136 replies to this topic

[andysea]

Here is the same image with no flats applied, only darks. After DBE to mitigate the vignetting. I see the same artifact.

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[wenjha]

Hi Andy

I suspect this maybe because the dark cannot fully match the light

can you try take darks immediately after light ?

[andysea]

Out stretch clear weather has ended so I can’t do any more testing for a while.

[bikerdib]

I thought the main reason people want the 294 is for NRTV?  That is the reason I chose it over the QHY163C or ASI1600MC,.  When I was upgrading from my Infinity color I first bought a QHY163 color/cooled but after the first use I decided I wanted the more sensitive 294 color/cooled and luckily High Point understood and gave me my money back on the QHY so I was only out the shipping.  I'm still learning the best settings to use with Sharpcap but so far I'm happy with the swap.

Edited by bikerdib, 20 March 2018 - 07:58 AM.

[andysea]

I don't know why people buy the 294 but I bought it because it was inexpensive and on paper the specs looked very good. I wanted a camera that I could take with me when I travel and that would be better than my DSLR. I also have the QSI 532, the Moravian 16200 and the ASi183 which are all monochrome cameras so I can go back to using one of them. I did like how simple the 294 was to use, especially with a fast instrument.

I have not received any suggestions for a resolution or offers to test the camera from ZWO which is pretty disturbing and I think people should take that into account when deciding which camera to buy. I bought the camera from Agena and they have not returned my emails either, except for the first email that I sent them.

[bikerdib]

I've never dealt with ZWO directly but I am a little surprised that Agena isn't responding.  They usually have top notch customer service.  Maybe they aren't able to get a response from ZWO about the issue either.

[bikerdib]

BTW, I certainly was not questioning your decision to buy a 294.  Unfortunately, sometimes with cameras intended for astrophoto, the only way to find out is to try.

[andysea]

Yep isn’t that the truth!

Btw I got an email from Agena. They will do whatever zwo deems necessary.

[neaptide]

The fact that ZWO is aware of the issue you and others are having with this camera and only gives short 10 word responses is disturbing ineed. I am very disappointed because I was only a few weeks away from buying this camera at NEAF. I will talk to Sam at NEAF and see what he has to say. I really thought this was going to be an excellent camera for both eaa and astrophotography. Now I'm not sure what I'm going to buy. This is a major purchase for me and I would like to know that there is going to be some kind of support if something goes wrong with my $1100 camera.

[bikerdib]

I don't think there will ever be a totally perfect camera that is capable of both high sensitivity, and low noise of all types.

 

Of course, soon as I type this...LOL

 

Andy, at least Agena is following up but I guess that unless they want to take the loss by refunding your money, their hands are tied by ZWO.  BTW, I followed your link to your Flicker account page; you have some AMAZING images posted.

[A. Viegas]

The ZWO 294 was originally marketed toward the EAA crowd.  The specs lend themselves to use as a very sensitive OSC camera as well.  However, as others have noted its rare to get a 'perfect' product that does everything you want it to do.  The 294 excels using very high gain which is great for EAA, but with such a large well its tempting to use it at very low gains and much longer exposures.  Assuming that the red glow is a critical flaw is well just one of the trade-offs in the 294 chip -- very high sensitivity -- with higher dark current and red sensitivity.   I don't think its fair to say its "ZWO's fault"   that is just not true, they are to be commended for always being willing to innovate and stay ahead of the curve.  If we did not have a ZWO pushing the envelope most of all the other camera manufacturers would be blithely churning out near-obsolete over priced CCD cameras.     

 

As for what to do...   well Sam will be at NEAF in 4 weeks.   He is going to hear about this issue and I imagine he and his team will try and address it best they can.  This is either an endemic problem with the sensor which ZWO cannot do anything about as it is what it is, or its a defect specific to Andysea's camera.   If the latter I am sure ZWO will address it and make good on the camera.   I have not used the camera below unity gain and I usually am pushing the gain much higher.   In fact it seems to me that this is an issue easily resolved by using higher gain.    Given all the evidence to date, it seems that using the 294 at unity or lower gains with offsetting very long exposure times is just not going to be very good, however, there is nothing wrong with using much higher gain and stacking just more frames, so maybe you are not getting the full well benefit of the camera but you are still way ahead of other OSC cameras in terms of FW.

 

Consider  at unity gain the FW of the 1600 based chips is like 8000e and the unity gain of the 071 based OSC is like 15,000e....  meanwhile unity gain for the 294 is about 27,000e 

 

Case in point.  Here are two images.

 

Rosette   180s at Gain 390  -- debayered calibrated frame with darks/bias no flats. --- notice  no red hue.

 

Thor's Helmet -  180s  but at Unity gain   (gain 117)  - debayered calibrated frame with darks/bias - no flats.    Notice  some RED here.

 

 

 

 

 

oh by the way... think about it... these are single frames, from a red zone....  3 min exposures...  this is what makes the 294 chip so good, its very sensitive!

 

Al

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Edited by A. Viegas, 20 March 2018 - 03:58 PM.

[andysea]

I don't think that what I am seeing is a glow but rather a rounded artifact that spans across the whole sensor. Don't you think?
Anyway that may very well be normal I just need someone to tell me so (Ideally ZWO), in which case I can make an informed decision on whether the camera is good for me or not.

[sarmen2]

Hello Andy,

 

From your post: Posted 15 March 2018 - 02:26 PM, you mentioned taking 0.5s duration flats. From what I understand, CMOS sensors with "global shutter" capability capture the entire pixel array simultaneously (light to charge conversion), then digitizes row by row for readout. This might allow for very short flat fame capture. I don't know for sure if Sony 294 has Global shutter.

 

I would keep flat frame captures to at least 3s to avoid any shutter effects even if the 294 supports global shutter mode. You might experiment with flat capture times and notice any differences. Probably will not change anything, but may be worth a try.

[andysea]

Ah! good suggestion. I do that with my CCD cameras, I'll try new flats tonight and see how it goes.

Edited by andysea, 20 March 2018 - 06:37 PM.

[andysea]

Well there you have it now I know that this camera has essentially uncorrectable dark current. 

Here is ZWO's explanation.

 

"I asked Sam about this issue. He told me something make sense.
The pattern is cause by heat of sensor. TEC is a little smaller than Sensor, so in long time use, center of sensor will have a little lower temperature than side of sensor.
So we recommand to take dark frames as soon as you finished light frames in one night."

 

I think I will sell it right away.

[Konihlav]

if that's the case then ZWO should take all cameras back and re-design and fix it for every camera sold. Sure, it is expensive, but a happy and satisfied customer must be always above any financial loss. We do, loss a lot when pioneering in trying a new camera out there (I did went that route plenty of times while searching for the holy-grail).

 

On one hand ZWO must be appreciated that they do new products quickly and move the market, allow everybody to afford cheap and very good performing cameras.

 

But on the other hand, I do not know of ANY camera maker who did not made mistakes or malfunctioning products in the past - EVERY maker did had some issues with some series. So this is nothing new. What matters is how it is dealt on the customer service side.

 

Sorry andy to hear about this.

 

BTW I am myself in a search of some mono solution (since I sold my G3-11000 I do not have any mono camera, because I also get rid of QHY163m just because I said no more qhy) and in the CMOS world there's still only ASI1600 that is a great performer (though the non AR coating of the cover of the sensor) and other CMOS cameras (SONY :-( ) do have always large amount of amp-glow...

therefore as summary, the old CCD is still a choice of some of us (like the newest 16200 chip).

[A. Viegas]

So I found an image from a few weeks ago when I was experimenting with the 294 at ZERO gain.   Here it is, the Elephant Trunk shot with my AT65  this is a 180s exposure at ZERO gain.  It is a single calibrated sub (just applied ABE) and I may have shot my darks right after the capture sequence, so maybe that is why - but there is NO RED BORDER here.

 

 

 

 

 

Al

[andysea]

Right. I have hundreds of such subs. Probably over a thousand at this point. Single exposures look fine. The issue only gets revealed once you stack several hours worth integration time.

[DonBoy]

Well there you have it now I know that this camera has essentially uncorrectable dark current. 

Here is ZWO's explanation.

 

"I asked Sam about this issue. He told me something make sense.
The pattern is cause by heat of sensor. TEC is a little smaller than Sensor, so in long time use, center of sensor will have a little lower temperature than side of sensor.
So we recommand to take dark frames as soon as you finished light frames in one night."

 

I think I will sell it right away.

Sounds like if a thin piece of aluminum or copper, the same size of the sensor or slightly larger, could be slipped in between the Peltier chip and the sensor that it may distribute the heat better.

[javaruba]

Well there you have it now I know that this camera has essentially uncorrectable dark current. 

Here is ZWO's explanation.

 

"I asked Sam about this issue. He told me something make sense.
The pattern is cause by heat of sensor. TEC is a little smaller than Sensor, so in long time use, center of sensor will have a little lower temperature than side of sensor.
So we recommand to take dark frames as soon as you finished light frames in one night."

 

I think I will sell it right away.

Hi Andy,

Now that you had your response from ZWO and if you sell the camera, which camera would you purchase afterwards? OPTCorp recommended me this camera as well since my budget is set at around $1k. Reading your post, I am having seconds thoughts.

 

Jairo

Edited by javaruba, 21 March 2018 - 04:48 PM.

[andysea]

I think that if you keep your exposures within 1 or 2 minutes you will be fine. Before I sell it I will try a new imaging run with 2 minute subs as others have suggested. The read noise is low enough to allow for that.

[javaruba]

I think that if you keep your exposures within 1 or 2 minutes you will be fine. Before I sell it I will try a new imaging run with 2 minute subs as others have suggested. The read noise is low enough to allow for that.

Sounds like a plan, keep us posted on the your tests.

[DonBoy]

I wouldn't sell this camera short.  If you are into EAA or Near Live Imaging you couldn't do better.   So if you're into EAA take a look at my working Flickr album.  AP guys stay out. LOL

 

https://www.flickr.c...157692230746941

 

And BTW there is a ROI bug resulting in warm pixels which they will be correcting in the next drivers,

[andysea]

Lol nice work! Ok i will give the 294 another whirl with shorter exposures.
I’m glad that we got to the bottom of the issue that I was seeing.

[MoonPrince]

Hi Andy

I download your 294pro images. All the light/dark/flat/bias frames of leo triple galaxies. My processing in Pixinsight 1.8 is like this:

1. Batch Preprocessing Script 1.46, put light/dark/flat/bias into it, calibrate and output calibrated light frames, master dark, master flat, master bias.

2. Debayber light frames.

3. Align light frames

4. stack light frames.

5. Background Neutralization

 

After thoes processing, I use STF auto-stretch, and I'm glad that it is looks good, I didn't think the image have any unacceptable issues:

 

Then I tried STF auto-stretch(boosted), a little gradient appears, does it is acceptable too? gays. In my DSO experience, this result is pretty satisfied for me.

 

If we need to get better calibration result, taken dark frames as soon as finished light frames will be a perfect way. Light frame and dark frame taken with same conditions, will have much consistent noise level.