gthomas Posted June 20, 2012 Share Posted June 20, 2012 This Canon EF 200mm lens continues to impress me.One hour and fourty minutes of 2 and 3 minutes subs, stacked in DSS and some processing with pixInsight gave the following.The whole loop is nicely captured with plenty of detail and there are a shed load of stars which are nice and round right out to the corners even though the lens was only stopped to f3.5!Those stars are the problem though. I've not yet found a way to lift the nebula while keeping the background stars down. There are just so many that the loop gets kinda lost in there. Link to comment Share on other sites More sharing options...
Gina Posted June 20, 2012 Share Posted June 20, 2012 Great images I'm planning to do some wide-field stuff a bit later. I don't know PixInSight, I use PS sand in that I use Curves to bring up the fainter stuff while keeping the bright stars at bay. The technique is to lift the curve near the bottom (right hand) end but lower it near the upper (left hand) end. That lifts the brightness/contrast of the darker parts while lowering that of the lighter parts. Hope that makes sense. Link to comment Share on other sites More sharing options...
gthomas Posted June 20, 2012 Author Share Posted June 20, 2012 Thanks Gina,Do you mean like the usual S curve but upside down? Link to comment Share on other sites More sharing options...
Steve Ward Posted June 20, 2012 Share Posted June 20, 2012 Just been watching this , may be useful to you .http://www.astronomyshed.co.uk/forum/viewtopic.php?f=19&t=10593 Link to comment Share on other sites More sharing options...
gthomas Posted June 20, 2012 Author Share Posted June 20, 2012 Thanks for that Steve,I've tried star masks and, following Gina's idea, also some really bizarre curves but all to no avail. The problem is that the many small stars are at a signal level that is in the middle of the range covered by the nebula. Normally the problem is the other way around with the nebula far lower. Link to comment Share on other sites More sharing options...
Mark72 Posted June 20, 2012 Share Posted June 20, 2012 Glyn,This is not a great deal in PI. Create a star mask, apply to linear image, go to a stretched mask script, set to 100 iterations, watch the whole football game; when it's over, PI will be ready with a lot of nebula and suppressed stars.You can also reduce them with Morphological transformation. May look like this in the end - http://astrobin.com/2546/ Link to comment Share on other sites More sharing options...
gthomas Posted June 21, 2012 Author Share Posted June 21, 2012 Thank you Mark.I am fairly new to PixInsight and so was not familiar with those two functions. I've had a bit a play with them but with only limited success so far. I guess I need to do some more research and practice. Link to comment Share on other sites More sharing options...
gthomas Posted June 21, 2012 Author Share Posted June 21, 2012 Well after playing with various masks and transforms and on-line tutorials I think this is a lot better. Link to comment Share on other sites More sharing options...
Mark72 Posted June 21, 2012 Share Posted June 21, 2012 Yes, much better! Link to comment Share on other sites More sharing options...
gthomas Posted June 21, 2012 Author Share Posted June 21, 2012 Thanks for your help Mark Link to comment Share on other sites More sharing options...
Psychobilly Posted June 21, 2012 Share Posted June 21, 2012 Fits nicely in the FOV doesnt it...I'm using mine at f2.8 these days...http://stargazerslounge.com/index.php?/topic/150462-Canon-200/2.8L-can-you-get-decent-star-shapes-at-f2.8#entry1514700Peter... Link to comment Share on other sites More sharing options...
gthomas Posted June 21, 2012 Author Share Posted June 21, 2012 I find that at f2.8 I get some vignetting in the corners, but that can be corrected with Canon Photo Professional. At f3.5 or f4 I don't need to do that extra step plus, to be honest, I rather like the diffraction pattern on the brighter stars Link to comment Share on other sites More sharing options...
Psychobilly Posted June 21, 2012 Share Posted June 21, 2012 And i lke the fact you can grab those photons more quicklyFlats soon sort out any uneven illumination issues as well as sny dust bunnies etc...Pesonally i hate the multiline diffraction pattern and used to use front aperture rings to stop the lend down... but each to their own...Peter... Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.