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Alan1956
super member
Reged: 02/07/05
Posts: 137
Loc: Albuquerque, NM, USA
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I have been designing an ultralight 20" over the last few years, and finally got the time and permission from financing (my wife) to go ahead with the project.
Design requirements are as follows:
* 20" f4.0 mirror.
* No electronics. I enjoy the hunt.
* Protractors are allowed on the alt/az.
* Heaviest part around 50 pounds.
* Fits in the trunk of a hatchback.
* Only needs 1-2 steps from a step stool.
* Quick setup.
I just created a web site tonight, and it is here: http://www.xmission.com/~alanne/DS5/DS5Main.html. Unfortunately, my wife has the camera in Colorado, so I don't have any recent pics - such as the spider.
I will add more pictures, and shrink the ones that are there (they are huge) as I get a chance.
Alan
http://www.xmission.com/~alanne/DS5/DS5Main.html
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Alan1956
super member
Reged: 02/07/05
Posts: 137
Loc: Albuquerque, NM, USA
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Here is a picture of the scope stored.
Alan
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StarStuff1
scholastic sledgehammer
Reged: 04/01/07
Posts: 979
Loc: South of the Mason-Dixon Line
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Beautiful woodwork altho the sides of the rocker box appear to be a little thin and there might be an issue with flexure.
Just curious, what are the 4 screw/bolt heads on the side of the focuser board for?
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Tools that make objects very far away appear much closer than they actually are.
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Alan1956
super member
Reged: 02/07/05
Posts: 137
Loc: Albuquerque, NM, USA
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Very good catch.
There are two dimensions I don't know until I get the mirror (slated for early winter). One is the length of the trusses, the other is the diameter of the bearings. The diameter of the bearings changes the form of the rocker box sides. Thus, the rocker box sides are 2-3 inches too tall, and will be cut shorter. I used the same design for my 16", and didn't have any problems.
They are 4 brass nuts stored on the focuser board. They are used to snug up the attachment of the trusses to the upper cage.
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Alan1956
super member
Reged: 02/07/05
Posts: 137
Loc: Albuquerque, NM, USA
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Here's the OTA assembled:
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bbasiaga
professor emeritus
Reged: 05/10/06
Posts: 724
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Very cool. I'm in the middle of a 22" based on a similar concept. Great project, isn't it?
-Brian
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Vixen 80EDSF
Stellarvue 102ED2
Orion Atlas 11 EQ-G
15" Astrosystems Telekit w/ Discovery Optics
Lust for something Larger
Lust for something Larger than that
Past Lovelies:
Oberwerk 20x100 binocs
Meade AR5
Meade LX10 8" SCT
All sold to a good home
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Alan1956
super member
Reged: 02/07/05
Posts: 137
Loc: Albuquerque, NM, USA
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Quote:
Very cool. I'm in the middle of a 22" based on a similar concept. Great project, isn't it?
-Brian
I debated going to a 22". What f ratio are you? Why did you decide to go for a 22"? Will you be using ramps and wheelbarrow handles? Is there a thread here at cloudy nights on your scope?
Alan
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bbasiaga
professor emeritus
Reged: 05/10/06
Posts: 724
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I went to a 22" b/c it was close to double the light gathering of my 15". I went with F/4 as well, in order to try and keep the EP height as low as possible. I want to use the same two step stepladder that my wife uses with the 15" F/5 we have, and think at this focal ratio we'll be fine with that.
I don't know if I'll use wheel barrow handles or not. Frankly, we don't use the ones we have for our 15" very much, and the heaviest part of this scope will not be significantly heavier than the the 15" (due to the fact tha tthe 15" has a traditional mirror box, and a 1" thick solid wood tailgate). So I think we'll be able to do carry it like we do the 15".
The other key to this is the removable bearings. I plan to make the whole thing collapsable so we can carry it in multiple parts.
Check it out here
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3151274/page/2/view/collapsed/sb/5/o/all/fpart/1
Hopefully I'll have some more pics up soon.
-Brian
--------------------
Vixen 80EDSF
Stellarvue 102ED2
Orion Atlas 11 EQ-G
15" Astrosystems Telekit w/ Discovery Optics
Lust for something Larger
Lust for something Larger than that
Past Lovelies:
Oberwerk 20x100 binocs
Meade AR5
Meade LX10 8" SCT
All sold to a good home
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Alan1956
super member
Reged: 02/07/05
Posts: 137
Loc: Albuquerque, NM, USA
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Well, I finally have paint on the scope. The only thing that is missing is to 1) cut the trusses to length, 2) make altitude bearings, and 3) cut down the rocker box sides to match the altitude bearings.
Scope weight for the mirror box, cell and mirror are currently at 53 pounds, assuming the 1 5/8" mirror ends up weighing in at 36 pounds. Total scope weight should be about 99 pounds.
Here is a picture of the scope in it's stored configuration. Dimensions are 17"X26"X26". The 26"X26" is the baseboard - the upper cage is 25"X25", and I didn't want it being the part of the scope that hit against walls when stored.
Alan
http://www.xmission.com/~alanne/DS5/DS5Main.html
Edited by Alan1956 (11/01/09 01:26 AM)
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Alan1956
super member
Reged: 02/07/05
Posts: 137
Loc: Albuquerque, NM, USA
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Here is the scope set up:
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