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  #61  
Old 29-01-2018, 07:52 PM
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  #62  
Old 29-01-2018, 08:43 PM
Wavytone
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Originally Posted by AG Hybrid View Post
It's no wonder even the best refractors with smaller apertures cant compete.
You should try again now that I've fixed the collimation. It was quite close but not quite perfect at 450X and I thought leave well enough alone. But last Saturday I broke out the screwdriver and tweaked it, ever so gently. All it took was barely crack 1 screw, perhaps 1/10th of a turn or less.

Now that it's spot on I can say a Strehl of 97% is quite something to behold, and I was quite surprised at just how much difference that tweak made at really high powers on close multiple stars and planets.

Something else also stood out looking at the moons of Jupiter and Saturn - even in poor to average seeing its quite easy to identify those that are moons and not stars. Jupiters moons are resolved nicely... Saturns are harder.

Compiling a list of close double stars to see how it fares near Dawes limit.

FWIW I have a nice 8" f/9 mirror with a fine figure in storage, never used.... I think that's going to be up for sale soon.
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  #63  
Old 29-01-2018, 09:01 PM
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With all the coming Planetary oppositions
OK I give in. Finally. For the first time in... cripes... 30 years... this year I'll try taking some shots with a camera through the scope.

By the way Joe, if you have the place to put it there are some serious big maks going... https://www.astromart.com/classified...fied_id=968866

... and more... it seems APM have sourced some large mak optical sets from LOMO again, 10" and larger.

I'll have to wait till retirement but by then I probably won't be able safely lift one larger than my current one.
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  #64  
Old 29-01-2018, 09:06 PM
bigjoe (JOSEPH)
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You should try again now that I've fixed the collimation. It was quite close but not quite perfect at 450X and I thought leave well enough alone. But last Saturday I broke out the screwdriver and tweaked it, ever so gently. All it took was barely crack 1 screw, perhaps 1/10th of a turn or less.

Now that it's spot on I can say a Strehl of 97% is quite something to behold, and I was quite surprised at just how much difference that tweak made at really high powers on close multiple stars and planets.

Something else also stood out looking at the moons of Jupiter and Saturn - even in poor to average seeing its quite easy to identify those that are moons and not stars. Jupiters moons are resolved nicely... Saturns are harder.

Compiling a list of close double stars to see how it fares near Dawes limit.

FWIW I have a nice 8" f/9 mirror with a fine figure in storage, never used.... I think that's going to be up for sale soon.
Wavy...

Collimation...Thats actually a bigger problem than most realise with SCTs and even less frequently Maksutovs

One of the main reasons otherwise good SCTs get bad raps..usually the owners fault ..some are even sold way out of collimation to the unwary, only to be cursed and resold within months..

They all screem foul about the ordinary images, and thats one bad reputation they unfairly hold ..bad images that should not be in most cases...Ive had some really good ones...Collimation and cooling is a must otherwise they will perform poorly.

PS: Wonder if Synta SW or Celestron will ever release a big Maksutov over 200mm , they had one 305mm in testing ..what happened to that!

bigjoe

Last edited by bigjoe; 29-01-2018 at 09:07 PM. Reason: Add
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  #65  
Old 30-01-2018, 09:01 AM
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Quote:
Originally Posted by Wavytone View Post
You should try again now that I've fixed the collimation. It was quite close but not quite perfect at 450X and I thought leave well enough alone. But last Saturday I broke out the screwdriver and tweaked it, ever so gently. All it took was barely crack 1 screw, perhaps 1/10th of a turn or less.

Now that it's spot on I can say a Strehl of 97% is quite something to behold, and I was quite surprised at just how much difference that tweak made at really high powers on close multiple stars and planets.

Something else also stood out looking at the moons of Jupiter and Saturn - even in poor to average seeing its quite easy to identify those that are moons and not stars. Jupiters moons are resolved nicely... Saturns are harder.

Next time we meet. Can you bring what ever tools you used? I'd like your help collimating my Mak. After opening it up multiple times for flocking the collimation is slightly out. At least according to star tests.
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  #66  
Old 30-01-2018, 02:34 PM
glend (Glen)
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Back on topic: the Skywatcher ED150.

As might have been mentioned previously, the APM 152mm Doublet, f7,9 happens to use FPL-51 and Lanthanum, which might be pretty close to the Skywatcher ED150 spec. The APM, and its Lunt, breathern, are pretty higjly regarded as a visual scopes. Could the APM have been the Skywatcher target. With Andrews now listing FPL-51 as one component, it is a possibility. Its (the ED150), affect on the APM price point, longer term, could be interesting.
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  #67  
Old 30-01-2018, 06:33 PM
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Yes as we all know , the mating element makes or breaks an objective and FPL51 and Lanthium are well regarded in this respect and with SW's track record ( ED80 -100 and 120 , yes I know these are SPL53 but not a Lanthium mating element ) I believe these should be a little better than the APM/Lunt 150mm APO's .

Computer mapping has come a long way in the 5 or so years since APM did the un-believable by allowing us with little money the chance to own a 6 inch APO .

Well done Sky Watcher , I will be following these very closely ( along with plenty of others I am sure ) .

Go on Lewis be out beta tester here in Australia . . Go on !

Brian.
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  #68  
Old 30-01-2018, 06:46 PM
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Well, technically they aren't apochromats

I am seriously considering one.
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  #69  
Old 30-01-2018, 06:58 PM
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Knew it ,, did not take long ,,,,, but yes they pass the APO spec by bringing 3 colours to a point that is perfect enough for visual , these were never designed for AP , thats why there are 80-100mm short f/l triplets and quads out there .

But never the less do a google on 'astro photography with an ED80' and you will see plenty of awesome shots taken with a ' Technically non APO ' scope but as said these were not designed for AP in mind , imagine the mount needed ,,, mmmm AP900 or 1200 ? perhaps ? .

Go for it Lewis ,,, . get one .

Brian.
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Well, technically they aren't apochromats

I am seriously considering one.
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  #70  
Old 30-01-2018, 07:12 PM
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For sure you can do AP with doublets, and some are better than others, but there is ALWAYS a slightly observable halo despite the best correction. A good triplet or quad on the other hand mitigates it almost entirely (notice I said GOOD - there are a few triplets out there not even as good as a good doublet!)

My BD150 is going to be a pure visual instrument. That's all I want it for. Unless I buy Steffen's Mak :drool:
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  #71  
Old 30-01-2018, 07:36 PM
thebonz (John)
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skywatcher

If these are what they are built up to be., I will have a severe case of TAKYPHALAXIS and put my FS128 in the museum for preservation and bring on the 6 incher
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  #72  
Old 30-01-2018, 07:37 PM
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Or sell me the 128 so you can afford the 150 (just after I sold the Tenba FS128 case of course)
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  #73  
Old 30-01-2018, 08:09 PM
bigjoe (JOSEPH)
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Quote:
Originally Posted by Wavytone View Post
OK I give in. Finally. For the first time in... cripes... 30 years... this year I'll try taking some shots with a camera through the scope.

By the way Joe, if you have the place to put it there are some serious big maks going... https://www.astromart.com/classified...fied_id=968866

... and more... it seems APM have sourced some large mak optical sets from LOMO again, 10" and larger.

I'll have to wait till retirement but by then I probably won't be able safely lift one larger than my current one.
Matthias Wirth scopes are beyond awesome and designed by Dr Phillip Keller...in Germany...Some of those LOMO Russian blanks are tens of thousands alone!

The prices are usually Astronomical to use a very worn out pun..but its the same performance as an 11 inch Apo that one offered in the Ad.

If I ever bought something like that....................."Im gunna need a bigger boat"! .....read that mount...some time off yet!

bigjoe

Last edited by bigjoe; 30-01-2018 at 08:13 PM. Reason: Add
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  #74  
Old 30-01-2018, 08:47 PM
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Lewis, No halos here, nada, zip, none

Last year I came to the conclusion that APO's are all wannabe's. Wannabe reflectors, that is.

Shocking, I know.

They can be very good, I agree, but none are perfectly achromatic across the whole spectrum in the way that a good reflector or catadioptric is.

FWIW there is an interesting rumour that Questar is considering making a Q5. That should be a really, really interesting scope, and if it came down to a choice of that vs a Takahashi I'd take the Q5, no question.
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  #75  
Old 30-01-2018, 09:02 PM
thebonz (John)
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q5

It as depends on your point of view of course. The doublet refractor will give wider field views that settle very quickly where as the mac will be a longer focal length narrower field of view. Horses for courses of course.
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  #76  
Old 30-01-2018, 09:05 PM
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Adrian did flocking make much difference to your scope ? For example, contrast when observing a star near the lunar limb, where stray light is very difficult. Mine is good at that test, but am scratching my head as to whether flocking would make any difference.

Reason I ask is that I'm preparing to pull my OTA apart later this year for several mechanical mods, and am thinking about whether to flock the inside of the OTA as well.

FWIW Steffen has just listed his Intes 6" mak. The humidity must have driven him crazy.
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  #77  
Old 30-01-2018, 10:00 PM
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Originally Posted by Wavytone View Post
Lewis, No halos here, nada, zip, none

Last year I came to the conclusion that APO's are all wannabe's. Wannabe reflectors, that is.

Shocking, I know.

They can be very good, I agree, but none are perfectly achromatic across the whole spectrum in the way that a good reflector or catadioptric is.

FWIW there is an interesting rumour that Questar is considering making a Q5. That should be a really, really interesting scope, and if it came down to a choice of that vs a Takahashi I'd take the Q5, no question.
We shall agree to disagree

More pros with a refractor IMHO than a Mak.
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  #78  
Old 31-01-2018, 08:02 AM
glend (Glen)
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We shall agree to disagree

More pros with a refractor IMHO than a Mak.
Mak, Mak, Mak, get over it. Questar's are not exactly cost effective regardless of size. An 8" Edge HD makes more sense, and i have one. However, i cannot denigh the attraction of a good long refractor at a reasonable price. I would like to put the Skywatcher ED150 f8 up against my iStar 127mm f12 R30 Anastigmatic, Strehl of 0,93.
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  #79  
Old 31-01-2018, 10:25 AM
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Mak, Mak, Mak, get over it. Questar's are not exactly cost effective regardless of size. An 8" Edge HD makes more sense, and i have one. However, i cannot denigh the attraction of a good long refractor at a reasonable price. I would like to put the Skywatcher ED150 f8 up against my iStar 127mm f12 R30 Anastigmatic, Strehl of 0,93.
Questars are not as good as their fable either. Not sure anyone was talking Questar here anyway?

And Matt no longer has his Mak either - the continual dew problems and protracted cool-down (plus the desire for a Bino-scope Tak) saw him sell that. I experienced the same issues with the Maks I have owned (2).
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  #80  
Old 31-01-2018, 11:01 AM
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AG Hybrid (Adrian)
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Originally Posted by Wavytone View Post
Adrian did flocking make much difference to your scope ? For example, contrast when observing a star near the lunar limb, where stray light is very difficult. Mine is good at that test, but am scratching my head as to whether flocking would make any difference.

Reason I ask is that I'm preparing to pull my OTA apart later this year for several mechanical mods, and am thinking about whether to flock the inside of the OTA as well.

FWIW Steffen has just listed his Intes 6" mak. The humidity must have driven him crazy.

Like all telescope designs, be it refractors, reflectors and composites. You can't gain contrast over the original intended design. But, through manufacture process and materials used it can be lost due to light scatter and what not. Flocking helps with removing the doubt of "Am I getting the best performance?". In my case, the flocking reduced stray light illuminating my inner tube as my backyard is rather well lit through no fault of my own.
The long focal length and optical design already lends to excellent contrast.
Flocking made the biggest difference in my Skywatcher strut dob.
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