alan4908 Posted January 10, 2018 Share Posted January 10, 2018 This is an LRGB image taken with my Esprit 150, it has a total integration time of just below 12 hours. The galaxy is surrounded by quite bright yellow/red stars, in an attempt to control these I decided to process the star-field separately from the main galaxy. I quite like the details and colours of the main galaxy and I was pleased to capture a little detail in the small background galaxies. Alan LIGHTS: L:21, R:17, G: 15, B: 17 x 600s. BIAS:100, DARKS:30, FLATS:40 all at -20C. Link to comment Share on other sites More sharing options...
SimonS Posted January 10, 2018 Share Posted January 10, 2018 Very nice image Link to comment Share on other sites More sharing options...
Tom OD Posted January 10, 2018 Share Posted January 10, 2018 very nice detail in the galaxy. Some of the stars look elongated though. You can fix this using the offset, and dark blends in PS Tom. Link to comment Share on other sites More sharing options...
alan4908 Posted January 10, 2018 Author Share Posted January 10, 2018 1 hour ago, SimonS said: Very nice image Thanks Simon. 53 minutes ago, Tom OD said: very nice detail in the galaxy. Some of the stars look elongated though. You can fix this using the offset, and dark blends in PS Tom. Thanks for the comment Tom. On the stars front - can you point out the stars which look elongated, since they all look round to me. Anyway, I checked with CCDInspector on both the final image and the LRGB stacks and they indicate very low aspect ratios (eg < 10). So I'm a bit puzzled. Alan Link to comment Share on other sites More sharing options...
ollypenrice Posted January 10, 2018 Share Posted January 10, 2018 I like the galaxy very much. I do see the elongation though. Its roughly aligned with the galaxy though slightly more vertical. Olly Link to comment Share on other sites More sharing options...
Tom OD Posted January 10, 2018 Share Posted January 10, 2018 4 minutes ago, alan4908 said: Thanks Simon. Thanks for the comment Tom. On the stars front - can you point out the stars which look elongated, since they all look round to me. Anyway, I checked with CCDInspector on both the final image and the LRGB stacks and they indicate very low aspect ratios (eg < 10). So I'm a bit puzzled. Alan Hi Alan, Most of them look elongated from the 11pm to 5pm direction. More of a teardrop look really. Easy to fix. Link to comment Share on other sites More sharing options...
alan4908 Posted January 10, 2018 Author Share Posted January 10, 2018 34 minutes ago, ollypenrice said: I like the galaxy very much. I do see the elongation though. Its roughly aligned with the galaxy though slightly more vertical. Ollu Thanks Olly - unfortunately, I still cannot see that any of the stars are non round...... 33 minutes ago, Tom OD said: Hi Alan, Most of them look elongated from the 11pm to 5pm direction. More of a teardrop look really. Easy to fix. Thanks Tom, but unfortunately, I still cannot see it. Anyway, I've taken a crop of the image, selected a few stars in MaximDL and they all are coming out OK. I've selected a random star (see below) which Maxim is telling me has a flatness of about 7%. To me this looks round - if I measure it on other stars they also appear round, so I'm really confused. Can you help by picking a star that you believe is a non round star ? Alan Link to comment Share on other sites More sharing options...
Paul73 Posted January 10, 2018 Share Posted January 10, 2018 Gosh. You chaps are harsh critics. ? I was busy being blown away with the amount of detail that you pulled out of that galaxy. The star field is a smidge on the colourful side for my taste. But that galaxy is outstanding!! Great work! Paul Link to comment Share on other sites More sharing options...
alan4908 Posted January 10, 2018 Author Share Posted January 10, 2018 1 hour ago, Paul73 said: Gosh. You chaps are harsh critics. ? I was busy being blown away with the amount of detail that you pulled out of that galaxy. The star field is a smidge on the colourful side for my taste. But that galaxy is outstanding!! Great work! Paul Thanks for the comment Paul. I was also pleased with the amount of detail in the galaxy. On the star front - I really don't mind criticism, unfortunately, when I can neither see the star elongation or detect it with two different programs I do find it confusing Link to comment Share on other sites More sharing options...
Tom OD Posted January 11, 2018 Share Posted January 11, 2018 16 hours ago, alan4908 said: Thanks Olly - unfortunately, I still cannot see that any of the stars are non round...... Thanks Tom, but unfortunately, I still cannot see it. Anyway, I've taken a crop of the image, selected a few stars in MaximDL and they all are coming out OK. I've selected a random star (see below) which Maxim is telling me has a flatness of about 7%. To me this looks round - if I measure it on other stars they also appear round, so I'm really confused. Can you help by picking a star that you believe is a non round star ? Alan Hi Alan, This is interesting. I' m looking at your image, on my phone, and then on a lower res screen at work. My laptop screen at home and my phone show the elongation, but the screen here at work does not really. I wonder is this a screen resolution issue then. My phone is good, and my laptop screen at home is very good. The star you have in Blue in the above screen shot is rectangular on the laptop, but squarer on this lower res screen. I hope this clears up any confusion. I dont like criticising images as its so difficult to create one, I ony pointed it out as its fixable and would make a great image, even better. Tom. Link to comment Share on other sites More sharing options...
Davey-T Posted January 11, 2018 Share Posted January 11, 2018 Curious effect, stars definitely look elongated 5/11 on my screen but the more you zoom in on them the rounder they look, at pixel level they look OK Super rendition of the galaxy Alan makes mine look pants Dave Stars at 1200% Link to comment Share on other sites More sharing options...
alan4908 Posted January 11, 2018 Author Share Posted January 11, 2018 26 minutes ago, Tom OD said: Hi Alan, This is interesting. I' m looking at your image, on my phone, and then on a lower res screen at work. My laptop screen at home and my phone show the elongation, but the screen here at work does not really. I wonder is this a screen resolution issue then. My phone is good, and my laptop screen at home is very good. The star you have in Blue in the above screen shot is rectangular on the laptop, but squarer on this lower res screen. I hope this clears up any confusion. I dont like criticising images as its so difficult to create one, I ony pointed it out as its fixable and would make a great image, even better. Tom. Tom Hmm yes, I agree that is interesting. I think I shall have a look at image on various PC's to see if I can see anything. By the way, please don't hold back criticizing my images in the future, I view it as an excellent feedback to improve ! Alan Link to comment Share on other sites More sharing options...
alan4908 Posted January 11, 2018 Author Share Posted January 11, 2018 9 minutes ago, Davey-T said: Curious effect, stars definitely look elongated 5/11 on my screen but the more you zoom in on them the rounder they look, at pixel level they look OK Super rendition of the galaxy Alan makes mine look pants Dave Hi Dave Thanks for this - this does seem very bizarre. What screen resolution you are viewing the image at ? Alan Link to comment Share on other sites More sharing options...
Tom OD Posted January 11, 2018 Share Posted January 11, 2018 4 minutes ago, alan4908 said: Tom Hmm yes, I agree that is interesting. I think I shall have a look at image on various PC's to see if I can see anything. By the way, please don't hold back criticizing my images in the future, I view it as an excellent feedback to improve ! Alan set the screen res to its highest setting too to see if its noticable Link to comment Share on other sites More sharing options...
Tom OD Posted January 11, 2018 Share Posted January 11, 2018 3 minutes ago, alan4908 said: Hi Dave Thanks for this - this does seem very bizarre. What screen resolution you are viewing the image at ? Alan i m 1920x1080 at home. only 1024x768 here at work Link to comment Share on other sites More sharing options...
Davey-T Posted January 11, 2018 Share Posted January 11, 2018 1920x1080 15" here, as Tom said you could mess with it in PS but may make it look worse when enlarged, worth experimenting though, nothing ventured nothing cocked up as they say Dave Link to comment Share on other sites More sharing options...
johnrt Posted January 11, 2018 Share Posted January 11, 2018 Cracking image Alan. Link to comment Share on other sites More sharing options...
alan4908 Posted January 11, 2018 Author Share Posted January 11, 2018 25 minutes ago, Tom OD said: i m 1920x1080 at home. only 1024x768 here at work 21 minutes ago, Davey-T said: 1920x1080 15" here, as Tom said you could mess with it in PS but may make it look worse when enlarged, worth experimenting though, nothing ventured nothing cocked up as they say Thanks for the information. My screen resolution is 2560 x 1080, I changed it to 1920 x 1080 but I still cannot see any star elongation. I then went around various PC's of various screen resolutions but still nothing was revealed. I then thought perhaps it's my eyesight, so to hopefully eliminate this aspect, I took a magnifying glass and started peering at the screen Unfortunately, I still cannot see anything odd. What I really don't understand, is related to the point made by Dave - how is it possible to see the elongation when zoomed out but not when zoomed in ? I've also found star elongation, more easy to see when zoomed in. Anyway, all very interesting, although I am puzzled. Alan Link to comment Share on other sites More sharing options...
alan4908 Posted January 11, 2018 Author Share Posted January 11, 2018 10 minutes ago, johnrt said: Cracking image Alan. Thanks John ! Link to comment Share on other sites More sharing options...
Davey-T Posted January 11, 2018 Share Posted January 11, 2018 Perhaps it's my eyesight Alan, maybe I need new specs, do you wear glasses ? Perhaps it's some sort of PNG conversion artefact that only shows up on some screens ? Dave Link to comment Share on other sites More sharing options...
ollypenrice Posted January 11, 2018 Share Posted January 11, 2018 18 hours ago, alan4908 said: Thanks Olly - unfortunately, I still cannot see that any of the stars are non round...... Thanks Tom, but unfortunately, I still cannot see it. Anyway, I've taken a crop of the image, selected a few stars in MaximDL and they all are coming out OK. I've selected a random star (see below) which Maxim is telling me has a flatness of about 7%. To me this looks round - if I measure it on other stars they also appear round, so I'm really confused. Can you help by picking a star that you believe is a non round star ? Alan This is weird, isn't it. The star you've ringed here looks, on my screen, very obviously elongated top to bottom. That is until I zoom right in on it as Dave suggested and, when pixelated it looks very much better. I'm mystified by this and have never come across it before. Could you post a link to one star - say that one - as a tiny square crop in TIFF or FITS. Just the star and a bit of space around it? Olly Link to comment Share on other sites More sharing options...
Tom OD Posted January 11, 2018 Share Posted January 11, 2018 Maybe there is some compression of the data when its attached in this forum. As Olly says, check out the original FIT or TIFF and enlarged, and normal, they should look the same. We'll figure this out I m sure. T. Link to comment Share on other sites More sharing options...
alan4908 Posted January 11, 2018 Author Share Posted January 11, 2018 1 hour ago, Davey-T said: Perhaps it's my eyesight Alan, maybe I need new specs, do you wear glasses ? Perhaps it's some sort of PNG conversion artefact that only shows up on some screens ? Dave Dave No, I don't wear glasses (hence my use of a magnifying glass to hopefully eliminate this aspect !). Personally, to solve the problem, I think we need to eliminate the human and screen resolution effects and just try to measure something with a software program. 7 minutes ago, ollypenrice said: This is weird, isn't it. The star you've ringed here looks, on my screen, very obviously elongated top to bottom. That is until I zoom right in on it as Dave suggested and, when pixelated it looks very much better. I'm mystified by this and have never come across it before. Could you post a link to one star - say that one - as a tiny square crop in TIFF or FITS. Just the star and a bit of space around it? Olly Hi Olly - yes, on the wierness scale I think this is pretty bizarre ! Here, is a TIFF crop of the star that I pointed MaximDL at: Star crop.tif Hope this works since I never attempted to upload a TIFF before. Alan Link to comment Share on other sites More sharing options...
Tom OD Posted January 11, 2018 Share Posted January 11, 2018 that star looks good on my work screen, but a bit rectangular on my phone. What adds to the effect, is that the halo on the star is rectangular, and has a smoother transition to the core of the star. So maybe thats what my eye is picking up, making it look overall that shape. Again though definite differenecs between the phone and monitor. Link to comment Share on other sites More sharing options...
alan4908 Posted January 11, 2018 Author Share Posted January 11, 2018 Hi Olly, Tom and Dave Since I have a suspicion it has something to do with the way I've processed this, I thought it would be useful to do some measurements at the early stages on the same star. So, firstly, an unprocessed and unstretched RGB TIFF image in MaximDL (showing the star roundness at about 4%) A crop of the unprocessed and unstretched RGB TIFF image (this is the same star as the crop of the fully processed result) RGB unprocessed star crop.tif MaximDL screenshot measurement - still unstretched but after applying DBE, Photometric Colour calibration and SNCR Green (showing star roundness at about 7%) Alan Link to comment Share on other sites More sharing options...
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