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Equipment Discussions >> Equipment

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pgrunwald
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Reged: 08/09/09

Loc: Albuquerque, NM
Catsperch design question
      #5628802 - 01/17/13 08:13 PM

I want to build an Catsperch design observing chair. I have seen multiple designs with the cross brace on the back leg instead of under the front footrest.

I can see the back being safer because of the trip hazard being moved to the rear. Is there any stability issues moving it to the back leg?




Edited by pgrunwald (01/17/13 08:14 PM)


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mitaccio
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Re: Catsperch design question new [Re: pgrunwald]
      #5629255 - 01/18/13 01:33 AM

The majority of the weight is on the front "leg" of the chair, hence the reason most people put the cross brace there. It helps stabilize the chair when used. I have made them both ways and while the cross brace works on either leg, the front leg offers greater stability.

I also have been trying various widths of cross braces and find that while over 12" wide does offer a more stable chair, that the hazards have multiplied. I personally have my cross brace at 10" and use my own two feet for any minor additional stability needed.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Catsperch design question new [Re: mitaccio]
      #5629282 - 01/18/13 02:36 AM

Quote:

The majority of the weight is on the front "leg" of the chair, hence the reason most people put the cross brace there. It helps stabilize the chair when used. I have made them both ways and while the cross brace works on either leg, the front leg offers greater stability.

I also have been trying various widths of cross braces and find that while over 12" wide does offer a more stable chair, that the hazards have multiplied. I personally have my cross brace at 10" and use my own two feet for any minor additional stability needed.




Interesting, I would like to put the brace on the rear because it would let me position the chair a bit closer to the scope. But the stability is the issue.

Chairs like the Starbound are narrow in front and wide in the rear and have no issues with stability. The difference between the Catsperch and the Starbound is that that the attachment points for the rear leg assembly of the Starbound are widely spaced and there is no play. The rear strut attachment of the Catsperch is quite narrow and by comparison much less rigid.

How high up the chair do you go, the top run on a standard Catsperch is 42 inches?

Jon


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ThreeD
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Reged: 12/23/08

Loc: Sacramento suburbs
Re: Catsperch design question new [Re: Jon Isaacs]
      #5629585 - 01/18/13 09:59 AM

I have a catsperch pro that I built from their kit. As has been stated, most of the weight is definitely on the front. I built mine per the plans and haven't had a problem with tripping or with getting the chair positioned next to my dob.

Moving the large leg to the back seems like it would just be moving the trip hazard to a place where you might not walk as often but also might be moving a bit faster. When I getting up and sitting down I'm not moving very fast and I'm probably being a bit more careful.

Moving the large leg to the back would make it easier to place the chair. I've always been able to get me chair positioned okay but frequently that leg is a very close to the scope base.

I've read of people doing this. Do a search on google and I think you'll even find where designer of the chair chimes in refarding the change.


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Peter Natscher
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Reged: 03/28/06

Loc: Central Coast California
Re: Catsperch design question new [Re: Jon Isaacs]
      #5629599 - 01/18/13 10:08 AM Attachment (16 downloads)

With my Catsperch chair, I will sometimes sit all the way up at the highest 39" seat setting giving me an eye height of 70". I can use this chair with my 24" StarStructure Dob. I'm 6'3" and 195 lbs. and feel fairly stable sitting up that high. The front stabilization cross member is 28" wide. The red oak I used in making this chair from Catsperch blue prints is quite hard, firm, and heavy. It's mass keeps it stable. It works for me!

Quote:

Quote:

The majority of the weight is on the front "leg" of the chair, hence the reason most people put the cross brace there. It helps stabilize the chair when used. I have made them both ways and while the cross brace works on either leg, the front leg offers greater stability.

I also have been trying various widths of cross braces and find that while over 12" wide does offer a more stable chair, that the hazards have multiplied. I personally have my cross brace at 10" and use my own two feet for any minor additional stability needed.




Interesting, I would like to put the brace on the rear because it would let me position the chair a bit closer to the scope. But the stability is the issue.

Chairs like the Starbound are narrow in front and wide in the rear and have no issues with stability. The difference between the Catsperch and the Starbound is that that the attachment points for the rear leg assembly of the Starbound are widely spaced and there is no play. The rear strut attachment of the Catsperch is quite narrow and by comparison much less rigid.

How high up the chair do you go, the top run on a standard Catsperch is 42 inches?

Jon




Edited by Peter Natscher (01/18/13 10:09 AM)


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Jon Isaacs
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Re: Catsperch design question new [Re: Peter Natscher]
      #5629621 - 01/18/13 10:21 AM

Quote:

With my Catsperch chair, I will sometimes sit all the way up at the highest 39" seat setting giving me an eye height of 70". I can use this chair with my 24" StarStructure Dob. I'm 6'3" and 195 lbs. and feel fairly stable sitting up that high. The front stabilization cross member is 28" wide. The red oak I used in making this chair from Catsperch blue prints is quite hard, firm, and heavy. It's mass keeps it stable. It works for me!




I get up there too, I think the top rung on mine is 42 inches, I am a bit below that. I would like to have the chair narrow in front so I could position the chair the way I would like to. The Starbound design lets me get the chair right where I want it, the Catsperch not so much.

Jon


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nevy
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Re: Catsperch design question new [Re: Jon Isaacs]
      #5630000 - 01/18/13 02:01 PM

My front leg is 20"wide & the top rung for the seat is at 45 inches , it allows me to observe at my 16" lightbridge at zenith even on the JMI wheelie cart , it's very stable even when sitting at the maximum height, even that height is to high as I had the chair made bigger than I need.
[image]http://[/image]
[image]http://[/image]

Edited by nevy (01/18/13 02:03 PM)


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nevy
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Re: Catsperch design question new [Re: nevy]
      #5630029 - 01/18/13 02:24 PM

I think for a tall chair the front brace ( foot ) needs to be at the front for stability as tht is where all the weight is , even though my foot is 20" it doesn't get in the way as the only time it is right next to the scope base is at zenith , and even then it's in just the right place ( the lightbridge is considered wide (big) by most people) I don't think the tripping hazard is relevant because you can't trip over it when your sitting on the chair and its never that close to the scope when ya moving it to line up targets , it gets put near the scope when you're lined up and ready to sit.

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nevy
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Re: Catsperch design question new [Re: nevy]
      #5630109 - 01/18/13 03:23 PM

I should also add that I allways have the chair faceing the same way the telescope is pointing and turn my head to look through the eyepiece, I found that haveing the chair at 90 degrees to the scope ( the chair faceing the eyepiece) that A, you need to lean forward to look through the eyepiece and B, when climbing up the chair if not carefull it's to easy to smack your head on the eyepiece on the way up especially when using long eyepieces like ethos.

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Jon Isaacs
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Re: Catsperch design question new [Re: nevy]
      #5630177 - 01/18/13 04:04 PM

Quote:

I should also add that I allways have the chair faceing the same way the telescope is pointing and turn my head to look through the eyepiece, I found that haveing the chair at 90 degrees to the scope ( the chair faceing the eyepiece) that A, you need to lean forward to look through the eyepiece and B, when climbing up the chair if not carefull it's to easy to smack your head on the eyepiece on the way up especially when using long eyepieces like ethos.




I have a fair amount of experience observing seat on astro-chairs. What I found works best for me is for the chair to be at an angle to the chair so I don't turn my head, I just lean forward, place my hands on my knees.

The difficulty with the Catsperch is that if the support is in the front, placing the chair at an angle is difficult because the front crosspiece is so wide it interferes with the base of the scope. For that reason, I mostly use the Starbound and only use the Catsperch if the Starbound has run out of range.

As far as the stability, the question is whether the rear leg is attachment is rigid enough, there is sufficient weight on the rear to maintain stability if the rear leg is rigidly attached. The rear pivot is quite narrow and somewhat sloppy in comparison to the steel chair.

I guess I will just have to try it.

Jon


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Peter Natscher
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Reged: 03/28/06

Loc: Central Coast California
Re: Catsperch design question new [Re: Jon Isaacs]
      #5630280 - 01/18/13 05:22 PM

You don't want to lean to far forward while observing high up with these chairs. I even noticed with my Catsperch chair that if I lean forward a bit towards the eyepiece while higher up, the center of weight shifts dramatically forward over the front stabilization piece and the back leg get less stable. In the case of a rear-mounted stabilization/narrow front leg support chair (i.e., Starbound chair), you might get dangerously out of balance high up on your chair. I'm glad the Catsperch has the stabilization piece forward under my weight and not behind me.

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JayinUT
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Reged: 09/19/08

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Re: Catsperch design question new [Re: Peter Natscher]
      #5630312 - 01/18/13 05:44 PM

I used Shaun's plans to make my chair and I put the brace in front per the plans and because I'm a big guy. On mine I made an adaptation where I use black bolt like things so I can take the front brace off for transport. In thinking through it, I am sure a design could be made to allow the brace to be on the front or back depending on the user. For me, I'm glad mine is up front and I haven't had a problem with the chair at all or using it with my scope. My chair goes up I believe around 44 inches or 46 inches and I have been at max height on it.





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nevy
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Re: Catsperch design question new [Re: JayinUT]
      #5630344 - 01/18/13 06:10 PM

Quote:

I used Shaun's plans to make my chair and I put the brace in front per the plans and because I'm a big guy. On mine I made an adaptation where I use black bolt like things so I can take the front brace off for transport. In thinking through it, I am sure a design could be made to allow the brace to be on the front or back depending on the user. For me, I'm glad mine is up front and I haven't had a problem with the chair at all or using it with my scope. My chair goes up I believe around 44 inches or 46 inches and I have been at max height on it.







You can incorporate a way to hold the foot on the back of the chair also a little slide lid box to store the bolts,
[image]http://[/image]
[image]http://[/image]
You can then transport it easily as one unit
[image]http://[/image]


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Catsperch design question new [Re: Peter Natscher]
      #5630393 - 01/18/13 06:51 PM

Quote:

You don't want to lean to far forward while observing high up with these chairs. I even noticed with my Catsperch chair that if I lean forward a bit towards the eyepiece while higher up, the center of weight shifts dramatically forward over the front stabilization piece and the back leg get less stable. In the case of a rear-mounted stabilization/narrow front leg support chair (i.e., Starbound chair), you might get dangerously out of balance high up on your chair. I'm glad the Catsperch has the stabilization piece forward under my weight and not behind me.




On the other hand.... if the stablization bar were at the rear, the chair could be closer to the scope, and there would not be the need to lean as far forward. As it is, I have not felt any concerns about tipping forward.

My one concern is that the rear leg is wobbly but I guess since I am not hearing from anyone who has tried the rear position, I will just have to do the experiment.

Jon


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cavefrog
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Reged: 11/11/08

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Re: Catsperch design question new [Re: Jon Isaacs]
      #5630922 - 01/19/13 12:54 AM

I was experimenting with mine the other day. (raining, had to do something) I tried sitting on it backwards... it was much easier to get on it that way. I was mostly thinking about using it with a long refractor on a tall mount pointed low in the horizon. not done very often , but it is the reason I bought the chair as it is a bit much for the LB16. This places the wide foot behind you, and gives one a place to lean on.

Theo


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