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RE: [home_dome_users] Placement of OTA

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  • Dan Griffing
    Yes, I offset my pier. The Declination axis is approximately centered in my PD10 but above the center of curvature. Otherwise people would have to sit or lie
    Message 1 of 7 , Feb 5, 2010
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      Yes, I offset my pier.  The Declination axis is approximately centered in my PD10 but above the center of curvature.  Otherwise people would have to sit or lie on the floor to have a star party.
       
      Dan Griffing
      Darwin Observatory
      Belgrade, MT
      -----Original Message-----
      From: home_dome_users@yahoogroups.com [mailto:home_dome_users@yahoogroups.com]On Behalf Of Michael Cook
      Sent: Thursday, February 04, 2010 6:31 PM
      To: homedome
      Subject: [home_dome_users] Placement of OTA

       

      For owners of fork-mounted scopes, did you off-set your pier within the dome so that the OTA is centered in the dome when pointed at the zenith?  I know you can input dome off-sets in DDW to account for OTA placement, but I thought I would check with the users for some feedback on this.  I'm replacing my scope and mount and I have the opportunity to move things.

      Thanks.

      Mike Cook
      http://www.newcastl eobservatory. com

    • Michael Cook
      Hi Bruce, Thanks for your perspective. I know all too well how much fiddling is required with the geometry settings. It didn t take me long to get the dome
      Message 2 of 7 , Feb 5, 2010
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        Hi Bruce,

        Thanks for your perspective.  I know all too well how much fiddling is required with the geometry settings. It didn't take me long to get the dome slaving to the scope with the dome slit pretty much centered wherever the scope points.  I found that systematically tweaking the values by an inch at a time was the best approach.  I don't think I'll be going to a GEM any time soon.  I'm expecting deliver of a Mathis fork mount this month.  Due to the length of the fork arms of this mount, the OTA would shift north, and if pointed at the zenith, the view for the OTA would not clear the top of the dome.  I've seen examples of fork mounts placed in domes so that the OTA is centered in the dome: e.g.:
        http://www.starkey.ws/new_observatory.html
        http://www.imagingtheheavens.com/Obs/JMSMO/jmsmo.html
        http://www.company7.com/mccmo/ashrebspec.html

        The other advantage of doing this is that I would get more elbow room behind (north of) the pier.

        Mike



        From: waddington50 <bw_msg01@...>
        To: home_dome_users@yahoogroups.com
        Sent: Fri, February 5, 2010 12:56:47 AM
        Subject: [home_dome_users] Re: Placement of OTA

         

        Hi Mike. I used a 10-inch fork-mounted SCT in the dome for over two years, and the pier was centered, not the OTA. I had no problems with this arrangement, nor did I expect any. The only implication is that the dome will be open on the north side more often than not. It's also entirely possible that you will change to a GEM sometime down the road, so I think you're better off having the pier centered. If you haven't fiddled much with the various geometry settings, you may be surprised by how sensitive they are in terms of getting the dome opening aligned with the scope. I recommend just being patient, making small changes, and being methodical in the fine-tuning process..

        Good luck.

        Bruce

        --- In home_dome_users@ yahoogroups. com, Michael Cook <michaeljcook@ ...> wrote:
        >
        > For owners of fork-mounted scopes, did you off-set your pier within the dome so that the OTA is centered in the dome when pointed at the zenith? I know you can input dome off-sets in DDW to account for OTA placement, but I thought I would check with the users for some feedback on this. I'm replacing my scope and mount and I have the opportunity to move things.
        >
        > Thanks.
        >
        > Mike Cook
        > http://www.newcastl eobservatory. com
        >

      • Rick Wiggins
        Hi Mike, I think the bottom line the application. I know you to be a serious and well thought out astronomer, so I am guessing here that you know what you want
        Message 3 of 7 , Feb 5, 2010
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          Hi Mike,

          I think the bottom line the application. I know you to be a serious and well thought out astronomer, so I am guessing here that you know what you want to do.

          If you want to ultimately go to a GEM design, then center the pier as it will give you the best performance.

          If you know you are going to be using a fork mount, then center the OTA as in the examples you listed.

          You can always change it and you can do both.

          The JMSM setup for the last two years has been a centered pier with my 14.5 inch RC on a Paramount. Mike built the Pier Footing to accomodate a centrally located pier or an offset mounted fork mount.

          I recommend centering the OTA while accomodating future changes if possible. I think you will have frustration trying to operate a fork mount that does not have the OTA centered if you are using the DDW setup. Non-centered setups just multiply any errors in the calculated offsets.

          I have had very good success operating my StarCruiser Observatory with a centered AP GEM mount in the DDW dome. I use actual and measured offsets (no tweaking) and they seem to work well.

          Thanks, Rick

           




           

          -----Original Message-----
          From: Michael Cook
          Sent: Feb 5, 2010 1:14 PM
          To: home_dome_users@yahoogroups.com
          Subject: Re: [home_dome_users] Re: Placement of OTA

           

          Hi Bruce,

          Thanks for your perspective.  I know all too well how much fiddling is required with the geometry settings. It didn't take me long to get the dome slaving to the scope with the dome slit pretty much centered wherever the scope points.  I found that systematically tweaking the values by an inch at a time was the best approach.  I don't think I'll be going to a GEM any time soon.  I'm expecting deliver of a Mathis fork mount this month.  Due to the length of the fork arms of this mount, the OTA would shift north, and if pointed at the zenith, the view for the OTA would not clear the top of the dome.  I've seen examples of fork mounts placed in domes so that the OTA is centered in the dome: e.g.:
          http://www.starkey. ws/new_observato ry.html
          http://www.imagingt heheavens. com/Obs/JMSMO/ jmsmo.html
          http://www.company7 .com/mccmo/ ashrebspec. html

          The other advantage of doing this is that I would get more elbow room behind (north of) the pier.

          Mike



          From: waddington50 <bw_msg01@earthlink. net>
          To: home_dome_users@ yahoogroups. com
          Sent: Fri, February 5, 2010 12:56:47 AM
          Subject: [home_dome_users] Re: Placement of OTA

           

          Hi Mike. I used a 10-inch fork-mounted SCT in the dome for over two years, and the pier was centered, not the OTA. I had no problems with this arrangement, nor did I expect any. The only implication is that the dome will be open on the north side more often than not. It's also entirely possible that you will change to a GEM sometime down the road, so I think you're better off having the pier centered. If you haven't fiddled much with the various geometry settings, you may be surprised by how sensitive they are in terms of getting the dome opening aligned with the scope. I recommend just being patient, making small changes, and being methodical in the fine-tuning process..

          Good luck.

          Bruce

          --- In home_dome_users@ yahoogroups. com, Michael Cook <michaeljcook@ ...> wrote:
          >
          > For owners of fork-mounted scopes, did you off-set your pier within the dome so that the OTA is centered in the dome when pointed at the zenith? I know you can input dome off-sets in DDW to account for OTA placement, but I thought I would check with the users for some feedback on this. I'm replacing my scope and mount and I have the opportunity to move things.
          >
          > Thanks.
          >
          > Mike Cook
          > http://www.newcastl eobservatory. com
          >

        • Michael Cook
          Hi Rick, Thanks. I appreciate your thoughts and sharing your experience. It s always nice to hang an idea out here and get some feedback. Besides minimizing
          Message 4 of 7 , Feb 5, 2010
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            Hi Rick,

            Thanks.  I appreciate your thoughts and sharing your experience.  It's always nice to hang an idea out here and get some feedback.  Besides minimizing error prone calculated off-sets, I like the idea of making it more roomy north of the pier.  Accommodating that may seem straightforward to me, only to find out I've introduced another side-effect.  But it looks like it will be fine. Thanks for the confirmation.

            Mike



            From: Rick Wiggins <rickwiggins@...>
            To: home_dome_users@yahoogroups.com
            Sent: Fri, February 5, 2010 5:28:06 PM
            Subject: Re: [home_dome_users] Re: Placement of OTA

             

            Hi Mike,

            I think the bottom line the application. I know you to be a serious and well thought out astronomer, so I am guessing here that you know what you want to do.

            If you want to ultimately go to a GEM design, then center the pier as it will give you the best performance.

            If you know you are going to be using a fork mount, then center the OTA as in the examples you listed.

            You can always change it and you can do both.

            The JMSM setup for the last two years has been a centered pier with my 14.5 inch RC on a Paramount. Mike built the Pier Footing to accomodate a centrally located pier or an offset mounted fork mount.

            I recommend centering the OTA while accomodating future changes if possible. I think you will have frustration trying to operate a fork mount that does not have the OTA centered if you are using the DDW setup. Non-centered setups just multiply any errors in the calculated offsets.

            I have had very good success operating my StarCruiser Observatory with a centered AP GEM mount in the DDW dome. I use actual and measured offsets (no tweaking) and they seem to work well.

            Thanks, Rick

             




             

            -----Original Message-----
            From: Michael Cook
            Sent: Feb 5, 2010 1:14 PM
            To: home_dome_users@ yahoogroups. com
            Subject: Re: [home_dome_users] Re: Placement of OTA

             

            Hi Bruce,

            Thanks for your perspective.  I know all too well how much fiddling is required with the geometry settings. It didn't take me long to get the dome slaving to the scope with the dome slit pretty much centered wherever the scope points.  I found that systematically tweaking the values by an inch at a time was the best approach.  I don't think I'll be going to a GEM any time soon.  I'm expecting deliver of a Mathis fork mount this month.  Due to the length of the fork arms of this mount, the OTA would shift north, and if pointed at the zenith, the view for the OTA would not clear the top of the dome.  I've seen examples of fork mounts placed in domes so that the OTA is centered in the dome: e.g.:
            http://www.starkey. ws/new_observato ry.html
            http://www.imagingt heheavens. com/Obs/JMSMO/ jmsmo.html
            http://www.company7 .com/mccmo/ ashrebspec. html

            The other advantage of doing this is that I would get more elbow room behind (north of) the pier.

            Mike



            From: waddington50 <bw_msg01@earthlink. net>
            To: home_dome_users@ yahoogroups. com
            Sent: Fri, February 5, 2010 12:56:47 AM
            Subject: [home_dome_users] Re: Placement of OTA

             

            Hi Mike. I used a 10-inch fork-mounted SCT in the dome for over two years, and the pier was centered, not the OTA. I had no problems with this arrangement, nor did I expect any. The only implication is that the dome will be open on the north side more often than not. It's also entirely possible that you will change to a GEM sometime down the road, so I think you're better off having the pier centered. If you haven't fiddled much with the various geometry settings, you may be surprised by how sensitive they are in terms of getting the dome opening aligned with the scope. I recommend just being patient, making small changes, and being methodical in the fine-tuning process..

            Good luck.

            Bruce

            --- In home_dome_users@ yahoogroups. com, Michael Cook <michaeljcook@ ...> wrote:
            >
            > For owners of fork-mounted scopes, did you off-set your pier within the dome so that the OTA is centered in the dome when pointed at the zenith? I know you can input dome off-sets in DDW to account for OTA placement, but I thought I would check with the users for some feedback on this. I'm replacing my scope and mount and I have the opportunity to move things.
            >
            > Thanks.
            >
            > Mike Cook
            > http://www.newcastl eobservatory. com
            >

          • Michael H
            Hi Mike, I centered my 10ft concrete pier in the dome when starting out with my fork mounted 10 LX200. I had a custom steel pier that offset the fork to the
            Message 5 of 7 , Feb 8, 2010
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              Hi Mike,
              I centered my 10ft concrete pier in the dome when starting out with my fork mounted 10" LX200. I had a custom steel pier that offset the fork to the south. This worked very well for two years:

              http://www.horizontalheavens.com/InDomeOffsetPier2.jpg

              In 2005, I moved up to a MI250 GEM and replaced the original offset pier with a new straight (centered) pier:

              http://www.horizontalheavens.com/Trio-NP127-TMB80-LX200R.jpg
              http://www.horizontalheavens.com/PierWiresHanging.jpg

              FWIW, I did originally plan for the eventual use of a GEM mount, but now having had both over the years I have had second thoughts. I now feel that a high quality fork mount would be superior in a 10ft dome (something like a MI500 or MI750 fork. That of course would require a permenant pier offset with no "going back" and would have also limited OTA choices. Overall, I think GEMs are more flexible for our needs and desires as they both change over time.
              Michael

              --- In home_dome_users@yahoogroups.com, Michael Cook <michaeljcook@...> wrote:
              >
              > Hi Rick,
              >
              > Thanks. I appreciate your thoughts and sharing your experience. It's always nice to hang an idea out here and get some feedback. Besides minimizing error prone calculated off-sets, I like the idea of making it more roomy north of the pier. Accommodating that may seem straightforward to me, only to find out I've introduced another side-effect. But it looks like it will be fine. Thanks for the confirmation.
              >
              > Mike
              >
              >
              >
              >
              >
              > ________________________________
              > From: Rick Wiggins <rickwiggins@...>
              > To: home_dome_users@yahoogroups.com
              > Sent: Fri, February 5, 2010 5:28:06 PM
              > Subject: Re: [home_dome_users] Re: Placement of OTA
              >
              >
              > Hi Mike,
              > I think the bottom line the application. I know you to be a serious and well thought out astronomer, so I am guessing here that you know what you want to do.
              > If you want to ultimately go to a GEM design, then center the pier as it will give you the best performance.
              > If you know you are going to be using a fork mount, then center the OTA as in the examples you listed.
              > You can always change it and you can do both.
              > The JMSM setup for the last two years has been a centered pier with my 14.5 inch RC on a Paramount. Mike built the Pier Footing to accomodate a centrally located pier or an offset mounted fork mount.
              > I recommend centering the OTA while accomodating future changes if possible. I think you will have frustration trying to operate a fork mount that does not have the OTA centered if you are using the DDW setup. Non-centered setups just multiply any errors in the calculated offsets.
              > I have had very good success operating my StarCruiser Observatory with a centered AP GEM mount in the DDW dome. I use actual and measured offsets (no tweaking) and they seem to work well.
              > Thanks, Rick
              >
              >
              >
              >
              >
              > -----Original Message-----
              > >From: Michael Cook
              > >Sent: Feb 5, 2010 1:14 PM
              > >To: home_dome_users@ yahoogroups. com
              > >Subject: Re: [home_dome_users] Re: Placement of OTA
              > >
              > >
              > >Hi Bruce,
              > >
              > >Thanks for your perspective. I know all too well how much fiddling is required with the geometry settings. It didn't take me long to get the dome slaving to the scope with the dome slit pretty much centered wherever the scope points. I found that systematically tweaking the values by an inch at a time was the best approach. I don't think I'll be going to a GEM any time soon. I'm expecting deliver of a Mathis fork mount this month. Due to the length of the fork arms of this mount, the OTA would shift north, and if pointed at the zenith, the view for the OTA would not clear the top of the dome. I've seen examples of fork mounts placed in domes so that the OTA is centered in the dome: e.g.:
              > >http://www.starkey ws/new_observato ry.html
              > >http://www.imagingt heheavens. com/Obs/JMSMO/ jmsmo.html
              > >http://www.company7 .com/mccmo/ ashrebspec. html
              > >
              > >The other advantage of doing this is that I would get more elbow room behind (north of) the pier.
              > >
              > >Mike
              > >
              > >
              > >
              > >
              > ________________________________
              > From: waddington50 <bw_msg01@earthlink. net>
              > >To: home_dome_users@ yahoogroups. com
              > >Sent: Fri, February 5, 2010 12:56:47 AM
              > >Subject: [home_dome_users] Re: Placement of OTA
              > >
              > >
              > >Hi Mike. I used a 10-inch fork-mounted SCT in the dome for over two years, and the pier was centered, not the OTA. I had no problems with this arrangement, nor did I expect any. The only implication is that the dome will be open on the north side more often than not. It's also entirely possible that you will change to a GEM sometime down the road, so I think you're better off having the pier centered. If you haven't fiddled much with the various geometry settings, you may be surprised by how sensitive they are in terms of getting the dome opening aligned with the scope. I recommend just being patient, making small changes, and being methodical in the fine-tuning process..
              > >
              > >Good luck.
              > >
              > >Bruce
              > >
              > >--- In home_dome_users@ yahoogroups. com, Michael Cook <michaeljcook@ ...> wrote:
              > >>
              > >> For owners of fork-mounted scopes, did you off-set your pier within the dome so that the OTA is centered in the dome when pointed at the zenith? I know you can input dome off-sets in DDW to account for OTA placement, but I thought I would check with the users for some feedback on this. I'm replacing my scope and mount and I have the opportunity to move things.
              > >>
              > >> Thanks.
              > >>
              > >> Mike Cook
              > >> http://www.newcastl eobservatory. com
              > >>
              > >
              > >
              >
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