Re: Spikes in DEC #guiding #Guiding


Roland Christen
 

So, were you imaging with the dewshield off and unbalanced?

Rolando


-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Wed, May 5, 2021 11:31 am
Subject: Re: [ap-gto] Spikes in DEC #guiding #guiding

Hi,

For reference, I did calibrate near M3 which was the nearest I could get from the celestial equator/meridian at the time, given high trees that obstruct my sight in the south. 

But guess what, it seems Brian, Howard and Roland were right from the very beginning. (Who would have thought? Silly me...)

It seems my DEC axis was indeed in severe imbalance and my PA was off after all... Moreover, it was entirely human mistake (as it usually is in these kind of situation).

Curious to know how I found out ? Here it goes. Given all hypothesis were pointing in the same direction (DEC imbalance, PA off), one can only admit the simplest explanation is that indeed these are right somehow. That was difficult to admit for me, since I was convinced I had done everything right from the beginning (and I had, as a matter of fact). But at the end of the night (that's one clue), even PHD2 figures were shouting at me : PA was 20 arc-min off and DEC corrections were in only one direction.

So I mentally replayed the night, trying to remember the smallest and finest details. And it struck me. Remember the wind ? And me saying I had to remove the dew shield to help with that ? And there you have it ! That simple: I had REMOVED the DEW SHIELD ! That explains how my 2.3' PA went to 20.1', (even if I removed it carefully it seems - it was tightly put as it only holds with friction so I had to pull it out with some force). One down. That could also explain the imbalance but at that point, I was still skeptical it could have been "severe" because that thing is made of thin plastic and pretty lightweight (< 13oz) compared to the rest of the load. That and the fact that when I work on the setup inside, the dewshield is also OFF (but dustcap is ON and only slightly lighter). Anyway, simple experiment would confirm: scope in park 5, dewshield ON, DEC balanced, unlock the clutches, remove dew shield. See result in attached JPG. Definitely a severe imbalance...

Mystery solved (for me at least, it was a mystery) and lesson learned: once set up, don't touch the dew shield (basic, I should have known).

Thanks to Brian and all the folks at AP, you guys did challenge me enough to bring me back on the right track. BTW, I haven't said it publicly yet but as others have already said, that Mach2 is a marvel of engineering and craftsmanship. Thanks AP for making this piece of art real. That mount and the customer service that comes with it is definitely worth every penny.

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Roland Christen via groups.io <chris1011@...>
Envoyé : 4 mai 2021 11:21
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
The fact that both RA and Dec are drifting so fast in just a few minute's time indicates either that your polar alignment is way off, or that the object that you are calibrating on is not near the celestial equator and meridian.

Roland

-----Original Message-----
From: Seb@stro <sebastiendore1@...>
To: main@ap-gto.groups.io <main@ap-gto.groups.io>
Sent: Mon, May 3, 2021 10:42 pm
Subject: Re: [ap-gto] Spikes in DEC #guiding #guiding

Well, I'm not the one who will contest your analysis, Brian. As Howard said earlier, your advice is to be taken seriously, and I agree! 🙂 And I also agree with your argument about the guiding pulse being in only one direction and being compatible with bad PA.

The reason why I said it was good in the first place is only because PHD told me so (see attached). It wasn't based on anything other data. Hence my hypothesis about it struggling to show me the real NCP when I did the Polar Drift Align in the gusty conditions...

Anyway, AP is also working with me behind the scenes to help figure out what could have happened. So, we'll see if they can shed some light on this from their perspective.

Sébastien


De : main@ap-gto.groups.io <main@ap-gto.groups.io> de la part de Brian Valente <bvalente@...>
Envoyé : 3 mai 2021 22:55
À : main@ap-gto.groups.io <main@ap-gto.groups.io>
Objet : Re: [ap-gto] Spikes in DEC #guiding #guiding
 
Seb

When i first reviewed your PHD logs, it appeared to me your polar alignment was quite off. All your corrections were in one direction

You said you thought it was the wind, but i have my doubts about that

so it's possible your polar alignment may be misaligned for whatever reason


--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics

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