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  2. You have to love wide field images - not only a basketful of objects but also a serious 3d effect when contemplating their various distances. The large hydrogen region on the right is the 'nearby' Running Chicken Nebula (IC 2948; ~390 ly away). Shining through it is the bright field of stars known as the Lambda Centauri Cluster (IC 2944; 5900 ly). In the middle of the image, we see three, smaller, HII regions: RCW 61/Gum 41 (top; 2250 ly); IC 2872 (130 ly); and Gum 39 (1700 ly). There are two open star clusters on the left side of this image. Tiny Melotte 105 (5600 ly) is the one at the middle left, and IC 2714 (4000 ly) is the larger, looser looking one at the bottom. Photo stuff: 94 subs @ 60s ea. ISO 1600 Canon 6D with Tamron 500mm f/8 cat. lens.
  3. Like its more famous cousins, the Eagle and Orion Nebulae, this is a massive emission region of singly-ionised hydrogen gas (HII) that is being shaped by powerful stellar winds. It is also a region of active star formation. Gum 15 - also known as RCW 32 - is found in the constellation Vela, and is somewhere between 2200 and 3200 light years away, depending on who you ask. If anyone is planning on going soon, could they please send back an accurate measure? The dark lanes in the center and around the edges are absorption nebulae; long clouds of dust that block the light from the stars behind them. The lighter blue wisps appear to be reflection nebula. Photo stuff: 31 frames @ 300s ea. ISO 800 Canon 60Da on the RCX400 16" f/8, with a .67 focal reducer and an Optolong UHC filter

    © Gary Steel 2018

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  5. Last week
  6. Astronomy Workshop for Beginners at HVCC


    I'm a bit late, but have sent off a request to see if there is space and still going.
  7. CAS Member Meeting - Februrary 2018


    Due to the state of emergency issued by Christchurch City Council, and the data suggesting the weather is due peak at 10pm, I have been just been advised tonight's meeting has been cancelled. Selwyn has now also just issued a state of emergency.
  8. CAS Member Meeting - Februrary 2018


    This map shows the entrance to the building for tonight's meeting
  9. Earlier
  10. Collimation of SCT

    The before and after images certainly show the difference. Well done Terry
  11. Collimation of SCT

    Great stuff Terry! Are you coming to Stardate? We are having a collimation workshop on Saturday afternoon. Perhaps you might like to help out with SCT collimation? Rob
  12. Collimation of SCT

    Thanks for your helpful comment Bert. I used a video camera too. It makes the image so much easier to interpret. Your idea of a crosshair or a circle sounds like a very useful improvement to the method.
  13. CAS Member Meeting - Februrary 2018


  14. CAS Member Meeting - Februrary 2018


  15. Collimation of SCT

    Excellent tips, Terry. I used a similar method to collimate my SCT, i.e. the one you described with the artificial star, but in addition to that I used a modified webcam inserted into the diagonal and connected to a laptop and overlaid a crosshair (can be downloaded for free, search the internet for "Mire de Collimation") over the defocused artificial star that appeared on the computer screen. I centered the crosshair over the outer border of the defocused "star" on the screen and adjusted the scopes collimation screws to perfectly fit the image of the defocused "star" into the middle of the crosshair. This method really worked great for me, since it can be done in daylight (a cloudy day is good) and there is less risk of scratching the corrector if you have to use a screwdriver in the dark. In addition to that, the image of the rings of the artificial star is crisp and stable.
  16. Collimation of SCT

    Image names are not shown. The top one is before collimation, below is after collimation
  17. Collimation of SCT

    Collimating a SCT. Most of us will look at this subject with horror (as did I). First reaction is “I don’t want to fiddle with it”. Second reaction is “my telescope is ok, why change it”. I had the same thoughts until some photos showed asymmetry and some chroma. I looked at all possibilities in an attempt at avoiding the subject of collimation. I finally had to bite the bullet and accept that collimation was in order. This document outlines the steps I took and hopefully demystifies the subject by offering some handy tips. It is not difficult to do. Firstly, check if the telescope is functioning well by focussing on a star. Sure – wind the focus out, rings look concentric don’t they? Well I found that this was difficult to assess due to poor seeing. Things dance around so much, it is hard to tell whether the rings are concentric or not. I accepted the “probably ok” mindset. First tip. You can check collimation in daylight in your lounge. Set the scope up horizontally and then look into it from the front and move slowly backwards. You will see shadow of secondary mirror surrounded by rings out to the circumference of the primary mirror. Line up the outline of the secondary with a rim of its shadow and look at the symmetry of the rings. This is best done with one eye, as parallax will confuse the pattern seen. If these look concentric you are at least reasonably collimated. You can actually use this method to collimate (by using a card with a pinhole to give reproduceable eye position) but I found the changes confusing and difficult to assess. This is however a good way to make a quick check. This will tell you if you have a problem or not. I had a problem! Next collimate using a star. The method here is well described in a great article by Thierry Legault. http://www.astrophoto.fr/collim.html This shows beautifully the patterns you are looking for and shows the difference good collimation can make. Best to look at this now before you continue. He describes 3 steps, each gaining more precision than the former. The process is as follows. Second tip: use a video camera. You can see real time changes and saves you from going from front to back to adjust and check results. The camera can be rotated so top of picture is 12 o’clock on the scope. (Left and right are transposed though). Chose a bright star as high in the sky as possible to reduce atmospheric effect as much as possible at a magnification about the diameter of your primary (magnification 200 for 200mm scope) Set focus (forward or backward until you see the shadow of the secondary near the middle of a set of diffraction rings. Check (and adjust as necessary) that the shadow of the secondary is central to the diffraction rings. If adjustment is necessary, you will have to turn one or two of the 3 adjustment screws in front of the secondary set at 120 degrees from each other. Third tip: use a pointer (I used a plastic knitting needle) in front of the scope to define a radius. This is easily seen, and you can orientate the pointer to the narrow or broad radius as desired. Making adjustments There are 3 screws. Adjustments should be slight (an eighth of a turn or less). If one screw is loosened, then the other two should be tightened the same amount. There should be equal tension on all 3 screws at all times. None should be loose. Beware of overtightening which can distort the mirror. Be careful when using a screwdriver pointing towards your corrector plate. I found that I needed to tighten in the direction of the narrowest band. If this is opposite a screw, tighten this one and back off the other two. If the narrowest radius is between two screws, tighten both and loosen the third. I can’t guarantee this is the direction for all telescopes but since it is trial and error, you will soon find out which direction to turn. The star will move as you adjust. You will have to re-centre it each time you make an adjustment. If the star goes out of the visual field completely you have probably made too big an adjustment. Because of the need to re-centre the star you will have to use the motors to re-centre the image. Don’t forget to set the mount for terrestrial use or the “star” will wander off. Second step is finer adjustment. Use a star of less magnitude and use magnification 2 or 3 times the diameter of the telescope. Focus back and forwards slightly looking at the concentric rings and the bright spot in the middle. Adjust as above to make it true. Third step is to put the star in focus and look at the Airey pattern. The star should be dead in the middle of the diffraction rings. Adjust (with smaller turns of the screwdriver) if necessary. I did all this and found that my collimation had indeed been off. However, it didn’t work! Due to seeing conditions, especially at higher magnification, I found it impossible to reliably centre everything. Fourth tip: Use an artificial star. I made one of these in an hour using parts from the workshop. I used a small utility box (available from Jaycar) a super bright LED from an old garden light fixed in place with hot glue and made a hole in a piece of heavy grade aluminium foil with a small needle. The hole should be the order of 0.2 mm diameter. I used a small needle (the sort you use for removing a splinter) and with some cardboard underneath, penetrated the foil part way up the taper of the needle. I suspect a cardboard box and a torch would do the job. The hole should be smaller rather than larger. For my 200mm SCT I placed it on a fence post at 50 metres (should be at least 25 times the focal length of the scope). Collimation was completed in 15 minutes! Your collimation should be pretty good by now. Good enough that you can wait till a great seeing night and chose a star for checking. PS. The artificial star was made from junk, so I can’t give an exact recipe for this. If there is interest enough I will make one from proprietary parts and publish construction details in another article. I suspect that there may in fact already be one of these at the observatory somewhere for members to use? Feel free to add comments and tips to this thread. Samples below are both 30 second exposures unguided using 500D SLR
  18. The Robin's Egg certainly doesn't look like your usual planetary nebula. The well-defined ring is nowhere in evidence, nor is the usual symmetry. However, the professionals have found that the nebula emits a fair amount of OIII radiation, which is typical of planetary nebulae. This, along with the bright central star (a double!), helped to confirm it as a PN. I may try imaging this one again but using an OIII filter sometime in the future. Unfortunately, that project will have to wait for a while. Fornax - the constellation in which the Egg resides - is setting much earlier now. This makes gathering good data a bit challenging with all the summer heat in the atmosphere. Next year... Photo stuff: 23 frames @ 300s ea. ISO 1600 Canon 60Da on the RCX400 16" f/8
  19. The Southland Astronomical Society wishes to inform the public of the passing of one of its founding members, Russell Beck, who died on Saturday 10th of February 2018. Russell was not only a founding member, but also life member of the Southland Astronomical Society. He was Director of the Southland Museum and Art Gallery in the 1980's -90's, which helped the society to mount exhibits of an astronomical nature. He built the 12” telescope which was housed in the museum's observatory. It went on to serve the community for four decades, until is was removed at Christmas 2015. Russell was involved in the establishment of the observatory and ran it for some years. Russell will be sadly missed and our thoughts and prayers go to the Beck family at this sad time.
  20. Comet McNaught, the best image of my night

    One of the great photos. If only I'd had my camera back then.
  21. N44 Complex (R.F. Joyce Observatory; 07/02/2018)

    Well, that would depend on whether or not you subscribe to the purist movement or, like me, you're a card-carrying member of the Lying Bastards Astrophotography Group. For the former, I doubt that they would have any colour (no optical aid, even close up); a very wispy sense of white-gray, at most. For the LBAGs, we pretend that our eyes have permanent, unblinking cameras attached to them. Such a cyborg would tend to see the unfiltered gases as a palette of pale blue and pink, depending on whether or not they were a reflection or emission nebula (respectively), the dominant gas in the nebula, and its degree of ionization. I have just posted a wide-field photo of the area that is taken in visible (to a camera) light. Those are pretty close to what I would call the full colours.
  22. This is a follow-up to my previous image. The LMC will help you orient yourself. The N44 complex is the wee bit of blue and pink nebulosity to the right of centre, and, of course, the ever-impressive Tarantula Nebula (NGC 2070) is the big blue blob at the top of the image. Photo stuff: 96 frames @ 60s ea. ISO 1600 Canon 6D with a Tamron 500m f/8 cat lens
  23. N44 Complex (R.F. Joyce Observatory; 07/02/2018)

    Ah this is interesting. Great capture and some lovely details in the structure. You mentioned that it's false color, for those of us that don't know, what colours should each gas type be?
  24. until
    Astronomy Workshop Series for Beginners The Heathcote Valley Community Centre (HVCC) is glad to introduce the Astronomy Workshop Series for Beginners, a project designed to satisfy the curiosity of our small community. The first workshop is going to start on February 26th and there are still some places available, so we would like to make an open invitation to anyone keen to join us. The Rhythmic Sky – Astronomy Workshop by Erik Vermaat In this beginners course we are investigating how we see celestial objects move in the sky and why they move that way. This will change the way in which you see the sky, understanding the various rhythms that govern the firmament. THE RHYTHMIC SKY – 6 Week Workshop Mondays, 7.30 – 9.30 pm (120 min) 26 February – 2 April 2018 Price: $ 90 per six sessions Course description and enrollment information here: http://heathcotecommunitycentre.org.nz/2018/01/25/astronomy/ - Posted with the permission of CAS -
  25. Thanks Grant, a very informative site.
  26. My first composite narrowband image. N44 is a massive HII region about 163 kly away in the Large Magellanic Cloud. It contains several notable deep space objects: emission nebulae (NGC 1934, 1935, 1936; IC 2218), and star clusters (NGC 1934, 1937). In the centre of the image you can see its main feature, a "superbubble" of expanding gas. The bubble was, apparently, formed by the radiative pressure from at least on OB-type star (LH-47). Please note that this is a false-colour image. H-alpha is rendered in red, OIII in blue-green, H-beta is in deep blue. Photo stuff: Luminance: 18 frames @ 240s ea. H-alpha: 10 frames @ 240s ea. (colour set to 656.28) OIII: 10 frames @ 240s ea. (colour set to 500.70) H-beta: 10 frames @ 240s ea. (colour set to 486.00) ISO 1600 Canon 60Da on RCX400 f/8 with a .7 focal reducer
  27. Polar Aligning for Astrophotography

    I use binoculars to find the south pole and drop a line to the horizon to find a suitable landmark to align the polar axis. I stand behind the tripod and move the binos up and down a few times. That gets it pretty close. I start at Achernar and star hop to the pole via Beta Hyrdi, Gamma Octans (3 stars), then the asterism of Tau, Sigma and Chi Octans. The actual pole is near two fainter stars near sigma. This works even under bad light pollution in Christchurch. That is usually good enough, assuming the tripod is level and the polar axis altitude/latitude has not changed since last time. If there's still noticeable drift, use that to drift align. http://www.skyandtelescope.com/astronomy-resources/accurate-polar-alignment/ My rule for stars on the meridian (opposite the pole): If star drifts North => rotate clockwise. Works in both north and south hemispheres. By "drift north", I mean you could track the star by moving the telescope/camera toward the north pole (down). For stars on the east or west horizon, move the altitude/latitude up/down to bring the star back toward the centre. (Works north, south, east or west!) An even lower effort merdian star rule is the 3 o'clock rule: Call the direction the star drifts 12 o'clock. Rotate the polar axis azimuth to move the star in the 3 o'clock direction. This becomes the 9 o'clock rule in the northern hemisphere or if you are using a diagonal. How much to move? Try quite a lot and see if you can get the drift to go the other way. Then you can judge the correct amount based on drift rates.
  28. Polar Aligning for Astrophotography

    There are a few ways, including visual which would provide enough accuracy for the focal you plan on using. After you get the mount you may drop at the obs and a few of us can show you the general procedure.
  29. Polar Aligning for Astrophotography

    Southern pole finding is a challenge, as a newbie to this I gave up on visual methods and went to software. I start with a $15 compass to daylight align the stand to the pole, noting the world magnetic declination, for Chch magnetic south is roughly 24 degrees off polar south. Then a small level with a angular adjustment to get 43 degrees to roughly align Alt, basically need to be within 5 Degrees Alt/az for the software. Then when it gets dark I use Sharpcap ver2.9 http://www.sharpcap.co.uk/sharpcap/downloads The reason I use version 2.9 is the polar alignment is free in this version. Version 3 is yearly sub, small and annoying to pay like this, I'd pay a higher one off fee. anywhoo, off track, the alignment feature really helps and if you get the free version you can test camera and other setup requirements. Main trick is to get the right field of view, I use a ZWO ASI290 with a Orion 50mm guide scope, but I did do some calculations and one could use a 30mm guide scope with my camera. I believe a number of web cameras work in the software, really just a matter of getting FOV in the right range. Here is a short demo of sharpcap in action, northern polar alignment, but the software works in southern as well. https://astrobackyard.com/polar-alignment-in-sharpcap/ Software helped me, since my polar scope in my mount doesn't seem to work at all. regards
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