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OSC during full moon (Target suggestions)


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Hey guys, hope you are all well.

At the moment, we apparently have two potential clear nights coming this Sunday and Monday...But of course these nights will be accompanied by a near full moon (typical!)

Haven't had much luck with the weather/forecasts for a while, so hoping it stays clear. I am eager to get out and try and image regardless of the moon as I have not been out properly for a while.

I was aiming to try and image the pleiades as it is quite bright and would hopefully stand up better than most other targets in heavy moonlight, but unfortunately the moon is positioned pretty close to it (see below)

1051343453_Screenshot(97).thumb.png.d946ca7141dca413efd3f16889778d28.png   

So I am weighing up my options and just thought to seek advice from others regarding possible projects over the two day period given the circumstances. Would love to try a 2-day project and combine data to break my current ~2 hour max integration time, given the circumstances. 

I will be shooting with a WO Z73 (430mm) + Modded 600D on a SGP, unguided (Limited to 60 second subs) from a bortle 3-4

I would love to try the iris nebula, shoot for 4+ hours as a target, but I am not sure just how worthwhile it will be with the moon so full. Seen others have success with OSC and short exposures during a bright moon, but not sure about it. It is further from the moon, but also a little low.

 

Any advice welcome, want to get a plan in place before travelling :) 

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Shoot between NW to NE, below zenith and you have good options with that moon. by that time, it will be less than full, which helps a lot. The open clusters are nice when they get a lot of integration time, more than most people usually do. NGC 7789 (Caroline's Rose) is a good choice. For something with dusty features, I would recommend the E nebula (B142/143). 

 

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On 20/11/2021 at 07:49, GalaxyGael said:

Shoot between NW to NE, below zenith and you have good options with that moon. by that time, it will be less than full, which helps a lot. The open clusters are nice when they get a lot of integration time, more than most people usually do. NGC 7789 (Caroline's Rose) is a good choice. For something with dusty features, I would recommend the E nebula (B142/143). 

 

Thank you for the advice GalaxyGael, will check out the suggestions now in telescopius :D 

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I have a second question regarding correct exposure during what will be ~95% moon tonight.

I was out a couple days ago where the moon was a similar brightness, I took a few shots in order to try and find the iris nebula and see the kind of impact the moon had.

Here is a single 60 second image opened up in PS, untouched;

426871137_Screenshot(98).thumb.png.fb124e5c4d63a171083b6ee6c638eddf.png

 

Does this look washed out? Debating if I should be doing either 30 or 60 seconds under these conditions.

Il be under the same sky again (Bortle 2-3, depending on which site used) with near enough the same moon.

 

Actually amazed I found the Iris nebula so quickly, but I will admit, I sat there staring at my 600D screen trying to decide if that was just a funky star or the core of the iris :D ..But the surrounding darkness gave it away.

6 minute (x6 60 seconds) of it with a little stretch and levels balance;

302294911_6minuestack.thumb.png.779a9b55363cfea4c0de9bccdfbc059c.png

738119180_Screenshot(101).thumb.png.9726b199f88a011c5c0d540d9c6cbe6a.png

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OSC cameras are a bit tricky during bright moons, especially if transparency isn't great.

Reflection nebulae like the iris nebula or pleiades are much better in darker skies.

I normally choose low northern targets or clusters on moony nights, or even just use the clear sky time to stress test the system, and check and adjust variables like polar alignment etc.

I dont care what the meteorological folk say, there has to be some relationship between full moons and clear skies, far too many to be coincidental. We even arrange outdoor events around full moons, with the greater probability of good weather!

Tim

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I imaged the Iris Nebula in early December 2020 with a modified  EOS 1300D from a Bortle 2 site (my back garden :D ) and it's not an easy target, even under the near perfect skies as I had for this one.

I tend to stick with brighter galaxies or nebula which are away from the Moon. Even then, for the nebula, my ISO was down to 800 and exposures of 60 to 120 seconds, it depended on the amount of moonlight in the area I was imaging. 

Now I use a dedicated OSC camera and have a Optolong L-eXtreme filter I use around the full Moon. This is only good for emission nebula though, so doesn't work on the likes of the Iris.

Here's the thread of my Iris Nebula from last year, so you can see what I did and what I got. I hope it helps. ;)

 

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3 hours ago, Iem1 said:

Does this look washed out? Debating if I should be doing either 30 or 60 seconds under these conditions.

Yes it looks washed out, but that is to be expected. The target does not need to be visible in a single sub, in fact i usually see nothing in a single frame without stretching and even with stretching its mostly just a jumbled mess of pixels. This is probably especially true for a dark nebula (such as the iris) because you're trying to capture nothingness, so seeing nothing is actually what you're after. What separates the dark cloud from the background is more exposure to brighten the part of the iris that is not darker than background sky. Either 30 or 60 second subs would probably work, but the 60s one looks just fine. 30s would probably work aswell, so up to you to figure out whether you want to deal with more short subs or less long subs that have an increased chance of being trailed = thrown out.

Your left side of the histogram is completely detached from the left end, so you are at least not underexposed. The right side has some possibly overexposed pixels, but looks like its just the starcores of the very brightest stars as the "line" of values in the histogram is broken up towards the right side.

B3-4 and full moon might still be better than severe lightpollution without a moon for some folks, so it will probably work out as long as the Moon is well clear of the target. Ideally the full Moon targets would be something like open clusters or globulars, which are just stars so no trouble in any conditions so in this case the Iris nebula is a difficult target.

As an example for the "single sub doesn't matter" point, here are 3 pics. The linear sub, stretched and (attempted) colour balanced and the final product.

2021-11-21T13_58_53.thumb.png.334e5ad8d31132ae687382a5bf6cf89a.png

2021-11-21T13_58_44.thumb.png.cc420e7e61d731e402a3c95100ed1b52.png

 

1673266522_NGC4236-5h34m.thumb.jpg.d3463b0f119b2ac5b26147f820965008.jpg

Just judging from the single frame, either untouched or stretched you could never say what it might look like. But take a hundred? Now you have a much better guess at what sort of total exposure time you're looking for to get a good result. (3rd pic is 668x30s).

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On 19/11/2021 at 22:12, Iem1 said:

Hey guys, hope you are all well.

At the moment, we apparently have two potential clear nights coming this Sunday and Monday...But of course these nights will be accompanied by a near full moon (typical!)

Haven't had much luck with the weather/forecasts for a while, so hoping it stays clear. I am eager to get out and try and image regardless of the moon as I have not been out properly for a while.

I was aiming to try and image the pleiades as it is quite bright and would hopefully stand up better than most other targets in heavy moonlight, but unfortunately the moon is positioned pretty close to it (see below)

1051343453_Screenshot(97).thumb.png.d946ca7141dca413efd3f16889778d28.png   

So I am weighing up my options and just thought to seek advice from others regarding possible projects over the two day period given the circumstances. Would love to try a 2-day project and combine data to break my current ~2 hour max integration time, given the circumstances. 

I will be shooting with a WO Z73 (430mm) + Modded 600D on a SGP, unguided (Limited to 60 second subs) from a bortle 3-4

I would love to try the iris nebula, shoot for 4+ hours as a target, but I am not sure just how worthwhile it will be with the moon so full. Seen others have success with OSC and short exposures during a bright moon, but not sure about it. It is further from the moon, but also a little low.

 

Any advice welcome, want to get a plan in place before travelling :) 

you haven't mentioned if you have any filters. I often image DSOs on full moon nights as I generally use an Optolong L Extreme filter (which basically makes the moon and streetlights irrelevant). It's only really useful for emission nebulae tho. I guess I tend to leave any broadband targets for moonless nights.

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2 hours ago, StuartT said:

you haven't mentioned if you have any filters. I often image DSOs on full moon nights as I generally use an Optolong L Extreme filter (which basically makes the moon and streetlights irrelevant). It's only really useful for emission nebulae tho. I guess I tend to leave any broadband targets for moonless nights.

Yep, really the only things you can do is shoot narrowband and also choose an emissions target in the opposite side of the sky to the moon to further reduce the effects.

Broadband (if you really have to) should just be a case of shortening the exposures the limit the damage and accepting that the result won't be as clean.

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Realistically NB only with the moon nearly full, and very high in the sky, almost as high as it gets. And then only H-alpha unless you have a target with strong [SII]. Don't even think about [OIII]. even 3nm isn't moon-proof.

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I appreciate that this is a controversial opinion, but I shoot both narrowband (using an L-eXtreme) and broadband (with no filter) regardless of what the Moon's doing. I just don't factor the Moon into the equation. It works out fine -- example photos here.

Full Moon, New Moon, if the skies are clear I'll be imaging whatever project I've got on the go. If the subframe quality is really bad, PixInsight's SubframeSelector will flag that and I'll remove it from the stack. But tools like DynamicBackgroundExtraction and NormalizeScaleGradient work really well at making even images with strong gradients usable. I expect other software packages can do similar. 

I do aim for long integration times mind you -- 20+ hours -- so won't ever be producing an image from just a night or two when a target was close to the Moon. 

I consider this comment to be gold quality, bearing in mind I'm under Bortle 8 skies:

5 hours ago, ONIKKINEN said:

B3-4 and full moon might still be better than severe lightpollution without a moon for some folks, so it will probably work out as long as the Moon is well clear of the target.

 

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Thank you for all the replies guys!

Decided to bite the bullet and take a stab at the iris nebula :D 

645303056_SiRilpng.thumb.png.83d01c14df6c7ade7c0f2a77ae3fb423.png

This about x270 30 second light frames (~2.5 hours), x50 Flats & x50 Bias. Taken with a WO Z73, Modded Canon 600D, all on a SGP, unguided, taken with a backdrop of a 94% moon no less!

Looking noisy and in need of a lot of work, I also tried manually dithered between each image, hopefully helped somewhat. Hoping to get another 2.5 hours tomorrow night to improve 

I haven't done any real processing yet, just chucked it into SiRiL and done a few auto bits and bobs as it is almost 4:30 am, but I couldn't wait to have a sneak peek! :D 

As always, The raw for tif if anyone wants to take a look;

Autosave.tif

 

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6 hours ago, Iem1 said:

Thank you for all the replies guys!

Decided to bite the bullet and take a stab at the iris nebula :D 

645303056_SiRilpng.thumb.png.83d01c14df6c7ade7c0f2a77ae3fb423.png

This about x270 30 second light frames (~2.5 hours), x50 Flats & x50 Bias. Taken with a WO Z73, Modded Canon 600D, all on a SGP, unguided, taken with a backdrop of a 94% moon no less!

Looking noisy and in need of a lot of work, I also tried manually dithered between each image, hopefully helped somewhat. Hoping to get another 2.5 hours tomorrow night to improve 

I haven't done any real processing yet, just chucked it into SiRiL and done a few auto bits and bobs as it is almost 4:30 am, but I couldn't wait to have a sneak peek! :D 

As always, The raw for tif if anyone wants to take a look;

Autosave.tif 168.61 MB · 2 downloads

 

Good work. 

Actually, I proved myself wrong last night! I took the filter off and shot 2.5 hours of M31 against a 96% moon. Looks fine I reckon. 

https://www.astrobin.com/ol8xo6/

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Nice Stuart! 

I was very suprised I managed to get a somewhat respectable result! 

My image is still very noisy though, not sure what I could have done to have improved it.

And I don't know why my stars are so chunky either. Maybe it's because the data is in there, and SiRL detects it and brings it out, but in order to do so it needs to stretch the hell out of it, blowing up the stars? 

I'm wondering if I get another 2.5 hours tonight, will it help, or make it worse? It will either add more data and perhaps SiRiL will have to stretch less to display data, cleaning it up some more...or will it just compound current issues? Hmm.

Having a play with it now, struggling to stretch myself and keep noise under control xD 

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7 minutes ago, Iem1 said:

Nice Stuart! 

I was very suprised I managed to get a somewhat respectable result! 

My image is still very noisy though, not sure what I could have done to have improved it.

And I don't know why my stars are so chunky either. Maybe it's because the data is in there, and SiRL detects it and brings it out, but in order to do so it needs to stretch the hell out of it, blowing up the stars? 

I'm wondering if I get another 2.5 hours tonight, will it help, or make it worse? It will either add more data and perhaps SiRiL will have to stretch less to display data, cleaning it up some more...or will it just compound current issues? Hmm.

Having a play with it now, struggling to stretch myself and keep noise under control xD 

Thanks.

I guess the noise is mostly down to the fact that you're not using a cooled camera (but I am no expert on that!)

As for your star sizes, not sure. I used Siril too and I tend to only use the autostretch (not the Asinh). I don't take any calibration frames - my image is lights only.

I'm sure adding more data will improve matters - it will bring the nebula out more anyway. How were you focusing with the 600D? Could that be it?

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1 hour ago, Iem1 said:

My image is still very noisy though, not sure what I could have done to have improved it.

There are three main things you can do to combat noise:

1. Longer total integration times. The more good quality data that goes into your stack, the better your signal-to-noise ratio will be. Here are some tips

2. Take calibration frames (Darks in particular). Having a cooled camera sensor does help to reduce noise a little, but the real benefit of a cooled camera is that you take set it to a particular specific temperature and then create a library of calibration frames that can be reused. Calibration frames are still important with a non-cooled camera like a DSLR, they just take a bit more effort to produce.

3. Noise reduction during post-processing. What you can use depends on the software that you're using. I find that Topaz DeNoise AI can work well, particularly on starless images (you then add the stars back in afterwards).

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1 hour ago, Lee_P said:

There are three main things you can do to combat noise:

1. Longer total integration times. The more good quality data that goes into your stack, the better your signal-to-noise ratio will be. Here are some tips

2. Take calibration frames (Darks in particular). Having a cooled camera sensor does help to reduce noise a little, but the real benefit of a cooled camera is that you take set it to a particular specific temperature and then create a library of calibration frames that can be reused. Calibration frames are still important with a non-cooled camera like a DSLR, they just take a bit more effort to produce.

3. Noise reduction during post-processing. What you can use depends on the software that you're using. I find that Topaz DeNoise AI can work well, particularly on starless images (you then add the stars back in afterwards).

Thank you lee, I am looking forward to hopefully doubling integration time tonight, providing the weather holds!

Be good to see the comparison.

3 hours ago, StuartT said:

Thanks.

I guess the noise is mostly down to the fact that you're not using a cooled camera (but I am no expert on that!)

As for your star sizes, not sure. I used Siril too and I tend to only use the autostretch (not the Asinh). I don't take any calibration frames - my image is lights only.

I'm sure adding more data will improve matters - it will bring the nebula out more anyway. How were you focusing with the 600D? Could that be it?

Yeah, true.

Though it felt pretty cool last night as it was between 1 and -1 degrees xD

It shouldnt be the focus, I used the B mask that came with the WO scope, although I am not a fan of it. It seems as though sides of the diffraction pattern are not symmetrical sometimes. But I focused and locked it down. 

About all I can muster with my measly processing skills, lost some of the dust and messed the stars up, but it was a bit of fun. 

1940972279_PSattempt(forSiRiL(bestversion).thumb.png.cd7bc574e3705a6461ff38557cceee39.png 

 

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1 hour ago, Iem1 said:

It shouldnt be the focus, I used the B mask that came with the WO scope, although I am not a fan of it. It seems as though sides of the diffraction pattern are not symmetrical sometimes. But I focused and locked it down. 

Ok, a Bhatinov mask should be giving you good focus if you're really zoomed in on the live view.

Get more data and post what you get . Not sure where you are, but it's looking like another crystal clear night in southern England...

Edited by StuartT
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I managed to get around another 1hr and 30 mins last night, the data seems good, stars no longer blown out as much. 

But it is a nightmare trying to stack the two sessions together! They do not align well at all, which i was expecting to some degree because of the manual dithering, but I wasn't expecting the result I got.

I did my best to mitigate all the damage and work with what the stacking would reasonably allow, so here is my current take on the Iris nebula.

~x450 30 second images, ~3 hrs 45 minutes of data over two nights, during a 94% moon and 88% moon respectively;

308604834_somewhatpassibleiris(png).thumb.png.cd52fdb5dba55000207eb4e3c3af5e74.png

it is quite heavily cropped, more than I would like. And stars are still large due to 1st nights data unfortunately

I tried quite a few methods of stacking in DSS (Standard, Mosaic and a custom rectangle), here is an example of what I was getting back;

Stacked and untocuhed.

Autosave002.tif

 

Not the greatest of outcomes, but it is a learning curve!

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Hi

Am completely with @Lee_P on going ahead, moon or no moon; gradients are easily removed these days.

The first set of frames. Some lovely detail in the nebula.

Keep adding those frames but be careful to keep the target centred. 

Cheers

1-w.thumb.jpg.3acb86de1593eda40688a6574ffb338e.jpg

 

 

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32 minutes ago, Iem1 said:

I managed to get around another 1hr and 30 mins last night, the data seems good, stars no longer blown out as much. 

 

Definitely an improvement. You're starting to get some more nebulosity in there

Have you tried using Siril for stacking and processing? I used to use DSS, then moved to Astro Pixel Processor. But now I use Siril and love it. It's got some nice tools and it's super fast on stacking

Edited by StuartT
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