Saturday, June 22, 2013

Calling It Quits On The Telescope Rebuild

I was hoping to report victory on the telescope rebuild, but I'm just surrendering.

I cut 51 inches out of the middle of the tube:






And yes, it took 19 pounds of it.

But the cutting process wasn't pretty, and neither were the results:






Worst of all, when I was done I had the same problem with the lower cage that I had with the aluminum one -- too flexible.  I am beginning to think that this is a variant of the 50 pound bike theorem.  In case you aren't familiar with it, it was first explained by a friend (okay, a gal that I was convinced that I was madly infatuated with in 12th grade, before she went to MIT), based on the problems of bicycle retention in the Boston area:

1. A 20 pound bicycle is so valuable that it requires a 30 pound lock and chain to keep it from being stolen.

2. A 30 pound bicycle is in less demand, so it only requires a 20 pound lock and chain.

3. A 40 pound bicycle is barely worth anything, so a 10 pound lock and chain are sufficient.

4. A 50 pound bicycle doesn't require a lock and chain.  Who would steal it?

This reflects bicycle and lock technology of the 1970s; today the situation is probably somewhat different.  But I think the problem here is similar:

1. A big Newtonian reflector will either be heavy and stiff or light and floppy.

2. You can have a big reflector, but you either need a $6000 mount, or it is so hard to keep in collimation that it doesn't matter what mount you put on it.

Perhaps I should just make a Dobsonian mount, and give up on using this astrophotography.  Or perhaps I will just sell the parts to someone who has more energy to devote to building a Dobsonian.

UPDATE: CloudyNights has the ad here.




2 comments:

Richard Clark said...

Speaking of Dobs, perhaps you know ...

I see a folks doing astrophotography with video cameras (lots of fairly short exposures) and photo stacking software. How much does the image move during the individual image capture? Is there stacking software available (or possible) that can correct for rotation as well as linear drift?

Perhaps you can do in software what isn't practical in hardware. :)

Clayton said...

There are tracking platforms for Dobs -- typically about $400 - $800 -- which let you track for about 30-40 minutes at a stretch. I'm not sure if this is good enough for visual only, although some claim to do adequate astrophotography with them. This may be the way to go.

But at this point, I am going to try and liberate the cash out of this set of optics, and start over.