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catburglar

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About catburglar

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    Star Forming

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    North Wales
  1. catburglar

    How to do flats with Samyang 135mm F2

    Thanks for all the tips- exposure time was approz 0.01s - so will try to dim the panel and increase the time, I’ll also take a look at increasing the distance to the panel and might flock the lens hood- wonder if I’m getting some glancing reflections that might be throwing the flat off
  2. I'm shooting with a Samyang 135mm @ F2 on an APS-C sensor. The raw files have a strong vignette (probably about 2 stops at the extreme corners- but I haven't measured it). I'm trying to correct with flats when I stack in DSS, but I still end up with a strong vignette in the resulting autosave file. I've tried using twilight flats with some white paper over the lens to act as a diffuser and a similar technique with a tablet screen. When I review the master flat, it shows the same vignette that the raw images do, so the flat division should work. I realise I could stop the lens down, but I see many people here using the lens wide open - so there must be a way. Does anybody have any tip/tricks for getting good flats at F2. John
  3. Barry I do understand that there’s always some risk- but most fellow astronomers that I’ve come across treat their kit pretty well and describe it honestly when selling, so I’m not too concerned. I’d just like to make sure that the sensor is nice and clean- could you post a single uncalibrated sub from one of your recent imaging sessions. If it’s too big a file I could PM you a link to my OneDrive so you could upload the RAW file. If that looks OK, we can confirm the details.
  4. Hi Barry I’m interested in the EOS 600D. Would you be able to pack/post it safely? John
  5. There's some good learning in the last message from Antonio. I went down the cheapskate route- got a RPi 3b+, installed Astroberry server (like StellarMate- it's Ubuntu with wifi hotspot, indi, kstars, plate solving and lots more pre configured). I'm reasonably proficient in Linux, but there was still quite a lot of head scratching getting it all to work. It's entirely possible to run kstars, indi and platesolving on the Pi- it may not be the quickest, but it's certainly workable- and it's the way I've setup recently. KStars and EKOS is certainly more fully featured than APT, particularly if you want scheduling of multiple imaging runs, multi panel mosaics etc. However, if your needs are a little more modest, a pretty cheap win10 tablet, running APT and real vnc server (so you can access it remotely) or similar can get you a long way. You don't need a lot of processing grunt to run an imaging session. One last point about KStars on windows connected to RPi as an indi server. in this configuration Kstars won't do offline plate solving- so you need both your Pi and windows PC to be on a network that has internet access, or have your PC connected to the RPi in hotspot mode and another connection to your internal home network so you can platesolve.
  6. There’s this adapter from FLO- if you can unscrew your current nosepiece, it might do the trick. https://www.firstlightoptics.com/diagonals/william-optics-sct-adapter-for-2-diagonals.html
  7. I agree with Olly- I don’t usually bother with darks if using short frames and a relatively low noise camera. There’s the natural dither option, or you can use APT’s internal dithering option which works really well even without guiding.I I set it to dither by up to 5 pixels every frame- it only adds a couple of seconds between each exposure and means it does a pseudo random walk around the centre of the image. It is very effective a sorting out hot pixels and such like.
  8. The SW ED120 with matched reducer gives 765mm FL and pretty close to 1arcsec per pixel. Not the ultimate apo, but has refractor simplicity, and the weight shouldn’t tax the mount too much
  9. I may be interested- I was looking to get my 1300d modded. Have you got a bit more detail? What mod have you down- H-alpha or full spectrum? What’s the issue with daytime photography/ camera lenses- is it just white balance or have you got focus issues? How old is the camera, what’s the shutter count and what do the calibration frames look like? Can you share examples? Thanks
  10. catburglar

    EQ5 for Imaging?

    You can get good images with an EQ5 mount- particularly if you have a lightweight/ short focal length setup. It’s likely to have a bit more backlash in the gears and a little more periodic error than the HEq5, but it’s still doable.
  11. catburglar

    Should i buy 200mm or 300mm lens?

    I think the Rokinon 135mm is likely to be a better lens than the Super Takunar 200. But what’s best for you may depend on a couple of different factors....cost and field of view. I’ve attached a couple of images I’ve taken with the EOS1300 and Rokinon 135mm. (I’ve still got a lot to learn), but I was quite pleased with them. I find it quite tricky to get rid of all the vignetting with flats, but because the short FL and wide FoV it means you’ve got a little bit of scope to crop the image. The 200mm will get you a bit closer in but because it’s operating at F4 vignetting/field flatness might be less of a problem. Id you can find one within budget I’d get the 135mm, but if you can’t the 200mm is a good lens too.
  12. catburglar

    Should i buy 200mm or 300mm lens?

    Out of the two you mention, I think I’d probably go for the 200mm. The shorter focal length will be more tolerant of tracking /polar alignment errors meaning that you get more good frames to stack in your final image. If you plan to add guiding to the setup in the near future then the 300mm might be a better bet, but guiding adds complexity and kit that would tend to limit portability- if that’s important to you. You may also want to consider a Rokinon/Samyang 135mm ED F2- I’m not sure if you’ll get one within budget, but it’s a good lens to start out with. Just one word about your choice of targets- most planetary nebulae and galaxies will be too small for either of these lenses to give great images. There are plenty of targets in the winter sky that will suit these shortish focal lengths including M31, M42, M45, Rosette Nebula for starters.
  13. catburglar

    Advice On Dob Mirror Cells Please...

    Unless you plan to go up in aperture, I’d be tempted to keep the SW mirror and cell. Any improvement in quality from a custom mirror at the same aperture is likely to be marginal. You don’t say why you want to change, but presumably you want something that is lighter/more portable. If this is the case I’d put the money that you save because you’re not buying a mirror into optimising the mechanical elements that impact on setup, usability, stability, thermal issues and light baffling. E.g thicker/carbon fibre truss poles , integrated dew control for primary and secondary with internal cabling etc.
  14. catburglar

    Skywatcher ED80 Pro

    Sky-Watcher 130pds with SW coma corrector would suit your camera with 2.4micron pixels. The cc acts as 0.9x reducer so you’re imaging at f4.5. You’d need to make sure you can guide sufficiently well at approx 0.9arcsec per pixel.....
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