APM Doublet ED Apo 152/1200 mm OTA

[John]

If I'm spending that kind of money I want a "proper" telescope colour scheme which, for me, is a white tube with black trim

[Stu]

Sorry to drag up such an old thread, just wondering if anyone has had any experience with the APM 152 ED doublet?

At some point, I would love a 6" refractor with decent colour correction and this one seems quite close to being a good contender. I had a very nice, long chat with the chap from APM at PSP and if finances ever allow I would be quite tempted.

The basic one seems vaguely within reach, but then there is the LZOS version with Kruppax tube which would probably be amazing. Silly money though.

http://www.apm-telescopes.de/en/Telescopes-/Refracting-Telescopes-OTA/Apochromates/APM-LZOS-Telescope-Refractor-152-mm-f/1200-mm-2.5-ZTA1.html

Wonder how these compare with TEC 140 etc for visual use?

Stu

[John]

I saw one of the new APM 6" doublets at a show this summer Stu. I was so tempted to reach for my credit card !. It seemed really well put together and is pretty lightweight too, for a 6" refractor. Having just taken delivery of the 6 foot long Istar 6" F/12 achromat though I was really not going to be able to explain another 6" frac to my other half !

Initial reports from owners on Cloudynights seem favorable though I don't think many of these are "out there" yet.

I had a lot of fun with the cheap approach of 6" F/8 achromats and Chromacor correctors a couple of years back so I've seen what a 6" ED doublet can do more or less. Very nice views

A Vixen 150mm F/9 ED doublet was on UK AB&S for £1,600 recently and I reckon that would perform similarly to the APM 6" doublet but it's a lot heavier.

Sorry to rabbit on even though I've actually not used the scope you are interested in - I get quite excited about big refractors

[Stu]

I saw one of the new APM 6" doublets at a show this summer Stu. I was so tempted to reach for my credit card !. It seemed really well put together and is pretty lightweight too, for a 6" refractor. Having just taken delivery of the 6 foot long Istar 6" F/12 achromat though I was really not going to be able to explain another 6" frac to my other half !

Initial reports from owners on Cloudynights seem favorable though I don't think many of these are "out there" yet.

I had a lot of fun with the cheap approach of 6" F/8 achromats and Chromacor correctors a couple of years back so I've seen what a 6" ED doublet can do more or less. Very nice views

A Vixen 150mm F/9 ED doublet was on UK AB&S for £1,600 recently and I reckon that would perform similarly to the APM 6" doublet but it's a lot heavier.

Sorry to rabbit on even though I've actually not used the scope you are interested in - I get quite excited about big refractors

Yes, I thought it was a lovely looking, and well put together scope. The focuser was very nice, and with self centering 'quick lock' style fittings. I would assume the colour correction is pretty good, though not up to triplet standards obviously. I believe the LZOS versions hold up better at higher magnifications for planetary. There is a nice review from Neil English here, would be interesting to know the difference between the standard and the LZOS doublet which he reviewed.

http://neilenglish.net/a-new-large-aperture-ed-doublet-refractor-from-apm/

I did enquire about the Vixen but was too late, I think the lighter tube of the APM would suit my mount better anyway.

Out of interest John, where did you get your chromacorr? They seem to be fairly elusive, borderline 'mythical!!' They do sound a very interesting option though.

Feel free to rabbit away :-). I am developing a liking for big fracs too, not the f12 or 15 type, but nice f8 ish ED's.

Cheers

Stu

[John]

I've managed to find 3 Chromacor's over the past few years, a couple through e.bay where I was the only bidder and one that came fitted in a scope that I bought from Norwich AS (they knew it was in there !). The last one was a Chromacor II which are even rarer than hens teeth. 

They can have a dramatic effect on the optical performance of a correctly matched objective lens provided that they are positioned precisely in the right place in the optical train and the scope is accurately collimated. 

Quite a lot of provisios there so I think finicky is an apt description as mythical is

When I got things adjusted correctly I was getting close to ED doublet performance from the chinese 6" F/8 scopes as the Chromacor not only removes around 80% of the CA but also, if properly matched, corrects spherical aberration too, which is a pretty common defect in the chinese achromat objective lenses. 

Chromacors have been out of production for some years now as the advent of relatively low cost ED doublets sort of killed the demand for an $800 corrector.

I believe Istar are currently working on a similar corrector although it's gestation period has proved long and I think there are now some doubts on how much of a priority it currently is for them.

I did a write up of my experiences with the first Chromacor that I tried, if it's of any interest:

ccreview.pdf

[Stu]

Thanks very much John. Will have a read of your review later on. All very interesting :-)

Cheers,

Stu

[ollypenrice]

F6 would be fast for a six inch triplet. TEC stick at F7.5 for the slightly smaller 140 triplet. For a doublet it strikes me as being too fast to be more than achromatic. However, that's just my scepticism showing through and I've no way of knowing how this scope will perform.

The TEC is exquisite in visual use and very competent in CCD imaging, though the blues could be a little tighter. Around 4000 euros is the usual asking price for used ones. Build quality is exemplary.

Olly

[Stu]

F6 would be fast for a six inch triplet. TEC stick at F7.5 for the slightly smaller 140 triplet. For a doublet it strikes me as being too fast to be more than achromatic. However, that's just my scepticism showing through and I've no way of knowing how this scope will perform.

The TEC is exquisite in visual use and very competent in CCD imaging, though the blues could be a little tighter. Around 4000 euros is the usual asking price for used ones. Build quality is exemplary.

I think they are nearer f8 Olly, 152mm aperture and 1200mm f/l. Agree that f6 would be a challenge but f8 should be more manageable.

Stu

Olly

[Stu]

Managed to put my answer within your quote, hopefully it notices still!

Stu

[ollypenrice]

Doh, you're right. My mistake. F8 is indeed far more reasonable. Even the very budget F8 Synta six inch was not at all bad for the price.

Olly