Auto Stretch and Save at Start

[Wknight]

I am new to PixInsight and hopefully I am doing something wrong, but when I do the Batch PreProcessing I am finding that if I don't do a stretch on all my images before I start, it doesn't find any stars to do star alignment.

Since there doesn't seem to be an option in the Batch PreProcessing script to auto stretch at the moment I am having to open the group of files, apply an auto stretch to all of them and then save them individually which is a bit of a pain. Is there a quicker way to do this?

[aworonow]

First, look at your subframes with screen stretch on...STF AutoStretch. Make sure that you can see dozens of stars. If not, your images are causing the problem. Probably exposures were too short to get stars well above the background noise.
Then try the procedure (not script) called StarAlignment. It may do that job for you when the batch procedure failed. In any case, StarAlignment has a section that allows you to adjust the sensitivity for finding stars (called Star Detection). The documentation for StarAlignment can be accessed by clicking the middle icon at the bottom right (a page with the corner folded down).

Good luck, Alex

[Wknight]

The exposure is 5mins so that is not the issue. As you say when I do screen stretch the stars appear but without doing that the original file seems to come in pretty dark so can't be processed.

The images have been captured with SkyX and I have come to PI from Maxim where I never had this problem

[pfile]

this is not a thing, one should never stretch images before stacking.

chances are your stars are large/soft/few and SA can't get a handle on them. or, there are a lot of hot pixels which are being detected as stars. open one of your calibrated subs, open the StarAlignment process and change the mode to "detected stars" and then apply SA to your image. you'll get a new image showing where SA thought the stars were. you can then tweak the star detection parameters in SA to increase the count of detected stars. you'll then have to re-run the SA process on your calibrated lights with those settings. not all the SA settings are exposed in BPP so you may not be able to register these subs with BPP.

rob

[aworonow]

screen stretch does not affect the image, which remains linear.

I believe I have heard of this issue elsewhere...where SkyX writes files differently from what PI (and other?) programs expect. This may be the issue. I have never used SkyX, so not sure. Maybe someone else could comment?

Alex

[chris.bailey]

No problem here is using .fits files out of SkyX.