Image integration query

[SteveH]

Hi,

I’m completely new to Pixinsight so I’m presently going up that steep learning curve! I’m finding the various online videos and the PI forum very helpful, but would appreciate any thoughts on the following observation…

I’m acquiring, focusing & calibrating images using TSX Pro plus camera add-on. I’ve created a library of calibration images for a range of exposure times and a set chip temperature (minus 20). The calibration process appears to work fine, and I’ve been careful to match exposure times between light and dark frames. To give me something to practice on I took a series of LRGB images last week (all on the same night, same observing conditions etc.) and after calibrating them brought them into PI. Before starting with PI I visually checked each image and rejected any which looked suspect. Here’s what I found when trying to register and integrate the images:

The luminance images (7x120sec subs): all registered / star aligned and integrated without any issues.
Red images (10x90sec subs): registered / star aligned – no issues but would not integrate. The following message was shown:


Zero or insignificant signal detected (empty image?)
<* failed *>

Using the STF on any / all images there is clearly data there. I get the same fail for Blue and Green Images at the integration stage.

To the edge of the images stars show some elongation (not drastic!) – so I know that my guiding and / or polar alignment and / or imaging train need improving. However if this is a possible source of the problem it’s not affecting the luminance images. I’m also able to stack all of the same calibrated images without any problems in MaximDL, though my intention is to use Pixinsight for all processing work after calibration.

In following the above process I registered the images in batches (L, R, G, & B  respectively) and then attempted the integration in the same sequence. My intention was to finish with four images – L, R, G, & B – each calibrated, registered and integrated ready for the next stage…

I’ve played around with the integration settings but had no luck so far.

Any suggestions would be much appreciated.

Thanks

Steve

[jkmorse]

Steve,

What do the images look like before applying STF?  Are they black or sort of a washed out grey?  And after STF, do they look really washed out/overly bright?

Jim

[SteveH]

Hi Jim - before STF the images are essentially black in each case. After STF The RBG images do have more of a grey background (I would say slightly washed out) - the Luminance is the same but a little less so. I wouldn't say any of the STF images look overly bright. There is noticeably more detail coming through on the luminance image.

Steve

[jkmorse]

Steve,

Just out of curiosity, did you try doing a star alignment and integration without calibration.  I know we will need to fix in the end, but it will provide a clue as to where the problem is arising.  Also, are you calibrating using both a master bias and a master dark?  Also, look at those calibration frames.  Are they black before STF or are they already stretched? 

I have been using PI for over a year now and I keep running into similar issues in the translation between MaximDL and PI where for some reason, on occasion (maybe 30% of the time even when all settings remain the same) either my calibration frames or my lights will end up getting truncated, blowing everything up.  It just happens sometimes so I am totally confused on why it happens and each time I have to find new ways to resolve.  I am betting its a hardware issue or a Windows 8 issue but I has me stumped as to the root cause.  But I will keep working on it. 

Let me know if any of that makes sense or helps or at least tells you where the problem lies.

Best,

Jim 

[SteveH]

Jim,

Thanks for your reply - it's much appreciated. In TSX Pro (as I understand it) once you have created a batch of, say, dark frames a master frame is automatically created when you run your first calibration routine. So I've been working on the basis that I do have masters - bias, darks & flats. I'll admit that I probably need more - I did batches of ten of each type. I'll also take a closer look at my flats - I did these carefully but flats do seem like something of a black art to me

Also, thinking about what you've related, I run TSX Pro and Maxim DL in my observatory on Windows 7 - essentially because of the need for the Ascom platform. And Windows 7 is running on Parallels on a Mac. But I have PI on another Mac in the house, running on OSX.

I think I'll go back to the beginning and re-visit everything from scratch. I'll also take a look at the calibration frames as you suggest.

Your suggestions are certainly helpful and I'll report back with what I find, although this will be a good 2 - 3 weeks from now as I'm about to travel

Thanks again,

Steve

[jkmorse]

Steve,

Once you have it worked out, hopefully, you may find the attached helpful, at least others have suggested as much.  Its a cribsheet I developed and have been updating regularly for the better part of a year now.  If you find it helpful and would like the Word version so you can adapt it to your own needs/style, just drop me an email at jkmorse57@gmail.com.

Best,

Jim

[SteveH]

Hi Jim - your crib sheet is really excellent! Thanks for sharing this - it will definitely help.

Thanks again for your help,

Steve