One nice thing about sticking with one filter for a while: doing L and B when highest in the sky, R at lowest, and G intermediate, we can reduce the impact of scattering.
Very good advice! I used to do that in the simple sequencer back in NINA 1.10, where there was the option to do just that, but I don't remember how I dealt with dither. I can say that even with a cheap focuser (ZWO EAF) that has quite some backlash, with proper backlash overshoot compensation and filter offsets, it works shockingly well. If I know that the night is going to be completely clear, I do it the traditional way (and I can also choose which filter will be imaging close to horizon, which close to Meridian, etc. to optimize)
Absolutely Cuiv! When the weather is looking iffy I go this route so I don't miss a whole channel, but on long clear nights old methods creep back in. EAF's are getting much better these days with many "zero backlash" focusers available now too.
I've thought about this since I stated using NINA. The problem is the offsets in the filters will only work if you can get the backlash in the focuser exactly right, because each time it moves the position would end up different. I'd rather do it the way in the video but for now I just do ha, sII, OIII, one after the other. It's too bad because it takes me about 2 months to do one target because weather, and day off have to be perfectly aligned and that almost never happens.
You've got a good point abut backlash, but I've seen a couple of tricks that might help. First, NINA has an "overshoot" method of backlash that works well for me. As long as you enter a step value larger than the backlash and in the correct direction, it should take care of the issue. Second, choose the order you shoot your filters so that you move in one direction only and don't have to adjust for backlash. For example, I have backlash if I move the focuser out, so I shoot my filters in an order where the focuser moves inward until the end of the loop. In my case, I image in B, G, L, R order. The focuser doesn't have to adjust for backlash until it goes back to blue. I hope that helps.
Hello, nice tips, thanks. but what about, instead of RGBRGBRGB, doing RGBBGRRGBBGR ? you save up some filter change time, right ? Only drawback is that you could only dither every 6 exposures. Added bonus is that going from R to B is probably longer than other changes (because those 2 filters are more distant in the wheel) doing RGBBGR you always go the the next filter.
You could definitely do RGBBGR style instead which would help with the filter movement as you mentioned. Just add another 2 lines (G & R) to the sequence & change the blue filter line to take 2 images. Leave the dither trigger at 3 and it would dither between the blue images too keeping you at one dither per RGB "round". Love this extra optimisation and I'll try it out my next clear night.
RoRo, thanks for your advise. This has been on my mind being in the UK and no one else I have seen has explained this method for mono. Funny seems obvious after your video... but I was stuck with the thought previously of combining different nights observations together... one night red one night blue, then green. Which having a portable set up is a bit complicated. Your procedure is a much better idea After your video, I'm going mono cheers.
Hi RoRo, been going through your videos for a few months now and am about to attempt my first imaging night ever 😅 I’m using monochrome which is what led me to this video. I will be using asiair plus to set up my imaging sequence would it be a similar interface? I haven’t actually used it yet. I really want to follow this process so at least I get something I can work with at the end of the night and practice processing. Also I have one more question about taking flats. You didn’t mention this my thoughts are after every filter you take a flat but I think I might be wrong 🤷♂️ can you take your flats at the end of the night and just change the amount of exposures per filter in the sequence?. Sorry for the long post but I’m trying to write down my plan from start to finish so I don’t miss anything. Any advice would be helpful thanks
Thank you for this nice video. I tried to test your suggestion, but i ran into an issue with NINA, where during rgb imaging when the filter changes for the next subframe, nina stops and resumes guiding during the filter change (which messes the guiding little bit). Is this normal ? I noticed that if i disable the setting "disable guiding during AF" that this is not happening. However a filter change, is not an AF event. Do you think this is a bug of NINA ? Have you seen this as well ?
Great video - thanks. You described my reluctance to move to mono exactly. Quick question. Is a single LRGB sequence say at 1 minute each equivalent or better in terms of light gathering, noise or quality to single OSC camera exposure for 1 minute ? If you tell me that the LRGB sequence gives the quality of 2 or 3 osc exposures the that would be a huge pro in terms of moving to LRGB ? Thoughts ?
Doing RGB you're losing 1/3 time with mono. When doing L, you're 2x better with mono roughly. For example, if you do 10h L and 6h RGB (16h total) you end up getting similar SNR as with 24h with color. You get better resolution and (arguably) better color information on top of that.
RoRo, I've thought about this in the past but never executed it because I wasn't sure I could trust the filter offsets well enough to be in critical focus. However, NINA's filter offset routine is getting really good and there are other methods such as overshoot that might work. I'll give it a try next time out.
Hi, but how about offsets and focuser backlash? Even though offsets should work, I find AF reassuring. Therefore I shoot in 10R10G10B and loop that with AF for each 10.
NINA has a built in backlash overshoot compensation that works really well to prevent these kinds of issues. You just need to change the backlash method from absolute to overshoot. I'd recommend giving it a try and see how it goes for you :)
With an color camera you are essentially using three cameras at once and the sensitivity per pixel is practically the same as mono. All you lose is some resolution that is probably made irrelevant by seeing conditions any way. Pop on a dual band filter and capture Ha and O in one take. S is practically irrelevant. People should stop imitating NASA publicity images. Take a look at the raw Hubble data sometime. Ugly! I keep considering mono but it just doesn't make sense. Imaging takes much longer in mono and more things can go wrong. And then there is the cost!
An OSC camera captures 25% Red, 50% Green & 25% Blue equivalent. In the same number of exposure hours, Mono captures: 25% Lum, 25% Red, 25% Green & 25% Blue. An image from mono camera with same total exposure time, is significantly better.
One nice thing about sticking with one filter for a while: doing L and B when highest in the sky, R at lowest, and G intermediate, we can reduce the impact of scattering.
Very good advice! I used to do that in the simple sequencer back in NINA 1.10, where there was the option to do just that, but I don't remember how I dealt with dither. I can say that even with a cheap focuser (ZWO EAF) that has quite some backlash, with proper backlash overshoot compensation and filter offsets, it works shockingly well. If I know that the night is going to be completely clear, I do it the traditional way (and I can also choose which filter will be imaging close to horizon, which close to Meridian, etc. to optimize)
Absolutely Cuiv! When the weather is looking iffy I go this route so I don't miss a whole channel, but on long clear nights old methods creep back in. EAF's are getting much better these days with many "zero backlash" focusers available now too.
Ro, you think out of the box…great video
Fantastic method. Makes perfect sense.
Great video Rohan!
I've thought about this since I stated using NINA. The problem is the offsets in the filters will only work if you can get the backlash in the focuser exactly right, because each time it moves the position would end up different. I'd rather do it the way in the video but for now I just do ha, sII, OIII, one after the other. It's too bad because it takes me about 2 months to do one target because weather, and day off have to be perfectly aligned and that almost never happens.
You've got a good point abut backlash, but I've seen a couple of tricks that might help.
First, NINA has an "overshoot" method of backlash that works well for me. As long as you enter a step value larger than the backlash and in the correct direction, it should take care of the issue. Second, choose the order you shoot your filters so that you move in one direction only and don't have to adjust for backlash. For example, I have backlash if I move the focuser out, so I shoot my filters in an order where the focuser moves inward until the end of the loop. In my case, I image in B, G, L, R order. The focuser doesn't have to adjust for backlash until it goes back to blue.
I hope that helps.
Hello, nice tips, thanks. but what about, instead of RGBRGBRGB, doing RGBBGRRGBBGR ? you save up some filter change time, right ? Only drawback is that you could only dither every 6 exposures. Added bonus is that going from R to B is probably longer than other changes (because those 2 filters are more distant in the wheel) doing RGBBGR you always go the the next filter.
You could definitely do RGBBGR style instead which would help with the filter movement as you mentioned. Just add another 2 lines (G & R) to the sequence & change the blue filter line to take 2 images. Leave the dither trigger at 3 and it would dither between the blue images too keeping you at one dither per RGB "round". Love this extra optimisation and I'll try it out my next clear night.
RoRo, thanks for your advise. This has been on my mind being in the UK and no one else I have seen has explained this method for mono. Funny seems obvious after your video... but I was stuck with the thought previously of combining different nights observations together... one night red one night blue, then green. Which having a portable set up is a bit complicated. Your procedure is a much better idea
After your video, I'm going mono cheers.
Glad it was helpful! All the best.
Very nice. Thanks.
Hi RoRo, been going through your videos for a few months now and am about to attempt my first imaging night ever 😅 I’m using monochrome which is what led me to this video. I will be using asiair plus to set up my imaging sequence would it be a similar interface? I haven’t actually used it yet. I really want to follow this process so at least I get something I can work with at the end of the night and practice processing. Also I have one more question about taking flats. You didn’t mention this my thoughts are after every filter you take a flat but I think I might be wrong 🤷♂️ can you take your flats at the end of the night and just change the amount of exposures per filter in the sequence?. Sorry for the long post but I’m trying to write down my plan from start to finish so I don’t miss anything. Any advice would be helpful thanks
Thank you for this nice video. I tried to test your suggestion, but i ran into an issue with NINA, where during rgb imaging when the filter changes for the next subframe, nina stops and resumes guiding during the filter change (which messes the guiding little bit). Is this normal ? I noticed that if i disable the setting "disable guiding during AF" that this is not happening. However a filter change, is not an AF event. Do you think this is a bug of NINA ? Have you seen this as well ?
Great video - thanks. You described my reluctance to move to mono exactly. Quick question. Is a single LRGB sequence say at 1 minute each equivalent or better in terms of light gathering, noise or quality to single OSC camera exposure for 1 minute ? If you tell me that the LRGB sequence gives the quality of 2 or 3 osc exposures the that would be a huge pro in terms of moving to LRGB ? Thoughts ?
Doing RGB you're losing 1/3 time with mono. When doing L, you're 2x better with mono roughly. For example, if you do 10h L and 6h RGB (16h total) you end up getting similar SNR as with 24h with color. You get better resolution and (arguably) better color information on top of that.
RoRo, I've thought about this in the past but never executed it because I wasn't sure I could trust the filter offsets well enough to be in critical focus. However, NINA's filter offset routine is getting really good and there are other methods such as overshoot that might work. I'll give it a try next time out.
Let me know how you go. NINA is definitely making a lot of new imaging "styles" possible, especially with all the new plugins too.
Using Antlia filters I've found that the focal difference is so small that it doesn't make sense to refocus after each.
Richard - Belgium - Great video RoRo..:-)...What about temperature change during the night...?
Hi, but how about offsets and focuser backlash? Even though offsets should work, I find AF reassuring. Therefore I shoot in 10R10G10B and loop that with AF for each 10.
NINA has a built in backlash overshoot compensation that works really well to prevent these kinds of issues. You just need to change the backlash method from absolute to overshoot. I'd recommend giving it a try and see how it goes for you :)
With an color camera you are essentially using three cameras at once and the sensitivity per pixel is practically the same as mono. All you lose is some resolution that is probably made irrelevant by seeing conditions any way. Pop on a dual band filter and capture Ha and O in one take. S is practically irrelevant. People should stop imitating NASA publicity images. Take a look at the raw Hubble data sometime. Ugly! I keep considering mono but it just doesn't make sense. Imaging takes much longer in mono and more things can go wrong. And then there is the cost!
An OSC camera captures 25% Red, 50% Green & 25% Blue equivalent. In the same number of exposure hours, Mono captures: 25% Lum, 25% Red, 25% Green & 25% Blue. An image from mono camera with same total exposure time, is significantly better.