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Big Jim Slade

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About Big Jim Slade

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    iandwebb@hotmail.com

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    Leafy Bedfordshire, UK
  1. See also the Cosmic Distance Ladder, of which parallax and the AU are just the first two rungs. https://simple.wikipedia.org/wiki/Cosmic_distance_ladder
  2. I'd post one of mine but it won't be much help as I have everything connected with M48 adapters so I have a fair bit vignetting. You're showing a 2.2% difference between top and bottom in that image, so the stretch is making it look far worse than it is. EDIT: Just compared one of yours to one of mine, and while they are visually pretty different, the MAD values are with 4 (yes four) of each other.
  3. Hehe, indeed. The problem with PI is you can start out trying to get a nice piccy and end up thumbing through tomes like "Image Processing and Data Analysis - The Mutliscale Approach" looking for tips. (Sez the man who has barely mastered calculus)
  4. Well, there's an interaction with all the steps here. If the weighting/noise evaluation of the images isn't working (for example giving too much weight to the shorter subs), then your pixel rejection has a much harder job to do. Fundamentally, it's the pixel rejection algorithm's job to get rid of statistical outliers, so if the weights favour the longer, lower noise subs, you should have less trouble tuning the pixel rejection. More signal, less noise.
  5. My recollection is that the docs suggest WSC for > approx. 10 images, and Linear Fit for more than 15 images. My policy is to run both on any given set of data and use what works best - it will vary I think. The best bit of PI wisdom I've learned is that there is no one single recipe that works on everything. Blue will always be the noisiest channel, there's just less of it. As far as integrating different length subs goes, a better approach would be to move to using the Subframe Selector to do the weighting but this is more than a little fiddly! It's my default workflow now, but it took a while to get comfortable with it.
  6. Yes that's the ones I was thinking of. They can't be exported outside and used on other servers, but they do the job for us.
  7. Bear in mind that what you're looking at is a Certificate Authority which is used to sign certificates, not a certificate itself. In essence it can't show that it's trusted, because its job is to confer trust on other things. With custom CAs like this we have to decide ourselves if we trust them, and the install them if we do. Most of the time we avoid this because browsers all come with what's know at a "Root CA Bundle" which includes all the common root CAs from people like Google, Go Daddy, Comodo etc. Actually, you can go a bit further. The CA is signed with a public key, so if you can find a list of DoD signing keys (which the may well publish) you can confirm the the fingerprints match. That's pretty bomb-proof, assuming you trust the site with the keys. This kind of thing is not un-common in larger organisations btw. At work, our internal certificates used to be signed by our own CA, so colleagues used to have to download it so they wouldn't get security warnings. These days Amazon provides signed certificates for free that work in all browsers, so we use those now. Hope that helps rather than confuses.
  8. TheSkyX works well the EQMod in my experience. Follow the setup guides and get it talking to the mount, then in TheSky just configure the the telescope to use ASCOM and choose EQMod in the drop down. You should then be able to hit connect and the display should pop up and you'll be good to go.
  9. That site has a cert signed by the one of the US DoD's own root certificates (DOD ID SW CA-37), which are not part of any standard browser install as far as I'm aware. You could just add an exception if your browser lets you, or you could download and import the root cert from the net, I found them here: https://militarycac.com/maccerts/
  10. I must admit I'm a bit confused about the PSF part here. I don't quite understand why only using just Moffat (in Steve's example) or just Gaussian as Wim mentions above, is necessary. To get the most accurate fit to characterise the PSF don't you need both? (I should add of course: thanks to Steve for doing this. I've been through multiple write-ups on Deconvolution and it's very hard to find one that makes a very complex process as clear as this does. )
  11. Agree with Vlaiv here. Looks like a clipping problem during stacking. I don't use DSS, but I'll bet I could reproduce it in PixInsight if I had reasonably "hot" stars and high pixel clipping turned on.
  12. Given the lower surface brightness, plus the high sky background, you may be better off with lots of short (60 secs) exposures. If you get 30 or so it may start to emerge. (Caveat - I'm a CCD guy, so someone with more CMOS knowledge may know better.)
  13. Photo of Steve's first obsy: ? Seriously, I'm amazed by what was done on film with manual guiding. There's a bit of me (a very masochistic bit) that fancies giving it a go sometime.
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