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PARACORR with Discovery f4,1 - f5 : YES or NO?

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  • Johan
    I have no experience at all with a paracorr. I first seen coma when i was looking at pictures that i took long time ago with a Bresser 114mm f5 newtonian. The
    Message 1 of 11 , Dec 1, 2007
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      I have no experience at all with a paracorr.

      I first seen coma when i was looking at pictures that i took long
      time ago with a Bresser 114mm f5 newtonian. The center was ok but
      when going to the edges, stars elongaaaaaaaaated... On some pictures
      i saw the secondaries & the primaries in stars on the center.
      Planets where good, give the fact the mount was a motorized EQ2 and
      the camera was an OM1 with normal ASA400 fuji film.

      Good laugh about those old pictures :-)

      Visually i never had any optical issues with my old Meade Starfinder
      16 inch dob.
      The same with my lightbridge 12"f5... Optically: no coma issues.

      So i love advises from you guys Paracorr for visual use on
      Discovery's TD & PDHQ f5-f4 design?

      Johan
      between tulips and mills
    • Don D'Egidio
      Johan, I wouldn t use my 17.5 TD F/5 without one, especially with my Nagler eyepieces. Not so bad with my Panoptic and not needed with my Plossl s or Ortho s.
      Message 2 of 11 , Dec 1, 2007
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        Johan,

        I wouldn't use my 17.5" TD F/5 without one, especially with my Nagler eyepieces. Not so bad with my
        Panoptic and not needed with my Plossl's or Ortho's.

        Don

        ----- Original Message -----
        From: "Johan" <notme@...>
        To: <Discovery-Dob-Users@yahoogroups.com>
        Sent: Saturday, December 01, 2007 5:57 AM
        Subject: [DDU] PARACORR with Discovery f4,1 - f5 : YES or NO?


        >I have no experience at all with a paracorr.
        >
        > I first seen coma when i was looking at pictures that i took long
        > time ago with a Bresser 114mm f5 newtonian. The center was ok but
        > when going to the edges, stars elongaaaaaaaaated... On some pictures
        > i saw the secondaries & the primaries in stars on the center.
        > Planets where good, give the fact the mount was a motorized EQ2 and
        > the camera was an OM1 with normal ASA400 fuji film.
        >
        > Good laugh about those old pictures :-)
        >
        > Visually i never had any optical issues with my old Meade Starfinder
        > 16 inch dob.
        > The same with my lightbridge 12"f5... Optically: no coma issues.
        >
        > So i love advises from you guys Paracorr for visual use on
        > Discovery's TD & PDHQ f5-f4 design?
        >
        > Johan
        > between tulips and mills
        >
        >
        >
        >
        > To unsubscribe from this group (but we hope that you stay), send an email to:
        > Discovery-Dob-Users-unsubscribe@yahoogroups.com
        >
        >
        > Yahoo! Groups Links
        >
        >
        >
        >
      • Don D'Egidio
        Johan, The three eyepieces I use most often are a 20mm Nagler, 12mm Nagler, and a 35mm Panoptic. They do work better with the Paracorr and I use it as I have
        Message 3 of 11 , Dec 2, 2007
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          Johan,

          The three eyepieces I use most often are a 20mm Nagler, 12mm Nagler, and a 35mm Panoptic. They do
          work better with the Paracorr and I use it as I have balanced the scope with it in place.

          I would wait until you get the telescope to see if the you need a Paracorr.

          Don

          ----- Original Message -----
          From: "Johan" <notme@...>
          To: <Discovery-Dob-Users@yahoogroups.com>
          Sent: Sunday, December 02, 2007 2:00 AM
          Subject: Re: [DDU] PARACORR with Discovery f4,1 - f5 : YES or NO?


          > Hello Don, Dell and forum,
          >
          > After thinking about and evaluating mu choice of telescope I decided
          > to change the telescope design I choosed:
          > Selected the 17,5 f5 Truss Design instead of the split tube f4.1.
          > With DSC pre installed (tnx for the good advis Dell)
          >
          > Factors for selecting the pdhq over the TD was
          > 1)that the split tube PDHQ f4.1 is 40 cm shorter than the f5: no
          > ladder needed and still transportable in a medium car.
          > The PDHQ 17,5" f4.1 is 500$ less expensive than the TD 17,5" f5.
          >
          > The lead times at Discovery are long and this allowed me to raise
          > the extra $$$ for a Truss design
          >
          > The size is no issue anymore: a TD fits virtually in most cars.
          > Right?
          >
          > Don, from your posts to the forum (and Dells) I read that you guys
          > own 17,5 TD.
          >
          > Don, you are saying that you won't use your TD without a paracorr.
          > So there is a difference at the eyepiece with or without paracorr?
          > Shall I add the paracorr to my order?
          > decisions decisions...
          >
          >
          > Johan
          > between mills and tulips
        • Johan
          On the Dutch forum, some members advised me to buy the paracorr. wait until you see the differance one wrote... Discovery told me yesterday evening that 1/3
          Message 4 of 11 , Dec 3, 2007
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            On the Dutch forum, some members advised me to buy the paracorr.
            "wait until you see the differance" one wrote...
            Discovery told me yesterday evening that 1/3 of their customer uses a
            paracorr.

            I had this discussion with my wife last evening about the size of the
            telescope.
            How tall is the TD F5 when pointing to the zenith on its rockerbox?
            The website states that the F4.1 is 14 inch shorter than the f5.

            Oh man, I failed to evaluate all that before placing my order.
            How could I forget the most important in this story: my wife!
            Sent a mail last night to change (again) my order to the f4,1.
            I love my wife ;-)

            Johan
          • Don D'Egidio
            Johan, Since you now ordered the F/4.1, I would suggest getting the Paracorr. Don ... From: Johan To:
            Message 5 of 11 , Dec 3, 2007
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              Johan,

              Since you now ordered the F/4.1, I would suggest getting the Paracorr.

              Don

              ----- Original Message -----
              From: "Johan" <notme@...>
              To: <Discovery-Dob-Users@yahoogroups.com>
              Sent: Monday, December 03, 2007 7:06 AM
              Subject: Re: [DDU] PARACORR with Discovery f4,1 - f5 : YES or NO?


              >
              > On the Dutch forum, some members advised me to buy the paracorr.
              > "wait until you see the differance" one wrote...
              > Discovery told me yesterday evening that 1/3 of their customer uses a
              > paracorr.
              >
              > I had this discussion with my wife last evening about the size of the
              > telescope.
              > How tall is the TD F5 when pointing to the zenith on its rockerbox?
              > The website states that the F4.1 is 14 inch shorter than the f5.
              >
              > Oh man, I failed to evaluate all that before placing my order.
              > How could I forget the most important in this story: my wife!
              > Sent a mail last night to change (again) my order to the f4,1.
              > I love my wife ;-)
              >
              > Johan
              >
            • Akarsh Simha
              Hi I have a 17.5 f/5 order with Discovery. Do you think I will require a Paracorr for a 17.5 f/5? I m primarily going to observe Deep Sky Objects. Regards
              Message 6 of 11 , Feb 23, 2008
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                Hi

                I have a 17.5" f/5 order with Discovery. Do you think I will require a
                Paracorr for a 17.5" f/5?

                I'm primarily going to observe Deep Sky Objects.

                Regards
                Akarsh.
              • delbert rohrbach
                Hello Akarsh, I have the 17.5 F5 Split tube and from my experience I start to see the curvature of the primary mirror with eyepieces at 21mm. So depending on
                Message 7 of 11 , Feb 23, 2008
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                  Hello Akarsh, I have the 17.5 F5 Split tube and from my experience I start to see the curvature of the primary mirror with eyepieces at 21mm. So depending on how much magnification you plan on using, you may need a Paracorr. Also it depends how bright the deep sky objects are, how big they appear, and how much contrast your looking for. The stronger the magnification the darker the sky and the better the contrast. Although some objects are too dim and you'll lose details with too much magnification. I guess it comes down to just trying it yourself and deciding if your eyes can overlook the sea gall effect or if you would be happier with a more flattened appearance through your eyepieces.

                  Dell

                  ----- Original Message ----
                  From: Akarsh Simha <akarshsimha@...>
                  To: Discovery-Dob-Users@yahoogroups.com
                  Sent: Saturday, February 23, 2008 12:02:08 AM
                  Subject: Re: [DDU] PARACORR with Discovery f4,1 - f5 : YES or NO?

                  Hi

                  I have a 17.5" f/5 order with Discovery. Do you think I will require a
                  Paracorr for a 17.5" f/5?

                  I'm primarily going to observe Deep Sky Objects.

                  Regards
                  Akarsh.



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                • Johan
                  edited@2020 Akarsh, You probably won t need one. Coma will not be noticable. I had the lightbridge 12 f5 and never noticed coma. I have the paracorr for my
                  Message 8 of 11 , Feb 23, 2008
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                    edited@2020

                    Akarsh,

                    You probably won't need one. Coma will not be noticable.
                    I had the lightbridge 12" f5 and never noticed coma.

                    I have the paracorr for my future TD 17,5.
                    I used it with the 13 inch f5 Truss Dobsonian. There was some
                    improvement. We are using the Nagler T5 31mm, the ETHOS and Meade
                    serie QX 26mm and 5000 8.8mm. All good wide angle EP's. The paracorr
                    barlows 1,15X. So your f5 becomes a f5.75.


                    Dell is right, a paracorr on a F5 is a good investement.
                    You should try and see for youself.

                    Here the URL with the performance graphs:
                    http://www.televue.com/images/accessories/Paracorr%20Graphs.jpg

                    Check the f5 data.

                    I received a mail from our common friend about ETA's
                    I think your order is near the top of their back log now.
                    Send him a mail for an ETA.

                    Lets hope the Discovery not giving reliable ETA's is definittelly
                    over.

                    johan



                    Akarsh...> wrote:
                    >
                    > Hi
                    >
                    > I have a 17.5" f/5 order with Discovery. Do you think I will
                    require a
                    > Paracorr for a 17.5" f/5?
                    >
                    > I'm primarily going to observe Deep Sky Objects.
                    >
                    > Regards
                    > Akarsh.
                    >
                  • Akarsh Simha
                    Hello Thanks a lot for the inputs on the Paracorr. I don t think I ll buy one, atleast for the present. Johan, thanks a lot for the good news. I wanted to make
                    Message 9 of 11 , Feb 23, 2008
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                      Hello

                      Thanks a lot for the inputs on the Paracorr. I don't think I'll buy
                      one, atleast for the present.

                      Johan, thanks a lot for the good news. I wanted to make some changes
                      in my order, so I'm going to send out an email to Bill shortly :-D

                      I'm switching from a Discovery 32mm 2" eyepiece to a Televue Panoptic
                      41mm, following the advice of people at the Cloudy Nights forums.

                      Regards
                      Akarsh.
                    • singularity1101
                      ... Akarsh, I would like to make a few points about your choice of the Panoptic 41. I did see that it is over 100 dollars cheaper than the 31 Nagler so if
                      Message 10 of 11 , Feb 27, 2008
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                        > I'm switching from a Discovery 32mm 2" eyepiece to a Televue Panoptic
                        > 41mm, following the advice of people at the Cloudy Nights forums.
                        >
                        > Regards
                        > Akarsh.


                        Akarsh, I would like to make a few points about your choice of the
                        Panoptic 41. I did see that it is over 100 dollars cheaper than the 31
                        Nagler so if saving money was your goal then the 41 is a good choice.
                        It's a super quality eyepiece that will yield the maximum field of
                        view possible from a 2 inch eyepiece. IF you can spend the extra money
                        I would go for the 31 inch Nagler. It will give you very close to the
                        same actual field of view.

                        -41mm has a fieldstop of about 46mm (field stop is the mask used in an
                        eyepiece that defines the size of the hole that light passes through)
                        -41 gives you 68 degrees of apparent field
                        -41 give you an exit pupil of about 8mm when used with an f5

                        -31 Nagler has a fieldstop of 42mm giving you only slightly less (92%)
                        actual field of view than the 41 panoptic
                        -31 gives you 82 degrees of apparent field
                        -31 gives you an exit pupil of 6mm when used with an f5

                        One big advantage of the 31 is it give almost the same actual field of
                        view BUT magnifies that field 1.32 times more that the 41 which
                        translates into a darker sky (better contrast), more detail visible in
                        objects, and overall, a more spectacular image in front of your eyes.

                        For an f5 scope the other advantage of the 31mm is the exit pupil of
                        6mm doesn't exceed the size of your fully dialated pupil which in
                        young people is about 7mm. With the 41mm eyepiece the 8mm exit pupil
                        will extend beyond your pupil a bit which means you're losing a little
                        of the total light available. If you have any astigmatism you will
                        notice it less with a smaller exit pupil. Also you might begin to see
                        a hint of the spider and secondary shadow when viewing a bright object
                        that fills the field, like the moon. This is due to the relatively low
                        power of the 41 compared to the 31.

                        Again, the biggest advantage of the 31 is more magnification of the
                        same (almost) actual field of view as the 41 and a more asethetically
                        pleasing view.

                        The 41 is an excellent eyepiece but for an f5 scope I would recommend
                        the 31 if you can spend the bucks.

                        Chris
                      • Akarsh Simha
                        Hello Chris, That was a very well explained argument. Yes, as you expected, it was the price that made me choose the 41mm Panoptic over the 31mm Nagler. In
                        Message 11 of 11 , Feb 27, 2008
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                          Hello Chris,

                          That was a very well explained argument. Yes, as you expected, it was
                          the price that made me choose the 41mm Panoptic over the 31mm
                          Nagler. In addition to the 100$+ difference, I need to pay ~ 36%
                          custom duty on that! So I decided I'll settle for a panoptic.

                          Regards
                          Akarsh.
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