Lens for lunar/basic photography

[lancerde]

Hi folks

I want a lens for my EOS1100D to take basic lunar and general pictures of the night sky. Any suggestions?

[fredster]

Camera lenses can be truly expensive. To get some merely average glass will cost £300 upwards. I only know because i spent weeks bidding on Ebay for average quality lenses to go with my 1000D. There's some real budget lenses like the Canon 75-300 and Tamron 70-300, get them well under £100 secondhand. Also the Sigma 70-300 DG. But all three in the scheme of things are poor lenses. Low end optics, superb slow AF, noisy and poor build. And for lunar shots they get real soft 200mm onwards. Even stopping down to F11 doesn't help much. I tried them all.

Came close to blowing £300+ on secondhand examples of the Tamron 70-300 VC (rave reviews), Canon 70-300 IS (much better than the 75-300) and Sigma 70-300 OS. Then realised that sort of money buys a secondhand EQ3 with a Skymax 102, which would give lunar shots not possible with those lenses, and also another scope setup to go with my Startravel 120.

Downside of course is a still do not have a long reach telephoto lens for the 1000D. But busy saving for a decent lens that will last. Set my heart on the Canon 70-200 F4 L, which sell for roughly £400 secondhand. But that's proper premium glass according to the reviews and with decent AF speed.

[JamesF]

The 200mm f2.8L is well-regarded, but not exactly cheap. Otherwise you can get some quite reasonable widefield images with the kit 18-55mm lens -- have a look in the widefield/other section for examples. I wouldn't be in the least surprised if it were cheaper to buy a telescope to image with than a new lens though.

James

[lancerde]

Thanks guys.

[jgs001]

A nifty fifty is under £100 and is a superb optic for the money (if you ignore all the plastic). Works great for widefields (if you can track it). The Canon EF-S 55-250 is a capable performer, and again is cheap. The newer

Tamron 70-300mm f4-5.6 SP Di VC USD

is supposed to be very good...

[JamesF]

I've noticed the older metal-bodied nifty fifties go for quite a premium second hand even on the price of a new plastic-bodied one. Are they optically better as well, or are people paying £40 or £50 more for the old model just to have a metal body?

James

[fredster]

Nifty Fifty is superb. Currently i have that plus the 18-55 IS kit lens and the 55-200 non IS. The 50mm F1.8 II is in a different league to the others for optical quality and frames most constellations very well.

I have heard good things about the EFS 55-250 IS as well, very tempting to swap 55-200 for one. The rotating front element (awkward for filters) and no full time manual focus were what put me off. Which is why the Tamron 70-300 VC is so appealing, get all the frilly bits for a good price. And the optics are better than Canon's 70-300 IS USM.

[Shibby]

As for lunar, have you thought about using your DOB at prime focus?

[lancerde]

Thanks again. What is prime focus?

[JamesF]

Prime focus imaging is when you fit the camera to the scope directly (instead of the eyepiece) and place the camera sensor at the image plane of the scope. As opposed to imaging through the eyepiece ("afocal" imaging) for instance.

James

[mikehab]

One other option worth thinking about is using old lenses originally designed / shipped with other makes of camera - for eample Olympus OM series, and using them with your Canon EOS with an appropriate adapter ring. For example - for wide-field (not luna, planetary or DSO) the old Olympus Zuiko 50mm F1.8 prime lens is a fantastic, excellent quality & v. fast lens - one of the best, and you can easily pick up a good one on ebay for <£30, and the adaptor ring for <£10. It'll be manual focus as these old lenses were around long before auto-focus even existed, but for wide-field astro photography that's not a problem - you don't really need AF anyway. I defy anyone to get a brand new AF F1.8 lens for <£30 these days - so using old (fantastic quality) lenses like this might be worth a punt...

[lancerde]

Thanks for the explanation James.

I had not thought about using an old SLR lens. I assumed that they would not work with a DSLR. You are quite right the Zuiko were great lenses. My old SLR is a Minolta I assume I could get an adapter and use the lenses from this? Thanks mikehab

[JamesF]

Is it correct to say that the field of view with a 50mm lens will be about 2.5 times less in linear dimension than an 18mm lens? Or is it just not that simple?

James

[GlassWalker]

I treat the moon and other objects separately. Looking it up, the 10 inch LightBridge (1270mm) appears to be near enough the right focal length that, if you put a 1100D on it, you'd get the whole moon in one shot. Aiming isn't too bad as at that magnification it isn't too fast. I've used my Nexstar 4SE for lunar shots (1325mm) manually pointing it. You can always fit the barlow if you want to try getting more detail.

Lenses aren't so much use for the moon unless you want to get the moon in context with the landscape. I assume the 1100D came as a kit, and that'll be adequate unless you want to spend a lot more.

What other lenses really depends on what you want to do with them. Unless you have a tracking mount, preferably equatorial, then you better be a fan of star trails if you try longer exposures.

The Canon 50mm f/1.8 lenses are believed to be identical optically between the better built mk1 and the current mk2. For longer-ish focal length lenses, the angle of view is inversely proportional to the focal length. It doesn't quite hold out at wide angles, but generally close enough at an approximation. On a calculator this gives a 50mm a horizontal FoV of 25.4 degrees, and 18mm a FoV of 64 degrees. So doesn't quite match the ratio of focal lengths.