Back to forums

Filter burst, peeled off

ZWO O-III 7nm Filters OIII Troubleshooting
14 replies•253 views
Skender Kajoshaj avatar
Skender Kajoshaj avatar
Strangest thing …. I noticed a dark patch on my subs and thought there might be dust on the camera protection glass … But then i sëe that the OIII has sonehow "burst" … not the glass itself but one side the coating is literally as if it had been eaten by acid or something - so there were pieces of this glitter everywhere.

I removed the filter and ordered another one (Optolong this time).

But it is strange that this only happened to the OIII … What coukd have caused such a thing?

The filters are 36mm unmounted.
andrea tasselli avatar
andrea tasselli avatar
Water infiltration might do the trick.
Dave Erickson avatar
Dave Erickson avatar
Most likely compressive stress from IBS coatings overcoming surface adheasion, the coating cracking and flaking off. This is a rare occurance due likely to improper surface preparation. Either a substrate polishing issue or a cleaning prior to coating issue.

I either case the coating manufacturer will, should, replace the defective filter.

Best,
Dave
Helpful Concise
Skender Kajoshaj avatar
Skender Kajoshaj avatar
Now I have again another, even darker patch ... I tried looking where it is, it seems again it is on the camera protection glass. Just hoping it is not some worse thing like oil leak or so?

In any case, since I use an OAG and filter wheel, all of them are BOLTED to each other, so I would have to unscrew each part separately to get to that glass which is really a chore.

What do you guys think? Here is a sub, where you can see the patch (it is on all filters, so it must be on the protection glass again, I hope at least):

andrea tasselli avatar
andrea tasselli avatar
Flattening the lights should remove the patch. I had worse.
Skender Kajoshaj avatar
Skender Kajoshaj avatar
andrea tasselli:
Flattening the lights should remove the patch. I had worse.

Well, I did that of course, it did not remove it quite well, it actually "multiplied" it so I got some insectlike "eyes" ... I really do not want to unmount and unscrew everything again.
andrea tasselli avatar
andrea tasselli avatar
Then obviously the flat isn't doing its work too well so the question really is: why it doesn't do that? As per one recent thread about flats over/undercorrecting the light that are different possible reasons for that. So, to get started, what the flats look like?
Skender Kajoshaj avatar
Skender Kajoshaj avatar
andrea tasselli:
Then obviously the flat isn't doing its work too well so the question really is: why it doesn't do that? As per one recent thread about flats over/undercorrecting the light that are different possible reasons for that. So, to get started, what the flats look like?

Skender Kajoshaj avatar
Skender Kajoshaj avatar
Skender Kajoshaj:
andrea tasselli:
Then obviously the flat isn't doing its work too well so the question really is: why it doesn't do that? As per one recent thread about flats over/undercorrecting the light that are different possible reasons for that. So, to get started, what the flats look like?

Master Flat from PI:

Skender Kajoshaj avatar
Skender Kajoshaj avatar
Look at the repetition:

andrea tasselli avatar
andrea tasselli avatar
So it overcorrects. What is the procedure you use for calibration and are you using WBPP?
Skender Kajoshaj avatar
Skender Kajoshaj avatar
andrea tasselli:
So it overcorrects. What is the procedure you use for calibration and are you using WBPP?

I normally don't use PI for stacking and integration. I use AstroPixel Processor.
This is why, after APP I thought I will try WBPP in PI, but the results were largely the same. I just used "default" settings in WBPP because TBH as I said I have never used it for this, so I do not know what setting is important or what one must change etc.

In APP I load all lights, flats, flat-darks and also the Master Dark and BadPixelMap. This is the procedure I always used for all my photos.
andrea tasselli avatar
andrea tasselli avatar
WBPP is a BAD idea if you don't what you are doing (and also if you know but this is another story).

1. Master flat to be obtained from flat frames - dark flat master using ImageCalibration. Make sure the dark-flat master contains the bias, has the same offset and gain of the flats.
2. Once calibrated use ImageIntegration to create the master flat with the settings shown below:

Next to calibrate the lights...
andrea tasselli avatar
andrea tasselli avatar
To calibrate you need to obtain a master dark (same offset and gain of the lights, same temperature and duration obv.) . The master dark must contain the bias. If you aren't sure do it again in PI using ImageIntegration.

3. Fill in the form as shown below (assuming you are using a mono camera:



4. Use StarAlignament to register the lights (here we skip a couple of step as non critical for the issue at hand):

5. Run LocalNormalization using as reference frame the same you used previously for registering the lights:



5. Integrate the registered lights and make sure to add the local Normalization files
Skender Kajoshaj avatar
Skender Kajoshaj avatar
andrea tasselli:
To calibrate you need to obtain a master dark (same offset and gain of the lights, same temperature and duration obv.) . The master dark must contain the bias. If you aren't sure do it again in PI using ImageIntegration.

3. Fill in the form as shown below (assuming you are using a mono camera:



4. Use StarAlignament to register the lights (here we skip a couple of step as non critical for the issue at hand):

5. Run LocalNormalization using as reference frame the same you used previously for registering the lights:



5. Integrate the registered lights and make sure to add the local Normalization files

Thank you for the instructions. I will try this.