Atik383-L+ strange bias

[GH-ATIK]

n=20 1x1 bin 13,0 V DC

[GH-ATIK]

and the last : n=20  1x1 bin  12,5V DC  from a car-battery

[GH-ATIK]

it seems, that the voltage and the stabilyzing has an influence .

greetings Gerhard

[Max]

Hi Gerhard,

there should be no problem with the bias frame – when there is the same behavior within the dark frames.

Please try this (easy to do in CCDStack):

1.) Open the DarkMaster
2.) Open the BiasMaster
3.) Take care that DarkMaster is selectet in CCDStak
3.) Process -> File Math -> Substract -> BiasMaster…
4.) Now the DarkMaster shout be clear – that means there is no Bias/Master banding problem.

Maybe:
The problem could be caused by the light frames – regarding the cooling unit of the early 383er.
The next days I will check other pictures.

Thanks a lot
Max

[Max]

Hi Gehrhard,

An idea:
Tomorrow I will check the behavior of the fan.
1a) Fan speed with less colling.
2a) Fan speed with more colling.
3a) Fan speed with max colling.

1b) Fan speed with 12V.
2b) Fan speed with 12.8V.
3b) Fan speed with 13.8V.

When the fan speed is not constant than there is a different cooling for the electronic parts.

Thanks a lot
Max

[Max]

Hi Gerhard,

I've done the tests.

Please have a look to the picture.
It was not so easy to find an analog volt- and  ammeter to see the rapid changes.
I have no oscilloscope at home…
The cable from the power supply to the ccd is only 1,5m (59inch) – to take care of the voltage drop.
The longer cable in the picture is only for the voltage measurement- it does not matter.
SW: TheSkyX with camera add on.

Tests 1a, 2a, 3a (power supply with 13V):
When the cooling is low (20% -> 0.7A) – than there is also less voltage drop (because of the current): 0.2V
When the cooling is medium (50% -> 1.2A) – than there is also medium voltage drop: 0.35V
When the cooling is high (75% -> 1.6A) – than there is more voltage drop: 0.5V
The speed of the fan is changes depending on the voltage drop.
When fan “coughs” than there was a fast change of the current – the regulation. (and there a lot of fast changes).
 
Tests 1b, 2b and 3b:
When the voltage is low - than the speed of the fan is also low.
When the voltage is higher - than the speed of the fan is also higher.
 
Conclusion:
There is no voltage regulation for the fan.
During the photo session the temperature of the night is changing.
Because of the change of the temperature the amount of current for the cooling unit is also changing.
This causes – because of the voltage drop to the camera plug – that the speed of the fan is also changing.
Maybe this effect could be the reason for the different banding behavior over the night.

I could make the measurements in the company with professional equipment – but I think it’s not necessary.

Thanks a lot,
Max

[GH-ATIK]

Hi Max,


Well, a good idea, but only a theroretical consideration invalidated this unproven thesis :
the "aperture time" of bias were as short as possible, and temperaturfluctuation ( better voltagefluctuation ) in this short time,
is excluded. the whole bias-session as well.
but : the effect is , indeed , voltage-dependent, howsoever.

I will test grownding of the powersupply and the cam, today.

thanks a lot

Gerhard

[GH-ATIK]

So, there is a solution :

I changed the powersupply , which is build for amateur radio with noise-reduction.
SPS 250-II
I measured the ground on minus, there was a connection.

on the other powersupply, there was no connection from ground to minus !

Ok, its not clear , if the voltage of 13,8V, the missing ground or noise-reduction was respunsible for the wrong bias,
but this result is now ok :


Thanks a lot

Gerhard

[Max]

Hi Gerhard,

respect and congratulations!
I will also have a look to another power supply.

Thanks a lot
Max

[Max]

Hi Gerhard,

I've looked at the specification of the Maas-SPS-200-II power supply: 13.8V.

Please have a look to the picture – also cleaner bias with my regulated power supply at 13.8V and grounding.
I have taken the bias at home – therefore only with -15°C.
That means: For clean bias 13.8V (in the range) are necessary.
As Atik said: No voltage over 13.8V - it should be OK.

Thanks a lot,
Max

[GH-ATIK]

Hi Max ,


perfect win-win-situation 

Thank´s a lot

Gerhard