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Re: [vsx-dis] Suitable filters to use

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  • arne
    Hi David, Johnson V is almost always your first choice for photometric filters, as the next star you observe may be a different color and V is very generic.
    Message 1 of 5 , Jun 12, 2013
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      Hi David,
      Johnson V is almost always your first choice for photometric filters, as the
      next star you observe may be a different color and V is very generic. You may
      have to expose longer for your current red star, but you do that for deep-sky
      images anyway and scientific photometry always takes about the same amount of
      on-sky time. If you only want to image very red stars, your best filter is
      Cousins Ic, which is a very red filter (redder than Halpha).
      Arne

      On 6/12/13 11:52 AM, David Kennedy wrote:
      >
      >
      > Hi everyone,
      > thank you for replying to my questions. Most of my data for NSV 10242 is with
      > a Ha 12nm astronomik filter, with blue or green filters the star is hardly
      > visible. For an extreme red star which photometric filter would be most useful
      > for making observations?.
      > Thanks,
      > David
      > *From:* Patrick Wils <mailto:patrickwils@...>
      > *Sent:* Tuesday, June 11, 2013 6:36 AM
      > *To:* vsx-dis@yahoogroups.com <mailto:vsx-dis@yahoogroups.com>
      > *Subject:* Re: [vsx-dis] Suitable filters to use
      >
      > Hi David,
      >
      > LRGB filters are difficult to transform to the standard photometric system,
      > especially for red stars such as this one. It would be better to use e.g.
      > Johnson-Cousins filters.
      >
      > As this forum has been inactive and most questions are dealt with on one of the
      > AAVSO forums <http://www.aavso.org/forum>, I suggest to ask your questions
      > there. There are many more experienced photometrists available to give you more
      > complete advice.
      >
      > Patrick
      >
      > ________________________________
      > From: David Kennedy <mailto:dken%40live.com.au>
      > To: mailto:vsx-dis%40yahoogroups.com
      > Sent: Sunday, June 9, 2013 3:07 PM
      > Subject: [vsx-dis] Suitable filters to use
      >
      > Hello everyone,
      >
      > I’m a new member to the group, joining after noticing a possible variable
      > star in my CCD images of the nebula NGC6559. Through the VSX website I’ve
      > found out the star is a suspected variable listed as NSV 10242. I’ve made
      > observations of the star on 3 nights over the past 3.5 weeks and using MaxIm DL
      > have measured that it’s decreasing in brightness. However, I’ve been
      > collecting data using the filters I use for imaging (LRGB and Ha
      > Astronomik filters) and I would like to know if useful photometric data can been
      > gained with these or do I need to use different filters instead? Can
      > anyone help?
      >
      > Thanks,
      >
      > David Kennedy
      >
      >
      >
      >
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