15 replies to this topic

[james7ca]

Now that I may have you interested, this is an UNCOOLED shot using the COOL version of ZWO's ASI178MM. This is a 6MP camera with tiny 2.4um pixels. I wasn't using cooling because I seemed to be having problems with dew formation on the sensor when I had the temperature regulation turned on, so these were taken with mother nature's own cooling system, a fairly brisk night (at least in southern California, mid-30s). The sensor temperature was reported as being 47F.

 

Also, this is just 64 seconds of exposure for each channel (4s x 16 subs) with calibration using 100 DF and bias frames. Capture scope was a Tele Vue NP127is with a 0.8X reducer (e.f.l. 528mm at f/4.2). Normally I wouldn't use the reducer or such a short focal length for an object like the Eskimo Nebula, but I wanted to make certain that I could get something usable/recognizable on the first night out and I had some technical problems with the object I started with, which was M78 (that's when I noticed what seemed like dew on the sensor).

 

I measured the median FWHM on the final RGB composite and it turned out to be 1.9 arc seconds (just about 2 pixels). The median eccentricity was 0.45 which is kind of mediocre and while the small stars look fine there does appear to be some issues with the shape of the brighter/larger stars. There was no guiding used with the 4s subs (lucky imaging techniques). In total, I have 500 subs for each channel which will take some time to process and make fit for presentation but I thought I'd throw this quick look out for review since I don't think I've seen many images taken with this camera (or actually, none at all).

 

In any case, here is what just over 3 minutes of integration time looks like on the Eskimo Nebula when using the ASI178MM. This is a crop (1600 x 1200) from the center of the image, but it's shown at the full pixel scale (0.94 arc seconds per pixel). Fairly quick and straightforward processing in PixInsight and Photoshop CC2015.

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Edited by james7ca, 10 January 2016 - 07:37 AM.

[rkayakr]

Nice to see a first result.

I think that you mislabeled the camera name in the last paragraph of text.

[james7ca]

Nice to see a first result.

I think that you mislabeled the camera name in the last paragraph of text.

Yes, thanks for that catch, I've corrected the name.

[geo444]

Congratulations : it's a very revealing first test of the Asi178mm !

I suspect the imx178llj to be a very good sensor, it shares many with the 1" BSi CMos that's in the Rx100(II-III-IV). Despite 48 subs stacked only, one can't spot any hint of FPN (banding) from your Photo, which indicates it's a Full Specification Exmor, particularly the Digital CDS that eliminate up to 99% of the Pattern Noise !

Please, could you post a pushed 100% crop of the Worst part from your set of Bias frames...

Thanks ! 

[james7ca]

Here is a PixInsight AberrationInspector matrix for a master bias create from the ASI178MM (100 subs, master created by PixInsight's BatchPreprocessing script). This was with no cooling, camera temperature reported as 7.9C (46F), 0.064ms exposure. The only transform applied to this was a PixInsight auto stretch followed by the AberrationInspector script to create a 1:1 scale, 3 x 3 matrix taken from the corners, sides, and center of the full frame.  It was also converted from 16 bit grayscale to a pretty highly compressed, 8-bit JPEG.

 

These are very preliminary results and pixel peeping to the extreme so I caution not to draw too many conclusions from this single sample.

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Edited by james7ca, 10 January 2016 - 05:58 PM.

[evan9162]

Too bad we're limited to JPGs.  The compression artifacts are the predominant pattern in the noise...

[james7ca]

Too bad we're limited to JPGs.  The compression artifacts are the predominant pattern in the noise...

In the reproduced image of the Eskimo, there is some deterioration in the dark background from the JPEG compression but I wouldn't call it extreme or very bad.

 

However, in the master bias there doesn't seem to be much difference between the compressed JPEG and the 16-bit, uncompressed TIFF that was used to create the JPEG file. However, I'm sure you could find differences since the "noise" in the master bias is so random that I had to use a fairly high compression to get under CN's 500KB limit. In any case, the medium-fine and large scale features are probably identical.

Edited by james7ca, 10 January 2016 - 06:12 PM.

[james7ca]

Here is a HIGHLY stretched difference frame between the uncompressed 16-bit TIFF image of the Eskimo Nebula and the compressed 8-bit JPEG. Of course, this is also compressed and a JPEG file but I think it represents fairly well the difference in the two images. Without the levels adjustment in Photoshop (i.e. the stretching) the difference frame looked almost completely black with just a hint of changes to the background and no real visual pattern except those created from the stars and the nebula itself. You can see very fine and small blocking artifacts but those are almost lost in the random noise of the background.

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Edited by james7ca, 10 January 2016 - 08:03 PM.

[mfarrell]

Wow, that looks amazing for only 3 minutes total exposure.  Even at such a short focal length the image scale is still nice.  1.9 arc sec FWHM at 528mm focal length is pretty much unheard of until we got these tiny pixels.  We may have a real winner here for fast imaging systems.  It will be interesting to see how it does with slower systems in the f/6 to f/8 range.

 

Great stuff James, please keep it coming!

[james7ca]

I've started a new thread where I will post some of the processed images that I've done with the ASI178MM. These will be "finished" results which may not fully represent what the "raw" camera is delivering (which could be better or worse than what I will show, given my processing and other factors). Here is the link to that thread:

 

  http://www.cloudynig...l/#entry6991686

[geo444]

Here is a PixInsight AberrationInspector matrix for a master bias create from the ASI178MM (100 subs, master created by PixInsight's BatchPreprocessing script). This was with no cooling, camera temperature reported as 7.9C (46F), 0.064ms exposure. The only transform applied to this was a PixInsight auto stretch followed by the AberrationInspector script to create a 1:1 scale, 3 x 3 matrix taken from the corners, sides, and center of the full frame.  It was also converted from 16 bit grayscale to a pretty highly compressed, 8-bit JPEG....

 

I am sorry that I have requested for that ' Bias Map ' because it's not the easiest way to appreciate the amount of FPN in the Asi178's RAW files...

 

...  the "noise" in the master bias is so random that I had to use a fairly high compression to get under CN's 500KB limit...

 

That's what I wanted to bring to everyone's appreciation...

 

Here is a HIGHLY stretched difference frame between the uncompressed 16-bit TIFF image of the Eskimo Nebula and the compressed 8-bit JPEG. Of course, this is also compressed and a JPEG file but I think it represents fairly well the difference in the two images. Without the levels adjustment in Photoshop (i.e. the stretching) the difference frame looked almost completely black with just a hint of changes to the background and no real visual pattern except those created from the stars and the nebula itself. You can see very fine and small blocking artifacts but those are almost lost in the random noise of the background.

 

Oh, that gives me an Idea !

Please, would you rebuild your First Picture of Eskimo Nebula in the Same Way with 3 x 16 x 4 sec. Subs and the Dark Frames but... Without the Bias Frames ? Thus we could compare and appreciate the difference between both pictures = with and without the Bias Frames ? You could also post this ' HIGHLY stretched difference frame ' between both pictures ?

Thanks.

Edited by geo444, 11 January 2016 - 04:29 AM.

[james7ca]

Here is an UNCALIBRATED and highly stretched image sample from my ASI178MM. This is a stack of 30 subs that were each exposed for 90 seconds (45m total integration time) in red light with a Tele Vue NP127is working at f/4.2 (e.f.l. 528mm). This is a full frame sample, but reduced by 50% to meet the CN posting guidelines.

 

The good new is that in this particular sample there is no apparent pattern or banding noise. Since this is an uncalibrated sample (no bias and no DF) you can definitely see some amp glow (top right) and some apparent heat sources (bottom left and right corners) but otherwise I think it looks pretty good. The camera gain was set to 300 and given the base exposure of 90 seconds this is probably near to the sky fog limit under my red/orange zone light pollution. Given that, the background sky fog may be helping to mask any banding or pattern noise. The camera's temperature set point was -20C which was about 25C below the ambient air temperature.

 

The median FWHM on this sample was 2.65 arc seconds and the median eccentricity was 0.3876 (both as measured by PixInsights FWHMEccentricity script). One again, this is essentially a completely unprocessed image, no bias frames, no dark fields, no noise reduction, just a simple auto stretch to convert the raw, linear image to something that shows some image detail.

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[geo444]

Here is an UNCALIBRATED and Highly Stretched image sample from my ASI178MM. This is a stack of 30 subs that were each exposed for 90 seconds (45m total integration time) in red light with a Tele Vue NP127is working at f/4.2 (e.f.l. 528mm). This is a full frame sample, but reduced by 50%...

 

The good new is that in this particular sample there is no apparent pattern or banding noise. Since this is an uncalibrated sample (no Bias and no DF)... The camera gain was set to 300 and given the base exposure of 90 seconds... The camera's temperature set point was -20C which was about 25C below the ambient air temperature.

 

This is essentially a completely unprocessed image, No Bias frames, No Dark fields, No Noise Reduction, just a simple auto stretch to convert the raw, linear image to something that shows some image detail.

.

Wow !

Thank you very much James ! 
Look Ma !... No Banding at all !... Not a hint of FPN !

 

The Full Specs Exmor CMos sensor for Astrophotography that I was hoping for since 2010 !

 ( Full Specs = Digital CDS inside )

.

 

... this is probably near to the sky fog limit under my red/orange zone light pollution. Given that, the background sky fog may be helping to mask any banding or pattern noise....

.

We share the Same Sky with a Huge Light Pollution, James...

 

You have the ability to get rid of that Sky Glow by mounting an UHC filter,

and thus, could Test Furthermore the Asi178mm's Resistance toward Banding ?

... I'm patiently waiting for it... 

 

 

Here is a Pentax K5 on a Skywatcher 254/1200 through an UHCs Filter

-Left = the 1000 sec. Exposure at ISO 80 at F4.7 - Raw file as is

-Right = this Raw pushed +6 Ev with an S Contrast Curve

Exif Data as in 2011/04 : FL is not 800 but 1200mm

http://www.cloudynig...k5lv-5-6/large/

camera Temperature ~23°C ambient ~11°C

 

and what does it shows : No Banding at all

... not the tiniest hint of FPN !

1st Exmor: 2010

 

http://www.cloudynig...k5lv-5-6/large/

 

 

/!\ can't find the way to Attach a Pic as you did ??

 

 

Edited by geo444, 13 January 2016 - 07:55 AM.

[PiotrM]

I got the camera too, although I don't have any photos yet, aside some indoor tests - http://www.cloudynig...m-cool-testing/

[Thirteen]

I may end up with 2 ZWO cooled cams. I want that thing.

[james7ca]

Since I seem to have been one of the early adapters of the ASI178MM-Cool I want to give a quick update on what I've found after a few weeks of limited use.

 

1.) The camera seems to work very well for lunar photography with a good dynamic range and sharp results.

 

2.) The set-point cooling seems to work well and the temperature as reported in Sequence Generator Pro is stable within +/- 0.5C even as the camera goes in and out of exposure sequences.

 

3.) The amp glow, although quite apparent in a stretched, uncalibrated image seems to be almost totally eliminated with a good set of DF and bias files.

 

4.) There is some pattern noise but it seems to be much lower than on my uncooled ZWO ASI174MM camera.

 

5.) The ASCOM interface/driver seems to work very well with Sequence Generator Pro.

 

That's the good news. However, as yet I have been unable to determine at what level the ASI178MM will function for DSO photography. I'm not ready to make a final determination and I can't give any specifics as yet, but if you've held any concerns about the suitability of this camera for DSO work then I can produce nothing right now that could allay those doubts. Thus, in my hands it remains an open question as to whether the ASI178MM will be near to the top or closer to the bottom of the CMOS choices for DSO photography.

 

I hope to have a better idea on where it stands in the next few weeks.