Jupiter only grey scale

Discussions of using SharpCap for Planetary Imaging
User avatar
turfpit
Posts: 1779
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: Jupiter only grey scale

#11

Post by turfpit »

Set the Brightness to 0, this will push the histograms over to the left. here should be no gap at the left as your image has a lot of black space.

What exposure is the last video captured at?

What are the min and max values of gain (maybe find out on a non-tablet).

11fps for a USB3 is poor - is the camera connected directly to the PC (tablet?).

The last SER video is starting to look how I would expect a Jupiter capture to appear.

Dave
Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Re: Jupiter only grey scale

#12

Post by Buckrogers »

Exposure=87.9904ms
Min gain is 100
Max gain is 383
Yes the camera is connected directly to the PC
User avatar
turfpit
Posts: 1779
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: Jupiter only grey scale

#13

Post by turfpit »

The exposure is too long, that will result in a lower frame rate. I suggest:
  • Set the brightness to 0. The will shift the histogram to the left.
  • Try gain values of 230 up to 300. These are 60% - 80% of max gain.
  • Turn on the histogram from the toolbar and check the logarithmic box.
  • Adjust exposure until right hand side of histogram is around 60%
  • Post a screenshot of this capture in Sharpcap + the camera settings file.
The logic is exposure affects fps. If the gain is increased then the exposure can be decreased resulting in higher fps. Don't worry about high gain with planets.

There is another sinister side to this - the selection of 640x480 is a ROI and the camera is still capturing the full 3872x2072 of the NexImage 10.

Dave
Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Re: Jupiter only grey scale

#14

Post by Buckrogers »

Thanks Dave, next time I have clear skies will try it out and reply back.
User avatar
turfpit
Posts: 1779
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: Jupiter only grey scale

#15

Post by turfpit »

Maybe try this is the daytime:
  • Focus on a land based object using some suitable gain & exposure
  • Set capture area to maximum, record the FPS shown in the bottom left of the SharpCap information bar.
  • Reduce the capture area and note the fps
  • Repeat until down to 640x480
.

Lets see what comes out of that .

Dave
Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Re: Jupiter only grey scale

#16

Post by Buckrogers »

Actually that's a good idea to try it in the daytime.

When you say repeat until down to 640x480, I normally start at the max and when I have the object in view, I go down to 640x480 and use ROI to adjust. Is that a bad thing?
User avatar
turfpit
Posts: 1779
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: Jupiter only grey scale

#17

Post by turfpit »

I normally start at the max and when I have the object in view, I go down to 640x480 and use ROI to adjust. Is that a bad thing?
No. It is just one way to do it.

I wanted to see what happens to the fps as you step down from maximum capture area to 640x480.

Trying things out by day (when practical) saves wasting those clear night opportunities.

Dave
Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Re: Jupiter only grey scale

#18

Post by Buckrogers »

Hey there,

So I focused on an object during the day. When I was at max resolution, I was getting below 10 fps. When I switched to 640x480, I was getting between 50 and 60 fps.

Last night, I captured Jupiter (files attached). I couldn't go lower than 31 ms for exposure, otherwise it would be too dark. Same with the gain but I was getting about 30 fps. Ran for about 5 min capture. I did forget to focus when I swapped my eyepiece for the camera, doh. So it was blurry

Tried another attempt (this time focused after I swapped eye piece with camera), was getting about 15 fps at 63 ms (again, couldn't down further or image would be gone)
Attachments
19_06_29.PNG
19_06_29.PNG (239.61 KiB) Viewed 999 times
18_58_36.PNG
18_58_36.PNG (427.04 KiB) Viewed 999 times
19_06_29.Histogram.csv
(4.86 KiB) Downloaded 60 times
19_06_29.CameraSettings.txt
(703 Bytes) Downloaded 62 times
18_58_36.Histogram.csv
(5.13 KiB) Downloaded 66 times
18_58_36.CameraSettings.txt
(703 Bytes) Downloaded 67 times
User avatar
turfpit
Posts: 1779
Joined: Mon Feb 13, 2017 8:13 pm
Location: UK
Contact:

Re: Jupiter only grey scale

#19

Post by turfpit »

So I focused on an object during the day. When I was at max resolution, I was getting below 10 fps. When I switched to 640x480, I was getting between 50 and 60 fps.
This proves that reducing the capture area increases the fps - that is working correctly.

Looking at 18_58_36.cameraSettings: SER, RAW8, 640x480, gain=383 and brightness=0 are all sensible choices. That leaves the exposure at 31ms (which gave 31fps). For 19_06_29 an exposure of 63ms gave a frame rate of 15fps (double the exposure halved the frame rate, which is consistent).

I think you are using reasonable camera settings now. The start of the post shows the camera is capable of 50 - 60 fps. The land based fame rate is not translating into the planet capture frame rate - I am missing something here.
  • Are you using a Barlow or any filters?
  • Is there anything else in the optical train?
  • What telescope is being used?
  • What is your latitude?
  • What is the approximate elevation of Jupiter.

This is a typical Jupiter capture for me using a Celestron C8 SCT and ZWO ASI120MC USB2 camera plugged into a USB2 port, captured at 53°N with Jupiter around 20°elevation. Note the camera settings - I have brightness=0, the gain is at 70% (70 out of 100). The exposure of 2.71ms puts the right hand side of the histogram at around 60% saturation and results in a capture speed of 44.5fps.

ASI120MC-with-C8_SCT.JPG
ASI120MC-with-C8_SCT.JPG (59.22 KiB) Viewed 992 times


Note that the screen shot of a capture in progress tells me everything I need to know.

Dave
Buckrogers
Posts: 78
Joined: Wed May 13, 2020 2:22 pm

Re: Jupiter only grey scale

#20

Post by Buckrogers »

Not using Barlow and/or filter
My latitude is 45 degrees N
Using a Nexstar 4SE
Approximate elevation for Jupiter is about 29 degrees
Post Reply