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Go Back   IceInSpace > Equipment > ATM and DIY Projects

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  #1  
Old 11-07-2018, 03:56 PM
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astronobob (Bob)
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Opinions: Rotating Flex-Dob Shroud 120*

Hi all 'Astro'liano's

I am finding this Flex Tube Dob is quite large - Good 'Light-Bucket'
But the Finder is awkward to reach around zenith - The Base is around 1meter in diameter, if memory serves - 33". Both the Focuser & Finder stand just over 6' when around zenith.
I definitely need a small step to reach them but lunging out another 500mm to get my eye near the Finder is risking a hazard of landing in/on the mirror, haha, or should I admit- I have fell into the scope, well, I managed to straddle around it after gravity failed me, Lol, no damage/consequences - nor embarrassment as I was alone

Some home-made Dobs of this size have had the focuser & Finder attached on or near the bottom of the scope shroud for easier access, makes a lot of sense, and as many know, it a great Idea

So, I am considering Rotating this shroud 120 degrees, as there are 3 trusses placed 120 deg apart'
There is one large bolt on top of each of three trusses holding the shroud to them.

My question is whether this would hamper any collimation factors ?
I would assume all trusses would/should be exactly the same length & all parallel - within reason ?

I guess one can only try it and if ok, great bananas, if not- put it back
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  #2  
Old 11-07-2018, 08:48 PM
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OzEclipse (Joe Cali)
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Bob.

Good point. If you're out observing alone and you have a big fall, knock yourself out. Who will find you? I have similar issues observing up a ladder on a remote site. I exercise extreme caution and minimise the straight up observing when alone. It's worth a try and no harm no foul.

If it doesn't work, you could try : -

1. You can add another finder on the other side if that side is more accessible? You'll also need to add counterweight.

2. Mount a RACI finder down on the rocker box. No counterweight required.

3. Video finder?

4. Add a Nexus or an Argo Navis ? You won't need a finder.

Joe
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  #3  
Old 11-07-2018, 09:11 PM
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astronobob (Bob)
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Quote:
Originally Posted by OzEclipse View Post
Bob.

Good point. If you're out observing alone and you have a big fall, knock yourself out. Who will find you?
Joe, and I'd get a real good look at my clumsy self

Quote:
Originally Posted by OzEclipse View Post

1. You can add another finder on the other side if that side is more accessible? You'll also need to add counterweight.
Great Idea Wont need to bend upside down for them low'ish targets, two finders, best of both worlds


Quote:
Originally Posted by OzEclipse View Post

4. Add a Nexus or an Argo Navis ? You won't need a finder.

Joe
It does have the Synscan GoTo, but it aint accurate enough when using barlows and high power Ep's, let lone a small chip planet cam I intend to use,,, when they find me, or I somehow get out, might leave a rope in here for next time, just incase

Much appreciated Joe
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Old 16-07-2018, 06:58 PM
geolindon (Lindon)
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g day Bob,

i have a similar problem and am thinking a right angle finder . . . . wotcha reckon?

L
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Old 18-07-2018, 11:44 PM
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g day Bob,

i have a similar problem and am thinking a right angle finder . . . . wotcha reckon?

L
Hi Lindon, good thought & should work better than a straight line finder, atleast this would bring the ep and inch or two closer
On the other hand, in my case, I am only a short *ss compared to this light-bucket, and I have just picked up another finder so can add it to the lower side, hehe, saves the step/stool & the risk of falling in, well, for me anyway
Let me know how you go, btw, what aperture is yours ?
All the best ...
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Old 20-07-2018, 07:20 AM
Baza (Barry)
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I don't have the height problem with a 12" but have had neck injuries that make a 90 degree finder necessary. You can't move the focuser but can rotate the top by 120 if you want.
have you looked at moving the finder bracket to the lowest possible point or considered attaching a right angle bracket under the big black nut to mount the finder.
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Old 20-07-2018, 06:31 PM
geolindon (Lindon)
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g day Bob,

the 16" is my grab n go; it sets/packs up in 4 unhurried minutes and for my 185cm is soooo convenient as zenith is at my eye height standing on the ground.

the 18" is where i, with a heights phobia, struggle cos at zenith the eyepiece is 220cm and i'm 2 steps up a ladder and stepping one foot across onto a milk crate to look into my straight thru finder. plus up n down to shift the ladder when turning in "dob's hole" and it comes up against the ladder when aligning. oh those views tho . . . they are worth it

i like your idea of a lower finder; get aligned then up the ladder and viewing with a right angle finder up there also. BUT my 8 strut system = unaligned struts so need another bracket/platform to mount it.

regards, L
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  #8  
Old 20-07-2018, 10:18 PM
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astronobob (Bob)
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Quote:
Originally Posted by Baza View Post
I don't have the height problem with a 12" but have had neck injuries that make a 90 degree finder necessary. You can't move the focuser but can rotate the top by 120 if you want.
have you looked at moving the finder bracket to the lowest possible point or considered attaching a right angle bracket under the big black nut to mount the finder.
Quote:
Originally Posted by geolindon View Post
g day Bob,

the 16" is my grab n go; it sets/packs up in 4 unhurried minutes and for my 185cm is soooo convenient as zenith is at my eye height standing on the ground.

the 18" is where i, with a heights phobia, struggle cos at zenith the eyepiece is 220cm and i'm 2 steps up a ladder and stepping one foot across onto a milk crate to look into my straight thru finder. plus up n down to shift the ladder when turning in "dob's hole" and it comes up against the ladder when aligning. oh those views tho . . . they are worth it

i like your idea of a lower finder; get aligned then up the ladder and viewing with a right angle finder up there also. BUT my 8 strut system = unaligned struts so need another bracket/platform to mount it.

regards, L
Appreciate your interesting inputs, Barry & Lindon
I have two finders now, the original on top which is quite comfortable to use at lower altitudes below 45degs, and am placing the 2nd on the low side for using above 45deg alt's

Was squizzing at Planets last night, and have a marked position for the 2nd finder now, I reckon it will earn its keep no probs !
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Quote:
Originally Posted by geolindon View Post
BUT my 8 strut system = unaligned struts so need another bracket/platform to mount it.

regards, L
Interesting situation Lindon - If your handy with a drill & an angle-grinder, you could fashion some thin 1mm Galvanised sheet up to bridge two struts ?
If you need/like any further info, throw a PM my way - I already have a plan , ,
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