31 replies to this topic

[Rdug1]

We have been recently ben gifted a beautiful restored Thomas Cook 8" 1858 Telescope 11.5 feet long.  Need to know what size observatory should house it? We are a non profit  and trying to plan on what it would take to get and observatory build.  12', 14' or 16' any thought would be helpful. Will plan on using it as  educational programs. Looking for help on final installation/ sighting/ general info. I ne novice to this site and honored to start to work on this classic scope.

We are located in Vermont. This is an image of the Fry Telescope in a London University. The scope is in 7 very heavy Crates!

[ccwemyss]

What kind of observatory would you want to build? Dome? Roll off roof? Hinged roof? The size depends on the design, and also how many people you expect to be in the space at once.

 

Chip W.

[Rdug1]

Hi Chip, I was imaging a dome which could house up to 6 people.

[ccwemyss]

I have an 8' dome housing a 64" refractor, and it is tight. You can think of that as 16" on each end, but I have it shifted forward to clear the dome by only 8", which should allow 24" behind it. Even so, depending on the position, I still can't stand behind it to look through the eyepiece -- just the nature of the equatorial mount. I was also an operator for the Amherst College 18" Clark for public observing nights. That dome allows 8' behind the eyepiece, and has a motorized platform that lifts observers over 12' up. 

 

You will want the eyepiece to be far enough off the ground to be comfortable for viewing above 45* altitude. With a mount axis height of 9'9", the tailpiece will be about 4'3" below the mount axis at 45* and 5'9" below when at the zenith, that keeps the eyepiece in a range of 5'6" to 4' at those altitudes. For angles below that, you'll want a rolling stair. 

 

For an observatory that will house a 12' telescope and serve visitors, I would thus advise at least 4' of space behind the eyepiece because the stair unit should have enough space for an operator and a visitor to stand on (including a parent and child). They don't all have to stand behind the scope -- the operator can be beside it while visitors look. You want to avoid the situation where the eyepiece is over 7' off the ground, and the operator can't reach it to help the visitor or prevent an accident. Thus, that would argue for a 20' dome at least.

 

As to the height of the stair, near the horizon, the eyepiece will be above 9', but you're unlikely to do much in that part of the sky except for some planet viewing if you have unobstructed views. So the stairs might only provide 24 to 30" of rise to a platform, and then you could have a portable step to bridge the gap for short viewers or closer to the horizon.

 

At that size, the dome doesn't have to be on a wall at the height of the mount. Because it is nearly vertical for several feet at the sides, you could use a wall that's just high enough for the entry door, and that can even be a bit less than full height. So you could have the dome on a wall that's 7' high.

 

It's also good to have some space outside of the circle of the dome, both for equipment storage, and for people to get out of the way while the scope is being moved. Given the weight of the dome, you'll probably want a circular support structure, and the extra space can be in a wing or wings off of that. 

 

Chip W. 

[Rdug1]

HIi Chip,

This is all fantastic info thanks for you time reviewing this. I am having some plans drawn up and I might ask you to look at them at some point.

Do you also know of any similar equatorial 8" in size in our area? With out unpacking and assembling and measuring the actual telescope and the mount hard for  me to know the size of the pedestal. You said with amount axis 9'9" Is that what my Telescope is your is that an approximation? I have not been able to find a plan with measurements of this Scope. Just drawings/photos without sizing. So when we do the concrete pedestal height all of this  must be taken into account? It looks like in the photo I posted of the Fry telescope the pedestal looks like a height of 2.5' if the guy in the photo is not a giant..

Maybe I need to take a trip to London to get a good look at the Fry. Again thanks so much for you input it will really help this project move along.

[ccwemyss]

Mt. Holyoke College has an 8" Clark in a domed observatory.

 

https://www.mtholyok...ery-item-1725-2

 

You might want to arrange a visit with them to see their setup.

 

The 9'9" axis height was a result of a rough estimate I did of where you would want that point of the mount to be, if you want the eyepiece to be a little above 4' off the ground when pointed at the zenith. Looking at the picture, I'd estimate they had it set up with a height between 9' and 10'. I agree that it's hard to tell how high the pedestal is. 

 

Chip W. 

[SkipW]

That's a beautiful telescope! Nice catch!!

The critical dimension for sizing a dome will likely be the distance from the dec axis to the end of the eyepiece when racked all the way out, plus sufficient room from EP to wall to stand on a ladder or stair, plus offset from the intersection of the dec and RA axes to the center of the circular footprint of the dome (this can be reduced or eliminated by offsetting the pedestal so it's south of the center of the dome), plus some extra for the lateral offset of the far edge of the tube from the intersection of the axes.

 

Don't forget the thickness of the supporting wall (if it's a cylinder) or collar (if the dome is atop a square building) since the nominal diameter of the dome will be approximately the size of the outer diameter of the supporting cylinder and this will probably be at least 6" thick, meaning you've already lost at least 1' of dome diameter, and maybe more if there are mechanical doodads like motor drives mounted inside that your equipment must always clear in order to avoid operational problems. Depending on the details, I suspect you're looking at an 18' dome at least.

 

Where in Vermont will it be installed? Can the polar axis of the mount be adjusted to your lower latitude? 

[Rdug1]

Hi , Thanks for jumping in this conversation very helpful information!. It will be installed in Southern Vermont. Originally install at the Fennel Hill Observatory on the Isle of White of the cost of southern England. I am not sure about the polar axis of the mount. but the difference would be 

latitude 50.65047 Longitude -1.293190 Isle of wight
lat 43.147362 longitude -72.721771 West Townshend

[Oregon-raybender]

Chabot Observatory has a 8 inch Clark, f/14

 

But yours is a bit longer, f/17 ?

 

So maybe a 20 to 25 foot dome about 10 feet of clearance. 

 

Here are a few images.

 

Starry Nights

 

https://en.wikipedia..._Science_Center

 

https://www.flickr.c...bold/8687074875

https://chabotspace..../observatories/

[Rdug1]

Here is an image of an engraving of the Telescope from Fernhill Observatory which is where this came from. It says 11.5'

[R Botero]

What a gift - congratulations!   Check this video's end for Jeff Blazey's own observatory and his (donated) 11" f/12 D&G at Camp Troy: https://youtu.be/pTF...m1T-iFmYDXkh_U1    It may give you some ideas for the old Cooke.  Jeff is a member of this forum.

 

Roberto

Edited by R Botero, 23 July 2024 - 06:54 AM.

[R Botero]

I would also suggest subscribing to the Antique Telescope Society if you are not a member yet and joining their online forum:  https://ats-forum.gr...-Forum/messages   A number of members have restored Cooke scopes there.

 

Roberto

[Rdug1]

An image of the restored Cooke clock . Just can wait to unpack the rest.

[R Botero]

Beautiful.  Looks like a great restoration work

[Rdug1]

Restoration was done by David Hudson of England. Who has passed and did an amazing job. Did you know him?

[R Botero]

Restoration was done by David Hudson of England. Who has passed and did an amazing job. Did you know him?

No, I'm afraid I didn't but I've only visited the Isle of Wight twice (and sailed around it once also) and was not aware this telescope was there.  Looking forward to more pictures as you unpack it!

 

You may also want to look at this restoration closer to home:  https://www.cloudyni...ph-restoration/  Some of the CN users in that thread may still be active.

 

Roberto

[x-ray]

I suggest a 16 foot Ash dome.  You need some elbow room for observers and guests.  The center of the pier does not go in the center of the dome.  The intersection of the RA and declination axes goes in the center.  When the telescope is horizontal, you want to be able to see out through the slit, so that sets the height of the wall the dome sits on.  There are several proportions that need to be integrated into the design.  The support pier under the telescope needs to be separated from the floor that people walk on to avoid vibration.  Dimmable red lights pointing down at waist height makes for safe illumination with no glare.

These are some of the many considerations that will include an observing chair.  I'm helping a group in NY with a new observatory for a 12;5 inch f/15 Warner and Swasey that I am restoring for them.  The architects need a good understanding of the problem.  You have a great start with a fine telescope.  I care for Harvard's 9 inch Clark.  It is in a 16 foot ash dome and gets used a lot.  Ask lots of questions

Alan Sliski

[Rdug1]

Thank you Alan that is very helpful. Would i need to assemble the telescope for accurate measurements before determining the height of side walls and dome dia? 

I prefer to leave it crated until the observatory is finished. Would other 8" thomas cooke telescopes be the exact same size?. I have not been able to find any plans for this scope just engravings. I can get to the cast iron pedestal which is in two parts I could measure that. I have a meeting with a designer/Architect in August to go over the site and building requirements. Is this something you do also? 

[martinr]

Beautiful - and that Clock Drive is in marvelous condition! Mine is in a poor state and plan to work on it in the next couple of years after moving to Utah from Kansas. Mine is all in crates as you know.

[SkipW]

Looking at the engraving and assuming it is close to the true proportions (hey, it's all I have to work with!), I'd guess that the distance from the dec axis is about 6'5" to the eyepiece and almost that much to the front of the dew shield, which looks to be about a foot long. Presuming those lengths are close to right, you would want a dome no smaller than 16'. Depending on the actual dimensions of the telescope and details about the dome and support structure, 16' might be uncomfortably tight.

 

I second the suggestion to contact Ash Manufacturing Co. (info@ashdome.com, 815-436-9403). They offer domes in two-foot diameter increments from 10'6" to 30'6"; you'd probably be interested in their 16'6" R or 18'6" M models. Request diagrams showing dimensions and recommended supporting structures, and the price list. Prices go up rapidly as size increases, and and take a jump between the R models (smaller domes, up to 16.5') and M models (starting with 18.5').

 

I understand not wanting to uncrate the instrument until you're ready to begin installation, but I'm not convinced that is the best plan. You will want to take accurate measurements of the tube geometry and check on things like being able to lower the PA angle by more than 7° and what that does to the height of the mounting point, especially if you go for the smaller dome size, before settling on your observatory plan.

[Rdug1]

I was able to do a drawing after opening up a few of the crates with the stand and the Telescope main tube. Here is what I came up with.

 

 

[SkipW]

Nice sketch!

 

Is the circled assembly between the pedestal and back end of the PA adjustable? Can it be adjusted enough to accommodate the change in latitude?

 

[R Botero]

090F175F-E699-4400-AEB7-42D3688DAB84.jpegI was able to do a drawing after opening up a few of the crates with the stand and the Telescope main tube. Here is what I came up with.

  

[x-ray]

Your sketch is a good start.  I think you can measure what you need to without assembling it, which is a big project that requires space and material handling.  Making a CAD model of it is the best approach.  This will allow you to see how it fits in the dome.  I can help with this if necessary.

Alan

[Rdug1]

Alan, thanks and nice speaking with you at the conference! Will be back in touch soon.