Would like a 6" Frac - but which one ?

[sweatysock]

Evening all !

Need some advice please from you clued up folks on refractors...

Currently have an Celestron 8SE OTA but mounted on a CGEM that came my way ...  Also have a 16" Dob for fainter objects, and starting to get drawn to DSO.

I am now interested in what a 6" frac could do for me...  I dont fancy the APO or even ED route, as I dont want to start throwing money at this ( yet ! ) , so have narrowed it down to these 4 choices based on various bits of Googling  :

Bresser AR-152L/1200

Skywatcher Evostar 150

Explore Scientific AR152

Starwave 152 V2 ( only because its pretty )

You can see my choices have quite a big range between £430 and £830...  I mainly do visual but there is a chance this new setup will get me to dust off my old webcams and get back into trying to capture images.  I am concerned about CA though, which "should" push me towards the Evostar at f/8 right ? But the Bresser is just behind at f/7.9 yet is over £100 cheaper - could get a Baader semi APO for that.

The ES seems to have the better all round "package" than the Bresser and the SW, so thats also interesting - but then we get to the Altair which seems to receive great reviews and somehow reduced CA at f/5.9!  But almost 2X the price of the Bresser -  is the view really twice as good ? Any advice appreciated on what I should be concentrating on here as I now cant see the wood for the trees...

Cheers in advance !

 

[Dude_with_the_tube]

if CA is off your main concern then neither of your mentioned instruments will suit you,and trust me,Altair at F5.9 will have more CA then bresser or Ex Sc or Skywatcher purely because its shorter focal length.I am a refractor fan and had various refractors starting from F7 up to F15.Achromats will have CA unless they go really long focal ratio.Unfortunately to get rid of CA in a refractor its either get a very long focal ratio one and then fight the issues with mounting it due to OTA being stupendlously long or go down ED or APo route. I went down ED route and currently i am in a process of building a new ED telescope(quite a large instrument).

Looking that you already have a 8" SCT why on earth you would need a 6" achro? your 8" will show you the same detail (roughly) anyways.To really get an improvement over your 8 " sct it will have to be a minimum of an 5" ED anything smaller will not really be a massive or no improvement.Also your 8" will be easier to mount and handle then that long F ratio Achro.

John will chip in for sure,but he had a 6" F10 achro and he struggled to get it mounted,I know a few guys who have a 6" F15 and boy that thing is darn long and dog to mount on your own.

if its a point of just getting a hang of how refractor works or shows planetary,get a skywatcher 100 ED,they go for about 300 quid s/h and will be a stunning instrument for visual and also for a bit of AP and will not brake your bank.

P.S. those 6" short focal ratio refractors are not meant for planetary,but for a wide field observations (rich field) due to CA.

[John]

I had a 6" F/12 achromat for a while but as the Dude says, getting a suitable mount for it was really challenging. The F/12 was a good one (Istar) but CA was still visible around bright stars and the lunar limb. I think you need something like an F/18 in the 6" aperture to be pretty much "CA free" with an achromat.

Of the ones you list, I've owned a few of the 150 F/8's and a Meade 152 / F/7.9 which I believe is the same as the Bresser you list. They all showed CA as you would expect but it seems to depend on the individual as to how bothersome they find it.

The 152 / F.5.9 Altair and the other incarnations of it does reportely show less CA than the Bresser / Skywatcher 6" F/8's which is quite an achievement. I don't think anyone is reporting that it's on par with an ED doublet though.

I suspect that the overall optical quality of the 152 F/5.9's is more consistently better than the Bresser / Skywatcher F/8's in terms of spherical aberration as I found the latter rather variable from the samples that I owned.

In all honesty I'd not pay those sort of prices for a F/6-F/8 6" achromat I think. A used one for a £200 or less (which is what I managed to pick up) is fun as long as you have a suitable mount but £600-£800 will get you a used ED120 which would be my preference (and was in the end).

I don't know much about the ES 152 F/6.5 but Ed Ting tested it along with a 152 F/5.9 a little while back:

http://www.scopereviews.com/page1y.html

 

[Peter Drew]

I have long and short 6" refractors and a 8"SE, if it wasn't for my solar interest I'd have just the 8SE.   

[cloudsweeper]

Larger aperture fracs have long-ish focal lengths which is why I went for the ST120 to complement my 8SE - I really like the widefield views it gives (f is only 600mm), and it is a manageable size.

As for CA, I've only noticed it on the lunar perimeter and planets, but if I want a session with them I use the 8SE!

So I would recommend a 4 or 5 inch frac.

Doug.

[Moonshane]

What type of object are you looking at mainly with this scope? Maybe i misunderstand but you seem to want a reasonable aperture with a short focal length and ca free. For visual,  ca only really matters on bright (generally solar system) objects and your spec suggests planetary Is not prime.

Your criteria seem best served by a 6" f5 newt to my mind especially given your other scopes.

[michael.h.f.wilkinson]

I agree that next to your two scopes a short F/L refractor would be best. On planetary and lunar a properly collimated 8" SCT will do better than a 6" achromat in my experience. It is also WAY more manageable. I do not have a big Dobsonian (I will get one one day), but I do have a little APM 80mm F/6 triplet apochromat, which serves as a brilliant wide-field scope (and for solar). Some wide-field instrument, like an ST102 or ST120 may well serve you better than a 6" achromat

[xtreemchaos]

ive had the bresser AR150l, lovely scope, giant in size and weight, but do give great views with a bit of Ca, Ca dosnt bother me, its like diffraction spikes with newts there just part of using the scope and if you like large doublet fracs you learn to live with it, downside with the AR150 is weight its built like a tank, i had mine on a eq6 and at times the mount couldnt take it like if there was a bit of wind because big fracs dont hafe catch the wind. i sold it after about 18 months becase of the weight, i have a gamy knee and had to cut down on carrying heavy stuff, i allready had the smaller AR127L and i find it much more manageable, still great views with the 127. good luck and clear skys charl.

[Commanderfish]

I have the Altair Starwave 152.  It is fantastic for visual, especially DSOs.   I keep meaning to post a review.  As far as CA is concerned, it is pure witchcraft.  It has less CA than my SW120 Evostar F8.3 had.  Don't ask me how, it's impossible.  It just does.  (Actually it's something to do with focusing red and blue wavelengths instead of red and green, plus better coatings = witchcraft).

I have no doubt you'd enjoy it if you got one.  They never seen to come up second hand, which is quite telling. PS there is no optical difference between the V1 and V2 other than colour.  

[Sirius Starwatcher]

2 hours ago, Commanderfish said:

I have the Altair Starwave 152.  It is fantastic for visual, especially DSOs.   I keep meaning to post a review.  As far as CA is concerned, it is pure witchcraft.  It has less CA than my SW120 Evostar F8.3 had.  Don't ask me how, it's impossible.  It just does.  (Actually it's something to do with focusing red and blue wavelengths instead of red and green, plus better coatings = witchcraft).

I have no doubt you'd enjoy it if you got one.  They never seen to come up second hand, which is quite telling. PS there is no optical difference between the V1 and V2 other than colour.  

Yes Please Commander, Post your review ASAP please as I am after as much info as I can before I part  with the  leccy sorry telescope money .