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16200 & RBI?


DaveS

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This is a very early finding-out exercise as yet, but...

I may be in the market for one of the KAF 16200 based cameras, in order of cost, Atik, Moravian G3, and SX Trius46 (FLI is out of my league!). Leaving aside for the moment diferences in BF and filter-wheels, the main thing  I see is with the SX, which says it has an inbuilt IR diode illuminator for RBI elimination.

I know there are folks on here who image with 16200 sensor cameras, so I'm asking if anyone been affected by RBI, and do you think RBI elimination is worth having?

There may be other advantages which justify the £800 or so difference in cost between Atik and SX, but I'm not sure how significcant they are.

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Hi Dave, I have had the Moravian G3-16200 (original version) for a few years now and have never had any noticeable problems with RBI using it at -20C or -25C. My G3 does have the RBI NIR pre-flash feature but I have never had the need to use it (even shooting flats); I would assume that the updated version also has it but I guess there is a chance they could have removed it.

What I have noticed is that for consistent calibration the camera needs two CCD clear cycles between exposures  (as is set by default in the Moravian SIPS capture software) or the background levels can start to drift and flats don't work properly.

Paul

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On ‎05‎/‎01‎/‎2019 at 11:24, Ikonnikov said:

Hi Dave, I have had the Moravian G3-16200 (original version) for a few years now and have never had any noticeable problems with RBI using it at -20C or -25C. My G3 does have the RBI NIR pre-flash feature but I have never had the need to use it (even shooting flats); I would assume that the updated version also has it but I guess there is a chance they could have removed it.

What I have noticed is that for consistent calibration the camera needs two CCD clear cycles between exposures  (as is set by default in the Moravian SIPS capture software) or the background levels can start to drift and flats don't work properly.

Paul

As I'm looking at 16200 shortly as well, could you clarify what you mean by the last sentence?  

Are you referencing when you take the calibration frames or when you are taking the lights (or both) so is it:-

Light/calibration frame
Bias Frame (effectively)
Bias Frame (effectively)
Light/calibration frame

or do you mean something else with "CCD clear cycles"

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In short I have had no issues with calibration when bias, flats (and darks) were taken using SIPS, regardless of which capture software i use for lights.

I only started having problems when I captured some new calibration frames in SGPro and noted that there was some inconsistencies in levels but can't remember the details. The end result was over correction with flats and inverse dust bunnies when trying to calibrate my light frames.

I put this diwn to the fact that SIPS includes 2 ccd clear operations between frames by default (i assume this is a function to remove any residual charge after the image dowload without having to do a proper readout but am not certain) but SGPro doesn't. It could be something else entirely but as i say everything is fine if I stick to SIPS for acquiring my calibration frames. 

Hope this helps 

Paul 

 

 

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22 hours ago, Ikonnikov said:

In short I have had no issues with calibration when bias, flats (and darks) were taken using SIPS, regardless of which capture software i use for lights.

I only started having problems when I captured some new calibration frames in SGPro and noted that there was some inconsistencies in levels but can't remember the details. The end result was over correction with flats and inverse dust bunnies when trying to calibrate my light frames.

I put this diwn to the fact that SIPS includes 2 ccd clear operations between frames by default (i assume this is a function to remove any residual charge after the image dowload without having to do a proper readout but am not certain) but SGPro doesn't. It could be something else entirely but as i say everything is fine if I stick to SIPS for acquiring my calibration frames. 

Hope this helps 

Paul 

I've found some information here as to what it is doing. 

https://www.gxccd.com/art?id=418&lang=409

Basically it NIR preflashes your CCD then reads out (at least twice preferably from the text) and then your repeat that the number of times you want to do this.

Effectively what you are doing equally flashing all the pixels to remove any old residual image (at the cost of raising the noise in the images). 

As stated it is temperature dependent so the warmer you are running the faster it dissipates.  

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Thanks for the link, it also answers a question I had about Moravian software, whether I could control RBI preflash in Maxim DL.

So it's looking increasingly like the Moravian. Now just waiting for @FLO to update us on the Moravian coming to FLO.

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1 hour ago, Whirlwind said:

I've found some information here as to what it is doing. 

https://www.gxccd.com/art?id=418&lang=409

Basically it NIR preflashes your CCD then reads out (at least twice preferably from the text) and then your repeat that the number of times you want to do this.

Effectively what you are doing equally flashing all the pixels to remove any old residual image (at the cost of raising the noise in the images). 

As stated it is temperature dependent so the warmer you are running the faster it dissipates.  

You can utilise the NIR preflash feature (followed by some CCD clear cycles) as indicated in the image on the Moravian instruments website for the G4-9000 camera, but the default for the G3-16200 is to have 0 sec for NIR preflash (i.e. no preflash) but 2 for Num clear (i.e. 2x clear cycles) so I assume the clear function is important regardless of whether or not you do the preflashing. The KAF9000 chip is very prone to RBI so the preflash is almost a must for this camera but the KAF16200 (and closely related 8300) show virtually no RBI signal down to at least -25C in my and others' (e.g. see Cloudy Nights forum posts) experiences.

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2 hours ago, DaveS said:

Thanks for the link, it also answers a question I had about Moravian software, whether I could control RBI preflash in Maxim DL.

So it's looking increasingly like the Moravian. Now just waiting for @FLO to update us on the Moravian coming to FLO.

Yeah, not many seem to have updated their sites fully to the new MKIIs.  

QSI are also bringing a version out (no release date).

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