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The Best Telephoto Lenses for Astrophotography

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The Best Telephoto Lenses for Astrophotography

Rudy E. Kokich

Over the last ten to fifteen years excellent apochromatic telescopes have become available for visual use and photography. Along with improvements in telescope mounts, camera technology, filters, and digital image processing, these have allowed amateurs to produce astrophotographs of nearly professional quality.

However, these APOs have a couple of drawbacks. One is the price, which starts around $800 for the smallest units, and rapidly climbs into thousands of dollars for larger apertures. Another drawback is the focal length. Most of these APOs have F ratios around 6.5, and are unable to comprehend in their field of view large celestial objects such as the Andromeda galaxy, the North America nebula, and comets. Some APOs can be fitted with pricey telecompressors, but those invariably result in vignetting and coma.

Especially for beginning astrophotographers, who should first invest most of their finances into a good telescope mount, telephoto lenses are an excellent and affordable solution. 135mm and 200mm lenses are suitable for wide angle star-field views, and comet and asteroid hunting, while 300mm lenses serve very well for the Andromeda galaxy, large emission nebulae, open clusters, and even larger globular clusters. Aside from being much more affordable, telephoto lenses are easier to transport, easier to mount and easier to guide, and are much more likely to produce encouraging results to a beginner.

Over the years, I have tried more than two dozen telephoto lenses, until I finally found three or four perfect solutions. But first, there are several general rules which must be understood.

Zoom lenses are entirely unsuitable for astrophotography due to prominent aberrations of every kind. They are by nature designed to compromise by magnification and distance, and are therefore not optically optimized at any single setting.

Because of chromatic aberration, no telephoto lens can be used at full aperture. The best ones listed below serve well with a one stop reduction, and some require two or even three stops.

Reducing aperture with the built-in aperture iris interferes with the light path, and results in eight diffraction spikes around bright star images. Some people like these, and consider them decorative. I do not presume to further decorate the universe, and perceive them for what they are: interference. I therefore reduce the aperture at the front end of the lens (as an aperture stop) by screwing in a series of step-down rings into the filter thread. These are affordably available on eBay, and result in perfectly round star images, the way nature intended them to be.

There is some controversy about the use of UV filters, but I found that a good UV filter significantly improves contrast, sharpens small star images, and reduces chromatic aberration. By far the best one is the Tiffen Haze 2 filter. Unfortunately it is not manufactured in a multicoated version, and produces prominent internal reflection artifacts on very bright stars. Nevertheless, it performs excellently on most star fields, and is too cheap not to acquire. The second best, is the Hoya Pro One Digital MC UV(0) filter. I use it routinely in preference to many other multicoated filters I tested, including the new Hoya MC UV©.

All lenses mentioned below are adaptable to Canon EOS cameras with slim EOS adapters which allow the lenses to focus just slightly past infinity. Focusing should be done on moderately bright stars using the 10x magnified Live View. Because of some residual chromatic aberration even with the aperture stop, the best focus lies not where the star image is the smallest, but rather just slightly away from infinity, at the point where the star image barely begins to enlarge. This way the focus will favor the red light which is more objectionable within a star image than a bit of blue.

No telephoto lens can be used with cameras modified by the removal of the internal UV/IR cut filter and anti-aliasing filter. Such "full spectrum" cameras are somewhat more sensitive in the ultraviolet, but much more sensitive in the deep red and infrared. No telephoto lens, and no apochromat, is sufficiently corrected to accomodate such a wide spectral range. Whereas quality apochromats can be corrected with broad band filters, such as the Astronomik UV/IR cut filter or the CLS-CCD filter, telephoto lenses can not. However, they can be perfectly corrected with narrow band H-alpha or OIII filters.

Finally, to prevent image shift during exposure, all telephoto lenses must be supported at two points: at the camera end, and at the far end with a large retaining ring. To prevent damage to the lens finish, apply nylon acorn nuts (or cap nuts) to the tips of the retaining ring's three alignment screws. The screws should be set sufficiently tightly to prevent shift, yet not so tightly as to interfere with fine focusing.

It may be superfluous to add, but it can't do any harm, that in astrophotography all shutter control must be done with a wired or wireless electrical shutter release swith. Touching the telescope, even ever so slightly, will introduce vibrations which will ruin the photograph. Also, accurate guiding is essential. If the telescope mount is precisely aligned to the celestial north pole, unguided exposures of one to two minutes are possible. A series of such images can be digitally stacked to produce excellent results. However, I find the process tedious, and prefer single, manually guided, long exposures which seem to have deeper colors. My guidescope is a 5in F5 Jaeger's achromat with a 2.3x Barlow, and a 9mm illuminated reticle eyepiece. This gives me the power of 162x, which is barely sufficient for my 420mm fl APO astrograph at full camera resolution. Extrapolating from this, minimum recommended guidescope power is 120x for the 300mm telephoto, 80x for the 200mm, and 55x for the 135mm.

The first telephoto lens of choice, especially recommended for beginners, is the 135mm F2.5 SMC Pentax. This lens has the Pentax K bayonet mount, and requires the K-EOS adapter for attachment to Canon EOS cameras. When the aperture is stopped down to 37mm using step-down filter rings, this lens produces incredibly tiny pinpoint star images from edge to edge. In this configuration, the lens is still a very fast F3.4. The lens is available on eBay for around $200. It must not be confused with the much cheaper SMC Takumar, often deceptively advertised as SMC Pentax Takumar, which has the M42 camera thread, and is plagued with unextinguishable blue chromatic aberration.

The best 200mm lens is precisely the older 200mm F4 SMC Takumar, which comes with the M42 camera thread, and requires the M42-EOS adapter. When stopped down to 37mm, at F5.4, it also produces perfect, small and round star images across the entire field. It has just a hint of chromatic aberration on very bright stars and, if highly enlarged by 400-800%, the stars in the very corners barely begin to show a touch of astigmatism. These lenses can be had on eBay in mint condition for around $70, and are probably the most price efficient optical instrument in the world. Take care not to confuse this lens with the 200mm F4 SMC Takumar 6x7 which has a different optical configuration, and which I have never tested. Also, the newer and much more expensive 200mm F4 SMC Pentax with the K mount is decisively inferior, showing small but annoying red chromatic aberration.

The next 200mm lens of excellent quality is the 200mm F4 Nikkor F which requires the Nikon F to EOS adapter. When stopped down to 37mm, F5.4, it is almost identical to the Takumar except that on highly enlarged images it shows a hint of coma in the distant corners. In excellent condition, this lens retails for around $200. Selecting between it and the 200mm Takumar was not an easy choice but, in the end, I chose the Takumar because it seemed to have slightly better contrast.

The one and only 300mm lens I tested is the Zeiss Tele-Tessar 300mm F4. There was no reason to test any other because, when stopped down to 49mm, F6.1, this lens is simply perfect, comparable to any APO on the market. It has no chromatic aberration, and no hint of star deformities in the corners. It requires the Contax-EOS adapter for attachment to the camera. I bought my lens in mint condition for $350 from Japan, but I see that some retailers are asking significantly more. This lens has only two drawbacks. One is its size and weight, which requires a sturdy support on the telescope. The other one is the inevitable and persistent regret that, because of chromatic aberration, the full 75mm aperture of this beautiful lens can not be used in full visible spectrum photography. However, I am convinced that its large aperture and fast F ratio would perform exceptionally well in three color or narrow band H-alpha and OIII photography.

M13, Hercules, Zeiss 49-300mm, exp 163 seconds, iso 800, Hoya MC UV(0) filter. Note the small galaxy NGC 6207 in
the 2 o'clock position from the great cluster. (Click the image to load full-sized version.)

  • ChipAtNight, Fox1971, macaddict and 6 others like this


gene williams
Jun 27 2015 09:57 PM



Is it possible to get good results on a Baader filter modifed Canon 450D and a good telephoto lens, or do I need to get a good APO?


No telephoto lens I tested, nor my TSAPO65Q, was suitable for use with a DSLR "clear glass" modified to include deep red and IR.

The APO showed no chromatic aberration at all with the addition of the Astronomik UV/IR cut clip filter (passing 380-680nm), but the telephoto lenses, even when stopped down, showed a tight bright red ring around all stars.

Your Baader filter passes 420-680nm and, in theory, a good APO should be able to focus that part of the spectrum with no chromatic aberration. However, as I have no actual experience with the Baader filter, I would suggest that you consult other members on the particular APO - Baader filter combination you have in mind. I can only guarantee that the TSAPO65Q would work very well.

I do not think telephoto lenses would be suitable for use with your modified camera.

Since I am interested in wide field astrophotography, I bought a new, unmodified, Canon 600D body for use with telephoto lenses.

Best Regards,


    • gene williams and radomir like this
vlad dumitrescu
Jun 28 2015 03:55 AM

Rudy, why didn t you include any L lenses from canon? I had a 70-200 f/4 that i used unstopped at 200 with awesome results. you can see here a lot of photos mostly shot with the f/4 version. 



Now i have the f2.8 version, and while the resolution is better it s under no circumstance as good as the f/4 one. I also tested 200 f/2.8 tele and it is one of the most perfect lens in existence, as well as the 135. Then you should have tried the 180mm nikkor ED, the old one, which is the favorite tool of a lot of astrophotographers. i also have the 300mm f4.5 non ED nikkor which is quite nice .


I was expecting a lot more of an article that says "the best telephoto lenses for astrophotography". 

I have used the canon 70-200 f2.8L ii and also the 100-400 f4.5/5.6 L  with excellent results. 

My canon is clear modded and I use a an Astronomik EOS-clip L filter to block the uv and ir.

the EOS-clip filters are compatible with all EF lenses but not with the EF-s. The latter are designed for crop sensor cameras and the back of the lens sticks too far into the body of the camera and would hit the EOS-clip filter. 


The 200f2.8 L is excellent - I am using it right now :)

he 100 f2.8 L macro is also very good. 


So so far the best that I have used are the 200f2.8L and the 400f5.6L. 

    • KevinS likes this
gene williams
Jun 28 2015 10:36 AM

Andysea, those are great images on your website. Were those taken with the Canon telephotos you spoke of, and the full spectrum modified camera and the clip in filter?  What I am trying to avoid is spending another $1,100 on a quality APO, and instead using my existing Nikkor 180mm ED lens with a Baader-modified Canon 450D that I just obtained.  

Sme of the wide field are. Here is a  recent ones taken with the canon xs and a lens.



The 70-200 f2.8 L2 and he 400f5.6 will however set you back way more than $1.100

gene williams
Jun 28 2015 02:22 PM

Nice image, andysea. I am not really looking at buying anything else, though.  I would like to make this work with the Nikkor 180mm ED (i.e., what I have versus what I cannot have...lol).  


I have no experience with that lens, Jerry Lodriguss however published a review of that lens on his website http://www.astropix....NIKON_180MM.HTM

Vlad and Andy,


The article was based on the numerous lenses with which I have personal experience - that is naturally limited.


The criterion I used in evaluating lenses was optical perfection with no reservations.


The lenses I selected are all affordable prime lenses, easily available on the second-hand market, and adaptable to the EOS system.


Also, when used as recommended, and properly guided at full camera resolution, they are all comparable to a field-corrected APO, producing perfect images from edge to edge which can be easily cropped 25% with no evidence of aberrations. I think they are an outstanding value for any wide-field astrophotographer, and are particularly suitable for newcomers.


The lenses I listed are certainly not the ONLY exceptional lenses made over the years. For example, a friend recently recommended Pentax 6x7 prime lenses which were designed for a large format flat field, and are also adaptable to the EOS system. Several days ago another member posted a stunning telephoto image of the Snake Nebula, Barnard 72, taken with a Canon lens which costs $12,000.


I think the readers would welcome contributions from other members' experiences.



    • gene williams likes this

OK guys TOS  rule number one "  Posts that are not respectful of other individuals (be they members or not) are not welcome here."


You got a criticism fine say it politely, and too the point.


No accusations, no bashing.


The OP  admits he limited experience with lenses other than what he has.


If you don't like that article that's your right as a member.


Thank you the moderating team

Michael Covington
Jun 29 2015 07:41 PM

There are quite a few other excellent lenses out there, and nowadays, quite a few that can be used wide open.
Canon 300/4 ED IF AF (non-IS)
Sigma 105/2.8 DG EX Macro (very sharp at infinity)
Nikon 300/4 ED IF

Sigma 50/2.8 DG Macro (not a telephoto, but good)

I hear great things about the Canon 200/2.8 L but do not have one.

Standards have risen in recent years.  A lot of lenses today are better than anything money could buy in 1980.

Michael Covington
Jun 29 2015 07:42 PM

BTW, the 300-mm Tele-Tessar you describe -- what camera was it made for?  Zeiss Jena or Oberkochen?  There have been a lot of Tele-Tessars over the years.

Michael Covington
Jun 29 2015 07:44 PM

Also, I used to have a Nikon 180/2.8 ED IF AF and 300/4 ED IF AF.  These were just a tad less sharp at the corners than their Canon competition, but certainly extremely sharp all over the field if closed down one stop or even half a stop.

It is good to know that the 200/4 SMC Takumar is good.

The Olympus Zuiko 180/2.8 and 100/2.8 impressed me in the 1980s, but in the digital era they are not so sharp.  Digital sensors are roughly 5 times as sharp as 400-speed film.  Lots of older lenses no longer satisfy.

Got it! I wanted to add my experience with some lenses that I thought worthy of being considered too, and some of the equipment that I have used.


I've tested some of the old Pentax 6x7 lenses with a friend. They seem to be really good for NB work. While they provide a very large flat field we noticed some CA. Part of it might be that they were designed for film photography and modern digital sensor are far more demanding in terms of optical quality.

Michael Covington
Jun 29 2015 07:47 PM

I have an old 135/2.5 Takumar that is not bad at all, for the price.  Pentax seems to have put more emphasis than others on keeping the resolution uniform all over the field.

    • obin robinson likes this

How about the sigma 50mm f1.4 Art? I heard it's very sharp and well corrected.

Yuri toropin tests a bunch of lenses on Flickr which is a great source. From my experience, the toughest test on a lense is its ability to function wide open. 645 lenses such as the mamiya apo line and pentax edif can operate within these conditions without vignetting on apsc sensors. If you can tolerate vignetting, there are many normal 35mm lenses that are great wide open. I've seen several listed but here are more to consider. Samyang 135mm f2, 100mm f2.8, and asperical 16mm f2.8. The sigma 150mm f2.8 tests very well, zeiss 135mm apo sonnar, and leica 180mm f3.5 apo all proven performers on star tests.

    • Deus_Ex_Mamiya and Michael Covington like this

Do you have a link to Yuri's photo stream? I would love to see his test images.



In general, prime telephotos should outperform zooms. (And cost less too)


I just purchased a very lightly used Canon 200mm F2.8L II USM for $620 from a great online dealer and can't wait for an opportunity to try it out with my Astronomik CLS clip on a T4i at a dark site. That whole rig comes to about $1200, minus the mount. (AVX). That's a cheap, fun date for AP.


From my purchase research, I found a consensus that stopping down optimizes sharpness but the diaphragm will make nine diffraction spikes when stopped down. It's a trade off. This seems to be the norm for telephotos. Diffraction from the cheap EF-s kit zoom lens was uneven. 


Stellarium has a great viewport feature that allows you to preview different lens and sensor combinations on DSO's before you decide on the focal length you want.


Also type the lens you are interested in into the search window on Astrobin to see examples shot with that lens. 

    • jayar likes this

No one yet mentioned a zoom lens, I had an opportunity to test my Canon 24-105L f/4 on M31 Andromeda Galaxy and received wonderful results with Canon 60D unmoded, I set it to 105mm, No vignatting, slight coma on the corners and no false color on bright stars.
Looking forward to allow purchasing the Canon 200mm f/2.8L II USM.



The difference between modern and old telephoto lenses is probably similar to the difference between my APO and an old Jaegers 5in F5. Yet the Jaegers becomes essentially color free when stopped down to 3in. It would not surprise me if modern lenses were useable at full aperture. But, since fast 300mm ED lenses are beyond my toy budget, I would appreciate seeing magnified center and corner test images of actual star fields.


Lior, I have done a lot of reading on modern zoom lenses. It seems they are now quite comparable in quality to prime lenses. However, all the reviews were made by nature and sports photographers, and I would like to find out more about their performance in astrophotography. Please send your photos of  the Andromeda galaxy.


MCovington, my Zeiss 300/4 is the full thickness barrel version, made in West Germany, serial number 5990836. I understand the optical design is quite old. When stopped down to 49mm it really is indistinguishable from an APO, except it shows red chromatic aberration with modified cameras even with the UV/IR block or CLS-CCD filter.


KevinS, in my experience stopping down dramatically improves image quality in terms of chromatic aberration, coma and astigmatism. 30-35% diameter reduction is usually necessary on "good" lenses. Some lenses are incurable. Using the lens's diaphragm interferes with the light path and results in diffraction spikes which I find unattractive. You will get perfectly round star images if you use an aperture stop in front of the lens made of a series of filter thread step-down rings.



    • KevinS likes this

Thanks for the fine article and the thought you put into it. I've recently started using 135 and 200mm lenses from the 1970s with my mono CCD and they've proven very useful for imaging large emission nebulae. I really like how they augment my longer focal length scopes.


Although your target audience is beginning DSLR imagers, much of your advice also applies to using lenses with CCD cameras. One difference worth pointing out is for those who image using narrowband filters. Chromatic aberration is almost eliminated in narrowband, so lenses with that problem may be fine performers.


This summer I'm going to try the lenses out for LRGB images to see how they perform.

OK guys TOS  rule number one "  Posts that are not respectful of other individuals (be they members or not) are not welcome here."


You got a criticism fine say it politely, and too the point.


No accusations, no bashing.


The OP  admits he limited experience with lenses other than what he has.


If you don't like that article that's your right as a member.


Thank you the moderating team

I recommend the author change the title of his article from "The Best Telephoto Lenses...." to "Some Inexpensive Telephoto Lenses I Have Tested..."   The original title generates a claim and expectation in the reader that his article can't support that leads to reader frustration and just more questions; why didn't you test this one or do this etc. etc..     Ron

    • Jimmy462 likes this

Interesting that ancient, low-tech (no ED glass, no special coatings) non-apo telephotos could produce decent results compared to something modern.  Of the old teles I've had, Nikon's 400mm f/3.5 was decent, Olympus's 300mm f/4.5 was good (it had a precursor to ED glass) Pentax's 300mm Takumar was TERRIBLE, Pentax's 500mm was terrible, Nikon's 135 f/2.8 Q was ok, and Sigma's 400mm f/5.6 "apo" was satisfactory.  The main problem with the old lenses is spherical aberration and colour error, especially pronounced on digital sensors.  I'm thinking a modern (but expensive) Nikon 200mm f/2.0, 300mm f/4 or f/2.8 or a Borg telephoto/telescope would all be very good.

Do you have a link to Yuri's photo stream? I would love to see his test images.



Sure, if you scroll through his page there are quite a few lens tests on stars https://www.flickr.c...hotos/ytoropin/

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