Gord
professor emeritus
Reged: 01/06/04
Posts: 694
Loc: Toronto, ON, Canada
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Hi All,
I've been doing some planning and I'm trying to figure out gear and housing sizes. I like the size of the ED for fitting in my backyard, but I'm trying to figure out if it will work for the gear I want.
I have a 10" newt now, but am considering something larger. Also, I really like GEM's, so whatever OTA path I go, it will be riding on one.
So, will my 10" fit?
How about a 12" (~f5, like the current asian 12's)?
Anything larger?
The problem I see is the length of the tube and being able to swing clear inside the dome, and also how much space the observer has to get to the EP. I don't want to be forced right up against the dome to observe either. Anyone here using a newt?
Thanks!
-Gord
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* Celestron C10/Normand Fullum primary
* Tasco 11TR/Normand Fullum primary
* Orion StarBlast
* Orion Apex 102
* SkyWatcher 80ED
* Celestron CG5a mount
* MallinCam Pro & Color II
* Lots of other astro toys
...and the best wife I could ever dream of for letting it all happen! 
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SometimesKen
professor emeritus
Reged: 07/15/05
Posts: 506
Loc: Bad Moon Observatory
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Hello Gord,
here's a pic of a Orion 254mm X 1200mm newt. in my ED. I had it in my obs. for a few months last year, but I like refractors more and switched back to my 5"er.
Anywayz ... the 1200 mm length didn't crowd the obs too much, but getting to the eyepiece in a comfortable position was challenging sometimes. (at least for me  ) I should also note there's room for improvement to my pier height to set up properly to handle a large reflector.
Here the BMO with the current set up, a ED80 riding a 127ED on a Atlas mount, with a guide scope project I've been working on. The focal length of the 127ED is around 1140 (or is it 1143) and leaves plenty of room for a bigger 'fractor.
Good Luck with your obs.
Ken
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As the setting sun / melts below the horizon / the stars applaud her bow. ~W. Terrance~
Bad Moon Observatory - February 1, 2007
39° 54' N - 74° 09' W
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Bill F
sage
Reged: 05/30/05
Posts: 203
Loc: scotland
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Hello,
I have a 10 inch newt on a GEM in my 7 foot dome. It just fits and my head is close to the dome in certain viewing positions with my binos and Pan 24. in use. The extra foot in an ED would make a huge difference, but I couldn't get one when I was buying my dome. I would think a 12 inch newt in an ED would be fine, as long as it isn't more than about F5. You can mess about with balance weights to pull the end of the tube back a bit if things are tight.
The dome is the best piece of kit I bought. At least doubled my observing time.
Bill
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Orion Optics (UK) SPX 250 F4.8
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Gord
professor emeritus
Reged: 01/06/04
Posts: 694
Loc: Toronto, ON, Canada
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Thanks guys!
So it looks like my 10" won't be a problem at all in the ED (that's a great picture to give a perspective Ken). I assume too that being able to rotate the tube would also help position the EP to give more observer room for certain sky positions?
Bill, in what part of the sky do you find it the worst for EP position relative to the dome?
I too was thinking about balancing the tube in such a way that the mid-point is as close to the center of the dome as possible. With a 12" f5 (tube being about 60" long), that would leave 18" of so at either end, although I would imagine that this would vary depending on where it's pointed.
In the beginning, I'm thinking of something like the CGEM. But what I really want is something like the new CGE Pro (in terms of capability). I'd also like an OTA that gives me capabilities of at least what a C14 would do (visually that is). A 12-ish inch newt should be comparable in terms of going deep, and will give crisper images. It's just making sure that the usability inside a dome this size is acceptable.
If it works for visual, then space wise it should be no issue at all for imaging. And I suppose if I stick around that 1500mm fl size, then even a larger primary could work (just at a shorter ratio). An even better imaging setup.
Thanks again for the input,
-Gord
--------------------
* Celestron C10/Normand Fullum primary
* Tasco 11TR/Normand Fullum primary
* Orion StarBlast
* Orion Apex 102
* SkyWatcher 80ED
* Celestron CG5a mount
* MallinCam Pro & Color II
* Lots of other astro toys
...and the best wife I could ever dream of for letting it all happen!
--------------------
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Bill F
sage
Reged: 05/30/05
Posts: 203
Loc: scotland
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The most awkward position is when observing at high angles. I don't have moveable rings on my scope, so a lot of the problem is due to the usual gymnastics newtonians require to get at the eyepiece. Also my dome came in 4 pieces and has two inch flanges on the inside to bolt the sections together. These cause an occaisional problem, but that doesn't apply to the ED.
Bill
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Orion Optics (UK) SPX 250 F4.8
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rodney
Vendor - Explora Dome
Reged: 03/08/05
Posts: 812
Loc: Asbury, NJ
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Gord,
I feel Ken answered it best. His 10 inch OTA would not be any problem in an Explora Dome. As would go just about any size newtonian OTA. However, it would more so depend on the F-ratio of that scope. A 12 inch F/8 would be difficult to work with, however a 12 inch F/4 would be fantastic, it all depends on the focal length. I use an 8 inch F/5 in my Explora Dome with no clearance issues at all. And as already noted, the bigger concern is your eyepiece location while viewing on a GEM. Parallax rings would be the solution to EP location. I have heard of a guy in Texas (I think) with an older Meade 16 Starfinder F/4.5 and at a 72 inch focal length they had no problems with it. To me that would seem rather tight allowing only about 18 or so inches clearance all around. However, in the article the person was imaging and rarely in the observatory. So in a practical sense it was a mute point to him/her. As long as thte OTA clears everything inside and can see out the shutter I see no reason it would not work. In further reading, the old Coulter 17 inch scopes had focal length of 78 3/4 inches at F4.5 so in essence it would also fit. I would love to try that scenario out.
Hope that helps some, there might be more information on the Explora Dome Yahoo group.
Clear skies,
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Explora Dome information can be found here:
www.exploradome.us
Rodney
Meade 10 SCT
AT 8/F4 imaging scope
13 Truss
C8-NGT
Orion 80mm/F11
Canon 300D
Canon XSi
Two AS-GT mounts
Extremely happy Explora Dome home observatory owner
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Peter G
journeyman
Reged: 01/01/09
Posts: 9
Loc: Orrington, ME
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I thought I'd add some data for the ED 8' round building:
With a dew shield on the front of the MN76, the overall length of the OTA is 51 inches (1295 mm). With the OTA pointed at the bottom of the slot, there is 13 inches (330 mm) clearance between the dew shield and the dome, and 20 inches (508 mm) between the rear of the OTA and the wall.
With the scope pointed at the zenith, there is 26 inches (660 mm) between the end of the dew shield and the top of the dome.
The rotating rings are a big plus in the dome.
Good luck with your project,
Peter
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Gord
professor emeritus
Reged: 01/06/04
Posts: 694
Loc: Toronto, ON, Canada
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Excellent feedback (and pictures) everyone. It's sounding like a 1500mm fl (60" tube) might work ok.
Peter, how far below the dome (rotating) ring is RA axis center when horizontal (like in your picture? I assume that getting it closer to the ring level lets you view closer to the horizon at the expense of being closer to the dome top (and overall EP height)?
Thanks,
-Gord
--------------------
* Celestron C10/Normand Fullum primary
* Tasco 11TR/Normand Fullum primary
* Orion StarBlast
* Orion Apex 102
* SkyWatcher 80ED
* Celestron CG5a mount
* MallinCam Pro & Color II
* Lots of other astro toys
...and the best wife I could ever dream of for letting it all happen!
--------------------
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Peter G
journeyman
Reged: 01/01/09
Posts: 9
Loc: Orrington, ME
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Gord,
RA axis center is eight inches below the height of the wall ring and 15 3/4 inches below the bottom edge of the slot.
The top of the ring - i.e. the top of the base structure - is 56 inches from the floor. The bottom of the dome's slot is 63 3/4 inches from the floor.
From the floor to the top of the silver polar finder cap is 48 inches.
When the scope and mount are pointed at the pole the tension knob that secures the saddle plate is 51 1/2 inches from the floor.
The highest point that the eyepiece can reach from the floor (as currently balanced) is 64 inches - slightly below the height of my eyes when standing.
The dome is high enough that I'd have no concerns with having enough overhead space with a longer OTA or a higher mount. As it is there is over 26 inches from the end of the dew shield to the inside of the dome when the scope is pointed at the zenith.
Overall eyepiece height would be my primary concern with a higher mount or longer OTA, but rotating rings makes eyepiece height and location somewhat easier.
In my case I could have shortened the walls or raised the mount a bit to get better views of the southern horizon, but there are trees there. Modifying the stock structure to gain a few degrees of sky above the trees didn't seem worth it.
I used the adjustable legs of the Losmandy tripod, measurements from the ED web site, and my office in the barn to model the effects of pier height before purchasing the Le Sueur pier. I then used this experience to determine the height of the 18 inch concrete form and J-bolts.
The ED round building was a fun and stress-free project thanks to the information available online and the pre-planning I did.
Good luck with your project. I'm thinking of a 32 cm f4.8 Newt to use in place of the Mak-Newt on occasion.
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Gord
professor emeritus
Reged: 01/06/04
Posts: 694
Loc: Toronto, ON, Canada
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Peter, Thanks so much for the very detailed information about your setup. Love the "snow dome" scene in your avatar BTW.
Sounds like your setup is for most comfort while standing. I keep going back and forth on which way I want to go. Standing is very comfortable, especially for the cold weather. At the same time, I find I seem to be able to study things more intensely while sitting. One of those extended observers chairs would likely do the trick, but I'm not sure if space would allow for it in a dome (with pier, etc.).
It would also allow me to go a bit farther down to the south, but that isn't a great sky for me as well. Houses, street lights, and (likely) new trees to be added to my neighbours back yard.
Thanks again for your input.
-Gord
--------------------
* Celestron C10/Normand Fullum primary
* Tasco 11TR/Normand Fullum primary
* Orion StarBlast
* Orion Apex 102
* SkyWatcher 80ED
* Celestron CG5a mount
* MallinCam Pro & Color II
* Lots of other astro toys
...and the best wife I could ever dream of for letting it all happen!
--------------------
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Bill F
sage
Reged: 05/30/05
Posts: 203
Loc: scotland
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I do nearly all my observing sitting. Without rotating rings my eyepiece is frequently well above my eye height (I'm 5' 10"). I made myself a copy of Carol's observing chair. Not to anything like the same standard of workmanship! But it works. I have to use a 3 step stool to get on the chair at max elevation, which allows me to sit with the eyepiece over 6 feet off the ground. I haven't fallen off. Yet. The chair is very clumsily built but there is still room to move arround with my kit in and that is with a 7 foot dome.
Bill
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Orion Optics (UK) SPX 250 F4.8
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Gord
professor emeritus
Reged: 01/06/04
Posts: 694
Loc: Toronto, ON, Canada
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Bill, that's quite a high perch you've got there! I wouldn't want to fall off there, especially with all the hard, but sensitive stuff around.  Nice looking setup though.
-Gord
--------------------
* Celestron C10/Normand Fullum primary
* Tasco 11TR/Normand Fullum primary
* Orion StarBlast
* Orion Apex 102
* SkyWatcher 80ED
* Celestron CG5a mount
* MallinCam Pro & Color II
* Lots of other astro toys
...and the best wife I could ever dream of for letting it all happen!
--------------------
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Bill F
sage
Reged: 05/30/05
Posts: 203
Loc: scotland
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Oddly enough, this is where having a tight dome helps. Most of the time I can lean against the dome to give added stability when on my high perch.
Bill
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Orion Optics (UK) SPX 250 F4.8
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SometimesKen
professor emeritus
Reged: 07/15/05
Posts: 506
Loc: Bad Moon Observatory
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Hi Bill,
Nice lookin' set up! That certainly is a "cats perch chair"!!
I failed to include in my pic the 3 step ladder used with my 10"er. Rotating rings would have been helpful, but Parallax rings weighed too much for the mount. Wilcox rings are a must with a EQ6 and large reflector.
Good Luck
Ken
--------------------
As the setting sun / melts below the horizon / the stars applaud her bow. ~W. Terrance~
Bad Moon Observatory - February 1, 2007
39° 54' N - 74° 09' W
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