Help! Is this dirt or something more?

[Larry 1969]

Hello all!

This is a lightly processed image I took last night of M81 and M82. I stacked the images in DSS and performed the 1st round of processing in StarTools. I only used the top modules and then stopped to show the abnormality.
The center seems overexposed and there appears to be dirt or dust on the sensor.
It's a Canon T3i.
I'm finally starting to figure out this whole imaging thing and now my camera is giving me fits...

Any help or suggestions appreciated.

Thanks!

Larry

[JayTee]

The interesting thing is that those two dots are repeated all over the image in the same configuration and geometry. I wonder if it is both dirt and artifacts. This is a stumper to me.

Sorry,
JT

[Larry 1969]

Thanks for looking JayTee!

I just noticed that they appear to be repeating throughout the image... The plot thickens!

I'm also curious about the bright center. This is a new scope for me and the first time I've used a coma corrector.

Larry

[Ylem]

I don’t think it’s dirt, but I could be wrong.
Would not dirt be way out of focus?

[Arsene37]

Hi !
I think there are two "abnormalities" :
[*]black dots which looks like "bokeh" in pictures with some photographic lenses (those like this one, look down for the "donought bokeh"). Maybe somme dust on the coma-corrector ?
[*]multiple reflections (the one in the center and those on the sides.
Hope this helps !
Arsène

[Micke187]

The bright center in the image is most likely to do with fog or frost on the sensor glass. I recognize it because i have had the same issue before a couple of times.

[Larry 1969]

Hi !
I think there are two "abnormalities" :
[*]black dots which looks like "bokeh" in pictures with some photographic lenses (those like this one, look down for the "donought bokeh"). Maybe somme dust on the coma-corrector ?
[*]multiple reflections (the one in the center and those on the sides.
Hope this helps !
Arsène

Thanks for the link. Those photos toward the bottom are strange and they do resemble my image. I wish it were in English.

Larry

[carastro]

I'm also curious about the bright center.

Bright centres are normally due to not taking flats for calibration.

Lack of flats could also be the cause of the black dots and other artifacts in the image, though not entirely certain about that.

Flats are hard to learn for the new imager, but they make so much difference.

Carole

[UlteriorModem]

Those are dust motes alright. Quite close to, perhaps even on the sensor. They can be nullified with good calibration flats.

Need to learn about image calibration

Also yes there appears to be frost / dew in the imaging train.

Add to that the image is strongly over stretched which just the aberrations even more apparent.

[Larry 1969]

Thanks for the replies!
I ordered a lens and sensor cleaning kit that seemed pretty nice. I cleaned everything up yesterday. Time will tell.
I also ordered an LED backlit tracing board. I plan to use it along with some white T-shirts to start taking flats!

Larry

[UlteriorModem]

Be extremely careful cleaning that sensor! Get a bulb blower, that may be all that is needed.



I cant over emphasise how easy it is to foul up a sensor and make a 'bad' situation into a catostrophie!

https://www.bing.com/videos/search?q=ho ... ORM=VIREHT

[Larry 1969]

Thanks Tom!
This is the kit I got.


And I followed their instructional video along with several others very carefully.

Larry