Can't get photos to align when stacking

[Jameedon]

I've been using DSS for all my stacking but now I'm trying to switch over to PI but I can't get the photos to align when stacking (I'm using a Canon T4i full spectrum).  At first I tried using the script BatchPreProcessing but after like 2 minutes an error message pops up that says something like cannot stack less than 3 images, but I had 40 light frames (also darks, flats and bias frames).  I attached a screen shot of the last bit in the process console, maybe there's a clue of whats gone wrong?  It does say "unable to find a valid pair of star pair matches" but 2 lines above that it says "58 putative star pair matches"... This set of data isn't the only set I've tried but every time it ends with the same error message.

Since I couldn't get that script to work I tried the StarAlignment, ImageCalibration and ImageIntegration processes but in the end the stacked image looks like there was no attempt to align anything, just stacked on top of each other.  I attached a JPEG copy of the FIT file after ImageIntegration was done, at least I hope I attached some photos.

I've watched like 5 different tutorial videos on how to use PI to align and stack my images and I can't see what I'm doing wrong (I'd be shocked if it wasn't me doing something wrong).  From what I've described, does anyone have any ideas on what's going on here?

[Phil Leigh]

can you load your light frames into the subframe selector batch processing script and let it analyse them - see what it says about FWHM (star resolution) and star  support (number of stars) for each frame...
The selection of reference frame is critical to alignment - the frame with a low (but not zero!) FWHM score and a HIGH "Star Support" score makes an ideal reference frame.

If you don't choose a ref frame, Pi takes the first one in the alignment list...

[TobiasLindemann]

At higher focal lengthes with big stars I would try to increase the "detection scales" up to 7 or 8 in the "StarAlignment" process

[georg.viehoever]

You should experiment with the StarAlignment process directly. It has a number of diagnostic modes that show you which stars it finds, and which stars are matched. Than you vary the parameters in the star detection and star matching sections so they work with your image. After you find some working ones, you can use those with BPP.

Your image also seem to have severe vignetting. Check your calibration! If it cannot be fixed by calibration: I have seen cases where this prevents StarAlignment from working properly. Try cutting the region of interest first, and then do StarAlignment on those reduced images.

Georg

[Jameedon]

Last night I uninstalled the PI trial because I bought a license and then I down loaded a new PI from the link they provided.  So before I worked on solving my stacking issue I thought I'd try it first to see if this newly download PI would magically work, so I loaded all the data into the BatchPreProcess script and started it.   After about 5 minutes a new error message popped up which said "At address 000007FEFD56940D with exception code C0000005 :Access violation: invalid memory read operation at address 0000000100000019", I have no clue what its about.

So then I loaded the light frames into the ImageIntegration process and when I hit the apply global button the same message error message popped up.

Does anyone know what this is about?

Phil - I don't see a subframe selector script under the batch processing section or anywhere else.  Am I looking for the right thing?  I did select a reference frame which I determined to be a good choice because I looked through all the subs and I thought that that image had the best stars that weren't distorted from seeing conditions.

Georg - I will look into what you're saying as soon as I figure out access violation error I'm getting.  That image I posted of the stacked photos was done without calibration frames.  When I used DSS to stack this same data the calibration frames did their job as was expected, the image looked good (except for needing more subs as usual).

[georg.viehoever]

...
Georg - I will look into what you're saying as soon as I figure out access violation error I'm getting.  That image I posted of the stacked photos was done without calibration frames.  When I used DSS to stack this same data the calibration frames did their job as was expected, the image looked good (except for needing more subs as usual).

PI uses a different method for finding stars and matching them. Usually it is more powerful than DSS. If you are happy with the result that DSS delivers, by all means use it. But PI may give you better results after you learned how to  control it.

Regarding your installation issues: My recommendation would be to do a new download and then re-install.
Georg

[Andres.Pozo]

Last night I uninstalled the PI trial because I bought a license and then I down loaded a new PI from the link they provided.  So before I worked on solving my stacking issue I thought I'd try it first to see if this newly download PI would magically work, so I loaded all the data into the BatchPreProcess script and started it.   After about 5 minutes a new error message popped up which said "At address 000007FEFD56940D with exception code C0000005 :Access violation: invalid memory read operation at address 0000000100000019", I have no clue what its about.

Are you using the 32bit or 64bit version? If you are using the 32bit version, then you have to change a couple of parameters in ImageIntegration in order it uses less memory. You have to reduce the values of "Buffer size" and "Stack size". Please read this thread:
http://pixinsight.com/forum/index.php?topic=4442.msg31488#msg31488.

[cdesselles]

Excellent thread...

I've had the same problem show up where I tried to align and stack 24 frames but only wound up with four being stacked.  Reading the above has given me a good insight into the issue, especially since I usually have vignetting problems also.  I think I now know how to improve things a bit. 

Thanks, Guys

[diurnal]

i was getting the same results as you in your screenshot but my stars would align. it turned out to be bad flats for me. i had to rethink the way i took flats.

in the online manual it says it's usually bad data when you can't align i.e. such as saturated stars. you might want to try the 'blink' tool to look at your data as well.

good luck

[Jameedon]

Well I closed PI and was instructed that there were 16 updates that were available for download so I did that right away, then once when they were all installed I tried the BatchPreProcess script again hoping it would work no, and what I will tell you is it kinda did I think?  I can't say confidently that it did work as it should have because I don't know if it did.  What did happen was I entered all my data with calibration frames and hit start, when it was done the script disappeared and there were no images on the screen so I checked the output folder to see if there was anything in there and there was a light-BINNING_1.FIT file in there.  I opened that file in PI and a rejection high and rejection low image opened along with a gray-scale image of the light frames aligned, calibrated and stacked.  I wasn't expecting for things to work like that (when they did work that is).  I thought the rejection images and the stacked image would load automatically after the BPP script was finished and I thought the finished stacked image would be RGB, am I wrong?

Andres.Pozo, I'm using a 64-bit PC.  I just had it custom built so I could use PixInsight.

Georg, I want to use PI instead of DSS because I know it gives you better results (and a hard time).

[pfile]

make sure to tick "CFA images" to tell BPP that your camera is a DSLR/OSC camera... that's probably why you still have mono images, and probably why they would not register...

rob

[papaf]

Jameedon, the fact that you have a 64bit PC is not enough. You have to verify that both your operating system and PixInsight version you've downloaded are both 64bits, just to be sure.

[Jameedon]

lol, come on, give me a little bit of credit.  I have Win 7 pro and I did download the 64 bit Windows version of PixInsight 1.8 RC7.

I think those updates that were done were magic.  Magic is my explanation I give when the computer fixes its self since I don't know how or what fixed it.  My computers do magic about 3 times per week.

I attached the stacked image that Batch PreProcessing did.  Can someone tell me this, When you run BPP does the finished stacked image end up on the screen when BPP is finished or do you have to go into the output folder that you set and open the image from there?

Thanks Rob for that little tidbit about the CFA box, that did the trick.

[papaf]

I didn't want to offend, but you wouldn't believe what's out there. A friend had his computer reinstalled by a "tech savvy friend", and bam, win 7 32bit on a 64bit machine...
Glad you got it working, though!

[Jameedon]

Don't worry about, I make fun of myself too much for someone else to offended me.

I've been messing around with this Batch PreProcess script and I'm very surprised at how much better this stacks than DSS.  It seems like the alignment is better too, but the bad pixel subtraction is amazing. 

Whats the deal with the message that pops up after you hit the start button on the BPP script?  It says something like this script is used just to give you a visual of the data you have to work with and it doesn't do as good of a job that the processes do.  Is that the case?  Does anyone notice that the BPP script is subpar to the integration processes?