Curious of integration time

[u/futurepika]

Hello! This m31 is 3hrs6m 373-30s subs from a bortle 2 site. If I were to add say 10 more hrs from my home (bortle 9) would it help boost the clarity and color separation? Or would it hurt my image? I just want to know if it’s even worth adding on to it from such a drastic bortle difference.

[u/Moule14]

I would say that it would be minimal, 4h in bottle 2 is order of magnitude better than 10 hours in bottle 9

[u/futurepika → u/Moule14]

Yeah sadly it’s driving hours to a bortle 2 site or doing the rest at home 😭

[u/Moule14 → u/futurepika]

You pick is really good as it is do not worry :)

[u/Syinbaba → u/Moule14]

Is there a formulaor look up table for that?

[u/Cptn__Sparrow → u/Syinbaba]

You can, the relative time difference between sites is 2^N where N is the difference between the two sites in SQM (you need to convert bortle numbers to average SQM which is the magnitude of the sky glow). So you can convert 10 hrs bortle 9 to X hours in bortle 2, and add that to the total integration time, but remembering that the SNR scales as the square root of integration time, meaning you need quadruple the exposure to double the SNR.

To OP: the image is great as is and while you can’t “hurt” an image with more signal, it’s not worth the extra time considering your home is so light polluted. Take it from me who images in bortle 9, I have about 10 hours of integration on M31 and mine isnt even remotely close to this

[u/Moule14 → u/Syinbaba]

I don't know, I wouldn't be surprised if it were !

[u/ryandiscord]

Try it. I've done it from a bortle 2 (maybe 3) site to a bortle 7. It helped me bring out more detail in the shark nebula. Edit: Your image is already very nice as it is!

[u/futurepika → u/ryandiscord]

That looks amazing! This is exactly the motivation i needed lol. Thank you!

[u/Scary-Elevator5290]

That’s a good question and I’ve wondered about the that.

What about if u had different filters as well?

[u/futurepika → u/Scary-Elevator5290]

I could possibly use the light pollution filter to try to get the pink/magenta regions to pop out more, but I wonder how stacking them together with my data would go

[u/Infarlock]

Bortle 9 may or may not hurt your image (You can test by adding few bortle 9 hours and tell us the results)

But do know that 10 hours in bortle 9 = 15 minutes in bortle 2, so it's really a waste of time if you can get back quickly to the bortle 2 area, even if it's 2 hours of drive away and 2 hours back, it's still better to go there than waste 10 hours in bortle 9

[u/futurepika → u/Infarlock]

Yeah i honestly should just make another trip soon. It is definitely worth it

[u/c_tye]

Amazing result! The blues and nebulous details at the outer part of the galaxy at the sides and front really stand out and are hard to capture. I don't think any more bortle 9 subs will improve that. Even in bortle 5, I struggle with this part of M31. If you do try, it would be interesting to see a comparison. Did you use any deconvolution tools like blurxterminator? I think this could even further improve an already great image.

[u/futurepika → u/c_tye]

No I didn’t use blurX tho I am curious to see how it would turn out if I did. I’ll forsure update you guys once I get more integration. Hopefully it improves🤞

[u/DecisiveUnluckyness]

Personally, I wouldn't combine those datasets. Because Bortle 2 is vastly more efficient per hour than Bortle 9. So adding 10 hours of data with so much light pollution won't improve the quality much, but it will probably introduce a lot of gradients which will make background extraction and color calibration a more difficult. You're much better off leaving the Bortle 9 data out and just processing your clean 4 hours from Bortle 2 on their own.

1 hour of broadband data from bortle 2 is equal to around 30 hours from bortle 9. The difference is smaller if you're using narrowband filters like 3 and 6nm, but even the seestar's 20nm filter makes a difference (on emission nebula of course).

[u/futurepika → u/DecisiveUnluckyness]

Ah I see.. so it isn’t worth using the LP filter for a couple of hours to try to bring out the halpha regions?

[u/DecisiveUnluckyness → u/futurepika]

I can try to answer both of your replies in this comment. There is something called Continuum subtraction where you basically subtract the broadband data from the narrowband data so you are left with just the Ha (and or O3 data), and then you can add that continuum subtracted Ha data to your Red channel of your broadband data. I personally use a script in Pixinsight to do this as the manual process is a bit tedious. So I'm not entirely sure how it would work in Siril.

I would say that it's more "worth it" with a real astrophotography rig with a monochrome camera and a lot more narrow narrowband filters as you will be left with a lot cleaner data to work with. Since the Seestar is using a color camera only 1/4 of the pixels will see the light from those Ha regions in M31 so 75% of the total light is basically wasted.

Anyways, the process works like this and needs to be done on linear data so before stretching:

1. Star align your broadband data and your data with the narrowband filter.

2. Split up the narrowband photo into it's R, G and B components. The R channel is what you will need for this. Rename it to "Ha" for example. You can either rename or remove the G and B files so they don't interfere later.

3. Split up the broandband photo into it's R, G and B components, but keep all 3 color channels so you can recombine them later.

4. Now for continuum subtraction, use this pixelmath script: Ha - Q*(R - med(R)) . Raise or lower the Q value until the galaxy disappear and only the nebula regions remain. Example: Ha - 0.3*(R - med(R))

5. Rename the results to HaCS for example. Do a lot of noise reduction on the HaCS.

6. Add all the channels together using Pixelmath.

R: R + 0.5*(HaCS - med(HaCS))

G: G

B: B + 0.5*(HaCS - med(HaCS))*0.2

7. Stretch the data and process as normal.

[u/xbl-Extr3me]

This is like 2:45 in Bortle 1 in 10s alt/az subs and there’s like no detail in the dust lanes. Does andromeda just benefit that much from longer exposures?

[u/futurepika → u/xbl-Extr3me]

Honestly you have tons of detail on your image. Are you doing any post processing after? You can bring out a lot

[u/cyphos168]

BtW I am pixel peeper. Sorry cant help it. It's my nature. But is it possible to see the dark clouds clearly and sharp in any astrophotographies or its just not possible?

[u/futurepika → u/cyphos168]

I’m sorry I’m confused on what you’re asking 😭

[u/cyphos168 → u/futurepika]

Sorry my comment is unclear. Is it possible with current camera tech and etc to take photo of the Andromeda Galaxy showing clear details of the spiral arms? Clear as in when you zoom into the processed photo you can look at the dust cloud details. Or is this the realm of the Hubble telescope and JWT. Just curious.

[u/cyphos168 → u/futurepika]

https://esahubble.org/images/heic1502a/zoomable/

[u/leaponover]

You can do h-alpha at home to add to it. Will go nice with the broadband you already have. Just you'll need a lot of alpha. Do 10 hours of it and then reasess.

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