Setting shutter speeds in Backyard EOS

[Stargeezer63]

Hi to the forum.  I purchased Backyard EOS and it has been working perfectly.  I am using a Canon 5D MK II.  Jupiter has been great this spring and with the warm weather and clear skies I am getting all the data I can.  One thing I don't understand.  What is the role of selecting shutter speeds in the planetary section of the program?  Isn't the frame rate the shutter speed?  I notice that changing shutter speeds changes the image on the laptop due to Exposure Simulation. Does this actually affect the AVI file image?  As I understand it, the program calculates a frame rate based on the camera characteristics . My AVI images of Jupiter do not look anything like the laptop images, especially at high magnification. 

[PoppaChris]

Guylain can better answer this but, my understanding is that the FPs is strictly a function of live view's ability to output frames.  Hence approximately 25FPS (normally 26.1FPS with my T2i).  The actual shutter speed is BULB.  It only opens once for the imaging run and closes once at the end.  Therefore, the "shutter speed" adjustment in Planetary is more of a "gain" function similar to ISO.  It is a simulated shutter speed, not an actual one.

 

 Am I right, Guylain?

[admin]

Guylain can better answer this but, my understanding is that the FPs is strictly a function of live view's ability to output frames.  Hence approximately 25FPS (normally 26.1FPS with my T2i).  The actual shutter speed is BULB.  It only opens once for the imaging run and closes once at the end.  Therefore, the "shutter speed" adjustment in Planetary is more of a "gain" function similar to ISO.  It is a simulated shutter speed, not an actual one.

 

 Am I right, Guylain?

 

This is correct, it is a simulated shutter speed.

 

However, in planetary you do not want to use BULB, you want/should use a TV value < 2 seconds.  This is because exposure simulation is nullified in BULB mode

 

Regards,

[admin]

Without it you would certainly -always- over expose your planetary recording.  Setting to anything over 2 seconds nullifies the exposure simulation set in the camera, so it does give the ability to do that as well.

 

Hope this helps,

[Stargeezer63]

I guess my question is more functional.  If the program is creating an AVI file at 10 fps, what does setting a shutter speed do?  If I set 1/20th of a second as the shutter speed, does the program only actually expose the camera sensor for half the time within each frame?  Once I get to 1/10th second exposure speed, same as the frame rate, does the program expose each frame for the entire time within each frame?  Any longer than 1/10th of a second doesn't matter since the frame rate doesn't change?  I guess that would be a way of reducing exposure for a very bright object.  

 

My Jupiter image at high power is very dim. I am increasing ASA to try and get more detail.  Despite the fine weather the seeing is terrible.  The image is bouncing around all over the screen. 

[astroman133]

The frame rate is basically as fast as the camera can read out the sensor and download it to the PC. It is limited by sensor size, the DIGIC processor, and available USB bandwidth.

 

As Guylain said, you would use the Exposure and ISO in Frame & Focus, Planetary, and Drift Align modes to control the brightness of the downloaded LiveView frames.

[admin]

It does nothing to impact actual fps, live view provides roughly 20 to 25 frames per second regardless of shutter speed.  This is how DSLR works.

 

Shutter speed is there only as a function of exposure simulation.

 

Hope this helps,

 

Regards,

[Stargeezer63]

So shutter speed does not affect the actual exposure on the AVI file?  It just affects the brightness of the exposure simulation? The frame rate would be the actual shutter speed?

[astroman133]

For operation with LiveView active the exposure is not like a normal shutter speed and does not affect the frame rate in any way.  It is a brightness or gain adjustment that the camera applies to the image.

 

You want the image to be dark, but light enough that you can see the equatorial bands.  You should experiment with different values. You can stretch the image after the frames have been stacked.  It is pretty normal that the planet moves around when viewing the AVI file.  That is why you capture so many frames. The stacking software (RegiStax or AutoStakkert, for example) will grade each of the frames and only select the best frames for stacking.  This allows you to take advantage of brief intervals when the seeing is not as bad to get a sharper image.

[astroman133]

Basically, yes but while LiveView is active, the shutter is always open so the frame rate is the exposure, but not a "shutter speed".

[s3igell]

Removed as "Redundant"...

[Stargeezer63]

That is a good point. The sensor is "on" so the software can decide on a virtual frame rate to create the series of AVI files we need for stacking. Gain can be used to tune the exposure. I was confused by the shutter speeds displayed in the program from 30" to 1/8000 just like in the camera. I am hung up from video work. You get 30fps (1/30th sec) and the rest is done with f stops. No f stops with a telescope. Good discussion. Learning a lot. AutoStakkert has done miracles with the Jupiter AVI files.