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  1. You can buy step down adapter rings that screw into the filter thread at the front of the lens. I got a few from: https://www.crookedimaging.co.uk/products/kood-stepping-step-down-ring-lens-adapter?variant=31154001289 They reduce the f ratio as follows: 72mm->67mm (f/2.8 ->f/3) 72mm->62mm (f/2.8 -> f/3.2) 72mm->58mm (f/2.8 -> f/3.4) 72mm->52mm (f/2.8 -> f/3.8) The 200mm lens is amazing and I shoot wide open all the time. But I think if you step down a bit, you can improve the shape of stars at the corner of the images even more. I haven't used the rings yet, so I can't first hand tell you that this is true, but I'll be testing it soon. The positive of using a step down ring is that you avoid the diffraction spikes from the aperture blades. Looking forward to more of your images!!
  2. Very nice image. Are running the 200mm wide open at f/2.8 or have you stepped down?
  3. Thanks Adam. The green channel definitely looks a lot cleaner than the blue and as I suspected, they're both receiving the oiii signal. Do most people scrap the blue and red channels and simply keep the green when doing a narrowband combination? A dual band filter sounds nice, but I like to image with 200mm lens, so a clip is ideal for me (which nobody does as a dual band anyway).
  4. The idea of a dual/tri band filter is really appealing. Narrowband imaging on a dslr/osc should be more efficient as you're shooting both Ha and Oiii at the same time. I would separate the channels as @AdamJ suggested and process them individually to get a custom bi colour palette (I don't think an SHO palette is achievable here). Is it possible that the focus may be slightly off between the channels especially since you're using a doublet. @thomasv could this be the issue you're seeing in your image?
  5. If you're plate solving, this shouldn't be an issue. It should resume where you left, regardless of when you stopped. I find that doing a phd calibration after the flip can leave the scope away from the target though. It would be nice if it would do a goto++ after the calibration as well. I have mine set to 5 minutes, but I only started playing with it last week. It ended up waiting 15 minutes before reimaging. So I'll be looking at minimising that a touch as well.
  6. I have an astro modified 700D, which I've been using for the last few years, and while I would love to take the plunge and get a mono ... I can't substantiate the 2 grand price tag at the moment. As well as the regular RGB images, I've been using an Astronomik 6nm clip filter, which has given me some wonderful images. Processing them isn't too difficult as it is all isolated to the red channel. My question here is ... does anybody have any experience acquiring and processing oiii data on a dslr? Are you satisfied with the astronomik Oiii filter? More than anything I'm intrigued about the fact that the wavelength sits right bang inbetween the blue and green filters on the bayer matrix. Does this mean that I need to extract both blue and green channels and combine them? Does that improve noise compared to the ha filter as I'm essentially using the other 3 elements of the bayer matrix (despite the fact that the blue/green filters only allow 50% of the light through at that wavelength as well) Thanks
  7. That's stunning! That looks like 8 hours worth of stacked data from my dslr! I'm envious lol.
  8. What image processor are using? Pixinisght/Photoshop/Nebulosity?
  9. This is simply using a dynamic crop and the automatic background extractor in Pixinisight.
  10. First impression is that the original images are hugely misaligned. The stacker has registered the images and stacked them correctly and the bright part in the middle is the only coincident part of the group of raw images.
  11. There's a lot of really nice detail there. Try and run a gradient exterminator in PS or background extraction in PI to get rid of the rainbow effect.
  12. It's seems to me that the diffraction spikes from the bahtinov mask are better placed for the luminance and the ha. Sii and Oiii seem a little bit off. As @sloz1664 suggests, autofocusing between filters is probably the safer option.
  13. I agree that Ha is the way to go when the Moon is out. To improve your contrast it also makes sense to shoot as far away from the Moon as well (every little helps). In terms not bothering with Ha when using a DSLR, as long as the DSLR is modded I say go for it. Sometimes the funds don't quite stretch to buy a CCD/CMOS imaging train. I've managed to get some decent results with my DSLR + astronomik 6nm Ha filter (Narrower bandwiths help with contrast and even more when the moon is out). Of course, the results won't be as good as those generated with a Cooled mono chip and when the moon is not out ... but that shouldn't stop you from going out and getting some imaging time under your belt.
  14. Rico


    It depends on your setup, your sky background, the brightness of the object and a number of other things. I shoot with a modified 700D/SWED80/FR/Astronomik CLS filter and 5 mins is the minimum I would shoot, at ISO1600, to get some of the faint nebulosity. Some of the stars, will end up over exposed and with an object like M42, the core will be completely blown out, but that's the nice thing about using multiple exposures. Some of the faint stuff is so dim, that the exposure needs to be sufficiently long enough to pad the left side of the histogram. Otherwise, it'll be hidden in a sea of noise. I guess an other thing to consider, is artefacts from over exposed stars. Some chips and scope setups generate awful patterns which simply get worse with increased exposure times. I guess most if is down to trial and error. Try it, if it works, great, if doesn't, fix it and tweak it until you get it just right.
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