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About BrendanC

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    Star Forming

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    Buckinghamshire, UK
  1. Ah, here we go again! I've done a ton of research on calibration files and what I've found is, there is no consensus! So here's a perfect example: I have a 'yes', a 'no', and a 'yes and no'! The perfect balanced sample...! (Don't want to give the impression I'm ungrateful though, thanks for the replies all). Totally understand the need for darks and flat darks to be at the same temperature, and that's why I referred to a library: with my previous camera I spent quite some time taking loads of darks and dark flats by cooling the camera, letting it heat up, cooling again etc until I could bring sufficient numbers of them all together at each temperature (according to what the camera's sensor told me). I did this because I thought I was supposed to! Also because packages like DSS and APP tell you to, and have specific features for these calibration files such as matching them via groups etc. I just thought it was best practice. They were all shot at ISO800 because that's what I use for everything, with the darks matching the lights for duration too. I've also come across the argument that darks aren't needed at all. This would be more convenient, but I did find a web page (can't find it again) that outlined why you need both. So, given that there was no consensus, and some people argued that all calibration files are needed given different circumstances, I did both, figuring that it was a bit of a pain to begin with but once done, it was done. So, if I just use biases, and a large dither (which I do anyway), is it definitely the case that I don't need darks or flat darks (or even dark flats - yes, I've read the thread that goes on and on where people even discuss which phrase to use)? And if so, another question: do the bias frames have to be at the same temperature too? Again, research yields varying takes on this. [Post-edit - I think it was this page, which did my head in, not least the comment that 'a good way to think about it' was Pre-processed Image = (Light - Dark) / (Flat - Dark Flat), which someone then elaborated on by clarifying it as Subcalibrated = (Subraw - Bias - (Darks - Bias)scaled ) / (Flats - FlatDarks): https://www.cloudynights.com/topic/658692-why-do-you-need-bias-frames-if-you-do-darks/]
  2. Very interesting! Thanks for sharing this. I can see that your frequency of viewings goes up each year, presumably that's as you get more used to your equipment and observatory? I keep my scope outside under a (fairly serious) tent which keeps it dry, but even though I can be up and running in half an hour, it's still been very frustrating recently. For what it's worth, here's the Jupiter image I managed to capture with my T7C (ASI120MC clone): I also got a moon in there which I didn't realise until post-processing. Last night was without doubt the clearest and calmest it's been for months - but my DSLR was being repaired so I couldn't take advantage of it!
  3. Hi all, I just got my camera repaired (actually, replaced), and even though it's the same model (EOS1000D, modded), it's obviously a different sensor, different thermal characteristics etc. Am I right in thinking this means I need to rebuild my darks library? I think it does, I'm just wondering whether there's any way I can around it! Thanks, Brendan
  4. Well, tonight, Clear Outside got it wrong - I had a couple of hours of clear sky! Managed to get some slightly overcast Jupiter. Wheel of fortune and all that.
  5. If we're sharing telescope names now, to help each other through cloudpocalypse, my 130pds is called Scopey Wopey Doo Dah.
  6. I'd probably choose a stronger word but I thought I should keep it clean!
  7. If it were just about granularity, then how come it always gets worse, not better? (PS I wasn't being entirely serious about Cloudy Nights!)
  8. Here's a thing: on Clear Outside, I swear that it never shows clear blocks of time the closer you get to that time. For example, at about noon today, it showed three hours tonight, but I just checked and they've gone. It's always that way around - promising something and then revoking it as the time approaches - never the 'right' way around. Grrrrrrr!
  9. I feel your pain. I'm all collimated up and raring to go too - but according to Clear Outside, the 90-minute block of clear skies I had until about an hour ago just disappeared...
  10. I agree with the comments about equipment 'failing' even when it's not being used. What I tend to find more is that I'm so out of practice, I can't remember what to do next! I'm now a dab-hand at putting the rig together and taking it apart again. It's the bits in between that disappear without practice. I got a dinky little T7C (ASI120MC clone) so that I could do some planetary work as well as use it for guiding, in the belief that you can get the shots you need very quickly and take advantage of gaps in the cloud. Which is partly true because I got a nice shot of Mars the other night - then, last night, watched as Jupiter, then the Moon, then Saturn all faded behind the clouds just as they were emerging from behind the tree! Thwarted, again. I started out on this lark thinking I would purely want to do visual. However, I quickly found myself wanting to go the photography route, mainly because there's so much more out there among the DSOs, and I like the idea of 'seeing' what is 'hidden', plus you can share your work with people. Still, I guess running out and quickly chucking in an eyepiece wouldn't do any harm.
  11. Thanks for the helpful comments everyone. I'll try and keep the faith. During the 'cloudpocalypse' I've been reading books, building up my objects spreadsheet, writing my blog, tweaking my session timings spreadsheet, watching videos, reprocessing old data etc etc. But there's a limit to how much can be done in the background, as it were. There's an outside chance of some clear bits tonight. Fingers crossed.
  12. I keep my mount set up in the garden, and can get the camera etc all rigged up in about ten minutes. After polar alignment, I can be up and running in half an hour, all of which I can also generally do before full astronomical darkness. But still, so few occasions to do this. I sold my trusty little Skywatcher 130P AZ Goto so that I could concentrate more on imaging. Now I'm wondering whether I did the right thing - I could just plonk it anywhere in the garden and be up and running in no time.
  13. This is the thing. I never expected it to be easy, but I did expect more opportunities to do it once I'd overcome the hard bits! I used to have a classic car, a Spitfire. It wasn't until I got it that I realised how often it's cold and wet in the UK. Now I've got a telescope, I realise how often it's wet, windy and cloudy!
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