Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: Can this be used with a 2x "1000mm" adapter (doubler)?
Document: The lens is, essentially, a short range telescope; however, if you are expecting to use it for extremely distant subjects, I would opt to purchase a telescope and t-mount adapter instead.On the downside, the lens is heavy and difficult to hold steady without the use of a tripod. It is also very difficult to aim, especially with the 2x extension attached; slight movements can cause you to completely lose your objective. Even a target as large as the moon can slip out of sight easily.
It is a good lens for the money.....just make sure you order an extra T Mount Adapter.
The only problem I have actually had with the lens (other than its weight) is the tripod mount. It either uses different threading than what I have or was defective when I got it, as the quick release adapter on my tripod will not thread into the lens mount but will thread into my camera.The short of it is: the lens is due a little more credit than it receives but, for the tight-budget hobbyist, it is worth every cent.
After receiving this lens, I tried it out and it works well and takes pretty decent pics as well. My only concern is the T Mount Adapter. The one that was sent with the lens, either had a defect or it isn't really a good adapter, as upon the first tim using it, the adapter went on, but not snug on the lens, and is loose, allowing te body of the lens to rotate.
This lens in not bad at all. I was unsure about this when I saw the price. I figure it is worth a try instead of paying hundreds of dollar. When the lens arrive, I put it to the test. It was during a snow storm with little light and I used this lens to take some picture of deer that hang out on our property. I got some real nice shots.
This lens is capable of producing sharp detailed images, you just have to know how to work it correctly. If you are debating whether or not you should by this lens, debate no more, try it out, you will get some blurry images but that is because you are shooting at extreme focal lengths and manual focus is your worst enemy on this lens. Especially if you are used to taking photos in AF. I would recommend this lens to anyone, professional or consumer buyer.
Have used it with my t3 and my t3i and it does an incredible job. I use it when I go take my wildlife photos, and with the use on a monopod, I have gotten some beautiful photos which were far more detailed than people using lens that cost many thousands of dollars. Don't be afraid of the fact it is preset and manual - if you are shooting in the sunlight it is simple to use. I have not tried night photography with this lens, but for daytime shooting it is great.
I will be enjoining this lens I bought the doubler lens for ( Opteka High Definition 2X Telephoto Converter for Opteka 650-1300mm, 500mm and 800mm SLR Lenses) this and the combination works well together.
this is a pea shooter i can take it without care and shoot and id birds. Way better then the 75-300mm. Nothing award winning, but i shoot free hand and with a steady wind condition I don't even use a tripod and get clear pictures. you manually focus and set your own fstop, and it is what it is! I highly recommend it!
Whenever possible, work at a smaller aperture to give yourself more room for error...you're going to need all you can get.This brings us to the aperture, which is also manual. One ring marked with f/stop numbers acts as a stop block to select the minimum aperture, while a second ring marked O &lt;-> C actually closes the leaves. Pick the desired aperture on the first ring; but leave the second ring wide open to focus.
Answer: yes and you can order in combo pack on Amazon - I did. It takes incredible pictures- with or without tripod or monopod. It's one disadvantage is that it does not have image stabilization. I use it to photograph the annual bird nesting on High Island here on the Texas Gulf.