Jonathan's blog

I love photography, and I have an interest in astrophysics and astronomy. It only makes sense to combine them, and have fun with astrophotography. But which equipment is best for the beginner without breaking the bank? Let’s explore the options.

Some interesting photographs can be captured using a wide-angle lens to view the whole sky, but here I am specifically talking about long, telescope-like lenses. There are three solutions that I have at my disposal:

• Meade 60AZ 700mm f/11 telescope, with T-mount adapter for 35mm SLR or DSLR
• Tamron 70-300mm f/4-5.6 telephoto lens, native mount on DSLR with 2× teleconverter to make it a 600mm f/11
• Tokina 400mm f/5.6 telephoto lens, native mount on 35mm SLR with adpater for DSLR and 2× teleconverter to make it a 800mm f/11

So the “zoomiest” lens is the Tokina but that isn’t the only factor. Which lens is sharpest? What about chromatic aberration? What about other things affecting practical use for astrophotography?

First let me say a few words about each lens (and offer my apologies for the quality of the photos of the lenses – as you can see, my DSLR is in each picture so I was using my phone).

Meade 60AZ

The Meade 60AZ is an inexpensive 700mm telescope. The front element is 60mm in diameter, making it an f/11.7. There’s no variable aperture. It has the usual 1.25″ eyepiece fitting, so it’s easy to get hold of an adapter to turn this into a T-mount fitting. Once you’ve got T-mount, well, Bob’s your uncle, and you can adapt T-mount to anything else – including 35mm and digital SLR cameras, such as my AE-1P, EOS 450D and EOS 300. I bought mine from a car boot sale for £15, and then paid about £20 for the adapter to mount the camera.

Meade 60AZ on Canon 450D

It has an optically simple design with few elements, so chromatic, comatic and spherical aberrations may not be so well corrected for. This isn’t important for viewing by eye with an eyepiece, but aberrations show up more significantly in photographs that can be studied. Technically it is not a telephoto lens, since it does not have a telephoto group, and is correctly known as a long-focus lens.

Being a telescope, it comes with its own tripod which is a little flimsy, but easily capable of taking the weight of a camera.

Tamron 70-300mm

The Tamron 70-300mm is an inexpensive autofocus SLR zoom lens, offering a maximum aperture at 300mm of f/5.6. It mounts natively to the Canon EF mount, for use with 35mm and digital SLR cameras, including my EOS 450D and EOS 300. The 13 elements are coated to reduce flare and correct for various aberrations. My sample was bundled with my 450D at Jessops, but it costs around £100 new at the time of writing. I bought a Kenko Teleplus teleconverter for £30, second hand.

Tamron 70-300mm on Canon 450D

Autofocus is practically useless for astrophotography since there isn’t enough available light. On this lens, the focus ring is quite sensitive, undamped, and hard to use accurately. This will count against it in practical use.

Using a 2× teleconverter will double the effective focal length to almost match the Meade telescope, at the cost of a couple of stops of light and some sharpness – but still faster than the telescope.

This lens does not come with a tripod mounting collar but should be used with one, since the fully-extended lens with teleconverter is quite heavy, and unstable when the tripod attaches to the camera.

Tokina 400mm

The Tokina 400mm is a fixed focal length prime lens, with a maximum aperture of f/5.6. With a 2× teleconverter this gives me the longest effective focal length at 800mm while still being faster than the Meade telescope. It’s a manual focus lens with a large and well-damped focus ring which actually makes it easier to use than its contemporary rival, the Tamron. I paid £50 for this lens, second hand, and the Super Paragon teleconverter was about a fiver, I think.

Tokina 400mm on Canon 450D

It mounts natively to Canon FD-mount manual focus cameras like my AE-1P, but will work with Canon EF-mount EOS cameras with an adapter, which I wrote about recently. This adapter has the effect of making the lens a bit zoomier. I haven’t exactly measured the amount, but it could make this 800mm lens produce an image like a 900mm. We shall see.

This lens also does not come with a tripod mounting collar but should be used with one for best effect, because it is long, metal and heavy. They sure don’t make lenses like they used to.

Sample images

This article is about astrophotography really, but taking test photos of the moon or other celestial objects means carrying equipment to a dark place. I’m not sure I can be bothered to carry these three heavy lenses and two tripods and other accessories out at night, so for now you’ll have to make do with these images of the chimney at Frenchay Hospital, which is about one mile away. This is a city, so the atmosphere is quite hazy.

These pictures were taken with a Canon EOS 450D. The main images are exactly as they came out of the camera – no editing. The second images are cropped around the top of the chimney to show fine detail.

Meade 60AZ

Meade 60AZ

It’s immediately obvious that the image from the Meade telescope suffers from very poor contrast and colour saturation. This is perhaps obvious given its inexpensive and crudely coated elements. It might be possible to improve the contrast by using filters and shooting in black & white, since colour isn’t always important in astrophotography.

In its defence, the sharpness is good and I’m frankly shocked at how small the chromatic aberration is, given that this is a cheap 2-element lens.

Tamron 70-300mm

Tamron 70-300mm

The Tamron 70-300mm, a modern multi-coated lens, has no such problems with colour and contrast. The colours are vibrant and bold. However, it suffers badly from chromatic aberration. We might expect this from a cheap zoom lens – the effect will be less prominent with a fixed focal length prime lens.

As before, it might be possible to reduce the effect of chromatic aberration by using a coloured filter and shooting in black & white.

Tokina 400mm

Tokina 400mm

It’s immediately obvious that the Tokina 400mm is the zoomiest lens, with its teleconverter and FD-EF converter to mount it on the 450D. The colours and contrast are good, especially for a lens manufactured in the 1970-1980s.

The effect of chromatic aberration is also extremely small, presumably because it is a fixed focal length prime lens. I think the overall image quality is best out of the three lenses tested here.

Summary

The Tokina 400mm definitely seems to be the most useful for astrophotography and lunar photography. It has the longest effective focal length, the best sharpness, the best chromatic aberration and reasonably good contrast. Its manual focus ring is easy to use

Don’t forget that these images aren’t the best that each lens can produce – they are the lowest common denominator of what each lens can do. With careful processing, the images could be sharpened and have their contrast boosted. For some subjects, it might be appropriate to stack the images. For certain images, coloured or other filters could be used to work around the effect of chromatic aberration and atmospheric haze.

In the past, I experimented with a catadioptic mirror lens but the results were not great. In theory, mirror lenses should be well suited to astrophotography, so perhaps I had a bad sample. I also wrote some thoughts on other types of long-focus lenses for general use, and some of it might be relevant to astrophotography.

That’s enough discussion of lenses. I’m now waiting for a clear summer’s night when I can go for a short drive out of the city and hopefully capture some great images of the moon, and maybe other things in the sky. I should probably read up on astronomy so I know what to point the camera at!

I quite enjoy macro photography. When I used to use my Fuji S9600 as my main camera, it had a super macro mode, which allowed me to focus on objects as close as 1cm. That was pretty handy for macro shots and the results were generally good – such as this disgusting pupa.

Since swapping the S9600 for a Canon EOS 450D DSLR, I don’t have a macro facility. The best I could get was my Tamron 70-300mm telephoto zoom lens which allowed 1:2 magnification at full zoom. But the subject had to be at least 1.5m from the camera and image quality wasn’t great, so it wasn’t really a solution.

I bought a set of EF mount macro extension tubes from eBay. These sort of replicated the behaviour of the S9600, by allowing the camera to focus closer. By spacing the lens further from the camera body, it’s possible to focus down to just a few millimetres away from the end of the lens, so tiny objects can fill the frame.

However, as EF lenses are electronically controlled, you lose autofocus and the ability to shoot with the aperture anything other than wide open. Naturally, the depth of field is then very shallow. Sometimes it works, like in this photo of a pound coin, but it’s quite frustrating not being able to stop down.

The other disadvantage of “cheating” at macro by focusing closer is that it’s hard to get light onto your subject, because the snout of the lens casts a shadow. When I use my macro LED ring flash, some of the objects I photograph have to be so close to the end of the camera that they are within the ring flash and hence get no light.

So I decided the only real solution would be to buy a proper macro lens with 1:1 magnification. I considered the Canon 60mm macro as the cheapest entry-level macro lens, but unfortunately it’s EF-S mount and can’t be used on 35mm SLRs, such as my EOS 300. If I’m going to shell out for a lens, I want it to work on all my cameras.

The next lens up in Canon’s range is the 100mm macro, which is EF mount, but is unfortunately quite a bit more expensive. I watched a few second hand lenses on eBay but the auctions always closed for prices significantly higher than I was willing to pay – especially as macro photography is only an occasional treat for me.

The two main rivals of the Canon 100mm are the Tamron 90mm and the Sigma 105mm. The Sigmas are rarer but there were plenty of Tamrons on eBay. The first few auctions for the 90mm finished at quite high prices but eventually I found one ending at an awkward time and won the auction for a bargain price. The lens is second hand but very new; mint condition and boxed in all original packaging.

The main disadvantage of the Tamron compared against the Canon is that the Canon has an ultrasonic autofocus motor, and full-time-manual focussing. As nice as those things are, they weren’t worth an extra £150 to me. The Tamron lens flips between manual and autofocus by sliding the whole focus ring back and forth, which is much nicer than fumbling for a small switch on the side of the lens barrel.

The Tamron 90mm feels solid compared with some of my other lenses – most of them budget ones. It’s reassuringly heavy and feels like an expensive lens. The autofocus is quite slow and quite loud, but this doesn’t matter. When I’m composing a macro scene, I can take all the time I like.

The main gripe is that the lens barrel extends by about two inches when focussing. You have to be careful not to bump into your subject if you are working at close range.

I’ve only owned the lens for a few hours, but I can see it’s a fantastic lens. The images are very sharp and almost completely free from any aberration. When I have some time to experiment with some small subjects, I’ll see what I can come up with. But for the time being, here’s a picture of a piece of Velcro.

Recently I bought a Canon EOS 450D from Jessops. They were running a bundle deal, and it came with a Canon 18-55mm lens and a Tamron 70-300mm lens.

The long zoom was quite an important aspect to me, since I had upgraded from a Fuji S9600, with a huge range in focal lengths.

I’ve now owned the camera for a couple of weeks and I’ve had a chance to play with it a bit. Of course a fortnight isn’t nearly enough time to fully understand everything about a complicated device such as a DSLR, but I’ve tried a few things with it.

This review in particular is about the Tamron lens.

Obviously you don’t expect wonders from the cheapest lens in its class, but I am still quite disappointed. The S9600 was a jack of all trades (and master of none) and showed weaknesses at both ends of its range of focal lengths. That said, the whole camera cost around £200 and can now be bought for significantly less than £200. I think that represents fantastic value for money. During my 23-month ownership of it, I’ve taken about 10,000 photos. On average, that’s more than one every two hours!

Given that the Tamron lens on its own costs almost as much as the entire Fuji camera, I had hoped for significantly better images. Never mind.

At the shorter focal lengths, it’s OK. Nothing to write home about, but it’s fine. I took these self portraits at a focal length of 70mm and they seem OK.

But when you start to zoom in, the problems get worse. Some of this should have been obvious from reading the box – its largest aperture at 300mm is f/5.6, which is pretty slow. To make matters worse, there is no image stabilisation. You can’t complain about this – it says it on the box and if you want a fast lens, you have to pay more for it.

But I wasn’t at all pleased with the optical quality at 300mm. Take, for example, this photo of some distant horses. The first photo is the full image, and the second one has been cropped to show detail. Neither photo has had any other editing.

Horses in Hartshill

Horses in Hartshill

The first thing you might see is that the focus is very soft. It wasn’t camera shake because the sun was out and I used a tripod. The autofocus just seems to struggle at long focal lengths.

But then look at the chromatic aberration around the white horses. It makes the image look pretty terrible.

I also tried taking some photos of the moon last night, also at 300mm. As before with the horses, it couldn’t autofocus properly. The low light conditions made it much worse and the image was so blurry that there was no definiton on the surface of the moon.

I flipped the lens into manual focus mode where I was able to hugely improve the focussing. Unfortunately it seems in manual focus, as you approach infinite focus, the moon becomes sharper, but for the last little bit of the travel the lens goes beyond infinite focus and makes a garbage image. Not good at all.

In the end, this is the best I could manage. Here I used manual focus, spot metering and I’ve cropped the image afterwards.

The moon

It’s OK, but I’ve managed a better photo of the moon with my S9600.

I’m not sure if my lens in particular is faulty, or if these lenses are all equally bad. But I am very unimpressed with the results, even for a budget lens. Given how much more the 450D and this lens cost than the S9600, there is no excuse.

Tamron’s own website says:

Perfect 2^nd lens for your DSLR kit

So they are certainly admitting that it shouldn’t be your primary lens. However I would also hesitate to say it’s “perfect” for anything.

My advice would be to avoid this lens, unless you’re on a particularly tight budget, or you don’t plan to use the higher end of the zoom range. Be prepared to switch off the autofocus, and focus manually if sharpness matters. Get a Canon telephoto lens if you can.

Update

I may have been a bit hasty in my critical review. As I said in my comment below, I had another go today at taking a few photos with the lens.

First here’s a chimney stack at full zoom, and a cropped version below.

Chimney stack at 300mm

Chimney stack at 300mm (crop)

As you can see, the focus is very sharp. There is a little aberration, but that’s expected from a cheap lens.

This photo of the seagull was also taken at full zoom. The autofocus can be pretty slow going from one end of the focus to the other, but if you focus on a similar object first, it’s much faster. In this case, fast enough to get a lock on a swooping seagull.

Seagull

Yes, it’s not perfect – but it’s acceptable for the price. I’m going to keep this lens and see what I can achieve with it