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ZWO ASI 294 MM PRO: First impressions and test images.

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474 replies to this topic

#451 DrGomer

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Posted 19 October 2020 - 12:33 PM

grids like patterns in raw subs is likely PRNU and is calibrated out with flats.  I see it clearly when taking flats but not at all with calibrated images nor in stacks.



#452 tdastrup

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Posted 19 October 2020 - 12:56 PM

tdastrup,

 

   Which program did you use to capture the images you recently posted in #444 and #446? In addition, did you use the ASCOM driver or the native driver for connection to the camera?

 

 

John

I used N.I.N.A. and the native ZWO driver.

 

What's up with the weird grid pattern in the background?

I don't see the grid in my stacked image... for some reason, uploading it here to cloudy nights added the grid pattern.

 

https://1drv.ms/u/s!...uOkk7A?e=qLUHbJ

 

EDIT:  I had to remove the image because it was too large.  Here's a direct link to the image instead.


Edited by tdastrup, 19 October 2020 - 05:03 PM.


#453 xonefs

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Posted 19 October 2020 - 12:59 PM

So have they offered any indication if they will work on unlocking unbinned full readout or no?


Edited by xonefs, 19 October 2020 - 01:01 PM.


#454 jdupton

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Posted 19 October 2020 - 01:11 PM

tdastrup,

 

   Thanks for the additional information. I was curious about the grid pattern but see now that it is simply an artifact of the resize process for posting to CloudyNights.

 

   The full size Sii Bubble image you posted looks good. The background is good and there is no hint of any residual amp glow that is seen in the raw subs. That says your calibration process is working perfectly. You are well on your way to a very nice image.

 

 

John


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#455 StevenBellavia

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Posted 19 October 2020 - 03:04 PM

Hi,

 

I tried to search all 19 pages of this thread (so far), and it seems nobody has mentioned that the 294MM has 1/3 the dark current as the 294MC, at least according to the ZWO specs.

 

But I may have missed it.

 

Steve

Attached Thumbnails

  • 294MC_vs_294MM.jpg


#456 khursh

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Posted 19 October 2020 - 04:24 PM

Looks not quite 1/3 to me. Slightly different scales on the charts. 294MC goes to -15 on the chart, while 294MM goes to -20. At -10, the 294MC is just above .00781 and the 294MM is slightly below.



#457 Caprica

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Posted 19 October 2020 - 04:26 PM

Looks not quite 1/3 to me. Slightly different scales on the charts. 294MC goes to -15 on the chart, while 294MM goes to -20. At -10, the 294MC is just above .00781 and the 294MM is slightly below.

agree.

The dark current is the same.



#458 StevenBellavia

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Posted 19 October 2020 - 04:40 PM

agree.

The dark current is the same.

That is not what the data shows.

 

Maybe not the 3X I had incorrectly stated at the same temperature, but about 1.5X to 2X

 

The green lines are the same dark current value, the red lines are the same temperature (-15C)

 

Also note the that ordinate axis is not linear.  It is a doubling of the value at each major division.

 

Though they do seem to converge.  At +10C, the values are the same.

 

.

Attached Thumbnails

  • 294MC_vs_294MM.png

Edited by StevenBellavia, 19 October 2020 - 07:08 PM.


#459 Caprica

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Posted Yesterday, 12:50 AM

no, the graphs are the same. Only the ordinate for 294MM shows lower values (like Kevin mentioned in post #456). But that has no influence on the results. You see for example for -15°C both are on 0.00391 but this is not written on the 294C ordinate.



#460 Octans

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Posted Yesterday, 01:46 AM

no, the graphs are the same. Only the ordinate for 294MM shows lower values (like Kevin mentioned in post #456). But that has no influence on the results. You see for example for -15°C both are on 0.00391 but this is not written on the 294C ordinate.

Doesn't look that way to me. 0.00391 isn't labeled on the left because it's off the bottom of the plot and is the next major tick down. Tick labels otherwise match across the two plots.


Edited by Octans, Yesterday, 01:47 AM.

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#461 StevenBellavia

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Posted Yesterday, 08:06 AM

no, the graphs are the same. Only the ordinate for 294MM shows lower values (like Kevin mentioned in post #456). But that has no influence on the results. You see for example for -15°C both are on 0.00391 but this is not written on the 294C ordinate.

I am sorry, but that is incorrect. 

Please examine the graphs and the colored lines I have drawn in.

The dark current value of 0.00781 corresponds to -12C for the 294MC and -8C for the 294MM.  That is easy to see.

The actual dark current value for -15C is difficult because of the odd scale they used, but as Octans said (post #460), the next major division down for the 294MC would be .00391, and not where the red line I drew in is crossing.

 

Both graphs are using the same ordinate, with the same values, each a multiple of 2X.

The 8 subdivisions in-between, represent 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8 and 1.9, very similar to a log scale.

So you take the previous (lower value) major division and multiply it by the 1.2X, etc., to get the value, depending where it crosses.

 

I have attached what the values are for -10C and -15C for both cameras.  They are not the same. (But not as different as I originally thought.  Only a factor of 1.3X at those two temperatures).

Attached Thumbnails

  • 294MC_vs_294MM_subdivisions_2.png

Edited by StevenBellavia, Yesterday, 10:46 AM.


#462 Caprica

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Posted Yesterday, 09:05 AM

Yes, I was wrong. 

After a deeper look I see, somewhere below -7°C the values start to differ. 

This ist because the 294C curve is not more linear in this low region but maybe this is an error and it should be linear?

CS


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#463 Peregrinatum

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Posted Yesterday, 09:21 AM

I don't see any grid patterns in my raw subs, but there is some horizontal banding that comes out just fine after calibration and integration.



#464 StevenBellavia

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Posted Yesterday, 10:46 AM

Yes, I was wrong. 

After a deeper look I see, somewhere below -7°C the values start to differ. 

This ist because the 294C curve is not more linear in this low region but maybe this is an error and it should be linear?

CS

I was wrong about my initial claim of 2X to 3X.

I could ask ZWO.  They are always very helpful.  I just sent them an email.

But I suppose 30% is not a big enough error to worry about.


Edited by StevenBellavia, Yesterday, 10:55 AM.


#465 jdupton

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Posted Yesterday, 11:37 AM

Steve,

 

Hi,

 

I tried to search all 19 pages of this thread (so far), and it seems nobody has mentioned that the 294MM has 1/3 the dark current as the 294MC, at least according to the ZWO specs.

 

But I may have missed it.

 

Steve

 

ASI294_MC_vs_MM.jpg

 

   There are some minor differences between the two plots which become more significant at lower temperatures. I think this is a case of differing test conditions used by ZWO when they characterized each camera.

 

   If you compare the dark current at temperatures above 5°C, then the differences between the MC and MM cameras are quite small. At lower temperatures, the differences begin to increase. I note that the MM plot goes down to -20°C while the MC plot only goes down to -15°C. ZWO has explained before that the reason the MC plot only goes down to -15°C was because that was as low as they could go when they tested the camera. They further explained that the testing was done in warm ambient temperature conditions in the lab. The TEC Cooler was maxed out and could not cool below -15°C when they tested. This can be seen in the plot as a non-linearity where the curve begins to flatten below 5°C and is becoming significantly flatter below -10°C.

 

   Since the MM plot does go all the way to -20°C, it implies that the newer camera was tested under different conditions. Both the MC and MM cameras are specified to cool to -35°C below ambient.

 

   This is pertinent because the LGA packaging of these sensors comes into play along with placement of the thermal sensor. The cameras can be sensitive to self-heating effects as TEC power increases. Whenever the camera's TEC cooler pulls heat away from the sensor faster than the meager fan in the camera can dump that amount of 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 via its back side and heating it at the same time through its electrical pins around the periphery. The heat at the periphery is being conducted from the camera body to the PCB and then to the sensor's edges. This can cause an average increase in the temperature of the sensor compared to the cold-finger where the thermal sensor is located. The increased temperature at higher TEC Power usage is reflected in the dark current being measured. (BTW, this camera self-heating effect can happen on any sensor that uses a ceramic LGA package.)

 

   I run my ASI294MC 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 (measured at the area of the sensor / PCB) 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%. The delta temperature between the camera case and the surrounding ambient air rises quickly as the TEC power goes up.

 

post-160007-0-20185100-1592249197.png

 

   I think the self-heating effect at high TEC power usage when going for lower temperature set-points accounts for the nonlinearity seen in the MC plot from ZWO. For my MC camera, this effect actually kicks in at about 25% TEC power but doesn't become significant until about 50% TEC power. At 100% TEC power, the camera case is a full 8.5°C warmer than the ambient air around the camera. This heat is also being conducted to the sensor giving an incorrect view of dark current. By testing at a lower ambient temperature and not maxing out the TEC power, a more accurate view of dark current will result.

 

   I think the MC and MM versions of the ASI294 are probably very similar if not the same in terms of Dark Current at any given temperature. The ZWO plots may show otherwise but without repeating the tests under similar conditions, we don't know how much, if any, of the difference is real.

 

 

John


Edited by jdupton, Yesterday, 12:18 PM.

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#466 xonefs

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Posted Yesterday, 08:13 PM

Well I ordered one. Would like a 2600mm or 6200mm eventually but need something to hold me over until then

 

If they unlock unbinning though it might be a long term keeper


Edited by xonefs, Yesterday, 08:14 PM.


#467 Dean J.

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Posted Yesterday, 11:15 PM

Enjoy.  The ASI294MM appears to be a great camera and a step up from the ASI1600.  I am waiting for the ASI2600MM because it fits my situation better.  In the meantime I am having fun with my ASI2600MC.  I am starting to think I don’t actually need the mono version anytime soon.  



#468 xonefs

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Posted Today, 10:17 AM

I got 36mm filters for the 294. I wonder if 36mm filters would work if I got a 2600mm later. I dont even know if the zwo 36mm efw will hook up to the larger body but maybe they could be adapted for the 2" wheel.



#469 nfotis

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Posted Today, 10:39 AM

I got 36mm filters for the 294. I wonder if 36mm filters would work if I got a 2600mm later. I dont even know if the zwo 36mm efw will hook up to the larger body but maybe they could be adapted for the 2" wheel.


According to the CCD calculator here, 36mm filters should be enough up to APS sensor size:

https://astronomy.to...ccd_filter_size

N.F.

#470 xonefs

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Posted Today, 12:01 PM

According to the CCD calculator here, 36mm filters should be enough up to APS sensor size:

https://astronomy.to...ccd_filter_size

N.F.

yeah it's just a question of how to hold them. the 2" filter wheel isn't meant to attach to the smaller zwo bodies like 294 according to zwo, so guess the same goes for reverse on the 36/1.25" wheel. would need some custom adapters unless they come out with something



#471 Dean J.

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Posted Today, 12:16 PM

No problem with putting 36mm unmounted filters in a ZWO filter wheel.

I use the 7 slot ZWO EFW with my set of 36mm unmounted filters.

It has the M42*0.75 threads.

If I had an ASI294MM it would just screw into the filter wheel like I do with my ASI1600MM.

My ASI2600MC has female M42 threads on its front plate and I am assuming that the forthcoming ASI2600MM will be the same. So, I expect to be able to connect the 7 slot ZWO EFW to the new ASI2600MM with an M42 male to male coupler.

Edited by Dean J., Today, 12:18 PM.


#472 xonefs

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Posted Today, 12:29 PM

ok that's good to know. I ordered the 7 slot 36mm wheel so it would be nice to be able to just swap everything to a 2600mm if I decide to when it comes out



#473 mmatze239

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Posted Today, 01:40 PM

Hi guys,

 

this is my first post on this forum. Since here in Europe are only a few ASI294´s available I couldn´t find any support at our Forums.

Mine was comming in yesterday. Because the weather is bad I started to take the Dark libary.

I made 60-450 sec Frames 30 each with APT, cooling Temperature set to -16°C.

During the Dark Frames I see that the APT Temperature is always switching from -16.1 to -15.4 at the cooling aid.

The ambient temperature was approx 10°.

I´m wondering if anybody had seen somthing like this before?

With my ASI183 Mc Pro it was never a problem and the temp. was always constantly to the setting point.



#474 Lead_Weight

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Posted Today, 05:05 PM

Hi guys,

 

this is my first post on this forum. Since here in Europe are only a few ASI294´s available I couldn´t find any support at our Forums.

Mine was comming in yesterday. Because the weather is bad I started to take the Dark libary.

I made 60-450 sec Frames 30 each with APT, cooling Temperature set to -16°C.

During the Dark Frames I see that the APT Temperature is always switching from -16.1 to -15.4 at the cooling aid.

The ambient temperature was approx 10°.

I´m wondering if anybody had seen somthing like this before?

With my ASI183 Mc Pro it was never a problem and the temp. was always constantly to the setting point.

I've seen the temperature fluctuate on all my ZWO cameras. Usually only 1 degree or so. But especially as the camera begins to heat up when taking images. A small amount of fluctuation is not a big deal.



#475 Peregrinatum

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Posted Today, 05:18 PM

I was interested to see how the larger pixels would do with a smaller object... NGC40 74" major diameter, 0.41 image scale

 

JcQGl4cl.jpg


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