Moving dust particles

[Carole]

Following on from a conversation I had with Mark about my flats not removing dust particles because I thought I had accidentally rotated the camera when I did the flats the next morning.  (I can't find the thread I thought it was within my M31 High Halden thread, but seems it was posted separately).  Mark deduced that this was not the case and that the dust particles were moving.  I have now done another image and proved this indeed to be the case. I have overlaid a stretched master flat over the image switching the flat on and off and there are definitely no particles on the Master flat where they appear on the sub.  

So the master flat is subtracting a dust particle where there isn't one and not subtracting one where this IS one leaving me with a dark circle and a light circle. 

I am reluctant to turn off the EOS cleaning system that Mark suggested as I like to think my sensor is being cleaned otherwise I would surely have even more dust particles in there.  I think the only solution is not to turn off the camera between taking the subs and taking the flats.  Currently I wait until the following morning, and even if I've left the camera running during the night to do darks it normally needs re-setting by the morning.

So I think I am going to have to get myself one of those Gerd Neumann aurora flats so I can do them at the time of taking the subs.  

Any other thoughts?

Carole

[mickw]

If you are going to keep using the sensor cleaning thing you need to do the flats before turning the camera off.

As soon as the sensor cleaner operates, the dust will not be there or certainly not in the same place so it's pointless even taking flats.

If you leave the camera on the scope, no extra dust will get on the sensor anyway

[MarkS]

Switch off the auto sensor cleaning - this is still the best option by a long way.  I have gone for at least a year without acquiring any fresh visible particles of dust.

If you really want to vibrate the dust off from time to time then the camera still lets you do so - and at a time of your own choosing. 

Mark

[Carole]

That's a good idea Mark, I could switch it back on again when it is NOT during an image run.  

If you are going to keep using the sensor cleaning thing you need to do the flats before turning the camera off.

Yes I realise that Mick but I currently don't have any method of doing them during the night, and if I leave the camera on until the morning it needs switching off and then on again to made it active.  
Up until recently this "doing the flats the next morning method" has worked OK, so I never bothered to get set up for doing it any other way.  

So I am faced with two choices.  

a) Get a Gerd Neumann aurora flat.
b) Switch off the auto cleaner in the camera when I am doing imaging.

As you say, the camera is left in situ so no more dust is getting in, and I keep my flattener and CLS filter on the camera most of the time anyway.  

I think I'll have a go at switching off the auto cleaner in the first instance and see whether that works.

it's pointless even taking flats.

No it isn't because it removes most of the dust and vignetting just the odd one particle that seems to be wandering around.

Carole

[Carole]

Is it worth giving the sensor a blow with one of those squeezy bulb things to try to clear this loose particle, or do you think that might cause more problems than it cures.

Carole

[Mac]

Yes I realise that Mick but I currently don't have any method of doing them during the night

How about a light bulb and a piece of white card or even a sheet?

Works for me in the dome.

Dont forget you are not trying to get any focus, just an even illumination of something that is evenly lit.

Mac.

[Carole]

How about a light bulb and a piece of white card or even a sheet?

Yes I will have to sort something out Mac as it's not working well as things are.  Whatever it is though needs to work at DSC as well, as I don't think people will appreciate me holding up a light bulb in the middle of a field, which was why I was thinking of the aurora panels, and I was going to make some sort of box to go around them to shield the light. 

Need to put my thinking cap on. 

Carole