20 replies to this topic

[Neptune!]

Hi,

I am going to buy a telescope, but I can't decide if I should buy the 6 inch telescope or the 8 inch dobsonian.

The 6 inch one is a sct, with a focal length of 1500mm.

The 8 inch one is a dob, with a focal length of 1200mm.

 

I would like to look at outer planets and deep sky objects. I observe them in front of my house, but I have to go up the stairs.

 

I'm thinking for the 6" sct, but what do you think is better?

[Alex___B]

8" dob as well. More light = more fun.

[havasman]

I would like to look at outer planets and deep sky objects. I observe them in front of my house, but I have to go up the stairs.

 

Thank you VERY much for including that critical information. The strength of a 6" SCT is in its compact package size and ease of handling. It will do the job of showing you very fine views of the moon, planets and brighter more compact DSO's. It has been said many times that the best scope is the one that will get the most use and that often comes down to ergonomics and the ease of handling. It sounds like that 6" SCT might be a good match for you. Whichever way you go, enjoy your new scope!

[jesco_t]

Totally different beasts. My opinion is that unless you have good arguments in favor of the SCT, go for the 8" Dob. SCTs are great, you get a lot of aperture in a compact and light body. But they're awkward in a lot of other ways. They have a smaller field of view even at the same focal length because they're designed for 1.25" eyepieces. And they good thermal management to get them to cool down and not dew up. They have a weird focuser that changes focal length during during focussing.

[azure1961p]

All things being equal: the 8" newt will always best the C6. Been there.

[azure1961p]

The C6 is far easier taking up the stairs. Pete

[GaryShaw]

The SCT will be far, far more flexible and will keep up with you as your interests and knowledge advance. I had a 13” Dobsonian and ended up feeling that it was an awkward ‘one trick poney’ and donated it to a summer camp. If you can, go for an 8” SCT or, preferably in my view, an 8” F4 or F5 Newtonian. If you get a 6” SCT or Newtonian, I can almost guarantee that you’ll wish it were an 8” within a year. If you’re really interested in planets versus DSOs, the SCT has some advantages, but I’d wager that once you realize that looking at planets offers mainly a limited number of fuzzy planets jiggling all over the place, you’ll see the magic and appeal in the millions of fascinating DSOs within your view.

 

Don’t forget to check our the field of EAA observing which has a very active sub forum here in CN. If you are like so many of us, your skies are getting progressively more light polluted and there’s less and less that can be observed by visual means. Replacing the eyepiece with a simple camera will open up the entire universe for you to observe in ways that visual observing cannot ever come close to. Whichever telescope you get and whichever approach you take to observing, welcome to CN and look to the folks here to help you out as your astronomy interests thrive.

cheers

Gary 

[Spikey131]

An 6” SCT is certainly physically smaller than an. 8” dob.

 

But what mount are you going to put it on?  Mounts adequate for a 6” SCT are not easy to carry up and down stairs.  It would be good if you could see these scope in person.

[Ryley]

With a couple of carrying straps, a 8" Dob OTA isn't hard to handle.  I have 8 steps when taking my 10" dob out when I store it in the house.  I take the base down, then the OTA. Depending on the SCT and the mount it comes with, it could be 2 trips also.

[Tom Stock]

If you want to see deep sky you'll want the 8.   I went down the road of small grab n go scopes so I wouldnt have to haul out my C8 and equatorial mount which was time consuming to set up align and tear down.  I tried a C5 and also an ST80 and quickly realized I made a mistake and was going in the wrong direction. Everything was faint a d tiny.  I sold everything and got a 10" dobsonian. Then a 16" after that.  So much happier. I use the 10" twice a week.

 

The SCT is smaller but depending on the mount you choose setup can be multiple trips up and down the stairs and 20 minutes of assembly and aligning. Then multiple trips up and down when you pack up.

 

Most people can easily carry an 8" dob in assembled, or in two trips,

Edited by Tom Stock, 06 February 2023 - 08:42 PM.

[sevenofnine]

If you can comfortably manage the 8" Dob, it will show you more. Especially in planets and DSO observing. If the 6" SCT is on a go-to mount then you will find objects quickly. There's no perfect one scope. That why hobbyists often have several. Best of luck to you! 

[JoshUrban]

Another vote for the 8" dob.  Tripods are a pain in the neck - and on the door frames.  I'm always slinging dobs around.  I've got an 8" f/8 (so an extra inconvenient one), and it's arguably easier to move than a 100mm f/7 refractor on an EQ mount if they're both in one piece.  

 

  I also consider an 8" dob a more capable instrument.  However, someone already said it:  the best telescope is the one you use!  

[Tom Stock]

Its also very solid and quick to silently move a dob around the sky with nothing but charts and a telrad so consider your mount as well.

 

A go to mount (something you'd probably want for the narrow field of the sct) is a lot of button mashing and standing around waiting for the motors to grind to the next target.  

 

You'll see much more just freely scanning the sky slowly at low power which is not so enjoyable with a goto mount.

 
Alternatively a small sct on a small altaz tripod will likely be much less solid than the dob and more difficult to sweep the sky.

 

Went down that road also and quickly came back to dobsonians.

 

I do like SCTs but dislike the mounts required for them.

Edited by Tom Stock, 07 February 2023 - 09:44 AM.

[miniqtone]

Buy the 8" dob! If it has decent optics and collimation is maintained (easy!) it will be better than the little sct at almost everything. It will yield brighter images, have a wider FOV, show fainter objects, and given decent optics will likely put up a sharper image (based upon my experience as owner of two well collimated SCTs).

 

The dob will, of course, come with it's mounting too. If you choose the SCT you'll have to obtain an appropriate mount (and if so, consider learning the sky for real and the star hopping method of locating objects, and avoid a "go-to" mount).

Edited by miniqtone, 07 February 2023 - 12:01 PM.

[vtornado]

Given good optical quality in each, the dob will give you better views of both planets and dso.  The SCT offers tracking which is good for planets.

 

How many stairs?   Are the stairs steep?  or shallow, with a good railing?

The dob does break down into 2 20 lb pieces. (9 Kg)

 

 You could put the C6 in a carry bag and have one hand carry the bag and the

other tripod.   It depends if you feel safe negoiating the stairs without the hand rail.

 

Depending upon the number of obstructions (trees, buildings) goto may or may not be so easy to use.  I live in a heavily treed area.  It is hard to find alignment stars, and when

I switch targets, I have to pick up the scope to move it an re-align.

 

Also new is the celestron star sense which uses plate solving to help point the scope.

It does not need traditional two star alignment, but you lose tracking.

Edited by vtornado, 07 February 2023 - 05:34 PM.

[Spile]

I have enjoyed observing through my 8” Dobsonian.

[MellonLake]

I always say get the most aperture you can afford and, most importantly, move. Aperture really helps with DSO...and in really dark skies aperture really really helps.

If I was limited toy suburban backyard I would probably only have an 8" telescope. But... because I have access to very dark skies, I always find myself wanting even more aperture. I have seen many hundreds of galaxies and nebulae in my scopes and more aperture means more objects are reachable.

Just my $0.02

Rob

[Tom Stock]

You get almost twice the light gathering ability from an 8" over a 6".  

[Mike Q]

I would suggest hitting up your local astro club and go check them out.  See what you like and what works for you.  Hands on experience is the best indicator of what you should buy. 

[Eddgie]

The C6 is far easier taking up the stairs. Pete

That is kind of a mixed argument. 

The C6 OTA is easier to take up the stairs than the 8" optical tube, but with the C6, you need a tripod and a mount, and the tripod and mount is much harder to move than the C8 and the base. It isn't that the tripod and mount is heavier, it is that it is bulky and it needs to be folded up to move (or at least I would not try to carry a mount and tripod up a stairs without folding it).

 

The Tripod and mount can be broken into sections though, and this does indeed make it much lighter, but now more effort is required because more trips have to be made.

 

An 8" dob OTA only weights between 20 lbs and 22 lbs.  This is not really heavy and a carry strap will make it as easy to move as a decent tripod.

[Eddgie]

If you want to easily locate objects and you want to track at very high powers, you may find the 6" SCT on a Go2 mount to be a better choice.  This is the one area that the SCT will have a great advantage. 

 

You can get Dobsonians with digitial setting circles or the ability to use a phone so that you can locate objects, but if you want to view the moon and you want the scope to track the moon (or planets), then you might want Go2.

 

You can get Dobs with Go2, but here, the weight and size/shape of the base becomes a very important factor.  The motors and electronics are all in the base, and these bases tend to be rather heavy and awkward to carry. The telescope tube tends to be around 20 to 22 lbs for a regular dob, and the use of a carry strap makes it pretty easy to carry.  Dobs are by design, the most stable of telescopes. Even at high power, focusing should be very easy and manually moving the scope should not upset the view. 

 

The C6 will need a mount and tripod.  The tripod can be very light or quite heavy.  Lighter is easier to carry but less stable, heavier is the opposite in both cases.  The issue with a tripod is that to move it, plan on having to collapse it, so the setup and put-away time for the C6 will be longer than it will be for the dob.  Even though people will say the C6 is a great "Grab and Go" telescope, the reality is that except for the physical size of the OTA, it is not as good as an 8" dob in terms of how easy it is to get one outside before the session and inside after the session.

If you go with a light manual alt-azimuth mount for the C6, then you can save considerable weight off of the tripod, but now you don't have tracking. 

 

Just on the merits of performance, the 8" dob is easily superior in every way but unless you get Go2, you will have to manually track when viewing planets.  This is not typically hard if it is a good dob design with good altitude bearings, but some mass produced dobs will not track smoothly by hand without some amount of light modification. 

 

I am not recommending this specific scope, but I will point out that this scope uses a superior altitude bearing than is found on most 8" dobs. The altitude bearing is a key factor in making it easy to track smoothy at high power with a dob. This is because dobs are sensitive to balance. Most use some sort of friction clutch but if you use the clutch, it can make the movement stiffer and less precise. The large half wheel bearing on this model is far better than the friction clutch models. Again, I am not recommending this particular telescope. I am pointing it out as an example of a scope that would have very smooth motion.  If you buy a dob and intend on hand tracking for planets, probably the most important quality of that scope is that it has bearings that allow for very light pressure to track. If planets and the moon are going to be regular subjects, before buying, look at a lot of reviews that talk about the tracking quality, and my own advice is to steer clear of any telescope that is reported to be poor in smooth hand tracking.

 

https://www.highpoin...oBoCk0UQAvD_BwE

 

Full disclosure: I do have a telescope that uses this same large bearing style and of the commercial dobs I have owned, it is the best one for smooth tracking.  The bearing motion is the single most important quality in any size dob. Read reviews and see if a lot of modification was needed to make a given model move smoothly. 

 

My bias is quite high towards the 8" Dobsonian. If you have to have Go2 though, the weight and shape of the base becomes the go/no-go decision point. In this case, the C6 will almost for sure be easier to move. 

Edited by Eddgie, 08 February 2023 - 10:56 AM.