ASI178MM 14 bit?

ASI's Range of Specialised CMOS camera's

Moderators: Sam, Sean.Wang

Post Reply
pdb
Posts: 13
Joined: Tue Feb 16, 2016 9:51 pm

ASI178MM 14 bit?

Post by pdb » Fri Sep 13, 2019 10:41 am

Hi,

always used this cam for planetary/solar but started to use it for a some deep-sky (don't have a cooled cam yet ...)
Although mentioned as a 14 bit cam, the max value i can see in the FITS files is 65528. This looks like the 14bit value is shifted by 3 bits instead of the 2 bits I expected. (and probably this will shift out a bit containing data ...)

Any reason/explanation for this.

Regards,

Paul

PS: I use the cam with 14bit ADC enabled (high speed disabled) and happens on all platforms; W10 Ascom, W10 Direct, Indi ....

Katherine.Tsai
Posts: 210
Joined: Fri Dec 07, 2018 10:24 am

Re: ASI178MM 14 bit?

Post by Katherine.Tsai » Mon Sep 16, 2019 9:58 am

The image will be saved as 16bit fit file.
14 bit image will be stretched to 16bit.
viewtopic.php?f=29&t=8436
Hope this can help you.

pdb
Posts: 13
Joined: Tue Feb 16, 2016 9:51 pm

Re: ASI178MM 14 bit?

Post by pdb » Mon Sep 16, 2019 10:09 am

NO. this is not the question. I know it is stretched to 16 bit by shifting. My point is that it shifts 3 bits instead of 2.
(but on bias frames the shift seems correct)

Paul

User avatar
chad
Posts: 603
Joined: Thu Feb 09, 2017 4:58 am

Re: ASI178MM 14 bit?

Post by chad » Tue Sep 17, 2019 8:29 am

Hi Paul,
As we know, for a 14 bit camera, it means we use 14 "0" or "1" to save a data. So the range should be 2^14=16384.
then the minimum is 14 "0"s(=0). and the maximum is 14 "1"s(=16383). it means we could use it to standard from 0 to 16383 . The maximum value is Not 16384.
And sometimes, for some camera, when there is a continuous transmission of 1, there will be other meanings. So it is not used as valid data. For 178 , it is an example. That is why the max value is 16382.
And as we know, for our 16bit, we add 2 "0" at the end of the data. It means that we multiply the raw data from sensor by 4. So 16382*4=65528.
Hope you can understand.
Thanks
Chad
ZWO Driver Engineer
Location:lon=120.6 lat=31.3
SuZhou China

pdb
Posts: 13
Joined: Tue Feb 16, 2016 9:51 pm

Re: ASI178MM 14 bit?

Post by pdb » Tue Sep 17, 2019 2:32 pm

Thanks Chad,

That explains the difference I see.

Regards,

Paul

Post Reply