stacked image from dslr Monochrome modded camera

[NGC664]

Hi, I must be bored but I acquired a few Canon 350D cameras and took the least used unit and removed the bayer Matrix from the sensor. I took a few JPGs out the front door and the image was magenta until I did a custom white balance and then viola a very crisp monochrome image. Since I will be taking raw frames and stacking them in deep sky stacker, what will Star Tools do with this image since RAW probably doesn't care about the white balance I have set. I have been using Star tools for several years with great results only using my Sony A6500 .

[admin]

If you removed the Bayer matrix, there is no notion of color any more, and any debayering will just result in "nonsensical" colors (while also throwing away signal through unnecessary interpolation).

Make sure you do not debayer images in DSS (not sure if it will allow you to turn that off). If you cannot turn it off, you should be able to batch-preprocess your CR2s manually using dcraw, with the right options set. The resulting output of that can then be stacked in DSS.

Do let us know how you get on. This is an interesting experiment.

[Mike in Rancho]

Yes, there are a number of potential pitfalls here. As I think Ivo alluded to, your jpeg isn't really doing what I think you think it is doing. It will be demosaiced and interpolated into what it thinks is RGB, despite the missing matrix. The red cast, well, who knows how that came about, even if the UV-IR cut is now missing, and you found a way to "white balance" things into gray submission. The good news is that you haven't yet seen the crisp resolution increase that you should obtain from your mono mod!

Unfortunately, DSS will force debayer anything in a RAW format, you cannot turn it off. You can do so with FITS files. I am unsure if any acquisition programs will write out FITS from a DSLR, however. As far as I know NINA will save RAW files (NEF, CR2, etc) from DSLR despite having the program options set to 16-bit FITS.

Freddy, an ST-user and member here, also has a mono modded Canon. At first he was using dcraw to batch process his CR2's by saving them as TIFF using a special command line option for no interpolation. Ultimately he gave up on that and now uses PI for his stacking, as it has an option for no debayer/interpolation of RAW files.

I believe I tried ASTAP on some of Freddy's sample mono CR2's, and that didn't work out either, even though I thought it might. But ASTAP is updated frequently, so might be worth a look to see if anything has changed.

Another potential issue is just what the "black box" of Canon RAW pre-processing is doing. In many cases, nobody knows, unless they can reverse it out and come to conclusions via experimentation. That's how things like Nikon's lossy compression bucketing were found out, and a fix devised. But other things are done to massage RAW files such that they aren't really, fully, RAW, like you'd probably get from an astrocam. Thus, it's possible that you might have the pixels for your red and blue "channels" increased, even though the matrix is now gone, if Canon does that sort of thing.

It might be worth looking around to see if those who currently use mono mod Canons are also implementing some kind of replacement firmware hack which eliminates any such problems, or at least confirm whether or not it is something you need to worry about.

It may very well become apparent visually when you get your first looks at one of your mono CR2's.

Let us know what you find out -- it does seem very interesting!

[LuckyEddie]

Siril will convert raw to fits and also gives control of if (and how) to debayer.

[Mike in Rancho]

A little update -- I was working on some experiments for a different conundrum last night, and I think I may have found a way that this can be done properly using DSS. It's a couple steps, so PI or Siril may be more efficient, but I believe it works.

After loading your RAW files and setting everything up (registration, DSS options), make sure that you are in Standard mode, and in the Stacking Settings / Intermediate Files tab select the option for "create a calibrated file for each light frame." Below that, then make sure that "save a debayered image when processing RAW images" is NOT selected. Also select to make sure you use FITS, not TIFF. Then perform a stack.

What ends up being created is a 16-bit FITS file for each RAW. They will be placed in the lights folder. If done with only the lights loaded and stacked, it is really just a conversion from RAW to FITS. But you can also load your calibration frames (calibration is performed in the undebayered state anyway). The "intermediate" files will have a .cal appended to the name.

After that, discard/delete the autosave that was created as part of that stacking process. Then, if you want, copy or move all your new .cal FITS files into a new folder. Either way, you can now clear and load a new set of files to stack in DSS - the FITS files you just created. And now you will be using the FITS side of the RAW/FITS settings, where you want to have the option for "monochrome 16 bit FITS files...created by DSLR/color CCD" set to OFF, so that no debayering/interpolation is done. At this point you could probably also choose intersection mode if you want to.

When this set is stacked, that resulting autosave will now be your final mono without any demosaicing and interpolation having been done.

I still have a handful of Freddy's mono CR2 light subs, so gave it a run-through and it seems to work.

Ol' DSS still has some tricks up its sleeve after all.

[NGC664]

Here is my first attempt using my Canon350D minus it's bayer matrix. I wish I had a good workflow . I did use compose with mono selected. This was 30second exposures at iso 200. Underexposed because I did clip the blacks a lot. About 15 minutes total exposure time. No filters at all.

[U308041]

Just another note on above image, I did convert all the lights and calibration frames from CR2 to DNG files using the free Adobe DNG converter. I then stacked in DSS. I had not seen the previous suggestion but will give that a shot too.

[Mike in Rancho]

Same user different name, I take it?

That is pretty cool-looking. A good start on some detail I think. Yeah unsure what workflow you applied, but the stars seem rather blown out. FilmDev? Then again I'm used to watching my AP in color.

Do you have a further explanation on the DNG? I'm not really sure how that fits into helping. (pun sort of intended)

DNG is Adobe's "universal" RAW file. I actually use the converter (it's very fast too) all the time, as DNG is the required format for Mark Shelley's D5300 lossy compression repair program. In any event, all it does is convert a CR2, or NEF, into the universal DNG. It is still a RAW file, which means that DSS will interpolate the bayer matrix (absent Superpixel or Bayer Drizzle).

Try the method spelled out above by using DSS to "convert" your RAW files to undebayered FITS, so you can then load them into DSS which has an option for mono FITS. Or, use Ivo's method from the early post using dcraw in command line. Then your stack should really show off the clarity increase from your mono DSLR!

[NGC664]

Mike, I followed your instructions and used all my calibrations files as well. Restacked the FTS .cal files and ran it through ST. I did use the compose mono from dslr/osc. Not sure if that was the best choice. I also decided not to bin as this is only an 8MPixel camera. Normally with My Sony A6000 I bin to 25% since it has 24 Mpixels. I was not guiding /dithering for this image as I was just interested in seeing what the camera could do. I do have a couple of clear nights possible this weekend and I will increase exposure time and put some filters in to get rid of star bloat. I appreciate your thoughts and procedures you offered.

[Mike in Rancho]

Hmm, I'm not sure how compose mono from OSC/DSLR would work here, though perhaps no harm no foul depending on what you loaded in.

If you took all those .cal FITS subs created by DSS, and the debayered wasn't chosen, then when subsequently stacking those (and making sure the "mono FITS = color" was not checked), your stacking output should be a pure mono file.

So, simply using Open should work, and ST knows what it is and what to do with it.