paul Posted May 13, 2021 Share Posted May 13, 2021 This is the result of just over an hour of LRGB out 3 hrs of so-so subs. Very hazy conditions and some weird tracking issues took the rest. I tried for some Ha on the second night but chickened out with the forecast changing by the minute. This is 50% downsize. Scope: 250mm OO, Camera ASI1600mm. 4 Quote Link to comment Share on other sites More sharing options...
paul Posted May 13, 2021 Author Share Posted May 13, 2021 With the bigger scope I seem to be clipping the brighter stars too easily, I need to think about halving the exposures and doubling up. Oh for a few extra bits😉. Quote Link to comment Share on other sites More sharing options...
Bob-c Posted May 13, 2021 Share Posted May 13, 2021 A nice image Paul, the dust lanes stands out well. Bob. 1 Quote Link to comment Share on other sites More sharing options...
AstronomyUkraine Posted May 13, 2021 Share Posted May 13, 2021 1 hour ago, paul said: This is the result of just over an hour of LRGB out 3 hrs of so-so subs. Very hazy conditions and some weird tracking issues took the rest. I tried for some Ha on the second night but chickened out with the forecast changing by the minute. This is 50% downsize. Scope: 250mm OO, Camera ASI1600mm. The image looks fine, with some great detail in the dust lanes. I don't know what your sky pollution is like, but I never take longer than 2 minute exposures with RGB and 1 minute with Lum with my 1600. I live in a Bortle 4 area, and shoot at gain of 75 and an offset of 15. My scope is a 120mm refractor. With that light bucket of yours, you can easily lower the exposures times. Quote Link to comment Share on other sites More sharing options...
paul Posted May 14, 2021 Author Share Posted May 14, 2021 11 hours ago, AstronomyUkraine said: The image looks fine, with some great detail in the dust lanes. I don't know what your sky pollution is like, but I never take longer than 2 minute exposures with RGB and 1 minute with Lum with my 1600. I live in a Bortle 4 area, and shoot at gain of 75 and an offset of 15. My scope is a 120mm refractor. With that light bucket of yours, you can easily lower the exposures times. Thanks 🙂. It was L:60s, RGB: 120s which has worked really well for the 150mm. (If I try narrow band its been 300s). I'm still new to the 1600 and haven't messed with the gain so default 139 and 50 offset. Its something I need to research - if it gives more dynamic range then I'm interested but otherwise it sounds like potentially making S/N worse. I heard that the offset is locked at 50 in the ZWO driver so had not even considered that. I think I'll try L:30, RGB: 60. I like to loop the sequence so I always have a set of LRGB but if the sub is too short that's a lot of filter switching and wasted time and I worry I'll age the filter wheel prematurely! So I'll probably try a sequence like LLL,RRR,GGG,BBB looped but that is more than a simple sequence. Quote Link to comment Share on other sites More sharing options...
peter shah Posted May 14, 2021 Share Posted May 14, 2021 a great shot....pretty deep too 1 Quote Link to comment Share on other sites More sharing options...
AstronomyUkraine Posted May 14, 2021 Share Posted May 14, 2021 23 minutes ago, paul said: Thanks 🙂. It was L:60s, RGB: 120s which has worked really well for the 150mm. (If I try narrow band its been 300s). I'm still new to the 1600 and haven't messed with the gain so default 139 and 50 offset. Its something I need to research - if it gives more dynamic range then I'm interested but otherwise it sounds like potentially making S/N worse. I heard that the offset is locked at 50 in the ZWO driver so had not even considered that. The gain and offset are not locked in the 1600. ZWO for some reason changed unity gain from a gain of 139 and offset of 21, to a gain of 139 and an offset of 50. I have tried the new unity setting, but reverted back to the old settings. The default setting for high dynamic range is a gain of 0 and an offset of 50 You can make your own custom settings quite easily in the camera driver. As you see from the image below, I have two custom settings. To make a custom setting, just click the edit button, and fill in the respective rows with a name for your setting, followed by the gain and offset value. My advice would be to experiment until you find a combination that works. I would definitely lower the gain for broadband imaging and choose unity gain for narrowband. 1 Quote Link to comment Share on other sites More sharing options...
MarkAR Posted May 14, 2021 Share Posted May 14, 2021 Lovely image Paul, nice detail. 1 Quote Link to comment Share on other sites More sharing options...
Carastro Posted May 15, 2021 Share Posted May 15, 2021 Pretty good result for only 1 hour. Presume you had to throw all the others away. Carole 1 Quote Link to comment Share on other sites More sharing options...
Greg M Posted May 16, 2021 Share Posted May 16, 2021 Mighty fine for only one hour of data. I can only imagine how great it would have been with three hours had you not had tracking issues. 1 Quote Link to comment Share on other sites More sharing options...
paul Posted May 16, 2021 Author Share Posted May 16, 2021 (edited) 19 hours ago, Carastro said: Pretty good result for only 1 hour. Presume you had to throw all the others away. Carole I did a simple stack in PI and there was very good contrast but the stars were twice the size and very obviously tear drop shaped. The worst images came in the second half with a strange ghosting. I'm not sure that it was tracking and PHD2 looked good and it impacted all the frames to some extent, it may have been droplets of condensation on the CC which is now more closer to the secondary or some diffraction through a tree. Here is a sample (it was getting light then too). The diffraction spike tells me I didn't lose focus and the second night the issue wasn't there so its not likely to be collimation. Edited May 16, 2021 by paul Quote Link to comment Share on other sites More sharing options...
paul Posted May 16, 2021 Author Share Posted May 16, 2021 10 hours ago, Greg M said: Mighty fine for only one hour of data. I can only imagine how great it would have been with three hours had you not had tracking issues. I am happy with the results all things considered, I like to grumble 😉. I worked hard to iron out my process so its annoying when there are things I don't yet understand getting in the way. 1 Quote Link to comment Share on other sites More sharing options...
AstronomyUkraine Posted May 16, 2021 Share Posted May 16, 2021 4 hours ago, paul said: I did a simple stack in PI and there was very good contrast but the stars were twice the size and very obviously tear drop shaped. The worst images came in the second half with a strange ghosting. I'm not sure that it was tracking and PHD2 looked good and it impacted all the frames to some extent, it may have been droplets of condensation on the CC which is now more closer to the secondary or some diffraction through a tree. Here is a sample (it was getting light then too). The diffraction spike tells me I didn't lose focus and the second night the issue wasn't there so its not likely to be collimation. That looks almost like an alignment issue. I have had similar myself when I have overlooked an image with star trails. Once the culprit was deleted then restacked, the alignment was perfect. Quote Link to comment Share on other sites More sharing options...
paul Posted May 18, 2021 Author Share Posted May 18, 2021 On 5/16/2021 at 7:24 PM, AstronomyUkraine said: That looks almost like an alignment issue. I have had similar myself when I have overlooked an image with star trails. Once the culprit was deleted then restacked, the alignment was perfect. I would agree but its in every single frame after about 2hrs, that's puzzling. Its why I suspect condensation or some diffraction effect. I have seen a similar effect when the view passes through a tree branch. I'm considering making a dew heater for the CC that I can fit on the inside of the scope to keep dew off the glass element. I have some resistance wire to experiment with. Quote Link to comment Share on other sites More sharing options...
AstronomyUkraine Posted May 18, 2021 Share Posted May 18, 2021 1 hour ago, paul said: I would agree but its in every single frame after about 2hrs, that's puzzling. Its why I suspect condensation or some diffraction effect. I have seen a similar effect when the view passes through a tree branch. I'm considering making a dew heater for the CC that I can fit on the inside of the scope to keep dew off the glass element. I have some resistance wire to experiment with. For less than £19 you can purchase a ready made solution from ZWO. It is called an anti dew heater, and fits ZWO cameras. I have one myself, they work fine. https://www.rothervalleyoptics.co.uk/zwo-anti-dew-heater-strip-for-zwo-asi-cooled-cameras.html Quote Link to comment Share on other sites More sharing options...
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