130mm to 140mm refractor

[GavStar]

I've got a 100mm refractor (or two ?) but have been thinking for a while about stepping up to say 130mm to 140mm which I think is the max for me given weight etc. I'm visual only and so far have only used doublets.

The only APO doublet available at this size is the newish APM 140 f7. However I'd really like this scope to be a keeper and am a bit concerned about the f7 introducing some colour. The alternative is a triplet such as tec 140mm, cff 132mm or APM 130mm f9.25. But these seem to have longer cool down, heavier, and maybe trickier to set up and mount. I was hoping for a tak 130mm doublet but this doesn't seem on the cards in the near future.

So I'm unsure which way to go (or indeed should I stick with my 100mm since the jump to 130 to 140mm would not have much impact for visual?) Would the tec retain value the best if tak do release a larger doublet?

Any views would be appreciated?

Thanks

Gavin

[Chris]

I'll admit this is beyond my whelm of experience when it comes to premium refractors, but I think it would help to know what mount you plan on using?

[GavStar]

I've got a T-Rex alt az mount which I think should be good for refractors up to 140mm in size

[John]

My TMB / LZOS 130 F/9.25 takes around 40 mins or so to cool. Not excessive for a triplet I think.

I understand that LZOS production is being moved away from scope optics so just 9 more will be made taking the total run to 114 units, according to Markus Ludes of APM. Seriously good optics in these scopes, believe me. The best I've ever viewed with - as good as the Tak FC-100DL, maybe even a touch better.

The T-Rex would handle one fine with the right tripod under it.

I did consider the APM 140mm F/7 and might have bought one if the LZOS 130 had not come along.

Doublets larger than 120mm are a bit thin on the ground I agree. I guess you do risk a touch of CA on the brightest objects with a larger doublet ?.

 

Edited December 21, 2016 by John

[DaveS]

And what's your realistic budget?

My Photoline 130 f/7 triplet cost me 2400 Euro, while the CFF 132 f/6.9 was 5600 Euro. I very nearly went for the CFF but in the end, and with big bills looming, couldn't justify the expense.

I think that oiled triplets cool down faster than air-spaced, and also, something I didn't take into consideration, an oiled triplet won't get condensation between the elements, which is something I've seen with the Photoline.

I am, however, 100% imaging.

[Cjg]

@Gavster Perhaps also worth asking on CN, there seems to be more Frac users across the pond and you'll likely find someone whose made the jump in the specialist Frac forum. Love my Tak 76, but there's been a couple of times an extra inch of aperture would have come in handy. 

Chris

[A40farinagolf]

I have a 130 Altair Astro triplet with 0.79 reducer so either f7 or f5.5 - easy to handle at about 8Kg and I'd strongly recommend one.

Just used mine a few mins ago for visual of M45 on AZEQ6 in AltAz mode and the views were breath taking.

I'd ask Santa very nicely - you can't take it with you, money that is.

 

 

[Chris]

55 minutes ago, Gavster said:

I've got a T-Rex alt az mount which I think should be good for refractors up to 140mm in size

I'm pretty sure your sorted for any of the suggested scopes with the T-rex. I really like the look and reports on the APM scopes for their cost, but really have no personal experience of anything other than Synta ED's and a Meade 80mm triplet. All I can say it I like how doublets tend to be lighter and cool quicker, but understand that CA scales with aperture as well as focal ratio so I can see why a triplet would be of benefit with larger Apo's.

[GavStar]

7 hours ago, John said:

My TMB / LZOS 130 F/9.25 takes around 40 mins or so to cool. Not excessive for a triplet I think.

I understand that LZOS production is being moved away from scope optics so just 9 more will be made taking the total run to 114 units, according to Markus Ludes of APM. Seriously good optics in these scopes, believe me. The best I've ever viewed with - as good as the Tak FC-100DL, maybe even a touch better.

The T-Rex would handle one fine with the right tripod under it.

I did consider the APM 140mm F/7 and might have bought one if the LZOS 130 had not come along.

Doublets larger than 120mm are a bit thin on the ground I agree. I guess you do risk a touch of CA on the brightest objects with a larger doublet ?.

 

John, how much of a jump do you see from the 100DL to the 130 F9.25? Also how much of a chore do you find lugging the bigger scope around? Which one do you use the most?

[russp]

I'm using a carbon fibre tubed 127mm f7.5 which might fit your bill, much lower cool down being CF and much lighter. I've not used a shorter frac to compare it with unless you count the cheap 80 MM. doublet I use to guide with but it seems to produce lovely clear images with true colours. I'm in a wheelchair and have no abdominal muscles and have no problem moving it. It's a rebadged version of the Explore Scientific 127mm APO. http://www.opticstar.com/Run/Astronomy/Astro-Telescopes-Ascension.asp?p=0_10_1_6_52

[John]

3 hours ago, Gavster said:

John, how much of a jump do you see from the 100DL to the 130 F9.25? Also how much of a chore do you find lugging the bigger scope around? Which one do you use the most?

It is a bit harder work to setup than the 100DL because currently the mount I use for it is a Celestron AVX equatorial. In the new year I'm aiming to get a heavier duty alt azimuth setup for it which will make setup time the same as the 100DL. The 100DL cools in around 15-20 mins but it's a thin doublet in a thin tube so you would expect a difference in that. The 130 weighs 9kg all up (ie: with diagonal, tube rings, DT bar and 9x50 RACI finder) wheras the 100DL weighs around 4kg all up. Optically they are pretty much both perfect in terms of star test and show no CA whatsoever at focus and none either side of focus either, on any object. I've always seen a noticable difference in visual performance between my 4" fracs and my 4.7" ED120 so the 130 is that plus more. I've not had the chance to properly view Jupiter and Saturn with the 130 yet. I've seen quite a bit of detail on Mars and even managed to glimpse Neptunes moon Triton with the 130 which was a good show for a 5.1" aperture.

In terms of mounting requirements, the longer tube F/9.2 130 does put more stress on the mount than something shorter would of course. If that is an issue there is a shorter version of the scope - an F/6, which sells in greater numbers I believe.

The tube on these APM / LZOS scopes is Kruppax which cools reasonably quickly, is lightweight and also seems totally immune to dewing.

The downside to all this is that they are darned expensive when new - £5.8K to £6.8K apiece, depending on the model. Peak2valley instruments have an ex-demo APM/LZOS 130 F/9.2 going for £4K which has the 3" FT focuser (mine has a 2" FT). I was very lucky indeed to get mine at a far lower cost than that

IMHO and from other reports these scopes are among the very best 5" refractors ever made so I'm proud and pleased as punch to own one 

There are good 5" refractors around for a lot lower cost than these with LZOS optics of course so it depends what you want. I'm guessing that owning 2 4" Tak flourites will have given you a taste for fine optical performance

 

 

Edited December 22, 2016 by John

[Highburymark]

Having done a fair bit of research on Taks recently, I've been struck by the number of people - particularly in the US - who want to see Tak launch a 120-130mm doublet. I wonder whether that's part of the company's plans? An FC-130 at 7-8kg would be a lovely thing.

[stevepeverall]

I had a similar dilemma a year or so ago and decided to go for from a 110ED to a Mak 180. I loved the extra light grasp, observing from a suburban area in the midlands with reasonably dark skies (you could see the milky way unaided on some nights). The thing was I loved the extra light grasp but missed the pinpoint stars of the refractor so I sold the Mak and went for a APM 140ED.

That would have been great if I hadn't moved to London. With the light polluted skies there's not a huge amount of difference between a 110 and 140. The biggest difference is portability. The 110 is as grab and go frac on a an AZ mount, easily taken to somewhere dark. The 140 is much larger on a beefier mount and stays indoors (I don't have a garden at the moment).

In the long term when I move back out of London and have a garden the 140 will come into it's own but if your living in London and intend to travel with your scope to darker skies, portability is an issue.

PS. I wouldn't worry about CA if you're just using it visually. I see none.

[dweller25]

Hello Gavin,

I also had this dilemma several years ago  - I ended up with a Takahashi FS128 Fluorite doublet.

Time has moved on and APM are making two interesting doublets - the 152mm f/8 and the 140mm f/7

If I were looking now I would strongly consider the 140mm f/7 - especially as Steve in the above post says it has no visual CA

Edited December 22, 2016 by dweller25

[GavStar]

Thanks for all the comments. Astrograph had a Christmas offer on its in stock TEC 140mm so I've decided to get myself a Christmas present. It arrives next week and I'm looking forward to (hopefully) seeing a noticeable step up from 100mm to 140mm

Edited December 22, 2016 by Gavster

[John]

TEC 140 ? - superb scope

 

[dweller25]

TEC 140  - good choice

I noticed a significant increase in planetary detail going from 100mm to 128mm, so the 140mm should please

Edited December 22, 2016 by dweller25

[DaveS]

You won't go wrong with a TEC 140 APO.

[mikeDnight]

On 21/12/2016 at 22:33, Gavster said:

I've got a 100mm refractor (or two ?) but have been thinking for a while about stepping up to say 130mm to 140mm which I think is the max for me given weight etc. I'm visual only and so far have only used doublets.

The only APO doublet available at this size is the newish APM 140 f7. However I'd really like this scope to be a keeper and am a bit concerned about the f7 introducing some colour. The alternative is a triplet such as tec 140mm, cff 132mm or APM 130mm f9.25. But these seem to have longer cool down, heavier, and maybe trickier to set up and mount. I was hoping for a tak 130mm doublet but this doesn't seem on the cards in the near future.

So I'm unsure which way to go (or indeed should I stick with my 100mm since the jump to 130 to 140mm would not have much impact for visual?) Would the tec retain value the best if tak do release a larger doublet?

Any views would be appreciated?

Thanks

Gavin

The FS152 would be good if one came up secondhand!