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3m dome multiple scopes

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#1 RaulTheRat

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Posted 09 June 2019 - 04:00 AM

I'm in the planning stages for an observatory (early days, we've yet to relocate to the place where it'll be and that will most likely be next year).

For the purposes of wind protection and blocking stray light I'm really leaning towards a dome, but have reservations about practicality with the kind of setup I want.

I'm interested to know (ideally pictures would help to get this clear as well) if anyone has several scopes mounted side by side and/or piggyback in a medium sized dome.

I've already decided that the commonly available smaller domes around 2m won't be big enough. I'm thinking that if I can fit multiple scopes in a 3m dome though that it's worth serious consideration.

The mount will most likely be a Mesu with decent capacity, and at the moment scopes would be an 8" mak-newt, 6" refractor and a small refractor as well. I'll most likely add a big Cassegrain (something around a 14" RC) once I've built the observatory, so it'll be quite a bunch of scopes, albeit the longest won't be longer than about a metre.

Although I could obviously switch between OTAs, I'm not overly keen on the idea - a massive part of the benefit of an observatory is being able to set up and image without spending time mounting OTAs, balancing, connecting things etc. If a bunch of scopes mounted together won't be practical in a dome I will more seriously consider a RoR despite my concerns about stray light and wind.

In terms of walking around space, I don't expect to be using it for visual very much, but I do want that to be possible, and need to be able to walk around in reasonable comfort to change camera from OTA to OTA, make other adjustments etc. Most of the time I'll be imaging, and room for a desk etc inside the dome isn't necessary - if I need that, I'll add a bay.

It would also help if people could suggest some software they used to help visualise and design their own domes so I can start getting a model together to try things out.

#2 MCinAZ

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Posted 11 June 2019 - 01:35 PM

  Are you looking to use all of the telescopes simultaneously, or would it be feasible to choose one or a subset to be used at any given time. If you want all of them to be able to see the sky simultaneously, you may need a wider than typical dome shutter. If you're okay with some of the apertures being obscured while others are in use, you will likely need more than one dome azimuth model.

 

  I work with a building with a 10' Home Dome which has a PlaneWave L-500 mount equipped with a CDK500 in the primary saddle and a 12-1/2" R-C on the outside of the arm. Only one telescope can see the sky at once, though this isn't a serious drawback because the goals for the two telescopes are different. Each telescope has its own pointing model as well as a separate set of dome control parameters to align the slit.

 

  As for software, we used PlaneWave's calculation spreadsheet along with in-house generated CAD drawings to make sure everything would fit before we installed the L-500, and a lot of time in the dome since to make the pieces work together.



#3 RaulTheRat

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Posted 12 June 2019 - 06:30 AM

Ah thanks I hadn't thought of that - indeed, there's no requirement for multiple scopes to see the sky at the same time (well, at least not laterally separated ones on a side by side saddle, I'd imagine piggyback would be able to in any case). I would switch from one scope to another depending on what I'm doing, probably a large(ish) Cass on one side for deep sky or planetary imaging, a small refractor for wide field, and a bigger refractor for solar. Occasional visual use could I suppose be through any of them, but in the case of visual use even manual dome control would be fine.

Software would be SGP, which I know can control a dome but I have no idea what the dome software would be or how multiple dome models would work, I guess I need to look into that.

Pointing models won't be an issue unless I win the lottery! I did consider 10u but to be honest any unguided capable mount is probably out of budget, and even if I stretched to a gm2000 it would compromise payload a great deal compared to a Mesu, so although buying anything is still quite some time away I'm far more likely to end up with a mount that needs guiding, and won't have to consider multiple sky models for the various scopes.

#4 mark77

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Posted 12 June 2019 - 10:22 AM

I have a 15 foot dome that I built from scratch and I have 3 scopes mounted on the same GEM platform.

The main scope is a 16 inch Newtonian at F4, then I have 2 different William Optics refractors, one on each side.  All of them have motorized Moonlite focusors.

 

The William Optics scopes are attached with Losmandy D dovetails from ADM.  It is not in this picture but at NEAF this year, I picked up one of the ADM X-Y adjustment stages.  It will allow me to easily and accurately get the scopes all pointed at the exact same point in the sky.  I still need one for the other side but they are a bit expensive, so one at a time.

 

 

 

 

Attached Thumbnails

  • multipleScopes.jpg


#5 RaulTheRat

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Posted 12 June 2019 - 11:47 AM

Thanks for the reply. Looks like a pretty awesome setup, and a rather big DIY project on the dome!

I can't find the ADM XY stages by googling, do you by any chance have a link? I would also probably tolerate having the scopes pointed slightly differently (I could just solve and sync with whichever I'm using) at least for a while, but I'd be interested to see a picture of them and know the price.

How do your Losmandy dovetails attach? Do you have some sort of dovetail plate they all attach to? It's difficult to see in the picture, perhaps you have them directly bolted into the plate under the big newt???

#6 mark77

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Posted 12 June 2019 - 01:32 PM

https://www.admacces...y-duty-version/

 

https://www.admacces...y-duty-version/

 

I have the plates bolted to the side 

 

I will try to take better pictures tomorrow 



#7 RaulTheRat

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Posted 12 June 2019 - 07:00 PM

Thanks. Yes they look very nice - I already have something similar actually, I think mine is from TS and I bought it for using my small refractor as a guidescope but never used it yet, I use an OAG. The ADM is probably better, but mine seems very solid and substantial too and is most likely up to handling a small refractor at least without flexure. Still, worth knowing about the ADM and I suspect in the long term they might prove necessary once I get this thing built.

#8 drprovi57

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Posted 15 June 2019 - 12:00 PM

I have an Ashdome 12.5 ft observatory that houses an AGO 17" iDK (main OTA) - I amounted SW 100 Esprit along with a Lunt LS80THa/DS solar scope.  In addition, I have a Questar 7 Astro mounted on a Paramount large dovetail side-by-side plate - very solid design.  To ensure proper telescope pointing through shutter opening, I have two dome models that I use with the TSX Pro.  Hope this helps.

 

Jason

 

Here are some photos:

 

IMG_0031.jpg

 

IMG_0036.jpg



#9 RaulTheRat

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Posted 15 June 2019 - 01:06 PM

Thanks Jason, very helpful to see some photos and get some ideas how people mount stuff. It's looking more and more likely I'll go with a dome as it seems any issues are reasonably easily solved.

Your dome is quite a bit bigger than what I'm considering (probably the biggest I can afford, or indeed really need anyway is 9ft/3m) - I see you have a 17.5", would you say there's plenty of room around it? I'm considering that the biggest scope I'd expect to put inside would be a 16" RC probably, which my initial guesstimates suggest is a confortable enough fit in a 3m dome, but it would be nice to get some confirmation and ideas based on other similar sized setups.

#10 Carl N

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Posted 15 June 2019 - 03:46 PM

Multiple scopes are easy in a dome. The constraint isnt the dome diameter it's the slit width. Of course, the closer your tolerance on slit width, the more important you have precise offsets and settings done in your control/slaving software. The dome diameter limits scope length. I mounted side by side 115mm refractor with 9.25 SCT in my 6'6" TI home dome. 6'6" limited me to about a 130mm f8 refractor due to length.

#11 PirateMike

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Posted 15 June 2019 - 04:23 PM

Here is a thought that I have not yet seen mentioned here on CN.

 

I don't like domes unless they are on a mountain or big hill high above any light sources like building lights, street lights and the such. If they are on a similar elevation as the light sources, it is inevitable the the sources light will enter through the dome shutter and flood the dome with brightness. Not a good thing considering that one goal of a dome is to keep all light from reaching the scopes optics excepting the light coming directly from the FOV.

 

In such a situation, I prefer roll off roofs or other similar structures. These structures can be designed so that the walls do not permit stray light to be "trapped" inside them and also block all stray light from entering the optic system of the scopes installed. They are also much better at allowing itself and the telescope equipment to reach the outside ambient temperature.

 

I always get a chuckle when I see a picture of an opened roll-off roof observatory in a "direct light" environment with the end of the telescope peeking up over the top. Makes me wonder if the person forgot to add the last foot of wall.

 

Domes can have the same (or at least similar) issue if they are built in a location that does not account for their design limitations.

 

Just my thoughts

 

 

Miguel   8-)

 

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Edited by PirateMike, 15 June 2019 - 09:10 PM.



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