Wednesday, March 6, 2013

Cleaning Objectives

I've had my SV4 for several years, since 2004.  It spent most of the early time going in and out of the case, sometimes right after observing.  Most of the time it was dry when put away.

Late in 2012, I was aware of some severe dewing issues when observing in the back yard.  There were problems with bad connections on the dew heaters (which have been solved by use of hot melt glue).  One particularly bad morning, I saw that there was dew forming behind the objective!

On that day, I also saw that the SV70ED had dew that appeared to be inside, between the elements.  This was not good.

At that time, I figured out what to do about the dew heaters and I also started a practice of putting silica gel sachet packs just inside the caps.  This has dried out the scope nicely and kept things clear.

I was still worried about the apparent dewing on the inside of the tube and how it showed some dust motes that had spread a little over time.  Fearing fungus, I wanted to find a way to clean the inside of the scope.

Cleaning the inside of the SV70ED was easy and I was able to do it with a microfiber cloth once I'd unscrewed the scope tube from the focuser.

It wasn't until Vic posted on the yahoo group here the procedure to disassemble the larger scope body that I felt confident enough to open the SV4.  Once I read this post, I knew enough to do it.

I removed the scope from the rings and clamps (a chore in itself) and then pushed the dew shield back.  The lens cell was a little stiff to open, but once I got it started, it just spun off.  There are heavy pipe threads on the cell, so there's little chance to cross them.  I dabbed a microfiber cloth with some methanol and wiped the inside of the glass after using the puffer.

Now the inside of the cell is as clean as I can get it.  There are a few marks where debris had sat on the glass for a long time, leaving a defect in the multi-coating.  At least the glass is clean and there will be less opportunity for fungus to start.

I also noted that the focuser was loose on the scope tube.  Probably because of my struggles with clamping and binding causing a torque on it.  It's now tight.

No pictures of the procedure.

Also during this time I put a nylon 1/4-20 thumbscrew on the camera to thermally isolate it a bit more.