8.5.2020 Camera noise!

[Rusted]

Hi,

My ASI174MM has reached 43C. It shows in the snow.

The coloured image is after ImPPG has almost rescued it.

The B&W is a screen capture from AS!3's window. The noise is horrendous!

The third image captured a lucky bit of steadier seeing.

Note the rippled background over which the image seems to be "projected."

 

Edited May 8, 2020 by Rusted
add image

[michael.h.f.wilkinson]

Actually, I am not sure this is just camera noise or photon noise. You need to look at darks to see if this is the case

[Rusted]

3 hours ago, michael.h.f.wilkinson said:

Actually, I am not sure this is just camera noise or photon noise. You need to look at darks to see if this is the case

Thank you Michael.

Perhaps you would be kind enough to explain how I "look at the darks?"

There seems to be an option in SharpCap under Capture.
I use this for "flats" but haven't yet delved into the murky world of "darks." [Until now!]

Well, I just captured a "dark."  The file opens in Gimp. With which I have zero experience. All I see is a plain black rectangle.

Must the "dark" be captured at the same time as the image video and the flat?
Perhaps to ensure the camera is at the same temperature for both?

I'd better do some online homework on this "dark" matter before I break something! 

An UPDATE: Here is an excellent description of darks particularly related to SharpCap:

Capturing and Using Dark Frames

 

Edited May 8, 2020 by Rusted
update

[michael.h.f.wilkinson]

Taking darks just means taking a series of exposures at the same settings as the "lights", but with the camera shut off from all light (simply put a cap on the scope). Darks can then be stacked into a master dark, which can then be subtracted from the lights, to correct for the signal the camera produces in the absence of light. Even though the temperature of the sensor is high, each exposure is very short, so little dark current may actually build up in that time. 

[richard ashbee]

Have you tried any noise reduction software?

[Rusted]

45 minutes ago, michael.h.f.wilkinson said:

Taking darks just means taking a series of exposures at the same settings as the "lights", but with the camera shut off from all light (simply put a cap on the scope). Darks can then be stacked into a master dark, which can then be subtracted from the lights, to correct for the signal the camera produces in the absence of light. Even though the temperature of the sensor is high, each exposure is very short, so little dark current may actually build up in that time. 

Thank you Michael. If only it were that simple reaching the objective to cap it.
I have been practising with flats with a hat-like cell. Now I need to add capping to my repertoire.
A small, 18" high, stepladder has already been added to the observatory furniture so I can reach for flats.

A daft question: Can the darks be captured after the lights and flats?
I don't want to lose the small region of interest when dealing with a 3m focal length and small frame size. 

I may be misunderstanding the required order. If there is a fixed one.
Flats require a change of gain or exposure which then have to be returned to the lights settings.
It would be so much easier to capture the lights first. Followed by the darks and flats.
Then it won't matter if the telescope is disturbed slightly by the capping and/or fitting and removing the flat cell on tip-toe.

Moving the telescope is very undesirable when capturing a prom if it requires re-centring the ROI.
Made worse by SharpCap covering half of the capture screen.

[michael.h.f.wilkinson]

You can take darks at the end of the session. No problem 

[Rusted]

45 minutes ago, richard ashbee said:

Have you tried any noise reduction software?

Thanks Richard.

No. I have heard of it but not dabbled. A free option would be good to get a feel for what  is possible.
I am searching around the subject to see what is available. I shall try darks first.

[richard ashbee]

Topaz De Noise is one of the best but you have to buy it

[Freddie]

You shouldn't be getting any heat through the scope so just take the cam off the scope, leave it in the sun and cap it to take the darks. The darks should just be used to help determine where the problem is and not be used as standard during processing so it is a bit of a one off testing thing really.

Although noise reduction may help, it isn't getting to the root cause of the problem as your cam should not be that noisy so best to sort that rather than try and work round a problem that shouldn't be there. 

[Rusted]

Thanks again Freddie. I was imagining having to do a dark and a flat for every single capture.
Rod operated, flip-top, hinged objective lids, with a dark cap and a flat screen were being examined as the next project.

I believe Alexandra has mentioned having very similar noise problems with her own ZWO ASI174.
She reports that other manufacturer's versions, using the same chip, do not exhibit such noise. Basler, et al.

My ZWO ASI174MM has developed noise and a coarse grain over time.
It now shows up on lunar captures as well in very cool conditions. Making it worthless for that purpose.
When I first used it on the Moon it could capture Plato craterlets. Not any more!

One dealer wants me to send him examples of my affected images on the ZWO ASI120MC.
These will be forwarded to ZWO and then a return address provided once the fault has been diagnosed.
This sounds very time consuming!

The ASI174 came from a well known, UK dealer. I have not contacted them yet.
I was hoping to find a workable solution here first. To avoid losing what fills all my days and months in isolation.

With two ZWOs cameras now all but useless I should be looking for a far more productive [and far cheaper] hobby!
I have huge amounts of time and effort invested in building my observatory and its equipment.
Not to mention the considerable expense. Fortunately it was hugely rewarding. Until now.

[Freddie]

Sounds like you still have some experiments to perform to narrow down the cause as it is obviously not just temperature related.

Have you tried swapping cables and reinstalling drivers?

I have been using my 174 and 120 for solar (and planetary) for years without problems so it is not a fundamental fault with the cams.

[Rusted]

Thanks Freddie.

Swapping cables had no effect.

Not even thought about drivers. Until now.

I'll be back.

 

[Montana]

Yep, your prominence is full of little dots. All my images are full of little dots and it puts me off using it. I have to use very aggressive de-noise on all my images to get rid of them. I thought I was just being useless and maybe not stacking enough, but I have never seen others having this problem you see. I regret not spending the extra couple of hundred for the Grasshopper or Basler version  

Now I see your prom image, it does look like mine. However I don't see a weird condensation look when in live view like you showed before. All my grain comes when I try to post sharpen the stack. I have tried no gain vs some gain and it is still just as bad. Even stacking more and the dots are still there but the detail of the image are lost. With my Grasshopper (different chip) I can stack as low as 20-50 images and still not have dots, for the ASI174 I have to stack more than 300 to be even reasonable which is not an option for hires work. Good luck!

Alexandra

[Kitsunegari]

what are your actual exposure , gain, and gamma settings?   If you are using alot of gain, this is where the noise is from.  If you are using 0 gamma(at least in fire capture), this is also going to cause the noise.

 

If your setup requires you to crank up the gain its entirely possible you need a different blocking filter that lets a bit more light through, almost everyone needs to crank up software settings to get prominences to be exposed; but there is an extent to where you will not see something on the live screen that still is completely visible in the actual recorded data.

 

Try experimenting with a capture; where the live view does not show anything then take a sneak peak at the recording.  I have been quite surprised by this myself, thinking that i did not capture the data because it was not visible on my monitor ; but then was delighted to see the recording actually did contain everything.  

 

The mindset of "having to see" with our eyes on the screen does not necessarily apply to what the camera actually captures.

 

Indeed it could still be "ccd bakeout" however, so i will not discredit the 43c temp idea.