Somebody stop me! Aperture fever

[floyd_2]

I've been using my 10" Meade LX200GPS since they were first released, and still love it. I bought a Stellarvue 80mm guidescope for it not long ago and just started using the 80mm as a grab'n'go on an Alt-Az mount.

I'm really impressed with the 80mm as a scope in its own right. Whilst it will never be anything remotely resembling the 15" dob I had years ago, it still shows more than I expected under my suburban skies at Cecil Hills (NSW). I was looking at the Sombrero just the other night through it - very easy to find with a 27mm panoptic (I really thought that I had no chance of finding it). Unfortunately, an 80mm will never pick up much in the way of detail on an object like this.

So now I have aperture fever once again. I love my 10" for photography and have it set up accordingly. However, I had forgotten just how much I also enjoy sitting out under the stars and star hopping around the sky with a big(ish) dob lingering over this object and that.

As I'm on a bit of a budget, SDMs and obsessions are out :( I'm considering one of the Orion XX14i scopes at the moment. They look quite nice and are just about the right size. Anything over about 15" is getting a bit too heavy for my liking, and perhaps just a little tall. I haven't forgotten about the Meade Lightbridge 16" scopes, however they seem just a little too large and heavy, and I'm not so sure about the build quality on them. I guess you get what you pay for, but I would hate to end up with a nice big mirror, with a mount that makes me cringe every time I use it.

After that massive preamble, I'm just wondering if anyone has been down this path and what options you may have come up with.

Dean

[mental4astro]

Got the optics? Not convinced by OTA? -> DIY

Only way to cut the cost and get something custom made to you needs and standards.

I've been there- first pic

I've done that- second pic

Cost, approx $600 the DIY, cannibalising as much as possible.

:D

[AstroJunk]

Yup, the choices are stark.

If you are handy with a saw, then pick up a suitable second hand donor scope and have a go. SDM/Obsession scopes are based on a fully published design: http://www.amazon.com/Dobsonian-Telescope-Practical-Building-Telescopes/dp/0943396557

Otherwise, I guess that a man with a box full of Naglers ain't going to be happy with a wobbly lightbridge. You are just going to have to sell your car and buy an SDM ;)

[Paddy]

16" with a lightweight build is the way to go. Not too heavy and not too tall. Would have built one myself but was lucky to get an excellent home build second hand.

[ausastronomer]

Having owned both tube style dobs and truss dobs, I will never go back to a tube style dob again. A truss dob is just so much more storable, portable and transportable.

If you can't afford a premium truss in the 12" to 15" aperture range, or build your own, consider the 12.5" lightbridge. From my experience all of the 10" and 12.5" GSO optics I have seen have generally been very good to excellent, apart from the odd lemon that has slipped through the net. My own 10" GSO mirror is exceptional, almost the equal of just about any premium hand made mirror. Two of the 12.5" lightbridges that I have used have also been right up there. The 2 x 16" Lightbridge's I have used, whilst very useable were optically not the equal of the smaller aperture GSO optics I have used. I guess it comes down to large fast optics being somewhat more difficult to "mass produce" than smaller aperture slower optics.

Cheers,
John B

[floyd_2]

That's a fine looking telescope you've built Alexander. Very impressive indeed! Whilst I have a fairly well optioned workshop, I'm not sure that I have the time to invest in building my own scope. I've had the Kriege dob bible for years but have never taken the plunge and actually built a big dob.

I actually sent David an email to find out how much another 15" obsession would cost to land over here but, based on what I already know, I think it's just going to be too expensive to own an obsession again :(

After owning a 15" truss style dob before, I agree that there's no goingback to tube dobs, John. For a big scope I don't think you can go past a decent truss scope and will be heading down that path one way or another.

I would prefer to spend my dollars on aperture, however given that the pickings are slim in the 14" - 16" category it's become a difficult decision. The build quality on the lightbridge scopes looks to be fairly average, and I'm not sure that it's worth having a 16" mirror if the mount isn't smooth, stable etc. There's something about a three sided truss vs 4 sided truss that puts me off too.

I'm busily scouring the web for reviews and opinions on the lightbrige and XX14i to help me along the way. I've taken a look at the Discovery scopes at OPT as well, but I think the landing price in Aus is a little on the high side.

Fortunately I'm not in a hurry to spend any money, so I'll continue reading and asking questions. I really appreciate the views that you have offered guys.

Dean

[mental4astro]

Thanks for the compliment, Dean. I like using it too.

Most of the time I spent had been on the planning. I took my time on the planning, including reading the Kriege book from cover to cover. The building part was over four months, between work and family, and with limited tools, but the with the help of a second pair of hands from Hickny when needed. I've got the scope I wanted, and well worth the slow year's planning and careful crafting over four months (one of which nothing happened).

I'd suggest it is worth considering the DIY option some more. All I had tool wise was a circular saw, power and cordless drill, cheap router and a mate with a band saw and drill press.

Though its crafting was relatively inexpensive, I did not skimp on the principles held in the 'good book'. I had to work out how to craft the necessary components, and how to make them reliable and predictable. I only wish to have a better decked out workshop to have been able to machine components I would have preferred. But, necessity is the mother of invention.

There in lies the challenge. Limited funds, but unlimited enthusiasm, ;).

[pgc hunter]

Agreed. The optics in my 10" GSO are superb, to the point where I'm reluctant to sell it even though I have my 12" with a mirror that is rated as "up there with the very best". I've used the 10" at mags over 600x to observe small planetary Nebulae, with great results.

[mic_m]

I’m also after a 16” dob and I have the same problem; all the large aperture commercial dobs are way too heavy and bulky to easily move and transport.

I have been looking at both the XX14i and the LB 16, but they have too many design compromises especially in terms of unnecessary weight and bulk for me to seriously consider either. Ultimately, I have decided that I’m not going to spend thousands of dollars on something that I’m not ecstatic about. I would rather just save up a bit more for a premium scope or wait until commercial producers make something more compact.

Alexander, I really like your compact scope. It reminds me of the ones made by Dobstuff (http://www.dobstuff.com/index.htm). I would really like to see GSO or Synta come out with someting like these!

[erick]

There are a lot of options for building a scope around a quality primary mirror. Most quality primary mirrors take quite a while to get into your hands - so you might like to choose and order a primary from a specialist maker and pay that off. That gives you time to save your dollars to build a good scope around it - either DIY or from a scope manufacturer. Spread the cost over a couple of years?

Unless you pick up a premium 16" mirror off the shelf or second-hand - then you are stuck with expenditure now!

[mental4astro]

Dobstuff has the license to commercially produce the this design from the original concept devised by Albert Highe:

http://pw2.netcom.com/~ahighe/17_5ultra.html

Yes, it is my main source of inspiration for Odessius. However, mine is further developed from Albert's to suit my needs and capabilities to manufacture. Tnott put me onto Albert's creation.

Odessius, when 'shortened' for storage comes to just above my knee, shorter than Albert's.

Greg Babcock, though for me, has the ultimate DIY scope. His creation has inspired quite a following. Including Tnott.

http://synrgistic.com/astro/24inch.htm

I'd really like to know how to weld aluminium. It would be one heck of a skill to be able to exploit! :atom: :work: :rover1: :driving:

[floyd_2]

The biggest drawcard for the mass produced mid sized dobs is their price. To land an Obsession 15 classic with an Argo over here will cost almost bang on $10,000AU, as would a Starmaster, as would an SDM of similar size. Whilst I know that you get your moneys worth with an Obsession, and am sure that the same goes for Starmaster and SDM - it is a LOT of money. So once again we poor people head back down the path of mass produced dobs. I think at the end of the day you get what you pay for. You can't pay for a combie van and expect Mercedes.

As I'm on a budget and am not prepared to spend $10,000 when I have a young family, I think that compromise is ok. I think it more gets down to choosing the scope that most closely matches your requirements. If you have limited space, or need to get out and about with your scope - then perhaps the XX14i is a more likely candidate. It's lighter, and more attention has been given to portability than on the LB16. If you can plonk the scope in an obsie and don't need to heft it around much, perhaps the LB16 is a better choice. For me, I still can't get past the thin chipboard mount on the LB16, its footprint, the alt bearing and a few other things.

Certainly building a truss dob would be about the best thing you could do to get around all of these problems. You would end up with close to exactly what you want, and you'd know that scope inside out.

I've seen a lot of people modifying their LB16s in this way and that to improve the design. So I guess that's the final option - compromise on an LB16 and then modify it to your hearts content (a new rocker box sounds like a great idea, as do decent alt bearings).

Decisions...decisions....

Dean

[mic_m]

I can empathise with much of what you are saying, I don’t want to spend $10000 on a scope either, but I am not going to spend ~$3000 for something that is not complete. Unfortunately, there is no midmarket in Australia (in the US there are several companies and custom builders that make well priced structures).

Regarding the LB; a little attention to detail would go a long way and make it a very attractive option. I really don’t see why the money spent by ATMs on modifications can’t be spent the company at the production line to make the LB more compact and more serviceable out of the box. Here is the description of a LB16 base modification (http://www.batchelors.net/personal/telescope/16-inch-meade-lightbridge-telescope.html) to reduce its size by half, it don’t think that incorporating a similar design into second generation LB wouldn’t be too difficult or costly for Meade.

[floyd_2]

Oh dear. Nobody stopped me....so I was forced to order an Orion XX14i today :D

I was looking at the $AU falling, and thought that the XX14i would be about due for another price rise. It was sitting at $2995AU yesterday. I've been talking to Sirius Optics and Astro Optical about the XX14i trying to decide what to do. Sure enough, this morning I received an email from Sirius saying that the price just went up to $3220.

I rang Astro Optical and they were still selling at $2995 (I think it was $2695 before).

It was a hard decision between the meade 16 and the XX14i, but in the end, it boiled down to this for me:

The meade has a terrible mount that is way oversize, with tiny Alt bearings, made of chipboard that's too thin (current LB owners please don't be upset with me for that comment)
The meade, at 16", was getting just a bit too big and heavy for me.
I didn't like the three way truss design of the meade
I've read too many reports of people having to redesign the mount on the meade / replace it altogether
The Orion is a perfect fit for my observatory, which currently has a desk / computer and a Meade LX200GPS 10" in it.
The build quality on the Orion looks to be significantly better than the meade.
The orion can be handled by one person without any trouble. At 30kg, the tube assembly can be lifted by the truss poles onto the mount without too much issue.
The orion has 8" alt bearings with tension adjustment, 4 sets of truss poles, integrated weights behind the mirror cell, ebony star formica / teflon combo for the azimuth, is balanced for a 9x50 finder PLUS eyepieces....and so on. The mount is also collapsible in case I want to take it somewhere.
The orion, at 2" smaller than the meade, was beating it hands down in too many areas. As a former 15" owner, 14" was fine for me and suited my requirements to a tee. 14" still has almost double the light gathering power of my 10" LX200GPS, which is just great for a purely visual scope.
The orion has an object locator which will be handy for me in suburban skies where star hopping can get a little challenging at times. The beauty of a passive system like this is that I can choose not to use it if I know where I'm going, without losing tracking etc as I would with the LX200GPS.
I read through the entire XX14i manual last night and I was happy with what I read. It'll never be the obsession that I owned years ago, but it will be close enough (especially for the price - 30% of the cost of an obsession 15).

Thanks to everyone for your insights.

Dean

[AstroJunk]

Looking forward to the review Dean, this looks like a splendid scope :thumbsup:

Nice one.

[coldspace]

Yep,me too, look foward to a review as well mate.

[floyd_2]

Ladies and gentlemen,
the time has come. My new Orion XX14i is waiting for me at Astro Optical Supplies. I'll be the one on their door step in a sleeping bag when they arrive in the morning.

It all seems to have been timed to perfection. I completed my new observing area just a few days ago. I put in a lovely 8m x 3m paved area just outside the door of my obsie shed. As this area sits atop a retaining wall with no wheelbarrow / bobcat access, we shifted more than 7 tonnes of pavers, road base, sand and clay with buckets, shovels and our hands on the long weekend :help:. I can't wait to christen the new area with my new XX14i!

Dean

[Paddy]

Good news Dean, I reckon you will have some good nights with that one.

[floyd_2]

I collected the XX14i as planned this morning. Luckily I drove a van, as the cartons would not have fitted into a wagon. Everything was either double or triple boxed with double layer core flute cardboard, and fortunately the primary (centre spotted) unpacked in a single piece :)

The scope only took a couple of hours to assemble. I took my time and read the instructions carefully. The instructions were superbly written, and I don't believe that you could assemble the scope incorrectly if you follow them.

There were no parts missing, and all holes etc lined up perfectly during assembly. I only needed an extra spanner and phillips head screw driver during the assembly. All other tools were provided. It's a very nicely designed scope. I purchased the light shroud with the scope as well - which is made from super heavy spandex / lycra material. I was expecting rip stop nylon, but I really like this heavy duty material.

The OTA is quite heavy to lift out of the rocker box fully assembled as shown in the instructions. With the truss tubes removed, it's quite manageable but still fairly heavy.

I noticed that the secondary doesn't have a typical secondary holder, but rather, is glued onto a smaller cylinder connected to the spider. I guess this isn't a problem, just different. The secondary came pre collimated and they did quite a good job at the factory with it. It's out by just a tiny tiny bit - but nothing worth worrying about. I actually tried to loosen the secondary centre screw so that I could twist the secondary axially just slightly, but the screw has been put in far too tightly at the factory and I was unable to loosen it. Fortunately, it's well collimated.

I noticed that the altitude bearings are silky smooth, with adjustable tension. Very nice. The azimuth bearing is ebony star formica on teflon, but seems to be a little stiff for my liking. Having said that, the scope moves very positively in azimuth with zero backlash, but I would like it to be just a little more buttery. I might work on that later on (perhaps polishing the teflon with talcum powder might help, or larger teflon bearings).

The Intelliscope computerised object locator seems to work at face value. Certainly, the encoders look to be doing their jobs. However, I'll find out just how good it is tomorrow night. It looks to be quite easy to navigate and is a little similar to my LX200GPS hand controller.

I didn't manage to get the scope outside to star test the optics tonight. That'll be a job for tomorrow night when I move the scope into its new home in my obsie.

All in all, it's a superb looking scope that built perfectly. I can't wait to take a look through it tomorrow evening!

Dean

[Starkler]

After having owned a 10" tube dob, a 15" sdm and a number of other smaller scopes, if I were starting out again from scratch knowing what I know now, I would just buy a 12" skywatcher collapsible and be happy with that.

All chinese scopes require some work on the motions to become acceptable, but for the SW its pretty simple.

[floyd_2]

Having used the XX14i properly tonight, I must say that I'm quite happy with az bearings after all. They're firm enough to make minute corrections possible when trying to locate an object using the object locator. If it was more buttery as I originally posted, I think the small corrections would be just a tad more difficult. So, I'm happy!

I had to shim the finder just a tad to get it to align tonight. No big deal and only took a few seconds. I also noticed that my 12mm and 16mm naglers come to focus in this scope just before the full extent of the focusser. It'll probably be worth getting a small extension tube to keep things comfortable.

I was surprised at how easy it was to get going with the object locator, having never used one before. It literally took about 1 minute to align, and I was ready to go searching. Pity the sky was washed out with moonlight and clouds tonight. I made the most of what I could get my eyes onto and was more than pleased with the views. Collimation was spot on (checked inside out outside focus) - so all in all, a very pleasing new scope that ended up costing me about $7000 less than an Obsession 15".

Dean

[floyd_2]

I thought I must just add an extra snippet to this thread in case anyone interested in the XX14i is reading. I previously commented on the Az setup being firm. I just smoothed it out nicely by treating the formica on the underside of the mount with Armour All. After three applications the mount was nice and smooth, and it took all of about 1 minute to complete - no disassembly required.

Dean

[Archy]

There is nothing wrong with the mount on a Lightbridge 16, so don't worry you won't cringe when you use it.

[floyd_2]

I thought I may as well continue on with my endless XX14i ramblings for anyone interested now or in the future.

I noticed that eventualy armourall can cause extra stiction in the azimuth bearing, so I tried a few things:

1. Remove armourall and replace stock teflon az bearings with larger 50mm square (beveled edge) virgin teflon bearings (6mm thick). This in itself proved to have about the same friction as the stock teflon bearings - not worth doing in itself.

2. Add armourall to the formica along with the new teflon bearings. No real difference and not worth doing as the stiction problem will soon return.

3. Remove the armourall and clean all surfaces. Try a very small amount of fine talcum powder as a lubricant. Absolutely no stiction. Friction increased too much.

3. Clean all surfaces and try dry lubing the formica. Stiction reduced, but friction greater than without lube.

4. Clean all surfaces and polish formica twice with Turtle Wax (the $11 one in a tin) per Dave Kriege. Friction reduced considerably, stiction reduced.

5. Apply 2 thin coats of armoursll over the top of the Turtle Wax per Dave Kriege. Friction reduced further still, stiction almost gone. The az bearing is now significantly better than it was out of the box.

So far, option 5 has yielded the best results and is the solution I'm sticking with (until next weekend :D )

Dean

[mental4astro]

Hi Dean,

Who was the bright spark that tried wax polish first? It certainly would never have occured to me. It is really thinking outside the box.

The difference wax polish makes is extraordinary.

Also, a periodic clean of the Teflon pads and the bearing surfaces and then a reapplication of the wax will restore the beast to its optimal performance. You become unaware of the gradual deteroriation of the surface quality as dirt slowly accumalates, and the restored condition will surprise you as much as the very first time.

[Rick Petrie]

Hi Dean
Did you try the smear of Kero over your ebony star to remove all gunk and wax.(kero dissolves wax really good)
Kero will also aid in a minor lubrication of the bearings and should not gunk up with further use.
As you know I used this method on my XX14i and have had no stiction problems since and the az action is very smooth. Kero also will not affect the teflon or ebony star laminate.
Cheers Rick

[floyd_2]

Hi Alexander and Rick,
I've read that a lot of people use Sailkote with great success, but I'm keeping that one up my sleeve for now as it's about $25.00 a can. Others have moved the bearings inwards with great success, however, that will take the addition of more formica as Orion trickily only used a ring of formica on the base of rocker. I'm not convinced that moving the bearings inwards would be a good idea anyway as the teflon pads would no longer be directly over the feet where the greatest support is.

I didn't try the smear of kero yet Rick. I actually used a little solvent (again, per Dave Kriege) to clean the bearing surfaces and it seemed to work really well (no better than wd40 though). However, given that I seem to be in the swing of cleaning, then trying new ideas to eliminate stiction, I may well be on the kero path this weekend :D

On a side note, I finally managed to get the secondary cell loose on my scope. The scope arrived with a well collimated secondary but it needed tweaking. Finally, after much persistence, I managed to get the secondary loose and have now collimated it perfectly using my trusty tektron auto collimator eyepiece. I'm not sure how many people use an auto collimator properly. I've read that as long as the image in the middle is dark, then your scope is collimated as the light path is closed. However, there's an extra step where you insert something coloured and fine into the light path between the secondary and the draw tube in good light (I use the tip of a yellow cable tie). As the cable tie reaches the centre of the light path from one side, you should see a mirror image of it approaching from the opposite side. If they meet exactly in the middle of the light path, the centre image should flush with the colour of the object in the light path (yellow in my case). If this doesn't happen, you still have work to do on your secondary. This might be old fashioned now that laser collimators are about lol.

Dean