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About cjdawson

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    Sub Dwarf

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    Yorkshire UK
  1. My first DSO

    No need to worry about bad pixel maps. That's something that sorts itself out with other techniques. Going into the full detail, there are several types of images that you should be taking for a full set. 1. Lights. You already do this. 2. Darks. You already do this too. (note: should equal the number of light frames, but my experience is that 15 is good when you take more than 15 lights) 3. Bias frames. These are like darks, but taken with the camera's fastest exposure. Some people say that you can use Bias frames instead of dark frames on a DSLR. (I want to experiment this this at some point) 4. Flat frames. These are an exposure of a flat white surface. i.e. no colour gradients etc. Easily done in Av mode on your DSLR. That'll give a good exposure. i.e. not over exposed. Then you process the full set of these in something like DSS. it will reduce the noise. The more frames of each type, the less noise. There are diminishing returns, so whilst there's no limit, the practicalities get silly after too many frames. In addition, there is a technique known as Dithering. This is where the image is shifted slightly between shots. This then means that the picture will fall on different pixels. When stacking, bad pixels (hot and cold) will be averaged out, as though they are noise. If you are not guiding, you don't need to worry about dithering, as the inaccuracies in the scope will give you this for free. (Autoguiding can correct this problem, and that's why some autoguiding software has Dithering as a feature)
  2. My first DSO

    That's a good image of Cassiopeia. Keep going. Take a series of dark frames, not just one.
  3. Whilst it's true that you don't need a laptop when using a DSLR, it can help. Check out https://www.otelescope.com/store/category/2-backyardeos/ Backyard EOS means that I can run the camera using the laptop without needing to touch the scope.
  4. The cost is in the sensitivity of the camera. Years ago, when I first started, what I'm using as a guide camera now, would have been used as an imaging camera. In fact, it still can be!
  5. Star Party Timings

    That would be funny. All the SGL Admin team, in bikinis, in the middle of the night. It'll be freezing!
  6. SGL 2017 Weather Watch

    shhhhhhhhhhhhhh. don't anger the weather gods. I'm off to sacrafice a chicken or two.
  7. This is the guide camera that I went for. As I said, this is the opposite end of the spectrum to the Synguider, I really pulled out all the stops as I don't want this problem ever again. https://www.green-witch.com/starlight-xpress-superstar-guide-camera.html I got it running with PHD2, and decided to do a test through the ST-80. The street lights are over exposed at 1 second! The brick house that you see in the top middle of this image is over 2 miles away. And you can count the bricks. Might even be able to have a go at counting the branches of the trees in behind the furthest house. I did try pointing the scope at a random piece of sky to see if I could find anything. Note: at the time I did this, the scope wasn't even mounted on a tripod (the SCT fork mount of my LX-90 was sat on a concrete patio stone. with the ST--80 on top, no tracking) The image below shows what I saw with a 3 second exposure. Those stars are Mag 7.x (forgotten what) The upshot of this is if you are wanting to get those 300 second subs, make sure that you don't have huge problems with your guide camera. I'm looking forward to using this for the first time. (Not been out observing since SGL last year!)
  8. I've got a SynGuider, and when it works, it's great. The problem with it though, is that the camera is based on a simple web cam and from my experiences with it attached to an ST80 has trouble finding anything apart from the brightest guide stars. I had lots of trouble finding something to guide with. In the end, I've only managed to guide on Pliedes, Orion Nebula and Vega! After getting frustrated with that, and the not being able to see a real field of view, I've bitten the bullet and would a Starlight express to use as a guide camera. Ok, that's probably overkill, but I think it'll solve my guiding issues that have been trouble me for many years. After my experiences with a Phillips TuCam Pro II, SynGuider and now the starlight express, I'd say get yourself a decent mono camera something that is more sensetive than a planetary/lunar camera will help you to find guide stars - after all, you can't guide if you can't get a lock on something. (And believe me, I've wasted many sessions trying to do it stand alone. Just go for a laptop and PHD or something like that.)
  9. Star Party Timings

  10. Anyone bringing their kids along?

    Yep, I'm bringing Kyan with me. https://www.facebook.com/KyanTheCat/
  11. Anyone bringing their kids along?

    That's easy, sent him over to mine. I've got a hyperactive kitten that I'll be bringing with me. She'll keep him entertained. (and save me from scratches for a couple of hours)
  12. M42

    That’s one time when they are useful. There’s a whole bunch of othe techniques that you can do too, so it’s worth spending time learning about it
  13. M42

    Well done on your M42 image. That looks great. The don't worry about blowing out the core, it has to be done to get the faint detail. The trick is to take a series of shots exposed for the core only. This way, you can mask the blown out core with the non-blown out version to be able to get the trapezium into the image.
  14. SGL 2017 SP - Pitch Plan

    IIRC the only place that doesn't have EHU is on the far end of the rally field. Don't think anyone has booked onto those pitches.

    First thing on the schedule is Curry at 17:30. So best to make sure that you are there early enough to be settled in time for the evenings fun. I'm going to try and get there for 3pm this year, that'll give me time to pitch and setup the awning.