Medium / Large Telescope for "quick sessions"?

[RolandosCY]

Hi everybody...

I know this sounds kind of strange, but I bet the majority of us owns two or three telescopes in different size ranges to cover various observing situations. Most of the people in this forum own a rather large dob, 15-30" in diameter, and from what I gather they also own one or two small refractors in the 2-4" range. I fall in this same category. I have an 18" dob as my "big" gun, and I also have a premium 4" refractor (Tak FS102) and a small 3" ED80. With this set-up I found myself caught in a rather strange situation:

Being an almost exclusively deep-sky guy I totally enjoy (of course) the views through my Obsession. But there are times that either due to time constraints or worries about the weather I want to go to a dark sky with something more manageable. Up to now, this role had been fullfilled by the two refractors (which have the added benefit of wonderful wide field views). But, (yes, there is a huge "but"): When I used to own a 12" dob for many years, this seemed to be ok. Now, I find the relative difference in the views between my 18" and my 4" (let alone the 3"!) too big! Yes, I enjoy the views my FS102 gives... But even for two hours of observing (especially at dark sites) I feel I need something bigger than that. I am considering obtaining either a 6" achromat or an 8" dob. I lean forward to the refractor mainly because it will not need an hour to cool down, collimate, etc (important if you have 90 minutes of observing time!), and because I really enjoyed the deep sky views I had through it.

I would like to know what other members of this forum have, and what their opinions are in this matter!

[MarcE]

Interesting question. Since i own my 24" dobson i ask myself same question about the "optimal" second scope. Personally i am sure you need for several reasons a smaller scope, if you need to travel to dark sites for observing.
In my opionion for apertures below 16" you can always observe with the main scope, because you do not need to much space in the car and set up/break down are not too much effort.
With larger scopes the situation can differ, e.g. in my case i sometimes combine observing with travelling by car to a business trip. In these situations observing time is limited, time for packing all stuff in the car is limited and i do not like to park my car full of astro-stuff somewhere.
For me a refractor is no alternative, because also too large, heavy and 6" aperture is not enough for me.
Best works a 10inch dobson (no truss tube), you can easily set up and you only have to carry two pieces (plus chair, eyepieces..). I use my 10"f5 quite often for observing e.g. Herschel objects. Also interesting is to try objects at the edge of visibility with the small scope. Sometimes i am surprised how deep this small dobson goes (e.g. 4 companions of NGC7331).
Nevertheless i ordered a 16" f4.5 traveldob with total weight of 17kg for these "quick observings" and travelling by airplane. I know that the hazzle of set up is higher than with the 10incher. Honestlyi am not sure, which alternative is the better one (very quick set up with 10inch or more set up time for 16"). Both will definitely need less effort than the 24incher.
For your situation i would suggest a 10" solid tube dob (8inch will also work, but i like 10inch much more) or a 12-14 inch travel truss dob.
Clear skies
Marc

[MarcE]

I forgot your two points collimation and cool down time, because i never think about it.
Honestly, collimation is normally not necessary with a solid truss dobson (i check it every time) and for me no argument with a truss tube.
Cool down time can be an issue, but in not worry about that. I start observing typically with objects that don't need too much magnification (e.g. nebulaes) and then observe later with higher mag.
After latest 1hour these thin mirrors work very well.
Summarized: both points are not worth thinking about an refractor.
BR
Marc

[Howard B]

I have two other scopes beside my 28 inch, an 8 inch f/4 and a 13 inch f/4.4 which are also home made. I don't use these scopes when I don't want to bother with the 28, but in situations where I can't use the 28. The 8 inch is used almost exclusively in my backyard because it's easy to get it there - my backyard is about 3 meters higher than the basement/garage where the 28 lives and there's no way I can get the 28 up the steps and through the gate unless I took it apart and rebuilt it there! The 13 inch scope is a travel scope and has made one very successful trip to Hawaii so far.

I designed my 28 to be easy enough to load into my van and set up in 15 minutes at a dark sky observing site that the effort to this has never been an obstacle to observing, unless I'm so tired or busy that I can't observe with any scope. My van is my most important observing accessory for the 28 because it allows me to easily transport it. Without the van I'd use the big scope much less often simply because I couldn't transport it a dark sky.

[Marko]

If you find yourself in a situation where you may want to also do public star parties to share views or you may decide to meet friends who post to go out on a moments notice for a quick hole in the sky then I say having a 12" range low-hassle scope to complement the larger dob is GREAT!

For my quick scope suitable for above needs I have found the 12" meade lightbridge as ideal and here is why. Clever breakdown and setup get it from the back of my van to being setup in under 5 minutes. Add a few minutes to colimate after cool down. I can lift all pieces without having to use ramps like I do for my 18" starmaster. All screws are captive so I never misplace or drop any screw. The trusses are very clever in that they fold together so you have 3 pieces, each with two rods that hold vertical on their own in the mirror box while doing setup or tear down.

Is it the best mirror and the best optical design around. Frankly, No but its good enough. It's ultra fast setup and extremely low cost on Astromart are nicely in balance. When I use it I am not doing serious observing generally so it is very nice as a package deal.

I can do more serious observing if I were to go way out to darker skies but hay, that is where I'll want the 18".

[nicoscy]

If I may add to the thread, the point being that Rolandos can be at a dark site with a 20 minute drive (SQM between 20 and 21). The refractor will take about 5-7 minutes to set up. He can start observing at once and fully utilise those 90 minutes available for observing. Any suggestion for a 10" or 12" dob does not take into account the nearly 1 hour required for the mirror to cool down.

The issue here is to have a rig that allows a quick 90 minute session, with ease of setup and no need for extra time for either collimation or cooldown. Knowing Rolandos, I don't think he would be willing to observe through any Dob without first collimating and then being patient enough to wait for the mirror to cool.

But then again, I am a refractor guy, soon to join the Dob Dark Side.... Lots to learn...

[Astrojensen]

I have a 12" Lightbridge. I have been extremely positively surprised by how well it works as a quick-look scope. I first throught cooldown would be a huge issue, but this turned out not to be the case. Right out from the house, after spending a few minutes on collimating with a laser and barlow, I can immediately begin with 75x and enjoy great views! After ten to twenty minutes, I can go to 100x and after another half hour, I am usually at 150x, which is often as much as the seeing will allow around here. I do have the fan running, of course, which improves things quite a lot, even without any special baffles to direct air streams, etc.

Now, 75x - 100x on a 12" may seem ridiculously low, but a 3" or 4" refractor starts to get a little dim at these magnifications already, while the 12" is nice and bright. It will require relatively dark skies, though, or else the background is bright grey and washed out. Not pretty. Galaxies usually look a lot better at 100x than 75x around here and I have pretty good skies (not perfect). Still, the view at 75x, even with so-so transparency is vastly better than what my 6" throws up at identical magnifications. Where the refractors wins, and wins big, is wide field deep-sky and lunar/planetary, until the 12" has cooled down.

I usually carry the 12" LB OTA out fully assembled. I set it on the ground and go inside and get the rocker box. Find a place in the garden and plop it down, then set the OTA into the rocker box. Then I collimate. It all takes less than ten minutes and hardly raises a sweat. I have even done it to chase bright Messiers and NGC between clouds! I never thought I would do this when I bought it. Use a 12" as grab 'n go? Ridiculous! But it works very well indeed. The thing about hunting things through sucker holes is that when the view is so short, you want objects to show up clearly and unquestionably. You want bang for the buck. The 12" offers that, my smaller scopes don't.

And now I usually store the 12" in my garden shed, so it's fully cooled as soon as it hits the grass. Grab 'n go doesn't get much better than this.


Clear skies!
Thomas, Denmark

[Dragan]

Since we actually live in Chicago, for any really serious form of observing I have no choice but to drive 2hrs west of here. And that will always be with my primary scope.

Now I do have two smaller scopes for the "quick session". I have a stock Orion XT8 that is always setup and ready to go that I'll use from the driveway here at home. It isn't ideal but for an inexpensive little grab and go it works just fine.

I also have a TV101 that I had purchased about 10years ago with grandiose dreams I'd get into astrophotography and make world class images that would take the world by storm....but needless to say that never happened.

Too much work! :P

[Marko]

Thanks Thomas, fellow believer/owner of the 12" LB. I very much like it for the close medium dark sites as it is a good match for very fast setup (for a 12" range scope) and cools down well enough with the built in fan to make it well worth the wait. My 11" SCT is hard pressed to cool down as quickly and is a beast to put on a tripod with my back, thus the 12" LB I prefer.

For me a 2 hour session IS what I would call a 'quick' session so I missed that as being the point earlier. I do see the point on 'super fast sessions' and the refractor's value but the extra 10 minutes is normally ok for my 'quick' sessions. A well made APO of course has it's own superior views for several bright targets so that too allows it to shine on some targets.

Whatever it takes to get out and have some fun is often personal preference and as long as we do get out to view, all scopes are a fine choice.

So when are the darn winter cruddy skies going to clear so we can stop talking about it and actually get out there? OOPs that is a different thread by Howard and I agree on that as well.

Clear Skies to all,
Marko