Rodd Posted June 4, 2019 Share Posted June 4, 2019 I had forgotten what a decent night was like. I was actually able to follow the convolutions of Draco, which I typically can not do. I could see the trapezoidal head and all. That might seem banal to most....but to me it was a first at my imaging location. I decided to pursue M13 due to its position, and the fact that only 3 channels would really be needed (I am betting Lum will not be necessary....but please let me know if you disagree). I gave up on NGC 7425 at last--poor conditions, bad calibrations, weird guiding issues and now only about an hour per night before it hits the trees. I am not particularity happy about it, but M13 helps. This is only the red channel. I am posting because it will no doubt be many weeks before I finish this beauty--maybe more, depending on the clouds and Moon. I was hesitant to take 300 sec subs, fearing that I would burn the core. So far so good, but in the end shorter subs may be needed in the core...we'll see. This image has been very lightly processed..cropped, DBE, and stretched in a conservative manner (still might be heavy handed though). There is a bit of graininess to the background upon full resolution--probably need more data...then again, this is my nemesis that may very well have nothing to do with noise. Software binning 2x2 may help--but the FWHM values were consistently low 2's, so I kept it at 1x1. Not sure why the bright stars are....aura'd....I don' think it was hazy and focus was good. Anyway....suggestions welcome. TOA 130 with ASI 1600 Red: 25 300 sec Link to comment Share on other sites More sharing options...
kirkster501 Posted June 4, 2019 Share Posted June 4, 2019 Very nice, M13 and M15 amongst my favourites. This is a much harder target than most realise IMO. In your version you have lovely small stars in there so you must have had a very steady night and good tracking and guiding. You've lost control of the bright stars at 5 and 10 O'Clock though. What happened? Link to comment Share on other sites More sharing options...
david_taurus83 Posted June 4, 2019 Share Posted June 4, 2019 2 hours ago, kirkster501 said: You've lost control of the bright stars at 5 and 10 O'Clock though. What happened? It's the microlensing effect inherent with the Panasonic sensor on the ASI1600. It's worse on some optical configurations and not so bad on others. Link to comment Share on other sites More sharing options...
Rodd Posted June 5, 2019 Author Share Posted June 5, 2019 6 hours ago, david_taurus83 said: It's the microlensing effect inherent with the Panasonic sensor on the ASI1600. It's worse on some optical configurations and not so bad on others. I suppose that's good news. It could be worse. The TOA could be defective😱 Link to comment Share on other sites More sharing options...
david_taurus83 Posted June 5, 2019 Share Posted June 5, 2019 It could indeed be a lot worse. Link to comment Share on other sites More sharing options...
Rodd Posted June 5, 2019 Author Share Posted June 5, 2019 4 hours ago, david_taurus83 said: It could indeed be a lot worse. That doesn't look like microlensing. What are the concentric rings? Rodd Link to comment Share on other sites More sharing options...
JamesF Posted June 5, 2019 Share Posted June 5, 2019 2 hours ago, Rodd said: That doesn't look like microlensing. What are the concentric rings? Rodd Diffraction rings from the star? James Link to comment Share on other sites More sharing options...
Captain Scarlet Posted June 5, 2019 Share Posted June 5, 2019 looks like a Moire effect you get when photographing a PC screen at critical focus Link to comment Share on other sites More sharing options...
JamesF Posted June 5, 2019 Share Posted June 5, 2019 There's some fascinating explanation of this effect in this thead: https://www.cloudynights.com/topic/635937-microlens-diffraction-effect-explained/ James Link to comment Share on other sites More sharing options...
JamesF Posted June 5, 2019 Share Posted June 5, 2019 Actually, looking at the two threads I think that's where david_taurus83's image came from. James Link to comment Share on other sites More sharing options...
david_taurus83 Posted June 5, 2019 Share Posted June 5, 2019 Apologies if links to CN are considered taboo!https://www.cloudynights.com/topic/635937-microlens-diffraction-effect-explained/ Link to comment Share on other sites More sharing options...
david_taurus83 Posted June 5, 2019 Share Posted June 5, 2019 Just now, JamesF said: Actually, looking at the two threads I think that's where david_taurus83's image came from. James Snap! Link to comment Share on other sites More sharing options...
Rodd Posted June 5, 2019 Author Share Posted June 5, 2019 53 minutes ago, JamesF said: There's some fascinating explanation of this effect in this thead: https://www.cloudynights.com/topic/635937-microlens-diffraction-effect-explained/ James If it is the Talbot effect--why does it not appear for all bright stars--There was reference to it only happening sometimes. Also--this would mean that its camera independent and should happen with all cameras. I never noticed it on the STT-8300 and that has micro lenses as well. On the STT-8300, micro lenses create miniature diffraction spikes pseudo neutonianism or RCism. an argument can be made that even large diffraction spikes are ok, and miniature ones even more OK. But these lobes? They ruin images. Maybe their is a defect in the system. Nothing would skock me less. Rodd Link to comment Share on other sites More sharing options...
JamesF Posted June 5, 2019 Share Posted June 5, 2019 I believe the idea that it is the Talbot effect is discounted in the later postings in that thread. James Link to comment Share on other sites More sharing options...
JamesF Posted June 5, 2019 Share Posted June 5, 2019 Oh, and near the end of the thread there's also a posting from someone who claims to have seen it on the 8300 and 16200 sensors as well as with DSLRs. James Link to comment Share on other sites More sharing options...
Rodd Posted June 5, 2019 Author Share Posted June 5, 2019 18 minutes ago, JamesF said: Oh, and near the end of the thread there's also a posting from someone who claims to have seen it on the 8300 and 16200 sensors as well as with DSLRs. James I think the small diffraction spikes seen with sensors that use microlensing are caused by a different thing than the effect seen on the two bright stars in the image above. Rodd Link to comment Share on other sites More sharing options...
Rodd Posted June 8, 2019 Author Share Posted June 8, 2019 I had nothing else to do--so I fiddled. Brought out more of the core. Background needs work--but I am hoping that will work itself out by the time I get to RGB. Link to comment Share on other sites More sharing options...
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