Archive for March 2013

Cleaning A Telescope Mirror – April 13th 2013

March 18, 2013

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The following is the method I’ve used many times over the years to “successfully” clean telescope mirrors.  

I reviewed a variety of sources to get my ideas.  I especially liked the instructions from Sherrod and Koed’s A Complete Manual of Amateur Astronomy, and an article from the March 1992 Astronomy Magazine by M. Porcellino.  This procedure is comprised primarily from those two sources, but I have included some additional steps, a few changes and some other thoughts of my own. 

Materials:

Cotton balls  (100% cotton)  – Be sure to store the cotton balls in a sealed zip-lock bag

Blower bulb from a photo supply shop

100% Camel hair brush – Do not touch the bristles with your fingers or hands, and be sure to keep the brushes in a sealed bag. 

Three gallons of distilled water

One teaspoon of liquid “Ivory” dishwashing detergent

Two clean folded bath towels  (not to have been washed using fabric softener) 

     First, wash your hands and remove all rings.   (You may  use surgical gloves if you so desire)

     Now its time to remove the mirror cell (with mirror) from the telescope.  Using a permanent marker, mark two lines on the side of the mirror and also on the cell.  This will allow the same mirror/cell orientation after the cleaning process.  Carefully remove the mirror from the cell.  Tilt the mirror on its side and blow any loose particles from the surface with the blower bulb.  Take the camel hair brush, with care and a very light touch “whisk” the surface, removing any loose debris that has remained.  

     Typically the mirror cleaning process is carried out in the kitchen sink.  It’s best to wash the sink thoroughly using dishwashing detergent and rinsing with water from the faucet.  After this, wipe the sink with alcohol to remove any oil or grease residue.  Place one of the folded towels in the sink and carefully lay the mirror on the towel.  Turn on the water and flood the mirror surface for a couple of minutes.  Next, plug the sink and fill with distilled water to a level that is about one inch above the mirror.  Pour one teaspoon of liquid dishwashing detergent into the sink with the mirror, and let soak for about five minutes.  

     Secure one cotton ball by the corner to insure that finger oil is not deposited onto the mirror.  Next, saturate the cotton ball with water and pull it gently across the mirror…using only the weight of the saturated cotton ball.  After each crossing, dispose of the cotton ball, and proceed with another cotton ball (make sure the mirror is completely submerged during the entire cleaning  process.)  If the mirror is really dirty, I’ve found it necessary to use the same procedure, but pulling the cotton balls crossways.   

      The rinse process:  Turn on the faucet and flood the mirror, and then gently put one hand under the mirror and lift out of the cleaning water.  Rinse the mirror for at least two minutes, then turn off the faucet, and immediately start pouring one gallon of distilled water over the mirror for the final rinse.   Caution:  Be careful not to hit the faucet with the mirror!

     Optional:  After the first rinse, pour a bottle of 91% isopropyl alcohol over the mirror to remove any soap residue.  Rinse again under the faucet and then for a final rinse, pour one gallon of distilled water over the mirror.   (Dr. James Dire of Hawaii uses this procedure and reports excellent results.)  

My most recent cleaning, my final process was to pour an entire bottle of 91% isopropyl alcohol over the mirror as the final rinse, and it seemed to have worked fabulous! 

      Carefully position the mirror onto the second folded towel at an angle to allow the remaining distilled water to drain from the surface.  You can use the blower bulb to chase drops of water over the edge.  Do not use any other means to dry the mirror.  

      You’re almost through.  Now, carefully install the mirror back into the cell using the alignment marks.   You are now ready to tighten the mirror clips.  I use a sheet of notebook paper as a gauge.  I leave just enough space between the clips and the mirror to be able to slide a corner of  the notebook paper between the two.  This will leave a very tiny amount of space.  The clips should not be tightened down against the mirror, as their only purpose is to keep the mirror secure, but not tight.  This will insure that the mirror is not stressed, especially during temperature changes. They should, however, be tight enough to keep the mirror from moving in the cell.  The clips should have cork pads glued onto the area that touches the mirror. 

Disclaimer:  This method has allowed me to clean telescope mirrors with excellent results.  It should, however, be noted that your results may vary.  Mirrors and coatings are very delicate, so be careful, use good common sense and care.   

Roger Ivester 

Melotte 71 – Open Cluster In Puppis – Sketch and Notes – February Observers Challenge Object

March 3, 2013

Melotte 71, Observers Challenge complete report:  Please click on the following link. 

FEBRUARY 2013 OBSERVERS CHALLENGE – MEL-71

Date of observation:  February 28th 2013

Melotte 71:  Open Cluster in Puppis

Telescope: 10-inch f/4.5 reflector, with the employ of an 11 mm eyepiece and a 2x Barlow for a magnification of 208x.  I was observing from my backyard, with a NELM of around 4.5-4.8, due to moderate light pollution.  One of the most notable features of this cluster is a triangle of three brighter stars with the apex star being due south away from the cluster.  The brighter western-most star of the triangle has a subtle red color.  The star at the east leg of the triangle becomes a double at high magnification, also many of the fainter members begin to appear, but intermittently, and not constant.   When using low power, the cluster appears as little more than a nebulous patch with only a few of the brighter stars being noted.  The following sketch was made using a 5 x 8 blank note card, a No. 2 pencil, and an eraser, with the colors being inverted using a scanner.    Roger Ivester 

Melotte 71 - Revised

Observation by Debbie Ivester  (Date: February 28th 2013) 

Telescope:  I used a 10-inch reflector at 208x for the following notes:  Debbie 

Melotte 71: Open Star Cluster in Puppis 

I could see the triangle of three brighter stars pretty easily, but the main cluster to the north appeared as a faint haze.  After careful observing, a few of the brighter stars appeared.  The cold breeze was causing my eyes to water, which gave me difficulty in my attempt to observe this object.  It’s really hard for me to be outside when the temperature is below freezing, and especially with an icy wind.  I could hardly wait to get in the warm house!   

Debbie Ivester