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Martin Meredith

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About Martin Meredith

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    Sub Dwarf

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  • Gender
  • Interests
    Mountains, cycling, growing stuff
  • Location
    Northern Spain

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  1. Collimating- 10” quattro

    I have the 8" version of the same scope and would highly recommend using the Catseye autocollimator. Even so, the main problem is the jerky response of the secondary, so replacing the bolts by some from Bob's Knobs (or similar) is worthwhile, as is adding some simple home-made plastic washers between the tips of the secondary bolts and the secondary holder to smooth out the response. There are threads about this mod, which is often called the milk-bottle washer mod. Martin
  2. EAA first light with new kit

    Try this: I must admit they look like regular (i.e. on the protective window) dust shadows to me. Martin
  3. Washington Double Star Catalogue

    Mick, if you're still looking, try the following 1. Go to Vizier's copy of WDS 2. In the preferences tab (left column) choose 'unlimited' for max 3. On the following line choose something like '|-separated-values' (or any other format you prefer). If your aim is to load these into a spreadsheet, choosing '|-separated' works well. Experiment with different formats. If experimenting, set the 'max' value to something like 50 to prevent downloading the entire WDS each time. 4. I suggest you also click the J2000 box in the preferences table. This adds columns for decimal RA and Dec values to the table which I find to be more useful than the format supplied in the WDS catalogue (you also get that format as the last two columns of the table, so you can use either). 5. In the main table click as many checkboxes as you need (or choose them all and then get rid of them later once you've downloaded). 6. Hit submit and the results will be loaded into your browser window. 7. Check that they are all loaded (can take some minutes on a slow connection). The last line (if you follow step 4 above) should be: 359.97333|-31.20033|23599-3112|TDT4315| |1991|1991|248|248| 0.7| 0.70|11.54|11.90|-3119543 | | |23 59 53.60|-31 12 01.2 8. Copy and paste into a text editor, then delete all the non-data header lines. 9. Import the rest into a spreadsheet or whatever destination tool you have. There may be better ways to do this, but it works for me. This basic approach works for all the 1000s of useful catalogues that you can find at Vizier. cheers Martin
  4. EAA first light with new kit

    Congrats on the new setup! Great results -- the Pelican in particular. Does this mean you're going to pension off your 8" Quattro or will that get a turn on the mount at some point? As a Quattro owner I'd be interested in hearing your opinions on the difference between the two scopes. Having a permanent setup frees you from the constant collimation requirements of the fast reflector... When you say 'processed' images from the night, what processing did you do? cheers Martin
  5. Nice report. Nothing so organised from me but staring northwards at the region just below Cassiopeia I saw 4 in about 8 minutes just outside Bakewell in the Peak District at around 11pm. One was moderately bright but the others were very short-lived and quite faint. All were moving to the 'right' (eastwards). I may have missed some... I got the impression that this year the rate was quite high compared to previous ones I've managed to observe.
  6. Planetary nebula with visible central stars

    In case you want more, here's a list of planetaries organised by the magnitude of the central star. PNcstarMagI.pdf I've never looked at these ordered this way and there are some surprises. The PNs with brightest central stars are not necessarily the best known examples. Martin
  7. Maskelyne at Schiehallion

    It isn't often that my twin obsessions of Munro-bagging and astronomy collide, but they did yesterday at the base of Schiehallion, a 3553 ft Scottish mountain lying to the east of Rannoch Moor. Here I came across the following plaque to the work of Nevil Maskelyne, the Astronomer Royal, who used Newton's theory of gravity to estimate the density of the Earth. He did this by measuring the deflection of a plumb-line caused by the attractive force of Schiehallion. The deflection in turn was estimated by examining the distance of 77 stars from zenith on either side of the mountain, using the same zenith instrument used by Maskelyne during the 1761 transit of Venus. The entire method and the accuracy of the outcome is well-described in this commemorative article. Schiehallion is in some ways an exceptional mountain, standing some distance away from other mountain ranges (cleaner data), being steep on two sides (allowing the instrument to get close to the centre of mass on each side), and being almost symmetrical (easier to estimate its mass). As part of the need to precisely survey the mountain during the experiment, Charles Hutton was the first to use contour lines. On learning this I was rather hoping Charles Hutton was related to the father of geology, the Scot James Hutton, but although they were born within 10 years of each other I don't see any relationship. Here's an earlier shot of Schiehallion from a neighbouring mountain range to the west: In hillwalking terms it is a mountain of two parts, an easy well-made path up the first half through bracken and heather, followed suddenly on achieving the ridge by an extremely rocky landscape calling for stout boots, ending in a surprisingly bijou summit. If you do toil against gravity to reach the top, I can recommend rewarding yourself with a nice pint of Schiehallion IPA in a bar of the same name in the Macdonald Hotel in nearby Kinloch Rannoch! Martin
  8. Easier way to find deep sky objects.

    I also have a Star Adventurer and there are a couple of things you can do. One is to use a declination circle. There are several threads about this An alternative approach is to find a bright nearby star with roughly the same RA or Dec (I use a Rigel Quickfinder for this), then just move in RA or Dec until you hit your object. This approach works well if you have a deep enough atlas (for my 77mm refractor I find Interstellarium is not quite deep enough). This is my preferred approach as you can spot a lot of potentially interesting stuff on the way. The issue with a camera is that it is likely to show many more stars than an eyepiece, hence the need for a deepish atlas when using this approach. Good luck Martin
  9. Starlight Live controlling an SX USB Filter Wheel on a Mac

    Hi Jim Yes -- it works fine out of the box. SLL recognises the USB filter wheel as soon as you plug it in from my MacBook Air. On first use you can set up names for each filter position (e.g. R, G, B, Halpha, Darks etc), then use these to select the appropriate filter in the future. Its a great investment. Martin
  10. Back in December I posted about extreme runaway and hypervelocity stars, which are stars that have somehow reached a velocity that will allow them to escape the clutches of our galaxy one day. There I focusing on one called HVS 5 which is believed to have gained exit velocity by an encounter with the super-massive black hole at the centre of the galaxy. Out of the 20 or so HVS that have been identified, one stands out as different from the rest: HVS 2. This star is also known as US 708 due to its radial velocity of 708 km/s. At an overall velocity of 2.6 million miles per hour it is the fastest known star in the galaxy. Apart from this claim to fame (and somehow related to it!) HVS2 is special because it is thought not to have been caused by an encounter with the black hole, but instead is believed to be the result of a supernova explosion. Models predict that HVS 2 was a member of a binary star system, one of whose components exploded, sending it out at the enormous speed we now observe. HVS 2 is in Ursa Major, not far from galaxy UGC 5091. It is pretty faint at Vmag = 18.8 but is within reach of EAA techniques. You can find it at 9h 33' 21" +44 17 06. Here's a shot from earlier this year. I waited until this week to complete the story in order to capture another object that links to the HVS 2 story. The favoured ejection scenario for HVS 2 is actually a double-detonation of a white dwarf. The mechanism suggested is that helium is deposited on the white dwarf surface by accretion; this ignites, triggering the explosion of the white dwarf and leading to the ejection at hypervelocity of the helium star. Remarkably, a candidate system capable of such double detonation has been discovered. This is known as CD-30 11223 and lies in Centaurus at a declination of -30 degrees not too far from NGC 5494 (exact position: 14h 11' 16" -30 53 4). The star is quite bright (Vmag 11.9) and is shown on this single 30s shot from earlier this week: Admittedly, it is not much to look at, but consider a fascinating paragraph in the discovery article linked to above, pointing out that it is by far the nearest known SN Ia progenitor to Earth, and that when this star explodes (in an estimated 42 million years time), it will be visible from Earth with an apparent magnitude as high as -7.6, as bright as the 1006 supernovae, which itself was the 'brightest stellar event in recorded history'. One for future generations to look forward to. For more details, I recommend the web page of Warren Brown, who discovered the first HVS. It includes a link to his 2015 HVS article in the Annual Review of Astronomy and Astrophysics. Martin
  11. M51

    Thanks Jannis. I typically don't post-process, but on this occasion I did look at the effect of noise reduction in Nebulosity, but I didn't like the result...
  12. Skywatcher Quattro 8" f4 mounted in alt-az on AzEQ6 + Lodestar x2 mono camera. Due to field rotation I was forced into short exposures on this one (24x10s). This is unprocessed (captured at the scope using StarlightLive). There is some noise in there (probably read noise) but I left it in to show what is possible without processing if you don't mind that kind of thing! Martin
  13. M82 in RGB, Starlight Live

    I've found that I need much more RGB than L, plus increasing saturation helps. I've more or less given up the LRGB experiment for the moment because I think it takes too much time and takes away from the live element. But I'm a firm believer that it is possible in principle to do it live with the appropriate algorithms that treat luminosity and chrominance separately. For certain applications like the H-alpha+L combination I think it works well, although again quite a lot of H-alpha is needed to overcome the dominance of the L signal.... You could experiment with laying a base of a small amount of luminance and then add RGB.
  14. Flat galaxies in Virgo

    Excellent clear night yesterday even though it didn't get fully dark until 11.30 (pretty tired today at work...). The SQM reading reached 20.5, which is unusual for where I live. I had a long session looking at galaxies, galaxy clusters, globulars, an open cluster and Tabby's Star. Here are a few flat galaxies (all members of the Flat Galaxy Catalogue, FGC) in Virgo. NGC 4437 = FGC 1455 is quite bright and bears some resemblance to the Whale but without the Pup NGC 4430 = FGC 1423 is quite a bit fainter. With time the core became visible as a brightish spot NGC 5170 = FGC 1626 is my favourite of the lot, not just because of the almost perfect shape and bright core, but because of the 'ear-ring' like asterism to the lower right. Usual kit: alt-az mounted Quattro 8" f4 Newt, Lodestar X2 mono, StarlightLive software Thanks for looking Martin
  15. M82 in RGB, Starlight Live

    Welcome to the club! It will be interesting to hear your experience with RGB, esp. with respect to the nonlinear modes. Do you have an electronic filter wheel? Luminance can be overwhelming, its true. Laying down a luminance base first then adding quite a lot of colour seems to work, as does turning the saturation up (although for best colour in RGB mode I leave the saturation and hue controls alone). Martin