Adreneline

Hi. Even after 10 months I am still at the bottom of every learning curve, however, I also use SG Pro and have found the add-on to allow plate solving very good for repeatedly going back to a target. In terms of combining images I have used PixInsight (which I decided was a worthwhile investment compared with what I'd spent on hardware) but not found it particularly easy for combining images and not always been that pleased with the end result, although that is probably down to my novice skills at PI. In all other respects I have been very pleased with PI and obtained far better processing results than I ever did with PS. I have recently started using Registar and so far I have been very impressed with the way it can register and combine images taken on different nights, using different camera systems (414ex osc, 428ex mono and even a 70D dslr), and produce a very good end result which I have been able to further process in PI and obtain a positive end result. I am hoping to get even better results once we are finally blessed with some nice long, clear and very dark nights. I've nearly forgotten what one of those is! You know I never noticed the cloudy nights before I took up AP - I must have constantly had my head in the clouds.

I am sure to be corrected on this but, assuming I am making a one way trip to PS, I Resample the image to 300 dpi and then perform ICCProfileTransformation with Target Profile set to sRGB IEC61966-2.1 and Rendering Intent set to Perceptual (photographic images); I also check the Black Point compensation. I also then save as a 16 bit TIF. There are others with far more experience of PI than me so I am sure more advice will be forthcoming. Good Luck! Adrian

I used LHE (carefully) and combined the result with an image of M101 from earlier in the year. A bit more tweaking in PI and this is the end result: Compared with the original without added luminance: Well I don't think it is any worse but I'm not sure it is a lot better! Learnt lots though! Many thanks. Adrian

Hi Olly, I think our post crossed in system. No I've not tried LHE - thank you - something else to try. One thing I am discovering is I need a much more disciplined approach to saving and naming files. Never mind being "Lost in Space", I'm getting lost in my own subdirectories. Thanks again. Adrian

I tried the masked stretch but not sure the end result is as good as repeated HT stretches - unless I'm doing something wrong. Thanks Olly. In both cases I set the background at 20 in PS in an attempt to improve the contrast. Thanks again for all your advice. Adrian

Thank you Wim. Well I have had a go and this is the end result - or maybe not depending on the feedback I get In the end I used PI and PS to set a black point - I went for 20 - hopefully I've not overdone it. Thanks again in anticipation of your comments. Adrian

Thank you Olly. I'll give it a go and post my end result for comment Adrian

Thank you Firas. Yes, it is really was taken with a Skywatcher 80 ED DS-Pro and an Atik 428ex mono. I carried out a minimal crop in PI just to get rid of the stacking artefacts around the edges. I've been using a 414ex and have attempted to image M101 many times over the last 10 months. I decided to liquidate some assests from a previous, long, long ago hobby and treated myself to a 428ex mono. I've only bought a luminance filter so far; I wanted to get some practice using the 428ex just to obtain luminance images. I know essentially what I am trying to achieve in processing luminance it's just I'm not sure what I am doing currently is best practice - if such a thing exists. Thank you for the comment Olly - I have tried processing in PS as well and created a mask so I could selectively stretch the galaxy. With regard to processing is it fair to say I can allow the background sky to be 'blacker' than I might wish to achieve with rgb? When using the image for a luminance layer is contrast the overarching requirement? Does it matter if the background is clipped if it is going to be used as a luminance layer? Thnak you again for your comments and advice. Adrian

I agree Wim - we have neither dark nights or good seeing. I should have said I was using a R/F so the focal length is 510mm Thanks again. Adrian

Thank you Wim. The seeing was not good - although it was better than it has been for some time. The guiding seems good to me from what I can see from the PHD graph, with Total RMS error of 0.81". I stopped taking subs because it was starting to get light again, in fact I should probably be more ruthless in excluding some taken at the beginning and end of the session. I wasn't expecting to get a great image; I am just keen to know if I should be doing something over and above what I am trying now. I appreciate your help and comments. Adrian

Thanks Wim. So far I've used DynamicCrop, DBE or ABE, DynamicPSF, Deconvolution and then used HT to stretch the image a number of times trying to ensure I don't clip the background. Adrian

Can someone please give me some guidance on processing a luminance stack in PixInsight. I've looked at a number of web resources and Keller's book but I'm still a bit confused about what I might expect to achieve - what should the end result look like. Apologies for this being M101 again and the quality of the image but it was high in the sky and convenient for a short night with non-optimal seeing. The image comprises 19x300s subs (you know I don't know why I didn't take 20 with my OCD and all that) which I've calibrated with 50 each dark, bias and flats, registered and stacked in PixInsight. I've used STF to pull the image from the background and then saved as a jpg so you can view the image. It's taken with an Atik428ex mono on a SW80ED DS-Pro + NEQ6-Pro using SGP and PHD - focussed as best I could recognising the seeing conditions. I think I am getting the hang of processing osc rgb images in PI but I'm not sure of the best approach with a luminance image and what I might expect to achieve. I've included the fit and xsif file if somone wouldn't mind having a go and showing me what is achievable and what I should typically aim for - and how! I am keen to try to get to grips with the mechanics before those long dark nights set in - whenever that might be! As ever many thanks in anticipation of any help/guidance/advice. Adrian P.S. ImageAnalysis gives me the following stats on the image: Is this good, bad or indifferent? What is 'good' and what is 'bad' or 'in need of improvement'? Thank you M101-luminance.fit M101-Luminance.xisf

Hi Billy. In answer to your first question I've attached the image with and without the flat - both processed in PI using exactly the same workflow. I've had numerous further attempts at producing flats and they always come out the same. The feedback I had from a CN forum was "if that the way they are then that's they way they need to be to correct errors in the optics"; it's all a function of sensor size and optics train. The differences are pretty subtle I feel.

Thank you for all the advice and the time taken to provide me with some potential ways forward. At the end of the day if I am going to use flats in the calibration process I may as well do my utmost to get them right! The R/F has a 2" matt black adapter nose-piece courtesy of FLO which holds the 2" IR/UV IDAS filter in the drawtube. Downstream of the R/F is a Baader Varilock which has a matt black internal surface but whether it is matt black enough remains to be seen. The VariLock attaches directly to the 414ex camera body; the 414ex nose has been removed. I have to say it's not obvious where the problem may be as I know the inside of the drawtube is matt black. I will give the sky flats a go as well and see how I get on. Many thanks again for all the helpful comments. Adrian

Hi Billy. Attached is the configuration I use for flats - iPad running a 'light-pad' app sitting on the end of the OTA. I adjust the exposure in SGP to get a mean of around 30000. I tape some thick black plastic rubble sack around the drawtube (but not the focusser) and fire off 50 flats at a temp of -10deg - typical exposure time per flat is around 0.18 s. I assumed taking them in the daylight was acceptable as there is plenty of advice saying to use the dawn sky, etc. for illumination through a white cloth. I've just repeated the process and obtained the attached flat - with contour from PI. Any advice would be most welcome. I think I might be heading off to B&Q! AP is a tricky old business!