The reason I ask is what I see in PHD Log viewer is, which says 0.76", so in my mind I now take 0.76/2.2as/px = 0.38pixels on the imaging camera, which is great
I do see 0.5"/sec RA drift and 0.12" DEC in the drift tab but I didn't think I got to minus those off the total RMS
So I am just curious where the 0.25" comes from since I am already excluding dither variations here
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>>>
is this displayed in PHD Log viewer ?
yes, do just be clear i'm talking about the components of the guiding, not the?total guiding rms
If you have a perfect mount with 0 error, you are still limited by other conditions (seeing, wind, vibrations, hardware tilting)
i'm specifically talking about your notion of using PEMPro etc. to reduce the primary periodic error. in other words, what's the value of trying to implement PEC with your current setup
on your 3hr run, your PE for the primary is around 4.3" - FYI you'll notice your drift is much higher, but that's even easier to guide out
this PHD Log Viewer graph shows this:
That number is the calculated unguided PE
you can also choose to just analyze the guide data without backing out corrections:
here you can see your two peaks are both around 0.3" - in other words "residual error" i.e., what can't be guided out given your settings, configuration, hardware, etc.
The primary and 76 sec is prominent, but (here's the important part) they are both fractions of a pixel of your imaging camera.?
can you reduce those values using PEC? sure
will it make a difference? you're talking about error from PE going from maybe 1/3 of a pixel to maybe 1/4 or 1/8 of a pixel? you can decide if that's important to you ?
FYI I would give period length of 76.1s a try on PPEC and see how that goes. maybe drop your exposure time to 1-1.5sec
Yeah I think I get what you are saying (not sure how you can tell the "wasn't guided out" error -- where does that come from ?
If I have a 1" guide error then that will also be a 1" error In the imager (since we assume the scopes are moving together - assuming no flex)
Since I am 2.2 a/s in the imager, that would mean 1"/2.2 = 0.45 pixels and for my 0.76 error it would be 0.76/2.2 = 0.34 pixels
Now somehow you managed to come up with the? 1/4" "wasn't guided out" error but my RMS in the log was 0.76" total, so now I am curious about how you backed out the other approx 0.5" - is this displayed in PHD Log viewer ?
-- Brian?
Brian Valente portfolio
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Yeah I think I get what you are saying (not sure how you can tell the "wasn't guided out" error -- where does that come from ?
If I have a 1" guide error then that will also be a 1" error In the imager (since we assume the scopes are moving together - assuming no flex)
Since I am 2.2 a/s in the imager, that would mean 1"/2.2 = 0.45 pixels and for my 0.76 error it would be 0.76/2.2 = 0.34 pixels
Now somehow you managed to come up with the? 1/4" "wasn't guided out" error but my RMS in the log was 0.76" total, so now I am curious about how you backed out the other approx 0.5" - is this displayed in PHD Log viewer ?
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G11 and 6¡± f/10 for imaging?
I own a G11 and am considering putting together a 6¡± f/10 doublet for imaging the sun. Very high frame rate (>100 FPS) lucky imaging. I would put this on a very stout pier. Has anyone done anything similar??
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>>>so only if I decrease my imager scale Will I really need to care about this.? Don't get focused on the ratios and pixel sizes. The point is your error is in arseconds. Your "wasn't guided out" error on your main PE is 1/4"?
your image scale is 2.2" per pixel. that means that your guiding error is effectively 1/8th of a pixel on your imaging camera.? Personally I don't think you need to care about this at all until you are imaging at a finer resolution
Ah I think I see. Because my ratio of guide to image is about 3:1 then any error in the guider will be 1/3 in the imager
so the 15¡± PE is more like 5 and the 0.7 RMS is approx 0.7/3
This makes total sense.?
Even if I got 1.0 at DEC =0 I am still getting 0.3 or 0.4 RMS on the imager which is still less than a pixel
so only if I decrease my imager scale Will I really need to care about this.?
-- Brian?
Brian Valente portfolio
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Ah I think I see. Because my ratio of guide to image is about 3:1 then any error in the guider will be 1/3 in the imager
so the 15¡± PE is more like 5 and the 0.7 RMS is approx 0.7/3
This makes total sense.?
Even if I got 1.0 at DEC =0 I am still getting 0.3 or 0.4 RMS on the imager which is still less than a pixel
so only if I decrease my imager scale Will I really need to care about this.?
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Thanks Brian, that's awesome.
Sorry for my naive questions - just trying to get a baseline before I put a lot of time into getting data
Can you share how you came to those numbers ?
I was very happy with the guide log honestly but didn't really have much to compare it to (my Skyguider Pro logs would scare most people into quitting)
I really appreciate the help
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Nick
according to that 3 hour run, your primary PE is about 4.5" (removing corrections)
after guiding, the residual of your primary error is about 0.25"
Given your image scale, you are talking about less than 1/8th of a pixel error
I think this is not something to put time or effort into right now
Guider is 6.45 as/px
Main cam is 2.2 as/px
-- Brian?
Brian Valente portfolio
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Guider is 6.45 as/px
Main cam is 2.2 as/px
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Re: New G11 Question Concerning Stiction
I agree it can be a chore (and the video description offers some tips on how to ease that)
But if you mark it, you only really need to do it once.?
I like to set my weights and then pull the dec axis off via RA Extension kit so i don't even have to move them
While ALT = 0 is probably the most accurate, this method can be a bit of a chore. Cranking the altitude knob downwards is fairly easy, but turning back up to your latitude setting takes some significant torque and use of hand strength. When going up, the altitude bolt threads must lift the entire weight of payload plus counterweights and everything in between. Doing this a few times starts to get a bit tedious, especially if you start adding or removing gear. Plus every time you do this you lose whatever polar alignment adjustment that worked before, and you must start from scratch. Adding a wavy washer, plus swinging back and forth to judge balance, is a timer saver once you get used to it :).
-- Brian?
Brian Valente portfolio
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Nick what is your imaging scale again?
Yeah, this one has about a 3 hr guiding session at the end that overall I am extremely happy with. It was at Dec = 60 though and on another forum, someone pointed out that if I repeated this at dec=0 (have not done that yet) then I would likely see quite a bit worse guiding
As far as i can see, this is really good guiding (some occasional spikes at +/- 1.5 a/sec and I am not sure if that will be impacting the images or not) but otherwise it appears solid (to me)
I do need to adjust my settling pixel threshold in NINA as its set for my skyguider still and I can pull it in quite a bit from there
-- Brian?
Brian Valente portfolio
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Re: New G11 Question Concerning Stiction
While ALT = 0 is probably the most accurate, this method can be a bit of a chore. Cranking the altitude knob downwards is fairly easy, but turning back up to your latitude setting takes some significant torque and use of hand strength. When going up, the altitude bolt threads must lift the entire weight of payload plus counterweights and everything in between. Doing this a few times starts to get a bit tedious, especially if you start adding or removing gear. Plus every time you do this you lose whatever polar alignment adjustment that worked before, and you must start from scratch. Adding a wavy washer, plus swinging back and forth to judge balance, is a timer saver once you get used to it :).
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And this is a 10min sub from that session (toward the end).?
The elongated stars mostly in the top right are from some tilt I am dealing with
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Yeah, this one has about a 3 hr guiding session at the end that overall I am extremely happy with. It was at Dec = 60 though and on another forum, someone pointed out that if I repeated this at dec=0 (have not done that yet) then I would likely see quite a bit worse guiding
As far as i can see, this is really good guiding (some occasional spikes at +/- 1.5 a/sec and I am not sure if that will be impacting the images or not) but otherwise it appears solid (to me)
I do need to adjust my settling pixel threshold in NINA as its set for my skyguider still and I can pull it in quite a bit from there
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Nick i think you are munging a few different things together here that may confuse things
Do you have a guidelog segment that is at least 30 minutes of solid guiding (doesn't have to be low RMS, but does not have any issues, hiccups, poor calibraiton, etc.)
Apologies for the barrage of questions here.
I ran unguided for around 20 mins at DEC=0 (basically went to PHD2 drift align and told the mount to slew to where it wants to do that)
As others helped me understand, the Periodic error looked like around +7.5 to -7.5 which is a bit higher than I was expecting (potentially impacted by my guiding resolution)
I then went to DEC=60 (so maybe not a fair comparison) and did a multi-hour imaging test (with dithering) with PPEC enabled in PHD2
I imported the second log to PEC Prep and it seems to indicate that the PE was reduced to around +1.69 - -1.47 (see attached)
This seems very good (unless I am mis-understanding)
My questions.
1. Is that correct (based on attached images ?)
2. If I got PEM PRO and repeated this and actually programmed the mount, would I really see any benefit since it seems like PHD's PPEC basically already corrected the enite error out ? Wouldn't the PE in the mount just basically take on that portion of the PHD work ?
Sorry for the basic questions.
 
-- Brian?
Brian Valente portfolio
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Apologies for the barrage of questions here. I ran unguided for around 20 mins at DEC=0 (basically went to PHD2 drift align and told the mount to slew to where it wants to do that) As others helped me understand, the Periodic error looked like around +7.5 to -7.5 which is a bit higher than I was expecting (potentially impacted by my guiding resolution) I then went to DEC=60 (so maybe not a fair comparison) and did a multi-hour imaging test (with dithering) with PPEC enabled in PHD2 I imported the second log to PEC Prep and it seems to indicate that the PE was reduced to around +1.69 - -1.47 (see attached) This seems very good (unless I am mis-understanding) My questions. 1. Is that correct (based on attached images ?) 2. If I got PEM PRO and repeated this and actually programmed the mount, would I really see any benefit since it seems like PHD's PPEC basically already corrected the enite error out ? Wouldn't the PE in the mount just basically take on that portion of the PHD work ? Sorry for the basic questions.  
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Re: New G11 Question Concerning Stiction
That makes sense Brian. If it does not impact tracking then I dont care. Tracking is the only thing I am really interested in getting the best out of. I can use the alt=0 trick easily if need be.
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Re: New G11 Question Concerning Stiction
Nick,
The wavy washer goes in between the RA clutch plates and helps separate them when the locks are untightened. Unless you are at the equator, the altitude your mount is set at will always cause some large fraction of the mount weight to push down on the plates, creating stiction/friction. These mounts don't free wheel like some other brands but this is normal. The wavy washer helps with stiction, but does not eliminate it. If you gently swing the mount back and forth you will get a feel for the balance point.
Most folks go for a slight East heavy balance in RA, and a slight camera/eyepiece heavy balance in Dec. You don't want to be perfect, but want a slight imbalance to get the worm and ring gears to ride on one side of the gear faces, not jump back and forth to create backlash.
If you crank the ALT down to zero, that takes most of the weight off the RA clutches. But use caution as the center of mass is less over tripod center, and you can get tippy and flop over if the mount is bumped or is too far offset.
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Re: New G11 Question Concerning Stiction
Hi Nick
You only need to find balance once, so the ALT=0 trick is a good one
the wavy washer can certainly help though it is totally unrelated to tracking
I've watched all the videos (and going to watch this one again). My rig is light but I do find that its really difficult to "unbalance" it by moving the weight up and down
I got the 7 pound weight since the rig is light.
If I use just the CW bar and put it horizontal and let go, it does seem a bit stiffer to move than I would have imagined.
How does one know they need such a washer and does it help overall tracking significantly ?
?
-- Brian?
Brian Valente portfolio
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Re: New G11 Question Concerning Stiction
I've watched all the videos (and going to watch this one again). My rig is light but I do find that its really difficult to "unbalance" it by moving the weight up and down
I got the 7 pound weight since the rig is light.
If I use just the CW bar and put it horizontal and let go, it does seem a bit stiffer to move than I would have imagined.
How does one know they need such a washer and does it help overall tracking significantly ?
?
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