Messages

With pleasure 

In order to observe or photography the sun in total safety the best is to use a safety filter that covers all of the light entry, specifically designed for solar observing.

Several decades ago it was done with a special -thus expensive- coated optical glass who has to be perfectly plane and with perfect parallel faces, otherwise the optical quality was compromised. Today mylar films with the same coating exists for a few bucks. The thin mylar film has to be placed front of the objective, and do not need to be flat due to the fact the several µm of the film's thickness has no incidence on the optical quality. Cheaper and easier to use, yet more fragile.

When you have some mylar film mounting it on an objective is up to you: fix it with some tape or rubber band (not recommanded because it may fall off while observing) like this: http://www2.ville.montreal.qc.ca/planetarium/Information/Dossiers/EclipsePartielle2011/filtre_mylar.jpg, or better build a filter support with some cardboard you can paint in black (to avoid light reflections), or even buy a complete set with mylar film and aluminium frame ready to be placed front of your objective with three nylon screws.

Another clever way to use the film (that comes mainly in rectangular sheets) is to build a rectangular frame to place front of any objective, like this: http://photographingtransitofvenus.files.wordpress.com/2012/05/20120527-img_6033.jpg?w=650&h=488

Before putting your eye at the camera or starting liveview place your hand behind the finder. If you see a bright spot of light point away from the sun and carefully check your setup.

To find mylar film sheet and related accessories please google "solar filter film". You will find anything you need, from advices to create a safe filter to ready-to-use commercial solutions.

If you have further questions please do not hesitate.

Having asked the community for some help about a specific aspect of sun photography I would like to stress with you the danger inherent to this activity:

Never look or picture the sun directly, especially with teleobjective, without specific filtering. Any mistake can have devastating consequences on your camera, your eye, or both!

Light coming from the sun not only contains visual wavelenghts, but also a huge amount of UV and IR light. So even if the image seems not dazzling, IR and/or UV can still be harmful! The "trick" consisting to blacken a sheet of glass with a candle to make a homemade filter is not safe at all. Using a very dark grey filter, or stack of them is not safe at all. Any solution not specifically designed to observe the sun will be dangerous!

If you need to picture the sun please to not hesitate to ask a specialist around you (mainly astronomy club) about specific filtering, or drop me a message I will be happy to help.

... if I have understood the problem correctly, this issue is not about camera movement (thus neither mirror lock-up or similar features will help), but about the air between the telescope and the sun acting as a distorting lens.

Absolutely. Now I have to do some homework to see if I can link a steady air moment to a peak on the focus graph or any other monitoring function -as soon as all the clouds around my house decide to migrate somewhere else- to have a clue when firing best shots.

In the meantime I will be grateful if anybody has suggestions for monitoring functions (like focus graph) to test, so I will be ready for the next sunny day 

About an example of air turbulence I have a small .mov (64 MB) showing this effect. If it is possible to upload it I can do that ASAP.

I will also look at focus graph function in details. Thanks for the suggestion.

Thank you for your answers and suggestions.

Planetary imaging is well possible in video mode: the 60D(a) is able to record a video with a resolution of 640x480 pixels, using 640x480 "real" pixels on the center of the CMOS. Because there is no crop or resizing image quality is excellent and you can record faint details on planetary surfaces. The drawback is you use only 640x480 pixels on a 5184x3456 pixels' sensor.

As sun and moon are far bigger seen from earth than planets, astrophotographers try to use all the sensor surface to picture the sun or the moon in full. Using the 640x480 video will lead to take multiple movies of surface parts, then process the videos to get good pictures, then stick them together to get the full surface. In case of the sun, where events (like a solar flare) are moving in minutes, pictures taken on different time have a different aspect, thus "unstickable" . Using a 1080p video will get the surface in full, but due to cropping a lot of fine details are lost.

So currently the trick is to shoot continuously until the buffer is full, redo several time the process hoping one of the picture in the sequence was taken in steady air. It is a sort of slow fps, short time, high resolution sequence... with random results.

A way to improve the amount of good pictures is to monitor air turbulence. It is possible to do so in liveview, but the time your brain decide the picture is clear enough, order your finger to press the button to shoot... it's always too late. So you try to guess when the air will become steady. Results proove that guessing is not an exact science.

But if the detection can be done via the electronic or via a piece of brilliant code and the shoot is done in the next quarter of a second then the amount of good pictures will improve greatly and will let the astronomer hands available for other concurrent activities.

I hope I wasn't boring you too much with all these details 

Before speaking about the feature itself please allow me to introduce the context. When doing solar photography I use a telescope as objective (will be a 900mm F6 équivalent) with absolutely no communication with the camera. Not a problem as it is possible to focus using the telescope and take pictures with manual mode.

The main problem is air turbulence. Even if the telescope is perfectly focussed on the sun, air turbulence will randomly blur the image, from quite nothing to totally fuzzy. Currently I shoot 60 pictures in a row to get in best cases 5 not too blurred and in the worst case nothing at all. It is possible to monitor the turbulence via liveview, but if you try to shoot at the right moment  ... it's always too late  .

Maybe will it be possible to use a function like "Motion Detect" that will fire the camera if the image is at its maximum contrast, condition met only with few to no air turbulence? I yes I'm sure all astrophotographers will bless you and your family until the 30th generation  . If not we will stop at the 29th 

Greetings everybody.

A small introduction seems to be the rule around, but what to say about me having any interest? Maybe that I am an astrophotographer and I use ML on one modified Canon EOS 60D (IR filter removed and replace with a glass, allowing IR pictures) and a Canon EOS 60Da. ML is an invaluable tool for my hobby and I cannot thank enough the team who brought it to us, for free. A donation is in order...

Please be patient with me -as I'm more an astronomer than a photographer- if I don't grasp immediately what is clearly explained and if I ask stupid questions like "Do you accept suggestions?" and "If yes, what is the right forum's topic to do so?", and that as English is not my native language I may miss the point... 

FYI an article in "Astronomy Technology Today" (Volume 7 Issue 3) descibes why astronomers do love ML. It is here: https://www.astronomytechnologytoday.com/?l=/issues.asp