To Dome or To Roll?

[PhotoGav]

My research is going very well and I am ever closer to starting work on 'The River Park Observatory', however I am at a fork in the road and would like to canvas opinion before I go down the wrong route. Which is better - a dome or a roll off roof? Now, I know that there is probably no easy answer to that question as both have their advantages and disadvantages, so what I am really after is a quick reality check on the two options... As I see it, for my relatively small garden, the pros and cons are roughly as follows:

Dome, pros: takes up less garden space, looks better (good with the rest of The Board - wife and two children), more protection from wind, will last better as isn't wood.

Dome, cons: expensive, smaller view of the night sky when sitting in the dome looking up waiting for kit to do its stuff, complicated to coordinate dome rotation with mount rotation.

ROR, pros: cheaper, better view of whole sky, more space for kit storage, easy to use.

ROR, cons: takes up twice the garden space with roll off supports, looks like an 'ugly shed' (words of the Director of The Board) from the outside, is made of wood so will perish eventually.

Are there any other major pros or cons for either route that anyone would like to add given their experience?

Right now I am more inclined to go for a dome, but want to be sure that it is the best option given the expense. What I want out of an observatory is somewhere to leave all my astro kit ready for action, or stored, that is safe and secure, easy to get up and running and also shut down when cloud / rain arrives unanounced. I am an imager, so ease of use for imaging is essential.

I look forward to hearing what people have to say.

 

[Tinker1947]

I have a roll off and while the sky view are nice the breeze sometime limits the use  of my Reflector so a Dome would win when its windy, by how much well the last 2 - 3 months have had some really nice clear sky's but with a breeze as well so i haven't done any thing, if i had had a Dome maybe 3 weeks with the slit away from the wind thats 21 days or more the roll off has cost me. For ma a Dome would be the way to go.

[MartinB]

I have had a 2.7 pulsar dome for several years.  I do miss looking up at the sky on the other hand a major plus is the lack dew and the warmer working conditions ( your body isn't continually radiating heat to the sky).  A down side is that the small aperture of the dome can, potentially set up turbulent air currents, I have attempted to get round this by having a large extractor fan which, in theory, draws air through the dome in a smooth, regulated way.  In reality the seeing hasn't been any more of an issue than when I set up outside.

Co-ordination of the dome is an issue if you want to leave everything running for more than an hour or two unattended.  My dome has a battery driven motor which, with a lot of fiddling, can be set to sidereal which is ok for targets close to the celestial equator but not much cop for high dec ones.  I have all the kit necessary to set up proper dome tracking and have had a lot of advice from Steve 1962 but haven't got round to properly starting the project yet.

Cutting out the wind is a big plus. I have imaged in near gale force winds, terrible seeing but fabulous transparency, great for short focal length.

Pulsar now do a properly driven dome but you need deep pockets

[PhotoGav]

Interesting responses Tinker & Martin, thank you. The dome certainly seems to be in the lead at the moment. It is the Pulsar 2.2m that I am looking at, with as much automation as my pockets will allow!

[MartinB]

One other point, there can sometimes be issues with larger aperture SCT type scopes especially when imaging around the meridian.  When the scope is well away from the centre of the mount the aperture of the dome is presented at an angle to the scope and it can become impossible to get an unobstructed view.  

[Davey-T]

Hi Gav, I have a plastic ROR obs'y which gets rid of the wood problem, had it for several years (can't remember how long) maintenance free, just a power wash every spring.
I have wind / light shields that hook on the top edges, not as sheltered as a dome though.
Domes tend to have low doorways, OK if your young, and nowhere for a warm room so you need to have remote access, I don't think it's a good idea to be anywhere near the mount when imaging no matter how many tons of concrete its buried in

Dave

[PhotoGav]

Interesting point Martin. The advertised max size is a 14" scope, my current max is 8", so shouldn't be a problem for a bit, but is definitely a consideration.

Thank you Dave - is that a home brew or shop bought obsy? Do you have any pics please? Yes, the doorway is slightly elfen on the dome, but thankfully I'm young (well, 46!) and not very tall!

[Davey-T]

8 minutes ago, PhotoGav said:

Thank you Dave - is that a home brew or shop bought obsy? Do you have any pics please? Yes, the doorway is slightly elfen on the dome, but thankfully I'm young (well, 46!) and not very tall!

Yes, all my own work  
Only six by six but fits the SCT perfectly, bigger sheds are available, would like another one next to it for a warm room but was turned down by the planning officer who thinks a garden lounger is better use of the space
Made a pier with electric ram to raise the scope as the sides are a bit high.

Dave

[Grotemobile]

Hi Dave. Very nice. This is my heath robinson job. 

Bit rubbish compared to yours. The view I have got is East.

What U call, a on going project.

 

Steve.,

 

 

 

[MartinB]

1 hour ago, PhotoGav said:

Interesting point Martin. The advertised max size is a 14" scope, my current max is 8", so shouldn't be a problem for a bit, but is definitely a consideration.

Thank you Dave - is that a home brew or shop bought obsy? Do you have any pics please? Yes, the doorway is slightly elfen on the dome, but thankfully I'm young (well, 46!) and not very tall!

Hmm, ask them to put in writing that you will achieve an unobstructed view at low declinations at the meridian with an 8" SCT on a GEM.  Is it a Pulsar you are looking at?

[PhotoGav]

Love that Dave, impressive! Interesting to see that 6'x6' gives just about enough space, that's the size shed I was looking at.

Steve, that's better than my current obsy...

 

The proposed site for the new obsy is behind the conifer on the right, tucked in between the trampoline and the conifer. A fair bit of clearance work to do first!

[PhotoGav]

1 minute ago, MartinB said:

Hmm, ask them to put in writing that you will achieve an unobstructed view at low declinations at the meridian with an 8" SCT on a GEM.  Is it a Pulsar you are looking at?

Ah, ok. Yes, it's a Pulsar.

[MartinB]

Nice dog!

[PhotoGav]

25 minutes ago, MartinB said:

Nice dog!

Thank you, that's Bruff, my useless security system, though he might annoy a burgler by licking them a lot!

[ollypenrice]

For beating LP and wind, a dome. Quite a business getting them to work properly pre-and post flip, though, and near the zenith. 

For seeing the sky and saving a lot of money, a roll off.

It doesn't have to be 'an ugly shed.' A while back Simon (Singlin) showed us a stunning full roll off using the excellent principle of a flat plywood base running on rails and with a slot cut into it to pass round the pier. (I've built two full roll offs and didn't think of this. I welded up my own chassis longhand. Doh!) On this base he put a very swish chalet style buiding too nice looking to be called a shed. Once rolled off it becomes your warm room. Nor does it have to be timber, using this technique. You could use an ugly plastic or metal shed instead!

The full 'sentry box' roll-off is the smallest possible structure because it needs to cover only the scope and not the astronomer, whom it can cover once rolled off.

Olly

[steppenwolf]

Quote

Pulsar now do a properly driven dome but you need deep pockets

Everything about AP seems to require deep pockets! Interestingly, I note that Pulsar have recently released a newer control system which is quite a bit cheaper than the system that I installed last year and it looks even swisher! I guess that's progress for you ............

 

Quote

Hmm, ask them to put in writing that you will achieve an unobstructed view at low declinations at the meridian with an 8" SCT on a GEM.  Is it a Pulsar you are looking at?

It would certainly be worth drawing up a scale diagram to see just what would happen at the worse case positioning. My original Pulsar dome had an aperture 100mm narrower than my new one and with an EQ6 and 10" Newtonian, I didn't ever have a problem although it was VERY tight with a guide scope - OAG would be the way to go to avoid some angst with pointing through the aperture although that extra 4" on the new one is handy!

[PhotoGav]

Thank you Olly & Steve.

Ah yes, the roll off sentry box is an option I had forgotten about. The problem is that I'm not really the best diy-er, so need as much to be purchased ready for installation, preferably by the supplier, as possible!

Good to hear of Pulsar's progress, in fact I sent them an email today asking for clarification on the drive systems. I can't work out exactly what is required to do what! Regarding the slit alignment issues, thankfully I use an OAG already, so that helps as does the larger slit in the latest domes.

Much food for thought and as predicted, the answer isn't obvious one way or another. Though I just showed The Chairman (well, woman!) of The Board a picture of a green 2.2m dome and she thought it looked pretty!

[steppenwolf]

Quote

I can't work out exactly what is required to do what!

If you only require azimuth movement - i.e. you only need some automation of the rotation then you only need to purchase the rotation unit. Apparently, this can be programmed at various speeds to rotate the dome for you so, you slew the telescope to your chosen object, move the dome to get the aperture in the right place using the new control panel and then set it running at sidereal rate (or any other rate you prefer) so that the aperture remains pretty much in the correct place while you image. You only need the aperture controller and motor if you want automated shutter opening and closing.

Quote

Regarding the slit alignment issues, thankfully I use an OAG already, so that helps as does the larger slit in the latest domes.

In that case, I really can't see that the 8" SCT would present any problem.

Quote

Though I just showed The Chairman (well, woman!) of The Board a picture of a green 2.2m dome and she thought it looked pretty!

Now, I have met your lovely other half and can't believe that she prefers a green observatory to white - I was sure that she would have much better taste than that! An observatory should be white, a coal shed, wood store or bike shed could be green to disguise it!

[nucdoc]

5 hours ago, PhotoGav said:

My research is going very well and I am ever closer to starting work on 'The River Park Observatory', however I am at a fork in the road and would like to canvas opinion before I go down the wrong route. Which is better - a dome or a roll off roof? Now, I know that there is probably no easy answer to that question as both have their advantages and disadvantages, so what I am really after is a quick reality check on the two options... As I see it, for my relatively small garden, the pros and cons are roughly as follows:

Dome, pros: takes up less garden space, looks better (good with the rest of The Board - wife and two children), more protection from wind, will last better as isn't wood.

Dome, cons: expensive, smaller view of the night sky when sitting in the dome looking up waiting for kit to do its stuff, complicated to coordinate dome rotation with mount rotation.

ROR, pros: cheaper, better view of whole sky, more space for kit storage, easy to use.

ROR, cons: takes up twice the garden space with roll off supports, looks like an 'ugly shed' (words of the Director of The Board) from the outside, is made of wood so will perish eventually.

Are there any other major pros or cons for either route that anyone would like to add given their experience?

Right now I am more inclined to go for a dome, but want to be sure that it is the best option given the expense. What I want out of an observatory is somewhere to leave all my astro kit ready for action, or stored, that is safe and secure, easy to get up and running and also shut down when cloud / rain arrives unanounced. I am an imager, so ease of use for imaging is essential.

I look forward to hearing what people have to say.

 

You can always be creative in your design to get around the 'ugly shed' concerns of the Director of the Board, worked for me.....

 

 

[PhotoGav]

Nucdoc - excellent work!

Steve - there are three motorisation units offered when you go through the Pulsar options screens to define your order; a dome motor, a shutter motor and a remote dome kit. Do you need all three to computerise the obsy? I hope not! As for colour and the taste of Mrs. James, I'm not raising issues with any of her thoughts on the matter. If I can get away with occupying a patch of the garden with an observatory I don't mind what colour it is, even pink with blue spots, if that's what she demands!!  Regarding the scope alignment to the aperture, I'm pretty certain the 8" wouldn't present any problems, it's future proofing that concerns me most.

[martin_h]

Do you want/need a "warm room" I have a ROR shed roughly 12 ft x 6 ft, split in half, scope in one half, computer and bits in other half. The scope roof slides over the warm roof, so the footprint remains the same.

 

 

[steppenwolf]

Quote

Steve - there are three motorisation units offered when you go through the Pulsar options screens to define your order; a dome motor, a shutter motor and a remote dome kit.

I can only find two units and these are all you need.

Can you post the URLs of the drives you are looking at?

[PhotoGav]

Martin, I had thought not, but I love your video, that's just completely Thunderbirds, love it!

[PhotoGav]

1 minute ago, steppenwolf said:

I can only find two units and these are all you need.

Can you post the URLs of the drives you are looking at?

Ah, now this is good news! Yes, the website only shows the two drive units: http://pulsarobservatories.com/products.php?category=drive However, when you click the 'Customise and Order Now' button on this page: http://pulsarobservatories.com/products.php?category=observatories you enter various details and are then taken through various 'would you like to add this' screens, including those two motors and then one for the 'remote dome' kit. Thankfully it looks as though only those two motors are required to computer control rotation and shutter. At last, a less expensive result!

[steppenwolf]

How strange, it looks as though they haven't updated the order system to take into consideration the new drive units (from the photos, both azimuth and aperture drive systems are different from mine).

I guess you could contact them directly and ask them to put together a quotation for you tailored for exactly what you require?