Regluing Secondary Mirror

The edge of the secondary holder was pretty tight against the mirror and I read that sometimes the holder can pinch the mirror and mess with the views.  So until I can afford a better secondary mirror I decided to pry the mirror off and sand the holder.

  I also read that sometimes the mirror is held on with three pieces of double sided tape and sometimes silicone.  I had no idea what was holding this mirror so I drilled a couple of holes in the back of the holder hoping to be able to push it out from behind but the mirror was pressed in pretty tight and I couldn't get it to budge.  So the next step was to pry it loose from the front.
  I used a couple little flat screwdriver tools from my fishing reels and proceeded to follow the edge of the mirror around the holder to loosen it up a bit.  It was in pretty tight so I went slow and easy so I wouldn't chip the mirror.  Then I put in both tools and slowly pried the mirror up until I could feel the glue popping loose.

Finally I felt the last of the glue pop loose and the mirror was free!  This process took me about 30 minutes as I was being really careful not to chip the glass or slip and scratch the face of the mirror.  Very nerve wracking half hour!  The folks at Apertura just put globs of silicone on the back and pressed it in tight.  There was more silicone on one side than the other.

I scraped the silicone off with a razor blade then used alcohol as a degreaser for the back. Then I started on the holder.  I sanded the inside edge and kept checking until the mirror fit without touching the sides.  Once I got it to my liking I used alcohol to clean the holder edge where the silicone would sit.  

While the mirror was out I blackened the edges better with a Sharpie.  Being careful not to get it on the face of the mirror.

In my reading I found that there is supposed to be a space between the holder and the mirror so that the mirror can expand and extract on top of the silicone as it cools and not touch the holder itself.  I saw that most used toothpicks as spacers.  Since there was no way to pull out the toothpicks after the mirror was glued in , I figured I could use a thin cord that was about the same thickness as a toothpick.  For the silicone I used black Aquarium sealant from Petco.

I marked 3 spots with the sharpie where I would put the silicone then threaded the cord through the holes I drilled when trying to push the mirror out.  I also threaded some cord through the center screw holder.  Then used small pieces of tape to keep them in place.

Three globs of silicone and the holder is ready for the mirror!

I cut up a business card and used them to center the mirror in the holder.

I let the mirror dry for a couple days then pulled out the cord.  It worked like a charm!  The mirror was stuck on pretty good and there was a space between the mirror and the holder.  I screwed on the little holder at the top edge of the mirror and it was ready to be installed.  In my excitement to install and collimate the newly redone secondary I forgot to take a picture!  

The final step is to wait for the clouds to clear so I can try it out!

Update:

The secondary is working great!  Pinpoint stars in the clusters and great definition in Saturn.  Next is to take it out to my dark spot on a moonless night!

Messier Objects List

I've been out on the balcony a couple times and to my dark spot once (which was a different camp site than usual so I had trees blocking some of the sky).   There's been lots of clouds lately so I can't do much viewing.  Here's the Messier objects list so far.  I'll update it as I check off the objects.

 1          23          45          67          89

 2          24          46          68          90

 3          25          47          69          91

 4          26          48          70          92

 5          27          49          71          93

 6          28          50          72          94

 7          29          51          73          95

 8          30          52          74          96

 9          31          53          75          97

10         32          54          76          98

11          33          55          77          99

12          34          56          78        100

13          35          57          79        101

14          36          58          80        102

15          37          59          81        103

16          38          60          82        104

17          39          61          83        105

18          40          62          84        106

19          41          63          85        107

20          42          64          86        108

21          43          65          87        109
22          44          66          88        110

    

  List updated 11-26-14
  59 Messiers
List updated  1-28-15
  66 Messiers
List updated  2-18-15
  95 Messiers
List updated  3-16-16
  106 Messiers

First Light

I put the scope out to cool around 8:45 and went out an hour later.  The clouds were moving in but I was anxious to test the mirror.  It is really humid and not a very good night for viewing.  This is the closest clear sky chart to me.

From my balcony I get views from the Northeast to the Southeast.  The garage lights in the complex are pretty bright so I use tarps to block them the best I can.  I could see Vega so my first stop was the M57 the Ring Nebula.  I could see it right away with the 28mm!  I had to use averted vision but there it was!  With the 11mm and 6.7mm I could make out the star next to the Ring.  Next was the globular M56.  I only saw it briefly with the 11mm before the clouds moved in.  I could resolve some of the stars in the cluster. 

 I did a quick star test on Vega with the 6.7mm just to see what it would look like.  The defocused star was boiling.   Again not a very good night I know the sky has to be perfect and I'm not even sure how to do it right but I was curious. 

I could see Saturn in Libra just above the roof line so I turned the scope and put in the 28mm.  With the warbly sky and the heat from the roof the planet was going in and out of focus but when it was in focus it was sharp and crispy.  I went through all the eyepieces and was very impressed.  I could easily see the Cassini Division with the 11 and 6.7.  And I could also see some bands on the planet itself.  The moons were easily visible.  So far so good with the newly refigured mirror and I can't wait to take it out to my dark site!

Saturn and the position of the moons

Collimating

Not to get too deep into it but I start the collimation process by using the Catseye teletube combo tool to line up the hotspot under the cross hairs (the secondary has already been centered under the focuser).  (Not a very good picture!)

Then adjust the primary to fit the hotspot into the center ring of the combo tool.

Next is the XLKP autocollimator.  Turn one of the primary screws to "decollimate" the primary so that all 4 reflections are seen. 

Use the knobs on the secondary to align the hotspot reflection with the inverted reflection.  Then use both the combo tool for the primary and autocollimator for the secondary to fine tune the mirrors.  Going back and forth between the tools to make sure everything gets lined up.

Simple enough!  But it actually takes me a long, frustrating, time to get them lined up.  And even now I'm still not sure if it's right!  The only way to tell is to view and see if I'm happy with what I see.

The Mirror

It finally arrived after months of being refigured by Swayze Optical and coated by Spectrum Coatings!

The refiguring took the longest but it looks excellent!  The edges are more uniform and look a lot cleaner than before.  That's the only way I can tell there was work done by just looking at it.  I sent it in for test and refigure because of the stars looking like cotton balls instead of pin points.  The true test will come when I can view with high power eyepieces.  But of course, it looks like it will be cloudy all week.

The coating was quick and only took a few weeks.  I chose the recommended standard aluminum/quartz (pal) 91% coating and it looks excellent too!  Smooth and shiny!  Again the true test will come by viewing but I'm sure everything will turn out better than expected!

I paid for the center spot to be applied but a Catseye triangle was put on instead of the hotspot that I asked for but it was no big deal since I had an extra hotspot.  Before peeling the triangle I checked it with the Catseye template and it was centered perfectly.  I've never tried collimating with the triangle but from what I've read the hotspot is easier and for me the easier the better!

The hotspot being applied

Perfect!

Putting the mirror in the cell.  The lugs of the hotspot are aligned with the primary collimation bolts for ease in adjusting the mirror.  To avoid pinching, the clamps are not touching the surface but are tightened just enough to keep the mirror from falling.

Back on the tube!  Next step, collimating.