Posts Made By: Mitch Feller

My wife gave me a Meade 15mm Series 4000 plossel eyepiece a few months ago. Last weekend, I tried to put in a filter and discovered that the inside diameter is too large for the filter to grip the threads and it just falls out. I've checked against other filters and eyepieces and the problem is definitely with this eyepiece. (The outer diameter is fine.)

Meade customer service said they would replace it but I don't want to send it out and risk a 4 week turn-around until mars season is winding down. I've thought about wrapping the filter in teflon tape but I would need to remove the tape if I wanted to use the filter in other eyepieces. I also worry about small pieces of the tape coming off and fouling the lens.

Just wondering if anyone had any thoughts / suggestions.

Thanks!

I recently bought a used dob. The secondary has a heater wired in it. Coming out of the secondary housing is a wire with a transistor on it that I assume is a temperature sensor or something, an LED, and power wires that terminate in a 9V battery type connector.

Any thoughts as to the proper voltage for this? E.g., can I connect to it using another 9V-type connector but use my standard 12v supply battery or do I need to step down the 12v to 9v for this? (I don't want to burn it out by accident).


Thanks.
- Mitch

I recently got a used 13.1" custom dob (sonotube) and am planning on adding a fan to decrease the cool-down time. I don't want to cut into the tube to pull air across the mirror face and so am going to mount the fan on the back of mirror cell assembly. (The fan I have is a 4x4x1" 12v fan from a computer).

Does anyone have input re: whether it better to have the fan blowing air towards the mirror through the existing holes in the cell assembly or have the fan pull air away from the mirror?

Thanks.

Today’s “astronomy picture of the day” (http://antwrp.gsfc.nasa.gov/apod/ap030515.html) has something like this from the 1/2000 lunar eclipse. The picture was taken with a fixed mount and shows the moon trail from full to eclipse totality. Another picture at http://antwrp.gsfc.nasa.gov/apod/ap001013.html is similar but shows the whole eclipse

The idea that "everything is moving away from each other" is somewhat of an over-simplification. The expansion of the universe is not about the motion of any particular star, cluster, galaxy, or other object, but with the universe as a whole. While a group of objects may be moving towards each other, in the average, things are moving apart because space itself is expanding.

It can give you a headache to try and picture it. A classic analogy is to compare the 3D universe to the 2D surface of a balloon. Cover the balloon with dots to represent galaxies. As the balloon is blown up (an expanding 2D universe), everything on the balloon's surface moves away from everything else. It gets more complex when you factor in the motion of individual objects. Replace the dots with ants, for example, and some ants will be moving towards each other even as the balloon gets larger. On the average, though, this motion is superimposed over the gradual expansion.

So, M31 can be rushing towards us while at the same time the entire universe is expanding.