OIII stacked ... what's going on here?

[souls33k3r]

I've been out in the last few nights trying to gather some much needed OIII data. 

It was somewhat a moonless night meaning the moon was rising quite late and by the time i was done capturing the subs, the moon was then rising from the east.

Now this image has been put through PI for calibration, registration and  SFS but i can't seem to explain what is this hazy/cloudy like structure?

Only used darks as i've always been. The effects seems to be still present even when i run DBE or ABE.

Used a quick STF and histogram to show what's going on. I've also used MaximDL like i've been doing in the past but makes no difference to the end result.

Need some help please.

Thanks in advance.

 

[david_taurus83]

Flats?

[ollypenrice]

Without flats it's hard to know. OIII is not at all moon proof so I'd do a stack with unaffected subs. First step has to be flats but after that there are obvious banding issues which strike me as being on a diagonal orientation in this image. That's very unusual.

Olly

[souls33k3r]

I've never had to do flat before, I mean I know I should but I've always been fine with what came out just by using darks. 

This is the first time something like this has shown, my other two scopes never did that. 

I know OIII is not moon proof but the moon was still not above the horizon so took the opportunity. 

I did notice that the mean readout in SGP was quite high (between 2000 - 3000) which only indicates that maybe high clouds or haze but even if that would the high clouds and haze show up like this? 

Yeah this banding is another thing to worry about. With no potential clear nights, I'm stuck with suggestions right now so anything is muchly appreciated. Just trying to find some probable answers. 

[Andyb90]

Another thing you could check for is dew on the 1600 window/cover glass. I remember reading some posts about it a while back. You just need a night with conditions where dew is likely to form.

[carastro]

Not sure about the mistiness, but is there any chance you were imaging through branches of a tree/shrub in some of the images?

Carole 

[souls33k3r]

9 hours ago, Andyb90 said:

Another thing you could check for is dew on the 1600 window/cover glass. I remember reading some posts about it a while back. You just need a night with conditions where dew is likely to form.

Very valid point, i did however shoot OIII and Ha on the same night (wanted to complete my OIII and then have a few more Ha frames). Checked the last 10 subs from OIII and the first 10 subs from Ha. Only the OIII shows this but not Ha which only leaves me to believe that the issue is with OIII only. See the image below. I've used STF Autostretched Boosted to make it more visible

 

10 hours ago, carastro said:

Not sure about the mistiness, but is there any chance you were imaging through branches of a tree/shrub in some of the images?

Carole 

You really had me thinking there Carole. I could have possibly been imaging a few subs through a tree at some point but to test this what i did was stacked 10 frames from the point the target crossed the meridian and stack them. I know for a fact that the target won't even reach the tree for another 2hrs so this could be a good test. Unfortunately i can see still the mistiness.

Now this weird grid like pattern is also causing the concern. I've tried to change the registration parameters in PI from Auto to "Bcubic B-Spline" and also "Catmul-Rom Spline Filter" but same thing. Went back to MaximDL which has always worked and still the same.

I'm really lost here.

[Oddsocks]

Just a guess, it *might* be an edge diffraction effect with the unmounted filters, it's not uncommon.

You mentioned you hadn't seen it before with your other scopes and it might be that your other scopes had smaller illuminated field so that the light cone was smaller than the filter diameter and maybe your current scope has a larger illuminated field that is straying over the edge of the filter resulting in edge diffraction where the stray light is bent around the edge of the filter and towards the camera.

Some filter manufacturers blacken the filter edges of their unmounted filters with matt black paint to prevent this happening, others don't.

Some filter wheel manufacturers supply filter masks with their unmounted filter carousels and after the unmounted filter is dropped into the wheel recess the mask, like a large washer, is placed over the top before the filter retaining screws are fitted, the mask acts as a shade at the filter edges to prevent edge diffraction.

Finally, interference filters such as these narrow band dichroic's only have a filter etching on one side of the glass substrate while the opposite side has an anti-reflection coating, it's easy to see the difference in thicker filters, and some manufactures apply a mark to the edge of the filter that shows the side that is meant to face the front (aperture) of the telescope. Edge diffraction can be more of a problem if unmounted filters are facing the wrong way.

For your Astronomik's I'm guessing there isn't a mark as the substrate is too thin so you will have to look carefully with a magnifier and try to identify which side of the substrate has the dichroic etching and which is the plain side. Usually the shiniest side is the dichroic etched side and this normally faces out towards the front aperture of the telescope and the duller side with just the anti-reflective coating faces back towards the CCD.

Check that all your filters are mounted with the shiniest, dichroic etched side, facing out towards the sky. If you can't really tell then try reversing just the OIII filter.

The most often reported fix in various imaging fora for curing filter edge diffraction in unmounted filters is to paint around the edges of the unmounted filter with mat black enamel paint, which prevents the over-illuminated light field from being diffracted at the filter edges but just in case you do have a defective filter and you might need to return it for exchange I would make a mask first from opaque material, a piece of cardboard blackened with a felt pen would do. Cut a circular mask from the cardboard who's outside diameter is a few mm wider than the diameter of the filter and who's inside diameter is a few mm smaller than the filter then temporarily fix the mask over the filter with a tape and try imaging again.

If the problem is solved then consider blackening the edges of the filter with mat black enamel, if not, contact the filter manufacturer for advice and possible exchange if found to be faulty.

HTH.

 

[souls33k3r]

1 hour ago, Oddsocks said:

Just a guess, it *might* be an edge diffraction effect with the unmounted filters, it's not uncommon.

You mentioned you hadn't seen it before with your other scopes and it might be that your other scopes had smaller illuminated field so that the light cone was smaller than the filter diameter and maybe your current scope has a larger illuminated field that is straying over the edge of the filter resulting in edge diffraction where the stray light is bent around the edge of the filter and towards the camera.

Some filter manufacturers blacken the filter edges of their unmounted filters with matt black paint to prevent this happening, others don't.

Some filter wheel manufacturers supply filter masks with their unmounted filter carousels and after the unmounted filter is dropped into the wheel recess the mask, like a large washer, is placed over the top before the filter retaining screws are fitted, the mask acts as a shade at the filter edges to prevent edge diffraction.

Finally, interference filters such as these narrow band dichroic's only have a filter etching on one side of the glass substrate while the opposite side has an anti-reflection coating, it's easy to see the difference in thicker filters, and some manufactures apply a mark to the edge of the filter that shows the side that is meant to face the front (aperture) of the telescope. Edge diffraction can be more of a problem if unmounted filters are facing the wrong way.

For your Astronomik's I'm guessing there isn't a mark as the substrate is too thin so you will have to look carefully with a magnifier and try to identify which side of the substrate has the dichroic etching and which is the plain side. Usually the shiniest side is the dichroic etched side and this normally faces out towards the front aperture of the telescope and the duller side with just the anti-reflective coating faces back towards the CCD.

Check that all your filters are mounted with the shiniest, dichroic etched side, facing out towards the sky. If you can't really tell then try reversing just the OIII filter.

The most often reported fix in various imaging fora for curing filter edge diffraction in unmounted filters is to paint around the edges of the unmounted filter with mat black enamel paint, which prevents the over-illuminated light field from being diffracted at the filter edges but just in case you do have a defective filter and you might need to return it for exchange I would make a mask first from opaque material, a piece of cardboard blackened with a felt pen would do. Cut a circular mask from the cardboard who's outside diameter is a few mm wider than the diameter of the filter and who's inside diameter is a few mm smaller than the filter then temporarily fix the mask over the filter with a tape and try imaging again.

If the problem is solved then consider blackening the edges of the filter with mat black enamel, if not, contact the filter manufacturer for advice and possible exchange if found to be faulty.

HTH.

 

Hi Oddsock,

The only issue is, these Astronomik (NB) are not unmounted filters and have all been put in the same way so we're back to square one.

[souls33k3r]

Just thinking, could it be high (thin) clouds that would explain the hazy/misty/cloudy structure?

Could it be LED street light?

[carastro]

It could be thin cloud causing the haziness, but doesn't account for the streaks.

Carole 

[souls33k3r]

Could OIII filter really pick up thin clouds? that would be my first question.

The haziness is unforgivable but the streaks are liveable right now i suppose because i couldn't see them in the combined image so far.

I will try to get flats done and see if these still appear in that.

Also found this article on ZWO forum, worth applying this fix i suppose? But i do worry and wonder, it was never like this before so what caused it? The only thing that changed was a refractor. Coming from a WO Star 71 to SW Esprit 100.

https://bbs.astronomy-imaging-camera.com/viewtopic.php?t=7516&start=10

[carastro]

Quote

Could OIII filter really pick up thin clouds?

Hmm, forgot it was an Oiii filter.  Not sure now, but should definitely reduce visibility.

Carole 

[souls33k3r]

6 minutes ago, carastro said:

Hmm, forgot it was an Oiii filter.  Not sure now, but should definitely reduce visibility.

Carole 

No worries Carole. I was thinking of starting a new thread for this cloud and LED malarkey but then i thought i can keep on adding to this thread to find out the answers.

I really would be interested in knowing from experienced imagers the effect that the OIII filter has with high/thin clouds (5 minute exposures) and also LED lights and would also like to find out if both being true, could this result in the image with clouds like structure and pattern?

[souls33k3r]

Many thanks to all for replying so i thought i should update this thread

Last night I got the chance to spend a few minutes on this. I have the ZWO 8 position EFW and one of the slots is empty so I chose that slot and looked through the scope using flash light and see if I can spot anything on the scope lens or the camera lens but I couldn’t. Next I changed from filter to filter to have my eyes adjusted and then switched to the OIII filter and I couldn’t see anything obvious on the filter.

I then tried to take the flats and on the flats I can see the same patterns (grid and the smudge like feature).

Ha and SII did show the signs of streaks but more obvious on OIII.

Attached is the master flat of OIII. I just hope there's nothing more sinister going on for me to worry about. I won't be taking the camera and FW or even the filters out (will leave in the same orientation) and will reuse these flats and refresh every few months. 

 

[RolandKol]

Do you usually leave the camera outside?

if you do, we had quite a humid period recently...

I would do the test with Un-cooled and Cooled Flats...

I suspect some frozen humidity is causing it.....

In my case it was co-centric, not even close to the pattern like yours... So I hope, my suspections are wrong.

[souls33k3r]

15 minutes ago, RolandKol said:

Do you usually leave the camera outside?

if you do, we had quite a humid period recently...

I would do the test with Un-cooled and Cooled Flats...

I suspect some frozen humidity is causing it.....

In my case it was co-centric, not even close to the pattern like yours... So I hope, my suspections are wrong.

Hi Roland,

No i tear my gear after each session and bring it back in. Leave it out in the room for the entire night and then pack it away in the morning.

I have not tested this with un-cooled flats but only did with the cooled one. Will test this in the next day or two and will come back.

If it's frozen humidity, how can i get rid/avoid it?

[RolandKol]

1 minute ago, souls33k3r said:

Hi Roland,

No i tear my gear after each session and bring it back in. Leave it out in the room for the entire night and then pack it away in the morning.

I have not tested this with un-cooled flats but only did with the cooled one. Will test this in the next day or two and will come back.

If it's frozen humidity, how can i get rid/avoid it?

I was lucky I suppose,

I simply brought it back home, - at 7AM placed near the radiator in peaces (EFW - with filters inside, Reducer, Camera, - all apart as did not want to trap any water inside) ,  - tested my Flats after work at 7PM, and it was enough.

But I as mentioned before, my pattern was completely different, - it was in the central area mainly and spreading out co-centric way, not liner like yours.

Mine was obvious case...

[RolandKol]

P.S.

I actually had it Twice....

The second one happened, once I started SharpCap for Bahtinov focusing Aid while leaving SGP connected to ASI.

I think drivers went mad and camera frosted in 2mins... Completely frosted.... I was ready to bury it....

In this case it was quite warm outside, so I simply switched all of, - had N amount of cigarettes during 30min period, - switched back on and it was OK

 ASI1600 is hard to kill  

-2 lifes  

[souls33k3r]

This is a slight scare for me.

Do you reckon the best thing to do is take the camera off the EFW, and then inspect the AR window / sensor and then also inspect the filters?

Like i said, when i was looking through the scope, the camera sensor/window and filters were quite magnified but i couldn't see anything obvious.

[RolandKol]

To be honest, I was not able to see anything even directly....

In my case it was, probably, a very small amount of frost and was undetectable once brought home into warmth.

Not sure if it is your problem at all. 
In your case, - I would simply do some flats at home. Cool cam to -15C (at home it will not reach -20C probably), -  repeat flats.

If no pattern visible, dry a bit more before next session and forget as a bad nightmare.

If pattern appears while Not cooled, - look for another reason... Flats per each filter, with & without reducer, with & without filters and which ever order is less time consuming to you, - to eliminate any possible part which is Not causing it.

I hope you will Not end up with camera.

[souls33k3r]

1 hour ago, RolandKol said:

To be honest, I was not able to see anything even directly....

In my case it was, probably, a very small amount of frost and was undetectable once brought home into warmth.

Not sure if it is your problem at all. 
In your case, - I would simply do some flats at home. Cool cam to -15C (at home it will not reach -20C probably), -  repeat flats.

If no pattern visible, dry a bit more before next session and forget as a bad nightmare.

If pattern appears while Not cooled, - look for another reason... Flats per each filter, with & without reducer, with & without filters and which ever order is less time consuming to you, - to eliminate any possible part which is Not causing it.

I hope you will Not end up with camera.

Cheers Roland.

So let me take you through the timeline.

A couple of days ago we had this 4 nights clear night stretch. Say Tuesday was the last night, i started to image on Monday night and then finished off my 80th sub on Tuesday night. This pattern was visible on the first and the second night.

I then took the flats last night while being inside my home and the camera was cooled.

I also took the flats from my SII and Ha filters also but didn't pay much attention to it last night.

On closer inspection of the flats taken from last night, the smudge (let's call that) does appear on any of the other NB channels but ever so slightly. The streaks do slightly appear.

So this leads me to believe it's not the filters but something on the camera lens/window or the scope?

SII master flat

Ha master flat

[RolandKol]

If no Reducer was used,

Camera probably,

As it has to be a really large smuggle on the scope to become visible. My 130PDS mirrors are constantly dirty as I am surrounded by trees and nothing is visible on the images or flats.

Lets hope it was just a bit of dew on the outer glass of ASI.

If it's inside.... - ASI .pdf Manual has a section how to clean it!

However, if it is still covered by warranty.... I would keep a manual aside.

[RolandKol]

By the way...

EDGE HD, 

large

from home, 

out,

to 5C...

Dew?

ach... but flats been done inside... but again, from 5c to 23c

[carastro]

Hmmm, not seen anything like this before. 

Let me get my head around this.  Does this streaky pattern appear on your subs, or just when you have stacked? 

What is going on in my mind is, are faulty flats causing this problem.

How do you do your flats?

Scrub that, just re-read the thread, you didn;t use flats.  However you have now produced some flats which are giving the same result.   So there is something wrong in the light train.   

It's probably too late now because you have removed the camera from the scope to examine it, but I am wondering what your image would have been like if you had applied flats at the outset, because this is what flats do, counteract faults in the light train, though what the fault is is difficult to ascertain. 

Carole