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                                  EXHIBIT (C)

     THE FOLLOWING OPINION OF J.P. MORGAN SECURITIES INC. AND THE BEACON GROUP
CAPITAL SERVICES, LLC DOES NOT ADDRESS THE FAIRNESS OF THE MERGER TO THE PUBLIC
STOCKHOLDERS, AND IT SHOULD NOT BE RELIED UPON FOR SUCH PURPOSE.

JANUARY 29, 2000

Board of Directors
Thermo Electron Corporation
81 Wyman Street
Post Office Box 9046
Waltham, MA 02454-9046

Attention:  Dr. Richard Syron
          Chairman and Chief Executive Officer

Special Committee of
the Board of Directors of
Thermo Instrument Systems Inc.
81 Wyman Street
Post Office Box 9046
Waltham, MA 02454-9046

Attention:  Mr. Polyvios C. Vintiadis
          Director

Ladies and Gentlemen:

     J.P. Morgan Securities Inc. ("J.P. Morgan") and The Beacon Group Capital
Services, LLC (collectively "we", "us" and "our") understand that Thermo
Instrument Systems Inc. ("Thermo Instrument"), a subsidiary of Thermo Electron
Corporation ("Thermo Electron"), proposes to acquire all of the outstanding
common stock, par value $.01 per share, (the "Shares") of Thermo Optek
Corporation (the "Company") not currently held by Thermo Electron or its
subsidiaries from the holders thereof at a purchase price of $15.00 per Share,
net to the seller in cash (the "Consideration"), pursuant to the merger (the
"Merger") of Optek Acquisition Inc. (the "Purchaser"), a wholly-owned subsidiary
of Thermo Instrument, with and into the Company. You have requested our joint
opinion as to the fairness, from a financial point of view, to Thermo Instrument
and to Thermo Electron of the Consideration proposed to be paid pursuant to the
Merger.

     In arriving at our opinion, we have reviewed (i) certain publicly available
information concerning the business of the Company and of certain other
companies engaged in businesses deemed by us to be comparable to those of the
Company; (ii) the reported market prices of the securities of certain other
companies deemed by us to be comparable to the Company; (iii) publicly available
terms of certain transactions involving companies deemed by us to be comparable
to the Company and the consideration paid for such companies; (iv) current and
historical market prices of the Shares; (v) the audited financial statements of
Thermo Instrument, Thermo Electron and the Company for the fiscal year ended
January 2, 1999 and the unaudited financial statements of Thermo Instrument,
Thermo Electron and the Company for the period ended October 2, 1999; (vi)
certain agreements with respect to outstanding indebtedness or obligations of
Thermo Instrument, Thermo Electron and the Company; (vii) the terms of other
business combinations that we deemed relevant; and (viii) projections for the
period from October 3, 1999 through January 1, 2000 and for fiscal 2000 prepared
by the Company in November 1999 (the "2000 Projections").

     In addition, we have held discussions with certain members of the
managements of Thermo Instrument, Thermo Electron and the Company with respect
to certain aspects of the Merger, the past and current business operations of
the Company, the financial condition and future prospects and operations of the
Company and certain other matters we believed necessary or appropriate to our
inquiry. We have reviewed such other financial studies and analyses and
considered such other information as we deemed appropriate for the purposes of
this opinion.
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     In giving our opinion, we have relied upon and assumed, without independent
verification, the accuracy and completeness of all information that was publicly
available or was furnished to, or discussed with, us, by Thermo Instrument,
Thermo Electron or the Company or was otherwise reviewed by us, and we have not
assumed any responsibility or liability therefor. We have also assumed that
there have been no material changes in the Company's financial condition,
results of operations, business or prospects since the date of the most recent
financial statements made available to us. We have not conducted, and we have
not assumed any responsibility for conducting, any valuation, appraisal or
physical inspection of any assets or liabilities (contingent or otherwise), nor
have any such valuations or appraisals been provided to us. In relying on the
financial analyses, projections and estimates provided to, or discussed with,
us, we have assumed that they have been reasonably prepared based on assumptions
reflecting the best currently available estimates and judgments by management as
to the expected future financial performance of the Company. We have relied as
to all legal matters relevant to rendering our opinion upon the advice of
counsel.

     Our opinion is necessarily based on economic, market and other conditions
as in effect on, and the information made available to us as of, the date
hereof. It should be understood that subsequent developments may affect the
conclusions in this opinion and that we do not have any obligation to update,
revise or reaffirm this opinion.

     We have acted as financial advisors to Thermo Instrument and Thermo
Electron with respect to the proposed Merger and will receive a fee from Thermo
Electron for our services. We have also acted as financial advisors to Thermo
Electron for the purpose of advising Thermo Electron in connection with its
strategic alternatives, including the proposed reorganization of Thermo Electron
and its subsidiaries. As part of the proposed reorganization of Thermo Electron,
it is contemplated that Thermo Electron will acquire the publicly-held minority
interest in Thermo Instrument. We will receive separate fees for services with
respect to other elements of Thermo Electron's reorganization, including acting
as financial advisors to Thermo Electron in connection with the acquisition of
the publicly-held minority interest in Thermo Instrument. These other fees
include a minimum retainer for each of us and additional compensation if some or
all of the other elements of Thermo Electron's reorganization are completed. In
the ordinary course of their businesses, J.P. Morgan and its affiliates may
actively trade the debt and equity securities of Thermo Instrument, Thermo
Electron or the Company and their affiliates for their own account or for the
accounts of customers and, accordingly, they may at any time hold long or short
positions in such securities.

     On the basis of and subject to the foregoing, it is our opinion as of the
date hereof that the Consideration to be paid pursuant to the Merger is fair,
from a financial point of view, to Thermo Instrument and to Thermo Electron.

     This letter is provided to the Board of Directors of Thermo Electron and
the Special Committee of Thermo Instrument in connection with and for the
purposes of their evaluation of the Merger. This opinion does not address the
fairness of the Consideration to the public minority stockholders nor does it
constitute a recommendation to any stockholder of the Company as to whether such
stockholder should exercise their statutory appraisal rights. This opinion may
not be disclosed, referred to, or communicated (in whole or in part) to any
third party for any purpose whatsoever except with our prior written consent in
each instance. We hereby consent to the filing of this opinion as an exhibit to
the Transaction Statement on Schedule 13E-3 to be filed by Thermo Instrument,
Thermo Electron and certain of their subsidiaries and to the provision of this
opinion to persons who request it as contemplated by the Schedule 13E-3.

Very truly yours,

J.P. MORGAN SECURITIES INC.

THE BEACON GROUP CAPITAL SERVICES, LLC