Date: Mon, 23 Sep 2013 13:51:01 -0600 (MDT)
Subject: Re: [sdss3-25mlog 1393] 2.5m obslog 20130921 (MJD 56557)
From: "Garrett Ebelke"
Hi John,
Yes, you are correct, I did help write/debug this error message. At the
time, it made sense but during science last night it was still a little
confusing.
I think the confusing part is that we can't modify the existing science.
With BOSS, we can modify 4 exposures to 3 exposure when we are integrating
the 3rd exposure and it will just finish that exposure. We were trying to
do that with APOGEE and it wouldn't let us.
DanO and I discussed changing the exposure count request to 8 instead of
2x ABBA. Of course, you'd have to write code to somehow always start the
dither at A, dither between exp 1-2, dither again between 3-4, etc. But
that way, we could, in theory modify from 8 exposures to 6 when we are on
the 5th exposure. Does that make sense? You hinted at that too, but were
saying ABBAABBA.
Maybe some other observers can weigh in on whether or not it would be
useful to count exposures by the dither instead of by a full ABBA
sequence?
-Garrett
> On 22Sep 2013, at 07:20, gebelke@apo.nmsu.edu wrote:
>
>>                       APACHE POINT OBSERVATORY SDSS 2.5M
>>
>>                                 OBSERVING LOG
>>                          Saturday September 21, 2013
>>
>>                                  (MJD 56557)
>>
>> We attempted to modify the exposure from 2x ABBA sequences to 1x AB
>> sequence
>> after we had finished the first ABBA, due to humidity rising rapidly. It
>> beeped
>> at us:
>>
>> 08:16:40 APO.gebelke 43 sop f text="Cannot modify dither sequence if
>> current
>> sequence count is > 1."
>> 08:16:40 CmdDone: APO.gebelke 43 sop doApogeeScience ditherSeq=\"AB\"
>> seqCount=2
>> expTime=500.0
>> (APO.gebelke 558): doApogeeScience ditherSeq="; UNPARSEDTEXT="AB\"
>> seqCount=2
>> expTime=500.0\""
>> 08:16:40 .sop 558 sop f text="If you are certain it makes sense to
>> change the
>> dither sequence, change Seq Count to 1 first."
>
> This message is meant to tell you that changing "ABBA,ABBA" -> "ABBA"
> doesn't make sense if SOP has already started the second ABBA. If I'm
> reading the log correctly, SOP was at step 5 (sequenceState=4, indexed
> from 0) of ABBAABBA, i.e., the first A in the second ABBA, when the
> command was issued, hence the message.
>
> In the situation you were in, there is no obvious solution on how to
> modify an "2xABBA"->"ABBAAB", given the way the exposures are described
> (Nx[AB][BA]). See the discussion in ticket #1761:
>
> https://trac.sdss3.org/ticket/1761
>
> The "feedback that [didn't] make sense" is because the change didn't make
> sense, given that the 2nd ABBA had already started. For the future, you
> would have to issue the change before the 2nd ABBA started, by doing what
> you tried (changing seqCount=1, with ditherSeq="ABBA"). I can try
> rewording the message, but it seemed clear enough at the time (I think you
> may have even helped me debug it, Garrett!).
>
> The other option would be to abandon the 2xABBA usage, and specify
> "ABBAABBA" explicitly. This would allow more fine grained control of
> currently-running exposures, but it would also give more opportunity for
> typos.
>
> John
>
> --
> *************************
> John Parejko
> john.parejko@yale.edu
> http://www.astro.yale.edu/~jp727/
> 203 432-9759
> JWG 465
> Department of Physics
> Yale University
> New Haven, CT
> **************************
>
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