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Chroma 3nm orientation

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#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.
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#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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#17 Tayson82

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Posted 15 July 2020 - 02:25 AM

For Chroma You don't need any diafragma.

Blue Chroma vs Baader.

on Baader are very strong multiple reflection inside of filter. Black edge of Chroma eliminates this effect.

Chroma_Baader.jpg


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#18 AdamJ

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Posted 15 July 2020 - 06:28 PM

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

Mark


They look like tube currents to me, any chance that the scope cooled between the two shots?

Adam

Edited by AdamJ, 15 July 2020 - 06:30 PM.


#19 Gary Imm

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Posted 12 August 2020 - 04:36 PM

FYI, "Bottom of the text to sky" is a good place to start, but you still need to check them all.  One of mine had to be flipped the opposite way.


Edited by Gary Imm, 12 August 2020 - 04:37 PM.

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#20 jeffweiss9

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Posted 13 August 2020 - 11:27 PM

I guess the right answer is to flipping them and look for which side avoids the halo or fringing on a bright star from this discussion.   I have the same question for Astrodon filters, if someone knows any handy way by looking into the filters.   I have Gen 2E LRGB and 5nm Ha - all 50mm diameter unmounted.  There was nothing written on the glass edges and I dull-blackened them anyway to prevent edge reflections.

 

I note that Tony Hallas' recent article on Chroma filters (Astronomy Magazine, Sept 2020) says the Anti-Reflection (AR) side is distinguishable as the side you can see right through when looking into the Chroma filters and the AR ("back") side should be pointing to the sensor.    The "hard coating" on the other ('front') side is highly reflective and should be pointing toward the sky to prevent unwanted light from passing through the filter.  The article was on the Chroma L,R,G,B and Ha filters so might not apply to the Chroma OIII, or, apparently, any of the Chroma filters discussed above where the sides seem to be indistinguishable.   I have a Chroma OIII (5nm, 50mm diam unmounted) on its way from VT so am also interested in the question for Chroma filters.

 

CS/Jeff


Edited by jeffweiss9, 14 August 2020 - 01:01 PM.


#21 tjz

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Posted 14 August 2020 - 07:28 AM

Interesting. I just replaced my Baader 36mm filters with Chroma filters and had a similar dilemma. After re-reading instructions for the ZWO filters and looking at the arrows on my Baader filters, and doing that "hold a pen up and see if there are multiple reflections test", I ended up putting the shiny side up towards the stars and the AR coating down towards the camera. That resulted in bottom of letters down to the camera and top of letters up towards the stars. Having an ASI1600MM-Pro with some reflections in OIII and SII from the Baader filters, it made the most sense. So far, with a few nights of imaging (between the clouds and smoke in Colorado) there is a big improvement over the Baader filters. I have not tried flipping them to repeat the experiment, though.



#22 Monkeybird747

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Posted 14 August 2020 - 07:39 AM

FYI, "Bottom of the text to sky" is a good place to start, but you still need to check them all. One of mine had to be flipped the opposite way.


Same here. My Lum filter writing was opposite the other six filters.

#23 Monkeybird747

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Posted 14 August 2020 - 07:43 AM

Interesting. I just replaced my Baader 36mm filters with Chroma filters and had a similar dilemma. After re-reading instructions for the ZWO filters and looking at the arrows on my Baader filters, and doing that "hold a pen up and see if there are multiple reflections test", I ended up putting the shiny side up towards the stars and the AR coating down towards the camera. That resulted in bottom of letters down to the camera and top of letters up towards the stars. Having an ASI1600MM-Pro with some reflections in OIII and SII from the Baader filters, it made the most sense. So far, with a few nights of imaging (between the clouds and smoke in Colorado) there is a big improvement over the Baader filters. I have not tried flipping them to repeat the experiment, though.


This is what I did too, after reading up on the Baader filter orientation. I’ve flipped mine back and forth several times, and I just can’t see a difference. Maybe certain systems are more sensitive to this, as I’ve spoken to someone with an fsq that swears flipping solved their reflection problem.

#24 jeffweiss9

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Posted 14 August 2020 - 12:48 PM

Here's the answer for Astrodon filters from Doug Williams at Opticalstructures.com:

 

"It makes no difference. Astrodon filters are not sensitive to direction. Some other filters have coatings that are direction sensitive, but the coating methods used on Astrodon filters are not sensitive to direction or rotation."

 

CS/Jeff



#25 pyrasanth

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Posted 14 August 2020 - 01:47 PM

My Chroma OIII 3nm filter is definitely sensitive to which way it is placed in the filter wheel. If I get the orientation incorrect I get square blocks over the integrated image.  




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