Mach1GTO - Crazy calibration with PHD2
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Samara Nagle
Hello everyone, this is my first post here. I am the new owner of a Mach1GTO puchased last Christmas. Love my mount but don't get to use it often because of the horrible weather here in Ohio. Last night I woke up very early and it was clear so I decided to just play a little bit, ended up with another problem to troubleshoot. PHD's calibration was all over the place, which is something that never happened to me with any mount. The mount is permanently set in it's pier in my observatory in the backyard and since I bought it I never moved it. There are no cables snagging because I have a Rigrunner and USB hub sitting on top of the OTA and only 2 cables coming out of the mount, power and USB and those are very well anchored. The scope is a Celestron Edge 11" and the mirrors are locked because I use a Moonlite Crayford focuser. Anyway, I am a little lost here and the only thing I noticed different is that there's now a little bit of RA play. Any suggestions? I'll try to add the screenshot of the problem to the Photos area. Thank you! |
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Samara Nagle
Pictures in album called Mach1 GOT - PHD Calibration issues
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Roland Christen
1) You might want to place the camera at right angles to the RA/Dec direction.
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2) You are apparently trying to guide at 0.5x guide rate. All our mounts work best at 1x guide rate. The slower rates are for manual guiding. 3) RA backlash has no effect on guiding. Rolando -----Original Message-----
From: samara_c@... [ap-gto] To: ap-gto Sent: Wed, Apr 26, 2017 9:48 am Subject: [ap-gto] Re: Mach1GTO - Crazy calibration with PHD2 Pictures in album called Mach1 GOT - PHD Calibration issues |
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Samara Nagle
Rolando,
Thank you. I will check the guiding camera for orientation. It is good to know that the mount works best at 1 x guide rate, it's not what I have been using but in this case I actually tried both, 0.5 x and 1 x. I will definitely change it permanently to 1 x. The problem happened out of nowhere, last time I imaged everything worked fine and than I spent several weeks without imaging because of the weather and then last night this happened. I didn't know the orientation of the guide camera mattered, I will definitely double check. Thanks again! |
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Leo Shatz
I'm following this post as a new user of Mach1 after upgrading from EQ6 mount. I also used to guide at 0.5 rate and didn't consider to align my guidescope with ra/Dec grid. I'd like to know some explanation behind the suggestion to align the guider with RA/Dec axes. When guiding star moves in different directions, the scattering pattern is random in all possible directions, and corrections are applied independently on both axes, so why orientation matters? Thanks, Leo S. On Apr 26, 2017 7:40 PM, "samara_c@... [ap-gto]" <ap-gto@...> wrote:
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Roland Christen
Orienting the camera with respect to RA/DEC is not absolutely necessary. It does make calibration somewhat easier to understand and eliminates one more variable when trying to solve a problem.
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Rolando -----Original Message-----
From: samara_c@... [ap-gto] To: ap-gto Sent: Wed, Apr 26, 2017 11:40 am Subject: [ap-gto] Re: Mach1GTO - Crazy calibration with PHD2 Rolando, Thank you. I will check the guiding camera for orientation. It is good to know that the mount works best at 1 x guide rate, it's not what I have been using but in this case I actually tried both, 0.5 x and 1 x. I will definitely change it permanently to 1 x. The problem happened out of nowhere, last time I imaged everything worked fine and than I spent several weeks without imaging because of the weather and then last night this happened.
I didn't know the orientation of the guide camera mattered, I will definitely double check.
Thanks again!
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Leo Shatz
Thanks, Rolando.
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This makes sense now. While speaking about PHD2 guiding, is there a short summary of PHD2 starting settings recommended for this mount ? My friend had suggested that I probably should use hysteresis guiding algorithm for DEC axis instead of the default resist-switch, also use lower aggressiveness of RA hysteresis algorithm of 60 instead of 70. Thanks, Leo
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Roland Christen
I'm not very familiar with PHD, so I suggest going on their user group. Lots of knowledge there.
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Rolando -----Original Message-----
From: Leonid Shatz leonid.shatz@... [ap-gto] To: ap-gto Sent: Wed, Apr 26, 2017 1:18 pm Subject: Re: [ap-gto] Re: Mach1GTO - Crazy calibration with PHD2 Thanks, Rolando. This makes sense now. While speaking about PHD2 guiding, is there a short summary of PHD2 starting settings recommended for this mount ? My friend had suggested that I probably should use hysteresis guiding algorithm for DEC axis instead of the default resist-switch, also use lower aggressiveness of RA hysteresis algorithm of 60 instead of 70.
Thanks,
Leo
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Michael Fulbright <mike.fulbright@...>
Honestly if your DEC gear mesh is reasonably set then I doubt it
matters much what you use for DEC. I've always used the default in
PHD2 - I think it is 'Auto' where it works it out.
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If you had a mount with considerable DEC backlash it then would make a big difference. In that case you purposely polar misalign slightly so there is a definite drift in one direction for DEC and PHD2 would work it out (using Resist Switch) and only guide in one direction in DEC. Easiest way I've found to figure out guiding parameters is first set the DEC aggressiveness to 0 and watch the behavior of the mount. Then slowly ramp up aggressiveness and watch the guide graph (enable showing corrections as well) and see how well the guiding corrects for DEC drift. Keep incrementing aggressiveness until you converge on consistent good corrections. Michael Fulbright On 4/26/2017 2:36 PM, chris1011@...
[ap-gto] wrote:
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Andy Galasso
Leo, The link to the PHD2 User group can be found on the PHD2 site here: Getting Help. There is also a PHD2 Best Practices guide on the PHD2 site you may find informative. Andy |
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Roland Christen
First you need a good calibration run. Many don't understand what calibration does, but it's really a simple concept. The guide software looks at the position of a star and then commands a move (1x sidereal is recommended) for a specific amount of time, let's say 10 seconds. Theoretically the Dec axis will always move 150 arc seconds in that period of time (15 arc sec/sec), RA will move the same if you are calibrating at the celestial equator. The software then looks at the new position of the star and determines how many pixels corresponds to 150 arc sec. It uses that to calculate the number of pixels for a 1 second guide command.
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If your focal length is such that 1 pixel = 1 arc sec, then the RA and Dec parameter numbers will be 15. Consequently if the guide star is off by 15 pixels, the guide software sends a command to move at 1x for 1 second in the opposite direction, thus sending the star towards the zero line. The calibration routine simply is used to determine how many pixels a star will move in a given amount of time, as well as the direction in either axis. Theoretically one does not even have to do a cal run for the parameter numbers, just simply figure out what your pixel scale is and enter that into the software. The direction and angle, of course, are not known until you do the run, but if you never change the camera orientation, this will always remain the same. Rolando -----Original Message-----
From: Michael Fulbright mike.fulbright@... [ap-gto] To: ap-gto Sent: Wed, Apr 26, 2017 2:03 pm Subject: Re: [ap-gto] Re: Mach1GTO - Crazy calibration with PHD2 Honestly if your DEC gear mesh is reasonably set then I doubt it matters much what you use for DEC. I've always used the default in PHD2 - I think it is 'Auto' where it works it out. If you had a mount with considerable DEC backlash it then would make a big difference. In that case you purposely polar misalign slightly so there is a definite drift in one direction for DEC and PHD2 would work it out (using Resist Switch) and only guide in one direction in DEC. Easiest way I've found to figure out guiding parameters is first set the DEC aggressiveness to 0 and watch the behavior of the mount. Then slowly ramp up aggressiveness and watch the guide graph (enable showing corrections as well) and see how well the guiding corrects for DEC drift. Keep incrementing aggressiveness until you converge on consistent good corrections. Michael Fulbright On 4/26/2017 2:36 PM, chris1011@...
[ap-gto] wrote:
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Leo Shatz
Thanks, Michael for your comments! I agree that considerable backlash can be source of some headache, in that case I'm not sure if backlash compensation can clean it, but guiding in one direction would be certainly an option. For the mount with small dec backlash, I would indeed try to use hysteresis algorithm, as with resist switch it will change direction only waiting 3 periods above min Dec movement threshold. I also learned from my friend that sometimes he increases the min move on one axis to match RMS on another one, for the sake of stars roundness. Leo On Apr 26, 2017 10:03 PM, "Michael Fulbright mike.fulbright@... [ap-gto]" <ap-gto@...> wrote:
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Leo Shatz
Rolando, Yes indeed. I usually select smaller calibration pulse duration to allow more steps for additional precision, and then check orthogonality graph in PHD tool window. On Apr 26, 2017 10:16 PM, "chris1011@... [ap-gto]" <ap-gto@...> wrote:
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My 2 cents having a new Mach 1 and struggling a bit before i did the following:
Make sure you have the latest version of PHD2 downloaded, then in Phd2 before you run any calibration, you should of course properly polar alignment the mount. You probably have because of your permanent setup but things sometimes get out of wack. Second thing is I would recommend is restore all default settings in PHD and start from scratch. Use the new profile wizard and enter in all of your information about your guide camera, guiding focal length etc. Then point your scope at a star near the meridian and celestial equator and run the Guiding Assistant. Let the GA run for a few worm cycles ( Mach 1 I believe is a bit over 6 minutes per cycle) so 10-15 minutes later hit the stop button and let it do the backlash test. After all this is said and done use all the Guiding Assistant's recommend settings and apply them. This will give you a great idea of you actual polar alignment should it need adjusting. This will also give you a nice baseline for settings with your setup. Only small tweaks to the settings if any at all will be needed. I did this and have had very very excellent results using the new Mach1 and PHD2. Good luck Dan |
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Pawel Lancucki
As the mount has undergone several heat
/ cold cycles, I would recommend to check tightness of various screws and
bolts, dovetail saddle etc..
Also, if you are using a guiding cable, check / replace it. In my experience the endurability of these little RJ plugs and cables is much less than any other part of our astro gear. CS Pawel Lancucki |
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Samara Nagle
I followed everyone's suggestions between here and the AP Yahoo forum.
Downloaded new version of PHD Pointed the scope to Zenith and released the mirror locks and let the mirror sit and tighten the mirror locks again. Checked all bolts and screws Changed the orientation of the guide camera to be orthogonal with everything else Created a brand new profile in PHD making sure I have the right FL and left all the other settings as default Ran the guide assistant Changed guiding rate from 0.5x to 1x
Calibration looked a little better, DEC still showing some odd behavior but after a while the star just moves completely out of the target, I can see where the star is, it's moving a lot, which makes me think that either something on the mount or somewhere else in the imaging train is moving with gravity. I am lost with this one, I guess all I can do when I have another clear night is now get me a new USB cable for the Lodestar and try to fix the play in RA. I will keep everyone posted if I ever find the solution to this problem.
P.S.: The picture attached in the same album is from the first night, last night when I was guiding my star ended up exactly on the same location. |
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Leo Shatz
Samara, I'd suggest you to upload the PHD2 guiding log to PHD forum, I'm sure you'll get some helpful feedback. Leo On Apr 27, 2017 2:16 PM, "samara_c@... [ap-gto]" <ap-gto@...> wrote:
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dave@...
how long do u let calibration run?
When u calibrate, what side of the meridian is your ota on? east and pointing west or ota in the west, pointing east? Do you then flip and try your guiding test? during your guiding test, are the counterweights above the ota? Dave i follow Ray's guiding params. 1x and let calibration run 50-75% of the chip. for my 130gtx thats a 60sec calibration run per axis. |
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Few follow up questions:
Where was the scope pointing when you ran the Guiding Assistant? How long did the GA run before you stopped it? Did the backlash test run? Did you apply all the GA's recommended settings? What did it say your Polar Alignment error was? Fwiw: I once had a problem with guiding and couldn't figure it out. So I ran the Guiding Assistant to see what it said. It said my Polar Alignment was off by a few arc minutes. I said 'No way' I was accurately polar aligned within 30 arc seconds. So I re-checked my Alignment and sure enough it was off. Apparently my tripod led settled in the ground and threw off my PA and in turn also my guiding. The GA is a PhD user's best friend. If you submit your situation on the PhD Google group. Bruce will more than likely tell you to do what I did in my previous post. Best of luck Dan |
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Roland Christen
If you are getting a proper calibration, that means that the mount is following the input commands, so nothing wrong with your connection from the imager to the mount.
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If you have pier flip checked, then the guide software will indeed drive the star off the chip. That's because one of the axes is being given the opposite command, opposite to what is needed to drive the star to the middle of the chip. Rolando -----Original Message-----
From: samara_c@... [ap-gto] To: ap-gto <ap-gto@...> Sent: Thu, Apr 27, 2017 6:16 am Subject: [ap-gto] Re: Mach1GTO - Crazy calibration with PHD2 I followed everyone's suggestions between here and the AP Yahoo forum.
Downloaded new version of PHD
Pointed the scope to Zenith and released the mirror locks and let the mirror sit and tighten the mirror locks again.
Checked all bolts and screws
Changed the orientation of the guide camera to be orthogonal with everything else
Created a brand new profile in PHD making sure I have the right FL and left all the other settings as default
Ran the guide assistant
Changed guiding rate from 0.5x to 1x
Calibration looked a little better, DEC still showing some odd behavior but after a while the star just moves completely out of the target, I can see where the star is, it's moving a lot, which makes me think that either something on the mount or somewhere else in the imaging train is moving with gravity. I am lost with thi
s one, I guess all I can do when I have another clear night is now get me a new USB cable for the Lodestar and try to fix the play in RA. I will keep everyone posted if I ever find the solution to this problem.
 P.S.: The picture attached in the same album is from the first night, last night when I was guiding my star ended up exactly on the same location.
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