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ASI2600MC-Pro Best Practices (settings)?

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#1 TelescopeGreg

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Posted 26 September 2020 - 10:55 PM

Hi folks,

 

Getting started with an ASI2600MC-P camera, as a significant upgrade from a DSLR.  I've got it working, but wonder if there are a better set of settings that I should be using.

 

My scope is a Stellarvue SVA130EDT, unreduced, so it's running f/7.  The mount is an AVX, so I generally used fairly short subs (20-30 seconds) with my Nikon D3200 DSLR, even with it under autoguider control, running the ISO up to 3200+ to compensate.  That put the histogram at about the 1/4 point, as reported on the back of the camera.  I'm in Bortle zone 6+ here. 

 

First real images were this past week.  The acquisition software platform is CCDciel + INDI on a 4gb Raspberry Pi-4B.  A 10 second test exposure at a gain of 100 (it's described optimal value) and an offset of 5 (chosen by me, to keep a Dark from having a lot of zero pixels) netted absolutely nothing.  Bumping the gain to 300, and a 60 second exposure seemed usable, if still a little dim.  The histogram (as displayed in CCDciel) wasn't off the left edge yet, but there was a little hint of a tail starting.  I grabbed the Goofi Challenge image there.  With that "in the can", I tried 4 minutes exposure.  Seemed a lot better with the histogram, and I went off to pick up M33.  The mount cooperated for some reason, and I got some good subs.  (See M33, below.)  I'm using a 2x2 on-camera Bin for all of this, in order to improve download time, and because it should improve SNR.  I'd bin in processing anyway, and doing it on-camera means I get more net imaging time.

 

Looking at the settings in INDI, there are a number of defaults under "Controls" that I don't know what optimal values should be.  These are my questions for this thread.

 

1.  The Offset interacts with the Gain setting.  Is there any magic about what to pick, as long as I'm not picking something so large as to saturate things?  Is 5 ok?  Too small?

 

2.  Color balance.  There are settings for Red and Blue, which are defaulted to 52 and 95, respectively.  My skills in color balance are close to nil; are there better choices here?  StarTools 1.6 doesn't have an "Identity" setting for astro cameras in the color module, so that's not going to save me.

 

3.  I know I'm eating into the dynamic range by picking a gain of 300.  The INDI default was 200, and ZWO says that 100 is the optimal value.  Given that I don't want to run 12 minute subs (even 4 minutes is historically unrealistic), is there any other way to get a bit more sensitivity out of the camera?  What is the "best practice" setting for Gain and Offset on this camera, when used with an f/7 telescope?  Or, am I ok with the histogram pushed up against the left margin, given that the histogram thing is a rule of thumb for DSLRs, and this isn't a DSLR?

 

4.  Format.  Choices are Raw 8 bit, RGB 24, Luma, and Raw 16 bit.  Raw 16 bit is the default, and what I used, but I'm wondering about RGB24.  What's that used for and is it better?  I'm using DSS for stacking, and StarTools for processing, if that matters.  I did end up with a color image.

 

5.  I've got the temperature set to -5C.  Seems to work...  Any significant reason to go lower?  I run from batteries, and the current draw increases the colder you get.  According to Robin Glover's video, in Bortle 6 it should hardly matter to even be cooled.

 

6.  The AntiDewHeater is set to 0.  What should be set here, if it's needed?  How would I know?  Is this a % of max type of setting?

 

7.  Calibration subs.  Some cameras work well with Bias, some don't and prefer Darks.  I grabbed a set of both, but which calibration strategy should I be using for this camera? 

 

8.  Anything else I should be considering?

 

Below is a "test image" of M33, cropped only a little around the edges for stacking artifacts.  Just 46 minutes total integration, with most of the subs taken at 4 minutes, 300 gain, 5 offset.  Stacked in DSS, quickly processed in StarTools.  I think it's a lot better than what I submitted from the DSLR back in October 2018.  There's also the submission to the Goofi Challenge of NGC-7129, as another reference.

 

Thoughts?

 

Thanks!

Attached Thumbnails

  • M33 2 nights 46 min 300 gain 2x2 ST old process-b.jpeg

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#2 sn2006gy

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Posted 26 September 2020 - 11:09 PM

1. I use gain 100 and offset of 50

2. Color Balance should be 50/50 but sometimes you can have fun with that weird factory default one. It makes HA blood red :)

3. I shoot unity gain with a narrowband filter at 300 seconds, you shouldn't need long subs with this camera 

4. I left format default

5. -5c is perfect, very low/no dark current. Can get cooler in cooler temps.

6. This time of year i set dew heater to ON

7. I only use Flats, Flatdarks and Lights.  I don't use Bias or Dark frames. Camera doesn't need dark.  I have a flip flat so the flats and flatdarks work well enough for me but i may just do flats, bias and lights sometime. 

8. Have fun! :)


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#3 Jim Waters

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Posted 27 September 2020 - 12:07 AM

How can you change the color balance?

 

I use - Gain 100, Offset 50 and shoot at 0C or -10C depending on the ambient temp.



#4 sn2006gy

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Posted 27 September 2020 - 12:30 AM

How can you change the color balance?

 

I use - Gain 100, Offset 50 and shoot at 0C or -10C depending on the ambient temp.

The color balance is set in NVRAM to 52/95 for some odd reason and if you run native drivers, it will leave that at that unless you override them.  The odd thing is, if you run the ascom drivers it sets it to 50/50 there.

 

You can run the asitool or sharpcap to set it to 50/50 and it will be saved for future sessions.

 

I know NINA started defaulting the native driver to 50/50 too to mimic the behavior of the ascom drivers in the 1.10.hf1 release



#5 Jim Waters

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Posted 27 September 2020 - 12:40 AM

Thanks sn2006gy



#6 Stelios

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Posted 27 September 2020 - 02:42 AM

I have a sneaking feeling that your image is not being stretched. At 240" exposure and gain of 300 you are very likely clipping highlights.

 

Have you imaged at the same settings with the same software and different camera? Unfortunately I am not a Mac person, so have no experience with your acquisition software.



#7 TelescopeGreg

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Posted 27 September 2020 - 04:00 PM

I have a sneaking feeling that your image is not being stretched. At 240" exposure and gain of 300 you are very likely clipping highlights.

 

Have you imaged at the same settings with the same software and different camera? Unfortunately I am not a Mac person, so have no experience with your acquisition software.

The software used is on Linux, not a Mac, if that matters.  Acquisition is on a Raspberry Pi with CCDciel in control. 

 

I like the idea of comparing with other cameras...  I have used that system to grab images through the ASI174mm Mini guide camera and scope (though of different targets), and that seems to work just fine.  INDI reports Gain 240 / Offset 0, which appear to be the defaults for that camera.  The 174's QE is 77%, similar to the 2600's 80%.  The Guide scope is an f/4.6, so much faster than the f/7 imaging scope.  Scribbling on the proverbial envelope, and sifting through the archives, the images I took through the guider system had exposures all over the place (5 - 30 seconds and more), but a number of them were at 10 seconds.  So adding 2.3 stops of exposure (7**2 / 4.6**2) or 5x suggests that I would be at about 1 minute with that camera on the main scope.  So, I'm off by about 2 stops of the same with the 4 minute exposures on the 2600.  I think.  That might be enough to agree with you that there is a problem, but then again, the 174 is a 12 bit camera, and it's monochrome.  So a little apples / oranges?  I don't have a good enough feel for these things yet.

 

Changing the Gain with the 2600 definitely has an effect on the image gathered, so I know I'm controlling something.  Perhaps "300" in INDI is not "300" at the camera, though I have no reason not to trust it.

 

Mousing around one of the subs, the very center pixel of the brightest stars are indeed saturated with a value of 65535, but most of the background sky is in the 5k to 10k range, with the galactic core in the 15k+ range.  So, I think that's probably a reasonable exposure compromise.  You can't not saturate the brighter stars and still capture the fainter parts of the target.  In this screen shot, I'm pointing roughly at the bright star to the right of the galaxy, not quite centered on it.  Value is 24k (see bottom of window) at that spot.  The overall histogram in the lower right seems about right, as well, assuming it's displaying roughly what a DSLR would display.

 

CCDciel snapshot2.jpeg

 

My only other astro camera is a useless Skyris236C, which cannot go past 10s exposure. 

 

So, I'm curious where the stretching you refer to should be taking place.  The processing is in StarTools, and that's working pretty much as expected.  But, you have my curiosity...  Given this paper analysis, have I missed anything?



#8 TelescopeGreg

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Posted 27 September 2020 - 04:16 PM

The color balance is set in NVRAM to 52/95 for some odd reason and if you run native drivers, it will leave that at that unless you override them.  The odd thing is, if you run the ascom drivers it sets it to 50/50 there.

 

You can run the asitool or sharpcap to set it to 50/50 and it will be saved for future sessions.

 

I know NINA started defaulting the native driver to 50/50 too to mimic the behavior of the ascom drivers in the 1.10.hf1 release

Cool.  The values did seem a bit arbitrary, and R/G/B 50/100/50 seems more intuitive given the ratio of the number of pixels.  Or should it be 200/100/200?  Do they multiply or divide?

 

I'll change the values to 50/50 for R and B, but it will be a few weeks before I can take it out for another imaging run.



#9 TelescopeGreg

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Posted 28 September 2020 - 07:13 PM

Cool.  The values did seem a bit arbitrary, and R/G/B 50/100/50 seems more intuitive given the ratio of the number of pixels.  Or should it be 200/100/200?  Do they multiply or divide?

 

I'll change the values to 50/50 for R and B, but it will be a few weeks before I can take it out for another imaging run.

It occurred to me that I can do a quick test during the day.  I threw on the white T-shirt hoop (what I use to take flats), and took some low-ish exposure (1 second) flat images with the wb-r and wb-b set to the default 52/95, 50/50, and 99/99 (max allowed) while aimed at the garage ceiling (painted antique white, if I recall from decades ago).  Looked at the color cast in the 3 images with an app on my cell phone.

52/95 was center-green; 50/50 was yellow-green, and 99/99 was a startlingly deep orange-red.  Comparing to the cell phone aimed directly at the same garage ceiling, the 50/50 seems to be the closest.  Admittedly, an un-calibrated monitor, but that seems to confirm the 50/50 setting is correct.  Closed!

 

 

How can you change the color balance?

 

I use - Gain 100, Offset 50 and shoot at 0C or -10C depending on the ambient temp.

 

1. I use gain 100 and offset of 50

2. Color Balance should be 50/50 but sometimes you can have fun with that weird factory default one. It makes HA blood red smile.gif

3. I shoot unity gain with a narrowband filter at 300 seconds, you shouldn't need long subs with this camera 

4. I left format default

5. -5c is perfect, very low/no dark current. Can get cooler in cooler temps.

6. This time of year i set dew heater to ON

7. I only use Flats, Flatdarks and Lights.  I don't use Bias or Dark frames. Camera doesn't need dark.  I have a flip flat so the flats and flatdarks work well enough for me but i may just do flats, bias and lights sometime. 

8. Have fun! smile.gif

Ok, so 2 votes for gain 100, offset 50...

 

To Byron, we have similar scopes.  When you use Gain 100, Offset 50, what exposure do you tend to use when not using any filters?  I presume they're not in the 4 minutes range.

 

I tried both 300/5 and 100/50 with 1-second exposures.  300/5 had a pixel range of 1204 to 7569, while 100/50 had a range of 606 to 1249, both as reported in the FITS header.  Seems like the higher Offset isn't magically fixing things for exposure, and that I either need the higher gain, or something else is off... 



#10 Jim Waters

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Posted 28 September 2020 - 07:36 PM

Ok, so 2 votes for gain 100, offset 50...

Offset - Its not the number of votes...  Its what ZWO says.

 

Depending on the object, your imaging goals and other stuff, Gain 100 or 0.



#11 sn2006gy

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Posted 28 September 2020 - 07:36 PM

 

To Byron, we have similar scopes.  When you use Gain 100, Offset 50, what exposure do you tend to use when not using any filters?  I presume they're not in the 4 minutes range.

 

I tried both 300/5 and 100/50 with 1-second exposures.  300/5 had a pixel range of 1204 to 7569, while 100/50 had a range of 606 to 1249, both as reported in the FITS header.  Seems like the higher Offset isn't magically fixing things for exposure, and that I either need the higher gain, or something else is off... 

For no filter, I'm usually 60 to 120 seconds during new moon - but that was based on my old scope. I haven't had a clear new moon to try my esprit yet. I'll report back when i do :)   180 seconds seem to push too far and tbh i don't mind long integrations since computer time is more abundant than clear nights so i don't mind shorter subs.



#12 TelescopeGreg

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Posted 28 September 2020 - 10:10 PM

Offset - Its not the number of votes...  Its what ZWO says.

Even better!  Where did you find that?  Neither the user guide nor website seem to discuss the offset value.

 

 

For no filter, I'm usually 60 to 120 seconds during new moon - but that was based on my old scope. I haven't had a clear new moon to try my esprit yet. I'll report back when i do smile.gif   180 seconds seem to push too far and tbh i don't mind long integrations since computer time is more abundant than clear nights so i don't mind shorter subs.

Old scope was a...?  Scanning your website (nice work!), it looks like it was an ED-80, so, f/7.5?  Similar (I'm at f/7), so 4 minutes in my Bortle 6+ zone, aiming over the town's light dome, with the Moon just having set does sound a bit long.

 

Ok, so another difference.  I was using the on-camera binning 2x2; you're at 1x1.  Re-taking some test shots, appears that the 2x2 bin is making the pixel values a good bit lower.  I expected the reverse (better SNR, right?).  At 1x1, range is 1232-6017; at 2x2 it's 1390-4927.  Not a factor of 2, but significant.  Perhaps enough.  I may have to revisit the benefit of the shorter download time, if I need to take more total integration with 2x2 to achieve the same values as 1x1.

 

Long integrations weren't a problem last week, and with a long download time (compared to zero with the DSLR), a longer exposure makes the download insignificant.  But with an AVX, 4 minutes has been historically risky.  I need more than the two nights to know whether the swap in cameras has anything to do with it.  My guess is that it was mostly luck.

 

EDIT:  I also just found a setting in CCDciel for "Start new exposures as soon as possible".  That appears to start the next exposure while saving and processing the prior exposure for display.  Saves about 20 seconds per sub, which will certainly help.


Edited by TelescopeGreg, 28 September 2020 - 10:23 PM.


#13 Jim Waters

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Posted 28 September 2020 - 10:25 PM

Even better!  Where did you find that?  Neither the user guide nor website seem to discuss the offset value.

E-mail from ZWO support earlier this year.  Recommended setting.  I will have to look for it...



#14 TelescopeGreg

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Posted 19 October 2020 - 06:50 PM

Hi folks,

 

Reviving this thread with some new data.  And a re-ask of the color balance settings question.

 

New data.  I updated my acquisition software (CCDciel) and noticed that Patrick is now reporting RGB values for pixels as you move your mouse around the screen.  Nice.  But now a puzzle.  The "white" of the flats aren't even close to having similar values for all three color planes.  Shouldn't they be? 

 

Worse, the relative values for each is highly dependent on the exposure.  More exposure makes the differences more pronounced.  For example, a quick test.  White T-shirt method for flats.  Gain 100, offset 50.  INDI's setting for the camera has WB_R and WB_B set to 50, as discussed earlier.  Note:  For testing simplicity, these are random pixels from near the center of the frame, not a whole-frame average, but are pretty representative of what's going on.

 

Exposure   Red / Green / Blue

-----------------------------

Dark       502 /  501  /  503 (any exposure in this range)           

0.001      594 /  622  /  569

0.01      1357 / 1639  / 1108

0.1       9536 /12609  / 6336

0.5      45338 /60069  /29927

 

 

As you can see, the three color channels are pretty even at low exposures, but as exposure ramps up, the difference between the three becomes dramatic.  Notably, there's a 2:1 difference between the green and blue, with the red falling about in the middle between them.  So, I can discount the low exposure cases as irrelevant from a practical matter, but the 0.75 : 1.0 : 0.5 ratio of the higher values tells me that the camera's white balance settings (50 / 50) may not be correct.  For comparison, when I was using my DSLR for imaging, the flats taken in the same manner had some difference between the colors, but nothing like this.  If I recall, Green was the strongest, with Blue just below, and Red down a significant amount from Blue.  (Typically red-blind Nikon, right?)

 

Is this a test issue, or a settings issue?  Given the DSLR experience, it sure sounds like a camera / sensor thing.

 

So the question:  If due to settings, what (really) should the WB_R and WB_B values be?  I can correct for it in processing, but it would be nice to start out at least close to correct.  As it is now, my images have a very warm cast to them.



#15 sn2006gy

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Posted 19 October 2020 - 07:01 PM

The white balance with ascom drivers is set to 50:50 - the white balance with native drivers was set to whatever the default in nvram was last set to.

When I didn’t have my white balance adjusted correctly my images were blood red - they looked cool but otherwise I could tell something was off.

#16 nyda83

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Posted Yesterday, 05:32 AM

on my edgehd 8" with reductor and filter:

offset 50 (as zwo reported)

gain 100

exposure 200"

R/B 50/50

raw16

never bin on camera, download time it's around 5/6 second on windows minipc connected to the scope.

 

Look at my image on astrobin, I put every detail in it.



#17 TelescopeGreg

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Posted Yesterday, 01:28 PM

The white balance with ascom drivers is set to 50:50 - the white balance with native drivers was set to whatever the default in nvram was last set to.

When I didn’t have my white balance adjusted correctly my images were blood red - they looked cool but otherwise I could tell something was off.

on my edgehd 8" with reductor and filter:

offset 50 (as zwo reported)

gain 100

exposure 200"

R/B 50/50

raw16

never bin on camera, download time it's around 5/6 second on windows minipc connected to the scope.

 

Look at my image on astrobin, I put every detail in it.

Right, I understand 50 / 50 is what they recommend, and what people use.  I'm trying to verify that it's being applied properly in my system.  It's the engineer in me, cross-checking stuff, and when I see something that doesn't seem to match, I ask questions. 

 

I guess what I don't understand is what the reported R/G/B pixel values should be when doing a white "flat" image.  Shouldn't each be about the same, i.e. a ratio of 1:1:1?

 

I did a more scientific test, using my precariously balanced laptop screen atop the telescope (note to self: get a proper flat panel!), and found the values in the range of 1:2:1.  One random pixel was 22054 / 40137 / 24033, and that was pretty consistent around the screen.

 

Is that a "correct" R:G:B balance for "white" in a Flat? 

 

Greg

 

P.s. to Nyda83, a full-frame (1x1 bin) takes about 12 seconds to download to my Raspberry Pi 4B on USB 3.0, compared to under 3 seconds at 2x2.  So given that I'm going to do a 2x2 bin anyway in processing, why give up the additional imaging time during acquisition?
 



#18 nyda83

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Posted Yesterday, 02:45 PM



P.s. to Nyda83, a full-frame (1x1 bin) takes about 12 seconds to download to my Raspberry Pi 4B on USB 3.0, compared to under 3 seconds at 2x2. So given that I'm going to do a 2x2 bin anyway in processing, why give up the additional imaging time during acquisition?


I'm an engineer too :-) I have done several test on the camera (search for my post about the linearity of the camera)
The use of the r/g 50/50 really doesn't matters because duringg the process you arr going do color calibrate the image and also if the flat field are not perfect white doesn't matter they are taken just yo create a caratteristic image of the camera+scope so don't lose time to active perfect white.
50/50 it's just a setting to be neutral as possible and calibrate afterwards. (It's the same thing as when you shoot with the reflex in raw mode and you can change the white balance in the post editing without bothering what you have use during shoot)
About the use of the bin it's deprecated everywhere in the cmos camera bacuse you have no control in it, you don't know if it's doing an average a median o whatever you wold like to do, I do it in pixinsight during the debayer process if I want to do that, if you go on the zwo site you can find a great guide about it
https://astronomy-im...ndamentals.html

Inviato dal mio SM-N975F utilizzando Tapatalk

#19 TelescopeGreg

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Posted Yesterday, 04:45 PM

I'm an engineer too :-) I have done several test on the camera (search for my post about the linearity of the camera)
The use of the r/g 50/50 really doesn't matters because duringg the process you arr going do color calibrate the image and also if the flat field are not perfect white doesn't matter they are taken just yo create a caratteristic image of the camera+scope so don't lose time to active perfect white.
50/50 it's just a setting to be neutral as possible and calibrate afterwards. (It's the same thing as when you shoot with the reflex in raw mode and you can change the white balance in the post editing without bothering what you have use during shoot)

I'm not after "perfect" white, just trying to determine what "white" should be by the numbers.  Being off by a factor of two (1:2:1) seems to be significant enough that it should be addressed during capture, not during post.  What is "white" in terms of R:G:B?

 

I am not a PixInsight user, but use StarTools.  When I was imaging with a DSLR, ST has a built-in color balancing for a long list of DSLRs, including mine, and it was very nice to just select it from the list and be done with it as a baseline.  Now, with the ASI camera, that initial balance needs to be set.  If "white" is 1:1:1, and I'm getting 1:2:1 with 50 / 50, shouldn't I be setting R and B to 100 and 100?
 

 

About the use of the bin it's deprecated everywhere in the cmos camera bacuse you have no control in it, you don't know if it's doing an average a median o whatever you wold like to do, I do it in pixinsight during the debayer process if I want to do that, if you go on the zwo site you can find a great guide about it
https://astronomy-im...ndamentals.html

Thanks for the link, worthy of some study.  And, yeah, knowing the algorithm for merging the pixels is important, yet they never talk about that.  Odd.  Of course, I don't have control over binning in ST either, though I probably trust Ivo more than ASI on this account.

 

Since I know I'm a bit oversampled (0.85" pixel scale), I'm guessing I'll stick with the on-camera bin for now, just because it's faster.  I still have a lot to optimize with the new camera, and this might be one to look at in more detail in the future.



#20 nyda83

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Posted Yesterday, 06:04 PM

I don't know startools, pixinsight has two tools to actually calibrate the image based on color reference or balance of the image (I use the first). You can not really trust a color calibration in the camera because there are gradients, light pollution and filter white shift (if you use one) so a color calibration of the image is a need step during the elaboration, so none can tell you what white is in terms of rgb, it depends but at the end it doesn't matters, the only thing that matters is that you stick with the same setting in all you session (light, flat, flat darks, and darks if used)

 

For the binning question I want to add that the time spent is not in the download time but in the dithering time and settle of the mount, that takes me around 20sec but it's absolutely needed with a cmos camera so go with the unbinned file because if you bin it you can't go back to unbinned, I like to have the choice during the elaboration instead of regretting I didn't choose the unbinned mode




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