Need help on choosing cheap lenses

[IWatchStars]

Hi,

I´m currently working on building a motorized barndoor tracker for my Canon 700D/T5i. I'm planning on capturing the brighter dso's like Andromeda/Orion/Pleiades. The camera kit I bought included a 18-55 f3.5-5.6 lens, but I don't think this lens can get the dso's close enough, and also I don't think it's good for widefield milky way shots because of it's small aperture/poor light gathering capability. 

I'm thinking of buying the following lens for widefield milky way shots: LINK

I think this is a pretty solid choice, any good(maby cheaper) alternatives?

Also i'm planning to get a cheap zoom lens with enough reach/ for dso's. The Canon EF 75-300mm f/4-5.6  is very cheap and i'm considering it. Is it any good for the brighter dso's? Are there better alternatives for around the same price? 

[PeterCPC]

The Samyang is a good lens - as for cheaper alternatives  the M42 super takumar lenses are good if you can find what you want.

Peter

[Alien 13]

There are a lot of old M42 prime lenses in the 135mm to 200mm range that perform quite well you will also need an EOS to M42 adapter that is quoted as "infinity focus" there are optional chipped versions too that allow metering and focus confirm beep in Manual or AV mode.

New lenses might include the nifty fifty (50mm F1.8, there is a new STM version now which is much better).

Alan

[pete_l]

A barn door tracker won't give you the best tracking performance. They are also difficult to polar align with much accuracy and if it is mounted on top of a tripod, it might not be very stable, either.

Before you embark on spending $hundreds, I'd try running your tracker with the existing lens: 50mm is a good place to start experimenting. You might be surprised how good the results are. And if you do find that the barndoor doesn't live up to expectations then think of all the money you've saved

It's also worth bearing in mind that a long lens will put more torque (leverage) on the ball-joint on your barndoor. So unless you've bout an expensive one, you could get slippage of the camera. Longer focal length lenses, with their higher magnification, will also require more accurate tracking and alignment to get pinpoint stars and therefore not lose sensitivity.

I used my barndoor with the stock Canon lens and got results that pleased me, considering the low cost of the device.

[matt-c]

If you are looking for a starter 200mm lens I honestly can't recommend old takumars enough.

I litteraly have no complaints with mine although I've heard some have weird CA.

The one is use is f4 and I don't actually need to step it down at all.

Smaller than that I love Carl zeiss 2.8 135mm beautiful lens.

Smaller again nifty 50 is unrivaled in price/performance (I actually use an old Nikor 50mm with adapter)

Smaller again 16/14mm samyang are amazing, hard pressed to find a better priced wide field fast lens.

I also love my samyang 8mm fisheye just for those times you need landscape in.

I should mention I use all these with a crop sensor.

This turned out bigger than planned haha sorry but..... My name is Matt I don't own a telescope and I'm a lensaholic

[happy-kat]

My barn door has it's own base on adjustable feet and can be leveled and is very sturdy.

They are great projects.

[Knight of Clear Skies]

Some good advice above.

While the kit lens isn't the best it is possible to get good results with it. I've heard good things about the 14mm Samyang but it might be worth giving the kit lens a spin first.

The 70-300mm isn't ideal for AP. Similar to the kit lens the extra elements reduce light transmittance and tend to increase distortion, an old prime lens will likely give better results. 300mm also sounds ambitious for a barn-door tracker, I'd expect better results at shorter focal lengths. As others have said the 50mm is great for AP. I put together a quick guide to budget lenses if you're interested.