Suitability of Canon 50mm f1.8 Lens for Astrophotography

[Knight of Clear Skies]

Hi all. Up to now I've been using the kit lens supplied with my Canon 1100D for constellation imaging, at 18mm and f3.5. I've produced some OK results, but my attempt to stack some images have been failures due to tripod shake and wispy cloud scudding across between frames. Here are a few of my images:

(These are all 30 second exposures. I used a torch to light up the domes at Caradon Observatory, to make a new banner image for the website.)

I was wondering if I'd better results with a 50mm f1.8 lens, due to the lower f-number. However, with the higher magnification I guess trailing would become apparent more quickly, and I'd be restricted to even shorter exposures. Would this be a worthwhile trade-off? What exposure length could I use before trailing became obvious?

Any help would be appreciated.

[Leveye]

Seems you have some wonderfully clear and light pollution free skies over there. Personally i would invest in a computerised tracking mount.

[Knight of Clear Skies]

The top image was taken in Menorca last year, the bottom two while visiting Cornwall over Christmas in slightly hazy conditions, dodging between clouds and showers. Unfortunately I live in light-polluted Hertfordshire, almost within sight of London. I don't have the budget for a tracking mount at the moment. I'm hoping to get some meaningful practise at imaging up here, so I can make the most of my time when visiting Cornwall, which I do fairly regularly.

[Pete Presland]

i did some test exposures the other night to test the different fields of view size between the 18mm F3.5 and the 50mm F1.8 for imaging meteors

the results maybe of interest regarding the amount of stars visible.

the exposure on the left is the 50mm at 5 secs, the right is 18mm at 5 secs. no processing just converted to JPEG's to upload here, so ignore the obvious flaws!

i dont think you would get away with much more than 15 secs to be honest 

[Amra]

The nifty fifty is excellent, but you need tracking to get the most out of it.

[Beulah]

This nifty fifty is on my wish list - you had great results with it, Pete.

[Pete Presland]

This nifty fifty is on my wish list - you had great results with it, Pete.

i wish  i only took these because my attempts at imaging meteors has been such a failure. i had a go at the Geminids and the Quadrantids, 1 meteor trail in several hundred exposures, despite seeing quite a few go through the field of view!  

[Adamar98]

Its a great little lens! Its a vital part of my kit. I would say this lens has given me more pleasure in astrophotography than my scope! The longest exposures I got where around 15 second before trailing. Once you introduce tracking its belting! Best £80 ive spent in a long time. Heres two images taken with it. Both with tracking and 300 second subs. stopped down to f4.

[Knight of Clear Skies]

i dont think you would get away with much more than 15 secs to be honest 

Thanks for the test images, the 50mm is showing a lot more stars. If I can get 15 second exposures out of it then I should be able to get some better results than with the kit lens.

Its a great little lens! Its a vital part of my kit. I would say this lens has given me more pleasure in astrophotography than my scope! The longest exposures I got where around 15 second before trailing. Once you introduce tracking its belting! Best £80 ive spent in a long time. Heres two images taken with it. Both with tracking and 300 second subs. stopped down to f4.

Lovely images. What was the advantage of stopping down to f4 please?

Tracking is the real solution, and I should get some chances to play with a tracking mount down in Cornwall, but for the meantime I will be practising with a fixed tripod. Does anyone have any experience of using this lens on a fixed tripod please, and stacking the images?

[Adamar98]

I tend to stop down from wide open to improve coma, astigmatism and chromatic aberrations enough to produce usable stars. The more I stop down the better the stars tend to be.

[Alien 13]

l

I tend to stop down from wide open to improve coma, astigmatism and chromatic aberrations enough to produce usable stars. The more I stop down the better the stars tend to be.

I agree although its not too bad one stop down another advantage of going to F4 is its a bit more forgiving with focus which is not the easiest thing to get right with this lens in manual mode.

Alan

[Knight of Clear Skies]

I tend to stop down from wide open to improve coma, astigmatism and chromatic aberrations enough to produce usable stars. The more I stop down the better the stars tend to be.

Thanks, I guess this wouldn't be such an issue with short exposures, as my Milky Way isn't exactly leaping off the screen.

I agree although its not too bad one stop down another advantage of going to F4 is its a bit more forgiving with focus which is not the easiest thing to get right with this lens in manual mode.

Alan

Getting focus on the Menorca shot was a nightmare, as there was nothing bright enough to show up on live-view. I need to experiment with controlling my camera from my laptop as well.

[Pete Presland]

when using the laptop i always examine the images to check for focus. but when out in the field i check the focus by zooming in on an image and if the stars are smaller than the white square on the view screen (this square gets smaller the more you zoom in) the focus is normally pretty good.

[JKB]

Whilst the Nifty Fifty is ok, the Canon 40mm STM is awesome, Focus is really crisp. 

Cheers

Jamie

ps, will upload some pics later

[Beulah]

Whilst the Nifty Fifty is ok, the Canon 40mm STM is awesome, Focus is really crisp. 

Cheers

Jamie

ps, will upload some pics later

Yes please.

[jgs001]

The 50mm f/1.8 is great, but you really do need to stop it down to at least f/4 if not lower to get the optics to work the best. Otherwise the coma is really dire. Yes at f/1.8 you let in some serious light, but you'll lost something like the outer 30-40% of the image. Even at f/3.5 you lose a fair amount to coma. The 50mm f/1.4 is much better with the coma, at f/3.5 there's none visible, and the red CA across the middle is dealable with. 

However, unless you're tracking, you're going to be really hard pushed to use it. On a crop sensor camera, you're looking at about 8 second exposures to avoid trailing... you may be able to get away with a bit longer... but as a rule of thumb. With tracking, it's short enough and light enough, that on any decent mount, you should be able to hit 5 minute exposures easily, and at that sort of exposure time, even my non modded Canon 450d is pulling in plenty of Ha. 

[Physicist13]

Here's  a link to a pic of Orion using the 50mm at f2.2...showing "dire" coma as John says! It has the advantage that I can put a cls clip filter in, which on the Ef-S lenses you can't.

[Physicist13]

Here's  a link to a pic of Orion using the 50mm at f2.2...showing "dire" coma as John says! It has the advantage that I can put a cls clip filter in, which on the Ef-S lenses you can't.

with the link wld be useful!! http://flic.kr/p/j66bKN

[Astrosurf]

It's a shame I can't see your images here at work as they're blocked. I'll have a look when I get home. I don't know what your budget might extend to, but if you're not interested in a scope, have you thought about an Astrotrac? They're absolutely marvellous and, I believe, will take little refractors like 80mm. Melsky produces truly wonderful images with his Astrotrac. He uses a modded Canon EOS 600D and usually a 200mm lens. If you do go for one (try second-hand of course!) then it must come with the Astrotrac polarfinder. There are other models that do the same as the Astrotrac. See here:

http://www.ioastronomy.co.uk/2013/07/astrotrac-vs-skytracker-vs-polarie/

You'll also need a sturdy tripod and a good ball head joint.

Alexxx

[JB80]

I use the Polarie with mine stopped down to f/4.

You can see some pics here...

http://astropaz.weebly.com/pictures.html

There is also my attempt at a review for the Polarie on another page, just scroll down.

[stargazerlily]

I have a nifty 50mm which I use with a Canon 1000D.  As John said earlier, you do need to stop the lens down to f/4.  I've taken some images of Orion just using the Camera + nifty 50mm on a tripod but using a maximum exposure time of 4 to 5 seconds.  Any longer then 5 seconds and I'm getting star trails.  My problem is getting a good focus ... poor eye sight etc.

Cheers

Pete

[Physicist13]

yep you do need to stop it dwn, but it a compromise as to what distortions you are willing to take vs the possibility of capturing something faint at f2.2, say, with short exp. Focus is a pain with all these camera lenses as they have no manual focus lock and do tend to slip I've noticed. I use the liveview to zoom in on a bright star and focus by minimising the star size. Then being v careful not to go anywhere near the focus ring.

Pat

[jgs001]

There is a little trick you can do to prevent the nifty fifty from changing focus... It does mean you need to change the way the camera operates focus, and this may be tricky to get used to for normal photography, but it does work.

Set the camera to use rear button focusing, then, once focused in manual mode, set the lens to auto focus. It sounds counter intuitive to do that, but, as the shutter button no longer controls focusing, when the exposure is triggered by whatever means, the lens does not focus. The AF functions are then controlled from the * button on the rear of the camera. I've been using this trick for ages and it works really well... as long, of course, as you're not using a lens with USM focusing, as they allow for full time manual focusing. Personally, I find that rear button focusing works brilliantly for me, and I leave my camera setup that way all the time. My thumb controls AF, and my finger controls the shutter release...

[Adamar98]

I had no idea you could do that. I'll be trying it when I get home tonight. Cheers for that little tip!

[GeohanSolo]

Whilst the Nifty Fifty is ok, the Canon 40mm STM is awesome, Focus is really crisp. 

Cheers

Jamie

ps, will upload some pics later

I second this. The f/2.8 40 mm "pancake" STM is a much better build and quality than the plastic f/1.8 50 mm. But getting the pancake, maybe the f/1.4 50 mm would be a better choice?

I have an f/2.8 11-16 mm Tokina lens that can get away with 20 and 25 second exposures, where as my f/5.6 280 mm only takes 2 seconds to make star trails.