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    SGL 2017 SP

kens

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About kens

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    Star Forming
  • Birthday 08/05/61

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    Deep sky, fly fishing, cycling
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    Melbourne, Australia
  1. Filters ..... how important?!!!

    You can get nice monochrome images without a filter. Light pollution limits how good you can get but stacking with as much integration time as you can should give you satisfying images. Your subs will be necessarily short so you will need lots of them. A single Ha filter will give nice monochrome results with emission nebulae. You can take longer subs but you'll need more integration time. LRGB filters let you produce color images and the colors can enhance the image. I think it helps add depth to objects like globular clusters. You won't damage your gear by not using filters on DSOs so just try it.
  2. Target for 1st Autoguide

    I'd be inclined to use Sharpcap of those choices but you might also consider PHD2 drift alignment. The first thing to concentrate on is getting a good calibration in PHD2 - I'm assuming that's what you are using as guide software. You might also run the guide assistant and use its recommended settings. Once you do that don't be tempted to fiddle with them for now. Even if your guiding seems off it is unlikely to be due to the PHD2 settings as long as you got all your input data right and got a good calibration. Then you'll need to get your focus right with your imaging camera. Do you have a bahtinov mask? As a first target I'd suggest something like a decent sized globular cluster. Fairly easy to find, look great when imaged but not too demanding, especially if you are dealing with light pollution. M13 perhaps? Once you've got your target, take some sample images to get your exposure right - use the histogram. Don't worry too much about your first images. Just have some fun, and learn as much as you can each time. I reckon there's a million things that can go wrong in any imaging session and each time you learn to cut out a few of those. I think I've got 999,900 or so to go.
  3. Guiding scope

    The weight itself is not an issue. The biggest issue is to ensure the lens mount ring is securely fixed to the scope ring and cannot rotate. To do that you tighten up the circular lock nut that you can see in my picture under the mount ring. If it doesn't feel tight enough then rig up an L bracket on the rear ring that screws onto the ASI120 - similar to what I've done. I picked up my bracket from my local hardware store - 2mm steel I think and used for DIY shelving. I had to drill a hole in the appropriate spot and a couple of 1/4-20 screws and washers to attach to the ST80 ring and the ASI120. That will stop the whole setup rotating and unscrewing itself. Besides, you may need the same L bracket when you come to use the ST80 as a guide scope as the focuser tube is a bit sloppy. Your mount will handle the extra weight with ease. Guiding at 100mm should be fine - just. I think its worth a try. Beats having your kit lying around unused while waiting for the rest of your gear to show up.
  4. Guiding scope

    Any of those lenses would work - even the 85mm since you are only guiding 400mm ST80. The ring mounts are cheap as long as you dont get an "original". I found mine on eBay for a few dollars. You might find it easier to get one for the 70-200mm zoom as they are designed for heavier lenses. If you use the zoom lens you need to make sure the zoom does not change while guiding - especially when pointing upwards. My Tamron has a sliding zoom but a thick rubber band stops it moving adequately for short focal length imaging. As anotehr option there are some L brackets available that you could use to mount the ASI120. The camera woluld then need to support the weight of the lens so the bracket needs to be solid and preferably use a lighter lens (so likely the shorter focal lengths). You can see I use an L bracket on my ASI120 but you would want something more solid than that as mine is just to prevent movement in te focusing tube.
  5. Guiding scope

    It depends what lenses you have available. I'd start with something with a focal length between 100mm and 200mm and preferably fixed focal length. The attached pics show where to piggyback onto the ST80
  6. Guiding scope

    I think the simplest setup is to attach the QHY13 to the ST80 and use the Canon lens as a guide scope. I say this because if you want to connect the Canon lens to the QHY163 you would probably want to make the connection more rigid with some sort of dovetal bar and a tripod mount ring for the QHY163M as well as the lens. It's doable but gets complicated getting the bits to all match properly. So connecting the QHY to the ST80 should be pretty straight forward. Next you need to get an adapter for the Canon lens to either a T2 or C/CS thread. That lets you attach the ASI120 to the Canon lens. I'm assuming you have or can get a tripod mount ring for your Canon lens so that can be mounted on top of the ST80. Ideally you would make the connection between the Canon lens and the ASI120 more rigid but that can also be tricky. Hopefully, you can get by without doing that for the time being.
  7. Guiding scope

    The ST80 has a standard 1/4-20 mounting point on one of the rings. So you can piggy-back a DSLR there - either the camera body or a tripod mount ring on the lens. Alternatively you could image through the ST80. Get an adapter for the camera lens to use that as the guidescope by attaching the ASI120 to it. The ASI120 is hopfully light enough to just hang off the end of the camera lens. If not, the ASI120 also has a 1/4-20 threaded hole at the back so a L-shaped bracket could be used. Camera lens to T2 threads are a bit hard to come by but there are lots of lens to CS/CS mount adapters. The ASI120 has a T2 to C/CS adapter (used for the fisheye lens that comes with it). I reckon I've tried every single permutation at one time or another - mainly because I like tinkering.
  8. It makes no difference to guiding. PHD2 does everything in pixels and the scaling is just for display. In a way it would be nice to be also able to input the imager focal length and have the results shown in pixels on the image itself since that's what really matters. Another tool worth looking at is PemPro log viewer (a free add-on to PemPro) which can be used to analyse PHD2 logs. I don't think there is a webpage for it but it can be downloaded at http://www.siriusimaging.com/PEMProV3/PEMProLogViewer_Setup_1.4.0.0.exe and there is a tutorial at
  9. Guiding at 7.7"/p with 0.1p min movement means that PHD2 wont correct until you've deviated 0.77" Given what I've heard about the Mesu I would have thought a smaller value would be possible - say 0.05. And you could possibly use a regular hysteresis algorithm on dec rather than resist switch if it has no backlash. Might be worth checking with the experts over on the main PHD2 forum and/or other Mesu owners. I wish I was one - one day maybe.
  10. No I meant the graph. Two reasons: first up its easier to find a smooth patch of 50 samples than 400. The other is that those 50 samples are spread across the full width of the screen so any spikes are 8 times broader and look less spiky as a result. You are right to run at that scale when monitoring and when you are watching it in real time it does look choppy. But if someone shows a screen shot at scale x:50 with 1 sec samples to brag about how good their guiding is then 50 seconds of guiding is not very representative.
  11. The logs are usually located under Documents\PHD2 but thT is configurable in the brain Global tab.
  12. The other bluff is setting the X: scale to 50 so the graph shows only 50 samples. Makes it look really smooth on the screen. Its useful for monitoring as you can then get an idea of how a given sub is affected. But for troubleshooting after the fact the log file is the only way to go.
  13. Drizzling makes the images 4 to 9 times bigger so it is normal to select a part of the image to drizzle and stack to avoid running out of memory. To do this open an image the use the custom rectangle mode over on the right. Once clicked you can rubberband a region of interest on the image. DSS even shows you the boundary that will result in the same amounf of memory at 3x and 2x drizzling.
  14. Not Brilliant Guiding

    Its possible the drift I saw was an artefact of the backlash corrections. PemPro log viewer can remove the guide pulses to show the underlying PE and PA drift bit when dec backlash is bad, especially if in one direction, it shows up as a steady drift that looks like PA error. The only way to really check is with an unguided drift for several worm cycles.
  15. Not Brilliant Guiding

    Correct. During calibration PHD2 works out which way is "up" and also how many pixels a given guide pulse will move the mount on each of the axes. I had a good look at Neil's guide log. The calibration on that one was quite poor but the latest one above looks ok. I could also see the periodic error with PemPro log viewer which indicates around 60" p-p - pretty much what one would expect from this mount. The polar alignment isn't great either. It looks like about 1 degree. A bit hard to be sure though due to the backlash in dec. I'd suggest to sort out the polar alignment then run the Guiding Assistant in PHD2 and follow its recommendations.
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