ASI 184 Pro or non Pro

[CCD Imager]

I believe I am correct in thinking that the Pro version has a memory buffer which improves data transfer stability and reduces amp glow. I already have a 1600MM cool and have not had any issues with data transfer or amp glow. The amp glow is there, but corrects with proper calibration frames and perhaps the stability issue is with planetary imaging and dropping frames in a video sequence. Also the latest firmware improves amp glow by turning the amps off during exposure. So will the Pro version benefit me as a deep sky imager?

Adrian

[Adam J]

22 hours ago, CCD Imager said:

I believe I am correct in thinking that the Pro version has a memory buffer which improves data transfer stability and reduces amp glow. I already have a 1600MM cool and have not had any issues with data transfer or amp glow. The amp glow is there, but corrects with proper calibration frames and perhaps the stability issue is with planetary imaging and dropping frames in a video sequence. Also the latest firmware improves amp glow by turning the amps off during exposure. So will the Pro version benefit me as a deep sky imager?

Adrian

Got to assume you mean the ASI183mm pro as there is no 184 to my knowledge. 

In this case the difference is not just the memory, the ASI183mm pro is the only version with cooling, so if you want to do any DSO imaging with the camera then you will want the pro or you will have issues with calibration of the starburst amp glow. 

Adam 

[CCD Imager]

Yeah, I didn't realise the non pro doesn't have cooling, no brainer then

[newbie alert]

On 12/08/2018 at 12:51, CCD Imager said:

I believe I am correct in thinking that the Pro version has a memory buffer which improves data transfer stability and reduces amp glow. I already have a 1600MM cool and have not had any issues with data transfer or amp glow. The amp glow is there, but corrects with proper calibration frames and perhaps the stability issue is with planetary imaging and dropping frames in a video sequence. Also the latest firmware improves amp glow by turning the amps off during exposure. So will the Pro version benefit me as a deep sky imager?

Adrian

Thought amp glow was from the heating from the circuits during the exposure?

 

[Oddsocks]

1 hour ago, newbie alert said:

Thought amp glow was from the heating from the circuits during the exposure?

The amp glow seen at the edges of the frame in CMOS cameras is mostly generated by the on-chip analogue to digital converter and row and column amplifiers which are only active during array read after the exposure is complete.

When the camera is downloading a large frame over a slow connection such as USB 2 the A2D and row/column amps have to remain switched on for the entire duration of the transfer to the host computer, this leads to the pixels closest to the amps aquiring thermal photons, i.e. ‘amp glow’.

By the inclusion of a fast external memory buffer the A2D and row and column amps are only switched on long enough to read the sensor and write to the fast frame buffer, leading to reduced amp glow while the much longer read out of the memory buffer to the host computer can take place off-chip and being off-chip this creates no additional amp-glow.

During actual exposure the A2D and row/column amps are turned off, the amp glow is only generated once the exposure is finished and the sensor is being read, hence the inclusion of a fast in-camera DDR memory frame buffer does reduce amp-glow quite considerably for long exposure imaging, it has less impact for short exposure imaging and video mode where heat build up caused by repeated expose-read cycles in a short space of time exceeds the ability of the cooling system to remove it.

 

[CCD Imager]

Oddsocks, thats exactly how I understand it and if you transmit via USB 3.0, then the memory buffer becomes a bit redundant. Also the turning off of the amps during exposure is only a recent driver update fix, but all welcome

[Adam J]

1 hour ago, Oddsocks said:

The amp glow seen at the edges of the frame in CMOS cameras is mostly generated by the on-chip analogue to digital converter and row and column amplifiers which are only active during array read after the exposure is complete.

When the camera is downloading a large frame over a slow connection such as USB 2 the A2D and row/column amps have to remain switched on for the entire duration of the transfer to the host computer, this leads to the pixels closest to the amps aquiring thermal photons, i.e. ‘amp glow’.

By the inclusion of a fast external memory buffer the A2D and row and column amps are only switched on long enough to read the sensor and write to the fast frame buffer, leading to reduced amp glow while the much longer read out of the memory buffer to the host computer can take place off-chip and being off-chip this creates no additional amp-glow.

During actual exposure the A2D and row/column amps are turned off, the amp glow is only generated once the exposure is finished and the sensor is being read, hence the inclusion of a fast in-camera DDR memory frame buffer does reduce amp-glow quite considerably for long exposure imaging, it has less impact for short exposure imaging and video mode where heat build up caused by repeated expose-read cycles in a short space of time exceeds the ability of the cooling system to remove it.

 

That is not quite correct, the amp glow on the 183 grows in accordance with exposure length + read time. So you can derive that the source of the glow is active during the entire length of the exposure. Although this kind of pattern is called amp glow its not always the amplifier that is responsible, it just has to be a piece of circuitry on the CMOS that is emitting heat or more likely due to the star like form of the glow on the 183, IR light.  So if anything in this case the improvement in calibration related to the presence of memory is likely associated with read time being highly consistent making for a consistent glow at a given exposure length, but the bulk of the glow happens during exposure and is temperature / exposure time dependent. 

Now the corner glows that they removed with a firmware update, those probably actually are amplifier related.