Weird Artifact in Mosaic Mode

Gordon

Not that M1 needs to be imaged in mosaic mode, but I’ve been experimenting. What is the artifact that I’m seeing here? Thanks. Gordon

Support@Seestar

Gordon I see from the image that you have cloud or light damage effects when you use mosaic mode stacking, please send us the image to analyze after you choose to save a single one, thanks.

Daemon42

Gordon You're only 19 minutes of exposure into about a 1.5x or larger mosaic so generally at no more than than one full pass which is not enough. The streaks are a bunch of noisy corners laid next to each other as it works its way spiraling out from the center around the larger mosaic frame.
If you double the total exposure time the streaks will start to disappear as on the next pass it runs the center of the imaging over top of those corner streaks, and by 3 full passes, they'll be gone.
This effect tends to be amplified if you're imaging from Bortle 7+ area with a little haze in the sky lit up by the city. The darker skies you can find, the less you'll see this, even on the first pass.

Support@Seestar

Gordon

Thank you. I don’t use Seestar images for post-processing. Although, I have been experimenting with the editing processes within the unit itself. Unfortunately, I have deleted the *.fit file that was previously on the Seestar itself. I have the *.jpg image on my phone however. Please let me know if that would be useful for you to analyze. If so, how do I send the image to you? Gordon

Support@Seestar

Gordon If you can, you send it over first and we'll take a look at it.

Gulyas K

Daemon42 So true! Most people do not realize, that 1,5x mosaic does not mean 1,5x area. Both sides of the field of view is 1,5 times bigger, therefore we are talking about 2,25x times bigger area! So a 19 minutes mosaic is actually a barely 8 minutes long full exposure.

Daemon42

Gulyas K "So a 19 minutes mosaic is actually a barely 8 minutes long full exposure."
It's not even that much. For 1.5x diagonal framing, at 19 minutes total exposure it's usually just barely visually finishing up the last corner on its first pass, with only 2 exposures (20 seconds) in that corner, and still needs to make more exposures centered on the edges of the frame itself to clean up those noisy corners. To actually complete the full single pass it'll take another several minutes.. say.. 25 total, give or take. If you jump back and forth between live view and the Sky Atlas you can see that it spends a fair bit of time taking exposures that are literally half outside the frame which means 1.5x is really more like 1.5x + .5 + .5 or 2.5x total. Given all the the time it takes to take two exposures, then move, and sometimes discard frames with star trails while it's recovering from gear lash, I've generally found I need around 3 real hours to get 3 full passes, with about 75 minutes of total exposure time. Better still if you can get it up to 90 or 100 minutes of exposure.

Gordon

Thank you. This is all very interesting. It seems that the new mosaic feature is just a poor solution for the small sensor in the unit. I knew the Seestar in its present iteration would not be a suitable replacement for a good astrophotographic setup, but I find it perfect for EAA. And that’s what drew me to the product in the 1st place. Gordon

satch984

Gordon you need patience if you want to use mosaic mode.
This is 16h imaging, 1,5x framing, 8h real exposure in 3 nights

Its very long process, but the result for 500$ gear is awesome

Gordon

Understood, but how do you continue the mosaic on multiple nights? Thanks. Gordon

satch984

Gordon

Only thing you have to do is reframe in the same way as before and wait that mosaic complete. At the end you can stack your 3-4 images of multiple nights with Siril.

marvindj

Or PixInsight....an example on how to do that can be found here:

https://www.youtube.com/watch?v=dNhAjZKHWJ8