asi2600mc very noisy images

[bluesilver]

Hi, Not sure if i have got this posted in the correct section here or not.
I have just had a good clear night last night to try and do some imaging of NGC 6744 and also NGC 6334
Camera is asi2600mc, scope is Sykwatcher Esprit 150
All images are 2 minute exposures at gain 100 and -10c
I stacked 50 lights, 50 Flats, 50 Bias frames
Light frames were done in APT at 22000ADU
Stacked in DeepSky stacker and processed in Startools

As you can see the noise is very very bad,
NGC 6334 has some very bad sort of white glow effect going on also.
I took the flats and bias right after i finished taking the lights, so nothing was disturbed.

Something is way off here, I am not sure if it is a noisy cable form the camera ( standard ZWO cable )
Not sure if i should of included Dark Flats and Darks also in the stacking process?

In DeepSky Stacker, under Stacking Parameters, under Light, you have 3 options:
No Background Calibration
Per Channel Claibration
RGB Channels Background Calibration
( I selected the last one, I think this is what it is at the default settings anyway )

The you have an options button with:
Linear
Rotational
( i selected Rotational, again i think this is the default setting )

Then you have RGB Background Calibration Method:
None
Minimum
Middle
Maximum
( I selected maximum, think this is the default setting )

When all stacked and finished, i saved it as a TIF 16 bit file

Open in Startools as a Linear from OSC/DSLR
Using the wipe function and tried both basic and vignett options.

So something is at a miss here or i am stacking it all wrong.
Any advice or suggestions would be very much appreciated.

[Drac0]

Looks like I'm mistaken with this camera. :)
Cheers,
Mark

[AdamJL]

Are you able to upload the stacked files somewhere? Your images are quite small here; it's hard to see noise which requires a close up view.

That said, the Wipe function in ST shouldn't be used as a metric for noise. It purposefully does a very very aggressive stretch of the image so you can see any issues. Personally, I really don't like it how it does it, even though I understand why it does.

The first image though, looks like a (very bad) bad flats problem. Are you sure your flats were taken with the same settings and without the image train changing?

Also, ditch that flat cable. It's the first rule of thumb with ZWO anything... those flat cables are better used as linguine than actual data transfer cables. It likely won't have caused your issues, but you're just delaying the inevitable by using it.

And lastly, stick to Lights, Flats, and Bias only with the 2600 cameras (and 268s). You don't need to do darks and dark flats, your flats problem will get worse (speaking from experience as I've seen it happen to my own images)

[Drac0]

That's interesting. Learn something new every day. Do the bias do enough to deal with hot/stuck pixels?

[bluesilver]

Thanks for the replies,
Yes 100% sure all flats and Bias were taken right after the Lights were done.
So that part is done correct then, just Flats and bias.
I wanted to make all setting weren't changed at all.
I have had this light glow issue now on a few attempts, i thought i was a flats issue, so lowered the ADU from 30000 to 22000 for this run to see if it helped, afraid it didn't though.
I uploaded the files on here to jpeg and reduced them by 25% as they were a tad large.
Tried uploading the same version but at 100% but it won't allow it here.
I am not sure where else to upload the full version to yet, will have to look into that one.
Will look at replacing that flat cable, If they make a shielded USB A to B cable, that would be best, If so i would also look at replacing the cable inside the mount to a shielded version also.

I am now thinking if it could possibly be a smoke haze for a neighbors fire,
Was sitting at about 1 degrees outside when these were taken.

Next thought was to do a back to back comparison with my DSLR, run an image session with the DSLR then swap it straight over to the asi2600mc and run that , but the specs say that the asi2600mc should be far superior in all areas.

[AdamJL]

It's only these modern sensors. A couple of other cameras use the same sensor design, and they really don't benefit from darks or dark flats. Mainly because there's just little to no noise anyway.

As for hot pixels, I haven't seen any in my 2600MC or 268M, but I haven't looked too closely. Dithering is how I combat that!



Can I ask how you're taking your flats? Are you using a man made source or the sky?
I would check for light leak in your train. If you're getting it more than once, it appears your camera might be picking up stray light from somewhere, as flats are usually taken with a much brighter source and so light leak can show up easier.
Spend some time covering various parts of your scope, check for internal reflections, etc.
I don't envy you on this stage, because I'm still trying to fix some internal reflections of my own and it's not fun.

For image hosting, if you have OneDrive or similar, you can upload them there. Failing that, I'm happy to host them on my own OneDrive if you want. Send me a PM and I can send you the link (and then share it here, so others can also play with the files)

[The_bluester]

I have actually found the opposite with regard to darks, with really good flats (And your master flat and master bias should be 32 bit not 16 bit) you can sometimes see a slight brightening in the corners at high stretches unless a master dark is used along with a master flat. When I first got my 2600MC I used master bias only to calibrate both lights and flats, but soon moved to master bias for the flats to generate a master flat, and that master flat and a master dark, to calibrate lights. Dark-flats are not very useful for me as I normally shoot sky flats so the exposure times vary widely, in the range of 0.2 to 40 seconds per filter.

For the OP, you should be able to create master dark and master bias frames and re-use those for months, you don't need to shoot bias frames to go with each set of lights at the time you shoot them. So long as you use the same gain and sensor temp master bias and master dark frames are good to reuse for months with these cameras. Flats are the ones you don't want to disturb the image train for, to make sure any vignetting and dust bunnies match up with the lights.

[xelasnave]

Have you done a stack with no flats?

I am trying to include flats in my game but with them I am getting crazy results similar to your Cats Paw.

I dont know what I am doing incorrectly and in time will sort it out but I have the same camera ...however try a stack with no flats.

alex

[bluesilver]

Appreciate that advice, so sounds like i have made a mistake in saving my final stacked image to start with.
Should they be TIFF or FITS ? and then should they be 32 bit/ch integer or 32 bit/ch rational ?

All i have been doing in DeepSky Stacker is just loading all my lights in, all my Flats in, all my Bias in and then just let it stack them.

I haven't tried or looked into separate stacking like i think you are talking about?
So it sounds like you stack all your Bias frames first, this generates a master Bias.
Then you load all your lights and Flats in and the mater bias then stack
these?

[bluesilver]

Good point, no i haven't tried it without the flats.
Might even just try doing a stack with just the Lights only and see what that produces, good point there in elimination

[Bassnut]

the 1st picture is exactly what happens in Startools auto stretch if you have stacking artifacts. crop 1st to eliminate these.

[bluesilver]

Appreciate the advice.
The only issue with cropping that image was that the artifacts are all over the entire image.
But i do appreciate what you are saying there.

I just did a real quick try of just stacking lights and bias on that spiral image.
And saved as a 32 bit TIFF and a very quick process in StarTools.
Not a real lot of difference in the result, but appears to be a slightly cleaner image
I will have to come back to this though, as just shift work calls.
Appreciate all advice.

[Startrek]

Hi Peter,
As you probably know I use exactly the same camera and software
Firstly what do you mean by “Light frames were done in APT at 22,000ADU” I’m assuming you mean the Flats ?
Secondly your APT histogram is the roadmap or guide for successful Flats with this camera.
You should adjust the brightness of your flat panel or light box etc..and ADU target value to achieve an ADU range on the histogram of around 8500 to 35,000 ADU or around halfway along the Histogram. Not just select 22,000ADU and hope it’s ok
I found an ADU target of 21,000 to 22,000 was the right value after adjusting the brightness on my light panel and achieving a “ADU range” on the histogram of roughly between 8500 and 35,000 ADU or up to half way

In regard to Stacking with DSS

“RGB Channel Background Calibration” is a definite no no for Startools so set this Calibration option to either “Per Channel Background Calibration”or preferably “No Channel Background Calibration” In “options” leave Calibration Method to Linear and RGB Background Calibration Method to none.

Below are a bunch of settings you should use to ensure your stacked fits file is linear and meets the requirements for loading into Startools

DSS Latest Settings for both RGB and Narrowband data ( Prerequisites for Startools )

1/ Tick “No White Balanced Processing” in Raw Files Digital Development
2/ Leave “Set the Blackpoint to 0” unticked in Bayer Matrix Transformation
3/ Select “Per Channel Background Calibration” in Stacking Parameters even though when using Startools it should be “No Calibration”. I found Per Channel Calibration no issue when using Startools.
4/ Select “Intersection Mode” in Stacking Parameters (helps reduce stacking artefacts
5/ Tick “Align RGB Channels in final image” in Stacking Parameters
6/ Digital Development Process Fits setting and Raw settings select Bilinear Interpolation
7/ In Digital Development Process Settings ensure you tick “Monochrome 16bit Fits files created by a DSLR or a colour CCD camera” when using a DSLR or OSC camera like your 2600MC.
8/ Stacking Parameters, Lights use Kappa Sigma Clipping
9/Stacking Parameters, Calibration Frames use Median
10/ Stacking Parameters, Flats Median Kappa Sigma Clipping
11/ Stacking Parameters, Bias Median Kappa Sigma Clipping
12/ Ensure you save your stacked file as a “32 bit channel integer Fits files with no adjustments applied”
13/ In Digital Development Process Settings under FITS tab , use Generic RGGB for your cameras Bayer matrix ( I have the Latest version of DSS and the 2600MC is not on the camera list)
Leave colour adjustment box as default 1.0000 for all 3 items

I performed exhaustive testing for a month on all types of data earlier this year on calibration frames with the 2600MC and found that Flats and Bias worked fine ( Darks are not needed )
Your Bias frames can be captured at an exposure of 0.000032 sec which is the shortest exposure in the ZWO specs for this camera. I tried 1 sec , 0.5 sec , 0.1 sec as well with no discernible difference. I just use 0.000032 sec

Also when capturing Calibration frames ensure there is no stray light leakage that may be entering your image train.
As I use Newts , I wrap the focuser and camera with a black cloth and fit a shower cap sprayed matt black over the back end of the OTA to eliminate stray light when capturing Flats and Bias frames during the night

The photos you posted look like a calibration issue ( either with colour balance or your background)

Hope in the above info you have picked up something but I’ll keep thinking of things that might have caused this issue

Cheers
Martin

[AdamJL]

StarTools will show you those issues, and then you need to mask them out or crop if they're on the edges. Once that's done, do another stretch and see how it goes (or upload to the link I sent you and we can have a go).

[AdamJL]

It seems like a long way to go about it :question:
You should be able to just chuck your lights and calibration files into DSS without targeting each stack separately. I have never done anything else when I used to use DSS.

btw, TIFF or FITs is fine. I just stick to FITs for the main astronomy programs, then change it to TIFF when I export to Photoshop for the final touch ups.

[Bassnut]

This pic looks even more like stacking artifacts.
draw a box over the central part that has no artifacts and turn off ROI (Region of interest) in stretch. With ROI off the whole image is stretched the same as in the box, ignoring the edges.

[Startrek]

Peter,
If your Flats and Bias have been captured correctly in APT and stacked in DSS accordingly, you will still have issues in Startools if you don’t follow the operational flow chart on the left
Since you are using a 150mm scope at focal length of 1050mm ( assuming no reducers etc.. ) with the 2600MC , your image scale should be as follows -
3.76 uM x 206.3 / 1050 = 0.73 arc sec per pixel which is oversampled
With oversampled data you are encouraged to Bin in Startools to trade off some resolution for noise reduction. A default Bin of 50% works really well and also has 2 added bonuses , your stars will remain round ( not blocky when you zoom in ) plus the image size is more manageable to work with. Your not waiting for the computer to process the task

As Fred mentioned , cropping your image for stacking artefacts and other anomalies is so important before you apply a Wipe and then second or final stretch of the image.

So you should follow the flow chart on the left in Startools -
AutoDev ( forget Film dev ) 1st stretch to inspect image
Bin default 50%
Crop edges or areas to remove stacking artefacts
Wipe default but bump up dark anomalies to say 4 pixels
Then second or final stretch with Autodev using a Region of Interest ROI ( drawn with your mouse around the main body of the object ) Adjust “Ignore Fine detail” slider and “Outside region of interest “ slider a bit to adjust detail and brightness across image

After that you just move on to Contrast , HDR , Sharp and so on ….. to complete your processing

Attached is an image of M17 I captured 2 weeks ago under Sydney’s horrible LP using 3 minute subs ( 3 hours of data ) , dithering , Gain 100 , cooled to - 10C , Flats and Bias stacked in DSS

First image is just loaded into Startools and AutoDev for inspection
2nd image is initial stretch in AutoDev then using Wipe without Bin or Cropping
3rd image is initially stretched in AutoDev , Bin , Cropped and Wiped
4th image is initially stretched in AutoDev, Bin , Cropped , Wiped and second stretch in AutoDev using ROI and sliders ( ignore fine detail 4 pixels , outside region of interest 10% )

You can see the mess you end up with if you use Wipe without cropping out artefacts and other anomalies

Hope the above helps

Cheers
Martin

[The_bluester]

Regards the actual output files, I use Astro Pixel Processor, right up until the final export stage it saves the stacked output as 32 bit FITS, then I export then as 16 bit TIFF to work in Photoshop. I would love to stick to 32 bit files but you are straight away limited in some functionality within Photoshop and have to convert to 16 bit anyway.

[Bassnut]

I think you missed the Startools stage. You export 32bit fits to startools then 16 bit tiff from that to PS?. This is standard. Once stretched, there is no advantage to 32 bit in PS, the dynamic range is already compressed to the point where 16bit is more than adequate.

[The_bluester]

With Astro Pixel Processor I don't use Startools. 32 bit FITS of the stacks saved in APP then finally saved as 16 bit TIFF to take over to Photoshop for post production.

All stacking and assembly of an RGB image (RGB assembly for the mono cam) I do in APP, saving a combined RGB FITS as an RGB TIFF, and likewise Lum and narrowband FITS files saved as mono TIFF images to layer on the RGB image in photoshop. Everything else I do in PS.

[Craig_]

You may not even need flats/bias with the 2600, but it does depend on your image train. I have no material vignette so don't bother shooting flats. Flats would be useful for dust bunnies if you have them though.

I don't bother with any calibration frames on my 533 either (same silicon) albeit vignette is less of a concern on a small sensor.

Dithering and adaptive rejection algorithms in stacking do the job for me!

[bluesilver]

Thanks everyone for the help and advice with this, it is appreciated.

Yes i had a typo there when i said the lights were done at 22000ADU,
it was suppose to be Flats.
I have been playing around with different ADU vales, and the last one was 22000ADU.
It is sounding like ( as most of you are telling ) that the Flats are off, I am going to go back and have another look at APT as i am missing the main part of the instructions that everyone is telling me.

(Adjusting the brightness and achieving a “ADU range” on the histogram of roughly between 8500 and 35,000 ADU or up to half way)

I have just been selecting an ADU, say 22000, then letting APT do it Flats aid calculation.
So there is a way to actually measure the ADU of the flat panel first?
Then adjust the brightness to get the histogram to sit in the middle.
Then with this number, you then set the Flats aid to this number.
I will take a look into this.

I will have a look in the afternoon after i get some sleep, on a night shift leg this week.
I will then work through the rest of the advice given on here, most of it i have done correctly, just not the first part.
I don't think i am getting stray light in the imaging train, the bias frames all look black, might even just take it outside in the daylight and take some darks just to see if there is any light showing up in the frames also.

All very much appreciated.
Thanks heaps,
Peter.

[Startrek]

Peter,
What flat panel are you using for your Flats ?
Does it have adjustable brightness levels ?
Are you stretching a white T shirt over the end of the OTA wth a rubber band ?

I use a Huion led dimmable light panel and usually set t lowest brightness or just slightly above.

Photo my little 6” newt in Sydney taking Flats with APT

I set my panel brightness to lowest , Open CCD Flats Aid , Open the Histigram set it to Local , set APT Flats Aid to say 21000 target ADU , press Run then watch the Histogram move around until it stops. If it stops say between 8500 and 35000 ADU value where it says “Range” and the first peak ( RGB ) is located off the left hand side just away from blackpoint , 2nd peak in the middle and 3rd peak no further than halfway along the Histogram then I check Flats exposure value. For no filter used Flat are usually 0.2 sec to 0.5 sec , with L Extreme filter they can be 5 sec to 10 sec long
If the Histogram is not in the correct range then I adjust the light panel brightness ever so slightly or drop the ADU target range to 21,000 or even 20,000 sometimes
The Histogram Range is the key

Hope the above helps

Martin

[Stephane]

Hi Peter,

Definitely check for light leaks as previously suggested by others. Bias frames will still be black due to their short exposure so if you do have light leaks, they won’t show up on the bias frames.

I had a light leak issue and found the sources by looping 1 second exposures and shining a torch around the OTA. For my Newtonian, the weak spots were the rear end and the focuser. Once I fixed these, I never got those weird patterns again and can stretch my images so much more with no trace of leaks.

Also for flats, is your camera orientation exactly the same? I learnt the hard way that it must be the same.

I hope you fix your issues soon.

Regards,
Stéphane

[Startrek]

Yes as Stephane mentioned camera in same orientation and “Focus”
If camera moved or removed a new set of Flats should be taken eg: 2 nights imaging with camera removed and re installed 2nd night
I use a fresh set of Flats and Bias for each session even though you can reuse Bias
I’ve had issues with DSS and using Masters so I use a fresh set each session , haven’t had any issues to date
They don’t take long to capture anyway.

DSS loading Calibration Frames ( safest option )
1 nights imaging
Load Lights, Flats and Bias into Main group register and stack
2 nights imaging ( camera removed )
Load night 1 Lights , New Flats and New Bias into Main Group
Load night 2 Lights , New Flats and New Bias into Group 1
Register and stack
2 nights imaging ( camera not removed )
Load night 1 Lights, same Flats and same Bias into Main Group
Load night 2 Lights , same Flats and same Bias into Group 1
Register and Stack

NB: I’ve tried the reference frame method for multiple nights in DSS and it’s never worked for me

One important thing I do before loading Lights into DSS , I review the light frames in ASTAP and cull any lights with the following issues -

Bloated stars due to Ra or Dec excursions in PHD2 guiding
Tracking or guiding issues ( Star shape ) zoom in for inspection
Satellite trails
Aircraft trails
Cloud cover even high cloud ( Astap will pick it up )
Other anomalies

Cheers
Martin

[bluesilver]

I am going to go back over and re do the stacking program again as there are a few things on there that i do need to change.
In regards to this one:

9/Stacking Parameters, Calibration Frames use Median

I can't see that option anywhere in DeepSky Stacker.
I even downloaded the latest version just to make sure.
Under the Stacking Parameters tab i re set the Lights, Flats, Bias to the suggested settings.
But i can't see the Calibration Frames tab,
The only thing that i found remotely close was in the Cosmetic tab.
If i click:
Detect and Clean remaining Hot Pixels,
Detect and Clean remaining Cold Pixels,
Then you get the option:
Replace pixel value with the median Test on first Frame

I selected this option and and let it do its Test on first image
It take a little while, but came back with:
Detected Hit Pixels 832023 (3.19%)
Detected Cold Pixels 1494800 (5.73%)
Also left the Alignment method as Automatic.

Sorry for dragging this out, but definitely learning some very valuable information here.

[bluesilver]

Hi Martin,
I am using a dimmable light box for a member on here that is making them and sealing them.
That are 12V dimmable LED light boxes that fit snugly over the top of my dew shield.
So i will definitely be re looking at those Flats again, I can see now where i messed them up.
Yes, i basically just finished the imaging session with my lights, left everything as it is, didn't touch a things and put the dimmable light box on and ran the Flats session, then then did the bias after that.
So that part at least i got correct, just the Flats setting are way off

[Startrek]

Sorry Peter,
Forget item 9 Calibration frames tab ( I corrected that in item 10 and 11 ) and forgot to delete item 9

Do not touch anything in Cosmetics tab
Only check or tick Use all available processors

Stacking Parameters, Alignment tab set should be set to “Automatic”

Finally in Stacking Parameters under Light tab , with Per Background Channel , when you click on this it opens a menu with Options….. click Options and select Linear ( Calibration Method ) and None ( RGB Background Calibration Method )

That’s about it

I tested some data today and used Per Channel Background Calibration as well as No Background Calibration in DSS and the resultant processed image was the same in Startools using identical settings and procedures. But I’m still going to use Per Channel Background Calibration as I’ve always used this even though Ivo from Startools recommendation is use No Background Calibration to keep the DSS stacked image purely Linear.
I’m sure even when you use No Background Calibration your background across a whole session can be fairly uniform under dark skies.

I really hope you achieve some better processed images in Startools
It just takes some time as long as your data has good calibration, registering stacking is done correctly in DSS and the initial processing procedures are followed in Startools

Cheers for now
Martin

[bluesilver]

Thanks again for all this great information.
Just running it all through the stacking process aging now for those two images.
Might try and upload them to the One Drive that was generously offered to be by AdamJL
Cheers,
Peter

[Startrek]

Peter,
Just so you get an understanding of the File Groups in DSS

There are 2 Groups
1/ Main Group
2/ Group 1 and onwards

Light frames in the Main Group are only associated with the Flats and Bias frames in the Main Group

Flats and / or Bias frames in the Main Group are only associated with Light frames in Group 1 onwards

Flats and / or Bias frames from Group 1 and onwards are only associated with Light frames from same group

So in other words, Flats and or Bias placed in Main Group will calibrate with Light frames placed in Main Group or Group 1 or Group 2 and so on …,

You can’t place Light frames in Main Group and Flats or Bias in Group 1 or Group 2 and so on …. and expect them to calibrate, they won’t

That’s why the safest way to load your files is -

Night 1 only, load Lights , Flats and Bias into Main Group

Nights 1 and 2 ( camera removed ) load Lights , Flats and Bias night 1 into Main Group and load Lights , Flats and Bias night 2 into Group 1

Nights 1 and 2 ( camera not touched ) load night 1 Flats and Bias into Main Group , load Lights night 1 into Group 1 and Lights night 2 to Group 2 ( no need for night 2 Flats or Bias as Main Group night 1 Flats and Bias are common to Groups 1 and 2 Lights )

Hope the above makes sense

Cheers
Martin

[bluesilver]

Thanks Martin,
Yes that makes perfect sense,
I have printed out all these instructions and making up a word document so that i can print out and refer back to in the future.
Things are now starting to make sense.
Just a slow learner i guess.
Cheers,
Peter.

[rustigsmed]

https://www.youtube.com/watch?v=Kkg441UBNpo

check this video out (there are actually 3 i think) - it isn't necessarily just about the ADU with the modern cmos, they alter their read out if they are captured quickly (so adu and length of time to capture the adu). Perhaps try and dim the flat source and take a longer flat to get to the required adu. worth a try.

[bluesilver]

Sorry to bother you again with yet more questions,
Got everything back up and running again, just got to test it all out when we get clear skies.
I have ben working on the Flats Aid in APT, It appears that adjusting the light level, ( in my case it is a dimmable light box ) it is like a fine tuning of the histogram, while changing the ADU vales is a more course adjustment, at least that is what i am finding.
Si i have sort of ended up with an ADU value of 22000 for the asi2600mc,
This puts the 3rd peak of the histogram about half way along.
I the images below, the first one is with an ADU vale of 22000 and the range comes back at 12338 - 31587, i think this is look ok.
The second image is with an ADU of 30000 and the range is 16494 - 41419 and the 3rd peak is a little over half way along, but i think this is way over exposed.
I use the astronomy.tools to work out the arc seconds per pixel which comes back very simular to what you have said, 0.73 or 0.74 using astronomy.tools site

I do get wildly different histogram results depending on what you select on the histogram, ,like Log, Auto St-L, Auto Str-R, Local ( the range results remain results unaffected of course)

So just interested to know if i am on the right track here, to me it looks good, but still learning about this.
Cheers,
Peter.

[Startrek]

Peter,

Yes you are on the right track !!!!

I’m using APT v3.90 whereas your using v4.10 which has a few more features like showing the Gain value in Flats Aid but generally both do the same thing

Yes your key to good Flats is your “ADU range on the Histogram” with Local button , you just have to juggle the ADU target value and the brightness of your light source to achieve the best range ( definitely a Range no higher than 35,000 or halfway. 31,000 to 33,000 max on your ADU histogram Range is excellent)
The ADU range of 12,100 to 31,000 approx and your Histogram looks OK to me

Another thing to check is on the left side of the Histogram you just want to make sure your not black clipping but your 1st peak or left hand peak is around 12,100 which is fine , my 1st peak or left hand peak is usually around 8,500 to 9,000 which is also ok

Do you use a white T shirt stretched over the end of the scope ? I find a nice white T shirt works well, it gives you some flexibility with your light source and ADU Range.

I usually take 40 Flats and 60 Bias

A lot of folk say just take 15 to 20 Flats and 20 Bias but I still had some Vignetting with small amounts of calibration frames
To me the more the better as the calibration will result in less noise due to the Stacking algorithms

I revised the DSS settings again checklist for Stacking and using Startools, so here it is ( only minor changes and an addition)

DSS Latest Settings for both RGB and Narrowband data ( Prerequisites for Startools )

1/ Tick “No White Balanced Processing” in Raw Files Digital Development
2/ Leave “Set the Blackpoint to 0” unticked in Bayer Matrix Transformation
3/ Select “Per Channel Background Calibration” in Stacking Parameters even though when using Startools it should be “No Calibration”. I found Per Channel Calibration no issue when using Startools.
4/ In Stacking Parameters, Lights , Channel Background, under “Options” select Linear and None
5/ Select either “Standard Mode”or “Intersection Mode” in Stacking Parameters (Intersection helps reduce stacking artefacts)
6/ Tick “Align RGB Channels in final image” in Stacking Parameters
7/ Digital Development Process Fits setting and Raw settings select Bilinear Interpolation
8/ In Digital Development Process Settings ensure you tick “Monochrome 16bit Fits files created by a DSLR or a colour CCD camera” when using a DSLR or OSC camera.
9/ Stacking Parameters, Lights use Kappa Sigma Clipping
10/ Stacking Parameters, Flats use Median Kappa Sigma Clipping
11/ Stacking Parameters, Bias use Median Kappa Sigma Clipping
12/ In Stacking Parameters under relevant Tabs , only tick box at bottom that reads “Use all available processors”
13/ Ensure you save your stacked file as a “32 bit channel integer Fits files with no adjustments applied”

No problem if you any further questions or queries

I’m still learning as well after 5 years at it , you never stop learning in this hobby

Cheers
Martin

[bluesilver]

Thanks Martin, very much appreciated.
Good to know i am heading in the right direction now.
I didn't use the white T-Shirt method, mainly because my light box sits down over the dew shield, so the dew shield is sort of half way inside the box.
A tad tight to get a T-Shirt stretched over in there, but i might give that a try next time as well to see if that makes any difference even though the box has a dimmer on it.

[The_bluester]

Just looking at your attached images there and noted you are using gain 100, I never use that for flats as I found it produced flats which corrected quite poorly. At gain 100, each electron is about 5 ADU and I found the result to look quite posterised when applied to lights and integrated.

I always do my flats at gain 0 with my 2600 cams (Both mono and OSC) and I don't aim for a specific AUD, just somewhere in the 20,000-30,000 range, so long as nothing is down near zero and nothing near saturated.

[Startrek]

Paul,
Thanks for your experiences
I found not matching light frame Gain to Flat frame Gain doesn’t quite correct dust donuts other similar spots etc
I use both Gain 0 and Gain 100 to capture my lights in two different locations and corresponding Gain for my Flats and Bias and found no major issues.
Although in saying that my Gain 0 calibrated images are always so much better in regard to SNR due to the Bortle 3 skies

Cheers
Martin

[bluesilver]

Appreciate the advice there,
Might be worth while next time i get some clear skies to do a run of Flats at Gain 0 and a run at Gain 100 then do two separate stacks to see what the difference is there.

Might also try taking some Lights at Gain 0 to see how they perform as we have around Bortle 2-3 skies here.

[The_bluester]

I have not been using my MC a lot lately (Too little clear sky and I have been too busy to manage two scopes at once) but I normally shot everything at gain 0 with the MC, with my MM, I typically shoot lum at gain 0 and RGB and Narrowband at gain 100.