Terrible reflections with ZWO OIII and SII filters... what to do?

[MartinFransson]

Tonight I tried an imaging run on the area around Sadr and noticed that my ZWO filters give me really nasty reflections from bright stars (see attached)!! My Astrodon Ha-filter is lightyears better.

Is this to be expected from the ZWO filters or am I doing something wrong? Is OIII and SII always worse than Ha?

If it´s to be expected, what 31 mm or 1.25" filters would you recommend? Can´t afford more Astrodons...

[Davey-T]

Baader had this problem a while ago but it's fixed now and they guarantee no reflections / haloes so they're a good bet.

Dave

[symmetal]

I imaged the Sadr region in Ha recently using my dual scope setup and the widefield wiew with the ASI1600 with ZWO filters on the ZS61 produces a halo similar to the middle one of your three images which I assume is the Ha.

The other scope which took a narrower field view, Atik One with Baader filters on the FLT-98 didn't have the view I was primarily interested in so haven't processed. Looking at individual subs there is no halo on Sadr, just a mass of tiny radial diffraction spikes which the flt-98 produces on very bright stars. 

If you wish I can post a quickly processed image tomorrow for comparison. I haven't used the other narrowband filters so can't compare them.

Alan

[MartinFransson]

8 hours ago, Davey-T said:

Baader had this problem a while ago but it's fixed now and they guarantee no reflections / haloes so they're a good bet.

Dave

Maybe I could try a Baader OIII and see if that helps. 

Could it be the camera? Read somewhere about it lacking AR coating on the sensor glass...

[MartinFransson]

6 hours ago, symmetal said:

I imaged the Sadr region in Ha recently using my dual scope setup and the widefield wiew with the ASI1600 with ZWO filters on the ZS61 produces a halo similar to the middle one of your three images which I assume is the Ha.

The other scope which took a narrower field view, Atik One with Baader filters on the FLT-98 didn't have the view I was primarily interested in so haven't processed. Looking at individual subs there is no halo on Sadr, just a mass of tiny radial diffraction spikes which the flt-98 produces on very bright stars. 

If you wish I can post a quickly processed image tomorrow for comparison. I haven't used the other narrowband filters so can't compare them.

Alan

Yes, please post your image. Always good to be able to compare. 

[symmetal]

Martin, Here's the comparison. I've just stacked and roughly stretched the Atik subs (there were only 8 of them) to match the nebula brightness so don't use it as a comparison of camera/scope performance ,  and I've cropped and reduced them to a similar size.

ASI1600 / ZS61 / ZWO Ha filter

Atik One 6.0 / FLT-98 / Baader Ha filter

The 'scintillating' spikes on the Baader image are more a feature of the FLT-98 I believe as similar effects are present on LRGB images of very bright stars.

Alan

[MartinFransson]

That looks great! Of course it could be the scope or camera that has better coating but I might try one of those Baaders

[MartinFransson]

Would this be the correct Baader filter or are there other series? I need 1.25" mounted or 31mm unmounted.

https://www.firstlightoptics.com/baader-filters/baader-narrowband-ccd-emission-line-h-alpha-filters-125.html

 

[symmetal]

Yes, they're the ones Martin. The Baader ones I got are 1.25" mounted and the ZWO ones are 31mm unmounted. I bought the unmounted ones to ensure no vignetting with the ASI1600 but the 1.25" mounted would have been fine actually. I believe I read here reports that the unmounted ones were more prone to reflections, the filter edge not being masked by the holder, so I would get the 1.25" mounted if the extra width is not important. 

In fact now you've made me compare them closely I think I'll have to get a Baader 1.25" Ha for the ZWO filter wheel. I only have the 5 position mini-wheel so use LRGB & Ha. That's another £100 I'll have to spend. Thanks. 

Alan

[MartinFransson]

8 hours ago, symmetal said:

Yes, they're the ones Martin. The Baader ones I got are 1.25" mounted and the ZWO ones are 31mm unmounted. I bought the unmounted ones to ensure no vignetting with the ASI1600 but the 1.25" mounted would have been fine actually. I believe I read here reports that the unmounted ones were more prone to reflections, the filter edge not being masked by the holder, so I would get the 1.25" mounted if the extra width is not important. 

In fact now you've made me compare them closely I think I'll have to get a Baader 1.25" Ha for the ZWO filter wheel. I only have the 5 position mini-wheel so use LRGB & Ha. That's another £100 I'll have to spend. Thanks. 

Alan

Ha ha, always glad to help a fellow astrophotographer spend some money

[Whirlwind]

Just as a question but is there a preferential direction that ZWO filters are meant to set up within the filter wheel?  I think reflections can be made worse if they are the wrong way round.  However I have read that old ZWO filters had halo issues.  According to a user review on cloudynights I saw the newer ones are meant to be better.

[blinky]

Yep, there is an explanation on ZWO’s site and also 365astronomy has it as well - you look for the double reflection by holding a pencil near the front of the filter and this is the outside facing side

[MartinFransson]

11 minutes ago, blinky said:

Yep, there is an explanation on ZWO’s site and also 365astronomy has it as well - you look for the double reflection by holding a pencil near the front of the filter and this is the outside facing side

Will have to check that! 

[wornish]

I was going to say the same as the others check you have the filters the right way around.

I have the ASI1600MM-Pro camera and use the ZWO filters I don't have any reflection issue that I can see.

Also.

How are you mounting the filters ? They need to be as close as possible to the camera sensor .  I have mine in the ZWO EFW7 which is screwed directly on to the camera.

[symmetal]

Reading the Cloudy Nights review the new ZWO narrowband are much improved over the old ones. The old bare filter edges had much edge light leakage causing halos. Only the new OIII still shows some halo/banding. I may get a new ZWO Ha instead of the Baader to keep them all at 31mm. I admit I hadn't checked filter orientation when I put them in. The stretched flat frames are a good indication of leakage. My ZWO Ha flat frame is terrible while the LRGB just show the classic fall off towards the edges. Do the LRGB have an orientation issue or is it just the narrowband?. I had just a quick check of the ZWO/365 Astronomy sites and couldn't find the info blinky mentioned. 

Alan

[symmetal]

6 minutes ago, wornish said:

I have the ASI1600MM-Pro camera and use the ZWO filters I don't have any reflection issue that I can see.

Do you have the 31mm unmounted and are they the new ones with the blackened/beveled edges?

[wornish]

I got them from FLO in June this year as part of the bundle that FLO had on the  ZWO camera + EFW + LRGB and Narrowband filters.  They are the 36mm set maybe thats a difference.

As they  are in my EFW now I can't see the edges sorry.

[MartinFransson]

1 hour ago, symmetal said:

Reading the Cloudy Nights review the new ZWO narrowband are much improved over the old ones. The old bare filter edges had much edge light leakage causing halos. Only the new OIII still shows some halo/banding. I may get a new ZWO Ha instead of the Baader to keep them all at 31mm. I admit I hadn't checked filter orientation when I put them in. The stretched flat frames are a good indication of leakage. My ZWO Ha flat frame is terrible while the LRGB just show the classic fall off towards the edges. Do the LRGB have an orientation issue or is it just the narrowband?. I had just a quick check of the ZWO/365 Astronomy sites and couldn't find the info blinky mentioned. 

Alan

When was the old filters and when was the new? I got mine in July 2017. Don't think they have black edges.

[symmetal]

That's OK Dave. I bought mine as a bundle too before the 1600 Pro version came out so I assume mine are the old ZWO filters. Just had my filterwheel open and the RGB arn't coated to the edges though the Ha appears to be. They all have blacked edges apart from the Red edge which is clear glass. Ha, L and G show the double image with the pencil test so they were mounted correctly, R and B don't have a double image you can see, though one side appears more strongly the anti-colour facing forward so assume that's correct. The bevel edges of the filters arn't blackened which it seems is a feature of the new ones, so I must assume mine are the old ones.

Alan

[symmetal]

1 hour ago, MartinFransson said:

When was the old filters and when was the new? I got mine in July 2017. Don't think they have black edges.

That's the question Martin. It seems they may have had blackened edges but not over the edge bevels for the old filters. (Apart from Red). I bought mine in Sept 2017.

Alan

[symmetal]

Here are my current ZWO flats (Heavily stretched ). The LRGB are very similar.

The Ha indicates a lot of light leakage around the edges.

Alan

 

[MartinFransson]

1 hour ago, symmetal said:

That's the question Martin. It seems they may have had blackened edges but not over the edge bevels for the old filters. (Apart from Red). I bought mine in Sept 2017.

Alan

I checked my filter wheel now and the S2 might have been mounted the wrong way but the O3 was mounted the correct way while giving these reflections. It was also like you said, the edge is black but not the bevel.

The ZWO site says they have a new standard for narrowband filters from 2018, so that would make mine the old version. Kind of annoying. Makes me more want to buy a Baader O3 than another ZWO O3... I´ve heard the Baader ones are good.

[symmetal]

Martin. Here's the Cloudy Nights review comparing the old and new ZWO filters and comparing them to Astrodons. It compares the new ones favourably for the price comparing them as similar performance to Baader, apart from the OIII which still exhibits a slight halo. As I only need an Ha the cheaper new ZWOs could be worth a shot for me, but as you need the OIII this may not be so good for you. It's a pity ZWO didn't offer an upgrade offer for those that bought the old filters that they now admit had failings.

Alan

[MartinFransson]

1 minute ago, symmetal said:

Here's the Cloudy Nights review comparing the old and new ZWO filters and comparing them to Astrodons. It compares the new ones favourably for the price comparing them as similar performance to Baader, apart from the OIII which still exhibits a slight halo. As I only need an Ha the cheaper new ZWOs could be worth a shot for me, but as you need the OIII this may not be so good for you. It's a pity ZWO didn't offer an upgrade offer for those that bought the old filters that they now admit had failings.

Alan

I know! Especially since there were issues with my camera so I couldn´t even use it for the first year. Noticed only now that the filters are no good. Will buy a Baader on pure principle, not throwing more money at ZWO

Then there is the Astronomik version... 6nm... even better?

[MartinFransson]

There. I did it. Just ordered a Baader OIII-filter ?