Just bought my first monochrome camera, help me understand some things!

[RolandKol]

I just checked the files you shared...

Are you using multiple / stacked Calibration subs? or just single? Asking, as you shared only one file per calibration...

they should be stacked... The larger amount the better...

Furthermore, file names of flats tell, you take them incorrectly.... 2022-10-27_10-31-30_O_-10.00_0.03s_0000.xisf

0.03sec is way too fast sub for Flats, you should target above 0.33sec, closer to 1 sec (can be even 5sec for H), - stack minimum 25 of them.

Almost all software now have automated flats procedures (for Example NINA or SGP), the only thing you have to look after, - amount of light coming in, to have longer subs as described.

 

[Gumminess8083]

38 minutes ago, RolandKol said:

I just checked the files you shared...

Are you using multiple / stacked Calibration subs? or just single? Asking, as you shared only one file per calibration...

they should be stacked... The larger amount the better...

Furthermore, file names of flats tell, you take them incorrectly.... 2022-10-27_10-31-30_O_-10.00_0.03s_0000.xisf

0.03sec is way too fast sub for Flats, you should target above 0.33sec, closer to 1 sec (can be even 5sec for H), - stack minimum 25 of them.

Almost all software now have automated flats procedures (for Example NINA or SGP), the only thing you have to look after, - amount of light coming in, to have longer subs as described.

 

I do use multiple stacked subs, usually I take 50 calibration frames per type (you can find a folder with the stacked masters at the same link). I only shared one per type since I am running out of space on my GDrive...

As for the flat frames duration, I was taking sky subs and had a hard time taking them, as the sky was too bright. I did try retaking them today indoors using a tablet, but the patterns were still present (and the light was too dim, so I had a hard time getting any flat frame with an exposure time below 30 seconds at 200 gain).

Since I've tried everything, I might as well redo the whole procedure using a new set of flats with a longer exposure time. I have moved the optical train, so they won't account for any tilt or dust bunny, but they'll at least fix the artifacts, hopefully...

I'll also try stacking some uncalibrated light subs, just to see what comes of it.


Update: I tried stacking some uncalibrated lights, and the patterns seems to be showing there as well, so the problem may really lie with my underexposed flats... I'll try taking some more and run some tests

Edited November 2, 2022 by Gumminess8083

[scotty38]

Are you sure they're all using the same offset?

[Gumminess8083]

19 minutes ago, scotty38 said:

Are you sure they're all using the same offset?

If you mean camera offset, then yes, 200 gain and 2 offset (although I read somewhere that it's not necessary for flat frames to have the exact same gain and offset as the lights). If you mean filter focus offset, then I haven't bothered too much with that, since the filters are supposed to be parafocal.

Edited November 2, 2022 by Gumminess8083

[Gumminess8083]

2 hours ago, Gumminess8083 said:

I do use multiple stacked subs, usually I take 50 calibration frames per type (you can find a folder with the stacked masters at the same link). I only shared one per type since I am running out of space on my GDrive...

As for the flat frames duration, I was taking sky subs and had a hard time taking them, as the sky was too bright. I did try retaking them today indoors using a tablet, but the patterns were still present (and the light was too dim, so I had a hard time getting any flat frame with an exposure time below 30 seconds at 200 gain).

Since I've tried everything, I might as well redo the whole procedure using a new set of flats with a longer exposure time. I have moved the optical train, so they won't account for any tilt or dust bunny, but they'll at least fix the artifacts, hopefully...

I'll also try stacking some uncalibrated light subs, just to see what comes of it.


Update: I tried stacking some uncalibrated lights, and the patterns seems to be showing there as well, so the problem may really lie with my underexposed flats... I'll try taking some more and run some tests.

Update 2: I tried taking some new flats using the flat wizard and my tablet. S at 3.87 seconds, H at 10.46 seconds, and O at 5.87 seconds. I'll try stacking them tomorrow after work and see what comes of it.

(Not sure why this update was posted as a separate comment instead of an edit, but oh well...)

Edited November 2, 2022 by Gumminess8083

[scotty38]

18 minutes ago, Gumminess8083 said:

If you mean camera offset, then yes, 200 gain and 2 offset (although I read somewhere that it's not necessary for flat frames to have the exact same gain and offset as the lights). If you mean filter focus offset, then I haven't bothered too much with that, since the filters are supposed to be parafocal.

Yes I did mean camera offset so if they're the same that's fine. I looked at the headers and it seems that different drivers were used as the offset only shows up on the lights. I recall this from the NINA native versus ascom drivers when I had my 294mc and it bit me as the defaults for offset were different. 

EDIT - I'd like to read where you saw offset didn't matter being different as that's a new one on me and from what I've seen it very much matters.

Edited November 2, 2022 by scotty38

[barbulo]

10 hours ago, Gumminess8083 said:

and the light was too dim, so I had a hard time getting any flat frame with an exposure time below 30 seconds at 200 gain

My flats with the Ha fliter are around 35s at 120 gain and 30offset, and calibrate quite well. The shortest I take are with the luminance filter, around 5s.

[geeklee]

13 hours ago, Gumminess8083 said:

Unfortunately, it seems like this doesn't hold true for my flats...

EDIT: I've had a look at the files and compared to my own.

Two observations:

• The Master Flat is underexposed. It looks fine but typically aim to get the histogram further to the right.
• I think the Master Dark and Dark Flats could be causing the issue.  As I mentioned below, did you mean offset "2" when you typed that above?  

I looked out a 90s Master Dark I had.  Gain 120 and Offset 30.  So the defaults.  I had a play with calibration and got a result on your Ha with no discernible pattern (except the amp glow where we mismatched more clearly).  The pattern would have been there with a strong enough stretch as our calibration frames mismatched but the point was it wasn't overcorrecting massively. Perhaps your lights were offset 30 or higher than 2 anyway.

Lee

Edited November 3, 2022 by geeklee

[geeklee]

9 hours ago, Gumminess8083 said:

2 offset (although I read somewhere that it's not necessary for flat frames to have the exact same gain and offset as the lights)

Why wouldn't you aim to match gain and offset on all your calibration frames, it'll just make life much simpler and with less variables.

Is "2" offset a typo?  Seems very low. 

Edited November 3, 2022 by geeklee

[Gumminess8083]

13 hours ago, scotty38 said:

Yes I did mean camera offset so if they're the same that's fine. I looked at the headers and it seems that different drivers were used as the offset only shows up on the lights. I recall this from the NINA native versus ascom drivers when I had my 294mc and it bit me as the defaults for offset were different. 

EDIT - I'd like to read where you saw offset didn't matter being different as that's a new one on me and from what I've seen it very much matters.

Huh, this is strange. I thought I took them both with the same driver, but oh well. I tried opening them in pixinsight but the offset value for the lights is not using the same unit of measure as NINA, so I'm cannot confirm that it's 2, but it should be.

 

As for the other question, I'm not really sure where I read that, but it was a post going around the internet. Since my gain was so high, I was looking into whether I could take my lights and flats at a different gain and offset value to be able to get my RGB flats decently, as my sky flats were too bright.

For the new ones I will use tonight, I made sure to use the same exact settings as my lights, but I'll reconfirm it later when I get home.

[RolandKol]

2 minutes ago, Gumminess8083 said:

Huh, this is strange. I thought I took them both with the same driver, but oh well. I tried opening them in pixinsight but the offset value for the lights is not using the same unit of measure as NINA, so I'm cannot confirm that it's 2, but it should be.

 

As for the other question, I'm not really sure where I read that, but it was a post going around the internet. Since my gain was so high, I was looking into whether I could take my lights and flats at a different gain and offset value to be able to get my RGB flats decently, as my sky flats were too bright.

For the new ones I will use tonight, I made sure to use the same exact settings as my lights, but I'll reconfirm it later when I get home.

Not sure about your cam, but once you connect ZWO to NINA, you have 2 options, to use ZWO native drivers or ASCOM ones, - they may behave a bit different, I have not tested.

[Gumminess8083]

4 hours ago, geeklee said:

EDIT: I've had a look at the files and compared to my own.

Two observations:

• The Master Flat is underexposed. It looks fine but typically aim to get the histogram further to the right.
• I think the Master Dark and Dark Flats could be causing the issue.  As I mentioned below, did you mean offset "2" when you typed that above?  

I looked out a 90s Master Dark I had.  Gain 120 and Offset 30.  So the defaults.  I had a play with calibration and got a result on your Ha with no discernible pattern (except the amp glow where we mismatched more clearly).  The pattern would have been there with a strong enough stretch as our calibration frames mismatched but the point was it wasn't overcorrecting massively. Perhaps your lights were offset 30 or higher than 2 anyway.

Lee

I'll answer the question regarding offset first:

If you see my first comments on this thread, pluse the first piint of Vlaiv's reply, you can see why my offset is so low.

Keeping gain at 200 and offset at 2 allows me to have the minimum pixel value slightly above 0 when integrating some bias frames.

 

As for the flats, I'm not really sure how they could be underexposed, as I took them with NINA's flat wizard and made sure to keep the histogram at 50%.

 

As I mentioned previously, I'll try retaking ALL the calibration subs tonight and see if I can get everything to work. Maybe I changed some value by mistake without realizing...

I tried checking in pixinsight but, while it looks like I can see the gain value clearly for my lights (it's 200), the offset value is not using the same unit of measure as NINA, so I have no clue what the value presented to me by pixinsight corresponds to in NINA...

 

[Gumminess8083]

4 minutes ago, RolandKol said:

Not sure about your cam, but once you connect ZWO to NINA, you have 2 options, to use ZWO native drivers or ASCOM ones, - they may behave a bit different, I have not tested.

I did initially use the ZWO driver, but later switched to the Ascom one since I was having troubles with PHD picking my main cam as a guide.

As far as I know, though, I should have used the ascom driver for both lights and flats in this imaging session (not sure about the darks, but I am sure that those had the right settings).

[scotty38]

14 minutes ago, Gumminess8083 said:

I did initially use the ZWO driver, but later switched to the Ascom one since I was having troubles with PHD picking my main cam as a guide.

As far as I know, though, I should have used the ascom driver for both lights and flats in this imaging session (not sure about the darks, but I am sure that those had the right settings).

This is what I was trying to say about the driver differences. Swapping between these two won't necessarily keep the same offset settings and also explains why you can see the offset in the fits header of one but not the other. I know this because I've done exactly the same.

In the native driver NINA shows you the offset and you can change it there and then but with the ASCOM driver you can only see it and change it in the driver itself which you can do by clicking on the "gears" icon before connecting the camera.

I also think one of them defaults to 8 and the other defaults to 30. If you changd one of them to 2 then the other may have been 8 or 30 depending which you changed.......

Edited November 3, 2022 by scotty38

[RolandKol]

I have just compared my .fits Headers and found out strange thing,

my NINA and SGP do record resolution values into Headers, yours not.... 
Also, cannot know if it makes any difference, but worth checking NINA connection section, just in case...

P.S. my header from NINA

Edited November 3, 2022 by RolandKol

[scotty38]

2 minutes ago, RolandKol said:

I have just compared my .fits Headers and found out strange thing,

my NINA and SGP do record resolution values into Headers, yours not.... 
Also, cannot know it makes any difference, but worth checking NINA connection section, just in case...

P.S. my header from NINA

As I am saying that's the difference between the native and ascom driver.

[RolandKol]

15 minutes ago, scotty38 said:

This is what I was trying to say about the driver differences. Swapping between these two won't necessarily keep the same offset settings and also explains why you can see the offset in the fits header of one but not the other. I know this because I've done exactly the same.

In the native driver NINA shows you the offset and you can change it there and then but with the ASCOM driver you can only see it and change it in the driver itself which you can do by clicking on the "gears" icon before connecting the camera.

I also think one of them defaults to 8 and the other defaults to 30. If you changd one of them to 2 then the other may have been 8 or 30 depending which you changed.......

Just in case, 

once you will set up all and working, make your Windows System Image BackUp...
Saved lots of headache for me few times 

[Gumminess8083]

44 minutes ago, scotty38 said:

This is what I was trying to say about the driver differences. Swapping between these two won't necessarily keep the same offset settings and also explains why you can see the offset in the fits header of one but not the other. I know this because I've done exactly the same.

In the native driver NINA shows you the offset and you can change it there and then but with the ASCOM driver you can only see it and change it in the driver itself which you can do by clicking on the "gears" icon before connecting the camera.

I also think one of them defaults to 8 and the other defaults to 30. If you changd one of them to 2 then the other may have been 8 or 30 depending which you changed.......

I know what you mean!

 

What I was trying to say as well is that I did check those options and made sure they were correct (by clicking on the gear), but I changed the cables around, which may have reset them to default (although I cannot be sure).

 

While in the NINA app you can directly change the gain even with the Ascom driver, you are forced to use the cog to change the offset, so I am thinking that maybe I did actually shoot at 200 gain and default offset (I believe it was 30 as well).

 

Since I have plenty of things to try out, I'll test this as well tonight and see if it makes any difference.

 

Edit: Actually, I have the stats plugin installed, so I should have a json file with all the info pertaining to each shot I took!

Edited November 3, 2022 by Gumminess8083

[Gumminess8083]

@scotty38 @RolandKol @geeklee

I have proceeded, under the assumption that I have mistakenly taken all my lights at 30 offset instead of 2, proceeded to redo the whole thing. I shot all of my darks, flats, and dark flats with 200 gain and 30 offset, just to test whether the theory held any value.

You can see the results for yourselves in here: https://drive.google.com/drive/folders/1YliX_I4YkaKUSjJqnf061Lj7rF7Xnq1W?usp=sharing

I hastily made this combination just to see the results:

 

As you can see, while the problem seems to be mitigated, you can see that the patterns are still clearly visible in the background, although less, when compared to the previous results.

I'm not really sure what is going on, but I guess I'll just have to put the data aside for now and wait for another clear night to run some more tests. The weather forecast changed and it now says that it's going to be clear this coming Saturday, so I'll leave my scope out and shoot the same target (making sure that all my settings are correct this time), just to compare the final results.

(Not yet 100% sure on this, as I'd first like to run some tests on whether or not my camera has sensor tilt)

[RolandKol]

I just took files per each channel from here: https://drive.google.com/drive/folders/1AZtDxo0IwnWAfZ3qtgIYMeSoKr3835ou

all looks more or less OK for me.

The image below, is a 1minute stretch:  slightly cropped, background extrracted and a bit of color adjustment + SCNR (no sharpening or noise reduction)

 

Edited November 4, 2022 by RolandKol

[RolandKol]

10 hours ago, Gumminess8083 said:

(Not yet 100% sure on this, as I'd first like to run some tests on whether or not my camera has sensor tilt)

My suggestion would be, - do Not touch the camera tilt adjustment, check your focuser and all connectors you use first or "eyepiece clamp" you use in the focuser, - this may introduce slight tilt, especially once you place so many "mono toys" to hold.

RedCat looks like have quite solid focuser, so maybe you have not clamped it properly or any addaptor or even EFW introduced it. Disasable the optical train and assemble all back first, - double check.

In other words, check all other possible points of failure before adjusting the tilt of the camera.

And, to be honest, your FOV is large, so stars are quite small and the tilt is barely visible, - I would suggest to ignore it unless it goes out of control.

[Gumminess8083]

10 hours ago, RolandKol said:

My suggestion would be, - do Not touch the camera tilt adjustment, check your focuser and all connectors you use first or "eyepiece clamp" you use in the focuser, - this may introduce slight tilt, especially once you place so many "mono toys" to hold.

RedCat looks like have quite solid focuser, so maybe you have not clamped it properly or any addaptor or even EFW introduced it. Disasable the optical train and assemble all back first, - double check.

In other words, check all other possible points of failure before adjusting the tilt of the camera.

And, to be honest, your FOV is large, so stars are quite small and the tilt is barely visible, - I would suggest to ignore it unless it goes out of control.

I have made another post on here showing some examples of what I assume to be tilt. I have tried taking everything apart and putting it back together, so I'm gonna shoot some exposures to see whether or not that has solved it, otherwise I'm going to try and move one piece at a time to see whether anything changes and make sure that it is actually tilt.

No luck today. It's currently 21 and the sky is super cloudy

[Adam J]

On 02/11/2022 at 14:11, Gumminess8083 said:

Hello Adam, sorry to resurrect this old thread!

I finally got around to imaging some targets and I am indeed suffering from some of the problems you mentioned regarding the flat frames (similar to those mentioned in the linked thread).

I tried taking them under various conditions (sky flats, phone screen, laptop screen, tablet, ...) with various gain and offset settings, but they alway come out looking weird (not all filters present the same patterns. For example the OIII filter seems to be perfectly even without any artifacts).

I tried changing the settings around and following some suggestions I saw online, but the results always comes out looking like this...
I'd be grateful if you had any recommendations of things I can try out!

The flats are as expected but are they calibrating the lights correctly or do you still see the pattern in the calibrated stack? If not the it's ok.