64 replies to this topic

[clamchip]

From my own close calls with a long focal length 6 inch refractor:

Loosing grip of the OTA when assembling or disassembling on a ladder in the dark.

Forgetting to tighten the tube rings after balancing the OTA and moving the tube to something other than horizontal.

Someone tripping over one of my tripod legs.

I also forget to lock the shafts before I remove the counterweights. At this point the OTA is already removed but if you forget to lock the shafts in place and you remove the counterweights the saddle becomes the heavy part and it pivots around from on top to the bottom of the polar shaft crushing bones and tearing flesh in-route. This is hardest thing for me personally to remember and sometimes I tighten the drive clutch which helps but I don't like upsetting my clutch adjustment.

Robert

[amicus sidera]

Thanks, Robert, I can well envision how those scenarios can lead to damage.

On any refractor over 4" aperture, or EQ reflector over 8", it'd seem like a good idea to either have another set of hands assisting during setup and breakdown (not usually feasible, I know), or a checklist of sorts, mental or otherwise, to keep procedures in their proper order... that, and not hurrying when dealing with such big tubes. Believe me, I've dropped a few OTA's in my time, and it was almost always due to haste on my part.

Keeping a big stick handy to thwart any potential tripod trippers wouldn't hurt, either.

[tim53]

Here's how:

Put the lens and cell on a coolwhip tub (or equivalent, depending on the size of your lens), take the retaining ring off, and lower the cell to the table top around the lens. I suspect mine got chipped by someone trying to put it back in the cell by lowering it, having it get cockeyed when they "let go", since they can't hold onto the lens when it's inside the cell.

This person was likely completely inexperienced, as the two lens elements were not aligned at all, though the alignment marks were plain to be seen. In my pic above, the elements are aligned, which is why the marks from the spacers are double, showing where they were before I realigned the marks.

-Tim.

[amicus sidera]

Interesting, Tim, and I can envision someone trying to drop lens into cell, instead of vice-versa, and getting into trouble.

Incidentally, I was cruising the CN Classifieds when I spotted this neat-looking item:

"Scope-Totes"

I don't know how well they'd prevent refractor disasters like dropping the tube, but it seems like they might work fairly well, if you're decently strong.

Attractive young lady holding that big OTA, as well.

[clamchip]

I have a graph comparison of Brandt correction, if someone can tell us anything from this about the lens design. It may not be a Fraunhofer. Corrected for visual range 5100-6500A. I don't know if this information is scientific data or advertising?
I do want to try stopping down the lens to 5" and post the results.

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[clamchip]

Scope-Totes looks like a good idea!

Robert

[clintwhitman]

Tim where is the tissue for the cool whip tub top?
The 9" triplet on a 1 gallon Change jug full of change. with puffs tissues taped to the top.... LOL

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[tim53]

Hey, my cool whip tub was clean, and it's softer than glass!

-Tim.

[amicus sidera]

Tim where is the tissue for the cool whip tub top?
The 9" triplet on a 1 gallon Change jug full of change. with puffs tissues taped to the top.... LOL

OMG, it's The Pearl, all nekkid!

[clintwhitman]

Fred,
Did you note how thick the center lens is? The total thickness is over 3" Shes got some junk in her trunk!!

[clintwhitman]

Hey, my cool whip tub was clean, and it's softer than glass!

-Tim.

Might be softer than glass but coatings are not glass and vary widely in hardness. Better soft than sleeky!!

[amicus sidera]

Yessir, Clint, that is one impressive lens!

, indeed!

Happy is the man who possesses such glass...

[clamchip]

Yes it sure is an awesome hunk Clint! and no clam chips!

Robert

[PhilCo126]

Superb refractor and an amazing project. I hope this book could elaborate a bit about the spacing between lens elements:
Classic Telescopes: A Guide to Collecting, Restoring, and Using Telescopes of Yesteryear ( By Neil English = known author from the Patrick Moore's Practical Astronomy Series )

[clamchip]

Thanks for reminding me about that book. I meant to order one when it first printed but somehow forgot.

Robert