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ASI294MC Pro Blotches

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#1 RayRaywasHere

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Posted 13 June 2020 - 05:14 PM

After several months of using a DSLR I decided I wanted to jump to a dedicated astro camera due to wanting a cooled sensor for long exposures and not needing a cooling off period between shots. I picked up a ASI 294 MC Pro about a month ago and have gotten lucky enough to try it on 10 different nights. The images I've gotten with it have look amazing except for I have blotches that that I cannot get rid of. I have tried dozens of combinations of calibration and I'm looking what to try next, besides send the camera back to ZWO

 

As seen in the M51 image, there is a red ring visible with a basic stretch. Besides the red ring, there are dark blobs across the image. M51 -red blob.jpg

 

I have tried the camera on two telescopes (a 6SE and a Spacecat 51) using an ASIAIR for the capture. I've tried with and without bias frames, with and without dark frames, and multiple attempts of flat frames ranging from 0.1s to 10s. I've tried getting flats from the morning sky, an iPad, a laptop screen, my OLED TV to cheap tracing pad. I've tried exposures from 3min to 30 seconds. Gains at 0 and 120.

 

Some things seem like they are helping and I have made progress on the red ring but the dark blob always returns somewhere in the processing. Some things have made the ring go away, but only to be replaced with the dark blobs being more visible. No matter what I've done, the dark blobs remain in the same spot... mocking me.

 

 


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#2 RayRaywasHere

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Posted 13 June 2020 - 05:18 PM

dark spot.jpg

The spot... always there and always the same shape.


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#3 nimitz69

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Posted 13 June 2020 - 06:44 PM

Bias typically won’t work with that camera since it doesn’t like extremely short subs which is what bias are. You need to use dark flats instead. Also getting good flats can be tricky at times. Many of those cheap light sources you tried do not produce even light. One or more of the channels (RGB)can be way off. I had blotchy issues when I had a 294MC pro using one of those light tracing panels. Got myself a spike-a-flat and never looked back

Are your darks matched to your lights in gain & exp time? Your flats should be somewhere around 25,000 - 32,000 ADU and then your dark flats are at the same exposure time as whatever your flats were. you can’t use flats by themselves, you must always include either bias or dark flats or the subtraction doesn’t work

Edited by nimitz69, 13 June 2020 - 06:50 PM.

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#4 GoldSpider

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Posted 14 June 2020 - 07:16 AM

Unfortunately this seems to be a characteristic of this camera.  If they come up with a replacement at a comparable price point that doesn't have this "feature" I'll probably trade up to it.  When I stretch, I usually get into the blotchiness before I get into read noise.

 

I've been able to minimize my blotches by taking flats (and dark-flats) that are at least 3 sec. long. 



#5 nimitz69

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Posted 14 June 2020 - 07:41 AM

Many, many people use the camera with great success. You just have to be careful with creating flats. Those cheap ePanels that became popular a while back do not work all that well. Once you create good flats you should be fine

Edited by nimitz69, 14 June 2020 - 07:42 AM.


#6 jdupton

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Posted 14 June 2020 - 10:41 AM

RayRaywasHere,

 

   Out of curiosity, what was your set-point temperature for the images you posted in Posts #1 and #2? I think temperature, or more specifically, the depth of cooling from ambient has a lot to do with issue you see with respect to the colors in the background. 

 

   In addition, the dark center and bright surrounding ring are artifacts I often see. I think they are due to residual vignetting and reflections in the imaging system that are not being completely removed by the flat fielding. If you are using PixInsight, the dark center and brighter ring often appear only after DBE and or ABE. It can be treated in DBE using a radial symmetry methodology followed by a more normal sample placement strategy. While you mention the optical systems used, I would also be curious to know whether your setup uses any filters (like Light Pollution or IR Cut) or any focal reducer or flattener near the camera.

 

 

John


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#7 elmiko

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Posted 14 June 2020 - 10:44 AM

Ray, my wife bought me this camera Last Christmas. I had the same splotches all over. Nothing I did would remove them. I sent it back to the store I got it from and bought the ASI 071 mcPro and didn't look back.

  Not trying to be negative. I really hope you can resolve it. Please keep us posted with what approach you take to remedy this.

By the way I did try dark flats at 5 second subs. Same splotches. Bias, no Bias ECT. ECT.... Sky flats, light panel flats...red splotches! To me it wasn't worth the hassle trying to figure it out. Never experienced it with any other camera.


Edited by elmiko, 14 June 2020 - 10:48 AM.

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#8 AhBok

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Posted 14 June 2020 - 11:23 AM

Same here as I have posted many times. I returned mine under warranty and got an 071. Someone recently posted a closeup if their 294 chip and the swirling/blotchy pattern was easily seen. I’m guessing you purchased used? It seems the newer cameras do not exhibit this.
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#9 ChrisWhite

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Posted 14 June 2020 - 11:36 AM

I'm surprised they still sell this camera. It has a fundamental design deficiency that causes this issue with many copies. Many people have no problem, but a too high percentage of people do. Yet they still sell it, and the people who have good copies keep promoting it on these forums. Not trying to be negative or cynical but that is the reality it seems with the 294.
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#10 RayRaywasHere

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Posted 14 June 2020 - 12:15 PM

RayRaywasHere,

 

   Out of curiosity, what was your set-point temperature for the images you posted in Posts #1 and #2? I think temperature, or more specifically, the depth of cooling from ambient has a lot to do with issue you see with respect to the colors in the background. 

 

   In addition, the dark center and bright surrounding ring are artifacts I often see. I think they are due to residual vignetting and reflections in the imaging system that are not being completely removed by the flat fielding. If you are using PixInsight, the dark center and brighter ring often appear only after DBE and or ABE. It can be treated in DBE using a radial symmetry methodology followed by a more normal sample placement strategy. While you mention the optical systems used, I would also be curious to know whether your setup uses any filters (like Light Pollution or IR Cut) or any focal reducer or flattener near the camera.

 

 

John

I've kept the temperature constant at -10 as that has kept the percentage well below 50% so far in Minnesota.  I've had a 0.63 reducer in line, but I've tried taking it out without impact. I've tried it with and without an Optolong L-Pro filter. With the filter installed, it actually got a bit better... but still the blotches remain.


Edited by RayRaywasHere, 14 June 2020 - 12:17 PM.


#11 elmiko

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Posted 14 June 2020 - 12:26 PM

https://www.cloudyni...ound/?p=9872369

You can read this.


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#12 RayRaywasHere

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Posted 14 June 2020 - 12:28 PM

Same here as I have posted many times. I returned mine under warranty and got an 071. Someone recently posted a closeup if their 294 chip and the swirling/blotchy pattern was easily seen. I’m guessing you purchased used? It seems the newer cameras do not exhibit this.

Camera is brand new which makes this extra painful. 

 

I'm heavily debating going the same route as several of you here and asking for ZWO to send me an RMA so I can go to the 071. 


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#13 elmiko

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Posted 14 June 2020 - 12:33 PM

Ray, click on the link I just posted above. You will see I was having the exact same issue. Mine was even worse than yours.

   I would call the company you purchased it from and demand an exchange. This is not your fault. Don't let them try to convince you that you're not calibrating correctly. There is something very wrong with this particular model. Not all but too many! Good luck, Mike


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#14 RayRaywasHere

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Posted 14 June 2020 - 12:50 PM

Ray, click on the link I just posted above. You will see I was having the exact same issue. Mine was even worse than yours.

   I would call the company you purchased it from and demand an exchange. This is not your fault. Don't let them try to convince you that you're not calibrating correctly. There is something very wrong with this particular model. Not all but too many! Good luck, Mike

Yeah... that looks really, really familiar but your is indeed much worse. If I pull the saturation really high I can see a pattern that stays fairly consistent regardless of scope, flat or other combination. 


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#15 elmiko

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Posted 14 June 2020 - 01:08 PM

Yeah... that looks really, really familiar but your is indeed much worse. If I pull the saturation really high I can see a pattern that stays fairly consistent regardless of scope, flat or other combination. 

So that should tell you that it is something inherent in the camera. I don't even think it has anything to do with electronic noise. I think it is some kind of physical contamination inside the sensor or sensor window. Maybe when these cameras were assembled in the factory one of the workers were eating cotton candy or something! Lol!


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#16 jhart

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Posted 15 June 2020 - 01:21 PM

I have a new ASI294MC P coming soon.  There seem to be quality control issues for the sensor and/or its mounting in this camera.  (Or maybe I am hoping that is the problem instead of just an inherently bad camera).  Several posts say they don't have the splotching, dark spots or other problems that have arisen.  Is there a more or less objective set of settings and parameters to use for test photos to determine whether this particular camera exhibits those unfortunate problems?


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#17 jdupton

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Posted 15 June 2020 - 02:34 PM

jhart,

 

   These are my opinions below. Others may disagree but I have done a lot of characterization work on my camera.

 

   There are two different issues being described by the OP (@RayRaywasHere). One is the odd Red "blotches" in the background as illustrated in the first post. From reports here on CN, that is a real artifact of the sensor. (I would stress sensor here and not camera in order to differentiate between a physical sensor issue and an electrical camera issue.) As discussed in the other thread linked here, this looks like some sort of interference effect due to something happening at the sensor cover glass or on the silicon itself. It can be photographed on the sensor without even turning the camera on or hooking it up. If you encounter this issue, it is probably best to exchange or return the camera. It's hard to judge how prevalent this issue is with this camera. Mine does not show the effect.

 

   The second issue the OP encountered is the dark spot near the center of the image after gradient removal in image processing. I have seen this on multiple different types of cameras when processing is done with PixInsight DBE or ABE gradient removal. This is not indicative of any sort of issue with the camera. It can be caused by the nature of the image and the gradient removal process. 

 

   I had asked OP about the temperature settings because you can get a completely different type of "blotchy" background with this camera when running the cooling system at 100% for long periods of time.

 

   Whenever the camera pulls heat away from the sensor faster than the meager fan in the camera can dump that heat to the surrounding ambient air, you will notice the body of the camera heating up. That excess heat that couldn't be removed can heat up both the camera body and the inside of the camera by conduction. The sensor itself is ultimately heated all the while you are cooling it. In this way, you are cooling the center of the sensor at the center of its back side and heating it at the same time through its electrical pins around the periphery as heat is conducted from the camera body to the PCB and then to the sensor's edges. This can cause a dark current gradient to form on the sensor. When you stretch the resulting images farther than the data can support in processing, this gradient can appear as large scale background mottling -- light and dark areas. This camera self-heating effect can happen on any sensor that uses a ceramic LGA package.

 

   I run my camera on the conservative side of the trade-off equation between cooling and self-heating. I cool to about 25° C below ambient and no farther. Below is how my ASI294MC-Pro camera responds to cooling. The TEC Power is plotted on the horizontal axis and both sensor temperature and the delta between the ambient air and the camera case are on the Y axis (with different scales). Note that at about 40% TEC power, I can reach 0° C and the case is only just starting to warm up. To reach another 10° C deeper cooling, the TEC power soars to 100%.

 

TEC_vs_SP+CAD.png

ASI294MC-Pro Sensor Temp & Case-to-Ambient Delta vs TEC Cooling Power.

 

 

John


Edited by jdupton, 15 June 2020 - 02:39 PM.

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#18 elmiko

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Posted 15 June 2020 - 02:44 PM

I would return the camera Ray.


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#19 RayRaywasHere

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Posted 15 June 2020 - 03:17 PM

Thank you everyone for the helpful insights. I was just in the return window for the camera, so I have chosen to send it back and go for an ASI 071 as recommend by elmiko and AhBok. I just dropped it off at the post office and I already found an 071 in stock elsewhere. 

 

I hope others have good luck with this model camera and I'm envious of what others have captured with it. The images I got were a step above what I got before... but I'd rather not take that step with plantar warts. wink.gif


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#20 jhart

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Posted 15 June 2020 - 04:36 PM

Ray,

 

Did you have a chance to inspect or photograph the sensor on the ASI294 as John suggested before you returned it?


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#21 RayRaywasHere

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Posted 15 June 2020 - 07:14 PM

I saw that in a thread previously and tried looking at mine.

https://www.cloudyni...661685-word-of-warning-asi294mc-pro-and-opt-triad-and-nb/

 

I couldn't get a good view of the sensor behind the glass and I wasn't planning on taking the front off a camera I was debating returning.  


Edited by RayRaywasHere, 15 June 2020 - 07:14 PM.


#22 cuivienor

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Posted 16 June 2020 - 03:16 AM

I am the unfortunate original reporter of that red blotchy pattern (the Word of Warning thread). Ray, you should indeed return the camera - do it now. Instead, I would highly recommend either the 2600MC Pro, the 071MC Pro, or the 533MC Pro.

 

The 2600MC Pro and 533MC Pro seem to be related and are both trouble-free, easy to calibrate cameras with no amp glow and high quantum efficiency (the ratio of photons that get converted into electrons, basically). The 533MC Pro is cheaper than the 294MC Pro, although you do sacrifice some field of view with it. You can check my review of it here, including a comparison with the 294 MC Pro: https://www.youtube....h?v=lfQ_tPoPaLk

 

The 071MC Pro, which I've also owned (and which replaced my 294), is excellent as well - a bit less sensitive, but it is a very well behaving sensor, easy to calibrate and deal with.

 

Good luck & clear skies. I hope you can get it sorted out!


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#23 elmiko

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Posted 16 June 2020 - 04:18 PM

Good news Ray! You will not regret returning the camera. Any of the other 3 models discussed will be hassle free choices. I have no problems whatsoever with my 071 mcPro. It just works. I take sky flats with a t shirt cover on the scope, usually .5 sec. Exposures. Nice flat, clean calibrated subs.


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#24 FrankSD

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Posted 17 June 2020 - 11:24 PM

Let me chime in with my very mediocre experiment.  I was so sure my ASI294 was defective, I bought a second one.  Turns out both yield a weird background pattern when stretched.  Since clear nights are a rarity, here's my cheesy experiment.  I covered the scope with a sheet of aluminum foil and punched some pinholes in it.  A galaxy, right?  Except that Televue didn't think to give the the ability to focus on the end of the dewshield.  So what you're seeing here is a blurry bit of lighting coming in the middle.  In PixInsight, I debayered, removed the background with ABE and did a basic Histogram Transformation.  I tried to give it a realistic stretch, not going into the curve.  What I found is that though there's a bit of discoloration and unevenness is the unfiltered shot, adding the new Triad Ultra Quad light pollution filter gives that weird background pattern I've been fighting with the old camera.  I got similar but different patterns using  Hutech IDAS D2 and P2 light pollution filters. 

 

So. . .I'm wondering how much of my problem has been due to light pollution filters.  Anybody?  Triad-15-sec-VNG-ABE-HT-small.jpg

 


Edited by FrankSD, 17 June 2020 - 11:25 PM.

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#25 FrankSD

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Posted 17 June 2020 - 11:26 PM

Here's the same camera, same setup but no filter. 

Attached Thumbnails

  • No-filter-1-sec-VNG-ABE-HT-small.jpg



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