Frequently Asked Questions
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Optical Index and Edge Support
It is important to correctly edge support the primary mirror in the mirror cell. Small edge support
errors have the potential to severely degrade image quality. Please follow the instructions below
to maximize the performance of your telescope.
- Optical Index Arrow: There is an optical index arrow on the rear surface of your Galaxy
Optics primary mirror. Rotate the primary mirror in the mirror cell so the optical index
arrow is placed at zero degrees. The arrow should be pointed straight up when the
telescope is horizontal to the horizon. The optical index is the position your primary
mirror was tested in to achieve the least amount of flexure in the mirror substrate when
observing at angles low to the horizon.
- The width of the radial support belt is also important. We have found that 1.50” (40mm)
width nylon webbing works best on our 2” thickness optical substrates.
- The 1.50” width nylon webbing supports the lower 180-degree circumference of the optic.
The belt should be exactly centered on the 2” sidewall edge of the optic.
- The sling/belt should hang straight down from the connecting device, clamp, bolt, etc. to
the point where it first contacts the sidewall edge of the mirror. The belt may pull slightly
outward and away from the 2” sidewall edge of the mirror. The belt should not pull inward
or wrap around the mirror above the 180-degree points.
- The optic must hang straight down with no lateral strain. Adjust the sling/belt clamps,
bolts, etc. either forward or backward in conjunction with the collimating bolts so the optic
hangs with no forward or twisting lateral forces.
- Please contact Galaxy Optics for information concerning the edge support design for
equatorial telescope mirror cells.
TELESCOPE MIRROR CLEANING PROCEDURE
Supplies: distilled water, liquid dish washing detergent, acetone, 3Ó or 4Ó width sterile cotton gauze - Kerlix or 100%
cotton squares available at Walmart, trigger spray bottle - US Plastics Corp #66059, 1-800-537-9724, 6 Ounce Boston laboratory
bottle with Yorker dispensing cap - US Plastic Corp #66104, 1-800-537-9724, soft white cotton washcloth, 6Ó to 8Ó diameter
Manton laboratory cork ring Ð Optics Planet # M3-LB-55015, 1-800-504-5897, thin green nitrile gloves - powder fee.
Procedure: Part 1 Remove the mirror from the telescope and carefully clean the back, edge sidewall and bevel using water and a clean soft cotton cloth. The diagonal may be rinsed using distilled water instead of wiping with a cloth. Place the primary mirror on a large sturdy worktable in the vertical position and trigger spray the optical surface from top to bottom several times with distilled water to loosen and remove dust. You may want to place a towel under the optic for this. Note: please have someone help you if your mirror is 16Ó or more in diameter. Next, place the mirror face up on top of the cork ring. The cork ring acts as a table for the mirror. Make sure the optic is well centered for stability. Spray the mirror with distilled water and place two or three drops of liquid detergent at the center. Stack two or three cotton squares and spray them with distilled water and soak-up the detergent. Then, gently drag the cotton squares in a spiraling motion from the center of the mirror and work your way out towards the edge. If the cotton becomes excessively soiled, say halfway, use a new freshly wetted cotton wipe and a small amount of detergent and continue. Always use the smallest amount of detergent possible as an excessive amount makes it very difficult to remove. Next, tip the mirror up to the vertical position and trigger spray it with distilled water several times. Always spray rinse from top to bottom to remove the detergent. Use a hair dryer to blow the water droplets off the optical surface, then wipe the edge and back dry with a clean cotton cloth. This cleaning procedure can be used out in the field and even with the mirror in the telescope for 18Ó and larger diameters. Please note that you cannot clean the edge sidewall and the back of the mirror if you elect to clean it in the telescope. Use the same procedure for the diagonal mirror.
Procedure: Part 2 This procedure is for the once or twice a year "Super-Cleaning". Use the procedure described in Part 1 but do not blow the water droplets off the mirror. Place the wet optic face-up on the cork ring. Have plenty of cotton squares or Kerlix ready to use. Wear the nitrile gloves when handling the cotton and acetone. Nitrile is insoluble in acetone and will prevent contamination of the cotton. Place a small amount of acetone (extremely flammable) into the polyethylene Boston laboratory bottle. Stack two or three cotton squares and drip a small amount of acetone on them. Use just enough acetone to slightly dampen the cotton, do not soak it. Starting on one side of the mirror, wipe the optical surface with the cotton squares in straight lines coming towards you and work your way across the optic. When water droplets start to form in the trail of the wiping, discard the wipe and continue where you left off with a fresh wipe. Do not be concerned about any water droplets you may have missed, you will remove them on your way back across the surface. Continue with the wiping until you reach the opposite side and then work your way back across the optic using fresh cotton/acetone wipes as needed. Be sure to only use one side of the cotton for wiping. Tip: practice on a 6Ó or 8Ó shaving mirror.
Your mirror will be "Super Clean" at this point. If there are any localized streaks on the surface you may huff on that area with your breath and wipe with a fresh cotton/acetone wipe. If you work carefully, your optic will not be scratched or sleeked. The most important part of this procedure is to make absolutely sure that the bevel and edge of the mirror are clean. If your optic is scratched or sleeked, you may have dragged dirt onto the surface from the bevel and edge. Enjoy your "Super-Clean" optics.
"GALAXY OPTICS" assumes no liability whatsoever for the use of acetone in this procedure. Acetone is extremely
flammable. Use no sources of ignition near or around acetone.
Warning: The use of spray on film type optical cleaning agents will void your optical coating warranty.
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