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Re: Spikes!
Yes, using my 178 it should be 0.35 when using the OAG. I have binned it in the past but found that it didn't seem to help, so I just leave it native.?
Using my 1600 it should be 0.55 according to https://astronomy.tools/calculators/ccd_suitability, it should be 0.55 because of the 0.7 reducer.
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I put in a focal length of 1471 in the PHD2 wizard. Which is not exactly the spec for the scope with the 0.7 reducer (1422). I did this because the solver complained that my calculated focal length was actually?1471, not?1422, so the image scale is slightly different than what astronomy.tools reports.??I think that I calibrated a few times as I was trying things out, so there should be several in there. Jamie ?
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Re: Spikes!
OK, one more before I turn in. This is with the scope on the East side instead of the West. I'm not sure what to make of it really. It's pretty bad for one, keeping above 2 RMS. The huge spikes are gone, and replaced with some large jumping around all over. -- Not really sure what to think about this. I'll try some of your ideas next night.? Jamie |
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Re: Spikes!
Michael, you are awesome!?
So I've already switched my guiding to use the main camera, a ZWO ASI 1600MM Pro, from the guide camera, which is a 178MC. So far things are looking much better, but I'm going to give it some time to make sure that the spike does not show up. When I was looking at the star profile in PHD2 on the previous (bad) runs, I would see the star do a huge jump in one frame, and my gut feeling was that the camera somehow decided to deliver a bad image, the very next frame was back into a fairly normal position. I also have a ZWO 120MM USB2 version and it will occasionally give a half image, or an image that is positioned wrong in the frame. This somehow reminded me of this, but again, it's some detective work, and lot's of guessing going on. One thing of note is that it 100% happens in RA, not DEC, so my guess with the camera might be completely wrong...? I'll let this play out for a while, and if I start to see the spikes again, I'll follow your advice.? -- OK, so I'm still seeing some spikes showing up. They don't look as high, maybe 9 instead of 13, but that might just be some math with the focal length and pixel size going on in the PHD2 test profile that I made for the 1600. There is absolutely still a spike. I believe that this only happens with the scope hanging to the west, and weights to the east. I'll have to re-arange and try.? We should absolutely get together sometime soon, regardless of this issue -- We're following some pretty strict covid rules though, so we keep to ourselves for now, but if things work out we may start loosening up in the next month or so.? It's getting late, so I'll have to continue with this the next night.? |
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Re: Spikes!
Dear Jamie, Let's try to chase the cause...a couple of simple things to try: 1. Balance the mount in RA and DEC. 2. Now unbalance the RA: Wrap a rope or cord around the RA axis so the string drops to the East, and hang a weight on that.? Say 1 to 2 pounds should do it. 3. Try imaging and look for the same glitches. If this remedies the glitch problem, the root cause is likely something in the RA drive... gear mesh gap.? There are several gaps that are built in.? The transfer gears have a gap (if you have a tucked motor system), and the worm to ring gear has a gap.? The hanging weight torque ensures the axis cannot shift during tracking and autoguilding.?? 4. If this does not do the trick, please switch from your SCT to a refractor just to test if the cause is really the mount.? If the refractor imaging shows no glitches, it's possible one of the mirror holders in the SCT is loose.? Or the dovetail plate is not tight, etc.?? It's always hard to chase these glitches down.? Reflective optics are prone to loose optical elements.? ?? All the best, Michael? (I'm in Sunnyvale this week, not too far from you...if you want to get together, let me know). On Thu, Apr 1, 2021, 10:55 PM Jamie Amendolagine <jamie.amendolagine@...> wrote:
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Spikes!
I've been having what is becoming a frustrating experience with large RA spikes. I've lost track of how many nights that I've focused on just getting guiding under control, maybe 5 or so. I've switched my setup from my APO to my SCT for galaxy season, so there's a bunch of recent changes, but all of the equipment was used before and performed pretty well. This exact setup has performed performed around 1.1 to 0.7 RMS, and this was before multistar-phd2. Right now I'm having a hard time keeping it below 2.0 RMS. There are some huge spikes (10 .. 14 or so) happening somewhat regularly, but not on a precisely regular schedule. Here's some examples of the time gaps between the spikes: 197s, 247,? 412, 485. The setup is an EdgeHD8 with a 0.7 focal reducer and an OAG. 178MC camera for guiding. I'm thinking of switching to the guide scope just to see what I can find. If everything is great there, then maybe there's some sort of flexure in the OAG image train.? I've gone through things carefully, making sure my PA is good, balance is good, wires are not snagging etc. Help!!! This is not the infamous 76 second spike is it??? It's such a strange spike, maybe there's something going weird with the camera? I'm going to try and guide with the main camera just to see what I see.? Help! |
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Re: 76 second RA periodic error fixed with Belleville washer
That additional computer interface is on my ever growing ToDo list!?? Actually, you can just use the ammeter to tell if the mount is balanced, which you tell by slewing CW and CCW on an axis...best with counterweights horizontal.? ? If the current is equal in both slew directions that axis is in balance.? ?Then running sidereal rate, the current does not change.? Say about 0.20 amps.?? If you unbalance it say with a hanging East side cord (I'm testing with 1 pound weight now on the G11T, and a pair of back to back soft Belleville soring washers in the Titan RA drive....working well), the current will go up a little. But still stays about 0.27 amps.? ? So looking at current vs time is not of value unless:? a gear jams.? Or a cable snags!? Etc etc.? So you use the motor current monitor to tell if your worm position is adjusted right.?? Autoguiding adds more pulses of power to the motors and the current goes up a little from that.?? Fast slewing on my systems can take about 0.6 amp per axis, but it is usually only about 0.7 amps during a Park to CWD from a large distance.? You can reduce the digital slew rate limit, and thus reduce the max motor current also.?? Here is a picture of the Titan RA running a C14 EdgeHD with 80 mm findervscooe on top, heavy camera and 0.7 massive FL reducer, Celestron OAG, and Nautilus filter wheel...about 82 lbs of counterweights.? Showing 0.29 amps draw just sidereal tracking with a 1 pound East side hanging weight.?? Anyway, the seeing is bad tonight...but maybe I can catch a galaxy from the light polluted back yard.? I was shooting the Hamburger galaxy in the Leo triplet last night.? That galaxy took up the entire frame of the APS- image chip on the QHY168C camera even with the FL reducer.? I started by trying to shoot in the center of the triplet and there was nothing there but a lone star...I did not realize the image size was so tiny on this system with FL ~2800 mm.? Oh well ...it's all for fun.? We are not going to beat Nasa.? ?? Stay well, Michael On Thu, Apr 1, 2021, 8:04 PM John Kmetz <jjkmetz54@...> wrote: Michael, |
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Still working out polar alignment on my mount
About polar alignment. So you do some pointing adjustments to the east and some pointing adjustments to the west. After four or five adjustments you get a different prompt and center the last star using manual adjustments on the mount. My issue is, sometimes my mount wants to slew to a star, that will cause my telescope to hit the tripod legs, and I have to stop it before it does. Then I don¡¯t know what to do from there. It's like the sequence is messed up and I have to start over. What do I do then? I have watched all the videos from Losmandy and any videos I can find from other people who use Losmandy mounts. I still can¡¯t seem to get the big picture. I still prefer my G11T, most of the time, but my Celestron mounts seemed easy to polar align by comparison.?
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Re: M81
Very pretty!!!! Nice work!! - Michael On Thu, Apr 1, 2021, 11:45 AM deitzelj via <deitzelj=[email protected]> wrote: Working my way up the software learning curve!? Reprocessed the original image. ? Turns out there is really color in there:-).? Interestingly I have a strange blue flare on the brightest stars, the source of which I need to track down, but generally I think it is a bit more representative.? Like I said in the earlier post, fix one thing, find some more:-). ? |
Jamie Amendolagine
Michael Herman
jeff marston