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About kens

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    Proto Star

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    Deep sky, fly fishing, cycling
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    Melbourne, Australia
  1. kens

    PHD2 Guiding Setup Help Needed !!

    Make sure your guide rate is between 0.5x and 0.9x sidereal. Can you also post the guide log where you did the calibration?
  2. If I'm short on time (normal situation) with a narrowband target that is primarily Ha then I usually go with HHGB or as a bare minimum HHGG.
  3. The OIII channel is very weak. In fact the median value is only 386. Ha is better with a median of 1138. Assuming the subs are of similar level then you need to expose the OIII subs much longer to get them above the noise. I tried a variety of combinations.and the best visually I could get, in a short time, came with Ha as Luminance and Red and OIII as Green and Blue (i.e HHOO) with ratio of 3.0 on OIII to bring it up to an equivalent level to Ha. Any attempt at a Wipe just killed the OIII contribution. So I just did an autodev and a colour balance to restore the red after autobalance. The only real contribution from OIII is to make the star cores look white. Not sure how that compares with what you could get. Attached is the result along with stretched version of OIII so you can see its contribution.
  4. May be useful to post your stacked images to DropBox or equivalent. Like most things it depends on what you are working with. My usual workflow is Bin, Crop, Autodev, Wipe, Manual Develop then various stretching operations and finally colour balance. Loading the channels at the start depends on the target and how the channels look. Often HOS (as RGB), sometimes HHOS (using H for L as well) Most of the work is in Colour Balance to get the desired effect.
  5. kens

    PHD2 issues

    An ST4 cable has 4 wires. One each to move the mount N,E,S,W
  6. kens

    PHD2 issues

    Most likely severe dec backlash but could also be a faulty ST4 cable. Another possibility is that Dec guiding is set to North only. Can you post the guide log?
  7. Use DeepSkyStacker http://deepskystacker.free.fr/english/index.html You can use it for stacking and for aligning the different channels. To align channels is not immediately obvious but is briefly described in the FAQs. Choose the sub you want to align everything to. Lets say it is one of your green subs. When you stack your green subs, right click it and select "Use as Reference Frame". The reference frame is identified by "(*)" It will also be ticked so it is included in the green stack. When you stack your Red (or Blue) channel, add the chosen green sub, right click it and select "Use as Reference Frame". Make sure it is not ticked as it should not be stacked with red or blue subs. You'll end up with three stacked frames, one per channel, all with the same alignment.
  8. kens

    narrowband exposure times

    I always use offset 50 at all gains. I like to keep things simple.
  9. Could be just about anything but"flexure" covers most ills Some things to consider: how many pixels at what pixel scale was it? And were you dithering?
  10. kens

    narrowband exposure times

    With narrowband I generally image at gain 200 with the ASI1600. As always, aim to bury the read noise so expose to an ADU value in the range of 1000 to 1500. There is quite a difference between filters (depending on sky background) but I like to keep things simple so I use the same exposure on all three filters - whatever gets the lowest response over 1000 and preferably matches my darks library. I also allow for some reduction in the sky background over the night as the sun sets and people turn off their lights. Typical exposures range from 180s to 300s under light pollution at F/5.5. You'll need experiment under your own skies.
  11. With the ASI1600 most of us prefer flat darks over bias as bias frames tend to be inconsistent. If you use the same gain, offset, temperature and exposure time you can use the same darks. Similarly, flat darks depend on you having the same exposure time for each set of flats. I'm a bit fussy so I take my flats to reach a specific ADU count so each set has a slightly different exposure time. But I run it as a sequence so when done I put on the cover and rerun the same sequence for flat darks. They are short so its quick.
  12. Under LP the dynamic range is not impacted. Indeed, for a given target at a given gain, saturation of a subframe is less likely as fewer target photons are captured in a shorter exposure and the sky background would be exposed to the same level. So lets say you need 30 seconds under LP vs 300s in a dark sky to bury the read noise with sky background. Then you've captured 10x the target photons with the dark sky. What is heavily impacted under LP skies is SNR.
  13. You really only need Polaris. Certainly for PDA that is sufficient. With SPA, a couple more stars are better but one is enough. Sharpcap needs more because it has to plate solve and the only other stars near the pole are quite faint.
  14. SPA is the Static Polar Alignment tool in PHD2. You can find it on the Tools menu. There is a video tutorial at https://openphdguiding.org/polar-alignment-tool-video-tutorials/ Polar Drift Alignment (PDA) is also on the Tools menu and is also covered in the videos. Using these tools might help you get your polar alignment done quicker
  15. Try using PHD2's PDA and SPA tools. Point at Polaris, and start PDA. Select Polaris or any star you can see and adjust your PA. The switch to SPA and fine tune it on Polaris. That should save you some time as you only need to see the one star. Why are starting PHD2 for each target?

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