alacant Posted December 14, 2021 Share Posted December 14, 2021 Hi everyone Yes, sorry. Another. Excuse: we wanted to see if our bashed around 72ed was up to the standard of the swan chocolate box we had last week. Apart from the rubbish focuser, I think it is. Colour. Not sure. This is what Siril's photo database made of it anyway. Thanks for looking. Any other dslr/72ed/m42 shots? 700d 72ed ISO800 siril 1.0.0 rc3 StarTools 1.8.522 23 Link to comment Share on other sites More sharing options...
alan potts Posted December 14, 2021 Share Posted December 14, 2021 A beautifully detailed capture, just feel the blue is a little too over saturated. Alan 1 Link to comment Share on other sites More sharing options...
Cozzy Posted December 14, 2021 Share Posted December 14, 2021 alacant A quick search for 'SW 72ED' in the imaging forum will bring up quite a few images of M42 and many others using the same or similar kit to yourself. HTH's Tim 1 1 Link to comment Share on other sites More sharing options...
AstroMuni Posted December 15, 2021 Share Posted December 15, 2021 Lovely shot @alacant There seem to be sort of halos around the brighter stars. No idea if there is a way to get rid/reduce this. 1 Link to comment Share on other sites More sharing options...
alacant Posted December 15, 2021 Author Share Posted December 15, 2021 1 hour ago, AstroMuni said: way to get rid Hi Thanks for your post. I don't know I'm afraid. I'm not sure what causes it. Anyone? Cheers Link to comment Share on other sites More sharing options...
Elp Posted December 15, 2021 Share Posted December 15, 2021 Are you using a filter? Link to comment Share on other sites More sharing options...
alacant Posted December 15, 2021 Author Share Posted December 15, 2021 6 minutes ago, Elp said: filter Hi No. It's just telescope - FF - camera. Link to comment Share on other sites More sharing options...
Elp Posted December 15, 2021 Share Posted December 15, 2021 (edited) If you look at the halos they're relative to the centre of the image, so it looks like it's something to do with the light path, could be due to the flattener. Do you adjust the backfocus from the rear of the flattener to the camera sensor with spacers? I ask as my 61 WO flattener has a backfocus of something like 55-70mm depending on what source image you reference, I thought the dslr would connect directly to the back of the flattener via Tring but the stars were bloated when I did this. Edited December 15, 2021 by Elp 1 Link to comment Share on other sites More sharing options...
powerlord Posted December 15, 2021 Share Posted December 15, 2021 Very nice. What's this photo database in siril u mention? Sounds interesting. 1 Link to comment Share on other sites More sharing options...
alacant Posted December 15, 2021 Author Share Posted December 15, 2021 28 minutes ago, Elp said: something like 55-70mm Thanks. I think you're right about the flattener. This is a ts-flat2 which I just measured at 132mm. The advertised distance for 400mm is 128mm. Gotta be worth a try at the latter distance. Link to comment Share on other sites More sharing options...
Sunshine Posted December 15, 2021 Share Posted December 15, 2021 Wonderful capture! 1 Link to comment Share on other sites More sharing options...
alacant Posted December 15, 2021 Author Share Posted December 15, 2021 15 minutes ago, powerlord said: database in siril Hi It's under Image Processing -> Colour Calibration -> Photometric colour calibration HTH 1 1 Link to comment Share on other sites More sharing options...
ONIKKINEN Posted December 15, 2021 Share Posted December 15, 2021 16 minutes ago, powerlord said: Very nice. What's this photo database in siril u mention? Sounds interesting. I would assume this refers to the Photometric color calibration tool in Siril. The actual photometric data comes from either NOMAD or APASS surveys i think. Link to comment Share on other sites More sharing options...
ONIKKINEN Posted December 15, 2021 Share Posted December 15, 2021 1 minute ago, alacant said: Hi It's under Image Processing -> Colour Calibration -> Photometric colour calibration HTH If you dont like the color calibration result, try ticking off Auto and set the catalogue limit mag to a higher value? This way more stars will be used, assuming suitable stars are found in the image. I try to look at my image and see at which magnitude (referring to stellarium) the stars are still well resolved and not that noisy and choose that. Usually with mine i end up using down to mag 16 or fainter. Sometimes there is a difference, sometimes not, but worth a shot. 2 Link to comment Share on other sites More sharing options...
alacant Posted December 15, 2021 Author Share Posted December 15, 2021 6 minutes ago, ONIKKINEN said: ticking off Auto and set the catalogue limit mag As I'm hopeless at colour anyway, it's a quick way to get an idea of what maybe correct. That way, so long as you adjust only the saturation, something reasonable emerges. The method breaks down though if you have removed chunks of the spectrum. Cheers Link to comment Share on other sites More sharing options...
ollypenrice Posted December 16, 2021 Share Posted December 16, 2021 It's not unusual for refractors to struggle with blue stars at the best of times. Also, any high haze will exacerbate the problem. However, the halos are in two forms, inner and outer, and the fact that they have hard edges argues against their arising from blue bloat. They are more likely to be from internal reflections when they have a hard edge, I'd say. Olly 1 Link to comment Share on other sites More sharing options...
kirkster501 Posted December 16, 2021 Share Posted December 16, 2021 A lovely picture! Well done. Yes, as Olly says, even high-end refractors can bloat the blue channel (including the luminance). Even my TEC and FSQ do a bit. 1 Link to comment Share on other sites More sharing options...
alacant Posted December 18, 2021 Author Share Posted December 18, 2021 On 16/12/2021 at 08:35, ollypenrice said: internal reflections Do you mean as in Newtonian Reflectors if e.g. you don't blacken the inside of the tube/focuser/spider? Link to comment Share on other sites More sharing options...
ollypenrice Posted December 18, 2021 Share Posted December 18, 2021 6 minutes ago, alacant said: Do you mean as in Newtonian Reflectors if e.g. you don't blacken the inside of the tube/focuser/spider? No, I was thinking more of reflections shuttling back and forth between glass surfaces in the imaging train of a refractor. So that might be flattener/filter/chip window etc. Sometimes generic flatteners as devils for this. Olly Link to comment Share on other sites More sharing options...
alacant Posted January 1, 2022 Author Share Posted January 1, 2022 (edited) Here we are with the TSFlat2 at 128mm and a UHC filter. Yeah, I know. I changed too many variables [1], but it looks like the halos seemr more under control. [1] I expected the filter to introduce more -or larger- reflections. Edited January 2, 2022 by alacant gramática Link to comment Share on other sites More sharing options...
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