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Imaging with dslr


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Okay, so i have a canon 5d, im wanting to do some planetary imaging of saturn with it..I know many people use webcams for planetary images with the idea of taking a video and using the still images from this to stack, my question is.....would I be able to use the hd video function on my 5d to record saturn for say 10 mins...collect a thousand still images?? and then stack these on registax? I've had a quick go at recording but registax doesnt seem to recognise the file type (which is .mov) could I simply convert this video file to avi and carry on as normal? Also...with regards to the still images obtained from the video..what settings would they possess? Ie..would the still images have the settings of the original camera settings if I was to take a pic on manual? If you get me?

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You couldn't record it for 10 minutes because the planets rotation would show up, say 60 to 90s maximum.

As far as I know Registax expects an AVI, if you can convert to AVI then I can only guess it will work.

However, I think the concensus is that this type of imaging is best done using webcams so you are making it hard for youself, though probably not impossible if you really try.

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The problem you have is that the atmosphere is constantly changing, giving the impression that your focus is constantly coming and going.

Webcams take many frames per second as a video.

Software like Registax strips the individual frames out of the video and then picks the good ones to stack.

The field of view and number of pixels you get with a webcam suits the application. The webcam works like a 6mm'ish eyepiece.

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And the large sensor is the issue... Saturn, or any planet, on a dSLR barely covers a few pixels, unless you seriously crank up the multipliers (I used 20x worth of barlow and the planet was almost a reasonable size, shame the exposure was in the order of seconds or push to ISO1600 to get it down to something my little alt az mount could handle) on the scope, but then the exposure time per frame becomes silly for an SLR and the IQ disappears. In video mode, I think you use a much smaller area of the sensor and that makes a big difference, as long as you can convert the video to a format, avi, series of images etc, that registax can deal with. Frame rate is also important... You want the highest frame rate possible, for two reasons, 1, to capture as many frames as possible in the short time frames available before rotation smears the surface features, 2, to help overcome the atmospheric wobbling, that becomes far more noticeable at the effective focal lengths you really need.

If we look at the numbers... a 5d is full frame (I think), compare that to something like the SPC900 webcam, and it's equivalents, which has a sensor size equivalent to an 8.5x crop factor. so a 1000mm scope with the SLR is just that, but drop in a webcam, and you're automatically pushed up to an equivalent focal length of 8500mm, then add a 2x or 3x barlow (if the conditions allow), and you'd need something the size of a fairly large building and an awful lot of support to match the FOV with an SLR. Whilst an SPC900 doesn't have the highest frame rate on the market, there's no way an SLR can match the 40-60 frames per second that the dedicated cameras can manage, even my QHY5v guidecamera with a CMOS sensor can hit 85fps top whack.

Having said all that, give it a try and see how you get on.

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haha...doesnt sound too good for me then...:icon_eek:

I also do take the image through my scope (8" lx10) and use a 2x barlow with a variable projection adapter with an eyepiece inside so the image size can be ok...

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I would agree with all the has been posted.

Sure, use your 5D through a scope for large images of the moon (or sun with proper filtration) but for planets you are pushing it. Especially when a cheap (relative to a 5D anyway) webcam will do better, plus it is much lighter and not so much pain should you drop it on a dark night.

I have a 7D so I've already tried converting from the .mov format the camera provides to a .avi that the stacking tools use. You loose so much detail due to the compression plus the addition of many video artefacts from the original video you would have been better off just taking a series of stills in the first place.

But saying that, good results can be had it is just a lot of work but there are better ways of doing it.

On the plus side your 5D is still a great tool:

1. Wide field photography. Stick a wide angle fast lens on and use it to take big sky shots. Either short exposures or really long exposures to get star trails.

2. Narrower field photography. Stick a zoom lens on it and take multiple stills then stack them. Only need a tripod for this.

3. As above but while piggy-backing a telescope that tracks.

4. Stills or video of the moon or sun (with filtration) through a telescope using prime focus. You can really get some great results from this.

5. Stills through a telescope using prime focus of the sky. With accurate tracking do long exposures, without it, do short, multiple exposures and stack them.

6. Just take a some great shots of others using your telescope with the star-field behind.

I.e. your 5D isn't a total waste of time for astronomy, just that there are some things it can do well and some it can't/cheaper ways/better ways etc.



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