Flat acquisition no longer sufficient for broadband only

0.00 Brian Carter ... · view views · Share link
I can't seem to fix this problem, but all my broadband stacks are coming out like this now, flats are no longer fully correcting them. Not a problem with narrowband at all. I have been imaging for over a year, and this just started happening. It has coincided with two other events: 1. New reducer. I bought a 0.65x reducer. It does have a lot more light fall off than my earlier reducers. I'd have thought this could be a problem, but I am ONLY having an issue with broadband. The light fall off and/or vignetting is totally compensated in narrowband. 2. Streetlight: There is a new streetlight pointing towards my scope. It has ruined the entire southern sky, but this artifact is visible no matter what portion of the sky I am aiming at. I've plugged up all the little light gaps I can find in my setup to address leaks Hardware: ES127ED --> EFW 2" --> OAG-L --> Starizona Apex 0.65x --> Pegasus rotator Flats: I have an automated flat panel, use "Dynamic Brightness in NINA". I take new flats immediately after centering/rotating for every target, every night. N=50 flats, with 50% histogram target (I've experimented with a range of 20% to 80%, doesn't seem to matter). Like

0.00

...

I can't seem to fix this problem, but all my broadband stacks are coming out like this now, flats are no longer fully correcting them. Not a problem with narrowband at all.

I have been imaging for over a year, and this just started happening. It has coincided with two other events:

1. New reducer. I bought a 0.65x reducer. It does have a lot more light fall off than my earlier reducers. I'd have thought this could be a problem, but I am ONLY having an issue with broadband. The light fall off and/or vignetting is totally compensated in narrowband.

2. Streetlight: There is a new streetlight pointing towards my scope. It has ruined the entire southern sky, but this artifact is visible no matter what portion of the sky I am aiming at. I've plugged up all the little light gaps I can find in my setup to address leaks

Hardware:
ES127ED --> EFW 2" --> OAG-L --> Starizona Apex 0.65x --> Pegasus rotator

Flats: I have an automated flat panel, use "Dynamic Brightness in NINA". I take new flats immediately after centering/rotating for every target, every night. N=50 flats, with 50% histogram target (I've experimented with a range of 20% to 80%, doesn't seem to matter).

5.72 Álvaro Méndez ... · view views · Share link
Hi Brian, Even though you are exposing your flats correctly, the fact that you’re using a reducer now might be causing your flats to be too short. Try to dim the panel or place a piece of white cloth between it and the scope (or a neutral density sheet) so that you’re reaching the 40-50% ADU in at least 7 seconds. Flats too short don’t calibrate well. Maybe someone can explain the science behind this which I don’t remember since I learnt about it a while ago. This will probably solve your problem. Like

5.72

Álvaro Méndez

...

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Hi Brian,

Even though you are exposing your flats correctly, the fact that you’re using a reducer now might be causing your flats to be too short. Try to dim the panel or place a piece of white cloth between it and the scope (or a neutral density sheet) so that you’re reaching the 40-50% ADU in at least 7 seconds. Flats too short don’t calibrate well. Maybe someone can explain the science behind this which I don’t remember since I learnt about it a while ago.

This will probably solve your problem.

4.52 ScottF ... · view views · Share link
What camera? Like

0.00 Brian Carter Topic starter ... · view views · Share link
What camera? Sorry, meant to mention it: ASI2600MC Like

4.52 ScottF ... · view views · 1 like · Share link
When I see a clearly delineated circle in the centre of the frame like this, I suspect dew issues(2600MC dew heater on?). Just to be cover the bases, I would take flats during the day with all your filters and don't bother cooling the sensor and see if the problems is the same. Does that reducer work with that scope? Broadband and NB will behave differently. Like

9.89 andrea tasselli ... · view views · 4 likes · Share link
Light leak (in one way or another). Given it's a refractor ii might be some subtly shiny portion of the new reducer. And don't take flats during the day. Ever. Take instead a 300s dark and see how really dark it is, comparing to one taken in total darkness. That would tell what type of light leak you have, an actual one or a reflection. As for the intensity, as long as the histogram is away for either ends it doesn't matter. Like

9.89

andrea tasselli

...

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Light leak (in one way or another). Given it's a refractor ii might be some subtly shiny portion of the new reducer. And don't take flats during the day. Ever. Take instead a 300s dark and see how really dark it is, comparing to one taken in total darkness. That would tell what type of light leak you have, an actual one or a reflection. As for the intensity, as long as the histogram is away for either ends it doesn't matter.

0.00 Alberto Lopez ... · view views · Share link
Hi, Hi have same camera. Could this be partly due to vignetting? Same thing happened to me after adding a 0.63x focal reducer (Optec Lepus) The camera's sensor is large, and if the optical train has flares... In my case, with an SCT. See a crude integration picture after DBE. Like

4.01 Leonardo Ruiz ... · view views · 3 likes · Share link
Hi Brian, Don't worry, it's normal. I have two devices: one fixed, which I control with Asi Air, and another remote, which I control with NINA. The problem you're having is overexposure in the green channel. Let me explain: Asi Air assigns the value you program your shots to only the green channel. NINA assigns an average value. To achieve the same effect, you must control the histogram value in the green channel. Start with a value that is half of the value you are looking for. For example, if you are looking for 30,000 ADUs, set the target value to 15,000 and look at the resulting actual histogram. I'll show you the histogram of a shot taken with ASi Air and another with NINA, so you can see that the value that matters is the green channel. Asi Air: In this image, the target value was 35,000 ADUs, and as can be seen, it matches the value in the green channel, with the maximum value of the histogram in the green channel, while the values in the red and blue channels are much lower. The design value, the target value, perfectly matches the obtained value (green). However, in NINA, when creating a flat with a design value of 29,000 ADUs, we see that it assigns this value to the minimum value of the histogram in each chanel but but does not limit the maximum value of the green channel, reaching 40,928 ADUs in green chanel, which destroys your calibration. When you have an overexposed shot, the calibration subtracts more signal than necessary, creating an inverted vignetting effect. This is clearly visible in your images. I have an ASI 2600 MC and an ASI 2600MM, I don't know if the same behavior occurs with other brands and models, but for the AS2600MC, when you work with NINA it is necessary to control the value of the green channel in the histogram and make it match the value you are looking for. Edited ... Like

4.01

Leonardo Ruiz

...

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Hi Brian,
Don't worry, it's normal.
I have two devices: one fixed, which I control with Asi Air, and another remote, which I control with NINA.
The problem you're having is overexposure in the green channel.
Let me explain:

Asi Air assigns the value you program your shots to only the green channel. NINA assigns an average value.

To achieve the same effect, you must control the histogram value in the green channel. Start with a value that is half of the value you are looking for. For example, if you are looking for 30,000 ADUs, set the target value to 15,000 and look at the resulting actual histogram.
I'll show you the histogram of a shot taken with ASi Air and another with NINA, so you can see that the value that matters is the green channel.

Asi Air:
In this image, the target value was 35,000 ADUs, and as can be seen, it matches the value in the green channel, with the maximum value of the histogram in the green channel, while the values in the red and blue channels are much lower. The design value, the target value, perfectly matches the obtained value (green).

However, in NINA, when creating a flat with a design value of 29,000 ADUs, we see that it assigns this value to the minimum value of the histogram in each chanel but but does not limit the maximum value of the green channel, reaching 40,928 ADUs in green chanel, which destroys your calibration.
When you have an overexposed shot, the calibration subtracts more signal than necessary, creating an inverted vignetting effect. This is clearly visible in your images.

I have an ASI 2600 MC and an ASI 2600MM, I don't know if the same behavior occurs with other brands and models, but for the AS2600MC, when you work with NINA it is necessary to control the value of the green channel in the histogram and make it match the value you are looking for.

Edited ...

0.00 blastrophoto ... · view views · 1 like · Share link
Brian, I had the same setup and suffered the same condition with the APEX reducer. Only happened with broadband use, just as you’ve described. I wasted countless night taping off every edge on the scope, taking different flats, trying a bunch of different exposure settings… and nothing worked. It happened on both my ES ED80 and my ES ED127. I believe there’s some kind of reflection happening internally with the reducer or a reflection happening just on the edge of it.. not 100% sure. Either way, the reducer works wonderfully under no moon, with dark skies. Otherwise it’s narrowband only. if you’re looking for a proper reducer for that scope, consider the explore scientific .7x. It’s going to be better suited for the task. hope this helps Like

0.00

blastrophoto

...

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Brian, I had the same setup and suffered the same condition with the APEX reducer. Only happened with broadband use, just as you’ve described. I wasted countless night taping off every edge on the scope, taking different flats, trying a bunch of different exposure settings… and nothing worked. It happened on both my ES ED80 and my ES ED127.

I believe there’s some kind of reflection happening internally with the reducer or a reflection happening just on the edge of it.. not 100% sure. Either way, the reducer works wonderfully under no moon, with dark skies. Otherwise it’s narrowband only.

if you’re looking for a proper reducer for that scope, consider the explore scientific .7x. It’s going to be better suited for the task.

hope this helps

0.00 Brian Carter Topic starter ... · view views · 1 like · Share link
Brian, I had the same setup and suffered the same condition with the APEX reducer. Only happened with broadband use, just as you’ve described. I wasted countless night taping off every edge on the scope, taking different flats, trying a bunch of different exposure settings… and nothing worked. It happened on both my ES ED80 and my ES ED127. I believe there’s some kind of reflection happening internally with the reducer or a reflection happening just on the edge of it.. not 100% sure. Either way, the reducer works wonderfully under no moon, with dark skies. Otherwise it’s narrowband only. if you’re looking for a proper reducer for that scope, consider the explore scientific .7x. It’s going to be better suited for the task. hope this helps Sadly, the ES reducer is my next step if I can't fix this. I also think it might be a reflection, because I've had a couple good broadband experiences with it at a dark site, the images came out beautifully. Thank you Like

0.00

Brian Carter

Topic starter

...

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Brian, I had the same setup and suffered the same condition with the APEX reducer. Only happened with broadband use, just as you’ve described. I wasted countless night taping off every edge on the scope, taking different flats, trying a bunch of different exposure settings… and nothing worked. It happened on both my ES ED80 and my ES ED127.

I believe there’s some kind of reflection happening internally with the reducer or a reflection happening just on the edge of it.. not 100% sure. Either way, the reducer works wonderfully under no moon, with dark skies. Otherwise it’s narrowband only.

if you’re looking for a proper reducer for that scope, consider the explore scientific .7x. It’s going to be better suited for the task.

hope this helps

Sadly, the ES reducer is my next step if I can't fix this. I also think it might be a reflection, because I've had a couple good broadband experiences with it at a dark site, the images came out beautifully.

Thank you

7.22 Oscar ... · view views · Share link
andrea tasselli: And don't take flats during the day. Ever. is this tip only for refractors with reducers, the OP, or does this apply to me too? I have a 2600mm-p and a small petzval. I take my flats in the morning, using the sky. sorry for being paranoid and interrupting the thread, it's my only question here. CS Like

9.89 andrea tasselli ... · view views · 1 like · Share link
Avoid if at all possible, only @ dusk and dawn, not with the Sun up. If using NB filter this doesn't apply (or as much). Like

2.11 Adam Drake ... · view views · Share link
Leonardo Ruiz: Hi Brian, Don't worry, it's normal. I have two devices: one fixed, which I control with Asi Air, and another remote, which I control with NINA. The problem you're having is overexposure in the green channel. Let me explain: Have the NINA devs confirmed this? Like

0.00 Brian Carter Topic starter ... · view views · 1 like · Share link
Adam Drake: Leonardo Ruiz: Hi Brian, Don't worry, it's normal. I have two devices: one fixed, which I control with Asi Air, and another remote, which I control with NINA. The problem you're having is overexposure in the green channel. Let me explain: Have the NINA devs confirmed this? I don't know if this is true about NINA, it definitely isn't the case for my build. I can't replicate the issue with the flats he outlined above. If anything, NINA flat wizard is putting the peak green exactly at the ADU I'm requesting. The blues and reds are a distance away, as expected. Regardless, this didn't fix my problem. The green was already correctly exposed. Edited ... Like

0.00

Brian Carter

Topic starter

...

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Adam Drake:
Leonardo Ruiz:
Hi Brian,
Don't worry, it's normal.
I have two devices: one fixed, which I control with Asi Air, and another remote, which I control with NINA.
The problem you're having is overexposure in the green channel.
Let me explain:

Have the NINA devs confirmed this?

I don't know if this is true about NINA, it definitely isn't the case for my build. I can't replicate the issue with the flats he outlined above. If anything, NINA flat wizard is putting the peak green exactly at the ADU I'm requesting. The blues and reds are a distance away, as expected. Regardless, this didn't fix my problem. The green was already correctly exposed.

Edited ...

0.00 Andrew ... · view views · Share link
Leonardo Ruiz: Hi Brian, Don't worry, it's normal. I have two devices: one fixed, which I control with Asi Air, and another remote, which I control with NINA. The problem you're having is overexposure in the green channel. Let me explain: Asi Air assigns the value you program your shots to only the green channel. NINA assigns an average value. To achieve the same effect, you must control the histogram value in the green channel. Start with a value that is half of the value you are looking for. For example, if you are looking for 30,000 ADUs, set the target value to 15,000 and look at the resulting actual histogram. I'll show you the histogram of a shot taken with ASi Air and another with NINA, so you can see that the value that matters is the green channel. Asi Air: In this image, the target value was 35,000 ADUs, and as can be seen, it matches the value in the green channel, with the maximum value of the histogram in the green channel, while the values in the red and blue channels are much lower. The design value, the target value, perfectly matches the obtained value (green). However, in NINA, when creating a flat with a design value of 29,000 ADUs, we see that it assigns this value to the minimum value of the histogram in each chanel but but does not limit the maximum value of the green channel, reaching 40,928 ADUs in green chanel, which destroys your calibration. When you have an overexposed shot, the calibration subtracts more signal than necessary, creating an inverted vignetting effect. This is clearly visible in your images. I have an ASI 2600 MC and an ASI 2600MM, I don't know if the same behavior occurs with other brands and models, but for the AS2600MC, when you work with NINA it is necessary to control the value of the green channel in the histogram and make it match the value you are looking for. I don’t think any of this is accurate. There’s nothing stopping any channel from going over a “desired ADU ammount” when taking flat frames manually especially with a DSLR and calibration works just fine. besides calibration frames are not even debayered when they are applied to the lights (lights arent debayered either) the flat panel light could be red for all it matters. i suspect there is a light leak I feel for the OP, calibration issues like these makes a person want to put all the equipment up for sale and take up bingo night on Thursday’s. Edited ... Like

0.00

Andrew

...

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Leonardo Ruiz:
Hi Brian,
Don't worry, it's normal.
I have two devices: one fixed, which I control with Asi Air, and another remote, which I control with NINA.
The problem you're having is overexposure in the green channel.
Let me explain:

Asi Air assigns the value you program your shots to only the green channel. NINA assigns an average value.

To achieve the same effect, you must control the histogram value in the green channel. Start with a value that is half of the value you are looking for. For example, if you are looking for 30,000 ADUs, set the target value to 15,000 and look at the resulting actual histogram.
I'll show you the histogram of a shot taken with ASi Air and another with NINA, so you can see that the value that matters is the green channel.

Asi Air:
In this image, the target value was 35,000 ADUs, and as can be seen, it matches the value in the green channel, with the maximum value of the histogram in the green channel, while the values in the red and blue channels are much lower. The design value, the target value, perfectly matches the obtained value (green).

However, in NINA, when creating a flat with a design value of 29,000 ADUs, we see that it assigns this value to the minimum value of the histogram in each chanel but but does not limit the maximum value of the green channel, reaching 40,928 ADUs in green chanel, which destroys your calibration.
When you have an overexposed shot, the calibration subtracts more signal than necessary, creating an inverted vignetting effect. This is clearly visible in your images.

I have an ASI 2600 MC and an ASI 2600MM, I don't know if the same behavior occurs with other brands and models, but for the AS2600MC, when you work with NINA it is necessary to control the value of the green channel in the histogram and make it match the value you are looking for.

I don’t think any of this is accurate.

There’s nothing stopping any channel from going over a “desired ADU ammount” when taking flat frames manually especially with a DSLR and calibration works just fine.

besides calibration frames are not even debayered when they are applied to the lights (lights arent debayered either) the flat panel light could be red for all it matters.

i suspect there is a light leak

I feel for the OP, calibration issues like these makes a person want to put all the equipment up for sale and take up bingo night on Thursday’s.

Edited ...

5.02 Christian Bennich ... · view views · Share link
I agree 100% with @andrea tasselli Not too long ago I went through a very similar situation. It was a light leak as well. I started doing 5 minute exposures in broad daylight under the sun, until I got to a point where those exposures showed absolutely no trace of light from anywhere and could be used as a dark frame. Covering up all the little nooks and crannies of the scope, all the connections and threaded connections etc. etc. After that exercise - my problem went away 🤷‍♂️ Edited ... Like

5.02

Christian Bennich

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I agree 100% with @andrea tasselli

Not too long ago I went through a very similar situation.

It was a light leak as well.

I started doing 5 minute exposures in broad daylight under the sun, until I got to a point where those exposures showed absolutely no trace of light from anywhere and could be used as a dark frame.

Covering up all the little nooks and crannies of the scope, all the connections and threaded connections etc. etc.

After that exercise - my problem went away 🤷‍♂️

Edited ...

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Flat acquisition no longer sufficient for broadband only [Deep Sky] Acquisition techniques · Brian Carter · ... · 15 · 374 · 8

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