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19 Comments

  1. I would be interested to join the project team. My observatory is located at 175 E, 38 S. The instrument is an automated 0.4m RC with an SBIG STXL6303 camera equipped with Astrodon Johnson and Sloan photmetric filters. The data reduction software is Mira ProX64. Recent measurements of some RR Lyrae variables shows the measurement error less than 10 mmag.

    It looks like I might be able to fill a void between the observatories in Chile and those in Australia, especially for the far south stars which the U.S. western observatories may not be able to reach. Let me know if you want me to observe at specific times to provide the best coverage with some overlap for comparison.

    Fortunately, tonight (17/06/2017 NZ) looks to be clear so I will make some first observations of the target stars using V filter and continuous 60 second integration times, measured over a few hours. I didn’t see any exacting requirements for the data acquisition process, let me know if I need to make changes.

    Looking forward to working with you all,

    Craig Young
    Crystal Lake Observatory
    New Zealand

  2. Hi Craig,
    Great to hear that you are interested in joining the campaign and your contributions will be greatly appreciated. Your observation strategy looks fine to me and as you say you have a good location to be observing from in the South which will greatly help with our coverage of observations.
    If you have any questions please don’t hesitate to post to our forums on the web-site.

    best regards

    John Strachan
    Queen Mary University of London

  3. HI,

    I have a remote site in Chile (MPC G39) andfollow many stars nearly nightly.I started the first test runs last night and see that the stars are very bright and not at the position give in the J2000 coordinartes due to their proper motion.
    I guess way Craig is observing with 60s exposure is far too long for his equipment (similar to mine).

    I normally cycle serveral stars with time series and will see how I can add yours to my program.
    SO my cadence will be about every 5min or so with exposures in V band of 15s for V2500 Oph, I wonder why you have chosen the comp stars so dim as this will have as consequence that the uncertainty will increase. In my case most of the uncertainty comes from the comp stars (0.013 mag). With better comp stars which are in my field of view (57×57 arcsec^2) I see several brighter star I could use as comps.
    The same is probably true for the GJ729 which I also obsvered. Both stars are observed in snapshot mode.

    Regards,

    F.-J. (Josch) Hambsch

        • Hi Josch, have checked with some of the professional observers working on the campaign and we should stick to the existing comparison stars as 1) they are being used by all the professional observatories 2) they are in the 21×21 Field of view and 3) they have been tested for stability.

          John

    • Hi Josch, thanks for your message. You may be right that the 1 minute integration time may be too long. As no doubt you are aware ideal integration time depends on a number of factors: instrumentation used, seeing and transparency conditions and light pollution, star magnitude and airmass. However I would expect when taking exposures your prime guide for integration time is the number of counts recorded by the CCD. Most CCDs have a 64k limit on the number of counts they can record. And a reasonable rule of thumb is that you can go up to 2/3 that number before starting to have potential non-linearity problems with the CCD.
      I have chosen the number 1 comparison star that is being used by the professional observatories. I will have a discussion about your comment to use brighter stars and get back to you. In the meantime please continue with the. Urgent comparison stars . Again thanks very much for your time and contributions.
      Best regards
      John Strachan

    • Hi Josch,

      Not sure if this is the best thread to discuss the technical aspects of our acquisition methodology but I’ll keep going and the moderator can move us if he thinks it is best.

      I also did some test measurements last night, starting with Proxima Centauri, but got clouded out before I could try the other stars. With a 60 second exposure I got a raw max ADU of 10,469 for the target, 27,387 for the comparison (C1) and 23,187 for the check star (UCAC4 137:115579). So I think 60 seconds will be okay.

      I would like to propose the following comp and check stars:

      Comp: UCAC4 137:115786, I believe this is C1 on the finder chart as proposed. It has an APASS B: 10.574 and V: 10.311 (B-V: 0.263).

      Check: UCAC4 137:115579. It has an APASS B: 10.631 and V:10.491 (B-V: 0.140).

      The check is about the same color as the comp and both have an almost 0 value which means we can ignore the V color transformation?

      Want to get these sorted out before submitting the data.

      Craig

      • Just noticed that Proxima has a color index of 1.82, which means I will need to apply a color transform to get a standard V.

  4. I just measured V1216 Sgr as well and I get 4 mmag uncertainty due to the fact that the comp stars are much closer in brightness to the variable.

    Josch

  5. I just found the campaign. May be we can join with Planewave CDK20 telescope located at 22 16 25.7E +48 56 05.7 N, operated by P.J. Safarik University Kosice. The half meter telescope is equipped with Moravian Instruments G4-16000 camera and B V Rc Ic filters. We can observe only Barnard star. As I understand you need the coverage as dense as possible in V filter. Am I right?
    Pavol A. Dubovsky
    Astronomical Observatory on Kolonica Saddle
    Slovakia

    • Hi Pavol, we would be delighted for you to join us. You are correct that dense coverage with the V filter is what is required.

      best regards

      John Strachan
      Queen Mary University of London

  6. Hi,

    I have sent my data to the AAVSO database for both V2500 Oph and V1216 Sgr. I took time series during the past nights.
    Unfortunately in the AAVSOdatabse we have someone submitting H-alpha data with negative magnitudes (is the star really that bright in H-a?) and someone else which shows a larage variation in V band, which I can not reproduce.

    Josch

    • I have also sent data to AAVSO on V2500 Oph and V1216 Sgr from 6/23. Josch, my magnitudes(submitted as HBB) are comparable to your data from that evening. I did see someone with large variations in V and I reported this data as discrepant to AAVSO. I will continue to monitor these stars as frequently as I can but I live in Florida and the summer weather pattern doesn’t allow very many clear nights.

  7. Concerning the comp stars I am pretty sure the othes will also have the issue of large uncertainties intrpduced due to the large magnitude difference of comps and variable.
    Josch

      • Hi Barbara,

        did you use the comp stars as recommended?
        IN my case they introduce a too large error in the error propagation.
        Hence since my FOV is large I used different ones. But if you tell that your results are close to mine then the comps should not matter, which is good.

        Josch

          • Hi Barbara,

            I see a drop in your data from June 23, which I do not see in mine.
            Would you be willing to share your AAVSO file with me? Based on the LC of AAVSO we have obsrved at similar times.
            Do you know my e-mail address?
            Thanks,

            Josch

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