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This weeks's astrophoto

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  • This weeks's astrophoto

    I made a solar filter for my telescope.

    Elegant in it's simplicity, with a foreground aroma of hydrogen and a slight aftertaste of helium, we have our Sun.

    (color corrected)



    I am looking forward to sunspot season.

    I don't trust solar filters so I made my own. It's a belt and suspenders approach with a restricted aperture on the front, BOLTED in place with a #14 welder's glass over the aperture. The belt is the X8 neutral density filter on the bottom of the drawtube of the focuser. Even then I have no intention of looking at the sun with my remaining eye. (joke) This is for photo work only.





    This is machining related as there is a new drive on the mount. I will post some more on that later.
    Free software for calculating bolt circles and similar: Click Here

  • #2
    Nice picture of an Egg

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    • #3
      Do you have any idea why the sun is darker at the limbs?
      Free software for calculating bolt circles and similar: Click Here

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      • #4
        Originally posted by Evan
        Do you have any idea why the sun is darker at the limbs?
        What do you mean by limbs? I was joking about the egg, looked like one. If you mean the outer edges, well it would have to do with a difference in temperature and said radiation passing through the said filter your using.
        Now thinking more about it, the sun is really transparent being just a big gas ball. Could it also be that the outer edges of your photo, the sun is more transparent due to less density at the outer edges? I am not using any text book references, just applying wild cognitive intuition on the fly here, so correct me if my line of thinking is incorrect.
        Last edited by BillH; 03-19-2009, 12:49 PM.

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        • #5
          I knew you were joking so I set you up as the straight man since I anticipate this question will come up.

          The photosphere of the Sun, which is the lowest layer of the solar atmosphere, is composed of highly ionized gas and as such is not completely transparent to light. The limbs are the visible edge of the Sun and the light from those edges must pass through a much longer path through the photosphere. Some of the light is absorbed in the photosphere making the limbs darker.
          Free software for calculating bolt circles and similar: Click Here

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          • #6
            Originally posted by Evan
            I knew you were joking so I set you up as the straight man since I anticipate this question will come up.

            The photosphere of the Sun, which is the lowest layer of the solar atmosphere, is composed of highly ionized gas and as such is not completely transparent to light. The limbs are the visible edge of the Sun and the light from those edges must pass through a much longer path through the photosphere. Some of the light is absorbed in the photosphere making the limbs darker.
            Ah so simple geometry, at least part of it.

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            • #7
              Bolting that sucker on is an excellent idea. A friend of mine that teaches an observational astronomy course, and is active in Scouts had a bad scare. One of the Scouts he was showing the Sun to reached up and jerked his solar filter off just as another Scout was about to take a look. Luckily he was close enough to pull the kid away from the eyepice. The kids were about 12ish, and he ALWAYS gives a safety lecture first, so you wouldn't think there would be a problem but...

              You may not have that issue, but there's always a gust of wind or something that could knock it off. Even if you're not looking in the eyepiece, it could be an expensive mistake. He now has several screws installed to hold it on.
              .
              Mike

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              • #8
                Solar cycle 24 is still dragging it's feet (hence the cold nasty weather ). I am surprised though that there's no surface detail at all but it may be under-exposed. What did you use for a light source?

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                • #9
                  A light source???

                  BTW, for detail you need a narrow band hydrogen-alpha filter. $$$$$
                  Last edited by Evan; 03-19-2009, 05:22 PM.
                  Free software for calculating bolt circles and similar: Click Here

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                  • #10
                    Originally posted by Evan
                    for detail you need a narrow band hydrogen-alpha filter. $$$$$
                    I've heard these cost $700 to $10,000, depending on the aperture and the bandwidth. Is there any way you could make one?
                    Allan Ostling

                    Phoenix, Arizona

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                    • #11
                      Originally posted by Evan
                      A light source???
                      Pacific Northwest humor - we deny the presence of this "sun" you speak of. It is rumored to exist beyond the perpetual cloud cover but even the elders have but dim memories.

                      BTW, for detail you need a narrow band hydrogen-alpha filter. $$$$$
                      Yep - I looked once for umounted filter stock and about lost my breakfast. Mounted is expensive enough.

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                      • #12
                        Originally posted by Evan
                        Do you have any idea why the sun is darker at the limbs?

                        it's darker on account of being further away the light ain't got here yet
                        --
                        Tom C
                        ... nice weather eh?

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                        • #13
                          You may not have that issue, but there's always a gust of wind or something that could knock it off.
                          I wouldn't let a youngster observe the sun visually, period. I spent 5 or 6 years instructing Sea Cadets in firearms safety and target shooting and that was bad enough. With 4 at a time on the mats we had at least 3 people watching them at any time. I had to swat one on the next mat to get his attention once. The range officer who was both an Armed Forces lieutenant, our Commanding Officer and an RCMP officer just smiled.

                          Allan,

                          I highly doubt that I can make a Ha filter. I don't know for sure, the thought never crossed my mind.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            Ha filter

                            Evan,

                            www.telescope.com has a Ha filter for US$132.00. You can get them from astrodon (?) or someone like that for a better quality for like US$200 IIRC. They are on astromart.com once in a while.

                            Lenord

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                            • #15
                              Those are nebula filters and are not for solar observation.
                              Free software for calculating bolt circles and similar: Click Here

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