Mail Stop 0306

March 9, 2005



VIA U.S. MAIL AND FAX (860) 347-8372

Mr. Walter A. Shephard
Vice President, Finance and Chief Financial Officer
Zygo Corporation
21 Laurel Brook Road
Middlefield, Connecticut 06455

	Re:	Zygo Corporation
		Form 10-K for the year ended June 30, 2004


Dear Mr. Shephard:

      We have reviewed your response dated February 2, 2005 and
have
the following comments.  We have limited our review to only your
financial statements and related disclosures and will make no
further
review of your documents.  Where indicated, we think you should
revise future documents in response to these comments.  If you
disagree, we will consider your explanation as to why our comments
are inapplicable or a revision is unnecessary.  Please be as
detailed
as possible in your explanations.  In our comments, we asked you
to
provide us with supplemental information so we may better
understand
your disclosure.  After reviewing this information, we may or may
not
raise additional comments.

	Please understand that the purpose of our review process is
to
assist you in your compliance with the applicable disclosure
requirements and to enhance the overall disclosure in your filing.
We look forward to working with you in these respects.  We welcome
any questions you may have about our comment or on any other
aspect
of our review.  Feel free to call us at the telephone numbers
listed
at the end of this letter.







Accounting Comments

Form 10-K for the year ended June 30, 2004

Revenue Recognition - Page F-8

1. We note your response to our previous comment 5 and understand
that your products generally require installation. Please tell us
how
you determined that installation is perfunctory and confirm
installation is not essential to the functionality of the
delivered
products or services, as contemplated by SAB 104.  Also, please
supplementally confirm you comply the guidance at SAB Topic
13.A.3.b,
Question 2.

2. Please supplementally confirm that where your products include
software, such software is incidental (as defined in SOP 97-2) to
the
products.  If not incidental, tell us how your accounting for
sales
of the products complies with SOP 97-2 or other applicable
generally
accepted accounting principles.

3. Lastly, tell us how you considered the criteria listed in
paragraph 9 of EITF 00-21. Please tell us why you do not believe
the
product and the installation are two separate deliverables.  We
may
have further comments after reviewing your responses.

Note 2. Divestitures and Discontinued Operation

4. We noted your response to our previous comment 6 and also
reviewed
your disclosure in Form 10-Q for the period ending December 31,
2004.
Please revise future filings to more fully describe the
circumstances
related to the impairment charges.  Your revisions should include
the
significant information provided to us supplementally. We note
your
current disclosure in Form 10-Q states only that you "have
marketed
for sale the facility previously used by the TeraOptix unit and
have
recorded impairment charges since then related to the decline in
the
fair market value of the facility."  Please also include the
amount
of the impairment charges as discussed in your response to our
prior
comment.


*    *    *    *

      As appropriate, please respond to these comments within 10
business days or tell us when you will provide us with a response.
Please furnish a cover letter that keys your responses to our
comments and provides any requested supplemental information.
Detailed cover letters greatly facilitate our review.  Please file
your cover letter on EDGAR.  Please understand that we may have
additional comments after reviewing your responses to our
comments.

      We urge all persons who are responsible for the accuracy and
adequacy of the disclosure in the filings reviewed by the staff to
be
certain that they have provided all information investors require.
Since the company and its management are in possession of all
facts
relating to a company`s disclosure, they are responsible for the
accuracy and adequacy of the disclosures they have made.

      In connection with responding to our comments, please
provide,
in writing, a statement from the company acknowledging that

?	the company is responsible for the adequacy and accuracy of
the
disclosure in the filings;
?	staff comments or changes to disclosure in response to staff
comments in the filings reviewed by the staff do not foreclose the
Commission from taking any action with respect to the filing; and
?	the company may not assert staff comments as a defense in any
proceeding initiated by the Commission or any person under the
federal securities laws of the United States.

      In addition, please be advised that the Division of
Enforcement
has access to all information you provide to the staff of the
Division of Corporation Finance in our review of your filing or in
response to our comments on your filing.

      You may contact Julie Sherman, Staff Accountant, at (202)
824-
5506 or me at (202) 942-1812 if you have questions.  In this
regard,
do not hesitate to contact Martin James, the Senior Assistant
Chief
Accountant, at (202) 942-1984.



							Sincerely,



							Jay Webb



Mr. Walter A. Shephard
Zygo Corporation
March 9, 2005
Page 1