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ZWO filter orientation

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#1 miwitte

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Posted 01 March 2018 - 03:29 PM

I am finally going to get a couple of nights of being able to use scope (since Dec) and I just received my ZWo 36mm filter masks so I want to get them in tonight or tomorrow. I've see a bunch of threads on this, and I've used the ZWO site for how to determine orient when I got them in august, I just wanted to double check these as long as I have it apart. Ive reached out to ZWO and not much help. Also it appears they changed the pictures I remember that the LRGB was backward from the NB stuff and a different pic. Just looking for the right way and verify if ive go them in correctly.

 

the LRGB is really hard to see what I chould be looking for

ZWO LRGB.jpg

 

 

The NB camera side

 

ZWO NB Camera side.jpg

 

ZWO NB scope side

 

ZWO NB scope side.jpg

 



#2 the Elf

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Posted 01 March 2018 - 04:22 PM

NB and L are doing very different things, so one looking almost opposite to the other is correct. NB allows very little light to go through while reflecting most of it back -> scope side looks like a mirror. The active layer is on this side. Camera side: this is the glass side and the multiple reflections are generated between the glass and the active side.

L does a different job: anything that you can see with your eyes can pass. It reflects UR/IV but you cannot see it. The scope supposed to look a bit like a metal surface while the camera side should look like non refective glass. I'm working with industrial filters a lot. I'd say as a rule of thumb the active side is always one the lens/scope side.

If you really insert them the wrong way it wont ruin everything. You will (might perhaps?) see halos around bright stars. If you want to be 200% sure, take a test shot of a very bright star (not placing it in the center) in both directions and compare the images. This should reveil the truth!



#3 miwitte

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Posted 02 March 2018 - 09:17 AM

So only one person here has input on the correct way to put these in? I know there are a TON of us with this setup. I'm pulling it apart to put the masks in and clean things and want to verify that I installed them correctly last year. I finally have some clear weather AND I'm home.



#4 AstroPics

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Posted 02 March 2018 - 10:20 AM

You really need to just follow the images from ZWO.

 

Make sure you lay down some white paper (e.g. PEC wipes for instance) with the filter on it. Take a flashlight (and move it around) pointed at the the filter to identify the anti-reflective side (with the cascading rings). It can be really tricky with the LRGB filters (some are easier to identify than others). Be patient and make sure you are confident you have correctly identified the anti-reflective side. I found the Luminance filter the hardest one to identify. Just keep moving the flashlight around to find the right angle.

 

The NB is fairly easy to work with using the pen test (and looking for a double image).


Edited by AstroPics, 02 March 2018 - 12:36 PM.


#5 miwitte

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Posted 02 March 2018 - 11:47 AM

Thnaks that's exactly what I was looking for. I did work through the instructions on ZWO, but they are using different photos from what I remember. for both the non reflective side should face camera correct? I seem to remember the old instructions they were backwards on the LRGB side.



#6 AstroPics

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Posted 02 March 2018 - 12:36 PM

I think ZWO did change their stance on the orientation of the filters but now they want the anti-reflective coating to face the camera. By the way, I went back and edited my original post.... The cascading rings on the LRGB are the anti-reflective side!



#7 miwitte

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Posted 02 March 2018 - 12:52 PM

yeah the NB seems more straight forward. Inow see what you mean by the rings ill look for that.

I could have sworn they changed it at least I'm not crazy! I'm going to pull it apart this afternoon, clean them and reinstall with the masks ZWO sent. This is the first time I've had a clear night AND I've been home since middle of Dec so looking forward to getting out tonight and this weekend.

#8 the Elf

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Posted 02 March 2018 - 04:43 PM

miwitte, you are going to use the NB, don't you? There is this thing out, what was it's name? Ah, full moon. My sky is like milk and an can see about 11 stars with my bare eyes. Hope you get something decent!



#9 freestar8n

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Posted 03 March 2018 - 04:55 PM

So only one person here has input on the correct way to put these in? I know there are a TON of us with this setup. I'm pulling it apart to put the masks in and clean things and want to verify that I installed them correctly last year. I finally have some clear weather AND I'm home.

I haven't heard a clear explanation for why one way is better than the other.  And I haven't seen a comparison showing that one way is better than the other.

 

The arguments about reflections and so forth don't work for me because the transmission in the passband is the same either way.

 

For ZWO filters there may be a preference because they may not be coated all the way to the edge - and that combined with the filter holder will mean there is more light leak one way than the other.  But that has nothing to do with which side is reflective or something.

 

So without knowing the actual reason ZWO recommends it one way vs. the other - I don't think it's anything to worry about.

 

And if you do find halos are worse one way than the other - or something - that would be the first example I'm aware of to show the orientation matters.

 

Frank



#10 NuclearRoy

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Posted 26 May 2019 - 08:56 PM

I just installed the 36mm filter set and I know it's too late for the OP but in case anyone is searching for info in the future and ends up here like I did, here is my suggestion.

Start with the Green filter.

It is like night and day. Very easy to see which side is the AR coated side. That will at least let you see what you are looking for.

Good luck with the L filter. I spent 15 minutes trying to see a difference and never could be sure...




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