Approve the Cookies
This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies. Read More.
OK
Index  •   • New posts  •   • RTAT  •   • 'Best of'  •   • Gallery  •   • Gear  •   • Reviews
New posts  •   • RTAT  •   • 'Best of'  •   • Gallery  •   • Gear  •   • Reviews
Register to forums    Log in

 
FORUMS Photography Talk by Genre Astronomy & Celestial Talk
Thread started 02 Feb 2012 (Thursday) 06:55
Prev/next
sponsored links
(this ad will go away when you log in as registered member)

Making a screw-in Solar Filter

 
hollis_f
Cream of the Crop
hollis_f's Avatar
10,649 posts
Gallery: 1 photo
Joined Jul 2007
Sussex, UK
Feb 02, 2012 06:55 |  #1

What with this year being the last opportunity for a transit of Venus, an annular eclipse for some Americans and the approaching solar maximum producing a lot of sunspots, it's likely that more people will be interested in shooting the Sun.

First off - Safety is paramount. Looking at the Sun with the naked eye can be dangerous. Using magnifying optics can be very dangerous. Do not be tempted to try ND filters, smoked glass, exposed film, Mylar, crisp (potato chip) packets or any of the myriad other items that I've seen recommended. Even if they block most of the visible light there's a good chance they'll let all the retina-frying infrared through. Use something designed for the job.

Now, there are a few specialised filters that cost several hundred Pounds/Dollars/Euros. Luckily there is also Baader AstroSolar Filmexternal link. This is a very thin plastic/metal film that does a great job of blocking all the nasty radiation from the Sun. And an A4 sheet of it costs just £20external link. That's enough to make a couple of 77mm filters and one big one to fit a super-tele lens or a telescope. Today I want to describe how I make the 77mm filter. Later in the year I'll show how I make a large filter for my 300 f2.8 (these big ones aren't easy to store, so I'll wait until a week or so before the transit in June).


Frank Hollis - Retired mass spectroscopist
Give a man a fish and he'll eat for a day. Teach a man to fish and he'll complain about the withdrawal of his free fish entitlement.
Gear Websiteexternal link

LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as registered member)
hollis_f
THREAD ­ STARTER
Cream of the Crop
hollis_f's Avatar
10,649 posts
Gallery: 1 photo
Joined Jul 2007
Sussex, UK
Feb 02, 2012 07:06 |  #2

To make a 77mm Solar Filter I got a sheet of the AstroSolar film and two 77mm UV/'protective' filters (I found two Hoya Pro1 second-hand for a good price). First, in one corner trace around the outside of one of the filters - like this...

IMAGE: http://www.frankhollis.com/temp/Solar%20Filter_20120202_001.jpg
(The larger circle is for my 300mm lens).

Then cut out the circle of AstroSolar film. You're going to want some overlap, so make sure you cut outside of the circle you've traced earlier. Now, make sure the surfaces of the filters are clean (you'll not be able to clean the interior surfaces later).

IMAGE: http://www.frankhollis.com/temp/Solar%20Filter_20120202_002.jpg

Place one filter, thread down on a table and carefull lay the film circle on top - making sure there is some overlap all around. Now, carefully lower the second filter, thread-side down, onto the first and screw them together. Don't worry if the film becomes wrinkled. You should end up with a filter-film-filter sandwich, with bits of film sticking out all around.

IMAGE: http://www.frankhollis.com/temp/Solar%20Filter_20120202_003.jpg

OK, it's time to test it out.

Frank Hollis - Retired mass spectroscopist
Give a man a fish and he'll eat for a day. Teach a man to fish and he'll complain about the withdrawal of his free fish entitlement.
Gear Websiteexternal link

LOG IN TO REPLY
hollis_f
THREAD ­ STARTER
Cream of the Crop
hollis_f's Avatar
10,649 posts
Gallery: 1 photo
Joined Jul 2007
Sussex, UK
Feb 02, 2012 07:19 |  #3

Set your camera up on a tripod looking outside at a fairly bright scene, without the filter, and take a shot. This was ISO200, f4, 1/2000s

IMAGE: http://www.frankhollis.com/temp/Solar%20Filter_20120202_004.jpg

Now, the filter should reduce the exposure by around 15 stops. This was ISO200, f4, 30s which is around 16 stops.

IMAGE: http://www.frankhollis.com/temp/Solar%20Filter_20120202_005.jpg

What we're looking for here is any sign of leakage, where an ill-fitting filter, or a hole in the film, is letting light through. This looks good so it's time for the final test.

Attach the filter then set the camera up on a tripod on a bright sunny day. Or, if you're in the UK, when the cloud is thin enough for you to be able to see the Sun. If your camera has liveview then use it. Sweep about until the Sun appears on the LCD. It'll be a grey circle, small or very small depending on your lens in a jet-black background. Now you're ready to Shoot the Sun.

You'll want to focus manually (liveview with zoom can really help) preferably on any sunspots that are present. Don't use automatic exposure, as with the Moon it'll be horribly overexposed.

Here's my effort from the morning with my 100-400. ISO400, f11, 1/1000s. This is a crop from the centre of the frame. You'll need around 1500mm on APS-C for a full-frame shot.

IMAGE: http://www.frankhollis.com/temp/Solar%20Filter_20120202_006.jpg

Frank Hollis - Retired mass spectroscopist
Give a man a fish and he'll eat for a day. Teach a man to fish and he'll complain about the withdrawal of his free fish entitlement.
Gear Websiteexternal link

LOG IN TO REPLY
SteveInNZ
Goldmember
1,355 posts
Joined Nov 2007
Auckland, New Zealand
Feb 02, 2012 12:48 |  #4

Good idea to post something about how to do it safely.
Another method is to use the adapter ring for a Cokin style filter holder. Put glue on the flat surface and place it down on the film so you end up with flat film and no gaps (which are a pain). Then just screw it in like a normal filter. Don't bother trying to make a Cokin style (square) filter though. You need the light-tight seal around the edge.
You can make a simple solar finder with a cardboard tube mounted in the hotshoe. Watch the shadow on the ground until you can see the hole and you're pointed at the sun.


"Treat every photon with respect" - David Malin.

LOG IN TO REPLY
j4cub
Member
j4cub's Avatar
55 posts
Joined Jan 2012
Sarasota, Fl.
Mar 26, 2012 18:45 as a reply to SteveInNZ's post |  #5

Very nice work. I'm going to order a piece of the film and give it a try.
Tim


Who's mom kidding, I don't see any electricity in there.

LOG IN TO REPLY
ConEd
Mostly Lurking
19 posts
Joined Jun 2011
Austria
Mar 28, 2012 11:32 as a reply to j4cub's post |  #6

Perfect Idea.
If you allow i will copy that :-)
I'm also looking for such an solution, but here in Austria the Venus Transit is not visible in its full lengh.
And i don't know if the weather is fine on this day.


Canon EOS 7D | Canon Objectiv EF 70-200mm f2.8 L IS II USM | Canon Extender EF 2x III | Tamron Objectiv AF 18-270mm f3.5-6.3 Di II VC LD Asp IF Makro | Sigma AF 18-20mm f3,5 EX DC HSM | Canon Speedlite 430EX | Infrarot Remote CanonRC-1 | Cable Remote Canon TC-80N3
flickrexternal link

LOG IN TO REPLY
Celestron
Cream of the Crop
7,713 posts
Gallery: 1 photo
Joined Jun 2007
Texas USA
Mar 28, 2012 12:41 |  #7

I agree with SteveInNZ , also i might add that the Baadar film should be wrinkled to a certain amount anyway cause that allows for expansion of the film as it gets hot and it does get hot ! If it's tight the heat expansion can cause it to tear while viewing and that second can cause permanent eye damage and possible blindness that is not reversible ! So take caution no matter what !




LOG IN TO REPLY
Jay-Bird
Senior Member
Jay-Bird's Avatar
Joined Jun 2009
Las Cruces, New Mexico
May 11, 2012 23:32 |  #8

Bump for a thank you on how to make this! Why not just sandwich the filter between the lens and 1 UV filter? Is it strong enough to scratch the lens?


Facebook:https://www.facebook.c​om/ZeroedInPhotographyexternal link
http://www.zeroedinpho​tography.wordpress.comexternal link

LOG IN TO REPLY
hollis_f
THREAD ­ STARTER
Cream of the Crop
hollis_f's Avatar
10,649 posts
Gallery: 1 photo
Joined Jul 2007
Sussex, UK
May 12, 2012 01:21 |  #9

Jay-Bird wrote in post #14419202external link
Bump for a thank you on how to make this! Why not just sandwich the filter between the lens and 1 UV filter? Is it strong enough to scratch the lens?

The Astrofilm is a very thin film. If you were to sandwich it between the lens and a filter I'm doubtful that it would be reusable after it was removed. Using the two filters means you can keep the whole thing assembled for re-use.


Frank Hollis - Retired mass spectroscopist
Give a man a fish and he'll eat for a day. Teach a man to fish and he'll complain about the withdrawal of his free fish entitlement.
Gear Websiteexternal link

LOG IN TO REPLY
Jay-Bird
Senior Member
Jay-Bird's Avatar
Joined Jun 2009
Las Cruces, New Mexico
May 12, 2012 09:12 |  #10

hollis_f wrote in post #14419558external link
The Astrofilm is a very thin film. If you were to sandwich it between the lens and a filter I'm doubtful that it would be reusable after it was removed. Using the two filters means you can keep the whole thing assembled for re-use.

Of course, that makes too much sense for me to figure out! I am going order me up some film! Thank you!


Facebook:https://www.facebook.c​om/ZeroedInPhotographyexternal link
http://www.zeroedinpho​tography.wordpress.comexternal link

LOG IN TO REPLY
rburbank
Hatchling
1 post
Joined May 2012
Seattle, WA
May 13, 2012 19:25 as a reply to Jay-Bird's post |  #11

While looking for help in obtaining a solar filter, I came across this thread. So I ordered the film, purchased some used UV filters and just finished a successful test shot of the sun (I followed all the instructions as written:cool:). I live in the Seattle, WA and will head down to the Oregon/California border next weekend for the annular eclipse. Now that I have the tools, I'm really excited at the prospect of getting some hopefully good images. Thanks to Hollis_F for the great instructions; I'll let you know how it all goes.




LOG IN TO REPLY
Celestron
Cream of the Crop
7,713 posts
Gallery: 1 photo
Joined Jun 2007
Texas USA
May 13, 2012 23:18 |  #12

rburbank wrote in post #14426615external link
While looking for help in obtaining a solar filter, I came across this thread. So I ordered the film, purchased some used UV filters and just finished a successful test shot of the sun (I followed all the instructions as written:cool:). I live in the Seattle, WA and will head down to the Oregon/California border next weekend for the annular eclipse. Now that I have the tools, I'm really excited at the prospect of getting some hopefully good images. Thanks to Hollis_F for the great instructions; I'll let you know how it all goes.

Just keep it protected so it doesn't get damaged .




LOG IN TO REPLY
vandarix
Hatchling
6 posts
Joined Sep 2011
Fort Myers, FL
May 22, 2012 06:27 |  #13

The solar filter sheets are in the mail, will pick up some filters to make this with and will test it tomorrow hopefully. Cheers.




LOG IN TO REPLY
Regulus12
Hatchling
2 posts
Joined May 2012
May 22, 2012 22:40 |  #14

Thanks for posting this DIY. I see that they have 2 film options for the Baader astroSolar. A visual and a photo only. Am I correct in assuming that using the photo type for observation is dangerous, but the observational film, while not ideal because of the reduced light transmission, can be used for photography? Have you used the denser film for photographic work?




LOG IN TO REPLY
PM01
Goldmember
1,188 posts
Joined Dec 2007
USA!
May 26, 2012 22:13 as a reply to Regulus12's post |  #15

Are you sandwiching the solar film between two pieces of glass? Or even a single piece of the UV glass?

I went away from using the solar film - too many pinholes over a short time. Went with the Baader Ceramic Hershel wedge instead on my TEC160FL.




LOG IN TO REPLY
sponsored links
(this ad will go away when you log in as registered member)

14,684 views & 0 likes for this thread
Making a screw-in Solar Filter
FORUMS Photography Talk by Genre Astronomy & Celestial Talk


Not a member yet? Click here to register to the forums.
Registered members get all the features: search, following threads, own gear list and ratings, likes, more forums, private messaging, thread follow, notifications, own gallery, settings, view hosted photos, own reviews and more...


AAA

Send feedback to staff    •   Jump to forum...    •   Rules    •   Index    •   New posts    •   RTAT    •   'Best of'    •   Gallery    •   Gear    •   Reviews    •   Polls

COOKIES DISCLAIMER: This website uses cookies to improve your user experience. By using this site, you agree to our use of cookies. Privacy policy and cookie usage info.

POWERED BY AMASS 1.4version 1.4
made in Finland
by Pekka Saarinen
for photography-on-the.net
Spent 0.00155 for 6 database queries.
PAGE COMPLETED IN 0.03s
Latest registered member is LiliumVA
630 guests, 413 members online
Simultaneous users record so far is 5175, that happened on Jun 16, 2015