14 replies to this topic

[riot1013]

Ok guys I could use some help here as I have reached the end of my patience with this. I have taken multiple hours of exposures of the Veil Nebula over the last few weeks. All of the individual images look great, stars focused and round. After stacking, the final image has a large blurred region starting in the middle and moving up covering the 12-1 o'clock region of the image, almost like it is out of focus.

I am stacking in DSS, imaging with a T3i. I have never had issues like this before and I'm beyond the point of frustration. Has anyone had issues like this before?

[einarin]

Look if you have unfocused or trailed stars. DSS have hard time stacking those.

And try to tweak with star selection threshold.

Could put some images somewhere for us to investigate.

[jgraham]

This is a symptom that DSS is having trouble locking onto stars in that region of the image. Try turning the threshold down. It defaults to 10%, but I routinely use 5% or even 2% for problematic images.

[riot1013]

Look if you have unfocused or trailed stars. DSS have hard time stacking those.

And try to tweak with star selection threshold.

Could put some images somewhere for us to investigate.

Like I said, all of the individual images are tightly focused.  I have taken hundreds of images and I have never seen this happen before.  It's really strange though, if I stack all of the images from June 17th, when I started this series of images, I have no issue.  If I include images from the 18th or the 25th, they blur.  I've checked for fogging and there was nothing....I'm at a loss.

[riot1013]

How do you attach images?

 

*Edit - Nevermind

Edited by riot1013, 26 June 2017 - 12:28 PM.

[riot1013]

Here is one of the DSS autosaved stacked images.  Now that I look at it I probably should have uploaded one of the final stacked images, but I will have to do that when I get home.  All of the images that went into this stacked image were perfectly focused just like the bottom half of this image.  I probably compressed it a bit too much to get a good view of the bottom half, but you get the point.

Edited by riot1013, 26 June 2017 - 12:40 PM.

[riot1013]

Here is one of the 2 minute subs that went into this image.  Every sub looks just like this.  I sorted all of them prior to stacking.  Like I said before I have no idea why it is stacking them and blurring that huge section of the image.

[riot1013]

This is a symptom that DSS is having trouble locking onto stars in that region of the image. Try turning the threshold down. It defaults to 10%, but I routinely use 5% or even 2% for problematic images.

I will try that when I get home

 

*Edit - I tried stacking at 2% and 20% to no avail.  I'm currently trying to stack in PI to see if it makes a difference.  I'm beginning to think that my camera may have just died....but I still keep going back to the individual subs which on their own look fine.

Edited by riot1013, 26 June 2017 - 04:07 PM.

[riot1013]

Here is another 2 minute sub from last night.

[scott4comp]

Do you delete the Master Flat and Master Dark from previous operations ?

 

Calibration might be off.....

[RedLionNJ]

As Scott suggested above, delete all the computed masters. Sometimes the forced rebuilt of these can make a difference and I have NO idea why.

 

So tell me - you imaged on three nights, right?  If you stack each night individually, each night on its own is fine?

 

If that is indeed the case, then my best guess is that the image scale is slightly different from night to night (temperature -> tube length -> focal plane -> slightly different f/ratio), so slightly different image scale?

 

DSS does not generally deal well with images of varying scales, so perhaps this is the source of the issue?

[riot1013]

If I stack the images from each night separately, the first night's images will stack fine the other two will not. I got tired of dealing with it and I ended up buying a new camera so we will see how that pans out.

[einarin]

Likely not camera fault but...

[riot1013]

I think I figured it out. I am pretty sure my flat frames were bad. I used some older flats and stacked some of the newer subs with no issues. Time to try it on all of the images.

[riot1013]

Likely not camera fault but...

I needed an excuse....plus I got a smoking deal on a Canon 80d; less than 800 for the camera and 18-55mm lens. The original price was over 1500 so I think I made out ok.

Edited by riot1013, 28 June 2017 - 12:36 AM.