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Chroma 3nm orientation

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15 replies to this topic

#1 Ken82

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Posted 30 June 2020 - 05:29 PM

Just received my chroma 3nm filter 😀

 

In terms of orientation I know the arrow must point towards the specimen (nebula) although my filter doesn’t have any markings ?

 

Both sides are mirror like so can’t be distinguish.

Any ideas ?

 

Thanks

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#2 Monkeybird747

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Posted 30 June 2020 - 07:17 PM

Dick at Chroma says it doesn’t matter, but he also tells customers to flip them if they think they have a problem. I just noticed a reflection around a bright star in my most recent project with the 3nm O3 that is a little concerning. Have not been able to start troubleshooting, but flipping the filter is on my list. Right now I have the bottom of the letters toward the camera. No idea if that is correct or if it truly makes a difference.

MB

#3 John Miele

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Posted 30 June 2020 - 07:49 PM

Hard to believe filter makers don't put a tiny index arrow on their unmounted filters but they don't. I have a full set of Chroma and had to guess as well. Both sides looked too close to tell a difference...shrug.gif


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#4 Ken82

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Posted 01 July 2020 - 04:17 AM

Yea both sides of mine look identical. I even tried shining a torch onto the filter to see if one side is less reflective. I know there is nothing scientific about my test but both sides reflect like a mirror, that is a concern.

@monkeybird747 how many pixels across is your halo ? Any images you could share ?

#5 Tayson82

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Posted 01 July 2020 - 05:08 AM

Star ηGem Propus.

 

Wrong orientation Ha 5nm Chroma

chroma5nm.JPG

 

 

baader 7nm - chroma 5nm good side - chroma 5nm wrong side

baader_chroma_chromaodwrotnie.JPG

 


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#6 Monkeybird747

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Posted 01 July 2020 - 08:44 AM

Tayson82, that’s very interesting. Thanks for sharing. So can you tell us what is the proper orientation? This is assuming Chroma orients the writing on the edge the same way for all filters. Are those mounted or unmounted?

I have the Chroma LRGB as well, and you can see a difference between sides just looking at the filters.

The halo/reflection I have with my O3 looks identical to your Baader 7nm image. I’m hoping flipping the filter will have an effect.

Edited by Monkeybird747, 01 July 2020 - 08:46 AM.


#7 dghent

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Posted 01 July 2020 - 08:52 AM

Hard to believe filter makers don't put a tiny index arrow on their unmounted filters but they don't. I have a full set of Chroma and had to guess as well. Both sides looked too close to tell a difference...shrug.gif

Are index arrows necessary when which side is "up" doesn't matter?



#8 Tayson82

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Posted 01 July 2020 - 09:20 AM

So can you tell us what is the proper orientation?

I found some photo. 

Bottom of the text to sky.

 

https://astropolis.p...&comment=757505

ha.jpg


Edited by Tayson82, 01 July 2020 - 09:26 AM.

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#9 Ken82

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Posted 01 July 2020 - 10:07 AM

Thanks Tayson 👍

Chroma responded to my email -

We do not mark filters for orientation because these are front-surface
sputter coatings with anti-reflective coatings on the back surface. Most
systems will not notice any difference in performance regardless of
orientation.

#10 Peter in Reno

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Posted 01 July 2020 - 11:06 AM

I found some photo. 

Bottom of the text to sky.

 

https://astropolis.p...&comment=757505

attachicon.gifha.jpg

I suggest to get filter masks from:

 

http://buckeyestarga...FilterMasks.php

 

Here's mine:

 

https://www.cloudyni...but/?p=10175913

 

Peter 


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#11 Monkeybird747

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Posted 01 July 2020 - 11:18 AM

I found some photo.
Bottom of the text to sky.

https://astropolis.p...&comment=757505
ha.jpg


Thanks Tayson, that’s opposite the way mine are, so I’ll give that a try.

#12 numchuck

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Posted 01 July 2020 - 12:43 PM

some 36mm Astronomik that I have , are mounted so that the glass is closer to one side of the frame than the other ; so I place them , such that , the glass is closest to the camera sensor .



#13 Ken82

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Posted 01 July 2020 - 04:06 PM

I suggest to get filter masks from:

http://buckeyestarga...FilterMasks.php

Here's mine:

https://www.cloudyni...but/?p=10175913

Peter


Yea I’ve also got them Peter 👍

#14 phototech

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Posted 01 July 2020 - 06:22 PM

Star ηGem Propus.

 

Wrong orientation Ha 5nm Chroma

attachicon.gifchroma5nm.JPG

 

 

baader 7nm - chroma 5nm good side - chroma 5nm wrong side

attachicon.gifbaader_chroma_chromaodwrotnie.JPG

How do you tell which is the good and wrong side ?



#15 sharkmelley

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Posted 02 July 2020 - 01:35 AM

Star ηGem Propus.

 

Wrong orientation Ha 5nm Chroma

attachicon.gifchroma5nm.JPG

 

 

baader 7nm - chroma 5nm good side - chroma 5nm wrong side

attachicon.gifbaader_chroma_chromaodwrotnie.JPG

That's very interesting fringing around the bright star when mounted the wrong way. 

I wonder what causes it?

 

Mark



#16 ezwheels

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Posted 02 July 2020 - 01:42 AM

gravitational lensing wink.gif


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