Does BYEOS only work on point-source light?

[deepend]

Hi,

 

I connected up the camera to the laptop last night and tried the frame and focus on an indoor object. No matter how sharp I got the focus, the FWHM stayed at 64 all the time. I was under the impression that it's supposed to drop as we approach precise focus. So will this only work on point-source lights like a star?

 

Also, once I go into frame and focus, the live view on the camera blacks out. Is this normal? Canon T4i.

 

Thanks

 

Roger

[deepend]

Many, many thanks, people. Moving on now

[admin]

FWHM and HFD are meant to be used with a star only, it will not work inside during day time.

 

For this you need to use SdDev and work with the higher number.

 

Regards,

[astroman133]

You are correct.  FWHM focus metric only works for point sources (stars).  Not only that the star must be inside the zoom box.  This is discussed in the Focus Metrics section of the BYE User Guide.

 

LiveView takes very short exposures (well under a second) and displays them on the camera's LCD display or makes them available for download by BYE.  When your camera is connected to a telescope at prime focus only the brightest stars will show in the image.  You can raise ISO and lengthen the exposure time (to a point) to brighten the display to make it easier to see the star.  I would suggest choosing Sirius or Arcturus, setting the ISO to the highest value, and the exposure time to 2 seconds (set the shutter dropdown to 2" NOT Bulb with a duration of 2. NOTE: some cameras have a menu setting for Exposure Simulation in LiveView.  This setting needs to be enabled in order to control the LiveView image brightness with ISO and shutter speed settings.

 

You can play with this during the day by putting a lens on the camera and connecting it to your PC and BYE.  You should notice that with very short shutter speeds the LiveView display is very dark and speeds longer than 2 seconds are bright and that when you are longer than 2 seconds changing the shutter speed does not change the image much.  But the range from 2 seconds down to 1/100 second should noticeably change the brightness.

[dts350z]

Since no one answered your 2nd question. Here's an unofficial response:

 

Also, once I go into frame and focus, the live view on the camera blacks out. Is this normal? Canon T4i.

 

 

Live view is starting with whatever exposure simulation you last used, or maybe with an exposure simulation that is equal to your last capture plan. In any case, you can change this behavior by going into settings and then checking off "Maximum Sensitivity" in the "Live View" section. Apply and Save the settings.

 

Now each time you enter Frame and Focus (Or planetary) your exposure simulation will be set to the maximum sensitivity. 

 

That said, things may still be "black" if you don't have a bright star or planet in the frame. 

 

You may want to go into your camera menus (on the t4i) and make sure it's set to allow the highest possible iso. Looking on the internet for t4i iso expansion I see:

Found it: in the manual--pg 294. It's in the C.Fn I (exposure) menu. C.Fn-2 ISO expansion

 

Once you set this to "H", then you will be able to set your ISO up to 25,600 using the normal method of setting ISO.

 

 

Even if you don't plan on shooting astro images at iso 25600, you may want to use it for short exposure previews, plate solving, or exposure simulation.

 

Cheers,

Z