occulation

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John Whitehead
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occulation

Post by John Whitehead » Mon May 18, 2020 12:26 am

Just thinking,
could a occultation feature be included into Sharpcap.

Thanks John.

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admin
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Re: occulation

Post by admin » Mon May 18, 2020 6:34 pm

Hi,

I'm afraid I don't quite get what an occultation feature would do – can you elaborate?

Cheers, Robin

John Whitehead
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Re: occulation

Post by John Whitehead » Wed Jun 24, 2020 12:42 am

Dear Robin,
I compiled quite a note to you on what I mean by my Occultation message. I put it in the save draft and now cant locate it.

This occultation routine I have is in a Gstar camera quite old. But very useful.

I no longer use the Gstar camera. I have replaced it with a Gstar EX4 this doesn't have the Occultation function.
I have for my Astronomy mainly ZWO cameras, ASI 120mm, ASI 120mc, and a ASI 294 pro.

The use I have for a occultation routine is for viewing parts of the Suns surface where you need to block very bright over taking flairs from the image.
Viewing the Horsehead nebula where brilliance from brilliant Mintaka over whelms most of the image.
Viewing the pup of brilliant Sirius. I have built a eyepiece with a occultation bar works great.

A occultation function in Sharpcap turning off some pixels would be very useful. Just by moving the brilliant area out of the image isn't the same as actually blocking the offending light.

What's necessary is to be able to select a number of pixels to be turned off. Able to select the number to make a occultation bar and be able move the position as well as orientation.

Kindest regards,
John Whitehead.

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oopfan
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Re: occulation

Post by oopfan » Wed Jun 24, 2020 1:10 am

John,

I'm always open to new ideas, so let me ask, have you tried testing your theory? For example, take 10 frames of Sirius, and then before stacking, edit each frame and erase several of the saturated pixels at the star's center? After doing that what does the stacked image look like? Does it improve your ability of seeing Sirius B?

Brian

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Menno555
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Re: occulation

Post by Menno555 » Wed Jun 24, 2020 2:48 am

In theory couldn't that be done with a RONI: Region Of Non Interest? Or PONI (Pixels Of Non Interest (if those names are catching on, I want the rights to it :) )
No joke ... I mean, a ROI is a camera capable something. Wouldn't it be possible to device a kind of anti ROI, a negative ROI?
Sounds maybe stupid the way I describe it but I don't know all the technical terms :)

Menno

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oopfan
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Re: occulation

Post by oopfan » Wed Jun 24, 2020 3:31 am

Let's give John a chance to run experiments.

Like John says, an "occultation bar" is the best solution because it prevents the intense photon flux of the star from striking the sensor, but I am skeptical that an "anti-ROI" function is that helpful. After all, the thing that causes a bright star to balloon out is the spilling of electrons from saturated pixels to surrounding pixels. Erasing the few pixels at the star's center after the frame is captured does not reverse the damage to surrounding pixels.

Brian

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Re: occulation

Post by admin » Wed Jun 24, 2020 3:50 pm

Hi,

certainly anything that could be done in software in SharpCap is far too late to affect things like blooming or star spread in the image – that is in the data way before it gets as far SharpCap. What you could do is have an option to set fully saturated pixels to black (for instance). The only effect that would have is on the way that your eye brain process the image on screen. If you have for instance a bright star in the image that is annoying you, you would attain exactly the same effect by holding a piece of black card over that star on the monitor.

I think I'm with Brian at the moment that I'm still needing to be convinced by this.

Thanks for the explanation, Robin

John Whitehead
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Re: occulation

Post by John Whitehead » Sat Jun 27, 2020 1:56 am

Can I start thanking for those comments and ideas.
Its certainly put my brain back into gear.
I'm 78 years old so all this mental exercise is good for the gray matter.

Ok this occultation is some thing I have been playing with ever since I saw it work with the Gstar ex mono camera.
I do a lot of work watching the Sun for solar winds, my Gstar-ex camera's occultations routine has collapsed, so now I'm busy trying to reinvent it again
using other cameras.

Yes if I could find a way of switching off, or switching to black selected pixels in the camera forming a controllable bar that can be moved around the image to block over bright protons, similar to that of the controlling the ROI. That would prevent them from overflowing into adjacent pixels.

I don't understand much of how a camera works.

I stated before I have constructed a controllable bar in a eyepiece. This works almost beyond belief. But I have failed to introduce the same contraption in front of a camera.
John.

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Re: occulation

Post by oopfan » Sat Jun 27, 2020 3:09 am

Hi John,

When you say "my Gstar-ex camera's occultations routine has collapsed" what does that mean? I have a software background so the word "routine" refers to a program component but the word "collapsed" doesn't make sense in this context.

Brian

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Re: occulation

Post by oopfan » Sat Jun 27, 2020 4:13 am

John,

I searched the Internet for "Gstar-ex" and "occultation". Very few results. Basically people using the camera to record a star passing behind the Moon.

Then I searched for "occultation bar". Again just a few results. Basically people adding a thin strip of metal in the focal plane of an eyepiece. This particular gentleman used it to block the light from Mars so that he could view Mars' moons.

John, are you talking about doing something like this:
https://spaceweather.com/images2020/25j ... e_anim.gif

They are using a physical obstruction to prevent the intense solar flux from striking the camera's sensor. If they were to remove the obstruction then the sunlight would overwhelm the entire sensor. The entire frame would be white. Are you using special solar filters? Tell us more about it. Can you share some photos you've taken?

Brian

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