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feilimb

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About feilimb

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    http://ronnach.wordpress.com

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    Angling, Software, Astronomy, Film
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    Cork, Ireland
  1. @Davesellars and @Louis D: many thanks for your valuable advice and apologies for my slow reply. Some really useful info there and it's actually making me question my OTA.. I actually do own a f/6.3 reducer bring the focal length down to ~1280mm but I always felt adding a focal reducer to the train would add it's own imperfections to the setup in terms of visual quality. Dave as you say, mayube the first thing to consider here is an upgrade of the diagonal, it is indeed the stock one that I still own and use. Louis, I thought the main differences between C8 and C8 EdgeHD scopes would be in terms of flattening of the field at the edges of the field of view, and more with respect to imaging? Is it possible that the collimation was just way out on the older 8" SCT that you mentioned when you tried it on Jupiter with the 10mm Delos eyepiece?
  2. Hi all, I have a venerable Celestar 8 which I use for a mix of visual and imaging. My visual use has been very on and off over the years and I feel I'm not getting the most of of the scope with the 2 eyepieces I own (both 1.25" diameter). I think both are Plossl design (Celestron branded eyepieces), one at 25mm (~81x) and the other at 12.5mm (~162x). I most like planetary observing with some deep sky observing too. I would like to upgrade and get something for visual use which will give much improved planetary views, with higher contrast, crisper views and ideally a wider eye relief. Can someone advise on whether I should go down the 2" eyepiece route, and if so what would be the way to achieve this onto the visual back of a C8? I presume a 2" diameter eyepiece is more of a joy to use because of the greater lens area and easier viewing - I would like to get my kids into the hobby a little too and the last time I tried they had trouble seeing anything in the small viewing hole of the 1.25" eyepieces. Any advice greatly appreciated!
  3. Thanks all, my next project after this thread is definitely to try to take a few flats even if it is just a trial run with a different camera orientation etc. With bias frames - can these be library type images that you can reuse again and again, or should they be taken at same temperature and conditions as light frames? I guess camera orientation and telescope connection is not important for bias frames as the exposure is so short?
  4. Thanks Gnomus - regarding taking flats later, in theory could one take the scope of the mount at the end of imaging session with camera still attached, and take flats eg. the next day (assuming camera position and focus are left untouched) ? I haven't dabbled in taking of flats yet so need to get up to speed on how to take them. I went back to DSS this evening and chose to stack with drizzle (x2) and kappa sigma clipping options. After using Harry's Astroshed newbie videos as a guide this is what I have now achieved after a couple of hours basic processing (still getting to grips with it all). I'm pretty happy with it although I know there is much to improve as I learn more.
  5. Thanks gnomus and uranium for the tips. I went back to look at the original stacked image and I see the splotches in that image too, so I think you hit the nail on the head regarding dead pixels and it showing the dithering which took place. As you say I should have taken bias and other calibration frames, but am still on the learning curve and was trying to stick to using just light frames for my first few efforts. Bias frames seem to be the easiest to obtain so I really should take some of these on my next session at the least. I'm going to go back to DSS again and try some other stacking options to see if I can get an image which doesn't have these artifacts at the end.
  6. Last night I managed to capture somewhere between 60 and 90 minutes of 4 minute subs on M101, at ISO800, F/6.3 on a Canon 450D hooked up to my C8 SCT. The quality of the subs seems decent, with some exceptions when cloud rolled in or when the guiding became poorer (I only noticed at the end of the session that there was heavy dew on the objective of my mini guide scope). I didn't capture any flats, darks or bias frames, although I did perform dithering between each sub. The subs didn't look amazing at first glance, but I tried stacking the best 70% in DSS at pretty much all the default settings, and then opening in my trial PixInsight and doing a crop and dynamic background extraction. That is pretty much where I am at, I haven't done anything else yet, but when the DBE finished processing I was delighted to see the image below jump out at me (with STF applied). I haven't gone any further with the image processing yet as I spotted a lot of strange small red, green and blue 'splotches' in the image. I am wondering if these are some kind of artifact which is a result of the stacking? Has anyone seen these before, or know how they might be eradicated before I go any further with processing? Any tips greatly appreciated! I can upload the subs to Dropbox if that is useful. Update: I have added a Dropbox link to the subs I captured here: https://www.dropbox.com/sh/ftnpfsfcqs7353x/AAA02RFxWhE3MTjoFiq_2Piua?dl=0
  7. M 51 - 61minutes with Celestron RASA

    That is a really stunning image, well done!
  8. Wow where did that colour come out of, my eyes were popping when I saw your posted version That's very pleasing to know that there is more colour information in there, hopefully bringing this out in processing will come with time for me. I must go back and take a look at the star shapes in each sub, to see if they changed over course of the session or not. I was using sct, so maybe there was some mirror flop.
  9. Thanks William, those resources look great and I may invest in a book if I stick with PI. Regards the clipping, yes I guess I made mistake of just wanting to see a black sky in the Histogram Transformation and probably clipped out too much. Another version is shown below without any dynamic noise reduction applied and less clipping, I picked up a satellite trail in one of the subs too I guess, but there's probably some more of the detail in the galaxy here. I'm not sure if the odd star shapes I've picked up are due to poor focus, poor guiding, or something else. Thanks again for all the advice and pointers so far, I'm looking forward to my next clear night here to try to build more data on M51 again.
  10. Thanks William, Doh, yes of course and this is what you suggested to me in your first post. I guess I was thinking I can do the DeBayer after stacking but it makes sense that this can't work, when there is twice the green data in each sub, and it won't be in consistent places across subs. I went back and stacked again, and played around with the result a bit in PixInsight, and am now getting the result below. Not much in the way of colour but there is a just hint of blue in the spiral arms. I think there is still something a bit off as when I opened the stacked result in PI, it still had a very obvious strong green cast, after applying a DBE this seemed to get resolved but I'm not sure if that was the correct way of removing it.
  11. So I ended up downloading the Trial license version of PixInsight. I tried stacking the images in DSS with the DeBayer option turned off, and then using the DeBayer process in PixInsight. A crash course in some videos on Harry's Astroshed later, and applying a Dynamic Crop, Dynamic Background Extraction, and Color Calibration I have a very odd looking image in terms of colour (see below): The main thing I can't figure out is what is going on with the colours... This is a first attempt at a very rough deep sky image, and I did not apply any flats, darks or bias, the stack was made from lights only, and was a total of 27 minutes data at F/6.3. Does anyone know where the green and magenta colours might be coming from in the image? I thought there may have been some pattern to the green but I could be wrong. Disregarding the weird colours, the actual galaxy has a bit of detail and I'm delighted to have produced something all the same Note: as far as I could see the green and magenta colours were apparent via a Screen Transfer Function even before the crop, DBE and color calibration so were not introduced during these processes. I can upload the stacked FITS if useful..
  12. IDAS LIGHT POLLUTION FILTER

    Hi Bob is this the type that fits inside a Canon Dslr body by any chance?
  13. Thanks Stuart some excellent examples there, can I ask what exposure time the single sub was at the bottom out of interest? I'm guessing at least 10 minutes, as the amount of detail for a single sub looks really fantastic.
  14. @Oddsocks Thank you for such a wonderful informative reply, I really appreciate all the info. That makes some more sense now - and is a relief that the image capture is functioning correctly. I thought I spotted BGGR listed somewhere alright and I wondered whether the 2 G's were somehow related to the green cast I was seeing in the KStars FITS viewer. I will try to make the adjustments and stacking settings you suggested this evening and see how it turns out. It will only be a 24-30 minutes combined image so am not expecting too much but will be nice to see if I have picked up any colour in M51's arms etc. Thanks again, I'll post back with results when I have them!
  15. So last night I was experimenting again with my setup, and my first time ever attempting to capture some deep sky image data with my DSLR. My setup is as follows: Celestron C8 with F6.3 focal reducer Canon 450D unmodified DSLR Orion 50mm Guidescope & QHY5LII guiding camera Ekos / Indi & KStars software for image acquisition and telescope control I succeeded in getting all the equipment setup, with fair polar alignment and half decent focus. I then started firing off a bunch of 3 minute light subs of M51 to see what would happen. In my software I had chosen FITS for the image capture format. To my amazement, even in the 3 minute subs I could actually see some hint of the galaxy and I'm happy enough with how the session went just from the point of view that I actually successfully captured some 3 minute shots which were not just goo. The focus and guiding may not have been spot on but that will come with time. However the thing that has me most confused is whether I actually have lost color information in the FITS files, they appear to be marked as 'Grayscale' in Deep Sky Stacker. In the FITS image viewer which comes with KStars, they appear green? Although a sample file is large (24MB), I have shared it here in Dropbox if anyone could help shed any light on this: https://www.dropbox.com/sh/ftnpfsfcqs7353x/AAA02RFxWhE3MTjoFiq_2Piua?dl=0 If I somehow captured the image in black and white, I'm not sure how that happened. Anyhow it was a pretty successful first run, even the autoguiding seemed to go pretty well after settling down for a while. The next massive stpe will be trying to figure out how to do some very basic image processing on a stack of 10 of these subs (I didn't take any flats or darks yet.. but did use Dither between shots).
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