst NGC5753 and NGC5755 are much further away, at approx 450million light years. The more distant galaxies don't appear to be interacting now, although the extended arms of NGC5755 indicate that an interaction may of occurred in the distant past. By contrast, a gravitational interaction of the closer two galaxies has produced an extremely long (275,000 light years) tidal tale which extends from the starburst galaxy NGC5752, which you can just about see this on the image below. NGC5754 appears relatively unaffected by the collision. This LRGB image represents just over 11 hours integration and was taken with my Esprit 150. Alan LIGHTS: L:29, R:12, G:16, B:11 x 600s. DARKS: 30, BIAS:100, FLATS:40 all at -20C.
  18. Thanks. Yes, this one is hiding in plain sight ! Alan
  19. Thanks for the comment ! Alan
  20. SH2-112 is an emission nebula in Cygnus and responds very well to Ha imaging, so I decided to blend the result of my 3nm Ha filter into the Lum and Red channels in this LRGB image. As you can see, there's quite a bit of detail within the nebula which is mainly from the Ha component of the image. It was taken with my Esprit 150 and represents just under 16 hours integration time. Alan LIGHTS: L:16, R:16, G:13, B:10 x 600s; Ha x 1800s. DARKS:30, BIAS:100, FLATS:40 all at -20C.
  21. Thanks for the comment Gina. Alan
  22. Thanks Wim - yes, it does not often appear, although it is often captured in wide field views of B22. Thanks - it's quite different from my normal output. The style of the image reminds me a bit of an old dark oil painting. Thanks for the comment Thanks Alan !
  23. Here's one you don't very often - the reflection nebula IC2087, which is embedded in the dark nebula Barnard 22. Since reflection nebula's are normally blue, I'm not too sure why this one is orange(ish)....I guess it must be the combination of the light from the bright blue star (out of frame), which is makes the background blue/purple, interacting with the dark brown/red of the dark nebula. IC2087 is also known as the little flame which seems appropriate since the stars above it appear like sparks from a small fire. For those with keen eyes, you'll also see a small red blotch above the fire, this isn't a processing artifact but a Herbig-Haro object which is a patch of nebulosity associated with newly born stars. So, you get quite a few interesting features in this image which was taken with my Esprit 150 and represents just under 10hours integration time. Alan LIGHTS: L:12, R:15, G:12, B:20 x 600s, BIAS:100, DARKS:30, FLATS:40 all at -20C.
  24. I find the best way to inspect collimation errors is to pick an individual star and then zoom in on it to inspect it in detail. What you should see is all the colours aligning, in your case the red channel is slightly misaligned. To explain a little further, if I select a star at the right hand edge of the frame I get the image below. The star should be blue but you have a red misalignment effect as shown below in this highly magnified image. Hope this helps ! Alan
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