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Showing results for tags 'lights'.
Found 7 results
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Hi, I have just purchased a couple of these https://www.celestron.com/products/powertank-lithium-pro The manual says that when the battery is powering something that the 4 red battery will blink in sequence to show that power is flowing. My units are fully charged up, yet when I use them the red lights don't blink in sequence. I just have 2 red static lights lit under the 4 red battery lights. I have 2 of the smaller power tanks, the next model down, and the blue battery lights on those do blink in sequence when they are powering an object. I have tested my new units and they do seem to be providing power. But, if you have one of these, could you confirm please that your red lights don't flash when powering something? Thanks. It's just that the manual is very specfic about this. (I have double checked and the manual is specific to my new units) Still, it's a Celestron manual so maybe my expectations are too high Thank you Siouxsie -
Probably an old discussion but lets review it with some measurements: The dark noise should only have a small influence on the total noise of the final image. Most noise is generated by the sky background. Under good conditions SQM = 20.4, I measure using my ASI1600MM-Cool the following noise (standard deviation) in a dark and in a light for an area where no stars are visible (local measurement using ASTAP): Dark 1 x 200sec, σ = 15 (range 0..65535) Light 1 x 200sec, σ = 130 The noise in the dark is roughly 12% of the light, which seems acceptable to me. That would argue for about the same amount of darks as lights. With a worse SQM, you can probably do 2.5 times less darks for each (magnitude) step. So under light polluted sky you can do with much less darks than lights. If you are going to photograph with the H-alpha filter, it will be super dark. In a single H-alpha (7nm) light I measure a σ = 25r. Of these, 15 are self-noise and 10 of the incoming light. In good conditions and using an H-alpha filter, this is an argument to make much more darks than lights Above for a monochrome camera. To measure with an OSC (color) sensor I think it is better to first split the 4 Bayer pixels into 4 files and then measure them separately. Some measurements with my ASI1600MM-Cool, monochrome: DARKS noise: 1 x 200 seconds, σ = 16 1 x 200 seconds - master dark, σ = 15 4 x 200 seconds combined - master dark, σ = 6.8 This is approximately 15 / square root (4) 41 x 200 seconds combined, σ = 5 90 x 200 seconds combined, σ = 3.8 This is a limit value that arises mainly from unevenness of the pixels. The noise will be smaller, approximately 15 / square root (90) is 1.6 STACKED LIGHTS noise (lights corrected with darks and flats): 11x200 seconds, σ = 70 (measured at a star free area, standard deviation in 0..65535 range, sky conditions could have been different) 18x200 seconds, σ = 36 18x200 seconds, σ = 40 40x200 seconds, σ = 26 42x200 seconds, σ = 30 44x200 seconds, σ = 25 58x200 seconds, σ = 20 95x200 seconds, σ = 16 Apparently the light noise decreases considerably while stacking more lights and I reach σ values up to 16 a 20. You do not want to stack these images with a single dark having a σ = 15. If you want to keep the dark noise added below 10% of σ = 16 then you need 100 darks because they give: 15 / square root (100) = 1.5 noise. So this confirms for a good suburban site (SQM=20.4) you will need about the same amount (or more) darks then lights. For a more light polluted area you can take less darks since the noise from the skybackground will be abundant. For H-alpha work you better take more darks then lights. Han
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Evening all, I've been trying to get to grips with stacking images and think I have sort-of figured out how to do the calibration images as well as the lights. However, as I read through these forums, I'm seeing lots of references to people successfully stacking lights that have been made up of various different timed exposures. I seem to have fallen under the impression that all the light images need to be of identical parameters. I've even tried experimenting with deep sky stacker using lights with different parameters and DSS always rejects them ( I end up with the "only one frame will be stacked" error. Appreciate any insight on this - thanks
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Dear SGL. Your opinion is required please. We are very lucky and live in Southern Central France with stunning dark skies. When we get time we look up at the wonders of the night sky. Last night we set up our sunbeds and after a bit of bat watching we settled back to a couple of bottles of red and some cheese. We saw a few shooting stars the milky way as bright as ever, 2 iridium flares as predicted by ISS tracker and lots of air traffic. But we saw those strange flashes again! On several occasions in the past my GF has spotted very brief flashing lights, sometimes 2 in the same place. I poo pooed her until I saw them to. Then I was the one who was poo pooed! Sometimes these flashes are in different parts of the sky but we have confirmed today they all lie at around the same angle and mainly in the eastern to southeastern sky. We do not currently have a great view south so have not noticed them there. So a more detailed description of these flashes: They are brief - less than half a sec. Bright - brighter than any star in the vicinity. They do not seem to be associated with and moving object - satellite/plane. They are sporadic - sometimes you will see 2 or 3 in an evening, sometimes 1. Sometimes you will see 2 flashes in exactly the same spot seconds or a few mins apart. From reading the forums here I get the impression we are witnessing Geostationary satellite Flares but I can't be sure? How often do those distant objects use their thrusters? How bright is hydrazine? Should we be able to see them? As all the sightings tend to be in the same area it sort of points to that but I really don't know. Your opinion is greatly appreciated.
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Should I keep all my light-subs or only the final stacked image? My subs are 24 meg each so from a work flow perspective it would be nice to be able to toss them and just keep the final "stacked" image for processing. Also, same question on darks. Can I create a library of darks at temp & exposure and only keep the masters not the subs? Thanks, Lloyd -
I was wondering if any of you good folks might be kind enough to physically show me, and others, some examples of unprocessed LIGHT images from a DSLR (taken under medium light pollution), that can provide me with a point of visual reference? I'm looking for an approximate indication of the kind of 'look' I should be aiming to get on my DSLR screen at the end of a shot; Essentially trying to figure out where the threshold lies between a good, usable LIGHT image, and one that is over-exposed and has too much light pollution noise to be useful. At this stage in my learning, trying to read-up on it is making my brain ache, so some actual examples of what my unprocessed LIGHTS should physically look like, will be really useful. I live in a reasonably light polluted area (edge of a large Town). Thanks in advance- 19 replies
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Folloing on from a post I made in early November :- http://stargazerslounge.com/topic/198663-is-this-acceptable-or-only-30-mins-of-data/ I am finding myself frustrated by lack of time and the clouds.... (set up three times last week, clear skies, but by the time it was dark the good ole clouds had rolled in and put paid to another night.. So with the limited time I set myself a challenge to see what I could achieve with only 30 mins of subs, I have included three images of what I have so far. I would be interested to see what others could achieve with the same limitations, so are you up for a "30 Minute Challenge" ? Not too many rules :- Only 30 mins total of Subs (1 x 30m, 2 x 15m, 15 x 2m, 30 x 1m, you get the idea...),(Be Honest) Unlimited dark's, flats, bias etc. Include some capture information with any image submitted. Thats about it.. So heres my attempts :- all taken with a SW200P, HEQ5 Pro unguided, Canon 1000D at ISO800 M31 15 x 2m Lights 10 X 2m Darks 10 x Flats 10 x Bias M45 12 x 90s Lights 10 X 90s Darks 10 x Flats 10 x Bias M81 20 x 90s Lights 10 X 90s Darks 10 x Flats 10 x Bias Any One Else Up for It ????
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