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Super Telephoto L lens vs a 5-6" Triplet APO for imaging

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#1 tsk1979

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Posted 05 July 2022 - 12:53 PM

I was looking at "budget" 5-6" refractors (triplet APOs) and something like a ED152CF would cost around 4000$ (maybe a little less used). 

 

On ebay, the slightly older L lenses 600mm F4, and Nikon 600mm F4 also cost around 2500-3500$ and are top of the line offerings from Canon and Nikon.

 

I am wondering, what advantage does a triplet APO give over the Canon/Nikon lens. With a flattner/reducer, the backfocus for triplet is 55mm (similar to lens), and while the triplet are around 700mm F5.6 with reducers, the lenses are 600mm F/4 which makes for a fairly bright telescope for nebula as well as some larger galaxies. Moreover, you can use a 1.5X teleconverter too for increased reach.

 

I am unable to find many detailed astro reviews, but I am thinking would these refractors have coma issues? CA issues etc., as compared to triplets..?

 


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#2 Tapio

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Posted 05 July 2022 - 01:34 PM

Canon Ef-S flange is 44 mm and that might be problem with some cameras with filter wheels.

Also using these older lenses might be bit more difficult to arrange guiding and auto focusing.



#3 Headshot

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Posted 05 July 2022 - 01:47 PM

Many years ago (15?) a gentleman by the name of Samir Kharusi had a website where he posted some exhaustive test results from a Canon 600 f/4 telephoto lens vs a TeleVue telescope (Can't recall if it was a 101 or a 127). The link that I had to Samir's original site no longer works. Some of these results might be summarized on the dpreview site. While I do not remember the details, I believe they were fairly close in optical performance.

 

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#4 Avgvstvs

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Posted 05 July 2022 - 01:50 PM

Go the triplet. Less elements/lenses equals better images in my books.


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#5 bobzeq25

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Posted 05 July 2022 - 02:15 PM

I was looking at "budget" 5-6" refractors (triplet APOs) and something like a ED152CF would cost around 4000$ (maybe a little less used). 

 

On ebay, the slightly older L lenses 600mm F4, and Nikon 600mm F4 also cost around 2500-3500$ and are top of the line offerings from Canon and Nikon.

 

I am wondering, what advantage does a triplet APO give over the Canon/Nikon lens. With a flattner/reducer, the backfocus for triplet is 55mm (similar to lens), and while the triplet are around 700mm F5.6 with reducers, the lenses are 600mm F/4 which makes for a fairly bright telescope for nebula as well as some larger galaxies. Moreover, you can use a 1.5X teleconverter too for increased reach.

 

I am unable to find many detailed astro reviews, but I am thinking would these refractors have coma issues? CA issues etc., as compared to triplets..?

The triplet (with a flattener or flattener/reducer) will give you significantly better stars at the edges.  The lenses have to be designed to focus closer than infinity, that causes issues.  Why people overwhelmingly prefer the scopes.

 

You'd almost certainly wind up stopping the lenses down from F4, to get better stars.

 

The 1.5X teleconverter doesn't provide added reach for free.  You pay in signal to noise ratio.  Generally people feel the tradeoff isn't worth it.  Instead they use reducers to get less reach but better signal to noise ratio.

 

This is not terrestrial photography, to put it mildly.  The signal to noise ratio starts out _much_ worse.  You don't want to make it moreso.

 

A lot of very smart people have been doing it for a long time.  They don't miss much.

 

Your default option should be to follow the crowd.  To use equipment for what it was designed by a professional to do.  Creative solutions are more likely to be worse than they are likely to be better.


Edited by bobzeq25, 05 July 2022 - 02:17 PM.

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#6 photoracer18

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Posted 05 July 2022 - 03:01 PM

As mentioned many telephotos can't reach infinity focus without going back to the factory for an adjustment as that is not in their normal use range of focus. I sent one lens in my life back for that and I admit it was much better after that. I find some telephotos have perfect framing on some objects, with either APS-C or FF cameras. But that is one of only 2 advantages they have. The other is you are more likely to have a telephoto in your collection when you think about doing this. If you don't you are much better off buying a telescope, at least a decent ED one at a minimum. Telescopes have nearly an unlimited focus range so you have much more room for filters and other things that need to go between the optics and the camera. Much more than that 40-45mm registration distance from lens to camera you have to deal with SLR/DSLR lenses. I have a number of bigger telephotos, 100-300/4, 120-300/2.8, 300/2.8, and 150-450/4.5-5.6 and none of them have ever seen the night. Well one did see the night at the Rolex 24 Hour at Daytona one year but it was never pointed into the sky. I can see possible uses for WA lenses in the sky but not telephotos when you have perfectly build telescopes that do a better job.



#7 Tamiji Homma

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Posted 05 July 2022 - 03:01 PM

Many years ago (15?) a gentleman by the name of Samir Kharusi had a website where he posted some exhaustive test results from a Canon 600 f/4 telephoto lens vs a TeleVue telescope (Can't recall if it was a 101 or a 127). The link that I had to Samir's original site no longer works. Some of these results might be summarized on the dpreview site. While I do not remember the details, I believe they were fairly close in optical performance.

 

Headshot

 

The Samir's comparison was Canon EF 600L f/4 with/without 1.4x tele-extender and Televue 140mm f/5.

 

I have archived his pbase page in PDF.

 

Tammy



#8 900SL

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Posted 05 July 2022 - 03:07 PM

From Canon labs:

Since lenses have front and rear surfaces, this means that the overall loss of light from passing through one lens element is 8%. Most camera lenses are made up of five to 10 elements, and so in the end, the total amount of light getting through the lens is reduced by about 50%.

Ergo, use a scope. Less glass, more signal, less abberations
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#9 ngc7319_20

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Posted 05 July 2022 - 03:24 PM

The Samir's comparison was Canon EF 600L f/4 with/without 1.4x tele-extender and Televue 140mm f/5.

 

I have archived his pbase page in PDF.

 

Tammy

There are some of his comparison images at 

 

https://pbase.com/sa...i/televue_canon

 

Just with a quick look I would say the Canon 600mm F/4 has better image quality across the entire frame, and certainly wins in the corners and edges.

 

But the TV140 is sharper at the center.

 

Detection of faint stars is about the same with the Canon lens using shorter 13s exposures (vs 20 sec for TV140).  Interesting...


Edited by ngc7319_20, 05 July 2022 - 03:35 PM.

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#10 ngc7319_20

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Posted 05 July 2022 - 03:27 PM

From Canon labs:

Since lenses have front and rear surfaces, this means that the overall loss of light from passing through one lens element is 8%. Most camera lenses are made up of five to 10 elements, and so in the end, the total amount of light getting through the lens is reduced by about 50%.

Ergo, use a scope. Less glass, more signal, less abberations

The 8% number is for uncoated glass.  With modern multi-coatings this drops to 0.5% or less per element.  So the light loss is not a direct concern.  By the time you get a 3 element APO scpoe with a 4 element corrector, the throughput difference between the scope and telephoto lens is not huge.


Edited by ngc7319_20, 05 July 2022 - 03:31 PM.

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#11 RichA

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Posted 05 July 2022 - 09:03 PM

I was looking at "budget" 5-6" refractors (triplet APOs) and something like a ED152CF would cost around 4000$ (maybe a little less used). 

 

On ebay, the slightly older L lenses 600mm F4, and Nikon 600mm F4 also cost around 2500-3500$ and are top of the line offerings from Canon and Nikon.

 

I am wondering, what advantage does a triplet APO give over the Canon/Nikon lens. With a flattner/reducer, the backfocus for triplet is 55mm (similar to lens), and while the triplet are around 700mm F5.6 with reducers, the lenses are 600mm F/4 which makes for a fairly bright telescope for nebula as well as some larger galaxies. Moreover, you can use a 1.5X teleconverter too for increased reach.

 

I am unable to find many detailed astro reviews, but I am thinking would these refractors have coma issues? CA issues etc., as compared to triplets..?

https://www.cloudyni...28-lens-images/

 

 



#12 SilverLitz

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Posted 05 July 2022 - 10:02 PM

My experience w/ Canon EF300mm f/2.8L (non-IS) was very disappointing, with VERY bad stars at the edges of the small 183 sensor.  After coming to the conclusion that my EF300mm was of no use for AP (but good for normal uses), I got a Vixen FL55ss.  My FL55ss is FAR superior to my EF300mm copy.

 

I have not been pleased with star shapes of any camera lens I have tried, Canon 70-200mm f/2.8L IS ii and Samyang 135mm f/2.0, and all of these were tried on the small 183 sensor.  The Vixen FL55ss has much better stars on the larger QHY268.



#13 Jared

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Posted 05 July 2022 - 10:45 PM

Generally speaking, edge performance on a 600mm lens isn't all that important for the typical use case. Birds, wildlife, etc. The central two thirds of the field of view is generally very good, but most designs, especially those from a few years ago, do not have great results in the corners when shooting wide open. Why would they? Is rhino in the corner of the field? No? Then who cares? Limited depth of field is going to blur the heck out of the corners anyway. In addition, as others have mentioned, lenses need to work well at both close focus and infinity, and they need to have quick focusing by moving just one or two lightweight elements. The end result is lots of elements with accompanying light loss, decentering issues, etc. On average, a triplet telescope with a matched flattener or reducer is going to outperform even the very best photographic lens of the same aperture. It will likely be easier to adapt the telescope to astronomy cameras as well--typically more back space. 

 

End result? If you already own a long lens or if you will get double duty out of it (wildlife photography, birding, etc.), then by all means give it a shot. Generally, though, the astronomical telescope will do a better job for deep sky imaging.


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#14 Jeff Morgan

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Posted 06 July 2022 - 01:12 AM

The triplet (with a flattener or flattener/reducer) will give you significantly better stars at the edges.  The lenses have to be designed to focus closer than infinity, that causes issues.  Why people overwhelmingly prefer the scopes.

 

I was thinking of getting a somewhat smaller Canon lens (200mm) and started searching Astrobin for images with that lens. I came across images by Nico Carver (photographer turned astrophotographer) and we exchanged a couple of pm's on the subject.

 

He basically advised what you did. If you have a DSLR and do nature shooting, a telephoto makes sense. Otherwise, astro scope the whole way. He has a YouTube video where he compares a 20mm telephoto to an imaging scope directly. Pixel peeping tells the story:

 

https://www.youtube....h?v=dVEbOdn0qh0

 

Of course with a larger budget, there is this legendary telephoto. It has produced some nice images on Astrobin.


Edited by Jeff Morgan, 06 July 2022 - 01:18 AM.

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#15 akdwivedi

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Posted 06 July 2022 - 02:52 AM

there are few which have good reviews - sigma 135mm f/1.8 art, Samyang f/135mm f/2, canon 200mm f/2.8L ii, Canon 300mm f/4 and Canon 400mm f/5.6L.. I am sure some nikon ed lenses will probably give similar performance.

 

I also hear that 600mm f/4L is good but if a new one costs 12K and you could get a very good quality petzval or quintuplet for half that price which is optimized for astro photography. If you already own a 600mm f/4 L then its a no brainer, try it and if it works, it will save a few K investment which you can put into cameras and mounts.



#16 j.gardavsky

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Posted 06 July 2022 - 08:53 AM

I was thinking of getting a somewhat smaller Canon lens (200mm) and started searching Astrobin for images with that lens. I came across images by Nico Carver (photographer turned astrophotographer) and we exchanged a couple of pm's on the subject.

 

He basically advised what you did. If you have a DSLR and do nature shooting, a telephoto makes sense. Otherwise, astro scope the whole way. He has a YouTube video where he compares a 20mm telephoto to an imaging scope directly. Pixel peeping tells the story:

 

https://www.youtube....h?v=dVEbOdn0qh0

 

Of course with a larger budget, there is this legendary telephoto. It has produced some nice images on Astrobin.

This Leica APO Telyt R 3.4/180 is what I have been using with my Leica R7 and R8 cameras in classical photography, both for the terrestrial and astro.

 

The advantage of the Leica APOs is, they are corrected from less than 400nm up to around 700nm,

http://www.marcocavi...lass/00_pag.htm

 

For the longer focus lengths, the modular system https://www.apotelyt...-telyt-r-module came on the market

Comparable may be the recent ZEISS Tele-Superachromat T*, also manufactured for the 6cm x 6cm Habla digital cameras.

 

The astronomy triplet (fluorite, ED9) telescopes can't compete with these telelenses,

in spite of how much you would wish, and you eventually love to believe, I am sorry.

You need more lens elements than just 3 in the front light gathering group to get rid of the higher order aberrations across the full frame of your camera chip,

and you need the rear optics group (eventually with some ED glass) to get the flat field.

 

Even the "consumer optics" Leica 82mm APO Televid 5.4/440 spotting scope has 4 lenses in the front group, the internal focuser lens, and some lenses in the rear group for the field flattening.

 

As the premium telelenses are prohibitevly expensive, the astronomy refractors will dominate the hobby astrophotography.

For the wide field imaging, you may eventually find the old Leica APO Telyt for an acceptable price,

https://www.leicasho...yt-R-3-4-180mm/

 

Best,

JG

 


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#17 bobzeq25

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Posted 06 July 2022 - 11:54 AM

 

As the premium telelenses are prohibitevly expensive, the astronomy refractors will dominate the hobby astrophotography.

For the wide field imaging, you may eventually find the old Leica APO Telyt for an acceptable price,

https://www.leicasho...yt-R-3-4-180mm/

Half the price, and not merely half the quality for astrophotography.  6 elements, optimized for infinity, rather than needing to cover nearfield also.  Also, fixed optical speed at F4.5 makes less expensive optics work well for stars.

 

https://optcorp.com/...hotography-lens

 

Agree that if you want both terrestrial and astrophotography, a premium camera lens is a good solution.  And the only one for short focal lengths.


Edited by bobzeq25, 06 July 2022 - 11:57 AM.


#18 tsk1979

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Posted 06 July 2022 - 12:26 PM

thanks everyone. I guess I will be buying a 140PH most probably instead of spending the same amount on a used lens!



#19 Esso2112

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Posted 06 July 2022 - 05:09 PM

Also, keep in mind that Canon no longer will service some of the older L series lenses.  My Canon 500mm f4 L is lens is one that they won’t repair anymore.  It’s a great lens and still works fine, but in the future it could be an expensive paperweight.  


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