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Dave Smith

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About Dave Smith

  • Rank
    White Dwarf

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  • Website URL
    http://astrosnaps.co.uk

Profile Information

  • Gender
    Male
  • Location
    Maldon, Essex
  1. In spite of the weather being largely dominated by high pressure last night was the first clear night since the beginning of December. This is a fascinating variable star that has more than one period of oscillation. The two (or more) periods sort of beat together causing the variation in amplitude. The main period is just under two hours. This is one I would like to do again and if possible for a longer time. Dave PS The tutorial is progressing.
  2. Thank you Giorgio. With all the Christmas, New Year and Family activities it had slipped my mind that I was writing a tutorial so thanks for the reminder. I will attempt to answer your questions. Your setup is certainly ok for variable stars. Many reports I have seen are from a telephoto lens. The size of the scope may restrict how dim the stars can be, which is why I did upgrade my scope. I was able to detect an exoplanet with my 90mm refractor so it is worth a try with 60mm. When I did 643 45s exposures there was no intentional interval between each exposure only the inevitable delay while the image downloads from the camera. Whether you have an interval orr not depends on the time scale of the variation. With some stars the period of variation can vary from an hour to years. It is essential to use bias, flats and darks as in astro imaging. I usually have around 50 of each. AstroImageJ has a feature that enables a sample image to be examined to ensure that stars are not saturated. With comparative photometry, as long as the target star(s) and comparison stars are in the same field of view then no correction is needed for altitude or even light pollution (e.g. moonlight). Hope that helps Dave
  3. Dave Smith

    Who needs meridian flips anyway?

    I would agree there is no need to be paranoid about a meridian flip. The only danger to look out for is the scope crashing into the mount. Dave
  4. Thanks Helen. I see no reason why I can't write a short tutorial on this. I am giving a talk on variable stars to my club early next year and so preparing for that and a tutorial should go hand in hand. It may take some time (weeks) so I will keep you informed when I have made some progress. Dave
  5. Thanks Francis. I did get a bit bored with imaging in particular because it was not really of much use scientifically. Doing variable stars does appeal to my physics background and is actually useful to the professionals. I now regularly get emails from the aavso to say that a professional or a student has made use of my data. Dave
  6. Thanks Michael. You can do this without any special equipment. The software needed is free although I find SGPro invaluable to get the star right in the middle of the FOV. Almost any scope can be used. Dave
  7. Eclipsing binary star AD Andromeda. Multiple 45s exposures collected with SGPro and processed with AstroImageJ. The noisy bit at the end is due to the star approaching the horizon. Total of 643 readings! Dave
  8. This is an excellent piece of work. How are you deducing the magnitude? I can strongly recommend the free software AstroImageJ It is important to use flats otherwise any vignetting or dust bunnies will badly effect results. There is much help and advice on the BAA variable star section web page http://www.britastro.org/vss/ and also suggestions for target variable stars. Dave
  9. Thanks JOC. I have recently upgraded my kit but most of the variable star work I have done has been with a 90mm refractor and CCD camera. In order to get to fainter stars I am now using an 11" EdgeHD scope. This star varies from around mag 13 to 13.6. You are very welcome to visit anytime. Email on it's way. Dave
  10. No that is not right. The best explanation I have found is here https://www.aavso.org/vsots_delsct Especially half way down the page on "What makes them tick?" Dave
  11. Hi Alan The time scale is in days. So the period for this star is just over 2.5 hours. The change in brightness is due to the expansion and contraction of the star. Dave
  12. Unexpectedly clear last night so had a go at a different HADS star. The graph here is the output from AstroImageJ that I now use for the photometry. The horizontal lines are the 3 comparison stars. Dave
  13. Yes it's period is 3.20178 hours. It is the period that is being studied, I believe. There is the possibility of multiple periods. Dave
  14. This is a HADS (High Amplitude Delta Scutii) star the I am observing monthly for an astronomer in Belgium who is doing a long term project on HADS stars. This one is multiple 2 min exposures and analysed with free software AstroImageJ. Dave
  15. Dave Smith

    Exoplanat WASP-2b

    Hi Jim Here are a few links you may find useful. https://www.astro.louisville.edu/software/astroimagej/guide/AstroImageJ_User_Guide.pdf Richard Lee's tutorial on AstroImageJ https://britastro.org/sites/default/files/Tutorial_AIJ_Photometry_v2.05.pdf BAA VSS website where there are many useful links http://www.britastro.org/vss/ Dave
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