First Mono image the soul nebula with new version and now Flats help

[Danjc]

Apologies for not doing this earlier but here you go @david_taurus83 

MasterFlat.tifSingle Flat.fit

[david_taurus83]

They are the correct exposure so no issues there. They are clearly causing you issues though as they have a ring type artifact around them. Any ideas what could have caused this?

[Danjc]

10 hours ago, Danjc said:

I don’t think the technique and old iPad I’m using help thinking about it. I noticed when taking the flats that when I rested the iPad on top of the ED80’s dew shield that the iPad had pressure spots in an around the places where the iPad touched the dew shield. As well as that I probably should place a piece of thin white A4 paper in there to as the screens are of a glossy/reflective nature. 

Maybe this as the iPad screen rests directly on the metal dew shield of the scope ?

[Adam J]

23 minutes ago, david_taurus83 said:

They are the correct exposure so no issues there. They are clearly causing you issues though as they have a ring type artifact around them. Any ideas what could have caused this?

That is an odd looking flat for sure.

[Danjc]

I had a play with taking flats and set the target ADU in APT's flats aid to 7500 which is half the full well of the camera. I also placed a piece of thin white paper next to the ipad screen.

Im still not sure the flat looks ok and then I tried the same with a CLS CCD uv/ir cut filter (in the efw) I seemed to get a more uniform flat.

If I rotate the camera a little in the efw the bright spot moves so I'm flummoxed at the moment.

Help and feedback really appreciated. 

F_HA7Nm_2019-09-02_13-44-44_Bin2x2_1.67969s__-10C.fit

 

 

F_HA7Nm_2019-09-02_13-53-30_Bin2x2_1.67969s__-10C 90 turn.fit

With asi rotated 90 degrees 

 

 

 

F_LUMINANCE_2019-09-02_13-49-07_Bin2x2_0.10165s__-10C.fit

 

 

[ollypenrice]

I think we can see clearly that pressure on the screen was causing the initial problem. That large dark ring seems to me to confirm this.

I still don't entirely like the look of the new flats though. You'd really expect, after a basic stretch, to see fairly symmetrical darker corners with a lighter middle plus any dust bunnies if there are any.

If the bright spot moves when you move the camera it is absolutely vital not to rotate the camera at all between lights and flats. 

We are not trying to make even-looking flats, we are trying to make flats which precisely replicate the uneven illumination of the system. Below is a perfect flat, 'perfect' because it perfectly corrected the illumination of the rig in question, a Tak FSQ106 and full frame CCD. As you can see, the light fall-off in the corners is huge (about 23%) though the stretch makes it look far more than 23%. For all that, this was one of the flats that we used in our 400 hour 35 panel mosaic of Orion - and mosaics require images to be accurately flattened or the joints will show. When I do flats now in this rig I want them to look something like this. The bunnies will change but the dark corners and brighter, symmetrical centre make it look instantly credible.

Olly

[Danjc]

4 hours ago, ollypenrice said:

I think we can see clearly that pressure on the screen was causing the initial problem. That large dark ring seems to me to confirm this.

I still don't entirely like the look of the new flats though. You'd really expect, after a basic stretch, to see fairly symmetrical darker corners with a lighter middle plus any dust bunnies if there are any.

If the bright spot moves when you move the camera it is absolutely vital not to rotate the camera at all between lights and flats. 

We are not trying to make even-looking flats, we are trying to make flats which precisely replicate the uneven illumination of the system. Below is a perfect flat, 'perfect' because it perfectly corrected the illumination of the rig in question, a Tak FSQ106 and full frame CCD. As you can see, the light fall-off in the corners is huge (about 23%) though the stretch makes it look far more than 23%. For all that, this was one of the flats that we used in our 400 hour 35 panel mosaic of Orion - and mosaics require images to be accurately flattened or the joints will show. When I do flats now in this rig I want them to look something like this. The bunnies will change but the dark corners and brighter, symmetrical centre make it look instantly credible.

Olly

I’m a bit stuck tbf?

[ollypenrice]

4 minutes ago, Danjc said:

I’m a bit stuck tbf?

I think your problem may just be your light source. It needs to be even, have the right spectrum and require the right exposure time.

Olly

[Adam J]

1 minute ago, ollypenrice said:

I think your problem may just be your light source. It needs to be even, have the right spectrum and require the right exposure time.

Olly

I agree, I have never had a good time getting a flat from a LCD screen. You need a proper flat panel.

[Danjc]

5 hours ago, ollypenrice said:

I think your problem may just be your light source. It needs to be even, have the right spectrum and require the right exposure time.

Olly

 

5 hours ago, Adam J said:

I agree, I have never had a good time getting a flat from a LCD screen. You need a proper flat panel.

Thanks, I will look into getting a decent flat panel. 

[tooth_dr]

6 hours ago, Danjc said:

 

Thanks, I will look into getting a decent flat panel. 

 

I have shot flats on my iPad resting on the dew shield and currently am using a computer monitor. I’m not aware of any issues in my flats. They looks exactly like Ollys.

Is the iPad display definitely not changing when sitting on the dew shield? I needed to set up guided access to prevent the white display from changing when I used mine.

Also I had a ring like that on an image recently when I was shooting too early in the evening, too much like getting in and reflecting perhaps? Or getting in somewhere else.

[ollypenrice]

1 hour ago, tooth_dr said:

 

I have shot flats on my iPad resting on the dew shield and currently am using a computer monitor. I’m not aware of any issues in my flats. They looks exactly like Ollys.

Is the iPad display definitely not changing when sitting on the dew shield? I needed to set up guided access to prevent the white display from changing when I used mine.

Also I had a ring like that on an image recently when I was shooting too early in the evening, too much like getting in and reflecting perhaps? Or getting in somewhere else.

I think the screen should not be used as a means of support.

Olly

[Adam J]

3 hours ago, tooth_dr said:

 

I have shot flats on my iPad resting on the dew shield and currently am using a computer monitor. I’m not aware of any issues in my flats. They looks exactly like Ollys.

Is the iPad display definitely not changing when sitting on the dew shield? I needed to set up guided access to prevent the white display from changing when I used mine.

Also I had a ring like that on an image recently when I was shooting too early in the evening, too much like getting in and reflecting perhaps? Or getting in somewhere else.

I think it depends on the quality of the display some are more homogeneous than others. Also how you mount it against the scope as pressure on the screen changes its brightness locally. 

Edited September 3, 2019 by Adam J

[Danjc]

Just a quick test this morning without the iPad and using a white t-shirt with the scope pointing out the garage door (not ideal I know) with the same settings as previously used.

[Danjc]

3 hours ago, tooth_dr said:

 

I have shot flats on my iPad resting on the dew shield and currently am using a computer monitor. I’m not aware of any issues in my flats. They looks exactly like Ollys.

Is the iPad display definitely not changing when sitting on the dew shield? I needed to set up guided access to prevent the white display from changing when I used mine.

Also I had a ring like that on an image recently when I was shooting too early in the evening, too much like getting in and reflecting perhaps? Or getting in somewhere else.

No the screen definitely doesn’t change but it is a very old iPad. 

Tomorrow morning when I get in from work I am going to try the same but with my CLS-CCD filter to see what I get. 

[david_taurus83]

Looks like some sort of internal reflection. Do all the filters produce this with flats?

[tooth_dr]

1 hour ago, david_taurus83 said:

Looks like some sort of internal reflection. Do all the filters produce this with flats?

Light getting in around the camera or filter wheel?

[Danjc]

7 hours ago, david_taurus83 said:

Looks like some sort of internal reflection. Do all the filters produce this with flats?

I will try the CLS-CCD I have in the wheel tomorrow. 

5 hours ago, tooth_dr said:

Light getting in around the camera or filter wheel?

This has also crossed my mind and although I did cover the camera and wheel to a degree I could have probably done a better job of it. I will be sure to absolutely cover all next time to rule this out   

If my other filter shows the same signs of odd light then I guess it’s probably light leak of some sort. 

If the other filter is all good then could it possibly be something to do with the Ha filter ?

[Danjc]

More test images and both taken in my dark garage with the asi,efw and all the back of the scope coverd up with just a white wall lit up for purpose of the flats.

Both images taken with a CLS CCD UV/IR cut 1.25" filter in the efw.

I then decided to inspect the Ha filter and found this on it ( images on the next post as they are on my phone) and when I slightly rotate the camera the bright spot in the Ha image moves... could this be the problem ????

 

Target ADU 7500 as before

 

 

Target ADU 20000

Edited September 4, 2019 by Danjc

[Danjc]

[kirkster501]

My Ha flats sometimes have that "frame" look as well.....

You absolutely must not move the camera even a fraction between lights and flats or else the dust bunnies and vignetting will not calibrate out properly and you will end up with strange artefacts on the stacked master.

If you use autofocus, a slight difference in focus (within reason) will not make that much difference between lights and flats acquisition, nor will temperature of the camera.  For instance, if the light was taken at focus position 17123 and at -10C, it makes little difference if your flats were at focus 16900 and temperature 10C.

 

[david_taurus83]

What is that protrusion? Might be the issue.

 

[Danjc]

4 hours ago, david_taurus83 said:

What is that protrusion

I take it you mean this 

 

I haven’t got a clue what it may be David, I certainly don’t want to try and clean it. I have tried to capture it from different angles in my previous pics. 

I wonder if it’s worth contacting FLO ?

 

[david_taurus83]

Yes, is that actually in the filter cell?

[Adam J]

5 hours ago, Danjc said:

I take it you mean this 

 

I haven’t got a clue what it may be David, I certainly don’t want to try and clean it. I have tried to capture it from different angles in my previous pics. 

I wonder if it’s worth contacting FLO ?

 

Need to see a picture from the other side of the filter.