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I am ready to pull the trigger on a G11, however, I must first completely rebuild my observatory. I have a CPC1100 EDGE HD on a wedge, I plan to defork it and put it on a G11. I'm designing the new ROR Observatory and was wondering if anyone had that scope on a G11 or just general insight as to how high the pier should be relative to the walls, how much clearance around the 11" scope with a G11. any other input before I place a shovel in the ground.

Hi aughtago

The pier height really depends on the obs, but for me I went with a 36" pier height. I have a rolloff observatory (temp) so i didn't have to worry about the height relative to the walls, but generally i only image above 30 degrees (abs minimum) and more like 45-55 deg


Brian

aughtago,

How high? An imaging camera doesn't care so much but your back and knees will let you know if you get it wrong. A Celestron EdgeHD11 is not huge but when you consider the possibility that you could? easily have over 12" of imaging hardware sticking out the back of the OTA not counting an external focuser or any cables the shortest pier height is not going to be all that short. If we start with?a Losmandy G11 I at a pier height of 30" from the finished floor to the base of the Losmandy MA mount adapter the mount will be about 35" high. If you are planning to image with the C11 your imaging train will be getting uncomfortably low anywhere near zenith and you probably do not want to be dragging any hardware or cables on the ground which would be a possibility with a sort 30" pier. It seems like a safer imaging pier height from finished floor to the base of the MA is probably about 36" on the short end which puts the mount at a tic over 40" and provides some future flexibility in imaging options.

If you plan to use the EdgeHD11 visually you gain about 10" or so without all that hanging off the back of the OTA. I'd suggest nothing less than 42" depending on how tall you are. At 42" the mount is actually sitting just under 47" or so. Low enough to not need to be on tippy toes for horizon hugging objects if you rotate the diagonal but still high enough to be sort of comfortably seated for observing at the zenith. Slightly taller is a plus as you will not be giving your knees as hard a workout and for taller folks 46"-48" is not out of the question.?

If you add other popular scopes lets say a typical 130-140mm f/7-f/9 refractor you will need to use an even higher pier to observe comfortably at or near the zenith. My favorite visual scopes are the bespoke Parallax/AT130mm f/6 apo and the slightly longer 100mm f/9 Takahashi FC-100DL apo. For visual use with these OTAs I usually have the tripod height set to about 44" or about 48" mount height. Which is also where I used to set the tripod for the C14 with the G11 under it.??

The other things to think about is that visual observers take up a lot of room around a scope. The longer the OTA the more room it and the observer needs around the pier. Taller walls provide much better wind protection and reduces OTA disturbances. If it is cold where you live or you like to not be cold a standalone warm room to operate the scope imaging sessions from will be a plus by all? accounts. isolation of the floor and pier foundations is really important, you cannot walk on the same floor as the pier is poured on! Frost depth is something to know if it snows or freezes at your location. Do not believe the freeze depth charts, by digging 12" deeper your telescope pier will probably still be plumb in 20 years. Build your pier foundation upside down, put the largest width on the bottom and use Sonotube for the main pier base set 6" above ground height, use rebar from the base and up the pier and tie them together. Use quality 12" S.S. L/J-rod anchors in a 1" plywood form to hold the rods accurately in place during concrete cure and take the time to finish the foundation top level and flat to minimize the need for shims when installing the steel pier. If pouring a concrete floor pour it after the pier foundation has cured. Use a perimeter footing to help stabilize the pad and leave a 1/2" gap around the concrete pier and poured floor, once all are cured fill the gap using a soft flexible expansion gap foam.? ? ? ? ?

Just some thoughts.

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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

THANKS SO MUCH CHIP! ?Very informative. exactly the kind of info i needed. I'm amazed the G11 only uses 5" including the MA adapter, but I've only see pictures and videos of it, never had my hands on one. I wish they had a 3D scale drawing on their website of it. I plan to only remote image and remote view from my warm house, but when I poured my last pier I was only planning to do visual, so I know how interests can change. Building it to accommodate either makes sense.

I went 36" deep with the last 36"x 36" block of concrete and an 11" concrete pier, topped with a custom 6" steel adapter and had I no issues that I detected, but was considering 48" deep this time with a 12-14" concrete pier just for overkill.

I don't remember where I found it (so I can't verify the accuracy of it), but this is a SketchUp (.skp) model of the G11 which I used for designing an automated slide-off enclosure for my rig.

THANKS GREG! ?that is perfect as I am designing my ROR in Sketchup.

it looks far better than I could have drawn, and looks real nice sitting on my concrete pier next to my garden wall (for orientation) now just to design a shed around it.?

aughtago,

Here are some pics from inside my roll off shed. I pained over how high to make the pier considering I had 6 foot or 72 inch walls, and a 6 x 8 foot shed. But one of the most important measurements is making sure the RA axis hole, seen here with a Polmaster inserted, points up and over the wall so you can do polar alignment. How high this point is will be affected by your altitude setting for your latitude. In the end the top of my pier with leveling head was 39 inches, but I probably could have gone lower. I must flop the scope to the side and have Dec axis horizontal and scope almost horizontal to get the roof to clear, but I still can park at CWD with the roof closed.

The scope shown here is a C925EdgeHD, which is about the largest SCT I could fit inside a shed this size. With guide scope I am just clearing the walls in some scope orientations. For your 1100, you may want to consider an 8x10 foot shed or larger. I also found that having opposed inside corners at an east-west orientation gives the most room for the scope to slew back and forth and do meridian flips.?

So you would need to do some measurements on how high the top of your scope is off the ground at CWD and when folded over, and then how high the RA axis hole is. The rest is trigonometry. But the bigger the shed, the bigger the roof, and the more weight you need to move when rolling it off. All things in consideration. The shed was built with plans I bought from ShyShed, which saved me much time during the build process and materials planning phases.?

Good luck!

John?


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Losmandy G11G2 on pier; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user

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Thanks Brian.

The pier is a 4" solid aluminum cylinder, and braced with a 2x3" aluminum bar, both bolted through an end section of railroad track. The rail is 6 feet long, sunk 4 feet into the ground and surrounded by concrete. The shed is on a gravel bed and has a floating floor isolated from the pier structure. I would probably never do it this way again, as the rail steel is flame hardened and can't really be cut, drilled or modified with most tools short of an acetylene torch. Also, if you look at a cross section of rail, there are unusual geometric curves that only mate with custom surfaces. But in the end, it turned out super solid and vibration free and will support any weight scope that fits in the allowed space :).

John
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Losmandy G11G2 on pier; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user

YES, the shed in my head is 8' x 10'8" or there about to allow for 16" on centers and 8' long ply wood etc. The height is my main concern. Thanks for the pictures. Due to the layout of my yard, the shed will not be true N-S, rather about 30 degrees NE by 210 degree SW. The mount will be closer to the SW end, I think, but that is still wet paint in my head and may change. I plan to normally have the roof stop when it is about 8' open providing dew protection for a small work area at the NE end. I had not thought about the polar scope, but with my current mount , I cannot aim it at polaris or the camera will collide with the fork mount, so I've gotten pretty good at PHD2 drift aligning. I've also used the new Polar alignment tool in NINA, but if PHD2 drift is the gold standard, why not use that? I only check polar alignment every 6mo to a year anyway.?

?That said, I cut my teeth on a 4" manual GEM with a illuminated polar stop built in, so I am familiar with the process, but have never used it on a goto mount used for Astrophotography. I will have a learning curve for sure when i get the G11. That is why I posted here to get the wisdom from you experienced G11 users. I have also toyed with the idea of trying to get the G11 and set it up in my existing POD before finalizing the design , however, I would be severely limited in where i could slew it in the pod as my pier was put off center for visual observing comfort while using the diagonal on the fork mounted C11. this has been a challenge since i have moved onto AP and remote viewing, hence the new observatory idea was hatched.
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?I am "lucky" in the fact that my yard is surrounded by trees and a mountain to the east, my lowest horizon is SW, so If i can get the scope high enough to see over my trees , possibly with a fold down wall to the SW, and still keep it low enough to close the roof with it in any position, that would be ideal. I am only 5' 8" so that helps in that respect too. With the information you guys have provided combined with a Horizon file that i created using the current scope view using NINA plugin, I should be able to calculate a ideal height for my situation.?

?I would also like to set up a flat panel and have the scope able to slew closely to that, with the dew shield in place, so that may effect my pier distance from the NW wall, or I may opt for one that folds down from the ceiling in just the right spot when the roof is closed.

On Tue, Jul 19, 2022 at 05:17 PM, aughtago wrote:

I've also used the new Polar alignment tool in NINA, but if PHD2 drift is the gold standard, why not use that? I only check polar alignment every 6mo to a year anyway.?

Drift align is the gold standard, but a polar scope or Pole Master gets you most of the way there, and you can fine tune later. There is also the iterative method, using other stars if Polaris and the north are blocked, but fortunately I have never had to do it that way. In the NE USA, we have some hard freezes during the winter, so even a large concrete base can move around a tiny bit. Like a house foundation, the bottom of the concrete should be below the frost line for your area, so ice doesn't lift the whole construction

SharpCap is another preferred tool for PA, which is very accurate without doing drift. NINA's tool I have not used personally so can't comment. But even using a guide scope, you still need to clear the north wall top to a large degree going east or west when rotating RA, to get enough star field rotation. But I think you will find a GEM is much easier to moderate for the calibrations than a fork mount arrangement.

But many a shed design I have seen have a fold down wall to the south, to get at the low targets that don't stay above the horizon as those at higher Dec do. My south has a high tree line so that wasn't a concern for me.

Good luck and please keep us posted :).

John
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Losmandy G11G2 on pier; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user

I did try sharp cap align once didn't have much luck with it, dont remember the issue, maybe my inability to point north with my mount. NINA's new plugin is real easy and gets you real close, review and tweak a couple settings the first time, then just hit run, it slews to your predetermined area of the sky (for me it was SW) takes 3 images x degrees apart, then plate solves them, gives you a visual indication of what direction to move and how much. very quick and very easy to use, no need to see polaris.

I live in NE too. I dont think my 36"x36"x36" block o concrete set 3" below grade to the top, has moved yet, but it's only been through 2 winters I think.

aughtago,

Not sure I know what you mean but the Losmandy MA is about 4.5" tall from the base to the top of the MA so it doesn't add much height.?

When I was describing the pier foundation advice I did not include the foundation diameter. I had an engineer look at what is needed for a mount that could carry 100 pound payload, the EQ mount and the counterweights needed for that 100 pound payload. I used 300 pounds on top of the pier and said it needs to be bombproof up to 48" tall using a steel pier with a welded round steel base resting directly on the concrete pier not elevated on the j-bolt anchors, this is important to minimize vibration. Therefore, I wanted the pier foundation top to be well finished flat and level. This pier foundation can support a pier up to 14" diameter and mount up to an AP1600 fully loaded and last at least 20 years.? ?

The engineer thought a metric ton of concrete with plenty of rebar 4' deep would do the trick. So what he came up with was a 36" diameter 48" deep hole filled with a 36"x12" cylinder of concrete with another 18"x42' cylinder of concrete on top finishing 6" above grade. This is basically about a metric ton of concrete and overkill for my 300 pound top of the pier requirement. You could also reduce the diameter at ground level to the working diameter, 8"-10" but I would not go all the way up as concrete is not so easy to change the height of the pier as using a steel pier in the height of your choice.??

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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?

On Wed, Jul 20, 2022 at 03:33 AM, Chip Louie wrote:

concrete is not so easy to change the height of the pier as using a steel pier in the height of your choice

Agree with this as part of my pier is permanent and can't be changed. If I had to do again, I would have sunk some "L" bolts into a concrete base at ground level in a square pattern. That way you can change or modify your pier as needed, or alter type and height as needs progress. But the bolt spacing has to match your pier or an adapter plate that fits to a pier.
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Losmandy G11G2 on pier; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user

Yes, that was my suggestion. By casting in 6-8 pieces of 12" long, 1/2" thread J-bolts you are always going to need to use the same diameter base plate. But it is important to use the larger diameter for maximum contact and support of the steel base with the concrete foundation. You will just use the large base plate and weld a pipe and support plates/fillets to the flat steel base you want to use, this way as you change it up over time the pier can be made to the right diameter and height as appropriate for the mount and likely scopes used. Alternatively you could cast in recessed threaded inserts for different diameter base plates an just run in socket headed cap bolts as plugs until needed.?

Most mounts like Losmandy offer pier extensions to get the mount height closer to where you need them for easier access or operation on a permanent pier. Obviously you don't need to go so heavy on the concrete for a lighter mount and payload and the depth and diameter really depend on your frost line depth but the rebar is non-negotiable as if the concrete cracks significantly that will be all that is holding the concrete together and we would not want to have the pier crack and drop your mount and optics in the middle of a cold winter night.?


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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?