5"/6" refractor suggestions please

[Relpet]

I've just taken advantage of FLO's sale price on a Celestron AVX mount which I can use with a couple of tubes I have already, 6" Newt and 4" Mak, but I would really like to get hold of a refractor at an affordable price (Achro - obviously) which will give me good observing with reasonable AP opportunities.  There are a couple in the Bresser Messier range, which have had good reviews, but not much user input.  There may be others.  If anyone has any sensible suggestions I'd love to hear them.  Thanks as always.

 

[glynnlondon]

Nick ( cotterless 45 ) has/had a celestron c6r with which he had some nice results in his ongoing hunt for those elusive double stars.

Rother valley optics sell the Ota for £495.

Might be worth considering tho not too sure about achros and ap. Others will know better than I.

[Rick_It]

A 150/1200 is quite a big scope for a Celestron AVX for visual; you can forget AP with it. Moreover, it adds almost nothing to your 6" Newton.

If you want AP (strictly narrowband), you can buy the 127/635, which is a petzval. However at 7.7kg you are at the upper limit of the AVX photo capacity, so you will struggle. For the same price you can buy an 80mm ED, which is the perfect match for AP on AVX.

If you want visual, get a long focus refractor for planetary / double star. The 4" Mak, with 35% central obstruction, is absolutely not as good as a good long focus 4" achro. Bresser should come out in a month with a new 100/1350, i.e. a 4" f13.5 at a very reasonable price. I would wait for it.

[Peter Drew]

I can't see what a 5"/6" achromat is going to significantly add to your present lineup other than weight. The 6" Newtonian and 4" Maksutov should be better for AP and neither will suffer from CA.   

[Relpet]

25 minutes ago, Peter Drew said:

I can't see what a 5"/6" achromat is going to significantly add to your present lineup other than weight. The 6" Newtonian and 4" Maksutov should be better for AP and neither will suffer from CA.   

Thanks, Peter,

For AP it would seem that the 6" SW 150p-ds I have already will take me to the limit of any ambitions I might have in that field.  It is on a weaker mount at present so should benefit from the AVX.  Having read so much about the observation quality of a refractor being so much brighter, crisper, revealing and generally superior to reflected observations it seemed the way to go.  Even with my 8" Dob under clear French skies I have yet to see the GRS on Jupiter, the snow caps on Mars or a clear view of the Cassini division of Saturn.

If I am mistaken in expecting better observing then perhaps I'll save the money; otherwise I should maybe amend my enquiry to concentrate on the best value for observing only with an achro.

[Dave In Vermont]

Hi 'Fang,'

I have a 127mm F/9.3 Meade achro-Refractor from 2003, which is likely quite similar to the Bresser offering quaility-wise. I also have a 200mm reflector, and 150mm Maksutov. That refractor does rather leave the reflector and the Mak in the weeds in terms of planets and sharp views thereof.

The views I've had of Jupiter were breath-taking! A transit of the Moons were perfect, jet-black dots projected on the cloud-belts. The snow-caps of Mars - both of them at once - were wonderful little white tufts of cotton! "SHARP" was the operative word. I know this should be matched by the Mak, SCT, 200mm reflector - but this was simply amazing!

Though I know I should be dissuaded by the logic that other scope-types should be as good (and less money) than an achro (leave alone APO's, etc.) - but I am very, very happy I bought this beast.

So much for logic. Magic works sometimes!

Dave

[DaveS]

A 5" achro would need a much sturdier mount than an AXV, and would be NB only. It's not just the mass but the moment arm you have to consider, a 5" (Even more so a 6") 'frac at f/7-8 is a long beast.

I image with a 5" (Well 130mm) 'frac, but it's on a DDM60, several levels higher than an AVX.

[Moonshane]

A used 120mm Skywatcher ED

[mikeDnight]

The SkyWatcher ED's are the way to go if you want to improve on visual performance. May be if you use your reflector for AP as Peter suggested and settle down with a 100mm, or if you can afford it a 120mm ED from SkyWatcher, you'll have all you need. They will certainly give you the razor sharp planetary views youre after.

Don't let aperture be the determining factor! A SW 100mm ED will massively out perform an off the shelf 5" or 6" achromat on the Moon and Planets.

Mike

[Paul73]

I'm no imager. But visually, the SWED120 is great. Mine gave me my best ever Venus views last night. 

The GRS & shadow transits will be glorious in this!  But, when it comes to the Fuzzies, aperture matters!! And, yes, we are talking more than 6" here!

Paul

[Relpet]

1 hour ago, DaveS said:

A 5" achro would need a much sturdier mount than an AXV, and would be NB only. It's not just the mass but the moment arm you have to consider, a 5" (Even more so a 6") 'frac at f/7-8 is a long beast.

I image with a 5" (Well 130mm) 'frac, but it's on a DDM60, several levels higher than an AVX.

Thanks, Dave,

This is the one I had in mind

http://www.bresser.de/en/Astronomy/Bresser-Messier-AR-152S-760-Hexafoc-Optical-Tube.html

Bresser sell this mounted on their strongest own brand mount which is less sturdy than the AVX, I believe.  There is a 5" short tube version and each can come with longer tubes.  I have not seen a bad review of any from this brand, which may be based on earlier ES models.  Apart from the optics the focuser seems ideal for 2" EPs and there are other fringe benefits (and I don't mean chromatic!).

Peter

[DaveS]

Ah, OK.

That might be OK on an AVX *for visual* but I'd still be wary of trying AP on that mount with that OTA.

One thing to be aware of, because it's a modified Petzval design, don't try solar without a front filter as you'll wreck the rear group if you try to use just a Hershel wedge.

[Relpet]

58 minutes ago, Paul73 said:

I'm no imager. But visually, the SWED120 is great. Mine gave me my best ever Venus views last night. 

The GRS & shadow transits will be glorious in this!  But, when it comes to the Fuzzies, aperture matters!! And, yes, we are talking more than 6" here!

Paul

Thanks, Paul.  I will check out the ED120

[John]

The AVX mount handled my 130mm F/9.2 triplet apochromat quite well for visual observing. The scope is about the same size and weight as the Skywatcher Evostar 150mm F/8. It would not be stable enough for imaging though. The AVX was pretty much rock steady when I put my ED120 on it but I'm not an imager so rock steady to me might not be good enough for an imager.

 

[Relpet]

Is this the one you chaps were recommending?

https://www.firstlightoptics.com/equinox/skywatcher-equinox-120-apo-pro-ota.html

If so I gulped, swallowed hard and reached for the tranquilisers.  Way out of my price range, I'm afraid. But thanks for even thinking I could run to it.

[happy-kat]

Astroavani has shared recently some great images from his 127mm f6.5 refractor in the lunar forum. It's an explorer scientific acro.

[Paul73]

 

This was the beastie https://www.firstlightoptics.com/pro-series/skywatcher-evostar-120ed-ds-pro-outfit.html.

Ok. It isn't much cheaper, but they do come up 2nd hand for £700 ish. Need to make sure that it includes a decent diagonal and the dovetail bar. Although the Equinox does look very fetching in the Black & Chrome.

Paul

[mikeDnight]

2 hours ago, Relpet said:

Is this the one you chaps were recommending?

https://www.firstlightoptics.com/equinox/skywatcher-equinox-120-apo-pro-ota.html

If so I gulped, swallowed hard and reached for the tranquilisers.  Way out of my price range, I'm afraid. But thanks for even thinking I could run to it.

The SW Pro version uses the same superb optics as the Equinox version and you get a dielectric diagonal with it. The pro is beautifully made and is cheaper than the Equinox.

They do come up second hand from time to time on Astro Buy & Sell. 

If the 120 is too costly you could consider the 100 ED Pro.

Mike

[Relpet]

9 hours ago, happy-kat said:

Astroavani has shared recently some great images from his 127mm f6.5 refractor in the lunar forum. It's an explorer scientific acro.

Thanks for that.  I'll take a look at the pictures.  It's certainly a more affordable solution.

[Relpet]

9 hours ago, Paul73 said:

 

This was the beastie https://www.firstlightoptics.com/pro-series/skywatcher-evostar-120ed-ds-pro-outfit.html.

Ok. It isn't much cheaper, but they do come up 2nd hand for £700 ish. Need to make sure that it includes a decent diagonal and the dovetail bar. Although the Equinox does look very fetching in the Black & Chrome.

Paul

Thanks, Paul.  I'll keep a look out.  I'm not in a hurry.

[Relpet]

10 hours ago, happy-kat said:

Astroavani has shared recently some great images from his 127mm f6.5 refractor in the lunar forum. It's an explorer scientific acro.

Well, I've taken a look at the pictures - which were superb - but I've also checked user reviews submitted by, predominantly, experienced astronomers in the USA.  Without exception they all comment on the astonishing lack of CA.  I've not been able to trace pictures taken by any other users but all the reviews were from people impressed by the quality of visual observation.  CA seems to be noticeable with Jupiter but not much else unless you spend more time looking for the CA than at the object itself.  Though it is more expensive than the Bresser Messier 127s/760 it looks as if it could be money well spent.  Thank you.

 

[Relpet]

Thanks to everyone,

I have truly appreciated all the advice here and will seize whatever opportunity presents itself first in the light of that advice, with practical, affordable quality as the guiding principle.

[spaceboy]

21 hours ago, Relpet said:

 Even with my 8" Dob under clear French skies I have yet to see the GRS on Jupiter, the snow caps on Mars or a clear view of the Cassini division of Saturn.

If I am mistaken in expecting better observing then perhaps I'll save the money; otherwise I should maybe amend my enquiry to concentrate on the best value for observing only with an achro.

I'm surprised no-one else picked up on this.

You would be better saving your money!!

I much prefer refractors over Newtonians but due to cost you are very much restricted on aperture. My guess is your collimation is WAY out on your 8" dob or your just not catching the planets at right angle or time of night to see the above mentioned features. Even a 6" achro would struggle to top the a well cooled and collimated 8" dob.

IMHO ED Refractors do against similar apertures offer a far better quality of views as far as contrast and all-round tidiness (for want of a better word). Double stars are such a pleasure and the moon a delight but ED glass comes at a cost. Achromatic refractors are no slouch but CA can rob brighter stars and planets of contrast so you'd really be no better off than what you already have with the MAK. The moon isn't too bad in an achro depending on how illuminated it is and an ND filter will often tidy up CA significantly while cutting out the glare but many people prefer not using moon filters as the views tend to dim quickly as you up the magnification.

Personally I'd save your money as your really not going to top what you already have unless your prepared to side towards ED glass.

[nightfisher]

On 3/3/2017 at 01:38, Relpet said:

I've just taken advantage of FLO's sale price on a Celestron AVX mount which I can use with a couple of tubes I have already, 6" Newt and 4" Mak, but I would really like to get hold of a refractor at an affordable price (Achro - obviously) which will give me good observing with reasonable AP opportunities.  There are a couple in the Bresser Messier range, which have had good reviews, but not much user input.  There may be others.  If anyone has any sensible suggestions I'd love to hear them.  Thanks as always.

 

Lets try and get you where you want to be, so back to the start, you have a nice new mount, a 102 Maksutov and a 150p ds, plus an 8" dobsonian, the Maksutov is a very good Luna scope both visual and imaging, i have a 102 and only taken one Luna image so far but its turned out to be one of my best yet, this scope will also be pretty good imaging planets.

You have the 150p.ds, pretty good for deep sky imaging, and the 8" dob is going to be very good visual scope, as spaceboy says make sure collimation is pretty well spot on, the GRS can be a tricky one to see, most of the time its out of sight and seeing conditions need to be pretty good.

If you rather fancy getting a frac a 120ED is a very good scope, but its a big old lump and you may find you dont use it so much due to the size of it.

I think its best if you clearly outline just what you would use a new frac for then maybe we can offer better help more tailored to you needs

[Relpet]

26 minutes ago, spaceboy said:

I'm surprised no-one else picked up on this.

You would be better saving your money!!

I much prefer refractors over Newtonians but due to cost you are very much restricted on aperture. My guess is your collimation is WAY out on your 8" dob or your just not catching the planets at right angle or time of night to see the above mentioned features. Even a 6" achro would struggle to top the a well cooled and collimated 8" dob.

IMHO ED Refractors do against similar apertures offer a far better quality of views as far as contrast and all-round tidiness (for want of a better word). Double stars are such a pleasure and the moon a delight but ED glass comes at a cost. Achromatic refractors are no slouch but CA can rob brighter stars and planets of contrast so you'd really be no better off than what you already have with the MAK. The moon isn't too bad in an achro depending on how illuminated it is and an ND filter will often tidy up CA significantly while cutting out the glare but many people prefer not using moon filters as the views tend to dim quickly as you up the magnification.

Personally I'd save your money as your really not going to top what you already have unless your prepared to side towards ED glass.

That's the kind of informed comment I have come to expect from SGL and it is pertinent.  At one point last autumn I left the tube of the Dob open in the barn and next time I went to use it, some weeks later, found dead spiders and all sorts littered over the main mirror.  After stripping it down, cleaning and reassembling I carried out what was probably the most thorough collimation the Dob had ever been treated to.  Then the weather hit and we went for weeks without clear skies and the planets, on those odd occasions when they might have been seen, had gone some place else.  My highest magnification EP was 5mm, which was probably a step too far.  I was advised early on that 6mm was probably the most likely to give the best result.  I have now invested in a 6mm.  However, most of my gear is in France and I'm in England until 28th March, so I have to wait until then before I can see what difference this makes.  If the improved collimation, correct eyepiece, helpful juxtaposition of planets, clear skies do indeed let me see what I want to see with the Dob then maybe an 80mm APO will be enough of a refractor.  Thanks for the observation.