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ATM: 16" ultra-compact, ultra-light dob

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19 replies to this topic

#1 asaint

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Posted 29 July 2005 - 01:14 PM

ATM: 16" ultra-compact dob

#2 Jeff

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Posted 29 July 2005 - 01:53 PM

Time to start looking for some carbon fiber... Very impressive Craig! I'm curious how well that drive works for tracking.

#3 stringscope

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Posted 29 July 2005 - 04:45 PM

Very nice indeed Craig.

You don't mention details of the truss tensioning springs. I would be very interested to know the spring compression distance and the compression force. The reason is I have just built an 8" stringscope and I am contemplating the potential to scale the spring tensioning concept to larger scopes.

Cheers

#4 Craig C

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Posted 29 July 2005 - 05:26 PM

Thanks Ian!
I didn't use springs. The truss tubes "unscrew" to extend and create the string tension. I used this techinique on my 14 also and it works great. This is Dan Gray's recommended approach, too.
Craig

#5 Craig C

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Posted 29 July 2005 - 05:30 PM

Thanks Jeff!
I'll post an update on the drive performance when I've really checked things out. Unfortunately, I had a little accident on Monday and scratched the primary, hopefully just the coating. So the mirror's back at L & L getting coated. I hope to have it back Monday and I'll check everything out so that I can take it to the Mauna Kea VIS next Friday and/or Saturday.
Craig

#6 Greg K.

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Posted 29 July 2005 - 06:39 PM

Very impressive!

#7 Dave Chadsey

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Posted 29 July 2005 - 07:31 PM

Amazing and impressive Craig.

Dave

#8 erik

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Posted 29 July 2005 - 07:44 PM

great job, craig! 16" of aperture that's airline portable- incredible!! :waytogo:

#9 Oldfield

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Posted 30 July 2005 - 07:49 AM

single hand portable.... amazing!!!

#10 half meter

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Posted 30 July 2005 - 04:32 PM

I'm very impressed. Airline portable, including tracking!

I really want to hear your impressions after you get it to the top of Mauna Kea :D

#11 mirage

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Posted 31 July 2005 - 12:36 PM

Very cool 'scope! For airline portability, I guess you'd have to check the truss poles?

#12 Craig C

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Posted 31 July 2005 - 01:09 PM

I'm probably going to end up cutting the truss poles in half, so that they are more "manageable". I did that with the carbon fiber poles on my 14, and that works fine.

Thanks!

Craig

#13 rboe

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Posted 31 July 2005 - 02:26 PM

How's that focuser working for you? I take it that salt air and/or VOG are not a problem for you?

My mirror alone is 28lbs - and it's 16". That is quite a feat there. Ever thought of adding some koa as trim or wear bars or something?

Nice job by the way. I need to think up some excuse to beg a look through it some day! :wron:

#14 Guest_**DONOTDELETE**_*

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Posted 31 July 2005 - 09:24 PM

Unbelievable! That's simply amazing what you've done there to get that scope so small. My hat's off to you.

Doug :bow:

#15 ForgottenMObject

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Posted 01 August 2005 - 06:56 AM

Absolutely mind-boggling...

Wow!

#16 Craig C

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Posted 02 August 2005 - 01:47 PM

The focuser works very nicely: very smooth and very precise.
No problems with salt or VOG where I am.
I will be storing it in soft case, maybe padded. I'll keep an eye on the "wear" points. I can always re-paint it!
Thanks!
Craig

#17 Albert

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Posted 06 August 2005 - 02:16 AM

Hi Craig,

Nice achievement. I'd like to get my hands on some of those carbon fiber panels!

I don’t know if you seriously are considering traveling with your scope. Here are some thoughts about designing a travel scope. One must consider factors other than total weight and sum of linear dimensions of the scope itself.

1) Although most major airlines follow similar rules for checked and carry-on luggage, they aren’t identical.

2) Rules also vary for international and domestic flights. For example, on United domestic flights, each passenger is allowed two checked bags with a maximum size of 62 inches (length + width + height) and a maximum weight of 50 lbs each. On most international flights, each bag can weigh 70 lbs. United’s website states “Carry-on bag dimensions should not be more than 9" x 14" x 22" (length + width + height) or 45 linear inches (the length, height and width added together).” The bulk of your scope (minus struts) just meets the 45 linear inches criterion. However, I don’t know if all airlines use the more general rule. And, I suspect there is a high probability the scope would be denied access at the gate even at United. The gate attendant may not read a tape measure the same way you did and could always point out that the scope doesn’t conform to the 9” X 14” X 22” set of dimensions. As another example, If you fly on domestic flights on Qantas (Australia), the weight limit for a carry-on is only 15 lbs. It pays to check the airline’s website and print out the rules before you go (and design).

3) Airlines may restrict carry-on luggage at the gate, even when luggage conforms to published size and weight limits. If the scope is meant to be carried on board, do you have an effective backup plan? Will your intended carry-on withstand being handled as checked luggage?

4) Most airlines allow luggage to exceed the “free” limits to some extent, but usually at significant extra cost.

5) Since airlines limit the weight and size of your total carry-on and checked baggage, the travel scope must not prevent you from taking other essential items - clothes, eyepieces, charts, struts, ladder or step stool, etc. Will you pack expensive eyepieces in your checked luggage?

6) All carry-on and checked luggage is subject to search. An object such as a packed telescope will attract attention. The design must allow quick and easy inspection with little risk of damage. You may or not be present when the inspection is made.

7) If the scope is damaged during the trip, can it be repaired easily? Will spare parts be available? What spare parts do you plan to take?

I recommend trimming the corners of your upper baffle. It will be smaller, lighter, and also safer. Too easy for someone to jab an eye on those corners that will be difficult to see in the dark. Besides, the corners provide little or no baffling.

You mentioned that the scope balances well with 2" eyepieces. Will you also use lighter 1-1/4" eyepieces? If the scope is then bottom-heavy, the parallel struts are a good place to hang an adjustable counterweight. A section of pipe with an ID slighter larger than the OD of the struts works well with a nylon thumscrew and some non-marring spacers on the inside.

I look forward to seeing the scope sometime.

Albert

#18 Guest_**DONOTDELETE**_*

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Posted 14 August 2005 - 12:44 PM

I see a winter project coming up :D :D!!!

#19 macastronomer

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Posted 31 August 2005 - 10:49 AM

You look like a fairly tall person. Myself, I'm a bit vertically challenged (although I'm doing pretty well horizontally but that's another story).

Most 16" dobs get fairly high off the ground and this one looks to be no exception. How high is that eyepiece from the ground?

If you have some more carbon fiber laying around, a box (slip case style so the whole boxed up scope would slide in) with handle handle on it might make a decent step stool :D

Excellent job. That is a great looking scope! When are you selling it ;)

Duane

#20 David Hourdequin

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Posted 01 April 2006 - 04:01 AM

Albert, great feedback on the issues around airline portability. Thanks so much!

David in Highalnds, NC


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