"Lucky" imaging for galaxies - Forums

Topic starter

3 hours ago

I got a C8 Xlt and using the Celestron .63x reducer and 533mc pro. Exploring some ways that I can eek out a bit more sharpness from those fine dust lanes you see in the Whirlpool or m106 galaxies. Integration time is what I hear the most, but if my seeing is around 2” or worse (with some occasional 1” nights), I’m wondering how far that will take me in terms of resolving very fine structure. That said, I haven't even remotely put in those sort of dues yet where people put 20+ hours into a single subject. With my schedule and how many clear nights I get, those type of integration times will take a while, but looking forward to it.

Anyway, I started to do some research on lucky imaging for dso and was a little surprised that some people have had success with relatively short exposures, 2-30 seconds. The thought being, less exposure time, less tracking error, less blurring from atmosphere, and of course being able to cull bad frames, and possibly use planetary imaging software for more advanced lucky imaging stacking to pull out tighter edges

I’ve read other things like using filters like l extreme, tricks for managing thermal radiation from the ground, dew shields to increase contrast, etc.

My next step is to ensure my collimation is as good as possible so I got a red filter and going to give Metaguide a shot to see if I can do better than “the donut looks centered".

Any suggestions welcome! I should note i’m also using an auto focuser

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Tony Gondola

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2 hours ago

Although I wouldn’t call it true lucky imaging it is an approach if you want as much detail as possible in your images. First you have to have the right sampling. I would base that more on your hardware and optics rather than what your “average seeing” is supposed to be. For your setup I would not use the reducer but rather shoot at prime. That will put you right were you want to be for 3.7 micron pixels. Exposure times will range from a few seconds to as much as 15 or 30 sec. You’ll also want to pump up the gain to get the read noise down as low as possible. With a 533 that will be around 200 to 300 but keep an eye on your star cores as the trade off will be lower dynamic range.

With such short exposure times you are going to gather a lot of frames but that’s what you want. Also, you really want to look for those nights where the seeing is at least good for your area. Using a weather app like the clear sky chart or atmospheric will give you that data. You want to keep an eye on the position of the jet stream too Also avoid shooting at low elevations below 60 degrees. That means for an object transiting directly overhead you’ll get about 4 hours worth of data per night. Of course your focus and guiding will need to be spot on.

Once you have your data you’ll want to deeply cull your subs. There’s a lot of different ways to do that depending on your software. You want to cull based on FWHM. You might have average seeing for 2” but if you’re done everything else right there will be a number that were taken during those short spells when it calms down. It might take several nights to get enough good frames for a decent S/N. You can get improved results with this technique but don’t expect miracles as this isn’t really lucky imaging. Pick bright objects and get a lot of high quality data.

An easier road to improved detail would be to shoot at F/10 with normal sub exposure length, whatever that is for your skies. The trick is to stack two images from the same original data set. One including all usable frames for S/N and one deeply culled for the best resolution. You can then take the high frequency information from the deeply culled image and combine that with you high S/N image. Techniques for doing that will depend on your software.

All this is fun to play with and is worth doing, even if it’s just to find the limits for your hardware and location.

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Paul Campbell

Topic starter

2 hours ago

Tony Gondola · Jun 10, 2026, 03:20 AM
Although I wouldn’t call it true lucky imaging it is an approach if you want as much detail as possible in your images. First you have to have the right sampling. I would base that more on your hardware and optics rather than what your “average seeing” is supposed to be. For your setup I would not use the reducer but rather shoot at prime. That will put you right were you want to be for 3.7 micron pixels. Exposure times will range from a few seconds to as much as 15 or 30 sec. You’ll also want to pump up the gain to get the read noise down as low as possible. With a 533 that will be around 200 to 300 but keep an eye on your star cores as the trade off will be lower dynamic range.
With such short exposure times you are going to gather a lot of frames but that’s what you want. Also, you really want to look for those nights where the seeing is at least good for your area. Using a weather app like the clear sky chart or atmospheric will give you that data. You want to keep an eye on the position of the jet stream too Also avoid shooting at low elevations below 60 degrees. That means for an object transiting directly overhead you’ll get about 4 hours worth of data per night. Of course your focus and guiding will need to be spot on.
Once you have your data you’ll want to deeply cull your subs. There’s a lot of different ways to do that depending on your software. You want to cull based on FWHM. You might have average seeing for 2” but if you’re done everything else right there will be a number that were taken during those short spells when it calms down. It might take several nights to get enough good frames for a decent S/N. You can get improved results with this technique but don’t expect miracles as this isn’t really lucky imaging. Pick bright objects and get a lot of high quality data.
An easier road to improved detail would be to shoot at F/10 with normal sub exposure length, whatever that is for your skies. The trick is to stack two images from the same original data set. One including all usable frames for S/N and one deeply culled for the best resolution. You can then take the high frequency information from the deeply culled image and combine that with you high S/N image. Techniques for doing that will depend on your software.
All this is fun to play with and is worth doing, even if it’s just to find the limits for your hardware and location.

Good ideas all around, appreciate it! I’ve been very hesitant to shoot at f/10 due to my guiding numbers. I think the best I can do right now is around .75 to .85” with my eq-g, with occasional spikes up around .9 to 1”. I have had longer periods of around .6” guiding so i’m hopeful I can get it refined a bit more. I bought this mount used, and I love it, but I don’t know how much to expect from it. I’ve looked into getting belt mod kits but i’m a little worried it could make things worse.

All this said, I’m going to give it a shot, why not! I really like the idea of getting a high s/n image and a high frequency detail image and compositing them together. I had played around with using high pass filters and basically doing that with my current images, but the data is just not there.

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