I've been photographing the sun for some time so I can give some pointers.
Here's one of mine:
So let me start with the obvious bits.
1. Looking at the sun without the right protection will blind you and will destroy equipment. No Chinese sourced "The SUN" black filters that crack - get the right stuff from the start.
When taking images of the sun - it's better to use the live view on an LCD screen rather than using a finder with your eye for this reason. Did I say take no chances?
2. Filters and wave lengths.
The sun put a MASSIVE amount of light in all wavelengths - including unseen UV and IR.
The first job you will need todo is to reduce the amount of light to the right level using the correct blocking filter. Secondly you may want to look at filters to enhance the surface of the sun (continuum as it's called).
Whitelight - is the name given to the wide band (i.e. all colours) image. You'll see the disk of the sun, the granulations and the sunspots. However it's not good enough to see hydrogen alpha loops. The image above is a white light.
Hydrogen Alpha - this is a very specific bandwidth of red. You need some hard core filters such as Daystar or Lunt filters to get this.. expect to pay £1000+..
There's also others such as Calcium K too.. all these are the same - expensive and you'll need a scope and high speed video camera (such as Point Grey) to make the most out of them.
Here's an Hydrogen Alpha image using a specialist 60mm Lunt solar scope - this is my image but using a borrowed scope, my first time imaging at about 500mm focal length using the 60mm hydrogen alpha scope:
Cost of this scope is in the 1-2K range..
Back to Whitelight...
Baader are a very well regarded german manufacturer so much that they are authorised to service things by Carl Zeiss.
Now they also do some really neat stuff - including something called Baader AstroSolar film. This looks like silver foil but is the correct stuff to use as a starting point - I'll explain a little more:
Baader AstroSolar ND 5.0 - this is both visual and photography safe, it blocks so much that you can put this on the front of your lens and away you go. This is white light filter.
Baader AstroSolar ND 3.0 - this is for photography use only. It blocks less light so you get a brighter image (I'll come to the brightness later). White light filter.
AstroZap Baader Solar Filter - this is a ND5.0 filter foil in a metal ring with screw feet that hold the filter securely (although I would suggest taping too). The white light images above were taken with this over the end of the normal refractor scope and camera.
These foils reflect 99.99999% of the light. so you get a safe amount of light. Next up you may want the following filters:
Alternatives to foil are:
A. "Hershall Wedges" - these are great devices for telescopes rather than camera lenses.. basically they fit on the back of refractors and actually cope with all the heat generated. I can't use one because my refractor has a "perzval design" flattener. However the images are clearer than foil.
B. IDAS UHB-RS Solar Filter - this is a high tech, japanese filter that can cope with the heat rather than reflecting it like the foil does. Not used one, and so I can't really remark any further as foil has done well for me..
Now filters that help make more out of white light images:
UV/IR cut - these block the additional UV and IR light that your lens may not focus as well as normal visible colour light.
Continuum filter - these enhance the bubbling continuum of the 'surface' of the sun. I use a Green astronomy filter todo something similar.
Now why is ND3.0 better for photography?
The simple answer is the more light the faster the exposure. The faster the exposure the less atmospheric churn and clearer it will be.
However if you're going to look at the sun visually .. you'll need ND5.0 and possible UV/IR cut if you're sensitive to it.
How to use the foil.
The foil has a correct side to face the sun. Make sure you do.
Always attach foil using electrical insulation tape to the scope. This prevents any wind from blowing the foil off or anything knocking the foil off. If it comes off you will go blind.. or destroy your camera. Don't argue.. do it.
This is why the astro filter with foil in a metal ring works better.. the ring allows the tape to be attached without damaging the filter foil.
How long can I keep using the foil.
Foil can be reused as long as there's no pin
*****s (little light spots). If your visual foil has any pin
*****s - do not use it, get some new foil before viewing the sun. The small holes will act as lasers.. leading to pain, suffering and blindness. (sigh.. pin holes..)
Any holes anywhere on the filter.. bin it and get a new one before observing the sun.
Focal lengths.
The focal lengths I have available to me for imaging the sun are:
* 670mm f6.38
* 1340mm f12
* 3350mm f32
* 6700mm f64 (need ND3.0 for this as it gets very dim)
The sun spots above where at 1340mm and above. To get in close you need more focal length.
Technique?
The normal technique is to use a tracking mount.. that follows the path of the sun automatically. This means you can take 1000s of images, sort through them using some solar astro tools to grade the quality of images and only take those being over 95% quality.
You then use stacking to improve the quality of the images - registax is a good example that will work with solar images.
Can I make more out of my images with a 200 or 400mm lens?
Yes. Take lots of images. Then use a technique called super-resolution (or drizzle) stacking. This aligns the images, then uses the differences in the images to uncover more detail within the image. It's a great technique and will help you make the most of this opportunity.
Taking flats (i.e. to uncover the curvature of the lens for the focus position) and darks (that give the read noise - can be done later).
Did I say take lots of images.. 1000s.. devote SD cards to it..
