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Old 08-02-2019, 07:21 AM
dan_iana (Daniel and Iana)
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Unsure which narrowband filters belong to which subs

Hey all,

Took some narrowband subs of M42 last night on our new ASI1600mm-pro.

What's the easiest way to tell which filter created each subs? I have labelled our filters in the filter wheel as H/S/O based on their packaging but the images that came out were quite surprising and made me think that possibly the filters where in incorrectly labelled packages (we bought them off a iceinspace user).

I'll post them tonight BUT at the following parameters (-10 sensor temp, 300 gain/50 brightness, mono8, 180sec subs):

Halpha - showed the least detail
Sii - showed a huge amount of detail but the core was massive and white
Oiii - similar to Sii

I've tried to find M42 narrowband subs to compare ours against but would have thought that (generally) Halpha would show the most detail when compared with Si/Oiii (but guess it depends on what you are imaging).

So ultimately, I just want to make sure that my filters are labelled correctly

Will post photos tonight, unless there is an easy way (e.g. look at some histogram in sharpcap or Adobe) to identify the filters based on the wavelength of light registered.
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Old 08-02-2019, 07:24 AM
glend (Glen)
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Well if your imaging with a program like SGP, it puts a designation on the file name depending on the filter selected.
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Old 08-02-2019, 08:20 AM
dan_iana (Daniel and Iana)
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- I took the filters out of the used packaging
- I put them in the filter wheel and noted the position-filter
- I put my subs in their respectively named folders based on step 2.

My concern is I am uncertain whether the narrowband filters were placed into the correctly labelled packages when I received them. All my files are grouped appropriately but I have the feeling based on the images that the filters have been put into the wrong packages (e.g. halpha put in the si filter sleeves).

So is there an easy way to tell which image would generally correspond a filter?
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Old 08-02-2019, 08:22 AM
dan_iana (Daniel and Iana)
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This is the sub which corresponds with what's as labelled as Halpha.
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Old 08-02-2019, 08:23 AM
dan_iana (Daniel and Iana)
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Oiii
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Old 08-02-2019, 08:23 AM
dan_iana (Daniel and Iana)
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Si
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Old 08-02-2019, 08:33 AM
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traveller (Bo)
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The easiest way is using a spectrometer, but not everyone has one at their disposal.
Are they ZWO NB filters?
Can you take a photo of them and share, quite of few of us have ZWO NB filters so a visual comparison is probably the best way to go.
Judging by the photos, looks like the Ha and Sii mixed up, Oiii looks ok. But that depends on your exposure time, offset and gain settings etc.
So open up the filter wheel and show us the guts!
Bo
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Old 08-02-2019, 08:40 AM
glend (Glen)
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Yes given the target I would suggest Ha and Sii are mixed up. Some filter brands are easy to work out by looking at them (like Baaders).

You can always check by aiming at a target with minimal Sii.
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Old 08-02-2019, 08:54 AM
JA
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Quote:
Originally Posted by dan_iana View Post
Hey all,

Took some narrowband subs of M42 last night on our new ASI1600mm-pro.

What's the easiest way to tell which filter created each subs? I have labelled our filters in the filter wheel as H/S/O based on their packaging but the images that came out were quite surprising and made me think that possibly the filters where in incorrectly labelled packages (we bought them off a iceinspace user).

I'll post them tonight BUT at the following parameters (-10 sensor temp, 300 gain/50 brightness, mono8, 180sec subs):

Halpha - showed the least detail
Sii - showed a huge amount of detail but the core was massive and white
Oiii - similar to Sii

I've tried to find M42 narrowband subs to compare ours against but would have thought that (generally) Halpha would show the most detail when compared with Si/Oiii (but guess it depends on what you are imaging).

So ultimately, I just want to make sure that my filters are labelled correctly

Will post photos tonight, unless there is an easy way (e.g. look at some histogram in sharpcap or Adobe) to identify the filters based on the wavelength of light registered.
As a guide to which is which:
(unless you have a spectrophotometer) to test them, then, despite the various coatings, if you handhold the filter and look through the filter at a white object illuminated by daylight, then :

1. The Halpha filter will show a deep red tinge
2. The OIII filter a green tinge
3. The SII filter a darker image than that observed in the Halpha filter as this is getting close to the edge of our visual range

all subject of course to the filter bandwidth.

Look on the bright side there are only 6 possibilities.

It might also help to observe a red/green object or image such as the attached. The Halpha filter will show the RED as RED , but will show the GREEN as Dark/mid GREYish and conversely the OIII filter will show GREEN as GREEN and RED as Dark/mid GREYish , excepting any colour perception/blindness issues

Best
JA
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Last edited by JA; 08-02-2019 at 09:09 AM.
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Old 08-02-2019, 09:34 AM
dan_iana (Daniel and Iana)
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Thanks all and filters are zwo. I will take a photo of them tomorrow and post it up. I just had a go processing them and here was the result. First ever nb image.

Given some halos on brighter stars I assume I have the older zwo nb filters without the anti aliasing thing.
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Last edited by dan_iana; 08-02-2019 at 09:54 AM.
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Old 08-02-2019, 09:41 AM
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traveller (Bo)
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A great start.
The other way of telling the filters apart is in the combining stage. Use an existing image and try and combine your images to match the palette
eg. an existing M42 mapped to SHO and play around with your NB stacks to combine and match the palette and then you will be able to figure out which filter is which.
Bo
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Old 08-02-2019, 12:15 PM
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Stack the lot in one run and colour in the result☺ I ran into a similar problem and certainly have done what I suggest.
Good luck.
Alex
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