1767 replies to this topic

[wenjha]

here is a test from us show the relationship between power consumption and temperature drops when the cooler works

it can save your lots of power if you don't need to cool to the deepest

 

[syscore]

I see, so it is that last 5 degrees that takes another 50% power. So the % is accurate, but logarithmic. I wonder if other manufactures normalize the scale to make it seem more linear. But it does seem that you want to target 50% if you want to keep your temps constant all night.

[syscore]

Sam, is there a reason for limiting the exposure to 2000 sec?

[Jon Rista]

Tolga, thanks for sharing. Those darks have me pretty excited, very clean when cooled. I hope you don't mind, I took the liberty of stretching them all relative to the master bias:

Master Bias:

σK = 2.162e-005, N = 257917 (98.39%), J = 4

20C Dark:

σK = 1.024e-003, N = 195186 (74.46%), J = 4

-20C Dark:

σK = 1.919e-004, N = 257499 (98.23%), J = 4

Given the shift towards the right in the histogram with the 20C dark, it appears there is no dark current offset or suppression technology used in this sensor.

The cooling is curious...have you tried cooling with more than 50% power?

I ordered my ASI1600 after seeing this.

[bigeastro]

Okay,

Different then what I am used to with my current sensors.  That makes sense on the temperature.

 

Sam  Have to ask expected time of shipping for production models.  A few of us out here purchased the cameras directly.

 

Thanks.

[bigeastro]

Wow,

Look at those darks. I hope I can get to -20

[tolgagumus]

Tolga,

 

Are you sure on the 17mm from CMOS face to Filter Face?  That is pretty close and is similar to the QSI with the internal filter wheel.  If this is producting no noticable vignetting, then that is consistent with prior estimates from two sources.  You are the third.  I wonder what 20 or 22 mm would do?  That is what it turns out to be with the AXGYL filter wheel with stock adapters if I recall correctly.  The 1mm Precision Parts adapter places it at about 17mm.

I'll get you exact measurements when the darks are done

[bigeastro]

Take your time,

You are probably pretty excited about trying out the imaging.

Thanks for all the info.

[tolgagumus]

Tolga, thanks for sharing. Those darks have me pretty excited, very clean when cooled. I hope you don't mind, I took the liberty of stretching them all relative to the master bias:

Master Bias:
master_bias_stdev.jpg
σK = 2.162e-005, N = 257917 (98.39%), J = 4

20C Dark:
20c_dark_stdev.jpg
σK = 1.024e-003, N = 195186 (74.46%), J = 4

-20C Dark:
-20c_dark_stdev.jpg
σK = 1.919e-004, N = 257499 (98.23%), J = 4

Given the shift towards the right in the histogram with the 20C dark, it appears there is no dark current offset or suppression technology used in this sensor.

The cooling is curious...have you tried cooling with more than 50% power?

I ordered my ASI1600 after seeing this.

I don't mind at all. This is what this thread is about. I want the thread to stay technical. I am also working with Sam and Yang iron out any issues if they arise. 

[A. Viegas]

Looks great Tolga. Thanks for jumping in with the darks as I would have gotten to it until this Saturday or Sunday and the crowd here was getting frisky!

Al

[syscore]

Here is a comparison between the darks from an 8300 and a 1600 stretched the same. It also shows the higher resolution of the 1600 (the chips are almost the same physical size). The histogram in the first PNG is for the 1600, and in the second, the 8300. The temp, binning and exposure are the same.

 

https://dl.dropboxus...0_Histogram.png

https://dl.dropboxus...0_Histogram.png

 

Edited by syscore, 28 April 2016 - 09:58 PM.

[tolgagumus]

300 second Dark calibrated with Master dark

Attached Thumbnails

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[wenjha]

Sam, is there a reason for limiting the exposure to 2000 sec?

it's software limitation

because we use "int" as the exposure time and unit is us

so 2^31 equal to around 2000s

it should be enough in most cases

[wenjha]

Okay,

Different then what I am used to with my current sensors.  That makes sense on the temperature.

 

Sam  Have to ask expected time of shipping for production models.  A few of us out here purchased the cameras directly.

 

Thanks.

I think we can send at middle of May

[bigeastro]

Okay,
Different then what I am used to with my current sensors.  That makes sense on the temperature.
 
Sam  Have to ask expected time of shipping for production models.  A few of us out here purchased the cameras directly.
 
Thanks.

I think we can send at middle of May

Thank you very much. Take your time and work any issues out. Everyone will benefit. I think you have a winner! Congradulations and good luck. I am now a customer.

[syscore]

Tolga, why is your calibrated dark so low (1 x 10^-3)? Also, will you have a chance to do one 2000 sec dark?

[tolgagumus]

Tolga, why is your calibrated dark so low (1 x 10^-3)? Also, will you have a chance to do one 2000 sec dark?

Isn't that a good thing?

[Jeff2011]

Tolga,

 

The QE is listed as TBD. 

 

It would be nice to see 30 minute Oiii and Ha subs taken with this camera compared to the same with the 8300 on the same target. 

[tolgagumus]

Tolga,

 

The QE is listed as TBD. 

 

It would be nice to see 30 minute Oiii and Ha subs taken with this camera compared to the same with the 8300 on the same target. 

As soon as I get some clear skies LOL

[syscore]

 

Tolga, why is your calibrated dark so low (1 x 10^-3)? Also, will you have a chance to do one 2000 sec dark?

Isn't that a good thing?

 

 

Well, yeah, but that is like 0.00005 e-/sec dark current (considering a 300 sec dark). I don't recall seeing specs that low.

[tolgagumus]

Tolga, why is your calibrated dark so low (1 x 10^-3)? Also, will you have a chance to do one 2000 sec dark?

Isn't that a good thing?

Well, yeah, but that is like 0.00005 e-/sec dark current (considering a 300 sec dark). I don't recall seeing specs that low.

Just so we are clear. That's a dark frame calibrated with Master dark. It's just to show what to expect when you calibrate a light.

[tolgagumus]

Camera does -40 C from ambient and keeps it there with no problem, beyond that is not reliable. 

[bigeastro]

Camera does -40 C from ambient and keeps it there with no problem, beyond that is not reliable.

I start out at 25 in the summer. That should leave me at -10 to -15. What power for -40? You really think it will hold all night long at -40? or is that stretching it.

[tolgagumus]

Camera does -40 C from ambient and keeps it there with no problem, beyond that is not reliable.

I start out at 25 in the summer. That should leave me at -10 to -15. What power for -40? You really think it will hold all night long at -40? or is that stretching it.

If you think your ambient temperature is going to go up more than 5 degrees, I would set it at -35. But usually temp goes down during the night. So far with what I'm seeing I'm pretty confident it will hold - 40

[bigeastro]

That means I should be able to hold -15 most of the time. Sometimes with the western winds off of the Gulf of Mexico in the August and Sept when the water is around 31 to 33 C it does not get any cooler and actual start temperatures are around 28 c, so -10 will be my worst case scenario. Heck of a lot better than no cooling on my t3i or bad cooling from my ST8.

Thanks