1020 replies to this topic

[stryker66]

ZWO just shipped my ASI294MM today, I am not replacing my ASI1600MM and just wait for another one down the road. I do have the ASI294MC now and it seems pretty good, I just need the mono version for Luminance captures for galaxies, I just use the color for the RGB so I dont waste time with filters. This will be my dedicated pair for galaxies on RC10 F6.3 reduced at 1625mm FL. I am going to use this for the crab nebula and fireworks galaxy.

[Joe Bruessow]

Any idea as to when the first wave of these is going out to vendors?

[Grimstod]

The difference is that the mono has no Bayer filter matrix sitting on top of the sensor.

 

It's a _big_ difference.  <smile>  Bayer matrix filters are really a terrestrial device, and engineered for that specific purpose.  They're not horrible for AP (I use both types of cameras), but they are inefficient.  Particularly noticeable in light polluted skies.

 

Really, the only drawback to mono is the substantial cost of the camera, filters, and filter wheel.  Data acquisition is a bit more complicated, but (especially if you use LRGB methods) total imaging time for the same signal to noise ratio is less.  I think color is better, the Bayer matrix is sloppy, and some red and blue photons are recorded as green.  You can compensate some in processing.

 

All this is not to say people don't make lovely images with OSC cameras with Bayer matrix filters.

So well said I am book marking it. 

[MikiSJ]

 

bobzeq25:

 

The difference is that the mono has no Bayer filter matrix sitting on top of the sensor.

Both of the IMX492 chips, color or mono, have micro lens. The color chip has a RGGB filter below the microlens and the mono is clear.

 

https://micro.magnet.fsu.edu/primer/digitalimaging/cmosimagesensors.html

 

Here is the Sony data sheet: https://www.sony-sem...J_LQJ_Flyer.pdf

[bobzeq25]

Both of the IMX492 chips, color or mono, have micro lens. The color chip has a RGGB filter below the microlens and the mono is clear.

 

CMOS.PNGhttps://micro.magnet...agesensors.html

 

Here is the Sony data sheet: https://www.sony-sem...J_LQJ_Flyer.pdf

I wasn't including microlenses.  Just filters.  One is better than two.

Edited by bobzeq25, 24 September 2020 - 02:42 PM.

[Peregrinatum]

No worries about amp glow and calibration:  left is raw frame with amp glow, right same frame with calibration using flats that were flat dark corrected, and the master dark, below is the master dark

 

 

[Dean J.]

Right.  Attention to proper calibration always works.

[Peregrinatum]

Wow fellas, I am really impressed with this camera thus far... this is the "first light" image of the Bubble nebula, it represents 6 hrs of O3 integrated data from last night in  19.3 sqm skies... only processing was calibration and cosmetic correction...  So far I think this data is much cleaner than with ASI1600MM, and no micro lensing...  I need to get the rest of the channel data and process, but so far I am pleased and think the money is well spent!

 

Questions:

 

Why are my background adu values significatly higher with this camera (binning?)

 

How can I account for the binning when trying to estimate adu values to dilute RN by 10x?

 

[Lead_Weight]

Looks good. I got mine yesterday too, and am setting it up to image this weekend if we have clear skies. 

 

So, the ADU value is slightly higher compared to what? The 1600? This camera does have a higher QE, so you're getting roughly 30% more signal in each capture. Or are you saying the background black level isn't zero?

[calypsob]

do you need 2" filters or will 1.25 suffice with this camera? 

[Peregrinatum]

Looks good. I got mine yesterday too, and am setting it up to image this weekend if we have clear skies. 

 

So, the ADU value is slightly higher compared to what? The 1600? This camera does have a higher QE, so you're getting roughly 30% more signal in each capture. Or are you saying the background black level isn't zero?

With the ASI1600MM darks would have a median adu value of around 800 adu (16 bit), with the ASI294MM they are about 3200 adu (16 bit)... pretty sure it's due to the binning but just want to confirm.

 

When I use my usual values to calculate exposure for 10x RN I get about 600 adu, so somehow I am not accounting for the binning... the integrated image above has a median adu of 3500 (16 bit)

 

also, the raw files are smaller, 1600/32MB and with the 294/22MB, I was expecting them to be much larger because it is 14 bit

Edited by Peregrinatum, 25 September 2020 - 01:01 PM.

[barrabclaw]

With the ASI1600MM darks would have a median adu value of around 800 adu (16 bit), with the ASI294MM they are about 3200 adu (16 bit)... pretty sure it's due to the binning but just want to confirm.

At first I thought maybe it could be differences in dark current. But ZWO's charts show the dark current is lower for the 294 than the 1600. Could it be due to differences in the amp glow? The median value might not get pulled up much my a limited region of amp glow, though.

 

It could be as you're suggesting - the signal from four pixels is added instead of averaged, which would lead to higher values.

[andysea]

Wow fellas, I am really impressed with this camera thus far... this is the "first light" image of the Bubble nebula, it represents 6 hrs of O3 integrated data from last night in  19.3 sqm skies... only processing was calibration and cosmetic correction...  So far I think this data is much cleaner than with ASI1600MM, and no micro lensing...  I need to get the rest of the channel data and process, but so far I am pleased and think the money is well spent!

 

Questions:

 

Why are my background adu values significatly higher with this camera (binning?)

 

How can I account for the binning when trying to estimate adu values to dilute RN by 10x?

 

Excellent! I'm glad that the data looks good. That was also my impression when using the camera. Glad you could substantiate it.

[andysea]

Both of the IMX492 chips, color or mono, have micro lens. The color chip has a RGGB filter below the microlens and the mono is clear.

 

CMOS.PNGhttps://micro.magnet...agesensors.html

 

Here is the Sony data sheet: https://www.sony-sem...J_LQJ_Flyer.pdf

I think that the main difference between the graphic you linked and a BSI sensor is that all the circuitry is in the back of the chip. Right?

[jdupton]

Peregrinatum.

 

Wow fellas, I am really impressed with this camera thus far... this is the "first light" image of the Bubble nebula, it represents 6 hrs of O3 integrated data from last night in  19.3 sqm skies... only processing was calibration and cosmetic correction...  So far I think this data is much cleaner than with ASI1600MM, and no micro lensing...  I need to get the rest of the channel data and process, but so far I am pleased and think the money is well spent!

 

Questions:

 

Why are my background adu values significatly higher with this camera (binning?)

 

How can I account for the binning when trying to estimate adu values to dilute RN by 10x?

   The background levels in your raw frames are due to the camera Bias Offset level, the average QE of the sensor, Gain setting used, and the skyglow at your location. If you are comparing to another camera (Like the ASI1600MM) at the same location with the same exposure and Gain, it will come down to QE and Offset differences.

 

   Since each sensor used in different cameras uses different support electronics, the Offset value multipliers used in the electronics can be very different. So, for example, an Offset of 30 for one camera model can represent a very different Bias frame ADU level than an Offset of 30 in another camera using a different sensor. I think you are simply seeing the effects of the Offset Scaling differences between the hardware in the Sony IMX492 and the Panasonic MN34230 and the QE ~90% vs ~60%.

 

   Regarding read noise, you should not worry that the chip is internally binned or not. Just use the estimate from the ZWO published graphs for Gain vs Read Noise for the ASI294MM camera. It is the graphs you posted in Post #86. ZWO posted those specs based on the camera itself. You do not need to second guess what the inaccessible "unbinned mode" might be.

 

 

John

Edited by jdupton, 25 September 2020 - 01:32 PM.

[dghent]

 

Questions:

 

Why are my background adu values significatly higher with this camera (binning?)

Not the binning. What was your offset and was it appropriate for the gain your were operating it at? Offset is going to be the first thing I think of when the mean seems high.

[Lead_Weight]

So, I have a bit of a concern imaging with this new camera tonight. I noticed upon opening it that there's a strange issue with the CMOS sensor where it doesn't look uniform. So I compared it to my 1600 which is essentially like a smooth mirror in comparison.

 

 

1600 is on the top, and the 294mm is on the bottom.

 

I thought I had seen this before in some 294MC threads, but never looked too closely at it as I didn't have the camera.

 

So I took a few images against a flat light panel just to see how things looked through the filters, and the attached is the results.

 

 

Left image is Luminance, and right image is HA.

 

It appears that the CMOS imperfection pattern is possibly being reflected off the filter and is bouncing back into the sensor being captured. I did turn my filters around so that the highly reflective side is facing the camera, because that appeared to get rid of artifacts that were appearing on the 6200 camera in another thread. But now I'm thinking I might need to flip them back. Did anyone notice this issue with the sensor?

 

This same shape shows on both the HA, and OIII filter, but not the SII, nor LRGB filters. So maybe I only need to flip those two back.

[Astrojedi]

So, I have a bit of a concern imaging with this new camera tonight. I noticed upon opening it that there's a strange issue with the CMOS sensor where it doesn't look uniform. So I compared it to my 1600 which is essentially like a smooth mirror in comparison.

 

 

1600 is on the top, and the 294mm is on the bottom.

IMG_2303.jpeg

 

I thought I had seen this before in some 294MC threads, but never looked too closely at it as I didn't have the camera.

 

So I took a few images against a flat light panel just to see how things looked through the filters, and the attached is the results.

 

 

Left image is Luminance, and right image is HA.

Screen Shot 2020-09-25 at 5.01.03 PM.jpg

 

It appears that the CMOS imperfection pattern is possibly being reflected off the filter and is bouncing back into the sensor being captured. I did turn my filters around so that the highly reflective side is facing the camera, because that appeared to get rid of artifacts that were appearing on the 6200 camera in another thread. But now I'm thinking I might need to flip them back. Did anyone notice this issue with the sensor?

 

This same shape shows on both the HA, and OIII filter, but not the SII, nor LRGB filters. So maybe I only need to flip those two back.

Terrible... that does not look good. I will be happy to take the camera off your hands for a few hundred bucks. Get rid of it while you can....

[Lead_Weight]

I just flipped the HA and OIII, they look exactly the same. These are Astrodon 5nm filters. So maybe this is the new normal? It's pretty pronounced. I just hope it corrects out.

Edited by Lead_Weight, 25 September 2020 - 05:27 PM.

[andysea]

My h alpha and sii flats look similar. So far it calibrated out fine.

[Lead_Weight]

Update, I shot 20 lights in HA against a white background. They showed the strange sensor issue. I then shot flats, darks, and flat darks, and the strange area corrected out to a completely flat image. So I guess we're good despite how this looks.

[Peregrinatum]

Not the binning. What was your offset and was it appropriate for the gain your were operating it at? Offset is going to be the first thing I think of when the mean seems high.

Offset was 50, gain was 200 (e/adu)... how do I know if the gain and offset are appropriate?

[dghent]

Offset was 50, gain was 200 (e/adu)... how do I know if the gain and offset are appropriate?

The thing about offset is that, unlike gain where you tend to have some nice reference graphs from the vendor to know where you stand on things, offset isn't like that and a naked offset value by itself has zero context unless you're already very familiar with the camera. So I wrote up something to help people answer this question for themselves.

 

https://daleghent.co...g-camera-offset

[To The Universe and Beyond]

A newbie question here about the ASI294MM Pro and image scale with the Esprit 100.

 

I was just about to pull the trigger on the ASI1600 MM Pro to use with my recently acquired Esprit 100 when I discovered this thread, so now I'm wondering about waiting until the ASI294MM is available in the UK - possibly in mid-October.

 

I understand that accepted wisdom is to aim for an image scale between 1.0 and 2.0 to avoid undersampling and oversampling. With the Esprit 100 and ASI294MM the pixel size of 4.63 (compared with the ASI1600MM pixel size of 3.8) and focal length of 550mm gives an image scale of 1.734, which I guess should be fine.

 

I do plan to get a reducer/corrector at some point in the future though - the current one recommended by TS Optics is the TSRED379, which reduces the focal length equivalent by 0.79, giving a focal length of 434.5mm. However, with the ASI294MM this will give an image scale of 2.195, which I assume may lead to undersampling issues.

 

My question is - would the overall improvements of the ASI294MM over the ASI1600 Pro such as better QE etc be likely to compensate for the image scale with reducer on the Esprit 100 being over 2.0, to a point where it probably doesn't matter very much for overall image quality, or would I be better off with the ASI 1600MM Pro for my Esprit 100, which will give an image scale of only 1.801 with the reducer and 1.423 without?

[dghent]

You'll be fine at 2.1arcsec/px. People image with the existing 294MC on wider scopes and get good results. If for some reason it bothers you, you can always drizzle. The QHY version of this camera will let the user unlock the pixels and turn it into a 47mp/2.315um pixel image. Lots of data but it lets you recover some resolution into the 1.06arcsec/px realm, so you can have it both ways with 1 camera.