Subject: are there new throughput numbers? Will there be any?

From: richmond@astro.Princeton.EDU

Submitted: Mon, 27 Jan 1997 11:33:47 -0500 (EST)

Message number: 118 (previous: 117, next: 119 up: Index)

  The APO 3.5-m telescope recently had all three mirrors 
realuminized, and the apo35-general mailing list shows that
it was planned to assess the performance of the new optics
as quickly as possible:

> Report 3.5-m User Committee Meeting 12/09/96.
>    - primary mirror is in Tucson. Will be realuminized on 12/11/96.
> The goal is to have all three mirrors realuminized during this
> shutdown. An immediate throughput measurement will be made after
> completion of the shutdown.

>   Minutes of APO 3.5m User's Committee Phone Conference
>                 Monday, January 6, 1997
>   As soon as there is some clear weather, new throughput measurements will
> be taken.  Everyone is hopeful that with the realuminization, the
> throughput will have gone up substantially. 

>    Jan 8, 1997
> Furthermore, once re-assembly of
> the telescope is accomplished, approximately 1.5 clear nights on the
> sky are needed to re-establish alignment, a pointing model, focus
> settings, instrument blocks and so forth.  If photometric conditions
> prevailed during this period, it would also be very desirable to make
> some initial post re-aluminization throughput measurements. 

  From the Night Logs for the current year, we can see that the weather has
not been very good this month; however, there have been at least three
nights with stretches of three or more hours of clear weather (marked
below with asterisks):

1/10/97         cirrus, partly cloudy
1/11/97         overcast
1/12/97         clouds
1/13/97         closed
1/14/97         closed
1/15/97   *     "Throughput data using SPICAM and R filter was obtained during"
                "   a period of photometric skies."
1/16/97         overcast, then clear after 2:00
1/17/97         clear until 22:00, then cirrus
1/18/97         clouds
1/19/97         closed
1/20/97         cloudy
1/21/97   *     mostly clear, with occasional cirrus
1/22/97         clouds
1/23/97         clouds, then clear after 04:00
1/24/97   *     clear most of the night
1/25/97         clouds
1/26/97         closed

    It appears that one 5.4 hour period of one night (Jan 15) has
been devoted to throughput measurements.  Was this all that was

    Have those data been reduced?  Is there any information on the
improvement of throughput, from this or other sources?  I would
have guessed that "science" observers would want to know if the
telescope is performing better than it has in the past, since
it would allow them to modify their programs accordingly.

    Waiting eagerly to hear the answers (isn't everyone?)

                          Michael Richmond

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