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Hi all Thanks for the nice comments - I am really enjoying this hobby, and desperate for more clear nights. Ashley's book is almost nightly reading for when I can't get out as it has so much information, yes about short exposure astrophotography, but also about general principles for the beginner. Very helpful, as have all the posts on this subject in SGL. Some technical info as requested: M42 Orion: shot at ISO 800; 20 x 20s + 50 x 30s Lights; 60 darks; 40 flats; 30 bias M101 Pinwheel: shot at ISO 400; 150 x 45s Lights; 40 darks; 40 flats; 40 bias (fighting against a full moon that night) M51 Whirlpool: shot at ISO 800; 60 x 30s Lights; 60 darks; 40 flats; 30 bias M104 Sombrero: shot at ISO 1600; 80 x 45s Lights; 30 darks; 40 flats; 30 bias All stacked in DSS using prerequisites for StarTools taking 80% of good images; Images then processed in StarTools. I have been experimenting with ISO (as you can tell!) as looking at info on my camera, it seems that ISO 400 (possibly 800) is best to use for maximum dynamic range. Still learning processing with StarTools - however these possibly look overprocessed? Thanks Andy
Hi Vern Congrats on your very first image - it is one you will always remember! What I am finding out is that using the scope and taking the image is only half the battle - learning how to stack and process the image is just as important if not more so. Working the software can really bring detail in an image you never thought was there. And it gives you something to do when the skies overhead are clouded over!. Learning new techniques and applying them to existing images is fun. Honest! Andy
Hi Mikey As I understand it, the standard approach is that fewer longer subs should always be better than a lot of shorter subs. For the same overall exposure time you can achieve the same SNR with a larger number of shorter subs, but you cannot improve the overall signal. So 3 x 25 min subs will have the same SNR as 300 x 15s subs, but the signal component of the 25 min subs will be 100 times higher than that of the 15s subs (using an example from Joseph Ashley's book). Stacking cannot overcome this, otherwise what would be the point of spending so much on precision equipment in order to take long exposure photos? However, light pollution is also a signal, so increasing exposure time also increases the signal from light pollution. Therefore if an image signal is lost to light pollution in your backyard, you will not be able to overcome this by taking longer exposures. Hence the draw of dark sky sights. So the real answer to your question is: It Depends! But mostly it depends on the level of light pollution where you are. Incidentally, in the discussion after the article you quoted, someone asks about the impact of light pollution filters, and the authors comment was that it 'shifts you toward dark sky conditions'. So I think a good experiment would be to see what the impact is with and without the filter for your conditions. Hope I am right - seems quite complex! Andy
Hi everyone I have been lurking on this site for a while, reading and assimilating all sorts of fascinating information about this wonderful hobby. Having acquired a secondhand Canon 50D camera in January, I thought I might be able to attach it to my scope for simple moon pictures etc. Then inspired by the amazing work of those contributing to the NO EQ DSO CHALLENGE thread, and by reading and digesting the book "Astrophotography on the go: Using Short Exposures with Light Mounts" by Joseph Ashley, I looked at DSO targets in the sky and was more than pleasantly surprised by what I was able to achieve with my limited mount and scope. I am trying out StarTools imaging software, and with BYEOS driving the camera using a mix of lights, darks, flats and bias, stacked in DSS have come up with the following pictures. Yes, the CA is bad - I know this can be tackled in software, but to me it is part of the picture as taken - it is a cheap entry level scope after all. Yes, the background is poor and grainy - I have lots to learn about image processing and hope to pick up many more hints and tips on this subject as we go on. Yes, I am using the wrong equipment to image on, but it works for me for now until the Missus allows me more funds to play with! However, they are my pictures taken with my equipment and I am pleased with the results so far (plenty of room for improvement though!). Question: No matter what I seem to try, I seem to always come up with a grainy background for my images - looks over processed. What is the most important factor at play here? Is it ISO level, poor SNR in the images, poor choice in targets to image, too aggressive with the imaging software, or something else? How do others manage grainy images? Would a light pollution filter help at all? Thanks for taking a look, and may dark skies be yours when you wish them! Andy