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Live View


krphotogs

Question

I borrowed an D810A from Nikon to try - my normal cameras are D300/D500. With those, when I align my scope after startup - I slew to Vega and use Frame/Focus to center the star. Pretty easy, the screen is pretty dark and Vega is the only star visible. With the D810A,  a few stars visible and the screen with Frame/Focus has a lot of 'noise' (reminds me a a b&w TV from the 60s). So, what is different? I know there are values in settings for live view but I cannot seem to find the details behind them.

 

Kevin

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I have a question related to using the frame and focus setting with D5300. My question is simply how do you use it? I do not see anything on my screen when its on. The only way I see something is with the image setting but its really challenging to adjust focus or reframe using the image setting. Is there a tutorial or instructions for using the frame and focus function? For reference I was using the bulb setting, ISO 3200 and 20sec exposure.

 

Thanks,

Gene

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Live view is only a few milliseconds of data, so only bright stars will show up and you need to be close to focus to begin with.

 

The 20 seconds is virtual since it does not really affect the actual live view exposure length.

 

If all else fail, use the snap picture with the loop feature to take still images.

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Gene,

 

The first thing to understand about LiveView is that the exposures are actually only a few milliseconds long and you can not control their exposure duration. They are short enough that about 10-15 images are downloaded to the PC each second. The actual frame rate depends on factors like the image size and the USB transfer speed. If exposure simulation is activated in the camera, then you can brighten and darken the LiveView image by adjusting the exposure and ISO values. These adjustments only control the brightness of the image. They do not affect the frame rate.

 

I would set the exposure to 2 seconds and the ISO set high. then shorten the exposure setting. You should see the image darken as you keep shortening the exposure. The easiest way to play with this is indoors, with a lens on the camera and low light in the room. If none of this seems to change the brightness of the LiveView image then you should read the previous posts in this thread. Enabling exposure simulation can be tricky with a Nikon camera but doing so is what allows you, and BYN, to adjust the brightness of the LiveView frames to be able to see even the brightest stars..

 

Now once you have a feel for how to adjust the exposure and ISO to maximize the brightness you need to remember the combination that gives you the brightest image. Those are the settings that you need to use when you connect your camera to your telescope at prime focus. Still, remember that the exposures are only a few milliseconds long so even by brightening the LiveView image as much as possible you will only see the very brightest stars on the LiveView screen. Also, if the telescope is way out of focus the stars may not show up at all.

 

If you have no idea what focuser setting is "close" to critical focus then you will have to contort your body to look through the camera's view finder while aiming the scope at a very bright star like Vega. While looking through the view finder you should be able adjust the focuser to bring the camera close to focus. Then, you should be able to activate LiveView and see Vega as a very small dot on the LiveView image on the camera's LCD display. Once you can see Vega on the LiveView image you can connect the camera to your PC and start using BYN's Frame and Focus functionality to get your final focus.

 

You also said that it is challenging to adjust focus or reframe using the image setting. Framing is up to you and is accomplished by trial and error. You move the scope and/or rotate the camera and take a short exposure. You examine that image and repeat, as necessary, until you are satisfied with the framing. Focusing with short, perhaps 5 second, exposures is also pretty simple. This is why BYN has the Snap Image button on the Frame & Focus screen. Here you can take that 5 second exposure and measure the FWHM of one of the stars in the image.. You can move the zoom box rectangle around that star to measure its FWHM. Then tweak the focus and take another image. You repeat this until you are satisfied with the focuser position. Every imager who does not use a DSLR must use this technique to manually focus their camera, so it is a process that you will eventually have to become comfortable with.

 

I hope this helps.

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Hi Guylain and Rich,

Thank you for the feedback. Here is my workflow and perhaps you could comment.

 

Using a diagonal and eyepiece with a reticle I do a visual align in conjunction with Starsense and skysafari and also get my focus dialed in.

I then swap out the diagonal for my focal reducer and D5300. I put a batinov mask on my OTA and take an image of vega (for example) to see where the focus is. So should I be doing this step in frame and focus mode with 2sec exposure at high ISO as Rich suggests? Or can I somehow use liveview on the D5300. I would prefer to use frame and focus mode as I can never get live view on the D5300 to work (I get some warning message about the exposure setting). 

So I think I just need to clearly understand what is the best exposure and ISO to use while in frame and focus mode.

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Gene,

 

I am not a big fan of the Bahtinov mask. Once I have my scope aligned, I don't want to touch it even to add and remove the mask. I did use a mask at one time and found that using the FWHM metric as at least as good and did not require me to touch the mount, the scope, or the camera.

 

If the focus with the diagonal and reticle eyepiece is close to where it needs to be when you remove them and add the camera, then that is a good place to start. That has not been my experience.

 

Understand that Frame and Focus has 2 different modes...LiveView AND Snap Image. Snap images are throw-away JPG images that can be useful for framing and focusing. You can even choose to not save them on your hard drive. LiveView is the fastest way to focus, but it takes a bit of practice as well as a bright star. When in LiveView, the ISO and exposure are just brightness controls that do not change the LiveView frame rate. In Snap Image mode they operate in a traditional way. That is, in Snap Image mode a 2-second exposure is a 2 second exposure. So, you can easily take some Snap images at different exposures and ISO settings to see how long the exposure needs to be to clearly see stars. There is no right or wrong answer here; it depends on what scope you are using. Don't be afraid to experiment. Try 5 seconds, 20 seconds, 30 seconds and see which is most useful.

 

In LiveView mode, you want the brightest image you can get. Read my previous post for how to figure out what how to brighten the image as much as possible.

 

 

 

Read the previous posts in this thread for some tips on use of LiveView.

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I am not a big fan of the Bahtinov mask. Once I have my scope aligned, I don't want to touch it even to add and remove the mask. I did use a mask at one time and found that using the FWHM metric as at least as good and did not require me to touch the mount, the scope, or the camera.

 

I'll take the Opposite View...

 

A Bahtinov Mask is a GREAT TOOL for Focusing - especially for those with Manual Focusers.

 

Concerns over Physical Manipulation of your Mask and Scope:

1) Most any Scope and Mount is going to be Sufficiently Solid that proper handling of a Bahtinov Mask will just barely register on the PHD2 Graph.

2) Most folks without Motorized Focusers will do significantly more "jostling" to their Scope while repeatedly touching and adjusting the Fine Focus Knob.

3) Most folks will Operate under the "Focus then Frame" workflow so again Framing is not At Risk.

 

Actual Utility of the Bahtinov Mask and Mask Focusing Tool:

1) The Bahtinov Diffraction Pattern is a GREAT Visual for beginners who may not understand the details of Critical Focus and FWHM.

2) The Bahtinov Diffraction Pattern has an Absolute Goal (the "Perfect Focus" Pattern) while FWHM has a Relative Goal (the Lowest Number one can seem to attain).

3) The Bahtinov Diffraction Pattern works equally well for a Medium Bright, Very Bright, and even Oversaturated Star (or even a Planet - except Saturn) while FWHM is Saturation Sensitive.

4) The Bahtinov Diffraction Pattern works with Perfect Seeing, Poor Seeing, even Light High Cloud.

5) The Bahtinov Diffraction Pattern works as well with Short Exposures as with LiveView.

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Odd behavior.  There is an equivalent of "exposure simulation" with Nikon as there is with Canon's camera.  I don't recall what Nikon calls it though.  I'll try to dig into my old emails and see if I can find it.

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Here it is...

 

With the D810a you can get live-view exposure simulation in BYN if you have it turned on in the camera to start with.  Just press the "ok" button while in Live View and this should turn it on.

 

Regards,

 

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I did not realize that frame and focus had 2 modes. I will put the input to use this evening if I get decent conditions. I am sure I will have a follow on question or 2.

As far as focus goes,  I use the feather touch micrcofocuser from starizona so I have hands free focusing. I will see whether the B-mask, or the FWHM metric works best for me at my naive stage in the AP game.

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Thanks - not sure I understand and not sure if that was the answer to what I was asking. I will have to see if Live View mode was turned on in camera. But, more to my question, is there a way of increasing the sensitivity in Frame/Focus? I saw a couple parameters on the settings page but was not clear on what they did. As for the 810A, I only have it though the weekend.

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Thanks - not sure I understand and not sure if that was the answer to what I was asking. I will have to see if Live View mode was turned on in camera. But, more to my question, is there a way of increasing the sensitivity in Frame/Focus? I saw a couple parameters on the settings page but was not clear on what they did. As for the 810A, I only have it though the weekend.

 

Actually... that -was- the answer to you question.

 

If you do not turn live view simulation ON then ISO changes and other settings have no impact on the actual intensity of the live stream of images.

 

If you turn live view simulation ON.  You using the camera body itself... turn live on then press the OK button and that is it - that setting should survive you turning the camera off so you only need to do  this once.  This is a toggle button so if you do this twice you've just turned live view simulation OFF.

 

Once you have  live view simulation turned ON any ISO settings in Frame&Focus should change the live view stream images. 

 

Forget about StarHD for now... at least until you get regular live view working.

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I am using a Nikon D750 on a Skywatcher Adventurer.

It would be really nice to have the ability to adjust the focus without constantly manually adjusting the focus and taking a picture 

to see if it's correct. Is there a way to have the same (lens Image)<<< << < >  >> >>> bars for adjusting the focus from the computer as with some auto focusers?  :rolleyes:

thanks,

M Stone

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Ok, apologies for being thick headed. So all I have to do is press the LV button on the back of the camera... will try tonight.

 

StarHD? never heard of that...

 

Happy Thanksgiving!

 

Kevin

 

No.... but once live view is on you need to press the OK button to activate LV simulation.  This is a toggle button so if LV Simulation was on pressing ok wll turn it off.  Do a test, press it and then go to BYN in Frame and Focus and change ISO.... does the image intensity changes?  If yes then it is on, of not press the OK button again.

 

Hope this helps,

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