8" MAK OR 10" DOB

[sloz1664]

Please can any one steer me in the right direction. I want to upgrade my Tal 1 to either an 8" mak or a 10" Dob.

Points worth considering are:-

Ease of use, portability, ease of setup and long term use.

As I will be purchasing second hand, total oulay should be similar for both, I think ???

[John]

When you say 8" mak do you mean the 180mm maksutov-cassegrain, the 190mm maksutov-newtonian (both Skywatcher) or do you mean an 8" schmidt-cassegrain ?.

Sorry if that sounds pedantic but they are all very different scopes, and very different from a 10" dobsonian as well.

[sloz1664]

I'm looking at the Tal200k against the Lightbridge 250px

[banner001]

it really comes down to what you want to look at, and if you want to do AP (astro photography) or not?

if you mainly want to look as DSO's (nebulae, galaxies) etc...then get a dob, you need maximum aparture, and dont really need magnification.

if you want to split stars, look at the planets etc, get the mak, if you want to do AP you will need to also get a motorised mount (has to do tracking, you odnt need GoTo...but it can help).

[John]

I've not used a TAL200K so I can't comment on it. I have owned a few dobsonian scopes including a Lightbridge 12" and they perform well and are extremely easy to use.

As scopes they are completely different designs with very different strengths and weaknesses - perhaps you could say more about your observing interests, ie: planetary / lunar, deep sky objects etc ?.

10" dobsonians come up 2nd hand quite often for around £300. TAL200K's are rarely seen on the used market and, when they do come up, sell for quite a bit more than the dobs (like twice as much perhaps ?).

[sloz1664]

Cheers John / Banner001,

I hoped the Tal 200K would be a compromise. Large 8" aperature & still small & compact.

Would like my scope to be general purpose, planets & constellations etc...

[banner001]

Cheers John / Banner001,

I hoped the Tal 200K would be a compromise. Large 8" aperature & still small & compact.

Would like my scope to be general purpose, planets & constellations etc...

there isnt really a 'general purpose' scope, for DSO's i would be looking for a minimum 10" to 12" apperture, you need masses of light to see detail.

small and compact can still have a fairly large focal length, but if you want it to look at the planets you need a decent size apature, 8" is fine, and a long focal length, the TAL will be 2000mm so a 10mm EP gives you 200x which is at the limit for most seeing conditions, you are limited to 400x which is 50xmag per inch of apperture, and you will only get that under excellent seeing conditions. stick it on an HEQ5 and you will be away.

Edit, as you can see here your EP focal length limits your mag...that also works the other way, a tal with a 30mm EP will give you 66x mag, which is quite large, compared to a 10" dob which would probably give you around 40x mag, and as EP's over 30mm are rare and expensive (plus are usually 2" not 1.25") you set your minimum mag to 50-60x.

it would be more helpful to tell us what you have already seen and what you would like to see, but currently cant.

[sloz1664]

Thanks banner001

I recently obtained a Tal 32mm super plossl which is excellent, a steal at £40 as it came with a Tal x2 barlow as well.

I am now more drawn to the Dob as I would like to see more dso's.

Although, would I be compromised by not going to a dark site. I am lucky I live next to a lake where light pollution is not that excessive.

cheers

Steve

[swamp thing]

Hi Steve

A dark sky is THE most important thing for observing any diffuse objects with low surface brightness.

So any scope will be compromised by LP.

The good thing about any Dob is it's portability to allow you to transport it to one.

Although TBH the truss tube Dobs under 12" are really more agro than help. Too much faffing around with trusses and shrouds.

IMO your much better off with a solid tube Dob. Specially if set up time is an issue.

A solid tube is ready to observe as quick as you put it on the ground and collimate. 5 mins tops.

I have not used the Tal but they have a good name. It looks like a good planetary scope.

However I would say that for Deep sky visual observing a Dob is the scope to own.

Regards Steve

[nightfisher]

if you have good flat ground to set up the 10" dob and low light pollution, then it ill be a good scope, providing you dont want to do imaging, if you want to be mobile then the 200k would be a much better bet

[Ad Astra]

These are so different (except for aperture) that it is hard to compare them.

Maks are relatively long focal lengths, narrow field, high magnification and resolution. Excellent for planetary, lunar, double stars and clusters - rather poor choice for DSO's. This is a specialized scope, and does what it does quite well - but away from its specialty, it is a weaker choice.

A Dob is excellent for DSO's, but larger center obstruction, collimation issues (especially as larger scopes tend to have faster primary mirrors) etc. lower contrast and resolution. Just about the mirror opposite of the Mak.

An SCT is a compromise between the two, but the real question, is what kind of observing you like to do. I love planetary and lunar observing, and I love Maks and long refractors, but they do a relatively poor job on DSO's, especially visually.

You need to maybe join the local astro club and see if you can try both kinds of instrument, see what kind of observing you enjoy before committing to a scope. If I had to recommend just one for you, I'd say go for the dob:

1) Much cheaper - more $$$ left for accessories & EP's

2) More versatile - it does a better job on planets than a Mak does on DSO's

Hope that helps,

Dan

[dark star]

I have a Russian 6 inch Intes MK66 Mak and have found it excellent on DSO's, I have seen M81, M82, M57, M13 etc. and it is great on planets. With a 40mm eyepiece the FOV is big enough for many targets.

If you have the money I would suggest a Russian Mak such as Intes Micro, these are Rumak Mak designs which are different to the Skywatcher ones.

However, nothing beats aperture for Deepsky and I am planning to get a 10 or 12 inch Dobsonian at some point.

I guess what I am saying is that Maks can be be very good for Deepsky, but a 10 or 12 inch telescope will be even better! Maks of this size are too expensive and heavy.

In an ideal world I would get a 7 or 8 inch Mak and a 12 inch Dobsonian, maybe when I win the lottery! I would also be very happy to have a Tal 200k.

[banner001]

as others have mentioned, if you live in europe (i.e. we dont all have 10' wide cars ) a 10" dob should fit across your back seat, a 12" dob you would need to fold the seats down and you will have a harder time keeping it from banging into things. A large dob or 12" upwards needs to be a truss type if you need to transport it, if not a solid tube is better, but the largest solid tube i have seen is an OOUK 14" dob...dont know if there are bigger solid tubes, maybe some carbon fibre ones?

as for dark skies, yes a proper dark sky site will always outperform your back garden, but as long as you have minimal skyglow, and you can visually see to mag 4, maybe mag 4.5 - mag 5 then you will be ok, remember to try and only view above 30 degrees from the horizon (to minimise the amount of atmosphere you need to look through)

[cotterless45]

I prefer 8" Dob over 10". It's easier to move and gives very similar views in light pollution.You won't be needing high magnification to chase DSOs , just some decent aperture.

[sloz1664]

Thanks to all,

I now have to consider what I want to do in the future. I have an inkling it will be dso's. I have the Messier checklist to cosider.

cheers

Steve

[Foton Finder]

Hey Sloz1664

I agree with most of the comments posted so far. If you go for the DOB, you'll have more money left for additional eyepieces (can't have too many!), filters and other accessories. These really are apples and peaches, so comparing them is tough.

The 8" Maksutov is advertized as f/8.7, while the DOB will be a lot shorter FL (though not as compact). If the MAK has good optics, it will actually be quite useful for globulars, most planetary nebulae, smaller open clusters, and many small'ish galaxies, but won't give you the big, wide FOV needed to see things like the Leo Triplet (M-65/65/NGC 3628) in one eyepiece view.

Now I'll differ a little from my fellow posters.... if you have lots of light pollution, a big aperture doesn't always help -- the sky glow gets brighter with more aperture, too. Within reason, a little higher focal ratio is often helpful in separating the brighter DSO's from the background noise of light pollution. Once you get good at finding things, a little more magnification can really help the view, so a short focus DOB is not always better for "deep sky" -- it depends on the type of object. While both are portable, the DOB is meant to be toted around, and a Maksutov might be better for a fixed pier.

Bottom line is, get the DOB and buy some accessories with the leftover $$$, and if you ever change your mind and want to change, a good DOB is very easy to sell. You will have TONS of fun with that new 'scope!

Clear skies,

[Ags]

I agree with foton finder, addind aperture with light pollutions means you have to go to higher magnifications to get a pleasingly dark background. So the mak is not at such a disadvantage.

But a mak with an 8.7 focal ratio is a bit unusual - it will have a huge central obstruction - probably bigger than the newt's. So it would not offer the high contrast expected of a mak. A mak should have an f ratio of 12 or more to give good contrast.

[John]

Just for clarity, the TAL200K is not a Maksutov-Cassegrain, it's a Klevtzov-Cassegrain which is a rather different design.

Here is a short review and some links to further information on them:

TAL 200K telescope

FWIW I agree with the recommendations to go with an 8" or 10" dobsonian. While they have their fans, I understand that the Klevtzov-Cassegrains can be difficult to collimate and are a rather specialized scope design.

[Ags]

Ah... I thought the f ratio was odd. My bad for not reading the whole thread carefully, but is a bit difficult with tapatalk.

But I think my point about the size of the central obstruction is still valid.

[John]

But I think my point about the size of the central obstruction is still valid.

Yep - the Klevtzov's do seem to have a largish secondary

I believe they perform very well if properly collimated though (but then so do most scopes !).

[nightfisher]

i heard that the klev, once collimated is unlikely to shift, unless you play footie with it (not recommended)

[AndyH]

i heard that the klev, once collimated is unlikely to shift, unless you play footie with it (not recommended)

Hehehe...you heard correctly. It uses M6-ish BOLTS for collimation purposes. It's no more difficult to align the optics on a Klev, than on a Intes styley Rumak Mak IMHO. Perhaps easier.

On my 2001 model, the central obstruction is 72mm, which makes it about 36%. A wee bit bigger than an SCT, but again in my opinion, the views are tighter in a Klev. Not bashing SCT's. Great scopes.

Unless you're a DSO junkie, 8" of glass n mirror is a nice size and will let you see most everything rather well.

I like the compact size of a cassegrain. It suits ME just fine and you don't need a humungous mount to carry the ota. I've used the 200K on a W.O.(swiss build) EZTouch and my teeny helix-mfg grab n go alt/az to good effect.

Ags - you are kind of right. Modern 200K's are F8.7, but I doubt there are many of them in the UK, even although they have been manufactured at that focal ratio since 2006. I have a sneaking suspicion that 'Kaptain Klevtsov's' MAY be one.

I don't like to get bogged down by talk of this scope is better than that scope. Even the smallest will give you wonderful, mind blowing views. Who needs a big chair with spinning wheels and dials to go back in time? When you think of it, what is your scope, but a time machine? Mind blowing, man.

Jeez I'm showing my hippy tendancies.. . Now where did I put that Mamas and Papas disk??

:)Andy.