Live View in Nikon D90

[angelo327]

I have a Nikon D90 attached to a Celestron 6" OTA on the AVX mount.
I Start Celestron's CPWI 2.5.5 software then run BackYardNikon.  BYN controls the SCT via the CPWI drivers.

I'm just thinking out loud here.  I'll eventually figure my issue out.  Writtng it down helps me answer my own questions.

I open BYN interface (Trial Edition v2.1.3 ), Connect to the D90 Camera OK.. The Camera shutter is set to BULB and the Camera ISO is set to 1600.   But I notice the BYN Camera Info Center shows the Camera Info as: S=2, ISO=Hi-1.0, Dial=M. I Click the Frame & Focus BUTTON, hear the camera mirror flip up and see a live image on screen.  How did BYN determined the correct exposure to show a perfectly exposed live view?  How did BYN compute the correct shutter/ISO and why didn't that info get displayed somewhere so I'd have a good starting point?  Does BYN have an auto exposure feature? 

Without a exposure time/ISO starting point I have to create a Plan with multiple single shot exposures and keep guessing exposure settings untill I get close.  I think BYN knows the correct settings because it gave me a perfectly exposed LIVE VIEW when I first started.  My difficulty is guessing an initial exposure when shooting the SUN, Moon or a Planet.  I end up guessing Shutter/ISO settings and SNAP IMAGE to see if I guessed correctly and if not then keep guessing until I find something close to work with; a lenthy process.  If BYN can change camera shutter and ISO then shouldn't I be able to dynamicly see the image exposure change in the Live View without shooting an image.  Knowing the exposure initially used by Live View would save much time.   

 

 

 

 

 

[admin]

BYN didn't figure out anything. The last time you left "M" mode, you probably had those settings. So when the dial went from "B" to "M" this is what you got. Try the same test, but without using BYN, just use the camera buttons to move from B to M, you should get the same outcome.

[astroman133]

There are a couple of things that you are apparently confused about.

1) When you turn the camera on, it remembers its previous settings for shooting mode, ISO, exposure duration, image quality, etc.

2) When you connect BYN with the camera, The settings that are shown in the Camera Information Center are the current settings that just BYN read from the camera.

3) Live View is designed to provide very fast sequences of frames on the camera's LCD display. The display is updated fast enough that it appears to show a live movie of where the camera is aimed. In this context, the shutter duration is meaningless. For example, if the shutter duration is set to 1 second, how could you see 1 second exposures as a live movie? They would show a sequence of update, freeze, update, freeze, with about 1 second between updates. This is now how it behaves. Instead, what you see is that a 1 second exposure is brighter than a 1/2 second exposure, but the frame update rate does not change. The image is however somewhat brighter. This is an approximation, made by the camera to attempt to simulate the change of the exposure duration.

4) Because of 3) above, the settings for ISO and Shutter duration in LiveView should not be used to select appropriate values for imaging.

5) The exposure settings in the Capture Plan Center are not live settings. The settings of Shutter = BULB, Duration = 1, ISO = 1600 are default initial exposure settings that were chosen by the developers as initial values. You can change them, as necessary or replace them by loading a previously saved capture plan. Whatever values you put into row 1 of the capture plan will be downloaded into the camera when you click the Start Capture button and BYN starts executing the plan. They should also show up in the  Camera Information Center almost immediately.

The correct shooting parameters for Solar System objects (Sun, Moon, planets) will be different depending on how you are shooting them. I have shot the moon using LiveView and also with Imaging. I have only shot the Sun with short Imaging exposures. I have only shot planets with Planetary Mode, which uses LiveView. The settings for one are completely independent of the best settings for the other.

That all said, there is nothing better than keeping a log of the initial trial and error for a specific type of shooting. That way you will be able to look up what you previously used to get the initial settings the next time you shoot that target.

I hope this helps.