Sloan Digital Sky Survey Telescope Technical Note 19980908
Patrick Waddell, Mark Klaene
The Sloan Digital Sky Survey 2.5-m telescope has a diverse set of optics ranging from the large primary to a selection of c-mount lenses used to assess the performance of the stray light baffles. This document summarizes the cleaning guidelines to be followed during the maintenance of these optics.
WARNINGS AND CAUTIONARY NOTES:
ALWAYS WORK WITH CLEANING FLUIDS IN WELL VENTILATED AREAS ELIMINATE ANY SOURCES OF IGNITION. KNOW THE LOCATION OF THE NEAREST FIRE EXTINGUISHER AND CHECK ITS PRESSURE GAUGE IF ANY. DO NOT CLEAN OPTICS IN THE FIELD - OPTICS MUST BE REMOVED FROM THE TELESCOPE AND CLEANED IN A CLEAN INDOOR WORK ENVIRONMENT. CLEANING MUST BE DONE WITH LIGHTING CONDITIONS SUCH THAT SURFACE DUST AND PARTICLES CAN BE BRIGHTLY ILLUMINATED AND CLEARLY SEEN. AIR SOURCES FOR BLOWING SURFACE DUST MUST BE DRY AND OIL-FREE AND HAVE AN IN-LINE FILTER FOR PARTICULATE MATTER.
ELIMINATE ANY SOURCES OF IGNITION. KNOW THE LOCATION OF THE NEAREST FIRE EXTINGUISHER AND CHECK ITS PRESSURE GAUGE IF ANY.
DO NOT CLEAN OPTICS IN THE FIELD - OPTICS MUST BE REMOVED FROM THE TELESCOPE AND CLEANED IN A CLEAN INDOOR WORK ENVIRONMENT.
CLEANING MUST BE DONE WITH LIGHTING CONDITIONS SUCH THAT SURFACE DUST AND PARTICLES CAN BE BRIGHTLY ILLUMINATED AND CLEARLY SEEN.
AIR SOURCES FOR BLOWING SURFACE DUST MUST BE DRY AND OIL-FREE AND HAVE AN IN-LINE FILTER FOR PARTICULATE MATTER.
Materials:
All of these optics have hard AR coatings which can stand up to strong cleaning agents. Reagent grade acetone or methanol or isopropyl alcohol are highly recommended. Never return unused cleaning fluid to the bottle and cap the bottle when not in use. Distilled water Large and small tissues such as Kimwipes
Distilled water
Large and small tissues such as Kimwipes
Preliminary steps for the common and spectrograph corrector:
The common corrector and the spectrograph corrector must be cleaned while supported such that the optical axis is normal to the floor. To clean the correctors, the plastic emergency retainer must be removed from the side to be cleaned. Before removal, mark the orientation of the retainer relative to the corrector mount so that it can be reassembled in the same orientation. The retainer may be removed only from the side which is facing upward. Do not invert the corrector with a retainer removed. Only one retainer is to be removed at a time. After cleaning each surface, the retainer is to be reinstalled immediately.
To clean the correctors, the plastic emergency retainer must be removed from the side to be cleaned. Before removal, mark the orientation of the retainer relative to the corrector mount so that it can be reassembled in the same orientation.
The retainer may be removed only from the side which is facing upward. Do not invert the corrector with a retainer removed.
Only one retainer is to be removed at a time. After cleaning each surface, the retainer is to be reinstalled immediately.
Instructions
1. Blow off surface dust using an air source meeting the criteria discussed above. 2. Inspect for large dust particles. If present, moisten a small tissue with the distilled water and coax the particles off onto the tissue. Discard tissues after single use. 3. Inspect surface for water drop stains. If present, depending on size, moisten a large or small tissue with the distilled water and lightly wipe the area to remove the dried-on material. The wiping should not be rubbing; the sum of gravity and adherence due to water tension should be the dominant force between the tissue and the glass. Allow to dry. 4. Moisten a large tissue and gently wipe the lens, starting at the center and going out. There should be sufficient liquid that the tissue and liquid can "glide together" across the surface, and not so much that the fluid can flow away from the tissue on its own. Discard tissues after single use and be sure that oils from fingers does not contaminate the tissue which will contact the glass. 5. Continue out until the area cleaned is within about 10 to 15 mm from the elastomer bond between the glass and the steel mounting ring. Go no further; avoid getting the liquid in contact with the elastomer bond. 6. Inspect the surface for streaks and remnant contamination. If the lens was excessively dirty it may be necessary to repeat steps 4 and 5.
2. Inspect for large dust particles. If present, moisten a small tissue with the distilled water and coax the particles off onto the tissue. Discard tissues after single use.
3. Inspect surface for water drop stains. If present, depending on size, moisten a large or small tissue with the distilled water and lightly wipe the area to remove the dried-on material. The wiping should not be rubbing; the sum of gravity and adherence due to water tension should be the dominant force between the tissue and the glass. Allow to dry.
4. Moisten a large tissue and gently wipe the lens, starting at the center and going out. There should be sufficient liquid that the tissue and liquid can "glide together" across the surface, and not so much that the fluid can flow away from the tissue on its own. Discard tissues after single use and be sure that oils from fingers does not contaminate the tissue which will contact the glass.
5. Continue out until the area cleaned is within about 10 to 15 mm from the elastomer bond between the glass and the steel mounting ring. Go no further; avoid getting the liquid in contact with the elastomer bond.
6. Inspect the surface for streaks and remnant contamination. If the lens was excessively dirty it may be necessary to repeat steps 4 and 5.
ALWAYS WORK WITH CLEANING FLUIDS IN WELL VENTILATED AREAS ELIMINATE ANY SOURCES OF IGNITION. KNOW THE LOCATION OF THE NEAREST FIRE EXTINGUISHER AND CHECK ITS PRESSURE GAUGE IF ANY. AIR SOURCES FOR BLOWING SURFACE DUST MUST BE DRY AND OIL-FREE AND HAVE AN IN-LINE FILTER FOR PARTICULATE MATTER.
Materials
The fiber harness optical surfaces have no coatings and can stand up to strong cleaning agents such as alcohol and acetone. Reagent grade methanol or isopropyl alcohol are highly recommended. Also, one must be careful to preserve the cleanliness of the alcohol. Never return unused alcohol to the bottle and cap the bottle when not in use.
Cotton swabs
1. Harness cleaning should be done with good lighting conditions and while viewed under magnification. 2. The selected cleaning fluid should be applied with clean cotton swabs. Although a single swab can probably be used for several ferrules, be careful to always clean with a fresh part of the swab. 3. During cleaning, strokes should all be made in the same direction across the face of v-groove blocks and the polished ends of the ferrules. This pushes the dirt to one side rather than moving it back and forth across the optical surface. 4. Let fibers air dry. 5. Check for remnant cotton swab fibers and blow off using an air source meeting the criteria discussed above.
2. The selected cleaning fluid should be applied with clean cotton swabs. Although a single swab can probably be used for several ferrules, be careful to always clean with a fresh part of the swab.
3. During cleaning, strokes should all be made in the same direction across the face of v-groove blocks and the polished ends of the ferrules. This pushes the dirt to one side rather than moving it back and forth across the optical surface.
4. Let fibers air dry.
5. Check for remnant cotton swab fibers and blow off using an air source meeting the criteria discussed above.
ALWAYS WORK WITH CLEANING FLUIDS IN WELL VENTILATED AREAS ELIMINATE ANY SOURCES OF IGNITION. KNOW THE LOCATION OF THE NEAREST FIRE EXTINGUISHER AND CHECK ITS PRESSURE GAUGE IF ANY. NEVER USE ACETONE ON COMMERCIAL OPTICS - IT COULD REACT WITH PAINTS OR PLASTIC ITEMS. DO NOT CLEAN OPTICS IN THE FIELD - OPTICS MUST BE REMOVED FROM THE TELESCOPE AND CLEANED IN A CLEAN INDOOR WORK ENVIRONMENT. CLEANING MUST BE DONE WITH LIGHTING CONDITIONS SUCH THAT THE SURFACE DUST AND PARTICLES CAN BE BRIGHTLY ILLUMINATED AND CLEARLY SEEN. AIR SOURCES FOR BLOWING SURFACE DUST MUST BE DRY AND OIL-FREE AND HAVE AN IN-LINE FILTER FOR PARTICULATE MATTER.
NEVER USE ACETONE ON COMMERCIAL OPTICS - IT COULD REACT WITH PAINTS OR PLASTIC ITEMS.
CLEANING MUST BE DONE WITH LIGHTING CONDITIONS SUCH THAT THE SURFACE DUST AND PARTICLES CAN BE BRIGHTLY ILLUMINATED AND CLEARLY SEEN.
All of these optics have hard AR coatings which can stand up to strong cleaning agents. Reagent grade methanol or isopropyl alcohol are highly recommended. Never return unused cleaning fluid to the bottle and cap the bottle when not in use. Distilled water Small tissues such as Kimwipes
Small tissues such as Kimwipes
1. Blow off surface dust using an air source meeting the criteria discussed above. 2. Inspect for large dust particles. If present, moisten a small tissue with distilled water and coax the particles off onto the tissue. Discard tissues after single use. 3. Inspect surface for water drop stains. If present, moisten a tissue with the distilled water and lightly wipe the area to remove the dried-on material. The wiping should not be rubbing; the sum of the spring tension of the tissue and adherence due to water tension should be the dominant force between the tissue and the glass. Allow to dry. 4. Moisten a tissue and gently wipe the lens, starting at the center and going out. There should be sufficient liquid that the tissue and liquid can "glide together" across the surface, and not so much that the fluid can flow away from the tissue on its own. Discard tissues after single use and be sure that oils from fingers does not contaminate the tissue which will contact the glass. 5. Continue out until the area cleaned is within about 10 to 15 mm from the elastomer bond between the glass and the steel mounting ring. Go no further; avoid getting the liquid in contact with the elastomer bond. 6. Inspect the surface for streaks and remnant contamination. If the lens was excessively dirty it may be necessary to repeat steps 4 and 5.
2. Inspect for large dust particles. If present, moisten a small tissue with distilled water and coax the particles off onto the tissue. Discard tissues after single use.
3. Inspect surface for water drop stains. If present, moisten a tissue with the distilled water and lightly wipe the area to remove the dried-on material. The wiping should not be rubbing; the sum of the spring tension of the tissue and adherence due to water tension should be the dominant force between the tissue and the glass. Allow to dry.
4. Moisten a tissue and gently wipe the lens, starting at the center and going out. There should be sufficient liquid that the tissue and liquid can "glide together" across the surface, and not so much that the fluid can flow away from the tissue on its own. Discard tissues after single use and be sure that oils from fingers does not contaminate the tissue which will contact the glass.
ALWAYS WEAR EYE PROTECTION. NEVER LOOK INTO THE APPARATUS NEVER POINT APPARATUS AT YOUR EAR OR ANY OTHER PART OF YOUR BODY. NEVER POINT APPARATUS AT ANOTHER PERSON. NEVER STORE OR TRANSPORT CO2 TANKS IN DIRECT SUNLIGHT OR A WARM CONFINED SPACE SUCH AS THE TRUNK OF A CAR. SUCH HANDLING CAN RESULT IN EXPLOSION, ASPHYXIATION, AND DEATH. ALWAYS TIE DOWN GAS TANKS. ALWAYS WORK IN A WELL VENTILATED AREA. REMEMBER, CO2 IS A RELATIVELY HEAVY GAS AND WILL DISPLACE BREATHABLE AIR. FAILURE TO PROVIDE ADEQUATE VENTILATION CAN RESULT IN ASPHYXIATION AND DEATH. THE APPARATUS IS INTENDED FOR USE ONLY WITH CO2 AT 750 PSI. NEVER USE APPARATUS NEAR MATERIALS WHICH CAN BE IGNITED BY A SPARK. THE APPARATUS CAN BUILD UP STATIC ELECTRIC CHARGE ON ITSELF AND THE PIECE TO BE CLEANED. DO NOT CONTACT COLD METAL PARTS WITH BARE SKIN WHEN USING THE APPARATUS. FROSTBITE CAN RESULT. USE HANDGRIP, PLASTIC VALVE KNOB, AND WEAR INSULATED GLOVES. READ THIS BEFORE ATTEMPTING TO USE APPARATUS! OBSERVE ALL CAUTIONS! RETAIN THIS INFORMATION FOR FUTURE REFERENCE
NEVER LOOK INTO THE APPARATUS
NEVER POINT APPARATUS AT YOUR EAR OR ANY OTHER PART OF YOUR BODY.
NEVER POINT APPARATUS AT ANOTHER PERSON.
NEVER STORE OR TRANSPORT CO2 TANKS IN DIRECT SUNLIGHT OR A WARM CONFINED SPACE SUCH AS THE TRUNK OF A CAR. SUCH HANDLING CAN RESULT IN EXPLOSION, ASPHYXIATION, AND DEATH.
ALWAYS TIE DOWN GAS TANKS.
ALWAYS WORK IN A WELL VENTILATED AREA. REMEMBER, CO2 IS A RELATIVELY HEAVY GAS AND WILL DISPLACE BREATHABLE AIR. FAILURE TO PROVIDE ADEQUATE VENTILATION CAN RESULT IN ASPHYXIATION AND DEATH.
THE APPARATUS IS INTENDED FOR USE ONLY WITH CO2 AT 750 PSI.
NEVER USE APPARATUS NEAR MATERIALS WHICH CAN BE IGNITED BY A SPARK. THE APPARATUS CAN BUILD UP STATIC ELECTRIC CHARGE ON ITSELF AND THE PIECE TO BE CLEANED.
DO NOT CONTACT COLD METAL PARTS WITH BARE SKIN WHEN USING THE APPARATUS. FROSTBITE CAN RESULT. USE HANDGRIP, PLASTIC VALVE KNOB, AND WEAR INSULATED GLOVES.
READ THIS BEFORE ATTEMPTING TO USE APPARATUS!
OBSERVE ALL CAUTIONS! RETAIN THIS INFORMATION FOR FUTURE REFERENCE
1) Use at least 99.99% pure medical grade carbon dioxide (CO2) at a nominal tank pressure of 750 psi. Some critical cleaning operations will require even better grades of gas, and purities of 99.9999% are available. Test all cleaning procedures first on a small expendable sample. 2) Make sure CO2 tank has a siphon or else tip tank on its side so that liquid carbon dioxide can enter apparatus. ALWAYS TIE GAS TANKS DOWN! Also, it is best to select a larger tank over a smaller one. Some contaminants come off the inner wall of a tank and a large tank has a smaller surface to volume ration than a smaller one. A 40 to 50 lb. tank is best. 3) Remove aluminum foil covers on each end of apparatus and make sure plastic or cardboard washer is in CO2 nut (tank end of line; see p. 5) before connecting apparatus to tank. Tighten carbon dioxide nut to about 10 ft.-lbs. 4) Make sure all valves are closed before use. Then crack tank valve open slowly. Next, slowly open point-of-use valve (hand held valve) by not more than 1/16th of a turn. At first only CO2 gas will vent from the apparatus. Wait at least 3 seconds for the snow stream to begin. Longer delivery lines may require a longer wait. Adjust flow at the point-of-use valve for your application. 5) Before first use of the apparatus, let CO2 flow through the apparatus for at least 20 seconds. This will purge the line of any slight residual dirt or oils. 6) Occasionally CO2 tanks are badly contaminated with oils, so test the system on a test object (such as a clean microscope slide) first before each new gas tank is used. 7) Never dwell on one small part of an area to be cleaned. All industrial and medical grade CO2 is contaminated with small amounts of oil, which can leave a spot over a prolonged period of time. Only "spectral grade" gases have non-detectable hydrocarbon levels. Typically, the jet of CO2 snow and gas emerging from the apparatus should be about 12-18 inches long and should make an angle of 45 (to the surface to be cleaned. The distance from the exit end of the apparatus (see p. 5) to the surface should be about half the jet length. The jet should be swept across the surface at a rate of at least 1 square foot in 20 seconds. Further bombardment of the surface with carbon dioxide snow will not appreciably improve surface cleanliness. 8) After use, shut tank valve. Then open point-of-use (hand held) valve to bleed high-pressure CO2 from the apparatus. When hissing stops, shut point-of-use valve for storage. This latter precaution will prevent dirt from entering the system, and the unexpected discharge of high-pressure gas the next time the system is started up. 9) If apparatus should plug for any reason during operating, shut all valves, bleed the apparatus (as in step 8 above), let apparatus return to room temperature, then try to use apparatus again. If the apparatus will not bleed let the apparatus reach room temperature with all valves shut; then bleed the system. If none of these procedures is successful in bleeding the system, you will have to loosen the CO2 nut VERY SLOWLY AND CAREFULLY to relieve the pressure. If damage is permanent, label apparatus for repair and inform personnel responsible for equipment. 10) Never run the carbon dioxide snow cleaning apparatus for more than 5 minutes continuously. After such a time period, stop work, bleed the system (as in step 8 above), and allow apparatus to return to room temperature. You may then resume work. If ice builds up on the apparatus during use in a humid environment, stop work, bleed the system (as in step 8 above), and allow apparatus to return to room temperature. You may then resume work. 11) When the pressure gauge reading drops below 750 psi, the liquid CO2 is depleted and it is time to get more CO2.
2) Make sure CO2 tank has a siphon or else tip tank on its side so that liquid carbon dioxide can enter apparatus. ALWAYS TIE GAS TANKS DOWN! Also, it is best to select a larger tank over a smaller one. Some contaminants come off the inner wall of a tank and a large tank has a smaller surface to volume ration than a smaller one. A 40 to 50 lb. tank is best.
3) Remove aluminum foil covers on each end of apparatus and make sure plastic or cardboard washer is in CO2 nut (tank end of line; see p. 5) before connecting apparatus to tank. Tighten carbon dioxide nut to about 10 ft.-lbs.
4) Make sure all valves are closed before use. Then crack tank valve open slowly. Next, slowly open point-of-use valve (hand held valve) by not more than 1/16th of a turn. At first only CO2 gas will vent from the apparatus. Wait at least 3 seconds for the snow stream to begin. Longer delivery lines may require a longer wait. Adjust flow at the point-of-use valve for your application.
5) Before first use of the apparatus, let CO2 flow through the apparatus for at least 20 seconds. This will purge the line of any slight residual dirt or oils.
6) Occasionally CO2 tanks are badly contaminated with oils, so test the system on a test object (such as a clean microscope slide) first before each new gas tank is used.
7) Never dwell on one small part of an area to be cleaned. All industrial and medical grade CO2 is contaminated with small amounts of oil, which can leave a spot over a prolonged period of time. Only "spectral grade" gases have non-detectable hydrocarbon levels. Typically, the jet of CO2 snow and gas emerging from the apparatus should be about 12-18 inches long and should make an angle of 45 (to the surface to be cleaned. The distance from the exit end of the apparatus (see p. 5) to the surface should be about half the jet length. The jet should be swept across the surface at a rate of at least 1 square foot in 20 seconds. Further bombardment of the surface with carbon dioxide snow will not appreciably improve surface cleanliness.
8) After use, shut tank valve. Then open point-of-use (hand held) valve to bleed high-pressure CO2 from the apparatus. When hissing stops, shut point-of-use valve for storage. This latter precaution will prevent dirt from entering the system, and the unexpected discharge of high-pressure gas the next time the system is started up.
9) If apparatus should plug for any reason during operating, shut all valves, bleed the apparatus (as in step 8 above), let apparatus return to room temperature, then try to use apparatus again. If the apparatus will not bleed let the apparatus reach room temperature with all valves shut; then bleed the system. If none of these procedures is successful in bleeding the system, you will have to loosen the CO2 nut VERY SLOWLY AND CAREFULLY to relieve the pressure. If damage is permanent, label apparatus for repair and inform personnel responsible for equipment.
10) Never run the carbon dioxide snow cleaning apparatus for more than 5 minutes continuously. After such a time period, stop work, bleed the system (as in step 8 above), and allow apparatus to return to room temperature. You may then resume work. If ice builds up on the apparatus during use in a humid environment, stop work, bleed the system (as in step 8 above), and allow apparatus to return to room temperature. You may then resume work.
11) When the pressure gauge reading drops below 750 psi, the liquid CO2 is depleted and it is time to get more CO2.
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