Stacking Images

[gjasiewicz]

I am very new to this camera and wonder if there is more detail manual than the version off the Atik website or on the CD.

I am sure there will be more questions with time however, for now I like to understand how the stacking works on this camera. Are the images sent to PC and the software on PC does the stacking or the stacking is done in the camera by internal software.

Also, On the Atik PC software there is a box showing how many images are stacked. Sometime this number remains at 1 (with stack box checked), sometime goes 1,2,1,2...and stops itself at 1, at other times the number goes up by one to the max I had was 11 and then the counter goes from 1 to 11 many times and when I stop it  stays at 1.

[Jo]

The images are sent to the PC and it's the software that does the stacking. It essentially draws a kind of net around the stars in the image and uses that to align and stack them correctly.

If an image comes in that's very different from the previous image, it won't be added to the stack, but you should be able to stack far more images than you are - an indefinite number, really. Is Reject FWHM checked, and what level is it set to? Are you getting high numbers next to Rejected or to Not Stacked?

Thanks,
Jo

[KenT]

Hi,
     Try unchecking "Auto Reset Stack", down on the bottom left, it sounds as if your stack is resetting due to tracking errors. You may get a little movement , and you will see your tracking error distance, if it manages to keep up with your mount.
Good Luck, Ken

[gjasiewicz]

Thank you very much Jo and Ken for taking time to read my post and to reply to it.

It took me a while to setup the scope and the Infinity to go through your suggestions. I looked at the Arcturus and surrounding, then at the M13.

First replying to Jo's comments:
1. I did 0.1, 0.5 and 1 sec exposure
2. Bin set to 1
3. Auto reject set to Full range
4. The images are not very different at all, I see then clearly on the screen.
5. Stack Images is checked
6. Reject FWHM is checked
7. FWHM reject level - I setup first at 10, then 5 and then 1

With all the variations above, there was one time when I saw stack # going to 45 and the stack info few seconds. I thought this was going somewhere so I left the setup for few minutes waiting for stack to go to much higher number but when I came back the stack was zero.

This brought me to Ken's suggestion to uncheck "Auto Reset Stack" on the bottom left. I could not find the exact button down the bottom and did not uncheck. Then, I was reading manual and I think Ken may have referred to "Auto Range" and "Auto Range Type" however, the manual clearly states this is for black level setting. As I mentioned above, I do not see "Auto Reset Stack".
Is it possible I have an old version? Looks to me that you have the same on the web site.

If you find time, please review and provide more advices.

Also, is it possible to experiment with infinity punching few pinholes in the plastic cover?

Best Regards,
George

[elpajare]

Hello gj

I suggest you do this:

Start the session choosing a light star or a open cluster. Not a bright one or a globular cluster.

Choose " Finder mode"

Set exposure at 1" and binnig to 4

Focuse your target >> "Show image quality" >>"numbers only" a big red number will appear on your screen. Focuse  until this number is no more high than 2

Move the histogram white bar to the right to decrease light the maximum possible.

Switch to "Video mode" and increase exposure to 5" and binning to 1

Start stacking.


Example of Markab at Pegasus. 26 exp. x 5" each

[gjasiewicz]

Elpajare,

Thank you for the procedure with recommendations. I will follow it tonight, step by step and will share with you and with all others who are reading this thread.
I will work on Markab if I can see it from my observation point or if not, I will use Polaris that is only slightly brighter than Markab. Will try similar settings to your sample.

Question, why you do not recommend globular cluster or bright star? I understand they pose different challenges but for the sake of experiments would M13 be better than darker objects?
I am pretty good with DSLR use for astrophotos, but have no experience whatsoever with specific astro-cameras.

Take care,
George

[elpajare]

Hello George

In order to have a exact focus you need to use faint objects. You will see that the red numbers go down just 2 that is a good focusing.

With bright objects you never will achieve it.

[gjasiewicz]

Thank you Elpajare.

I just came back inside from experimenting with your procedure and it worked. There are still many combination of parameters that I need to work with but I think I understand your procedure and also the focusing explanation.
With exactly the parameters you recommended I was getting too many rejected frames, roughly 1:1. I did get similar picture though to yours.
With the focusing by number, I did get down to zero. I do not quite understand yet the FWHM setting.

As an experiment I swung the scope from the Markab to M13 and started stacking. I tried 5 secs bin 1, and with FWHM set to 3, 6, 9 the stacking did not work showing zero and rejects one. This was not changing for close to 5 minutes. I turned the FWHM Reject off and stacking went flawlessly up to 45 exposures. After that I turned it off.

I will appreciate any other comments and recommendations.

Best Regards,
George

[elpajare]

Reject FWHN, rejects all the frames whose number ( the red number) is higher than the limit you have put in.

When I take a picture of a bright object, the red numbers are higher than a faint objet so you can do 2 things:

Increase the level number of rejection or turn off the automatic FWHM rejection.

If you are sure that you have good focus ( done as I have explained before ) you can turn off automatic reject off FWHM without problem.

With bright objects, my RED NUMBER never is low than 6 or 7- Even I have a good focus. If you have put the rejection FWHM nº lower, you can't stack any picture.....

[gjasiewicz]

Elpajare,

I appreciate you finding time to educate me. I have learned what the FWHM is but did not find any explanation what to do with it. Your comment is straight down to the practical bottom and I will let you know what I find. I am getting ready to experiment some more tonight.
Couple questions again:
1. after saving your stack, where you find the details like how many images stacked, exposure time and all other info
2. when stacking some faint object, do you see live improvement with progressing number of stacks? My understanding is yes but I did not notice it yet.

Best Regards,
George

[elpajare]

Thanks George. We are all learning here and is nice to share experiences.

More about FWHM, after saved the picture I think that all parameters uses are lost. You must annotate when you are saving the picture.

When you are saved the first object, you wil have the tree histogram bars ( black, orange and white ) in a particular position, the best for have a good image.

If you go to another object, without touching the bars position and you make a zoom over the object you will se how the picture are changing every time a new stack image comes on.

It would not be a bad idea that someone of ATIK give us some practical and theoretical classes on FWHM, ja,ja,ja...

[gjasiewicz]

Elpajare,

I am glad that's how you look at that. Right now I don't think I contributed very much but I own the Infinity for about 1/2 year but started using it only about 3 weeks back and that not full time. I hope I will contribute some experiences perhaps not for the sake of advanced users but for more juniors than I am.

Starting from the back of your post, yes, I agree that Atik could present users with some more details of what is in the manual at the very high level. Jo, are you following and can you help with that?

I had a feel that there is no way to retrieve info from the stack but have not tried to record and play sessions. That may show what you do.
Perhaps in the next release Atik can incorporate metadata with stacks or even individual images. Again, Jo may want to take a note.

I did some more experiments with the Atik last night and to avoid worrying of tracking/guiding accuracy I set up the night with Altais and ended with Polaris.
So, this is what I found:
1. Altais - Started with 5sec BIN1, Auto range off, Stack and Reject FWHM checked, FwHM level 10.5. Stacking stopped at about 80 images (400s)
2. Altais- same as above but Reject FWHM unchecked, same happened.
3. Polaris - started with 5 then 8 and then 10 secs exposure, Bin 1, Auto Range off, stack and Reject FWHM checked and set to 10.5. The stack resets around 105 images.

Jo mentioned that you should be able to stack indefinitely and KenT recommended to uncheck Auto Reset Stack. None seems to work for me.

More to come.

Regards,
George

[elpajare]

I never exceed 300 s per image and never have had a problem of stopping stacking.

Infinity hasn't cooling and I fear strange effects in the chip because temperature, so I never do it.

In my limited experience 300 seconds is enough to fill completely the chip. I have photographed galaxies of mag 14,5 without problem.

May be Jo has another explanation......

[gjasiewicz]

Elpajare,


Actually in response to my original question starting this thread Jo had mentioned that I should be able to stack infinite number of images. I really think this is theoretical capacity and you are right, 300 secs should be sufficient for anything that I would like to do. This would be perfect if it always worked. My problem is that with some settings where I understand all should work, I get resets after 3-12 images. I did not write all the settings but next time I will test it and document.  Not sure when for it looks cloudy today and forecast is for thunderstorms over the next few days/nights.

I agree with you that the chip is not cooled and this may cause some issues that will be more pronounced in warmer climates. I am near Toronto, Canada and daily we are having 30-32C and nightly low to mid 20s. The last two nights though it was 15 and 18 degrees what should be very reasonable.

Anyway, I will focus on finding settings allowing me a min 250-300 secs stack.

I am not sure what you mean that 300 secs will fill the chip............ As Jo explained, the images are sent to your PC where the stacking happens. So, the camera handles really one image at the time and unless you go to 300 secs exposure, the camera handles only 5-10 secs at once. Am I wrong?

I will be sharing my future experiences whenever I make them happen.

Regards,
George

[elpajare]

You are right about "fill the chip", if as Jo saids, is the PC the one who stacks the images, the light captured by the chip is the exposure seconds of each photo.

This night I try to minimize the noise of the picture, and these are some results taking pictures of galaxies mag. 12 and starfields adjacents:

10" exposure to 300 " total, when I did a high zoom in a bright point of the image, I can see some colored dots ( green, blue,red)

10" exposure to 400" total, the colored points dots  almost disappears !!

So, increase light means reduce noise, and for deep sky objects like faint galaxies a 40x10" exposure may be good.