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Issue with Optolong L-Extrem filter, help !

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#1 Phil49

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Posted 22 September 2021 - 01:50 AM

Hi all,

 

We're next to the end of summer, I was taking advantage of the bad weather here in France and I had decided to change my flat bank for my refractor, a TS 76 EDPH fitted with a Zwo OAG and my cameras (ASI 294 MC Pro for imaging and ASI 290 MM for autoguidng).

 

My_refractor.jpg

 

I wanted to do it with my 1,25" filter screwed just in front of my Zwo ASI 294 MC Pro camera with the Zwo adapter.

 

I was confident, I shot a good 30 flats at 2 sec, gain 190, then 0 to find out if there was a difference, but when I started to open them up in Siril, I was a bit surprised and puzzled !

 

Siril_green_layer.jpg

 

I tried to see if I had a problem with my filter I had cleaned with Purosol and a scientific wipes dedicated to this use, bu no, Optolong advise to do so with isopropylic alcohol.

 

I had taken the week before a few photos of IC 1805 to carry out some tests for something else and was also surprised to find out this :

 

Image_IC1848.jpg

 

Of course, I don't speak about the amp glow which is properly taken into account and corrected by Siril or any other image processing software, but I'm talking about this green band on the right hand side !

 

I tried to look for a light "leak" in my optical train but except a very small slack (see red arrows) that I solved screwing the brass screw, I didn't notice any difference in the result ! :-(

 

TS 76 EDPH optical train.jpg

 

Now, whatever I do, I even get a new pattern on my flats :

 

Arc_circle.jpg

 

I don't know what this arc cicle is..

 

Some people told me that all those pattern don't matter as the software will only take care of dusts and some other defaults to correct.

 

Yet, what I don't understand is why I get a more "usual" pattern with a Zwo narrow band filter, also a 1.25" filter screwed before the camera and not with this Optolong L extrem filter ?

 

I'm looking forward shooting again to see if this green band is still present or not...

 

Any idea !?

 

Thanks a lot for your help 

 

Phil


Edited by Phil49, 22 September 2021 - 12:12 PM.


#2 Tapio

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Posted 22 September 2021 - 03:13 AM

That looks like a reflection - maybe the filter, maybe something else.



#3 stnagy

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Posted 22 September 2021 - 06:21 AM

I'm not sure if this is your problem, but make sure your OAG isn't protruding into the optical path. The prism needs to be arranged above the long side of the sensing chip. If it's not, it can extend over the chip a bit and cause reflections.

Edit: you might also check whether the filter is seated correctly. If it's at a slight angle, it can cause reflections and discoloration. It might be worth testing your set up with someone else's L-Extreme if you can find one. That way you could check if it's your particular filter or a problem with something else.

Edited by stnagy, 22 September 2021 - 06:30 AM.


#4 IonClad

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Posted 22 September 2021 - 07:43 AM

There appear to be several effects happening at once here. The reddish haze that circles the sensor edges is likely from the combination of the 294 sensor and the narrowband filter. If you search for this effect you'll find several threads describing it. I'm not sure if it applies to all narrowband filters or only this particular one.

 

The green edge and arcs within the frame are likely due to a reflection off components like the inner telescope barrel or spacers. If you remove the camera and point the telescope at a uniform source such as a white monitor you can look down the barrel and try to see where the strongest reflections occur. These can be mitigated by using components with a wider diameter or by flocking. I needed to flock several spacers to remove a similar effect from my setup.



#5 Phil49

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Posted 22 September 2021 - 11:54 AM

That looks like a reflection - maybe the filter, maybe something else.

Hello Tapio, yes, but what ?

 

I'm not sure if this is your problem, but make sure your OAG isn't protruding into the optical path. The prism needs to be arranged above the long side of the sensing chip. If it's not, it can extend over the chip a bit and cause reflections.

Edit: you might also check whether the filter is seated correctly. If it's at a slight angle, it can cause reflections and discoloration. It might be worth testing your set up with someone else's L-Extreme if you can find one. That way you could check if it's your particular filter or a problem with something else.

 

Hello stnagy

 

Someone on a french forum told me the same thing.

 

I did a test, I simply pulled the main part where the prism seats out of view of the lens, I shot some flats and I had the same problem, the same bright side on the flat on two corners as you can see on the last photo in my previous email !

 

This is the position that corrresponds to the green band on my light of IC 1848 !

 

Can in internal reflection generate such a brightness one one side of the frame !?

 

With a flat I can understand, with the led from my flat box or drawing pad, but with a nebulae and the dark  background and the night, what is generating such a brightness !?? 

 

 

I'm not sure if this is your problem, but make sure your OAG isn't protruding into the optical path. The prism needs to be arranged above the long side of the sensing chip. If it's not, it can extend over the chip a bit and cause reflections.

Edit: you might also check whether the filter is seated correctly. If it's at a slight angle, it can cause reflections and discoloration. It might be worth testing your set up with someone else's L-Extreme if you can find one. That way you could check if it's your particular filter or a problem with something else.

I unscrewed and screwed again I dont know how many times the adapter, and in my opinion, you cannot wrongly screw the filter on the Zwo adapter and in the dedicated  location in front of the camera !

I even tried both sides in case of, but it made no difference...

 

 

I'm not sure if this is your problem, but make sure your OAG isn't protruding into the optical path. The prism needs to be arranged above the long side of the sensing chip. If it's not, it can extend over the chip a bit and cause reflections.

Edit: you might also check whether the filter is seated correctly. If it's at a slight angle, it can cause reflections and discoloration. It might be worth testing your set up with someone else's L-Extreme if you can find one. That way you could check if it's your particular filter or a problem with something else.

I see no other test alas to do, and I'll ask to some friends if they have this filter.

 

Oh by way, among all the other tests carried out, I shot flats with just the first 10 mm extension ring where the filter is screwed in, then with the 21 mm one added to it, then with the OAG added to both extensions, and for all those tests I had a regular pattern, that is 4 corners vignetting and no reflection !

 

As soon as I screw back the optical train on my TS 76 EDPH, I get all those strange patterns and this bright side !

 

Tonight I may have the opportunity to shoot again a few photos, I won't take a lot of them as this is alsmot full moon, but will try and find out if I still have this bright side on my brute !

 

 

There appear to be several effects happening at once here. The reddish haze that circles the sensor edges is likely from the combination of the 294 sensor and the narrowband filter. If you search for this effect you'll find several threads describing it. I'm not sure if it applies to all narrowband filters or only this particular one.

 

The green edge and arcs within the frame are likely due to a reflection off components like the inner telescope barrel or spacers. If you remove the camera and point the telescope at a uniform source such as a white monitor you can look down the barrel and try to see where the strongest reflections occur. These can be mitigated by using components with a wider diameter or by flocking. I needed to flock several spacers to remove a similar effect from my setup.

 

Hello ,Ironclad,

 

Indeed I've taken a look at the inside, but didn't notice where it could happen...

 

Everything is almost black inside !

 

I have the feeling that it's closer to the OAG than on the opposite way, but not quite sure...

 

I'm really surprised to notice that very few people faced this issue !

 

Philippe




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