ZWO ASI 120 MC coloured dots??

[Skipper Billy]

I am trying to set up an all sky camera and its outside now for first light after much testing indoors.

The attached image was taken a few minutes ago and as the sky has got darker lots of coloured dots have appeared.

I have never used a colour camera before so please excuse my ignorance !!

I have turned the gain down to 50 but all it seems to have done is make the image darker - the coloured dots are still there.

Is this 'noise' or something else ??

Attached an image from just now and one from earlier when the sky was much lighter.

HELP !!

[Laurin Dave]

Looks like hot pixels to me..  what software are you using? Can it do automatic dark or bad pixel map subtraction ?  

[Jonk]

Yes this is noise - it is much reduced when the sensor temperature is lower.

In experiments with / without a peltier cooling the camera body of my ZWO 178MC, there was a marked difference in cooled vs uncooled colour noise.

It also appears to be read noise - longer exposures were less noisy than multiple short ones.

If you're new to it, just experiment with all settings / exposures etc until you xero in on the best you can get, which will be different every night!

[Skipper Billy]

10 minutes ago, Laurin Dave said:

Looks like hot pixels to me..  what software are you using? Can it do automatic dark or bad pixel map subtraction ?

It can do automatic dark subtraction - its not set up yet - I will try that but I wanted to be sure to know what the issue is before altering anything.

6 minutes ago, Jonk said:

Yes this is noise - it is much reduced when the sensor temperature is lower.

In experiments with / without a peltier cooling the camera body of my ZWO 178MC, there was a marked difference in cooled vs uncooled colour noise.

It also appears to be read noise - longer exposures were less noisy than multiple short ones.

If you're new to it, just experiment with all settings / exposures etc until you xero in on the best you can get, which will be different every night!

I may have made things worse than neccesary then - I have drilled holes through the base under the dome to allow heat from the Raspberry Pi into the dome in an effort to reduce dew/frost on the dome!

I will have a play.

Thanks both for your help.

[Jonk]

In my testing, heat from the camera or small mini pc is not enough, you will probably need a heating element of some kind.

[Laurin Dave]

Hi David..  I use AllSkyEye software and have a ZWO dew heater strip to prevent mine misting up.  Other use the ones from Dewcontrol.com 

Dave

[Gina]

Yes, I use the heater from Dewcontrol.com.  And I cool the camera with a Peltier TEC.

[Skipper Billy]

Sorted - dark subtraction made a massive difference - given that to the naked eye its blanket cloud outside and I cant see a single star I am more than happy with this test ! 　It's a ZWO ASI 120MC - uncooled.

The Raspberry Pi puts out a fair amount of heat so I will wait and see if I need to add a dew hetare.

This is a great improvement......

[Laurin Dave]

Certainly is  ..  presumably through the cloud 

Edited March 13, 2020 by Laurin Dave

[Gina]

Several constellations showing.  Pretty good that.  Must try dark subtraction on mine when I get it working again.

[MimasDeathStar]

I'm really sorry if this sounds like I'm hijacking your thread - but... is that the lens that came with the camera or is that a difference lens? I'm thinking about buying one of these cameras you see!

Great shots btw really pleased you fixed the picture issue. These all sky projects look amazing fun but I think they may be a touch too technical for me!

[Skipper Billy]

Its not the original lens - its an Arecont 180º from the USA. The orginal lens gives about 140º

Its not a difficult project - I have never used Linux before so if I can do it - you can !

The info is here - https://www.instructables.com/id/Wireless-All-Sky-Camera/?fbclid=IwAR0MBp6cGOPtSg-HegsgeWlneg9YHLHxmzI7CjYWvm_j-UrQgEYyWSYf0J4#step1

Once I get it working properly I will post some photos and info.

[happy-kat]

The dark subtraction worked great

[tooth_dr]

Thats a great result, from a cheap wee camera.  The dark subtraction made a huge difference.

[happy-kat]

How long were your exposures please? Like 5 seconds or less?

[Skipper Billy]

2 hours ago, happy-kat said:

The dark subtraction worked great

 

1 hour ago, tooth_dr said:

Thats a great result, from a cheap wee camera.  The dark subtraction made a huge difference.

I must admit I was shocked at the improvement!

[Skipper Billy]

9 minutes ago, happy-kat said:

How long were your exposures please? Like 5 seconds or less?

30 seconds.