Dust on DSLR sensor

[emyliano2000]

Hi guys.

Trying to process the images that I took this week, I noticed some spots in the images. I thought I might have some spots on my primary but on the second thought I decided to google "dust on DSLR sensor".

I took a shot with the camera as guided by a website and, yes, there's dust on the sensor.

I bought the camera, brand new and I sent it to get it modified straight away. 

The spots become very obvious on the 60sec + exposures and when I stack and process them. I can't see them on some of the photos that I took inside my house after I got the camera back.

I'm really thinking that it might have happened during the modification process because for the longer exposures that I took I used a Baader MPCC on and I don't think it would've been possible to get any dust on the sensor.

What can I do? Should I talk to the guys who modified it and send it back??

Here are some of the photos, processed a bit to make the spots obvious.

This photo was taken today as guided by the website to check the sensor for dust.

Here are some long exposures, converted from RAW to JPG.

And here is a stacked photo converted to JPG as well

Emil

 

[emyliano2000]

I found one of the 1st photos I tried to take on prime focus. 2min ISO 100 (don't look at how bad the photo is please, I was just testing)

[wimvb]

Dust on a dslr sensor is quite common. Flat frames correct for this.

I wouldn't recommend cleaning the sensor with fluids or mechanical means, but most cameras have a cleaning function in the menu.

[emyliano2000]

2 minutes ago, wimvb said:

Dust on a dslr sensor is quite common. Flat frames correct for this.

I wouldn't recommend cleaning the sensor, but most cameras have a cleaning function in the menu

I used flats on all of them and they don't look any better. Look at the Horsehead one. The cleaning function is not working anymore because the camera has been Baader modified.

[wimvb]

The flats should have the same dust specks as the lights. During the calibration process, the light frames are divided by the flat master frame. It is then that the specks should disappear. If not, either the dust has moved, or the flat calibration is not working properly.

[emyliano2000]

Here's one of the flats

[SilverAstro]

The sensor is still covered by the Baader then, so the dust may be on top of that and amenable to cleaning without risk to the sensor itself ? Perhaps ??

Gina did some investigating I think, on ways of measuring (sharpness of outline ?) if the dust was sandwiched and thus part of the mod process, or a distance away on top of the filter.

Not part of my experience, just a late night thought for what it is worth , , ,

hope it turns out well, good luck,,

 

[emyliano2000]

9 hours ago, SilverAstro said:

The sensor is still covered by the Baader then, so the dust may be on top of that and amenable to cleaning without risk to the sensor itself ? Perhaps ??

I took the test shot to check for dust with the lens that came with the camera so it can't be on the Baader.

[Adam J]

As someone who modifies DSLR for my own use I can tell you that given the size of your dust bunnies those dust particles are likely towards the front filter, They are too fluffy to be on the sensor window itself in my opinion. The auto clean function works every time the camera is turned on and off though so if I was a betting man I would say they are on the baader replacement filter. 

Has it always had them or have they build up with use?

I go to great lengths to prevent dust getting into my sensor and this is the reason that I do a full spectrum mod with no addition glass layers / filters in front of the sensor at all. That way you can just use a rocket blower directly on the sensor window if you get a build up of dust without needing to remove the sensor. Of course that method leaves the camera only usable with a telescope and useless with a camera lens as you have not compensated for the change in focal length.  

You can get dedicated camera cleaning kits that include sensor swabs, I have used them and they don't damage the filter glass in any way, however these will not help you is if the dust is trapped between the filters. 

You can compensate for this using flats and a large dither of 50 pixels or so. 

[alacant]

11 hours ago, emyliano2000 said:

I used flats on all of them

Don't forget that the flats you use must match the light frames you took. If you re-focussed or reorientated the camera, then they'll not work. HTH.

[emyliano2000]

4 hours ago, Adam J said:

Has it always had them or have they build up with use?

I bought the camera brand new in November and I checked 2 of the photos I took inside my house right after it's been modified. I can see the dark dots in those photos.

 

4 hours ago, alacant said:

Don't forget that the flats you use must match the light frames you took. If you re-focussed or reorientated the camera, then they'll not work. HTH.

I took my flats right after I took the light. Didn't change anything apart from switching the camera to AV mode.

I emailed the person who modified it, maybe he can do something about it.

[emyliano2000]

During the  modification process was the auto cleaning function supposed to be made to work again? I've been told that because the IR filter has been replaced this function will not work anymore.

Is it safe to use my rocket blower to try to blow the dust off if it's in front of the filter. If it's safe what should I do, how should I do it?

[alacant]

39 minutes ago, emyliano2000 said:

Is it safe to use my rocket blower

Hi Yeah. Open the shutter on B and blast away. 10 or so shots will shift dust if it's on the outer surface but I doubt will shift sandwiched particles. Make sure the blower is blowing only air. Must be worth a try. HTH.

[emyliano2000]

7 minutes ago, alacant said:

Hi Yeah. Open the shutter on B and blast away. 10 or so shots will shift dust if it's on the outer surface but I doubt will shift sandwiched particles. Make sure the blower is blowing only air. Must be worth a try. HTH.

Should I wait until I get an answer from the person who modified it?

[Squiddy]

I'd say you wait, cos he might have given you some sort of warranty of his job. Let him decide your next action.

[emyliano2000]

3 hours ago, Squiddy said:

I'd say you wait, cos he might have given you some sort of warranty of his job. Let him decide your next action.

I did wait and he advised to use the blower. It made some improvement but some of the dust specs are just too stubborn or they are between the filter and sensor. I emailed him the new test shots and now I'm waiting for a reply again.

I hope I'll get it sorted. 

[Adam J]

4 hours ago, emyliano2000 said:

I did wait and he advised to use the blower. It made some improvement but some of the dust specs are just too stubborn or they are between the filter and sensor. I emailed him the new test shots and now I'm waiting for a reply again.

I hope I'll get it sorted. 

Its important to remember that a DSLR is always going to collect dust eventually. It they are shifting they are on the outer surface of the front filter. As they are all about the same size I would guess that if one is moving its likely they are all in the same location. I would try a sensor swab as my next move, opening up the sensor again is something ideally avoided.

In a Baader conversion the front anti dust / IR filter is left in place.