Re: AP1100 Bad Stars Issues


Bill Long
 

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/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 5:13 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@... <mailto: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] > 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] <ap-
> gto@...>
> To: 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]
> 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] > 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.
>
>
>
>
>
>
>
>
>
>
>
>
>
>

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