From: Shannon Watters
Subject: Re: 2.5m obslog 20080615 (MJD 54633)
Date: Mon, 16 Jun 2008 22:08:27 -0600
Hey,
The guide stars were more towards the outside.
-S
On Jun 16, 2008, at 8:53 PM, stephanie snedden
wrote:
> Okay, thanks for that info. In that case, I have another question:
> Were the guide stars that you found near the center of the plate? In
> other words, could it have a large rotator offset that caused the
> problem?
>
> Steph
> On Jun 16, 2008, at 8:23 PM, Shannon Watters wrote:
>
>> I centered on the bright one.
>>
>>
>>
>> On Jun 16, 2008, at 7:27 PM, stephanie snedden
>>  wrote:
>>
>>> Hi Dmitry,
>>>
>>> The closest FK5 star to NGC 7086 is FK5 1560 (HD 203320). This
>>> star is a double, and if you accidentally centered on the
>>> companion, you could still have gone back to the very rich field
>>> of the cluster and gotten a few stars on fibers.
>>>
>>> I've attached the POSS image of the FK5. The companion is to the
>>> upper right of the FK5 at the center, and is 6.82 asec away.
>>>
>>> I have no problem with checking the guide star brightnesses, but I
>>> also do not think we should rule out a pointing problem.
>>>
>>> Steph
>>>
>>>
>>>
>>> On Jun 16, 2008, at 6:07 PM, dmbiz@apo.nmsu.edu wrote:
>>>
>>>>
>>>> Hi Steph,
>>>> I'm sure that the problem was not in wrong pointing since we
>>>> observed
>>>> two plates right before and found guide stars right after their
>>>> fk5.
>>>> This cluster (NGC 7086) has integral magnitude V~8.4, so its
>>>> individual
>>>> members are incomparable in brightness with an FK5 star; it's
>>>> hard to make
>>>> such a mistake.
>>>> We should ask the corresponding targeting team to check
>>>> brightness of
>>>> guide stars.
>>>>
>>>> Dmitry
>>>>
>>>>> Given the density of stars in this cluster, I think it is possible
>>>>> you may have found some other star besides your FK5, and even then
>>>>> could still have two stars, and maybe even three fall into guide
>>>>> fibers. I think we should try these plates again right after we
>>>>> take
>>>>> a new pointing model on the first night of shakedown.
>>>>>
>>>>> Steph
>>>>>
>>>>>> 09:35Z cart. 6 plate 2633 mounted (seguecluster)
>>>>>> fk5 used; fk5 star normally found.
>>>>>> Only 2 guide stars are seen after that.
>>>>>> We tried large exposure time as well, ~40 sec. Same pisture.
>>>>>>
>>>>>> --
>>>>>>
>>>>>> 10:00Z cart.5 plate 2632 mounted (seguecluster)
>>>>>> fk5 used; fk5 is normally seen.
>>>>>> Only 3 guide stars are found in the field. One of them is very
>>>>>> dim
>>>>>> (guider doesn't catch it).
>>>>>> Large exposure times ~30 sec 40 sec give the same picture.
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>
>
>
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