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iansmith

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About iansmith

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    Star Forming

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    Swindon
  1. Thanks x6gas. It’s 7 hours per narrow band channel, so 22.5 hours in total. Cheers, Ian.
  2. Thanks for the info MartinB. I doubt I will pursue this idea much further. For me there are other issues as well. For example, one reason for using ONAG was to avoid having to fiddle around finding a suitable guide star which I would have to do with an OAG. Having said that, does anyone have some real world performance figures with it? My current system gives me ~0.4” to ~0.7” rms with ~0.7” to ~1.3” peak to peak (depend on seeing conditions). Would an AO unit improve on that? If there was a chance of significant improvement then I would be willing to reconsider an OAG. Cheers, Ian.
  3. Thanks DaveS. I like to go deep with these objects to see if there is anything interesting surrounding the PN such as a faint halo or some such. I have so far only tried N2 on this and NGC 6058, which you can also find in my astrobin page. I’ve not had it very long and with the poor weather we’ve been having I haven’t had much chance to use it. Currently imaging NGC 40 with it, but not enough data yet to present it. Cheers, Ian
  4. Thanks MartinB. I have thought about adaptive optics, but as you say I’d need to find a bright guide star for it to work on. I have been wondering about if it could work, looking at a star from a larger field of view. In other words, could it work if I had a separate guide scope that was looking in the same direction, but was viewing a square degree of sky and then adjusted based on that. Will have to think more on that. Cheers, Ian
  5. This is my image of K1-16, a planetary nebula in the constellation of Draco, between 5200 to 7000 light years away. I have yet to come across much information about the PNe itself, other than its size which is put at between 1.6’ to 2’ across. It lies in front of a very distant galaxy cluster and to the south (left in my image) there is a bright 14th mag quasar, HB89 1821+643 which is part of the cluster. The quasar is 3.3 billion light years away but almost as bright as the central star of K1-16 which puts the power of quasars into perspective. The central star is DS Dra and judging by the number of professional papers it is of great interest to professional astronomers. It is classed as a PG1159 variable star, one of 20 such stars and only one of 7 which are the central star of PNe. These types of stars exhibit a small amount of variability (~±0.01 magnitudes) which comes and goes. It’s also hydrogen deficient and carbon rich, showing the same kind of spectra as WR stars. WR stars are normally very heavy, but as the central star of a PNe (CSPN), DS Dra must have been below 8 solar masses to start with, which is much lighter than most WR stars. It is thought to have just finished it’s AGB phase and is now transitioning to a white dwarf. There is a suggestion that it underwent a late Helium flash which dredged up and expelled a load of Carbon into the surrounding environment. The current mass is reckoned to be about 0.65 solar, with a surface temperature of 140,000K. This high surface temperature probably explains the high terminal velocity of the winds blown off this star. They have been measured at about 3800km/s. The mass loss rate is now fairly low, estimated at ~10-8 solar/year. This fits in with the expected behaviour of a post AGB star. My image was taken between July and September of 2019 using an Edge HD11 at prime focus and a QSI6120 camera, binned 3x3, mounted on a Mesu 200. NB: 42x600s in Hα, OIII, NII blended as: NII, Hα and OIII for red, green and blue respectively and then spent ages messing about with saturation, hues, etc to try and get a pleasing colour image. BB: 15x120s in red, green and blue. The stars were removed from the NB images and the PNe was removed from the RGB images. These two images were processed separately before being combined to create the final picture. I would welcome any comments or criticisms, especially on how to improve. Cheers, Ian
  6. Thank you tooth_dr and MarsG76. Cheers, Ian
  7. NGC 6058 is a small PNe in the constellation of Hercules at a distance of 3.5kpc (11,415.47 lightyears) with a maximum diameter of ~45". I have found one paper that has done a detailed study of this PNe: https://arxiv.org/abs/1304.3248 According to the paper, there are 3 elliptical outflows, more or less in the plane of the sky. These show strong OIII emission (coloured blue in my image) indicating the presence of shocks at these locations. This suggests they are related to collimated outflows from the central star that occurred ~4800 years ago, ~4400 years ago and ~5900 years ago and currently have have polar velocities of ~68kms-1. The bright central arcs appear to be a ring, but spectroscopic studies show it to be a limb brightened barrel like shell similar to NGC 7354. It does appear to be more difficult to analyse so it’s position angle, relative velocities, etc are less certain than the other outflows. Its inclination to the plane of the sky might be anywhere from 50° to 130°. Its age is estimated to be ~3400 years old making it the youngest of the outflows, but this may be an upper estimate. The bright ring like structure is probably where it is interacting with the earlier outflows particularly their equatorial regions and is protruding through them and this is causing the gasses to slow down which would make it younger than suggested. These separate outflows suggest that the star underwent 4 different ejection episodes, with the collimation axis precessing between episodes. There are also two regions of enhance emission and some faint structure within the bright ring. As this is also present in the pro’s image I don’t think it is an artefact of my processing. On a purely speculative note of my own, this reminds me of the filamentary structure that can be seen in HST images of the Eskimo Nebula. In that PNe the filaments are thought to be the edges of bubbles of gas created by shocks as the outflow breaks out from the polar direction. https://www.astro.umd.edu/~jph/eskimo.html shows this for the Eskimo Nebula. Perhaps something similar is going on here? The image is composed of narrow band data for the PNe and broadband data for the stars: NB: 60x300s in Hα, OIII, NII blended as: 0.5* Hα + 0.5*NII, 0.4* Hα + 0.6*OIII and 0.15* Hα + 0.85*OIII for red, green and blue respectively. BB: 15x120s in red, green and blue. The stars were removed from the NB image and the PNe was removed from the RGB image. These two images were processed separately before being combined to create the final picture. I hope you like the picture. Cheers, Ian
  8. Very nice image. Cheers, Ian.
  9. I prefer the smoother finish to the galaxies in B, the softer stars doesn’t bother me. But as Adam suggests, mask them off before applying Noise reduction or mask the rest off and use MT to tighten them up after noose reduction. Cheers, Ian
  10. Nope, I like imaging at 2800mm. It’s great for small targets like galaxies and planetary nebula I wouldn’t worry too much about the dust bunnies, I’ve seen much worse. Flat fielding will take care of it. Not sure what the dark spots are. Cheers, Ian
  11. One thought occurred to me on using longer integration times. The longer the integration, the smoother the target will be, but you will also get more faint stuff in the background, which is bound to be noisy. To me (looking on my phone) the main targets look great, it’s just the background where you have some noise. I don’t think there is much you can do about this other than targeted noise reduction on the background. Cheers, Ian.
  12. Yes, being able to come back to the same target night after night (or, with our weather, year after year ?), allows you to capture much more data on it. I get anywhere between 4 to 8 hours per filter. I’m inclined these days to go for 8 hours, which makes for a low output of images, but I think the extra SNR makes for a better picture. Also, going mono allows for the use of narrow band filters and that brings the option to image when the Moon is up (depending on the faintness of your target and it’s proximity to the Moon). Cheers, Ian.
  13. Not bad, but you need more data. Aim for as much as you have time/patience for. At least 4 hours to double the SNR. Cheers, Ian
  14. Also known as PK 204.1+4.7, Kohoutek 2-2 is a large, faint planetary nebula in the constellation of Monoceros. It is probably an old planetary nebula and appears embedded within a complex of even fainter nebulosity. Whether this is part of the original star’s red giant envelope or is something unrelated is unknown to me. According to The Simbad database, the planetary nebula has a diameter of 6.9’ and a distance of 2816 light years. There doesn’t appear to be much more information than that available about this particular planetary nebula. This image was taken over several nights between the beginning of February 2019 and mid-March 2019. The equipment used was a Celestron Edge HD11 telescope with Celestron f7 focal reducer, QSI6120 CCD camera (cooled to -25 C) and Astrodon 3nm Ha and O3 filters. The scope was guided with an ONAG and Ultrastar guide camera. The mount was a Mesu 200. The exposures were: 32x900s, binned 2x2, through the Ha filter and 32x900s, binned 2x2, through the O3 filter, giving a total of 16 hours. The image scale is 0.67” per pixel. After stacking the images in PixInsight I then separated the stars and nebula and processed them separately, before recombining to get the final colour image. I would have liked to replace the NB stars with RGB stars but ran out of time. For both stars and nebula the red channel is 100% Ha, the green channel is 50% Ha, 50% O3 and the blue channel is 100% O3. I hope you like it. Cheers, Ian
  15. Nice image. I had a similar plate solving issue once with Abell 5. The catalogues are not always perfect! Cheers, Ian
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