SHO Soul

[simmo39]

Finally managed to get some Si data for my soul. Still having mega problems with internal reflections and the only way to get a reasonable image was to crop the image right down.

This is my Soul taken with SW 130 pds and Zwo 1600. 40 ha 240 sec. 30 Oiii 240 sec and 25 Sii 240 sec. gain at 200.

Hints and tips welcome.

[david_taurus83]

Unsure whether to start calling this the Mickey Mouse Nebula or the Teddy Bear Nebula!

[simmo39]

13 minutes ago, david_taurus83 said:

Unsure whether to start calling this the Mickey Mouse Nebula or the Teddy Bear Nebula!

Lol, I thought it was jacobs ladder!

[RolandKol]

Nice one!

Sadly, you do not show your internal reflections as I have a similar setup and simply curious

As per image... I have a feeling, your collimation is off.... Your image is heavily cropped and has no bright stars, so difficult to inspect, but a brighter stars have spikes coming slightly off center.

I am almost 100% sure if you would image a bright star you will have asymmetric halo around it and spikes off center.

Processing is very nice,

I you use PI, I would play a bit more with yellow and blue mask from Mask Script.

And at the end, I would cheat a bit by using "Dark Structure enhancement" script

[simmo39]

9 minutes ago, RolandKol said:

Nice one!

Sadly, you do not show your internal reflections as I have a similar setup and simply curious

As per image... I have a feeling, your collimation is off.... Your image is heavily cropped and has no bright stars, so difficult to inspect, but a brighter stars have spikes coming slightly off center.

I am almost 100% sure if you would image a bright star you will have asymmetric halo around it and spikes off center.

Processing is very nice,

I you use PI, I would play a bit more with yellow and blue mask from Mask Script.

And at the end, I would cheat a bit by using "Dark Structure enhancement" script

Hi, thanks for the pointers, yes my collimation is off and I have got the point where I have had enough of trying to get it right. Ill try and post the full frame later and you will see the problems. Im thinking of switching to a SW ED72 just to get better results. I know the field of view will be a bit wider but I dont think that will hurt. I will keep the SW 130  for smaller targets where the reflection can be cropped out.

[simmo39]

16 minutes ago, RolandKol said:

Nice one!

Sadly, you do not show your internal reflections as I have a similar setup and simply curious

As per image... I have a feeling, your collimation is off.... Your image is heavily cropped and has no bright stars, so difficult to inspect, but a brighter stars have spikes coming slightly off center.

I am almost 100% sure if you would image a bright star you will have asymmetric halo around it and spikes off center.

Processing is very nice,

I you use PI, I would play a bit more with yellow and blue mask from Mask Script.

And at the end, I would cheat a bit by using "Dark Structure enhancement" script

Here is the full frame.

[Hallingskies]

I can't see what the problems are here.  It looks great to me.  

But then I'm not a PixInsight-powered pixel peeper...

[simmo39]

Just now, Hallingskies said:

I can't see what the problems are here.  It looks great to me.  

But then I'm not a PixInsight-powered pixel peeper...

Hi thank you. Its a bit rough around the edges. This was been worked to an inch of its life.lol

[RolandKol]

2 hours ago, simmo39 said:

Here is the full frame.

These are not reflections! 
and you can save the full field of this nice Image! .

it is notorious ASI1600 amp glow

there are two ways to reduce it to quite a good results, not sure if you tried them:

1) use bias but taken with 0.3s exp (I used 0.33 just in case) as 0.0003sec Bias do not produce correct results with ASI1600, they are way too random.

or

2) Use FlatDarks/DarkFlats and do not use bias at all... this one takes longer to process and to collect, but will produce better results than 0.3sec Bias.

P.S. Try different ADU level for flats.

I still have not made my mind, which is better 30k or 20k 

[simmo39]

11 minutes ago, RolandKol said:

These are not reflections! 
and you can save the full field of this nice Image! .

it is notorious ASI1600 amp glow

there are two ways to reduce it to quite a good results, not sure if you tried them:

1) use bias but taken with 0.3s exp (I used 0.33 just in case) as 0.0003sec Bias do not produce correct results with ASI1600, they are way too random.

or

2) Use FlatDarks/DarkFlats and do not use bias at all... this one takes longer to process and to collect, but will produce better results than 0.3sec Bias.

P.S. Try different ADU level for flats.

I still have not made my mind, which is better 30k or 20k 

Hi Roland. I used the second method. I have been using a lower ADU ( 17K ) I have tried higher and lower settings with out much change. when I tried 20k I got very dark corners. I may bite the bullitt and try 30k as I have never used an ADU that high.

[RolandKol]

We need @vlaiv to check your image.

He even wrote a short manual about it, but l am on the phone at the moment.

[vlaiv]

Well, for starters - very nice image indeed.

As for calibration, I can't quite tell from that image - color is too mixed up. I think I see issues with both dark calibration and with flats. Single channel images would reveal what a lot - just stretched without further processing.

I do wonder why people have difficulties with calibration of ASI1600 frames. I never had any issues with flats - and I did not follow usual guidelines, like ADU levels and such. I take my flats at extremely short exposures (in milliseconds), and did not have any issues with them.

[simmo39]

1 minute ago, vlaiv said:

Well, for starters - very nice image indeed.

As for calibration, I can't quite tell from that image - color is too mixed up. I think I see issues with both dark calibration and with flats. Single channel images would reveal what a lot - just stretched without further processing.

I do wonder why people have difficulties with calibration of ASI1600 frames. I never had any issues with flats - and I did not follow usual guidelines, like ADU levels and such. I take my flats at extremely short exposures (in milliseconds), and did not have any issues with them.

Hi Vlaiv, Here is the Ha channel. It has just been stretched.

[vlaiv]

To me that just looks like flats problem.

There also seems to be slight issue with darks, but it might just look that way to mine eyes - because I know where to look for it in ASI1600 - and there is something there in above image, but not sure where it is coming from.

Anyway, flats are under correcting (I'm now even not sure if I got the terminology for that right, but let's go with that )

Here I need to do a bit of math - I never seem to be able to remember that, so I need to derive it.

calibrated = light / flat

Calibrated is brighter than it should be - ratio is higher in value, means either light is higher in value, or flat is lower in value.

It's hard to get flats to be lower then they should be - unless you have clipping in flats - but clipping in flats will likely be "central" - or in center of the frame, rather than in corners. So that is not it.

Lights can be higher in value if not properly calibrated - if you did not subtract darks of exactly the same temperature and exposure length, or you used bias for some unknown reason (don't do it with ASI1600).

It can also happen if you fiddled with gain and offset settings between lights and darks.

[simmo39]

11 minutes ago, vlaiv said:

To me that just looks like flats problem.

There also seems to be slight issue with darks, but it might just look that way to mine eyes - because I know where to look for it in ASI1600 - and there is something there in above image, but not sure where it is coming from.

Anyway, flats are under correcting (I'm now even not sure if I got the terminology for that right, but let's go with that )

Here I need to do a bit of math - I never seem to be able to remember that, so I need to derive it.

calibrated = light / flat

Calibrated is brighter than it should be - ratio is higher in value, means either light is higher in value, or flat is lower in value.

It's hard to get flats to be lower then they should be - unless you have clipping in flats - but clipping in flats will likely be "central" - or in center of the frame, rather than in corners. So that is not it.

Lights can be higher in value if not properly calibrated - if you did not subtract darks of exactly the same temperature and exposure length, or you used bias for some unknown reason (don't do it with ASI1600).

It can also happen if you fiddled with gain and offset settings between lights and darks.

Hi again, Im not sure what your saying, so is it worth me upping the ADU value when i take the flats? At the moment I have it set at 17K 

[vlaiv]

5 minutes ago, simmo39 said:

Hi again, Im not sure what your saying, so is it worth me upping the ADU value when i take the flats? At the moment I have it set at 17K 

I don't think that would help.

I think there is something wrong with either calibration, or there is very remote possibility that lights were polluted by some light signal (maybe entering back of the scope, or something crazy like that) - that was not there when you took darks.

Things that you need to check:

1. If you are calibrating subs properly, meaning calibrated sub = (light - master_dark) / master_flat, where master_flat = stack(flats) - master_flat_dark.

2. Do you have matching darks? Meaning taken at same temperature, exposure length, gain and offset settings as lights?

3. Is there any chance that your scope might be leaking light unfocused light when taking lights, and you take camera off the scope when taking darks? Unfocused light can come from few sources - back of the scope, there is usually small gap for mirror collimation - if you have something shining at the back end of the scope, or maybe area around secondary - or rather tube behind secondary gets lighted up by some outside light source, again when you are taking lights?

 

[david_taurus83]

Stack all your light frames without darks or flats calibration. Then stack with darks. Then stack with just flats. Compare results to see where the problem may lay.

[simmo39]

3 minutes ago, vlaiv said:

I don't think that would help.

I think there is something wrong with either calibration, or there is very remote possibility that lights were polluted by some light signal (maybe entering back of the scope, or something crazy like that) - that was not there when you took darks.

Things that you need to check:

1. If you are calibrating subs properly, meaning calibrated sub = (light - master_dark) / master_flat, where master_flat = stack(flats) - master_flat_dark.

2. Do you have matching darks? Meaning taken at same temperature, exposure length, gain and offset settings as lights?

3. Is there any chance that your scope might be leaking light unfocused light when taking lights, and you take camera off the scope when taking darks? Unfocused light can come from few sources - back of the scope, there is usually small gap for mirror collimation - if you have something shining at the back end of the scope, or maybe area around secondary - or rather tube behind secondary gets lighted up by some outside light source, again when you are taking lights?

 

I have a dark library. When i do the flats, i intergrate the dark flats then calibrate the flats by subtracting the dark flats to create a master flat. I then use the master flat and the dark from my library to calibrate my subs. Am I doing this correctly?

[simmo39]

6 minutes ago, david_taurus83 said:

Stack all your light frames without darks or flats calibration. Then stack with darks. Then stack with just flats. Compare results to see where the problem may lay.

Will try that tomorrow, thanks.

[vlaiv]

1 minute ago, simmo39 said:

I have a dark library. When i do the flats, i intergrate the dark flats then calibrate the flats by subtracting the dark flats to create a master flat. I then use the master flat and the dark from my library to calibrate my subs. Am I doing this correctly?

That would be proper way for calibration.

My feeling is that flats are fine, it's the lights that are "problematic" - they contain some signal that should not be there. This signal can come from mismatched darks. You can look at lights fits information to see temperature they were taken at. Maybe they were "warmer" than those darks in the dark lib. Second thing to check would be gain and offset values used for both lights and darks. Since you have your darks in dark lib, I presume they were taken some time ago. Did you change any of the settings in mean time? Maybe installed new version of drivers with new defaults?

[simmo39]

8 minutes ago, vlaiv said:

That would be proper way for calibration.

My feeling is that flats are fine, it's the lights that are "problematic" - they contain some signal that should not be there. This signal can come from mismatched darks. You can look at lights fits information to see temperature they were taken at. Maybe they were "warmer" than those darks in the dark lib. Second thing to check would be gain and offset values used for both lights and darks. Since you have your darks in dark lib, I presume they were taken some time ago. Did you change any of the settings in mean time? Maybe installed new version of drivers with new defaults?

The darks are fresh, only took them a few weeks ago. I havent changed any drivers or other settings. I took the new darks as I had upped the Gain to 200 and have been using that for subs and flats. All temperatures are all at -20.

[vlaiv]

Another question then, just occurred to me when I was reading your last post - did you take dedicated flat darks - meaning same exposure length as flats? Using "regular" darks can produce above result as well.

[simmo39]

14 minutes ago, vlaiv said:

Another question then, just occurred to me when I was reading your last post - did you take dedicated flat darks - meaning same exposure length as flats? Using "regular" darks can produce above result as well.

Yep, dedicated flat darks, I take them straight after doing the flats at the same settings.

[vlaiv]

Did you have this issue before?

And one more question remains - how about light sources near you when imaging? Is there a chance something was shining on inside of the OTA at the side opposite from focuser, or maybe down the focuser tube?

[simmo39]

I have always had issues withe the edges of the image since I got the camera. I have been trying all ways to reduce it. I am in a fairly dark spot with no light shinning into it. This is why I thought it was internal reflections.