Shopper : Is this item newer model of sky tracker (3302)? or former model(3301)?
Shopper : What focal length lenses are compatable?JOHN L : I have had very good results up to 200 mm, and I am relatively inexperienced and not particularly patient. At 200 mm, I expect to reject about half my images using 30-60 sec exposures. I often use a 18-135 zoom with no issues up to two minutes at 135 if I am meticulous with alignment. At 18 mm, I can go up to 3-5 min. without star trails.KEITH S : The max FL really depends on three items. How well you get this polar aligned, how balanced the lens is with the camera, and exposure time.
On the first, this is a bit harder to get aligned as getting a good drift alignment is much different from a full real mount. I use the alignment routine for about an hour and watch to make sure Polaris stays in the outer ring. This check over every 10' or so gets you pretty dang close.
Lens balance is important, as if you have a big lens you will need to attach the camera not at the camera base but at the lens ring, otherwise balance will cause tilt.
Exposure time, obvious if shorter you can go longer, but get less info. I have a modified camera with the IR/CCD Cover removed, and shoot at F/400 for about 4' per exposure. That keeps the image data clean enough and makes for some really strong data for stacking.
On the lens if balanced right, and aligned right, I would not go more than 200mm due to flex of the components. I typically use moderately fast (F/3.5 or better) 8, 50, or 180mm lenses.GERALD C : Depends upon weight and balance of your rig (body and lens)
Total not over 5-6 lbsPETER S : Any, or whatever fits on your camera. But you have to be aware of the overall weight limitation (see specs), which would preclude the use of a very long lensYURIY T : Conservatively, at 50mm focal length you will be able to make 3 minutes shots with ~50% chance of round stars without trails.
Longer focal length (>50mm) - shorter exposures and less chances for the perfects starts. At shorter focus you will be able to take longer exposures with better chances for success.KEITH W : I use a couple of different lens - one is 50mm and the other is adjustable from about 35 to 135mm. Any lens on a camera will work. The larger the focal length the less tolerant the unit will be to improper polar alignment.LEWIS H : Generally speaking, the shorter the FL, the less chance of unwanted star trails and "tadpolized" objects. Also, the wider the angle of your objective lens is, the shorter the time needed for a proper exposure. When you increase the focal length, e.g. from 50 to 120 mm, on a zoom lens, you increase the magnification, but require a longer exposure, which makes exact tracking to obtain pin-point stars much more difficult.
To get best results:
1. Set the tracker onto a STURDY tripod, preferably one that has built-in level indicator.
2. Find Polaris (the North Star) through the polar scope. Take your time to get an EXACT polar alignment through the polar scope.
3. Mount the camera onto the tracker--tighten all screws. They tend to loosen easily when adjusting the aim of the camera.
4. Start with a wide-angle lens on the camera, or the lowest FL on a zoom objective.
5. Set your camera at a fairly high ISO rating, e.g. 3200 or 6400 so that you can make your exposure at a faster speed, e.g. 5-10 sec.
6. Make sure the camera is switched over to MANUAL focus and set at Infinity. Use the self-timer or a remote shutter control to initiate the exposure so you do not have to touch the camera while the shutter is open.
7. After the first few exposures, examine the results by zooming in on the object(s). If there any telltale "tadpoles", then something is not right and increasing the FL and/or exposure time will only give worse results.
If stars appear as clear, non-blurry pinpoints, even when zooming in on sample pics, then it's safe to move up to a higher FL, requiring a slightly longer exposure and/or higher ISO. (You may wish to go for higher quality by decreasing the ISO but must compensate by increasing the exposure.
Best results with a longer FL / higher magnification are achieved with bright objects, like the Moon:, set at 1/125 sec @100 ISO.
To answer your Q more directly:
I've gotten acceptable results with a zoom set at 100-150 mm, 12 sec @ high ISO.JIM N : It is a matter of weight and balance. I have used a range from 35mm up to 150mm. My experience has been that with the telephotos especially, stacking a larger number of shorter exposures works much better.
ed d : Will it work with a small telescope?DIDIER S : The mount is rated for 11lbs load, so that should accommodate a small telescope. However, it seems to have some trouble tracking with my 5lb camera+telephoto lens set up (I'm still working out the kinks) at 300mm. Perhaps the use of a counterweight (see the iOptron website for accessories) would take care of this.YURIY T : If we have astrophoto in mind then the longest focal length that could be practically used with SkyTracker is 50...80mm.
That means a camera + a "normal" lens combo.
Even the smallest telescope will be above capacity of the SkyTracker due to its limited tracking accuracy.GERALD C : Yes, it should, weight limit 6lbs
must be used with ball headLEWIS H : There is no reason why the SkyTracker should not work with a small telescope just as well as with a camera + telephoto objective lens.
Be aware however that this instrument works best non-telescopic optics. Best results are achieved with wide-angle objectives. Since a telescope involves the opposite set of optics, use the lowest possible magnification (for example an eye-piece @20-32 mm. Another thing to be aware of is the length of the exposure time. The longer the shutter is open, the greater chance for stars to develop tadpole tails.
The more you magnify therefore, the shorter the exposure ought to be. Since more magnification requires more light, however, you will need to increase the ISO setting to a faster one, e.g. ISO 1600.
For just visual observing and not astrophotography, attaching a telescope should work just as well as a camera. Because of the dimensions of the StarTracker, however, there is a weight consideration. The telecope should not weigh more than a good sized digital camera with a medium-sized objective lens, ie. not more than 3kg /5-6 lbs. I would also recommended avoiding flimsy tripods. I would also recommended attaching a ball head connector between the telescope and SkyTracker. It will then be easier to maneuver your telescope around to different objects, without moving the tripod, which would then require re-alignment.
The more accurate your polar alignment is (ie centering Polaris in the crosshairs of the polar scope, the longer and more precise the StarTracker will work for you. This is less important if you are just observing with a telescope, but extremely important if you doing photography with exposures of over 15 seconds, using telephoto lenses or greater magnification on a telescope.
The instrument itself is sturdy and reliable, and has harvested excellent test reports.
LewisANTHONY J : It's possible, but keep in mind that it's made to use with a standard camera tripod mount. If you can mount your telescope to a camera tripod, and the telescope doesn't weigh more than a few pounds, you might be able to do that.
The device itself may get in the way or create odd viewing angles if visual observing is your goal - a small goto telescope mount might be better for that purpose.
I must say I absolutely love this product. It's easy to use and does it's job extremely well. KEITH S : No even with the weight under 4lb the lever arm would cause too much stress on the gears. May last a short period but very suspect on longevity.
