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affordable 6" apo options

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#26 A. Viegas

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Posted 22 July 2021 - 02:37 PM

Optical quality, color correction, contrast, better mechanicals.

Bob


If you are going to be shooting mono then there is not going to be much of an advantage paying for a top quality APO when you can get a decent mid range ED or “Semi-APO” that will pull in the same photons. I use a “semi-apo” 6” and get what I think is good data. Granted my Lum and Blue channels have some bloat but when I am shooting SHO it does not matter. Now don’t get me wrong I have a nice AT65EDQ and it puts out much crisper OSC data and I don’t have any bloating in Lum or Blue but with the $$ you save with a non super premium 6” you can buy a lot of other goodies and more scopes too. At one time I had my smaller 65 on the 6” and I shot the color with the small scope and the narrow with the bigger one. Anyhow like all things in this hobby there are many different paths to get where you think you want to be and ultimately whatever you pick there will always be other options and tweaks to get you to that next level. Obviously for visual a top APO is hard to beat.

Al

#27 Jeff B

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Posted 22 July 2021 - 02:51 PM

I like this option because it is a bit larger which is great. no doubt it will need an upgraded  focuser, likely I would go with a moonlight motorized.

 

The question I would have prior to ordering this bad boy is it will handle my ES" reducer/flattner which I already own:

 

https://www.highpoin...fRoCvcQQAvD_BwE

Now I do have to tell you it's a bit porky, maybe a pound or two, for the aperture, compared to say the APM/LZOS 152 F8 or TEC 160FL F7.  But it's very well made.

 

Can't help you relative to a reducer/flattner though.

 

Good luck!

 

Jeff 



#28 TNmike

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Posted 22 July 2021 - 04:16 PM

affordable

6"

apo

 

Pick two...


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#29 SilverLitz

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Posted 22 July 2021 - 04:50 PM

For AP, there will be little (or any) benefit for pushing your image scale to finer than your seeing/3, as seeing jitter would blur out any possible higher resolution.  For my location, with its good 1.5" typical seeing, I would not pay-up to push it finer than 0.5"/px, which translates to my SVX130T with an 183 camera, or EdgeHD 925 with 0.7x FR & 268 camera.



#30 Wildetelescope

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Posted 23 July 2021 - 10:06 AM

This is the only option I can come up w as "affordable."  Anything above this price range by much I am feeling like may be too deep down the refractor rabbit hole, but still my concern is, spending more than $6k and getting, cheapy glass?     I say that because I have the ES 127 FCD100 but I started with the FCD1 version and from day one, wanted "better glass," and so I traded up. But is it worth it get get a $6k+ imaging refractor that may not have a great strehl and could have false color? Perhaps i should consider the SW Esprit. 

 

 

https://explorescien...in-carbon-fiber

What exactly was it about your FCD1 lens system that you did not like?   Since you started with the FCD1 and upgraded to the FCD 100 it would be interesting to see a comparison of images from each to understand what the difference in results were.    For imaging, I am not sure that going from a 5 to a 6 inch scope is going to buy you much except a smaller FOV.    I use my 6 inch F9 for planet imaging and visual, and my 5 inch f8 for DSO imaging.  If I want longer focal lengths for imaging DSO's I jump to my C8 Edge.    As always YMMV.   Bottom line, if you want a 6 inch scope and can afford it, I say go for it!  If you want to best, then save for it.  I have been very happy with my scopes that have "lesser" glass types, but can understand if someone wants to go high end.    There is a difference, it is up to you if it justifies the additional cost. Good Luck!

 

JMD



#31 rgsalinger

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Posted 23 July 2021 - 10:47 AM

First of all, I'm certain that you can get good results with less expensive refractors. However, I think that if you measure the data, rather than look at the results, you'll find that there's a clear advantage when you spend more money for an expensive refractor. What I think that you'll find is that those expensive refractors produce better data. How much that's worth is another question. As someone who struggles with processing, I tend to want the best data to start with as it eases the processing.

 

There's also that elusive build quality. My big refractor is going on 15 years old and it still produces very close to seeing limited results night after night. In fact, the results are so close to what my 12.5" reflector produces that I toy more often with getting rid of the reflector (and saving my back) than anything else. 

 

So, if I wanted to get the best information, I'd be asking people who have some of the less expensive 6-inchers to post some raw data. Then you can make a much more informed judgement that using secondary measures like "what glass" or Strehl measurements. All that counts is the quality of the data that the instrument produces. 

 

Rgrds-Ross


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#32 Ballyhoo

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Posted 23 July 2021 - 12:58 PM

First of all, I'm certain that you can get good results with less expensive refractors. However, I think that if you measure the data, rather than look at the results, you'll find that there's a clear advantage when you spend more money for an expensive refractor. What I think that you'll find is that those expensive refractors produce better data. How much that's worth is another question. As someone who struggles with processing, I tend to want the best data to start with as it eases the processing.

 

There's also that elusive build quality. My big refractor is going on 15 years old and it still produces very close to seeing limited results night after night. In fact, the results are so close to what my 12.5" reflector produces that I toy more often with getting rid of the reflector (and saving my back) than anything else. 

 

So, if I wanted to get the best information, I'd be asking people who have some of the less expensive 6-inchers to post some raw data. Then you can make a much more informed judgement that using secondary measures like "what glass" or Strehl measurements. All that counts is the quality of the data that the instrument produces. 

 

Rgrds-Ross

I suppose if i have a 127FCD100 a tec 140 would not be large enough increase to make a difference.

 

I don't know, if i want more punch than my 127 and the 6" is not enough increment increase maybe I should just get the C9.25. Seems like it is hard to know what difference there will be bw a 5" and 6."

 

and the Tec 160 is not quite crazy money but not far from.

 

Edit

 

I think my route refractor wise would be that 155mm is it a leap from the 127.  The Esprit is 150 versus Teleskp 155.

 

Is there anything wrong with the glass of the Telskop?   I would swap out the focuser for something nice, like a moonlight, or a ML for sure. Not much else can be done to make it nicer.

 

I just need to see about what reducer for the Telsk and whether my ES 3" would work. 


Edited by Ballyhoo, 23 July 2021 - 01:04 PM.


#33 rgsalinger

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Posted 23 July 2021 - 01:47 PM

I have a 127 and it's a great scope but it's only 660mm of focal length so rather undersampled with current cameras. The 155 was a big improvement in quality. I can't tell if that's a brand issue or if it's just having 30 percent more glass. Getting under 1 arc secomd per pixel using the dark skies that I have seems to also be part of the improvement. Glass I can't comment on because I just don't care about it. I base my judgements on what the data quality is for the scope. Incidentally, the 155 I have needed a flattener to handle an APS-C chip. I've not tried it will full frame as yet.

 

Rgrds-Ross


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#34 Ballyhoo

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Posted 23 July 2021 - 02:01 PM

I have a 127 and it's a great scope but it's only 660mm of focal length so rather undersampled with current cameras. The 155 was a big improvement in quality. I can't tell if that's a brand issue or if it's just having 30 percent more glass. Getting under 1 arc secomd per pixel using the dark skies that I have seems to also be part of the improvement. Glass I can't comment on because I just don't care about it. I base my judgements on what the data quality is for the scope. Incidentally, the 155 I have needed a flattener to handle an APS-C chip. I've not tried it will full frame as yet.

 

Rgrds-Ross

just to be clear, whch 155 do you have? Oh the APM...  is that a triplet?



#35 Wildetelescope

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Posted 23 July 2021 - 02:34 PM

just to be clear, whch 155 do you have? Oh the APM...  is that a triplet?

Ross' scope would be Astro Physics.  Yes it is a triplet.  Arguably among the finest optics you can buy.   As Ross has said, I would not get hung up on Glass type too much.  If you are buying premium optics, that is where things start, but It is much more about what they DO with the glass.   The AT/MEADE/TS triplets with the FK61 grade glass all have a group of happy users.  If you are doing narrow band imaging, you will likely not notice any great difference between the scopes in that price range.  You will have to spend about twice your budget to see something better, IE a 6 inch AP, Tak, CFF, etc...  

Good Luck!

 

JMD



#36 rgsalinger

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Posted 23 July 2021 - 06:39 PM

My point is that using "premium" optics on both refractors, the 6" turned out for me to be a much better scope for small objects than my 5".

 

I think that's because because the greater focal length gives me better sampling with my cameras and hence better detail (at my usual location) given the seeing. I also think that F7 is fast enough to get a picture every clear night that the OP will be happy with. If I was still using my ASI1600,  then a flattener would not be necessary. I'm all about convenience and I don't want to be wasting time collimating optics or waiting for big mirrors to cool down on the nights when I'm portable. So, I love the 6" and my bet is that the OP would too, particularly given the ASI1600.

 

I don't think that brand is that important any more. I've had these two scopes from a long time. My bet is that you will get the same kind of boost from the same upgrade with Skywatcher, Orion etc. 

 

Rgrds-Ross


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#37 Ballyhoo

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Posted 23 July 2021 - 09:28 PM

well I image w the ASI294mm now but a member is offering me a nice deal on the carbon fiber ES 152, which is FCD!. now that is F8 but I have the 3" reducer. I wonder though if imaging the native F8 would be worthwhile for image-scale on the galaxy targets



#38 rgsalinger

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Posted 24 July 2021 - 12:03 AM

Here's a shot taken at F8 - about 2 hours worth of data a week ago through an Ha filter. Image scale is .6 arc seconds/pixel.

 

 

M17_HA_small.jpg

 

 

 

So, I think that you can image happily with modern equipment at F8 with small pixels and a high QE camera.

 

 

Rgrds-Ross

 

 

 

 


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#39 teashea

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Posted 24 July 2021 - 08:45 PM

This is the only option I can come up w as "affordable."  Anything above this price range by much I am feeling like may be too deep down the refractor rabbit hole, but still my concern is, spending more than $6k and getting, cheapy glass?     I say that because I have the ES 127 FCD100 but I started with the FCD1 version and from day one, wanted "better glass," and so I traded up. But is it worth it get get a $6k+ imaging refractor that may not have a great strehl and could have false color? Perhaps i should consider the SW Esprit. 

 

 

https://explorescien...in-carbon-fiber

Seems pretty nice.  A Takahashi TOA130 is going to be way way above what your price point is.



#40 Ballyhoo

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Posted 24 July 2021 - 10:59 PM

but I wonder if I am spinning my wheels too. What is the difference in imaging and viewing bw a 5" that I have and the 6" that I always wanted? Is the difference merely that I always wanted the bigger scope?



#41 weis14

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Posted 24 July 2021 - 11:11 PM

but I wonder if I am spinning my wheels too. What is the difference in imaging and viewing bw a 5" that I have and the 6" that I always wanted? Is the difference merely that I always wanted the bigger scope?

I'm not enough of an imager to comment on the difference for that purpose.  However, I have had both a 130mm and 160mm (at different times) and visually I could tell the difference right away when I moved from 130mm to 160mm.  Remember that the light gathering power is a function of the diameter squared, which means that the 160mm will have 1.5 times as much light gathering power than the 130mm.  In my experience, this is enough to make a clear difference.  


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#42 PPPPPP42

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Posted 24 July 2021 - 11:21 PM

This:

https://explorescien...-fpl53-165cf-01


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#43 Marcus Roman

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Posted 25 July 2021 - 06:31 AM

Teleskop Service proposes a 155mm f/8 triplet with FPL-55 glass, the equivalent of FPL-53 but blanks cost a little less and it polishes better.

 

https://www.teleskop...zertifikat.html

 

I don't know how much it costs in dollars but the Astro-Tech 152 uses FK-61 low dispersion glass that performs a little inferior to FPL-55. The scope belongs to a new series, all diameters made with 55 glass, serial-numbered and guaranteed to have 0.95 Strehl, the certificate is included.

I watched through it a couple of nights ago. We were a group of friends, expert astronomy amateurs, some with experience of AP Starfire EDF155, one had a gorgeous Atlux 150ED right the same night, and the TS155 was giving visual images of Jupiter so sharp and so bright we were alla flabbergasted….I don’t and cannot know whether that was a particularly good sample but we all wound up thinking it was a very very good 6” apo though lens are most probably manufactured in China (mental bias?)………to ponder at least as an option.


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#44 Ben the Ignorant

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Posted 25 July 2021 - 07:08 AM

I don’t and cannot know whether that was a particularly good sample

When the minimum Strehl is 95% no sample can be greatly better than another so I would say you can expect the same quality from any sample. In a brief email conversation with someone at Teleskop Service before I ordered my 115 Photoline triplet, they told me the chinese now use mostly chinese-made glass that has been much improved in the latest years.

 

And as much as japanese, german, russian and american apo makers like to boast about the finesse of their optics, figuring and polishing a 150mm blank is not such a feat because very good mirrors up to 400mm have been made by several factories for decades, especially GSO.

 

Of course a lens has other challenges, glass purity (problem solved now) and critical alignment of both surfaces, but they are simply never that large so making excellent ones is not the end of the world for experienced makers. My chinese 115 turned out perfect with excellent straight and sharp Ronchi lines, no scattering, super-deep coatings, perfect centering/collimation, intense stars at focus, ideal defocus patterns, no chromatism to speak of, and strong contrast.

 

I would be very confident buying their 130 or 140 if I had the cash, especially the newer ones with certificate.


Edited by Ben the Ignorant, 25 July 2021 - 07:09 AM.

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#45 Ballyhoo

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Posted 25 July 2021 - 12:19 PM

I suppose I should sell my 5" triplet now that I ordered the 6" from another member.  I have to think there is no reason to have a both a 5" and a 6" ES triplet though the 5" is FCD100 vers the ED glass of the 6"


Edited by Ballyhoo, 25 July 2021 - 12:19 PM.



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