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Re: [Stellarvue] NGC 2903 by SV130

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  • Craig Temple
    Hi Robert, We have no experience with the ST-i, but we ve had our fair share of guiding difficulties :-) Sometimes (at least for us) longer guide exposures
    Message 1 of 4 , Apr 30 7:08 AM
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      Hi Robert,
      We have no experience with the ST-i, but we've had our fair share of
      guiding difficulties :-) Sometimes (at least for us) longer guide
      exposures can help, as it will smooth out the guiding. Do you use the
      graph in PHD?
      - C&T

      On 4/27/2012 6:20 PM, Robert wrote:
      >
      > Been a while since I have posted anything but finally the weather got
      > more friendly.
      >
      > I wanted to test my new SBIG ST-i mono as an OAG guide camera. There
      > has been growing pains. I had no problems obtaining guide stars and
      > getting a good focus thru the SV130. However I did keep getting "Star
      > Saturated" and "Low SNR" messages while using PHD. Never had these
      > problems using an external guide scope and an SSAG. Finally ended up
      > using a 5 second shutter speed on the ST-i. I had never gone higher
      > than 1 second with the external guide scope. I also changed mounts
      > without improvement.
      >
      > Anyway I will have to refine my technique to improve the OAG
      > experience as the guiding was less than stellar for the 3 nights. I
      > had many unusable frames and the guiding was pretty erratic. I am sure
      > some of the problems were due to me constantly changing guide
      > parameters. The sky conditions may have been part of the problems as
      > it was the first night after some strong storms.
      >
      > Here is a link to the final image:
      > http://www.flickr.com/photos/14381217@N03/6970942630/in/photostream
      >
      > Anybody else have experience using the ST-i with or without an OAG?
      >
      > Clear skies to all.
      >
      > Robert Collins
      > http://www.flickr.com/photos/14381217@N03/
      > Yuba City, CA
      >
      >


      [Non-text portions of this message have been removed]
    • Robert
      Hi C&T, many thanks for answering. I do use the graphing function of PHD and also study the log. Much information there too. Last night I used the ST-i with my
      Message 2 of 4 , Apr 30 12:34 PM
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        Hi C&T, many thanks for answering.

        I do use the graphing function of PHD and also study the log. Much information there too.

        Last night I used the ST-i with my 50mm (F3.5) guide scope and it performed very well giving me one of the smoothest graphs I have ever had. My RMS was 08. I received no PHD messages and my exposure was 1 second. My OAG problems are not with the ST-i and are likely to be technique/PHD-settings oriented.

        While using the OAG last week I was surprised that I immediately got a "Star Saturated" message and a couple of guide frames later received the "Low SNR" message. After some thought this seems easily possible as the two refer to two different things. With the saturated condion PHD can't find the center of the guide star. And, using the SV130 (F7) would certainly require more exposure than the F3.5 guide scope. 3, 4 or 5 seconds is probably reasonable.

        Looking at the log revealed star mass to be less than 2,000. I normally experience between 30,000 and 125,000 while using a guide scope (although last night I had below 5,000 with the guide scope and ST-i).

        I have to change my technique with the OAG. I need to calibrate the guide star after I do a final focus. Last time I used the OAG I calibrated before final focus. The change in focus in the guide star would probably affect the validity of the calibration. I also need to wait for the skies to stabilize before trying again.

        Clear skies.

        Robert Collins
        http://www.flickr.com/photos/14381217@N03/
        Yuba City, CA

        --- In Stellarvue@yahoogroups.com, Craig Temple <ctastroimager@...> wrote:
        >
        > Hi Robert,
        > We have no experience with the ST-i, but we've had our fair share of
        > guiding difficulties :-) Sometimes (at least for us) longer guide
        > exposures can help, as it will smooth out the guiding. Do you use the
        > graph in PHD?
        > - C&T
        >
        > On 4/27/2012 6:20 PM, Robert wrote:
        > >
        > > Been a while since I have posted anything but finally the weather got
        > > more friendly.
        > >
        > > I wanted to test my new SBIG ST-i mono as an OAG guide camera. There
        > > has been growing pains. I had no problems obtaining guide stars and
        > > getting a good focus thru the SV130. However I did keep getting "Star
        > > Saturated" and "Low SNR" messages while using PHD. Never had these
        > > problems using an external guide scope and an SSAG. Finally ended up
        > > using a 5 second shutter speed on the ST-i. I had never gone higher
        > > than 1 second with the external guide scope. I also changed mounts
        > > without improvement.
        > >
        > > Anyway I will have to refine my technique to improve the OAG
        > > experience as the guiding was less than stellar for the 3 nights. I
        > > had many unusable frames and the guiding was pretty erratic. I am sure
        > > some of the problems were due to me constantly changing guide
        > > parameters. The sky conditions may have been part of the problems as
        > > it was the first night after some strong storms.
        > >
        > > Here is a link to the final image:
        > > http://www.flickr.com/photos/14381217@N03/6970942630/in/photostream
        > >
        > > Anybody else have experience using the ST-i with or without an OAG?
        > >
        > > Clear skies to all.
        > >
        > > Robert Collins
        > > http://www.flickr.com/photos/14381217@N03/
        > > Yuba City, CA
        > >
        > >
        >
        >
        > [Non-text portions of this message have been removed]
        >
      • vic@stellarvue.com
        Nice Rob. Guiding and other issues seem to be part of the never ending process. Despite all of this, you have an awesome image there! Congrats Vic Maris
        Message 3 of 4 , May 2, 2012
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          Nice Rob. Guiding and other issues seem to be part of the never ending process. Despite all of this, you have an awesome image there! Congrats

          Vic Maris

          --- In Stellarvue@yahoogroups.com, "Robert" <collirob@...> wrote:
          >
          > Been a while since I have posted anything but finally the weather got more friendly.
          >
          > I wanted to test my new SBIG ST-i mono as an OAG guide camera. There has been growing pains. I had no problems obtaining guide stars and getting a good focus thru the SV130. However I did keep getting "Star Saturated" and "Low SNR" messages while using PHD. Never had these problems using an external guide scope and an SSAG. Finally ended up using a 5 second shutter speed on the ST-i. I had never gone higher than 1 second with the external guide scope. I also changed mounts without improvement.
          >
          > Anyway I will have to refine my technique to improve the OAG experience as the guiding was less than stellar for the 3 nights. I had many unusable frames and the guiding was pretty erratic. I am sure some of the problems were due to me constantly changing guide parameters. The sky conditions may have been part of the problems as it was the first night after some strong storms.
          >
          > Here is a link to the final image:
          > http://www.flickr.com/photos/14381217@N03/6970942630/in/photostream
          >
          > Anybody else have experience using the ST-i with or without an OAG?
          >
          > Clear skies to all.
          >
          > Robert Collins
          > http://www.flickr.com/photos/14381217@N03/
          > Yuba City, CA
          >
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