Weird circle

[serbiadarksky]

As the title of this section says general help, i will post it here too..

This image is stretched to reveal the dust, contains 22x5min ISO1600 F4 images all stacked in Photoshop to reduce the noise (no dss/pix is not helping me but thats for another post). I get this weird circles around my image, I checked remove vignette in photoshop while stacking..I dont use any flats/bias or darks as I never needed it, even if I have several images stretched even more withouth any problems. Oh and I use a dslr with a cls clip in filter..

Any idea on removing it?

[teoria_del_big_bang]

I am fairly new to this but could it be Newtons rings?

Search on this forum (or in Google) for Newtons Rings there is lots of info about it.

https://photo.stackexchange.com/questions/41433/what-causes-faint-circles-in-astrophotography-images

Sorry if it is not this ? 

Steve

[coatesg]

They do look like Newton's Rings, but I'm not entirely sure where they could occuring from (plus, they tend to be seen in narrowband rather than broadband imaging). The classic case is where you have a sphere touching a flat surface, but that sounds odd for this situation. 

What lens are you using, do you have and filters in place (front or back) and is the camera modded at all? 

Also, give DSS a go - the free version works well, and it'll improve the S-N by properly stacking the data.

[serbiadarksky]

1 hour ago, coatesg said:

They do look like Newton's Rings, but I'm not entirely sure where they could occuring from (plus, they tend to be seen in narrowband rather than broadband imaging). The classic case is where you have a sphere touching a flat surface, but that sounds odd for this situation. 

What lens are you using, do you have and filters in place (front or back) and is the camera modded at all? 

Also, give DSS a go - the free version works well, and it'll improve the S-N by properly stacking the data.

I use the 50mm f1.8 at f4, Baader modified and I use a cls clip in by astronomik

[Cornelius Varley]

Moved to imaging section.

[serbiadarksky]

11 minutes ago, Cornelius Varley said:

Moved to imaging section.

Thank you!

[Thalestris24]

Ice on lens? What are flats like?

 

[TheMan]

6 hours ago, serbiadarksky said:

I dont use any flats/bias or darks as I never needed it.

 

Time to start using calibration frames. You will be amazed with what they can do.

[serbiadarksky]

1 hour ago, TheMan said:

Time to start using calibration frames. You will be amazed with what they can do.

I fixed the circles are gone, just stacked them in Photoshop with vignette removal turned off.

And I tried them before, messed up my stack so i dint use them.

[serbiadarksky]

1 hour ago, Thalestris24 said:

Ice on lens? What are flats like?

 

 

1 hour ago, Thalestris24 said:

Ice on lens? What are flats like?

 

No ice, no dew, nothing.

No flats as I said.

[ollypenrice]

It's good that you've fixed it but you do need flats! Everybody does. Darks maybe not. Just try a master bias instead of a dark.

Olly

[serbiadarksky]

1 hour ago, ollypenrice said:

It's good that you've fixed it but you do need flats! Everybody does. Darks maybe not. Just try a master bias instead of a dark.

Olly

Thanks

yes darks are my biggest problem due to hige difference in temperature..

[ollypenrice]

Just now, serbiadarksky said:

Thanks

yes darks are my biggest problem due to hige difference in temperature..

That's why so many DSLR users don't use them. I don't even use them on set point cooled CCD cameras. I find they introduce noise.

Olly

[serbiadarksky]

29 minutes ago, ollypenrice said:

That's why so many DSLR users don't use them. I don't even use them on set point cooled CCD cameras. I find they introduce noise.

Olly

Exacrly..it bringed me more noise than dark free image

[tooth_dr]

2 hours ago, ollypenrice said:

That's why so many DSLR users don't use them. I don't even use them on set point cooled CCD cameras. I find they introduce noise.

Olly

Hi Olly

I think I get myself confused!  With my Kodak KAF-8300 sensor, i use darks, flats (6.5s), dark flats (6.5s), bias frames, and a BPM.  I use astropixel processor, which generates the calibration files that you can click on and look at.  Are there any of those calibration frames that I dont need in your opinion?#

 

Thanks

Adam.

[geordie85]

1 hour ago, tooth_dr said:

Hi Olly

I think I get myself confused!  With my Kodak KAF-8300 sensor, i use darks, flats (6.5s), dark flats (6.5s), bias frames, and a BPM.  I use astropixel processor, which generates the calibration files that you can click on and look at.  Are there any of those calibration frames that I dont need in your opinion?#

 

Thanks

Adam.

When I used to image with my 383L I never used darks. I also used flats of 2 seconds and never had any issues. 

I only use darks now with my qhy183c because of the amp glow. 

[tooth_dr]

1 minute ago, geordie85 said:

When I used to image with my 383L I never used darks. I also used flats of 2 seconds and never had any issues. 

I only use darks now with my qhy183c because of the amp glow. 

I honestly can’t use flats under 3 seconds or I can see a small dark rectangle in the bottom right corner from the shutter.  I’ll drop the darks though.

Do I load a bias in as a dark and also use that bias as well as a bias, or just don’t use a dark? What about a BPM? Can I still make that from the dark or do I make it from the bias?

Sorry for hijacking the thread ? 

[Thalestris24]

28 minutes ago, tooth_dr said:

I honestly can’t use flats under 3 seconds or I can see a small dark rectangle in the bottom right corner from the shutter.  I’ll drop the darks though.

Do I load a bias in as a dark and also use that bias as well as a bias, or just don’t use a dark? What about a BPM? Can I still make that from the dark or do I make it from the bias?

Sorry for hijacking the thread ? 

Hi Adam

The exposure duration of flats isn't overly important - you can adjust illumination accordingly. I take mine against a plain wall with low light which can be twilight or tungsten bulb light. The spec for the 383l+ says 0.2s min exposure. Suggests your shutter might need a service?

Louise

[tooth_dr]

Just now, Thalestris24 said:

Hi Adam

The exposure duration of flats isn't overly important - you can adjust illumination accordingly. I take mine against a plain wall with low light which can be twilight or tungsten bulb light. The spec for the 383l+ says 0.2s min exposure. Suggests your shutter might need a service?

Louise

 

Hi Louise

Thanks for the reply - there isnt anything wrong with my camera or shutter. It’s a common feature of the mechanical shutter in the 383L+ (and other cameras with the same sensor) that flats need to be 3+ seconds to avoid shutter swipe.

 

??

Adam

 

 

[carastro]

Yes I had a same problem when I had an Atik383L just had to do longer flats and dim the light source (as suggested by Atik themselves).  Known thing with this camera.

Carole 

[Thalestris24]

Yeah, just checked my 383 flats and they were taken at 4.5s, though I thought the camera could, in principle, do shorter exposures. The manual says exposures should be at least 200ms/0.2s. It's not a biggie  

Louise

[carastro]

You can do shorter exposures with the Atik383L Louise, i.e. Bias, but that is because the lens cap is on and you don;t get any effect of shutter shadow.

I am not sure how it works with looping, I presume the shutter stays open all the time.

Carole 

[Thalestris24]

1 minute ago, carastro said:

You can do shorter exposures with the Atik383L Louise, i.e. Bias, but that is because the lens cap is on and you don;t get any effect of shutter shadow.

I am not sure how it works with looping, I presume the shutter stays open all the time.

Carole 

That makes sense! I think I probably read about a 2s minimum somewhere before - but, being old, I forgot ?