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Dr Astronomy

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About Dr Astronomy

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  • Location
    United Kingdom
  • Interests
    astophotography, microscopic images, wildlife

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  1. Hi Both I have just worked through James's Astrophotography workflow - absolutely great. For all that use moded DSLR's James noted in the video that he had residual artifacts from flat files when applied. This is due to the BIAS information being left in the flat image. As the temperature in the camera changes so does the read noise and BIAS hence nighttime image - cold camera, daytime warm camera. As such you cannot subtract flat from light and be left with a good image - negative pixels come in as James describes. Most DSLR's adjust for this automatically by taking a dark immediately after the initial exposure but this is generally disabled for astrophotography. To test your camera take a 30 second image and it will take 60 seconds before it saves. This is due to the camera taking the dark frame. If it takes 30 seconds to save dark frame adjustment is turned off already. The best way to resolve the issue is to use CFA scaling but is not always available. You can scale the flat histogram to match the light histogram - hit and miss but I am sure James could cope with that. Otherwise use BIAS frames - ie after an taking a shot (light and flat) take the fastest possible dark frame you can - say 1/4000 second. This is near enough to be a bias frame but should be 0 seconds if possible. Subtract each bias from each light and flat before flat adjustment and your flats will work much better. For info that is why full blown astro imaging cameras are cooled and temperature controlled. All files are taken at the same temperature so no issues. They are also cooled so noise is kept to a minimum. What you really need is Light frames Dark frames (at the same exposure and temperature as light) BIAS Frames 0.00 seconds (at the same temperature as all other frames) Flat frames (same temperature as lights) And flat dark frames (at the same exposure and temperature as flat) The whole process then becomes seamless. Hope that helps
  2. I have just started to investigate water drop pictures and am at very early stages. In experimenting with stack I have found a lovely effect by using range setting instead of median or average. This is simply a glass bowl full of water with a lot of fairy liquid in it. Into which a few drops are milk are dropped form about 30cm. Shutter at 0.05 seconds with 200 images taken. A selection are then used for the merge - there are no colour corrections made in AP just levels, curves and denoise Bit of fun and costs next to nothing except processing time in affinity.
  3. As well as cleaning the mouse the surface you use it on makes a lot of difference. A lot of people don't use mouse mats these days but they really do help with precision. I recently switched to an ADX ultimate gaming mat - wow
  4. Lovely images and a great and relatively cheap thing for people to try During lock down I purchased a seond hand [£50} celestron digital microscope off the web, took the screen off and added my own camera with two polarising filters. The first (rotatable) goes over the light source and the other just before the camera. Citric acid, Tartaric acid and sodium salts of either do well. I then use focus stacking along with high pass filter (overlay) on a mono luminence layer is AP to bring out the sharpness. I love the idea of a cd case, I have been using selotape but think a cd case would work even better as I can cut a square and rotate it Still practising but here are a couple of attempts
  5. Finally have some good weather for galaxies - each one is over 200 mins of data taken over several nights Hope you enjoy
  6. Love the close up of this section. I have never tried at that resolution before so have something new to target over the next couple of month
  7. As per Nicks post "Is there any chance you can create either a video or detailed step by step instructions on how you do just one of these." Here is the method I use in ap for narrowband processing and its output Hope this helps and feel free to ask if there are any questions!!! ap processing astronomy.pdf
  8. I am working on a pdf for this at the moment though may be some time Will post it here when complete
  9. Thanks all for the great responses. Light pollution is always a pain; you have to travel for very non polluted skies which are few and far between. Went to St Davids for a week to be lucky enough for the clouds to clear and get these shots. Modded Xbox cam should do the job, I did use similar long ago - pop it out of the housing and into an old 35mm film container and it fits a telescope eyepiece as well !!! Don't give up - wait for a clear night and go for it - 30x30s exposures should do the job if stacked
  10. Finally managed to get to a site near St Davids with some very clear skies. The milky way is now in an ideal position to be photographed and is enhanced by having a site with limited light pollution Here are the results - stacked in Astroart and processed in AP mostly using tone mapping The bright object in mars glow.jpg is mars and the reflection of the milky way can just be seen in the sea. Others just show what can be achieved - no gradient removal as the light pollution is so low The image called Milky is with 10x30s stacked at 8mm F4.5 The other two are specialist mono camera with c mount lens at f1.2 Hope you like them Clear Skies
  11. Things have come on a lot - I use a solarmax II which gives about 0.5A bandwidth and dedicated mono camera. I do have a permanent mounted pier system but most of my solar ones (and planetary for that matter) are taken with a portable kit. Well if you call 30Kg additional luggage just for my astronomy kit portable !? Suggest you leave London for a night and head off to the south downs with an F2 ish 30mm lens and give the milky way a shot. - lots of nice dark skies down there. Clear Skies
  12. I will have to go back through my old files and find Planetary images. The UK is a bit far north for most of the planets so I have some archived ones taken nearer the equator. In the mean time here are a couple of the surface of the Sun - H Alpha re-coloured ***please don't attempt to look at or image the sun without very specialised equipment.*** Clear skies
  13. M57 (Ring Nebula) from night of 19/5/18 The more I use AP for image processing the more I love it Hope you like it - can you find the very faint small spiral galaxy IC1296 just to the left of the main nebula?
  14. HELP! Please I am getting blue artifacts when developing RAW (.dng) images I get bring the DNG into the develop persona and develop as per the screen shot attached When I apply the development I then duplicate the background layer and go sharpen - high pass (7.5px mono) and change the layer mode to soft light The navigator shows lots of blue areas yet the master image doesn't - on exporting I get an image the same as the navigator image with blue all over it. The same issue occurs with live filter If instead of softlight I use hard light or overlay there is no issue. In 16bit mode there is also no issue As I prefer to keep images in 32bit until final export is there any way around this issue Thanks
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