Can broadband camera data be stacked in LRGB groups?

[irandar]

Hi folks,

I have a set of 400 lights, 50 darks and 50 bias from Andromeda, obtained from a FB group contact. These are from a Nikon camera, NEF files. Initially, to keep the time short I was thinking of stacking about one quarter of the files. This could be done all in one group by selecting the type of file.

But I was wondering if the files could be artificially separated into LRGB and stacked as 4 groups. I guess with a portion of the darks and bias in each group. Then the JR composition of LRGB could be used. Would this bring a useful result?

Thanks for your advice, Irving

[James Ritson]

H @irandar, I'm assuming the files are all OSC since they're from a Nikon camera, in which case I wouldn't try and artificially split them into mono channel data straight away.

What you could do is stack portions of the light frames and use the same calibration frames each time, e.g. stacking the light frames in groups of 0-100, 101-200, 201-300, 301-400. You could use file groups for each set if you wanted to do this. However, I'm unsure if it would actually offer any speed benefit over just stacking all 400 frames in one file group, to be honest.

If you did take this approach, you would end up with multiple data layers once you apply the stack. You can select these layers, then go to Arrange>Live Stack Group and change the operator to Mean. This will average the layers and reduce overall noise further. Then you could either flatten (Document>Flatten) or Merge Visible (Layer>Merge Visible) to create a new pixel layer from this result.

At this point, you could try using the "Extract OSC Layer to Mono RGB" macro in the Data Setups category, then try either "Mono Stretch (RGB)" or "Mono Log Stretch (RGB)", the latter of which will be more aggressive. Finally, you could then colour map using "RGB Composition Setup".

There isn't actually a macro to synthesise a luminance layer, but I could actually add this in an upcoming version.

Hope that helps!

[irandar]

@JamesR_Affinity  Many thanks for your detailed answer. I now stacked 400 lights, 50 darks and 50 bias. APv1 said 371 files. On my iMac it took 4-5h. My Mac went to sleep on the job so I had to reset the preferences. The guy whose files I used said he took 7min to stack with Sequator. His result looks ok, although there was a slight bit of star trailing. That time difference does seem a bit extreme. My mac is not the newest but not so old either.  Just wonder about your experience. Interesting is that saving after stacking gave a 300MB file. I will edit it now. Best regards, Irving

  Model Name: iMac

  Model Identifier: iMac18,1

  Processor Name: Dual-Core Intel Core i5

  Processor Speed: 2.3 GHz

  Number of Processors: 1

  Total Number of Cores: 2

  L2 Cache (per Core): 256 KB

  L3 Cache: 4 MB

  Hyper-Threading Technology: Enabled

  Memory: 8 GB