Re: Nikon D5000 Subframe.

So it would be good to transfer an addressable area, say
x,y,width,height, maybe apply a scaling factor.  No idea how that
would happen, might have to be a camera firmware hack.

Could you grab from the hdmi output?  Trying to think of the fastest
way to get pixels out of it.  Zooming the viewfinder probably also
zooms the hdmi, and you can move the zoomed area around the full image
(on my D5200 anyway).  There's some limited ability to convert hdmi to
usb https://www.walmart.com/c/kp/hdmi-to-usb-cables

I've played with motion detection comparing one viewfinder image to
the next.  They're about 200x300 pixels, I was using a Raspberry Pi
Zero attached by USB, surprisingly capable.  I found clouds going over
caused too much variation so I was playing with averaging all the
pixels to get a baseline then comparing pixels to the baseline.  All
in C on a single core Zero on batteries.

What gets transferred as the viewfinder image when you zoom the
viewfinder I don't know, or if you can zoom the viewfinder remotely.
I zoom it to focus for terrestrial stuff just using the LCD.

I played a little with my D5200 mounted on my Celestron using direct
focus with a T-mount.  Then I ran out of summer.  I also picked up one
of the newer Raspberry Pi cameras (8 MP or so) to mount in an eyepiece
just because they're tiny and light.  My D5200 isn't.


On 12/10/19, [email protected] <[email protected]> wrote:
> Hi Lacy,
>
> Thanks for answering.
>
>> On 09 December 2019 at 18:06 Lacy Rhoades <[email protected]> wrote:
>>
>> Can you do the HFD at a lower overall resolution and/or a higher JPEG
>> compression setting?
>
> I can try that.  Some algorithms don't work well on .jpg, such as
> plate-solve or star-detection (which I need to find the focus star in the
> first place.) But maybe I can play with that.
>>
>> I don’t think you can do essentially a sensor crop using anything specific
>> to gphoto2. If there is some "sensor
>> crop" setting in your camera, again, you might find luck using
>> --list-config but the area you’re looking at must
>> be in the centre of the image.
>
> You're right, it's exactly that that I'm looking for.  Maybe I could crop
> the image with another tool, before I transfer it.
>>
>> Can you speed up the network connection? Ethernet? 12MB isn’t really so
>> big in 2019 terms.
>
> It's not just the network, it's also other processing being done at each
> end.  A smaller image would be faster for everything.
>>
>> I admit I do not understand your HFD goal but what does the in-built
>> autofocus not do well already? Does it focus
>> on the skyline or trees when you want to focus on the sky? If so, can you
>> change the focus points in the camera?
>> Just to say that Nikon etc. have spent a lot of brain on how to focus, so
>> it’s nice to leverage that when we can.
>
> It's a DSLR body attached to a telescope, so there is no Nikon lens, just an
> electronic telescope focuser.
>
> Regards
>
> Steve
>
>
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