Re: AP1100 Bad Stars Issues


Joe Zeglinski
 

Ray,
 
    On your point of occasionally “seeing east/west side PE”  differences.
 
    Could that be attributed to a minor, possibly intentional,  OTA imbalance causing the worm and worm wheel rubbing on one surface if “pulling” its weight upward, compared, to rubbing on their “opposite faces”,  if holding back the now falling weight of the OTA, on the flip side?
 
    Since even the gear box spur gears aren’t perfect, requiring a PEM correction - should we then assume that BOTH sides of any worm,  or its worm wheel, were cut & ground  perfectly smooth and symmetrical? In the final analysis, there will be at least 6 upto maybe 10 full worm revolutions during a PEM curve creation – and the curve surely would have to be very slightly different, owing to the “directly opposite, east side vs. west side gear faces”  being in contact. Add to that, the mount axle would have been de-clutched and rotated by the user,  at some point in time, so the curve for that test gear section of 6 consecutive worm wheel surfaces,  can change completely.
 
    So, to be closer to perfection, one could consistently choose only one side of the pier in establishing a curve, and redo the curve if the mount is declutched, and repositioned manually, to a different spot on the worm & wheel. But then, the PEM is just an average fix anyway, since if there are worm & wheel surface variations, over a 180 degree span of sky tracking, there will still be spots that don’t quite match the programmed  compensation PEM curve.
 
    End result, I am not surprised in seeing east vs. west side PEM curve differences. Perhaps a separate east & west side run curve could be averaged, in a final PEM curve.
But that’s probably going way over the top.
 
Just a thought.
Joe
 

From: 'Ray Gralak (Groups)' groups3@... [ap-gto]
Sent: Sunday, February 25, 2018 10:15 AM
To: ap-gto@...
Subject: RE: [ap-gto] AP1100 Bad Stars Issues
 
Hi Bill,

< SNIP >

I have seen slightly different PE's on each side of the pier with my 1200GTO,
which might have to do with balance.
Best regards,

-Ray Gralak
Author of APCC (Astro-Physics Command Center):
http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
Author of PEMPro:  http://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: http://www.gralak.com/apdriver
Author of PulseGuide: http://www.pulseguide.com
Author of Sigma: http://www.gralak.com/sigma


> -----Original Message-----
> From: ap-gto@... [mailto:ap-gto@...]
> Sent: Saturday, February 24, 2018 9:35 PM
> To: ap-gto@...
> Subject: Re: [ap-gto] AP1100 Bad Stars Issues
>
>
>
> The image scale was correct. I ran the wizard that set the scale accordingly.
This mount is
> two years old now, so perhaps the error now is what it is. I dont personally
care what it is,
> as long as it can be corrected. What I do care about is being called out for
somehow
> damaging the brand of AP, when in reality what I said was not false at all.
The measured
> error in my mount was close to 9" as I said. Not because I felt it appropriate
to say things
> that were unfounded at all. I didn't spend this kind of money to be treated
like that. Not
> your problem, Ray, you have been very supportive and I appreciate that.
>
>
>
>
> I can image on the east side of the meridian, but in terms of the equator I
have to move
> higher than that in the sky due to trees that block my FOV in the south skies.
>
>
>
> ________________________________
>
> From: ap-gto@... on behalf of 'Ray Gralak
> (Groups)' groups3@... [ap-gto]
> Sent: Saturday, February 24, 2018 8:03 PM
> To: ap-gto@...
> Subject: RE: [ap-gto] AP1100 Bad Stars Issues
>
>
>
> Hi Bill,
>
> > While, I do not
> > understand any of this as well as a physicist, is 8.9" of P-P error
> > within
> spec?
>
> If the image scale was incorrect for any reason then the scaling of the curve
would be
> wrong. However, if the created curve removed the periodic error as well as it
looks then
> the periodic error probably was correct.
>
> Looking at the original data it looks like the worm has about 8 arc-secs of PE
and the
> residual is caused by a 4x fundamental. Over time it is likely that the
measured periodic
> error will change, but it usually gets better rather than worse. That said, I
have seen logs
> showing an alarming increase in periodic error in a couple Paramount's that
had heavy
> telescopes mounted on them.
>
> Just out of curiosity can you try measuring PE on East side of the meridian
(with PE
> disabled)?
>
> -Ray Gralak
> Author of APCC (Astro-Physics Command Center):
> http://www.astro-physics.com/index.htm?products/accessories/software/apcc/apcc
> Author of PEMPro: http://www.ccdware.com Author of Astro-Physics V2 ASCOM
Driver:
> http://www.gralak.com/apdriver Author of PulseGuide: http://www.pulseguide.com
Author
> of Sigma: http://www.gralak.com/sigma
>
> > -----Original Message-----
> > From: ap-gto@... [mailto:ap-gto@...]
> > Sent: Saturday, February 24, 2018 5:42 PM
> > To: ap-gto@...
> > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> >
> >
> >
> > Yeah I did not think that the PEM ON data I had was a good enough set
> > to do
> anything
> > with. Way too limited. That is why I did not try, but I was told to go
> > do some
> simple
> > analysis on it, and that was the only result I could come up with.
> >
> >
> >
> >
> > I did actually walk back through my steps that night I obtained the
> > data,
> which for the
> > record was the first time I have ever used PEMPro. The curve in the
> > mount now,
> was
> > actually inverted. The first test I ran showed 10" of error (you have
> > the logs
> from that, Ray)
> > that's when I inverted the curve and replayed it to the mount. Then I
> > took the
> limited data
> > that is being discussed here, but did not have the boxes checked for
> > drift,
> and saw the 5"
> > of error and assumed I just had bad data and would try again another
> > time. My
> bad.
> > Rookie mistake.
> >
> >
> >
> >
> > Anyhow, I am more than happy to get 4 cycles of data to see how it
> > comes out
> with PEM
> > enabled. I think that is a fair ask and due diligence.
> >
> >
> >
> >
> > Can I ask a question (without my intelligence being attacked again) here?
> While, I do not
> > understand any of this as well as a physicist, is 8.9" of P-P error
> > within
> spec? That is not
> > me trying to be mean, rude, or whatever. Regardless of how well PEMPro
> > can
> correct that,
> > is that legitimate for the product? The sheet I looked at says +/-
> > 3.5" which
> I would assume
> > (again, you guys are the pros, I am the consumer) is 7" P-P.
> >
> >
> >
> > ________________________________
> >
> > From: ap-gto@... on behalf of
> > 'Ray Gralak (Groups)' groups3@... [ap-gto]
> >
> > Sent: Saturday, February 24, 2018 5:26 PM
> > To: ap-gto@...
> > Subject: RE: [ap-gto] AP1100 Bad Stars Issues
> >
> >
> >
> > Hi Bill,
> >
> > I don't think that curve is representative if you couldn't use drift
fitting.
> >
> > The data you posted looks like there was virtually no periodic error.
> >
> > -Ray Gralak
> > Author of APCC (Astro-Physics Command Center):
> > http://www.astro-physics.com/index.htm?products/accessories/software/a
> > pcc/apcc Author of PEMPro: http://www.ccdware.com Author of
> > Astro-Physics V2 ASCOM
> Driver:
> > http://www.gralak.com/apdriver Author of PulseGuide:
> > http://www.pulseguide.com
> Author
> > of Sigma: http://www.gralak.com/sigma
> >
> > > -----Original Message-----
> > > From: ap-gto@... [mailto:ap-gto@...]
> > > Sent: Saturday, February 24, 2018 5:13 PM
> > > To: ap-gto@...
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > > https://groups.yahoo.com/neo/groups/ap-gto/files/PEM%20ON.JPG
> > >
> > >
> > >
> > >
> > > Here is the curve made from the limited PEM ON data.
> > >
> > >
> > >
> > > 2.55 P-P Arc Second. The only drift fitting that showed any error was
"None"
> > though, so I
> > > am not sure how accurate this is.
> > >
> > >
> > > ________________________________
> > >
> > > From: Bill Long
> > > Sent: Saturday, February 24, 2018 3:36 PM
> > > To: ap-gto@...
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > > Well, where PEMPro wanted me to point, and stay in the green per the
> > > PEMPro
> > Wizard
> > > was blocked by a tree, so I had to slew a bit further west to get
> > > clear
> skies.
> > Perhaps that
> > > has something to do with the drift?
> > >
> > >
> > >
> > > ________________________________
> > >
> > > From: ap-gto@... on behalf of
> > > chris1011@... [ap-gto]
> > > Sent: Saturday, February 24, 2018 2:35 PM
> > > To: ap-gto@...
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > > The curves you posted line up because PEMPro has lined them up for
> > > you when
> > you
> > > clicked on the X and Y alignment tabs. You had mentioned in the
> > > PEMpro
> > postings that
> > > they did not line up and Ray pointed out that you had drift. That
> > > drift is an
> > indication that
> > > your polar alignment is not correct, it shows RA drift. When you
> > > have RA
> > drift, you cannot
> > > expect round stars regardless of mount PE.
> > >
> > >
> > >
> > > I will spend the 30 mins or so to get some fresh PEMPro PE data as
> > > well
> > to see if
> > > there is any difference.
> > >
> > > Why bother, you already have less than 1 arc sec performance. What
> > > do you
> > expect to
> > > achieve with yet another PEMPro run? Your tracking with PEM on is
> > > essentially
> > perfect. If
> > > you do a simple analysis of the PEM on data that you posted, you
> > > will probably
> > find that
> > > the periodic error is on the order of 1/2 arc second. You will not
> > > exceed that
> > and can only
> > > get the same or worse.
> > >
> > > Ray, can you do a quick analysis of that PEM-on run and post the
> > > resultant PE
> > curve?
> > >
> > > Roland Christen
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Bill Long bill@... [ap-gto]
> > > To: ap-gto
> > > Sent: Sat, Feb 24, 2018 3:17 pm
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > >
> > > The PEM ON test needs to be run still, next clear night I plan to do that.
> > >
> > > When I took my PE data, the curves seem to line up well. Here is
> > > what they
> > looked like:
> > >
> > > https://groups.yahoo.com/neo/groups/ap-gto/files/PEMPro%20Error.JPG
> > >
> > >
> > > Do those look egregious to you?
> > >
> > > As far as Polar Alignment is concerned, I used the Polemaster tool
> > > and ran it
> > through 3
> > > complete cycles to confirm its suggested alignment. Ray suggested I
> > > check that
> > alignment
> > > with PEMPro the next time I am out. I will spend the 30 mins or so
> > > to get some
> > fresh
> > > PEMPro PE data as well to see if there is any difference.
> > > > > > >
> > >
> > >
> > >
> > > ________________________________
> > >
> > > From: ap-gto@... on behalf of
> > > chris1011@... [ap-gto]
> > > Sent: Saturday, February 24, 2018 12:34 PM
> > > To: ap-gto@...
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > > What is the PEC curve with PEM turned ON? That is what you will be
> > > using
> > during
> > > tracking.
> > >
> > > When you took your PE data, you said that the individual curves did
> > > not lie on
> > top of each
> > > other, rather they moved up with each new worm cycle. That should
> > > tell you
> > immediately
> > > that your polar alignment is not good, and you have excessive RA
> > > drift. When
> > your polar
> > > alignment is correct (Altitude axis properly aligned), you will
> > > basically have
> > zero RA drift
> > > and each curve will lie on top of the next, or very close to it.
> > > Then with PEM
> > turned on, you
> > > should be able to get no tracking error for several worm cycles when
> > > you are
> > anywhere
> > > near the meridian.
> > >
> > > When you have RA drift, or Dec drift for that matter, you will never
> > > have
> > round stars even
> > > when the mount is tracking to 1 arc sec levels with PEM on. RA drift
> > > is
> > independent of
> > > periodic error and has nothing to do with mount tracking at sidereal
> > > rate. A
> > perfect mount
> > > with zero PE will have egg shaped stars if you have drift in either axis.
> > >
> > > Roland Christen
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Bill Long bill@... [ap-gto]
> > > To: ap-gto
> > > Sent: Sat, Feb 24, 2018 2:16 pm
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > >
> > > https://groups.yahoo.com/neo/groups/ap-gto/files/PEMPro_Curve.JPG
> > >
> > >
> > >
> > > ________________________________
> > >
> > > From: ap-gto@... on behalf of
> > > chris1011@... [ap-gto]
> >
> > > Sent: Saturday, February 24, 2018 12:07 PM
> > > To: ap-gto@...
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > > Maybe I'm missing something, but I see only the raw data, not the PEC
curve.
> > Can you
> > > point it out?
> > >
> > > Rolando
> > >
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Bill Long bill@... [ap-gto]
> > >
> > > To: ap-gto
> > > Sent: Sat, Feb 24, 2018 2:04 pm
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > >
> > > That is all located here:
> > >
> > >
> >
>
http://ccdware.infopop.cc/eve/forums/a/tpc/f/401101098/m/8577004986?r=5087004986
> > #50
> > > 87004986
> > >
> > >
> > >
> > >
> > >
> > > ________________________________
> > >
> > > From: ap-gto@... on behalf of
> > > chris1011@... [ap-gto]
> > > Sent: Saturday, February 24, 2018 11:59 AM
> > > To: ap-gto@...
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > >
> > > I sent another mail correcting my original statement. I had some
> > > more
> > coffee, then
> > > read it again. Ray had a look at the curve via the PEMPro forums and
> > > I think
> > we are good
> > > to go on that front.
> > >
> > > You posted two raw PEMPro runs, but no analysis of the actual PE
> > > value. Your
> > estimate
> > > of 9 to 10 arc sec P-P is not backed by actual analysis. Please post
> > > the
> > actual PE as
> > > analyzed by PEMPro so that people who read these posts do not get
> > > the false
> > impression
> > > that we ship mounts that are out of spec. The value that defines the
> > > mount's
> > PE is created
> > > when you press the tab "Create a PEC Curve". You will see in the
> > > upper right
> > the value of
> > > the mount's periodic error in +- arc seconds.
> > >
> > > Roland Christen
> > > Astro-Physics Inc.
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Bill Long bill@... [ap-gto]
> > >
> > > To: ap-gto <ap-gto@...>
> > > Sent: Sat, Feb 24, 2018 12:52 pm
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > >
> > > I sent another mail correcting my original statement. I had some
> > > more coffee,
> > then read it
> > > again. Ray had a look at the curve via the PEMPro forums and I think
> > > we are
> > good to go
> > > on that front.
> > >
> > > I will test this again, with PEMPro enabled and guiding running. I
> > > suspect
> > that my results
> > > will be better. Thanks for the info about expectations for
> > > non-guided
> > exposures.
> > >
> > > ________________________________
> > >
> > > From: ap-gto@... on behalf of
> > > chris1011@... [ap-gto] <ap-gto@...>
> > > Sent: Saturday, February 24, 2018 10:44 AM
> > > To: ap-gto@...
> > > Subject: Re: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > >
> > > The last one I ran was close to 9" P-P. This is almost 3 times the
> > published
> > > specification of +/- 3.5" without any error correction.
> > >
> > > First of all, 9" P-P is only 28% larger than +- 3.5". The error of 9"
> > > P-P is
> > equal to +- 4.5 ".
> > >
> > > I believe you misunderstand what periodic error is and how it is
> > > measured and
> > specified.
> > > A screen capture of the PEMPro run would be helpful, along with the
> > > PEMPro
> > analysis of
> > > Periodic error. Remember, when you are doing a PEMPro run on the
> > > sky, the raw
> > data
> > > also contains errors caused by atmospheric seeing. These can easily
> > > add 3 arc
> > sec or
> > > more to your raw data. PEMPro analysis removes these non-periodic
> > > errors
> > caused by
> > > seeing, drift, etc and provides the true mount tracking performance.
> > >
> > > I saw your images that you sent and they looked normal to me and
> > > George. The
> > 15 sec
> > > images had perfectly round stars, consistent with typical winter seeing.
> > >
> > > I would never expect unguided images to be round for a number of
> > > reasons, none
> > of which
> > > are mount related. In other words, even if the mount tracked
> > > perfectly, I
> > would not expect
> > > round star images in an unguided exposure of any normal length.
> > >
> > > A better indication of performance is the RMS value of your guiding,
> > > using one
> > of the
> > > popular guiding programs (MaximDL or PHD). You can use these
> > > programs to
> > determine
> > > the base level of atmospheric seeing errors and the resultant guided
> > performance in arc
> > > sec RMS. During guiding, when the RMS values of RA and Dec are close
> > > to equal,
> > you
> > > will have round stars on your images.
> > >
> > > Rolando
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: Bill Long bill@... [ap-gto]
> > >
> > > To: ap-gto
> > > Sent: Sat, Feb 24, 2018 12:07 pm
> > > Subject: [ap-gto] AP1100 Bad Stars Issues
> > >
> > >
> > >
> > >
> > > Hello all,
> > >
> > > I have contacted A-P about some recent imaging challenges I have
> > > had, and have provided details to George on this problem, but I
> > > wanted to get some thoughts
> > from the
> > > folks here on this forum as well, in the event someone has
> > > experienced a
> > similar problem.
> > >
> > > Problem Statement:
> > > Out of round stars in 15 and 30 second unguided exposures, on two
> > > different
> > cameras.
> > > Out of round Stars in 60 second, 120 second, and 300 second guided
> > > exposures
> > on one
> > > camera.
> > >
> > > Possible Red Herring or Evidence for Concern:
> > > I have run PEMPro and the readings of periodic error are wildly
> inconsistent.
> > I get up to
> > > 10" P-P of RA error. The last one I ran was close to 9" P-P. This is
> > > almost 3
> > times the
> > > published specification of +/- 3.5" without any error correction.
> > >
> > > Polar Alignment Method:
> > > Polemaster, 3 complete cycles per alignment, repeatable results.
> > >
> > > Gear:
> > > Stellarvue 80mm Refractor w/ SV80 Field Flattener Takahashi FSQ106ED
> > > Native w/
> > no
> > > reducer Takahashi TOA130 w/ 0.7x Tak Reducer
> > > AP1100 GTO CP4 w/ Auto-Adjusting Gearbox ASI 183MM Pro CMOS Camera
> > > ASI 294MC Pro CMOS Camera
> > >
> > > Software:
> > > APCC Pro
> > > ASCOM v2 AP Driver
> > > Sequence Generator Pro
> > >
> > > All cameras tested were properly spaced on each respective scope. I
> > > have
> > performed
> > > testing with a wheel and OAG attached, as well as without any wheel
> > > or OAG
> > attached,
> > > and spacers in place of them to ensure accurate chip placement.
> > > Using CCDWare
> > CCD
> > > Inspector 2, both cameras are reported to be showing 20% tilt. As a
> > > test, I
> > enabled guiding
> > > and set the RA settings very, very aggressively and while the
> > > problem did not
> > completely
> > > cure itself, the roundness of the stars improved dramatically, and
> > > tilt was
> > reported to be
> > > reduced to 2%.
> > >
> > > The cameras could be involved in the problem, I am not ruling that
> > > out, but to
> > have very
> > > similar results on two different cameras is suspicious, and if there
> > > is a way
> > to rule out the
> > > one constant in all of this testing (the mount) I would like to do that.
> > >
> > > The mount is not permanently mounted. I set up and tear down each
> > > night I
> > image. The
> > > axis are separated and reassembled when the mount goes outside, and
> > > when it
> > comes
> > > back inside each night. In case this information is useful.
> > >
> > > Thanks for reading.
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
> >
>
>
>
>



------------------------------------
Posted by: "Ray Gralak \(Groups\)"
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