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INDI Library v1.9.0 Released (23 Apr 2021)

Major INDI Library release v1.9.0 bring significant internal changes championed by @pawel-soja to modernize core INDI Library drivers and clients. New drivers for DeepSkyDad Flat Panel & Pegasus devices plus further improvements to PCM8 drivers.

ASI Camera bit size persistence issue

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Hi,

I am using ASI cameras that support a 12-bit ADC. When I use the default Ekos/INDI settings I notice that the INDI Control Panel shows that the 8-bit Raw Format is selected. This then results in my captured images being saved as only 8-bit FITS files i.e. stats show a maximum value of 255. Reading the docs, I picked up that 8 and 16 bit FITS are supported and to recover the extra 4 bits I will need to use the 16-bit format. When I then view the FITS stats, am I correct in saying that the 12-bit values are scaled up to fit a 16 bit values i.e. 0-4096 -> 0-65535? Also, when I exit and re-run the software the Format always defaults back to 8-bits. Is there a way to force the setting to stay at 16-bit?

Many thanks.
1 year 7 months ago #45704

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Going up to 16 bits will store 12 bits faithfully, is not scaled in any way to fill 16 bits. The extra bits are just zeros.

Save the ASI INDI driver configuration to have it remember the 16bit setting.
INDI/KStars on Raspberry Pi 4, 4gb
Raspbian Buster with AstroPi3 script configuration
Skywatcher HEQ5 Pro Mount
Canon 600D Camera
Orion SSAG/ASI120mm @280mm Guide Scope
PHD2
Waveshare Stepper Motor Board - DIY Focuser
Adafruit GPS Module
Generic Bluetooth Joystick.
Startech 7 port powered USB Hub.
The following user(s) said Thank You: Jasem Mutlaq, Alfred
Last edit: 1 year 7 months ago by Andrew.
1 year 7 months ago #45717

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This was recently discussed here:

www.indilib.org/forum/wish-list/5997-dri...ebth-as-default.html

As you can see Jasem has made sure that in future versions of INDI the default bit depth is set to 16 bits. Please read the rest of the comments in the thread as well.


HTH, Wouter
Wouter van Reeven

ASI6200MM and 7 slot 2" filter wheel with a SkyWatcher Esprit 80 ED on a SkyWatcher HEQ5-Pro
ASI1600MM-Pro Cooled and 5 slot 1.25" filter wheel with an 8" TS Ritchey-Chrétien on a SkyWatcher EQ6-R
1 year 7 months ago #45726

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Uh, no. At least the ASI cameras save their 16bit data left-aligned, i.e., the counts will be 0->65535, but increasing in 4bit = 16 count steps.
openSUSE Tumbleweed KStars git INDI git
GPDX+EQMOD, CEM60EC, ASI2600/1600/290mini+EFW+EAF
1 year 7 months ago #45816

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Curious why it's better to have the data left shifted, I can't think of any good reason.

Chris
1 year 7 months ago #45817

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I don't believe my statement was incorrect. For reference I found this explanation.
engineering.stackexchange.com/questions/...ustified-adc-results
If I understand correctly, Left-justified would be read as 0x123456789ABC0000 (would be binary in reality). Example being representative of 12 bits of information in a 16 bit register. The extra bits being zeros, as I said.
INDI/KStars on Raspberry Pi 4, 4gb
Raspbian Buster with AstroPi3 script configuration
Skywatcher HEQ5 Pro Mount
Canon 600D Camera
Orion SSAG/ASI120mm @280mm Guide Scope
PHD2
Waveshare Stepper Motor Board - DIY Focuser
Adafruit GPS Module
Generic Bluetooth Joystick.
Startech 7 port powered USB Hub.
1 year 7 months ago #45844

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Might be a semantic disagreement ;)
Yes, the result from the ADC will be padded with zeros. Padded on the right side. So the max value from the ADC (4095 = '111111111111') will be placed in 16bit as '1111111111110000'. Expressed in 16-bit, this is a four-fold bit shift left of the value 4095, which corresponds to a multiplication with 16. I'd well call that 'scaling'.
Upshot is, the data you get from ASIs is 0->65520, not 0->4095.
openSUSE Tumbleweed KStars git INDI git
GPDX+EQMOD, CEM60EC, ASI2600/1600/290mini+EFW+EAF
1 year 7 months ago #45860

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The data is shifted only, it's not being scaled.
1 year 7 months ago #45864

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Somewhat getting ridiculous.....
At least tell me then how 'scaling' would look in your opinion (and why multiplication is not scaling.....)
openSUSE Tumbleweed KStars git INDI git
GPDX+EQMOD, CEM60EC, ASI2600/1600/290mini+EFW+EAF
1 year 7 months ago #45870

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Point is the data is faithfully stored within. There is no loss or additional information, just some padding.
INDI/KStars on Raspberry Pi 4, 4gb
Raspbian Buster with AstroPi3 script configuration
Skywatcher HEQ5 Pro Mount
Canon 600D Camera
Orion SSAG/ASI120mm @280mm Guide Scope
PHD2
Waveshare Stepper Motor Board - DIY Focuser
Adafruit GPS Module
Generic Bluetooth Joystick.
Startech 7 port powered USB Hub.
1 year 7 months ago #45882

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