Dobs are often recommended, but what about...

[JohnBatibas]

Hi,
I'm brand new to both this site and to stargazing. It's great that these types of forums exist!
I'm in the process of getting my first real telescope and scanning the pages of this forum the Dobsonian's seem the most recommended. I looked at this (http://cdn.ozscopes.com.au/media/images/ozscopes/guides/telescopes-and-uses_.png) guide and decided that I wanted to be able to see objects beyond our solar system as a little more than a bright fuzz. At this point I realised that unless I had several thousand $$'s at my disposal I'd be hard pressed to find something within my price range ~ $600. There was though a telescope that was reasonably priced and, based on the above guide, would satisfy my "needs".
Would someone with some experience mind giving me some input as to whether or not the below scope would allow me to see DSO with a relative degree of clarity - relative to an 8" or 10" dob?
Thank you in advance!!:)
Celestron Nexstar 90 SLT MAK

[mswhin63]

Comparatively the 10" will give you the best display, the next will be the 8" finally the 90SLT the last. Why is because of the aperture the bigger the aperture the more light is capture and directed to the eye.

The only advantage for the MAK is portability and goto if you decide to get the non goto DOB.

The focal length of the MAK is similar to the 10" so the 10" will way out perform the MAK in just about everything.

[mental4astro]

Hi John,

That chart you've linked to has me confused and feeling it is miss leading. It leaves out a lot of information to have their claims make sense, and it implies what to me look like outright lies. It implies that you will see more with a 3.5" Mak than a 15" reflector. That is a just untrue as Malcom explained.

The only thing I can recommend is that you get to a local star party or astro club meeting and see what all these telescopes look like and how they work. There you will see the inexpensive to the outrageously expensive, and be able to gauge for yourself what best suits you.

Have a look in the Star Parties forum for star parties closest to you. There are two usually listed there for around Sydney at Mangrove Mountain (the Pony Club) and Katoomba (Katoomba Airfield). Sometimes others in Randwick or at Macquarie Uni. Also look in the "Our Community" heading in the left margin for astro club listings.

[mswhin63]

Bit of a marketing ploy, because it allows them to make money on making sure that a beginning package is used so that when a person gains interest and wishes to make the change then another package is need to be made. By creating a label Beginner, General and Advanced is a misnomer.

I agree with Alexander, in most cases advanced astronomers use more than one scope as they all perform different tasks. I have the 12" DOB bought under the beginner label but lucky as it is a good scope, I use this for good medium angle viewing and along with a 3 x Barlow is good for some close up work.

I also have a 80mm APO refractor which is really cool for wide-field. I have a pair of Bino for other views and I intend to get a Mak or Cass for some really narrow field views.

So it all relative. Alexander suggestion to get involved with a star party or even a club is a really great way to get fully knowledgeable.

[barx1963]

I can sort of get what they are getting at with this chart, but it is a bit misleading as it implies that a 3.5" Mak Cas gives higher resolution than a 15" dob, which is quite simply crap of the highest order!
A 90mm Mak like the one you mention certainly portable, buts its relatively tiny aperture will make almost all DSOs invisible except in really dark skies, and even then will still be very limited.
As you say you want to see DSO as more than faint blobs there is only one solution and that is aperture and more aperture. As you have a constrained budget of $600 a dob is the ONLY way to go.
Bintels 10" solid tube is $699 and if you shop around (say Andrews) you may get similar a bit cheaper (but I can highly recommend Bintels customer service).
A 10" will give a fair bit of detail in DSOs for the brighter ones, M42, Eta Car, the Trantula Neb, Omega Cen and the brighter Messiers will all look spectacular through this scope.

My 2 cents worth!

Malcolm

[dannat]

A 90 mak will only let you see brightest dso's, an 8" dob mounted reflector will let you see much more, however if you live in a city apartment a 8" may be Impractical ..I have a 4" refractor (which is a good city choice IMO on an altaz mount), I have had 12" & 8" reflector on dob mount & they just not suit me

Have you had ny viewing exp?

[mswhin63]

Not to belittle the MAK too much, it is great for Planetary and moon. I know that my 12" can be a bit over-powering occasionally. It is all relative!

[jjjnettie]

When it comes to scopes, size does matter. :)
You want as much light as possible to reach your eye. And a 90mm Mak just won't cut it for the fainter stuff.
An 8" Dobbie is a great scope. It breaks into 2 pieces and will fit across the back seat of most cars if you decide to hit the road looking for darker skies.

[yohanan]

Hi John

I am also brand new to this whole stargazing enterprise. And, again like you, have prowled the forums and found some very interesting posts. In the process I have learnt something of the basics.

I respond however as I too am looking at Celestron Nexstar for much the same reasons - I am drawn to deep space (1).

However, my problem is that I live at Maryborough in Queensland and as anyone from up this way knows - moisture is a big problem. My nearest neightbour is 5 k away and there is no traffic as I live beside a river near its mouth and where full moon creates so much light that one needs dark glasses to go about at night. ;)

But the humidity at this time of year is a killer. Mould is an ever present problem (2).

Thus, any telescope I might consider has to be fully enclosed and compact enough to be placed in a warming box to stop any crows feet growing.

Personally, I'm looking at the 5/6SE

The Celestron range seems to satisfy both these requirements (1) & (2).

As others have suggested, size does matter. I would love to go bigger but the budget does not stretch that far.

I have not made any decision and probably won't for some time as I check out other telescopes and speak to those who have more knowledge on such matters.

[Allan_L]

I'll also try yo put it simply, in a way you can apply to other scopes.

The ability to see DSOs with greater degrees of clarity depends on two main factors tha t you can control (there are other factors that you cannot control as well, but more about that later)
Magnification
Quantity of Light gathered.

Magnification is a mathematical relationship between the Focal Length of the scope and the number on the eyepiece. Mag = Focal length / eyepiece.

However, the highest possible magnification you can reasonably expect to be able focus on is generally said to be two times the aperture (in mm)
(And this drops as the environment conditions deteriorate)

So you can see that the 90mm SLT could at best deliver a magnification of 180 times, where the 10 inch DOB (250mm) could get you up near 500 times magnification.

Now admitedly you don't use that sort of magnification with DSO's generally, but the principle is that you will get more light gathering at any magnification and the more light you get the more likely you are to see your DSO.

As previously said, you really should come to an observing night and you will clearly see what I mean. We have a good range at the Pony Club, its friendly informative informal and FREE.

Hope to see you there.

[JohnBatibas]

I appreciate the time taken to respond to my question!!!! Hopefully I'll get myself to one of these star parties!
Thanks again!
:thanx:

[jjjnettie]

Make the effort to go John.
You'll find everyone is more than happy to show off their gear and share their knowledge to anyone who is willing to stand still long enough to listen. LOL

[Allan_L]

:lol: You got that right jjj ;)

[Steffen]

I'd like to add (in the defense of Maks) that due to their inherent higher contrast they perform better than they "should" – aperture-wise. For example, I have yet to see something in an 8" Dob that I couldn't see in a 6" Mak. And whatever it is you're looking at, it looks better in the 6" Mak than in the 8" Dob (less washed out and contrastier). The flip side is that the Mak is about 4 times as expensive as the Dob (considering the two particular scopes I've used, anyway).

Comparing an 8" or 10" Dob with a 90mm Mak is silly, of course.

Cheers
Steffen.