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About Penguin

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    Star Forming

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    Gloucestershire, South-West England

    Oh yeah, it leaks, but only in a couple of places. I plan to fibreglass the roof soon in the hopes of fixing that.

    Here's mine, inspired by @lukebl's. Built over the summer by your's truly:
  3. Thank you so much guys, I am learning again! I took a load of bias frames at ISO 1600 (matching the lights/darks) and 400 (matching the flats) and re-stacked the HH image in DSS, which warned about differing ISO settings but seemed to apply them correctly. Then I applied Wim's workflow which was a slight re-ordering of steps and very different with DBE: I had previously been told to use 30 samples per row, which often seems to extract a very mottled background and I suspect may be a major cause of the problems I have been having. For colour calibration, I have never previously used the entire image for white reference, nor used structure detection. Here are the results, it's much cleaner but has also lost dome detail and definition, particularly noticeable in the Horsehead itself. Possibly some aspects of my previous processing were better than this attempt:
  4. Thanks guys, there's a lot to think about here, I shall take it away and cogitate.
  5. Hi Michael, that would be fabulous to save time or get an extra few lights. Can you explain how using bias as dark frames works? I thought a primary purpose of darks was to get the thermal signal with the light-frame exposure at the temperature the lights were taken at so that it could be subtracted from the lights. How do we achieve that without darks? Also, DSS complains if the darks are not the same exposure as the lights. Will it still work? Also, what do you mean by "you must Dither between shots"?
  6. Thanks Alan, there's some useful (and free!) things I can look into there. I have not tried TGVDenoise so I will investigate that. I normally do SCNR Green as the last step in my workflow but having just tried it on the Flame/Horsehead image, I can see that it is reducing the green so maybe I had missed that step. In terms of calibration frames I normally take 15 darks at the end of my session. It's a bit annoying having to spend another 1/2 hour taking 'blank' shots before packing up when its already 12:30am but I do understand the benefit. Is 15 frames/30 minutes long enough for the darks? I also take around 15 flats at the end of the session using this panel, which has several sheets of photo paper in front of it to allow the camera to take a long enough exposure that the LED refresh doesn't mess up the image, and is housed in a makeshift frame. I have also attached a single flat from the most recent session. Again, is 15 enough? Is there a better way to take them? Bias is easy and I gather I can prepare a set once and use them multiple times, I have just been lazy. I will prepare a set now and might try reprocessing a few of my existing images.
  7. Yes, I focus with a bahtinov mask, but I always end up with one of the axis spikes diverging into two, as can be seen with Alnitak on the Horsehead/Flame image and I don't understand what is causing that. I tend to focus at the scope since I don't have an auto-focuser so would have to keep going back and forth between scope and computer. Otherwise, I would post the focusing images for you.
  8. Hi Guys, just looking for some general help with improving my images I'm not sure what to concentrate on to get the best bang for my buck. Here are my latest couple of images: Both of these are taken with an unmodified Canon 450D through a Skywatcher Explorer 150P on an HEQ5 Pro which is on a permanent pier. I have no guide-scope or filters and just take colour subs. I am stacking in DSS and processing in PixInsight, blindly following a workflow I was shown a couple of years ago. The PixInsight workflow goes: Background Neutralisation DBE Colour Calibration Histogram Transformation HDR Multiscale Transform ACDNR, followed by another bit of histogram transformation Curves Transformation (I possibly overdo this a bit but I like the colours!) SCNR Both these images were with 2 minute subs. The Flame/Horsehead was 2 hours-worth (with 15 darks and no flats) and M81/M82 was 4 hours (with 15 darks and 15 flats). What do you think are my worst offences? I can think of lots of things I could improve but I don't know what to attack first: Better polar alignment Guiding (I do have an 80mm Skywatcher refractor that I can piggy-back but I don't have a guide camera) Bias frames (I believe I could just take one master set rather than taking them every session. Would they have much of an effect?) Using filters (maybe a light pollution filter?) Coma Corrector Better use of DSS Better use of PixInsight
  9. Cheers, so in summary, that heater is suitable but any dehumidifier would need to be a desiccant type, preferably with a drain hose. That's really helpful, thanks guys --- Alistair
  10. Budget Observatory under £250

    That is a really neat and compact observatory and a gorgeous first-light image!
  11. I am looking to protect the gear I have in the roll-away Tardis observatory I built this year (see this thread on the build if you are interested: A dehumidifier: https://www.appliancesdirect.co.uk/p/md400/electriq-md400-dehumidifier) A greenhouse heater: https://www.greenhousepeople.co.uk/products/3872/slimline-eco-heater-55w-tube-heater-with-thermostat/ The observatory itself is around 1 meter square and 2 meters tall. Ventilation is currently provided by the gap in the base around the pillar, a large vent behind one of the 'Police Box' signs at the top, and the gaps around the door caused by my general bad workmanship! Do these seem suitable for my needs? Is there anything else I should consider?
  12. Fixing these star trails?

    Thanks Bob, and I'm also very interested in your home-brew guide camera article. Definitely something to look into once I am happy with the alignment. I'm planning on following this guide to get the alignment sorted: Drift Alignment by Robert Vice since it should be easy and quick to verify if the adjustments I make are correct.
  13. Fixing these star trails?

    That's very interesting on the coma corrector! Once I have the alignment sorted out to enable longer exposures I may try that out on some brighter targets. Here's the result of tonight's investigation It's about 2 minutes of non-tracking, followed by another few minutes of tracking. I can't remember what the target star was but it was a little east of south, around 60 degrees up. It looks to me as though, when tracking, the stars are drifting up the frame. I think I will watch some polar alignment videos and try again from scratch once I have a better understanding of what is going on.
  14. Fixing these star trails?

    Thanks Nigel, I will check this on the next clear evening (which might even be tonight!). I believe I know how to do it: Orient the camera so stars drift across the long side when not tracking. Time roughly how long they take to traverse. Place a star at the starting edge and start an exposure When enough time has passed for the star to travel 1/2 way or so across the frame, start tracking Continue the exposure for the same time again That should tell me which direction is which in the frame and which direction any alignment issues are in, I think.
  15. Fixing these star trails?

    Thanks Bob. Just to be clear, there is no guiding at present. Looking closer at those individual subs, I did spot that there are two issues going on, as you have pointed out: a consistent trailing upper left to lower right throughout the frame. I assume this is polar alignment. I may need to do some physical fixes to my rig in order to sort that out, as well as learning alignment methods (see below). a 'shadow' towards the edge of the frame, particularly noticeable in the top-right and bottom-left corners where it is at 90 degrees to issue #1. I assume this is the coma you are talking about and a coma corrector will be the only way to get rid of this if I want to use the full frame. I aligned the mount quite some time ago, maybe even last year, and have not touched or done anything to check it since. I have not found an alignment guide that I can fully understand so my technique may have been way off. Also, my mounting plate is a home-made affair with a bolt as the pin that the HEQ5-Pro alignment screws push against and it's quite possible that bits may have 'moved'.