front surface mirror projection of sun
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Dhinakar Rajaram
Feb 17, 2012, 9:06:45 AM2/17/12
to Bangalore Astronomical Society, aryabatta
17/02/2012
Dear All,
Today I got front surface or first surface mirror for projecting sun safely to see spots and transits specially made by SPACE as a gift. This method of solar observation I have suggested to some schools in USA & Japan through the solar astronomy programme where I am currently a member to see annular solar eclipse in may this year. This method of projection of sun is the safest method to see spots and transits also won't cost much. First surface mirror or front surface mirror (also commonly abbreviated FS mirror) is a mirror with the reflective surface being above a backing, as opposed to the conventional, second surface mirror with the reflective surface behind a transparent substrate such as glass or acrylic.
Front surface mirror is better than a rear surface mirror as front surface mirrors don't defract the light like a rear coated mirror and they faithfully reproduce the image. Rear surface mirror forms ghost reflections
To see the projected image clearly we need a Convex or Concave lens in front of the mirror! The image size depends on the size of the lens! Not on the size of the mirror! the lens to be 110 times bigger than mirror! The disk of the sun cast on the screen will be seen 110 times of the lens! The projection method I have elaborated on my post here last month and for those who sadly not read that here the link : http://dhinakarrajaram.blogspot.in/2012/01/ball-projection-of-sun.html
I am ready to help on this projection if any one wants to experiment to see the sun spots and transits!
This method is absolutely safe.
With warm regards,
R. Dhinakar BBA., MFT., ADCA.
http://dhinakarrajaram.blogspot.com/
http://www.facebook.com/#!/rdhinakar
http://www.orkut.co.in/Main#Profile?uid=10306548996021240054
Twitter: #rdhinakar
SKYPE: rdhinakar
alternate id: rdhi...@solarastronomy.org
Member: Astronomes sans frontières & Charlie Bates Solar Astronomy Project
***********************************************************
"Science without religion is lame, religion without science is blind” - Albert Einstein
God is traded as a commodity in this world by Theists as well as Atheists including so called Agnostics and Deist – Myself
Impossible n'est pas français - Napoleon Bonaparte
"Face the problem. Don't evade it. Find a solution, however small. People will be satisfied if you do something" - K.Kamaraj Nadar
Dear All,
Today I got front surface or first surface mirror for projecting sun safely to see spots and transits specially made by SPACE as a gift. This method of solar observation I have suggested to some schools in USA & Japan through the solar astronomy programme where I am currently a member to see annular solar eclipse in may this year. This method of projection of sun is the safest method to see spots and transits also won't cost much. First surface mirror or front surface mirror (also commonly abbreviated FS mirror) is a mirror with the reflective surface being above a backing, as opposed to the conventional, second surface mirror with the reflective surface behind a transparent substrate such as glass or acrylic.
They are made for applications requiring a strict reflection without a ghosting effect as seen with a second surface mirror - where a faint secondary reflection could be observed, coming from the front surface of the glass.
In other words :Front surface mirror is better than a rear surface mirror as front surface mirrors don't defract the light like a rear coated mirror and they faithfully reproduce the image. Rear surface mirror forms ghost reflections
To see the projected image clearly we need a Convex or Concave lens in front of the mirror! The image size depends on the size of the lens! Not on the size of the mirror! the lens to be 110 times bigger than mirror! The disk of the sun cast on the screen will be seen 110 times of the lens! The projection method I have elaborated on my post here last month and for those who sadly not read that here the link : http://dhinakarrajaram.blogspot.in/2012/01/ball-projection-of-sun.html
I am ready to help on this projection if any one wants to experiment to see the sun spots and transits!
This method is absolutely safe.
With warm regards,
R. Dhinakar BBA., MFT., ADCA.
http://dhinakarrajaram.blogspot.com/
http://www.facebook.com/#!/rdhinakar
http://www.orkut.co.in/Main#Profile?uid=10306548996021240054
Twitter: #rdhinakar
SKYPE: rdhinakar
alternate id: rdhi...@solarastronomy.org
Member: Astronomes sans frontières & Charlie Bates Solar Astronomy Project
***********************************************************
"Science without religion is lame, religion without science is blind” - Albert Einstein
God is traded as a commodity in this world by Theists as well as Atheists including so called Agnostics and Deist – Myself
Impossible n'est pas français - Napoleon Bonaparte
"Face the problem. Don't evade it. Find a solution, however small. People will be satisfied if you do something" - K.Kamaraj Nadar
Sunil G.R.
Feb 17, 2012, 10:01:38 AM2/17/12
to b-...@googlegroups.com
Hi,
Yes, i had bookmarked this page to read it later. Somehow till now, i could not go through it fully. But got the jist of it.
I hope this is also one of the DIY project.
What would be approx cost to make this experiment?
Asking this question because, thinking to tell this to few school students. So getting the details of the cost involved.
Regards,
Sunil.
Yes, i had bookmarked this page to read it later. Somehow till now, i could not go through it fully. But got the jist of it.
I hope this is also one of the DIY project.
What would be approx cost to make this experiment?
Asking this question because, thinking to tell this to few school students. So getting the details of the cost involved.
Regards,
Sunil.
Dhinakar Rajaram
Feb 18, 2012, 2:31:35 AM2/18/12
to Bangalore Astronomical Society
My blog post has the costs in detail!
On Feb 17, 8:01 pm, "Sunil G.R." <supersu...@gmail.com> wrote:
> Hi,
>
> Yes, i had bookmarked this page to read it later. Somehow till now, i could
> not go through it fully. But got the jist of it.
>
> I hope this is also one of the DIY project.
> What would be approx cost to make this experiment?
>
> Asking this question because, thinking to tell this to few school students.
> So getting the details of the cost involved.
>
> Regards,
> Sunil.
>
On Feb 17, 8:01 pm, "Sunil G.R." <supersu...@gmail.com> wrote:
> Hi,
>
> Yes, i had bookmarked this page to read it later. Somehow till now, i could
> not go through it fully. But got the jist of it.
>
> I hope this is also one of the DIY project.
> What would be approx cost to make this experiment?
>
> Asking this question because, thinking to tell this to few school students.
> So getting the details of the cost involved.
>
> Regards,
> Sunil.
>
Harshad RJ
Feb 18, 2012, 4:46:43 AM2/18/12
to b-...@googlegroups.com
I couldn't entirely follow the blog post, it's a little confusing. But anyway, it inspired me to go out and project the Sun with my 8" Newt.
My first attempt last year had been a disaster.. had managed to burn up the focuser.
But this time it went fine, and managed to observe sunspots 1419 and 1420. I used one of the cheaper Kellner eyepieces; couldn't resolve details in the sunspots or solar surface. I was wary of trying the costlier eyepieces. Has anyone seen high resolution in their solar projections?
The best view of the Sun I have seen was from Hemanth's terrace many years back. This was without projection. We could clearly see the surface texture of the Sun.
--
Harshad RJ
http://lavadip.com
My first attempt last year had been a disaster.. had managed to burn up the focuser.
But this time it went fine, and managed to observe sunspots 1419 and 1420. I used one of the cheaper Kellner eyepieces; couldn't resolve details in the sunspots or solar surface. I was wary of trying the costlier eyepieces. Has anyone seen high resolution in their solar projections?
The best view of the Sun I have seen was from Hemanth's terrace many years back. This was without projection. We could clearly see the surface texture of the Sun.
--
Harshad RJ
http://lavadip.com
Dhinakar Rajaram
Feb 19, 2012, 1:26:48 AM2/19/12
to Bangalore Astronomical Society
There are aluminised first surface mirrors offered by Scientific
Advance Co, Mylapore, Chennai who supply it on order. I came to know
on them on Saturday. The Methods I posted are very simple. Fix a front
surface mirror to a ball larger than the mirror! place a very large
focus Concave lens on front of the mirror as first surface mirrors
don't give a clear refection on a surface. Need concave to to see
clearly. On the FL point of the lens place a screen , you can see the
spots and transits.
Another alternative to first surface mirror: Take a mirror acrylic
sheet. Cut a round piece from that to your desired diameter. rub the
edges for smooth shape. Use a paint remover to clean off the grey
coating ( paint remover will easily damage the acrylic hence be fast!
Now use another cleaner to remove off the smudge and to polish the
surface. There is you cheap DIY front surface mirror!
We need good magnification to see the spots. So the Lens to be bigger
and better with good FL.
Advance Co, Mylapore, Chennai who supply it on order. I came to know
on them on Saturday. The Methods I posted are very simple. Fix a front
surface mirror to a ball larger than the mirror! place a very large
focus Concave lens on front of the mirror as first surface mirrors
don't give a clear refection on a surface. Need concave to to see
clearly. On the FL point of the lens place a screen , you can see the
spots and transits.
Another alternative to first surface mirror: Take a mirror acrylic
sheet. Cut a round piece from that to your desired diameter. rub the
edges for smooth shape. Use a paint remover to clean off the grey
coating ( paint remover will easily damage the acrylic hence be fast!
Now use another cleaner to remove off the smudge and to polish the
surface. There is you cheap DIY front surface mirror!
We need good magnification to see the spots. So the Lens to be bigger
and better with good FL.
Harshad RJ
Feb 19, 2012, 3:07:34 AM2/19/12
to b-...@googlegroups.com
Hi Dhinakar,
Thanks for responding.
I am aware of front-side coating since it is commonly used in telescopes for both primary and diagonal mirrors. But I am not sure if you are talking about a flat mirror or a concave mirror. If it's concave, is it spherical or parabolic?
A parabolic mirror can focus distant objects by itself without needing a lens. However, you need lenses to enlarge the image. A spherical mirror performs like a parabolic mirror but can't focus distant objects perfectly (this defect is called spherical aberration). A flat mirror will not affect focussing at all; it will only help change the direction of the sun's rays.
Ball projection is a commonly used word for projecting images on a ball (or spherical surface). In your case, I think you should say ball-mounted mirror to avoid confusion. Your idea itself is nice and useful, and pretty easy to implement.
cheers,
Thanks for responding.
On Sun, Feb 19, 2012 at 11:56 AM, Dhinakar Rajaram <rdhi...@gmail.com> wrote:
There are aluminised first surface mirrors offered by Scientific
Advance Co, Mylapore, Chennai who supply it on order. I came to know
on them on Saturday.
I am aware of front-side coating since it is commonly used in telescopes for both primary and diagonal mirrors. But I am not sure if you are talking about a flat mirror or a concave mirror. If it's concave, is it spherical or parabolic?
A parabolic mirror can focus distant objects by itself without needing a lens. However, you need lenses to enlarge the image. A spherical mirror performs like a parabolic mirror but can't focus distant objects perfectly (this defect is called spherical aberration). A flat mirror will not affect focussing at all; it will only help change the direction of the sun's rays.
Ball projection is a commonly used word for projecting images on a ball (or spherical surface). In your case, I think you should say ball-mounted mirror to avoid confusion. Your idea itself is nice and useful, and pretty easy to implement.
cheers,
Dhinakar Rajaram
Feb 20, 2012, 2:01:42 AM2/20/12
to Bangalore Astronomical Society
Acrylic mirror is suited The BEST for Annular and Total Solar Eclipse
and may not sound good for Venus Transit! I forgot to mention this!
On Feb 19, 1:07 pm, Harshad RJ <harshad...@gmail.com> wrote:
> Hi Dhinakar,
>
> Thanks for responding.
>
> (or spherical surface). In your case, I think you should say *ball-mounted
> mirror* to avoid confusion. Your idea itself is nice and useful, and pretty
and may not sound good for Venus Transit! I forgot to mention this!
On Feb 19, 1:07 pm, Harshad RJ <harshad...@gmail.com> wrote:
> Hi Dhinakar,
>
> Thanks for responding.
>
> On Sun, Feb 19, 2012 at 11:56 AM, Dhinakar Rajaram <rdhina...@gmail.com>wrote:
>
> > There are aluminised first surface mirrors offered by Scientific
> > Advance Co, Mylapore, Chennai who supply it on order. I came to know
> > on them on Saturday.
>
> I am aware of front-side coating since it is commonly used in telescopes
> for both primary and diagonal mirrors. But I am not sure if you are talking
> about a flat mirror or a concave mirror. If it's concave, is it spherical
> or parabolic?
>
> A parabolic mirror can focus distant objects by itself without needing a
> lens. However, you need lenses to enlarge the image. A spherical mirror
> performs like a parabolic mirror but can't focus distant objects perfectly
> (this defect is called spherical aberration). A flat mirror will not affect
> focussing at all; it will only help change the direction of the sun's rays.
>
> *Ball projection* is a commonly used word for projecting images on a ball
>
> > There are aluminised first surface mirrors offered by Scientific
> > Advance Co, Mylapore, Chennai who supply it on order. I came to know
> > on them on Saturday.
>
> I am aware of front-side coating since it is commonly used in telescopes
> for both primary and diagonal mirrors. But I am not sure if you are talking
> about a flat mirror or a concave mirror. If it's concave, is it spherical
> or parabolic?
>
> A parabolic mirror can focus distant objects by itself without needing a
> lens. However, you need lenses to enlarge the image. A spherical mirror
> performs like a parabolic mirror but can't focus distant objects perfectly
> (this defect is called spherical aberration). A flat mirror will not affect
> focussing at all; it will only help change the direction of the sun's rays.
>
> (or spherical surface). In your case, I think you should say *ball-mounted
> mirror* to avoid confusion. Your idea itself is nice and useful, and pretty
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