Dust on DSLR sensor?

[TerraC]

Hi all

Just looking for a bit of advice.

Having trouble with dust and cleaning telescope glass, field flattener.  It just seems to get everywhere and wont stay away.  Need some anti static cleaner maybe?

Crude stretch of a quick test in nowhere near ideal condition but I think these dots could be dust on DSLR sensor rather than on the FF or scope?  I think i'll need to have a go at cleaning the sensor with some swabs. 

What could be causing the blue line?

I think i'm getting a bit of walking noise too.  Just started using an EQ5 without guiding right now so i'm not dithering yet until I get my guide scope all setup.  I used to use an AZGTI and the accuracy wasnt good enough to need to dither, it dithered on it's own.  

 

Thanks

Ray

 

[malc-c]

I'm no expert but to me dust would be random and not in a straight line across the sensor.  The darker splodges towards the bottom of the image is more like your traditional "dust bunny".  Not sure if using a liquid lens cleaner would be safe on a bare CCD sensor, so a normal puffer used to blow dust away might work.

[alacant]

1 hour ago, TerraC said:

i'll need to have a go at cleaning

Hi

No need to clean as no matter how hard you try, you'll never get rid of all the dust in the optical train. 
Unless the sensor is damaged, flat frames will correct the dark areas and tidy your image in other ways.

We don't know what DSLR you used so can only guess, but the blue banding could be a defective row of pixels on the sensor, you've left the memory card in the camera, electrical interference, a faulty cable, introduced by old camera firmware...  In any case, it's easily removed in processing.

Cheers and HTH

Edited April 6, 2023 by alacant

[TerraC]

Thank you. Its a Canon 550d. The line has only appeared recently along with the dust spots. Ill try the calibration frames on next attempt. 

Ray

 

[michael8554]

Hi Ray

The 600D is known for banding, and the 550D is the same camera, but without the swivel screen.

But a much darker band is unusual. 

What ISO ?

The dust bunnies are very defocused, so are not on the sensor IMO.

Michael

[TerraC]

Iso on this one was 400. Trying to combat a bright moon. Iso800 blew out the sky. 60x 1min exposures. 

Ray

 

[alacant]

4 minutes ago, TerraC said:

Iso on this one was 400

Hi

Keep the ISO at 800. 

600d, so take no dark frames of any sort. Simply calibrate the light and flat frames by subtracting the offset. The easiest way to do that is by using Siril, the added advantage of which is that it will also take care of any banding.

Cheers and HTH

[michael8554]

Hi Ray

It's not the ISO that "blew out the sky", it was the length of the exposure.

Stick on ISO800 and reduce the exposure length.

Michael

[TerraC]

Hi guys

So id be better off keeping at iso800 and doing twice the number of exposures at say 30sec so as to keep the histogram 1/3rd from the left? 

Ray

 

[alacant]

56 minutes ago, TerraC said:

So id be better off keeping at iso800

Yes.
 

56 minutes ago, TerraC said:

twice the number of exposures at say 30sec

No. Take as many exposures as your patience allows.  Use an exposure which  keeps the histogram centre or left thereof; the 18Mp sensor can take quite a bit of thrashing.
Pick a target away from the moon. 

Cheers and HTH

[TerraC]

Unexpected clear night and late rising moon means ive managed an hour and a half of 60sec iso800 exposures tonight. Grabbed some calibration frames and will see if i get anything in the morning   

Ray