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                                                                     Exhibit 4.2

                         REGISTRATION RIGHTS AGREEMENT

     THIS REGISTRATION RIGHTS AGREEMENT ("Registration Rights Agreement") is
entered into as of December 17, 2001 between Photoelectron Corporation, a
Massachusetts corporation (the "Company"), and PYC Corporation (the
"Purchaser").


                              W I T N E S S E T H:

     WHEREAS, pursuant to the Subscription Agreement, dated as of December 17,
2001 (collectively, the "Subscription Agreement"), by and between the Company
and the Purchaser, the Company has agreed to sell and the Purchaser has agreed
to purchase the Company's 6% Senior Convertible Debentures (the "Debentures")
convertible into shares of the Company's Common Stock, $.01 par value ("Common
Stock") (such shares of Common Stock issuable upon conversion of the Debentures
being collectively referred to herein as the "Shares");

     WHEREAS, pursuant to the terms of, and in partial consideration for, the
Purchaser's agreement to enter into the Subscription Agreement, the Company has
agreed to provide the Purchaser with the registration rights contained herein
with respect to the Shares;

     NOW, THEREFORE, in consideration of the mutual promises, representations,
warranties, covenants and conditions set forth in the Subscription Agreement and
this Registration Rights Agreement, the Company and the Purchaser agree as
follows:

     1.  Certain Definitions.   As used in this Agreement, the following terms
shall have the following respective meanings.  Other terms used herein which are
defined in the Subscription Agreements and the Debentures shall have the same
meanings herein as they do in such other documents.

     "Commission" or "SEC" shall mean the Securities and Exchange Commission or
any other federal agency at the time administering the Securities Act.

     "Registrable Securities" shall mean Shares issued or issuable to the
Purchaser or any Holder upon conversion of the Debentures or upon any stock
split, stock dividend, recapitalization or similar event with respect to such
Shares.

     "Registration Expenses" shall mean all expenses to be incurred by the
Company in connection with the Holders' exercise of their registration rights
under this Agreement, including, without limitation, all registration and filing
fees, printing expenses, fees and disbursements of counsel for the Company, blue
sky fees and expenses, and the expense of any special audits incident to or
required by any such registration (but excluding the compensation of regular
employees of the Company, which shall be paid in any event by the Company).

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     "Selling Expenses" shall mean all underwriting discounts and selling
commissions, if any, applicable to the sale of Registrable Securities.

     "Holder" shall include the Purchaser and any transferee of Debentures or
Registrable Securities which have not been sold to the public to whom the
registration rights conferred by this Agreement have been transferred in
compliance with Section 11 of this Agreement.

     "Registration Statement" shall have the meaning set forth in Section 2
herein.

     "Regulation D" shall mean Regulation D as promulgated pursuant to the
Securities Act, and as subsequently amended.

     "Securities Act" shall mean the Securities Act of 1933, as amended.

     2.  The Registration Requirements.  The Company shall use its best efforts
to file within ninety (90) days after the Closing Date (as defined in the
Debentures), and use its best efforts to cause to become effective under the
Securities Act, a registration statement on Form S-3 or, if Form S-3 is not then
available, another appropriate form covering the resale of the Shares (the
"Registration Statement").

     3.  Exercise of Rights.  The Holders shall act with respect to their rights
under this Agreement according to the vote of a majority-in-interest of the
Shares voting together as a single class on an as-converted basis.

     4.  Expenses of Registration.  All Registration Expenses incurred in
connection with any registration, qualification or compliance pursuant to this
Agreement shall be borne by the Company, and all Selling Expenses relating to
the sale of any Registrable Securities shall be borne by the Holder selling such
Registrable Securities.

     5.  Registration Procedures.  In the case of the registration effected by
the Company pursuant to this Agreement, the Company will keep the Holders
advised in writing as to initiation of the registration and as to the completion
thereof.  At its expense, the Company will use its best efforts to:

     a)  Keep the Registration Statement effective at all times until such time
         as all of the shares of Common Stock issuable upon conversion of the
         Debentures (i) have been distributed to the public pursuant to the
         Registration Statement, (ii) have been distributed to the public
         pursuant to Rule 144 promulgated under the Securities Act or (iii) are
         saleable pursuant to Rule 144(k) promulgated under the Securities Act;
         and

     b)  Furnish such number of copies of the Registration Statement, the
         prospectus used in connection with such registration statement and
         other documents incident thereto as any Holder from time to time may
         reasonably request.

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     In the event that the Company shall fail to keep such Registration
Statement effective for any period of fifteen (15) consecutive days at any time
after the initial effectiveness of such Registration Statement and before the
end of the period described in paragraph 5(a) above, the then outstanding
principal of each Debenture and all accrued and unpaid interest thereon will
become immediately due and payable at the option of the Holder thereof.

     6.   Suspension of Use of Registration Statement.  Each Holder agrees that,
upon receipt of any notice from the Company (A) of the happening of any event
which makes any statements made in the Registration Statement or related
prospectus(es) filed pursuant to this Registration Rights Agreement, or any
document incorporated or deemed to be incorporated therein by reference, untrue
in any material respect or which requires the making of any changes in such
Registration Statement or prospectus(es) so that, in the case of such
Registration Statement or prospectus(es), it will not contain any untrue
statement of a material fact or omit to state any material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstance under which they were made, not misleading or (B) that, in the
judgment of the Company's board of directors, it is advisable to suspend use of
the prospectus(es) for a discrete period of time due to pending corporate
developments which are or may be material to the Company but have not been
disclosed in the Registration Statement or in relevant public filings with the
SEC, or (C) that the SEC has issued a stop order suspending the effectiveness of
the Registration Statement, such Holder will forthwith discontinue disposition
of such Shares covered by such Registration Statement or prospectus(es) until it
is advised in writing by the Company that use of the applicable prospectus may
be resumed, and has received copies of any additional or supplemented filings
that are incorporated or deemed to be incorporated by reference in such
prospectus(es).  The Company shall use all reasonable best efforts to insure
that the use of the prospectus(es) may be resumed as soon as practicable, and in
any event shall not be entitled to require any Holder to suspend use of the
prospectus(es) for more than thirty (30) consecutive days on any one occasion,
more than forty-five (45) consecutive days in the aggregate on two occasions
which are not at least ninety (90) days apart or more than an aggregate of sixty
(60) days in any twelve month period.

     7.  Indemnification.

     a)  Company Indemnity. The Company will indemnify the Holders, each of
         their officers, directors and partners, and each person controlling a
         Holder within the meaning of Section 15 of the Securities Act and the
         rules and regulations thereunder, against all claims, losses, damages
         and liabilities (or actions in respect thereof) arising out of or based
         on any untrue statement (or alleged untrue statement) of a material
         fact contained in any registration statement, prospectus, offering
         circular or other document (including any amendment or supplement
         thereto or document incorporated by reference therein) relating to the
         Registrable Securities, or arising out of or based on any omission (or
         alleged omission) to state therein a material fact required to be
         stated therein

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         or necessary to make the statements therein not misleading, or arising
         out of or based on any violation by the Company of the Securities Act
         or any state securities law or in either case, any rule or regulation
         thereunder, applicable to the Company and relating to action or
         inaction required of the Company in connection with the Registrable
         Securities, and will reimburse the Holders, each of their officers,
         directors and partners, and each person controlling such Holder, for
         any legal and any other expenses reasonably incurred in connection with
         investigating and defending any such claim, loss, damage, liability or
         action, provided that the Company will not be liable in any such case
         to the extent that any such claim, loss, damage, liability or expense
         arises out of or is based on any untrue statement or omission (or
         alleged untrue statement or omission) based upon written information
         furnished to the Company by such Holder and stated to be specifically
         for use therein. The indemnity agreement contained in this Section 7(a)
         shall not apply to amounts paid in settlement of any such loss, claim,
         damage, liability or action if such settlement is effected without the
         consent of the Company (which consent will not be unreasonably
         withheld).

     b)  Holder Indemnity. Each Holder (each, in such capacity, the
         "Indemnifying Holder") will, if Registrable Securities held by it are
         included in the securities registered under the Registration Statement,
         indemnify the Company, each of its directors, officers, partners, each
         person who controls the Company within the meaning of Section 15 of the
         Securities Act and the rules and regulations thereunder, each other
         Holder (if any), and each of their officers, directors and partners,
         and each person controlling such other Holders against all claims,
         losses, damages and liabilities (or actions in respect thereof) arising
         out of or based on any untrue statement (or alleged untrue statement)
         of a material fact contained in any registration statement, prospectus,
         offering circular or other document (including any amendment or
         supplement thereto or document incorporated by reference therein)
         relating to the Registrable Securities, or arising out of or based on
         any omission (or alleged omission) to state therein a material fact
         required to be stated therein or necessary to make the statement
         therein not misleading, and will reimburse the Company and such other
         Holders and their directors, officers and partners, or control persons
         for any legal or any other expenses reasonably incurred in connection
         with investigating or defending any such claim, loss, damage, liability
         or action, in each case to the extent, but only to the extent, that
         such untrue statement (or alleged untrue statement) or omission (or
         alleged omission) is made in such registration statement, prospectus,
         offering circular or other document in reliance upon and in conformity
         with written information furnished to the Company by the Indemnifying
         Holder and stated to be specifically for use therein; provided,
         however, that the obligations of the Indemnifying Holder shall not
         apply to amounts paid in settlement of any such claims, losses, damages
         or liabilities if such settlement is effected without the consent of
         the Indemnifying Holder (which consent shall not be unreasonably
         withheld).

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     c)  Procedure. Each party entitled to indemnification under this Article
         (the "Indemnified Party") shall give notice to the party required to
         provide indemnification (the "Indemnifying Party") promptly after such
         Indemnified Party has actual knowledge of any claim as to which
         indemnity may be sought, and shall permit the Indemnifying Party to
         assume the defense of any such claim in any litigation resulting
         therefrom, provided that counsel for the Indemnifying Party, who shall
         conduct the defense of such claim or any litigation resulting
         therefrom, shall be approved by the Indemnified Party (whose approval
         shall not be unreasonably withheld), and the Indemnified Party may
         participate in such defense at such party's expense, provided further
         that the failure of any Indemnified Party to give notice as provided
         herein shall not relieve the Indemnifying Party of its obligations
         under this Article except to the extent that the Indemnifying Party is
         actually prejudiced by such failure to provide notice and provided
         further that the Indemnified Party may employ no more than one separate
         counsel at the Indemnifying Party's expense if in the reasonable
         judgment of the Indemnified Party, based upon the written advice of the
         Indemnified Party's counsel, a copy of which is provided to the
         Indemnifying Party, representation of both parties' interests by the
         same counsel would be inappropriate due to actual conflicts of
         interest. No Indemnifying Party, in the defense of any such claim or
         litigation, shall, except with the consent of each Indemnified Party,
         consent to entry of any judgment or enter into any settlement which
         does not include as an unconditional term thereof the giving by the
         claimant or plaintiff to such Indemnified Party of a release from all
         liability in respect to such claim or litigation. Each Indemnified
         Party shall furnish such information regarding itself or the claim in
         question as an Indemnifying Party may reasonably request in writing and
         as shall be reasonably required in connection with the defense of such
         claim and litigation resulting therefrom.

     8.  Contribution.   If the indemnification provided for in Section 7 from
the Indemnifying Party is unavailable to an Indemnified Party thereunder in
respect of any losses, claims, damages, liabilities or expenses referred to in
Section 7, then the Indemnifying Party, in lieu of indemnifying such Indemnified
Party, shall contribute to the amount paid or payable by such Indemnified Party
as a result of such losses, claims, damages, liabilities or expenses in such
proportion as is appropriate to reflect the relative fault of the Indemnifying
Party and Indemnified Parties in connection with the actions which resulted in
such losses, claims, damages, liabilities or expenses, as well as any other
relevant equitable considerations.  The relative fault of such Indemnifying
Party and Indemnified Parties shall be determined by reference to, among other
things, whether any action in question, including any untrue or alleged untrue
statement of a material fact or omission or alleged omission to state a material
fact, has been made by, or relates to information supplied by, such Indemnifying
Party or Indemnified Parties, and the parties' relative intent, knowledge,
access to information and opportunity to correct or prevent such action.  The
amount paid or payable by a party as a result of the losses, claims, damages,
liabilities and expenses referred to above shall be deemed to include, subject
to

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the limitations set forth in Section 7, any legal or other fees or expenses
reasonably incurred by such party in connection with any investigation or
proceeding.

     The parties hereto agree that it would not be just and equitable if
contribution pursuant to this Section 8 were determined by pro rata allocation
or by any other method of allocation which does not take into account the
equitable considerations referred to in the immediately preceding paragraph.
Notwithstanding the provisions of this Section 8, no Holder shall be required to
contribute any amount in excess of the amount of the total net proceeds received
by such Holder from sales of the Registrable Securities sold by such Holder
pursuant to the offering that gave rise to such losses, claims, damages,
liabilities or expenses.  No person guilty of fraudulent misrepresentation
(within the meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation.

     If indemnification is available under Section 7, the Indemnifying Parties
shall indemnify each Indemnified Party to the full extent provided in Section 7
without regard to the relative fault of said Indemnifying Party or Indemnified
Party or any other equitable consideration provided for in this Section 8.

     9.  Survival.  The indemnity and contribution agreements contained in
Sections 7 and 8 shall remain operative and in full force and effect regardless
of (i) any termination of the Subscription Agreement, (ii) any investigation
made by or on behalf of any Indemnified Party or by or on behalf of the
Indemnifying Party and (iii) the consummation of the sale or successive resales
of the Registrable Securities.

     10.  Information to be Furnished By Holder.  Each Holder shall furnish to
the Company, within 20 business days of the Company's request therefor, such
information regarding such Holder and the distribution proposed by such Holder
as the Company may reasonably request in writing and as shall be reasonably
required in connection with any registration, qualification or compliance
referred to in this Registration Rights Agreement.

     11.  Transfer of Assignment of Registration Rights.  The rights, granted to
each Holder by the Company under this Registration Rights Agreement, to cause
the Company to register Registrable Securities may be transferred or assigned to
a transferee or assignee of not less than $100,000 in principal amount of
Debentures, provided that the Company is given written notice by such Holder at
the time of or within a reasonable time after said transfer or assignment,
stating the name and address of said transferee or assignee and identifying the
securities with respect to which such registration rights are being transferred
or assigned; and provided further that the transferee or assignee of such rights
agrees to be bound by this Registration Rights Agreement.

     12.  Miscellaneous.

      a)  Entire Agreement. This Registration Rights Agreement contains the
          entire understanding and agreement of the parties with respect to the
          subject matter

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hereof and supersedes all prior agreements and understandings, oral or written,
with respect to such matters.

      b)  Amendments and Waivers. No provision of this Registration Rights
          Agreement may be waived or amended except in a written instrument
          signed, in the case of an amendment, by the Company and Holders then
          holding at least a majority of the Shares (on an as-converted basis),
          or, in the case of a waiver, by (i) the Company, if the Company is the
          party against whom enforcement of such waiver is sought, or (ii) the
          Holders then holding at least a majority of the Shares (on an as-
          converted basis), if the Holders are the party against whom
          enforcement of such waiver is sought.

      c)  Notices. Any notice or other communication given or permitted under
          this Agreement shall be in writing and shall be deemed to have been
          duly given if personally delivered or sent by certified mail, return
          receipt requested, postage prepaid, by facsimile, by Federal Express
          or by other such expedited means, (a) if to a Purchaser, at its
          address set forth on Schedule 1 hereto, (b) if to the Company, at its
          address set forth on the signature page hereto, (c) if, to a Holder
          other than the Purchasers, at the address thereof furnished by like
          notice to the Company, or (d) to any such addressee at such other
          address or addresses as shall be so furnished to the other parties
          hereto by like notice.

      d)  Gender of Terms. All terms used herein shall be deemed to include the
          feminine and the neuter, and the singular and the plural, as the
          context required.

      e)  Governing Law; Consent to Jurisdiction. This Registration Rights
          Agreement and the validity and performance of the terms hereof shall
          be governed by and construed in accordance with the internal
          substantive laws of the Commonwealth of Massachusetts without regard
          to principles of conflicts of law or choice of law. The parties hereto
          hereby consent to, and waive any objection to the exercise of,
          personal jurisdiction in the Commonwealth of Massachusetts with
          respect to any action or proceeding arising out of this Registration
          Rights Agreement.

      f)  Title. The titles used in this Registration Rights Agreement are used
          for convenience only and are not to be considered in construing or
          interpreting this Agreement.

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  IN WITNESS WHEREOF, the parties hereto have cause this Registration Rights
Agreement to be duly executed as of the date first above written.


                                  PURCHASER:

                                  PYC Corporation

                                  By:  /s/ Peter Constantine Nomikos
                                       -----------------------------
                                       Name:  Peter Constantine Nomikos
                                       Title: President

                                  Address for Notice:

                                  c/o Aegeus Shipping Co. Ltd.
                                  17-19 Akti Miaouli
                                  Piraeus 185 35 Greece

                                  PHOTOELECTRON CORPORATION

                                  By: /s/ Timothy W. Baker
                                      ---------------------
                                      Name:  Timothy W. Baker
                                      Title: Executive Vice President,
                                             Chief Financial Officer and
                                             Treasurer


                                  Address for Notice:

                                  5 Forbes Road
                                  Lexington, MA 02421
                                  Attn:  Timothy W. Baker

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