96 replies to this topic

[Ittaku]

The short short version - I have land with no local illumination and an SQM of approximately 21 that I want to set up a very large observatory on with a reasonably large amount to spend for DSO observation. I'm terrified of heights and don't want to climb up for a very large Dob. The Optiques Fullum foldeds look to be the solution I'm looking for. I have soft plans for a slide-off-roof observatory. Yes I'm relatively inexperienced, yes it's a lot of money, yes I'm crazy - please don't debate that as I know this better than anyone.

 

What are people's thoughts on the quality and suitability of the light collector and observatory setup? If anyone has experience with systems of this size of any sort I'd be most grateful for your experience and lessons as well. Thanks!

 

Other information:

The land is a one hour drive away and I plan to go out there just about any clear night, which is why the compromise on a Bortle 4 location.

There is a house on the property that I can go to and from so resources and the potential for a place to sleep are not an issue.

Power would be very difficult to get to the location so I'll have to use standalone power.

Edited by Ittaku, 24 January 2021 - 03:50 PM.

[Allan Wade]

You are looking to spend around $160,000 by the time you have the scope in your hands. Then another $30,000 for a ROR observatory. So I expect you already have a pretty advanced knowledge of what you are undertaking. But some random thoughts.

 

I consider what you want to do a lifestyle choice. With that in mind, it is a very large sum of money to set up under a Bortle 4 sky. My priority would be to find a better observing location at the expense of some aperture if necessary. A 30” under a Bortle 1 is going to perform as well or better than a 40” in Bortle 4.

 

How do you feel about the large secondary mirror used in the folded design, and it’s impact on visual performance? You are spending huge for a 40” scope that doesn’t perform at a 40” level. I see it as a big sacrifice to make in order to avoid a ladder.

 

For that budget, I could build a bigger and better telescope, but it would be a traditional dob design requiring a ladder, though not an overly large one. When you get into it, you realise ladders are a non issue.

[Ittaku]

You are looking to spend around $160,000 by the time you have the scope in your hands. Then another $30,000 for a ROR observatory. So I expect you already have a pretty advanced knowledge of what you are undertaking. But some random thoughts.

 

I consider what you want to do a lifestyle choice. With that in mind, it is a very large sum of money to set up under a Bortle 4 sky. My priority would be to find a better observing location at the expense of some aperture if necessary. A 30” under a Bortle 1 is going to perform as well or better than a 40” in Bortle 4.

 

How do you feel about the large secondary mirror used in the folded design, and it’s impact on visual performance? You are spending huge for a 40” scope that doesn’t perform at a 40” level. I see it as a big sacrifice to make in order to avoid a ladder.

 

For that budget, I could build a bigger and better telescope, but it would be a traditional dob design requiring a ladder, though not an overly large one. When you get into it, you realise ladders are a non issue.

Thanks for your reasoned thoughts. Yes I'm well aware of the cost but, well, it's not an issue for me so just paper over that from here on. As for the Bortle 4 skies, the issue is it's a 1 hour trip to the site and we have the land. To get to Bortle 1 from here takes 3 hours. Bortle 2 is 2 hours. Our city is absolutely enormous as you no doubt know. I can comfortably drive an hour each way for 2 or 3 hours' viewing, but I cannot do a 4 hour+ evening round trip, even though I'm retired, and we are not leaving the city to live further out for family reasons. So this is the compromise I get from my wife that still allows me to build a big scope, but I have to drive there.

 

I'm not entirely sure what to make of the impact of the folded design which is why I'm opening up the discussion. I've seen precious little written about it and we don't have a single one in our country - and thanks to Covid, I can't fly out there to compare. As a builder you obviously know something that I'm unable to find through simply reading online. Feel free to enlighten me, bearing in mind I'm coming from scopes in the teens. Yes I'm crazy, I'll say it again, but I'm not just buying this as a cashed up person looking for decoration; I plan to use it every clear night. Thanks again.

[Allan Wade]

I understand, if you plan to drive out there to observe and back again, then distance becomes a factor. My site is a three hour drive away, but I’ve been known to spend two weeks there observing. What I’ll say is, I’ve spent a lot of time, effort and money over the years developing my astro property into what it is today, and I would be very disappointed if I had done all that under anything less than Bortle 1 conditions.

 

I spent a fair bit of time at the big overseas star parties using big scopes before I got mine. That was very enlightening and I made some life long friends along the way. It’s tough we can’t do that right now. 
 

All scopes have compromises. A big traditional dob needs a ladder, and that’s a compromise to some people. The folded Newtonian design is compromised optically compared to a standard Newtonian design. That’s where it’s good to try lots of scopes and see how they fit your style.

[eyeoftexas]

I can comfortably drive an hour each way for 2 or 3 hours' viewing, but I cannot do a 4 hour+ evening round trip, even though I'm retired, and we are not leaving the city to live further out for family reasons. So this is the compromise I get from my wife that still allows me to build a big scope, but I have to drive there.

 

I understand the compromise you're making, in that you already have the land.  Regardless of distance, make sure that your ROR observatory has a warm room.  You can eliminate the tiring round trips but staying overnight.  Also consider the wall heights of your observatory.  The mirrors on dobs are near the ground, and simple trig will show that unless you are far away from the walls, they will limit how low you can see.  That may seem ok, unless you consider where a lot of the interesting targets.  For me, Sagittarius and Scorpio (as examples) are fairly low in the sky, and so I have to find an alternative to my dob in the ROR in order to see some of the better M objects in them.

 

My last thought for pondering is build the structure first, and using your 32" in it for a while.  You may find that you do not need something larger once you're more permanently under those dark skies.

[macdonjh]

Ittaku,

 

One other thing to consider: a rolling warehouse ladder, like Jon Isaacs advocates for.  They are more like rolling staircases than ladders, so may not be frightening for you.  A permanent observatory would be the ideal situation for one of those.

 

https://www.grainger...c6a463d4f0c63b9

 

The question, though, is how would you close your roof with something this tall inside?  Custom modifications such that the top section could be lowered before your roof is closed?  Boy, a whole  new project.

[MitchAlsup]

I agree that it will always be best to have a sleeping room in a distant observatory--possibly well enough equipted to stay for a week. In addition, this would be a good place to put the machine shop and wood working shop to assist the implementation of the observatory and maintanence thereof.

 

The sleeping room prevents having to drive back once you are exhausted from observing. But, in tollerable weather, I have used the back of an SUV to cover that situation.

[Ittaku]

Sleeping room's a good idea, but there is a house on the land as well if I decide to stay for the night, so it's not an issue here.

 

Thanks for your comments so far.

 

I should add a few comments to the top post which help explain mu situation as people come up with ideas or have questions.

Edited by Ittaku, 24 January 2021 - 03:47 PM.

[MitchAlsup]

The short short version - I have land with no local illumination and an SQM of approximately 21 that I want to set up a very large observatory on with a reasonably large amount to spend for DSO observation. I'm terrified of heights and don't want to climb up for a very large Dob. The Optiques Fullum foldeds look to be the solution I'm looking for. I have soft plans for a slide-off-roof observatory. Yes I'm relatively inexperienced, yes it's a lot of money, yes I'm crazy - please don't debate that as I know this better than anyone.

 

What are people's thoughts on the quality and suitability of the light collector and observatory setup? If anyone has experience with systems of this size of any sort I'd be most grateful for your experience and lessons as well. Thanks!

 

Other information:

The land is a one hour drive away and I plan to go out there just about any clear night, which is why the compromise on a Bortle 4 location.

There is a house on the property that I can go to and from so resources and the potential for a place to sleep are not an issue.

Power would be very difficult to get to the location so I'll have to use standalone power.

A 20" F/3 can be used feet on the ground, even by short adults

A 30" F/3 is 1 large step or 2 small steps--you could make a movable wrap around raised platform here.

A 40" F/3 will put your feet 1 meter off the ground (maybe a bit higher)

 

If you don't mind compromizing a few degrees of the horizon, you can place the scope in a short depression so you can use the 30" F/3 feet on the cement, alternately you can build a raised platform around 1/3 (or more) of the scope and still have your feet on a stable floor.

 

With current EPs, and coma correctors, the fastest visual scope you can use is about F/2.75, and here, this is a somewhat specialized instrument--specialized for lower power and wider FoVs. Whereas by F/3 the instrument becomes more general purpose and most higher end EPs will tollerate the F/3 (F/3.45 with Paracorr 2) light cone with pinpoint stars edge to edge (think Ethoi)

 

I want you to consider the shedding a bit of aperture (30"-35") and placing it in a shallow depression (or raised observing platform) for feet on the ground/floor/cement instead of the 40". You loose a little bit of depth (0.5-0.25 magnitude) save $$$ big time and have a more comfortable to use machine.

Based on the Kangaroo scene in "Corcodile Hunter", make sure the telescope, while not being used, is imune from crazy people out in the woods shooting at various things.

[Keith Rivich]

IMHO...if your heart is set on the 1m scope go for it! Once set up its going to be a great scope. 

 

From an observational point of view I have quite a bit experience with scopes to 36", and occasionally a 48", in varying sky conditions. Even under perfect conditions there is not a huge difference between say a 32" (like Wade's) and a 40" scope. A  huge advantage of the 32" is you can mount it on a platform (table) and run it on a 12v battery. A second huge advantage is you can easily take it down and travel to darker skies, occasionally, if you so desire. 

[Ittaku]

IMHO...if your heart is set on the 1m scope go for it! Once set up its going to be a great scope. 

 

From an observational point of view I have quite a bit experience with scopes to 36", and occasionally a 48", in varying sky conditions. Even under perfect conditions there is not a huge difference between say a 32" (like Wade's) and a 40" scope. A  huge advantage of the 32" is you can mount it on a platform (table) and run it on a 12v battery. A second huge advantage is you can easily take it down and travel to darker skies, occasionally, if you so desire. 

Great thanks, but how does the 48 compare to the 40? People seem keen on me going smaller and spending less, in the quest to avoid going a folded design, but I want to spend more and go bigger. To be honest, I even considered the 50".

[eyeoftexas]

Then by all means go for it.  If I could, I would too. 

[Ittaku]

Then by all means go for it.  If I could, I would too. 

Haha, that's more the kind of response I was hoping for, but I did open it up for debate.

[Keith Rivich]

Great thanks, but how does the 48 compare to the 40? People seem keen on me going smaller and spending less, in the quest to avoid going a folded design, but I want to spend more and go bigger. To be honest, I even considered the 50".

I have had the opportunity to view through both a 36" and a 48" under very good conditions during the same week at the Texas Star Party. Often times looking at the same DSO. 

 

Here is where things get interesting...

 

The more experienced observers got the most out of the aperture difference, detail wise. Less experienced did not.

 

The folks that went with us that own small scopes got the bigger wow factor. Those of us that already have big scopes did not experience a wow factor. 

 

Does that make sense?

 

I do not have direct experience comparing a 40 to a 48 but I suspect the view is fairly similar. As one gains experience the differences become more pronounced. I do regularly observe with my 25" while a friend of mine has his 36" scope. The difference is there but it is not "knock your socks off" better.

 

Now, going to the 82"...that's pumps the wow factor way up!

 

For regular observing a 50" would definitely be the scope I would choose...

[Ittaku]

The more experienced observers got the most out of the aperture difference, detail wise. Less experienced did not.

The beauty of that is that experience comes with... experience.

[Augustus]

I would go with a traditional Dob from SDM honestly. Better stray light control, easier collimation, and a LOT cheaper.

[Ittaku]

I would go with a traditional Dob from SDM honestly. Better stray light control, easier collimation, and a LOT cheaper.

Okay I've avoided saying this but for reasons I don't want to go into, I can't wait the 24 months lead time. I'm looking at 8-10 months with OF.

Edited by Ittaku, 24 January 2021 - 11:06 PM.

[Augustus]

Okay I've avoided saying this but for reasons I don't want to go into, I can't wait the 24 months lead time. I'm looking at 8-10 months with OF.

Oh, sorry to hear - in that case I suppose a meter is a meter. 8-10 months for a meter-class scope sounds INSANELY optimistic though. Shipping that alone is going to take a while I'd imagine. 

 

Personally if I had some sort of deadline to get and use the scope I wouldn't be going this large; I'd get something in the 20-30" range with less of a learning curve or hassle to set up.

[Ittaku]

Personally if I had some sort of deadline to get and use the scope I wouldn't be going this large; I'd get something in the 20-30" range with less of a learning curve or hassle to set up.

Thanks, I should say I've got a 20" on the way already to arrive next week. I just need time to mull over the 40" a bit longer.

[Augustus]

Thanks, I should say I've got a 20" on the way already to arrive next week. I just need time to mull over the 40" a bit longer.

Fabulous. I think that makes your purchase a lot more reasonable. You should be able to learn and see a lot with a 20" in 8 months. 

[slavicek]

Okay I've avoided saying this but for reasons I don't want to go into, I can't wait the 24 months lead time. I'm looking at 8-10 months with OF.

Sounds like there are time constrains on how long in to the future you will be able to observe.

In that case I'd recommend that you look into the observing from different angle - Renting a observatory. I am not sure if it is even possible in Australia but here in the US you can rent the whole observatory at several locations. While I was waiting for my DOB to be made, I have rented the 20" observatory at Kitt Peak, Arizona for overnight observing - twice. And Once I will reach the limit of my 22" Dob then my plan is to rent the 30" at Mount Lemon observatory.... And Hopefully, one day I will go all the way to Mt.Wilsons 60" and 100" telescopes. If money is not the issue (which seems to be the case here) then there are great benefits of renting an observatory. Just my 2c.

[Ittaku]

By the way, I know these calculators are extremely rough and it appears this one is more aimed at smaller apertures, but if I read it correctly there is a taper in the ultra-large apertures, presumably due to relative light pollution effects, and going from 40" to 50" is only worth a measly 0.2 magnitude more.

https://www.cruxis.c...ngmagnitude.htm

[Allan Wade]

By the way, I know these calculators are extremely rough and it appears this one is more aimed at smaller apertures, but if I read it correctly there is a taper in the ultra-large apertures, presumably due to relative light pollution effects, and going from 40" to 50" is only worth a measly 0.2 magnitude more.

https://www.cruxis.c...ngmagnitude.htm

Yes you've discovered the diminishing returns of increasing aperture. On the flip side though, the number of observable deep sky objects increases enormously with each 0.1 magnitude gain at these very faint magnitudes.

 

You can understand now why the first thing I jumped on was your observing conditions. Those Fullum scopes double in price going from 40" to 50" by the time you get one in hand, yet you see the small increase in limiting magnitude you gain. While moving from a Bortle 4 to a Bortle 1 location gains you significant capability. My 32" under SQM 22 will go as deep as a folded 50" under SQM 21, and for 1/6th the cost. The loss of contrast from the huge secondary and the brighter sky is significant. Big scopes are built for galaxies, and nothing hurts galaxy observing more than bright skies.

 

It may not be what you want to hear, but just trying to throw some experience into the discussion, so you get value for the money you're investing. I'm not for a second saying don't spend the money, I'm just trying to explore some limitations in your plan, as I see you spending an enormous amount of money and not getting much value for it. I will most likely plonk down some cash one day for a bigger scope. If I put down $300k I am going to be certain I get $300k worth of observing performance. 

[Ittaku]

Yes you've discovered the diminishing returns of increasing aperture. On the flip side though, the number of observable deep sky objects increases enormously with each 0.1 magnitude gain at these very faint magnitudes.

 

You can understand now why the first thing I jumped on was your observing conditions. Those Fullum scopes double in price going from 40" to 50" by the time you get one in hand, yet you see the small increase in limiting magnitude you gain. While moving from a Bortle 4 to a Bortle 1 location gains you significant capability. My 32" under SQM 22 will go as deep as a folded 50" under SQM 21, and for 1/6th the cost. The loss of contrast from the huge secondary and the brighter sky is significant. Big scopes are built for galaxies, and nothing hurts galaxy observing more than bright skies.

 

It may not be what you want to hear, but just trying to throw some experience into the discussion, so you get value for the money you're investing. I'm not for a second saying don't spend the money, I'm just trying to explore some limitations in your plan, as I see you spending an enormous amount of money and not getting much value for it. I will most likely plonk down some cash one day for a bigger scope. If I put down $300k I am going to be certain I get $300k worth of observing performance. 

Yes you've made that clear. That said things going well I could always move it to a darker site in the future anyway, but that won't offset the quality of the secondary you keep bringing up.

[Allan Wade]

Have you had the chance to look through a large ladder dob? If not, I would suggest you get in touch with the Astronomical Society of Victoria and ask if you can spend a night on their 40” f/3.3. Then see how you feel about ladder observing after that. A proper observing ladder with closely spaced steps can be quite comfortable. If you definitely don’t like the experience, that narrows down your options.