Webcam resolution for Jupiter

[AstroNebulee]

Hi

Yet another question from me for advice. I have searched the forums before posting but couldn't see a difinitive answer. I have an astromaster 130eq and a svbony sv105 webcam when I was imaging Jupiter the other night I was wondering what resolution is best to use as it's a HD webcam I can get 1920x1080 but see a lot have used 640x480. I know Jupiter is low down at the moment and very soupy atmosphere to get through but I'll attach my image that I stack and processed, though I suspect I have pushed the limits of my set up at moment. 

[CraigT82]

The resolution you're referring to is the number of pixels used to create the image - horizontal by vertical. Ie the portion of the sensor which is used, also known as region of interest (ROI). Jupiter is small and will probably occupy only a few hundred pixels on the sensor so no need to use the full HD. 640x480 is more than enough. 

[AstroNebulee]

1 hour ago, CraigT82 said:

The resolution you're referring to is the number of pixels used to create the image - horizontal by vertical. Ie the portion of the sensor which is used, also known as region of interest (ROI). Jupiter is small and will probably occupy only a few hundred pixels on the sensor so no need to use the full HD. 640x480 is more than enough

Thank you for your reply and help, I always thought if it was being filmed on higher definition then you get more detail but at least I know now, so if I was imaging the moon is use a higher Res because the moon is bigger 

[CraigT82]

Yes the term 'resolution' is used for different things confusingly. For astrophotography the resolution of an image is how much area of the sky each pixel covers (in arcseconds per pixel) and is governed by focal length and pixel size. 

The figures 1920x1080 and 640x480 are referring to 'image sizes'. For the planets you only need small image sizes as the planets images are so small there is no point collecting the full sensor's data when most of it is just black space.  On the moon you may want to image the largest amount of lunar surface you can, and so using a larger image size would be better, but generally the larger the image size the slower the frame rates you'll get. 

[michael8554]

At full res 1920 x 1080, is the video compressed, that's not going to help the quality.

Is the 640 x 480 a crop of the full frame?

That would be better, and would probably allow higher frame rates.

For Long Exposure imaging a lot of emphasis is placed on Image Scale, with 1 to 2 arcsecs/pixel a common goal.

For Planetary Imaging figures lower than 1 are used, what is your figure ?

Michael

[AstroNebulee]

On 14/07/2020 at 21:07, CraigT82 said:

Yes the term 'resolution' is used for different things confusingly. For astrophotography the resolution of an image is how much area of the sky each pixel covers (in arcseconds per pixel) and is governed by focal length and pixel size. 

The figures 1920x1080 and 640x480 are referring to 'image sizes'. For the planets you only need small image sizes as the planets images are so small there is no point collecting the full sensor's data when most of it is just black space.  On the moon you may want to image the largest amount of lunar surface you can, and so using a larger image size would be better, but generally the larger the image size the slower the frame rates you'll get. 

Thank you Craig, that's cleared that one up for me, as I'm new to using my webcam on my scope just wanted clarification. 

[Cosmic Geoff]

With a smaller ROI (region of interest), e.g. 320x240 pixels, the planet image is more closely cropped and the frame rate is higher, which means the imaging total time for a large number of video frames is less, which may improve the quality of the final result.   A smaller ROI puts greater demands on your guiding, however.   With a faster frame rate there is less time for the planet to drift out of frame if the tracking is less than perfect. 

[JonCarleton]

I have a SV105.  Best to set it at 1080p (1920x1080).  That way, if you scale down the image, say, to 640, you get a much sharper image.  I have gotten some really good results with the 105, that I demoted to guide scope after I got the 305.  Looking at the image of Jupiter you show, It looks to me like you stacked it without doing a registration in your stacking program, making the stacked images not completely lined up.  This is my first moon shot with the SV105, shot at 1920x1080 and reduced to 640:

Edited July 16, 2020 by JonCarleton

[michael8554]

Full frame is probably required to fit as much of the moon in frame as possible, but for small objects like planets you should use the smaller ROI.

Michael