How long would an object such as a planet stay in view on a telescope such as Zhumell Z10 Deluxe Dobson?

I am debating whether to buy an electronic Celestron NexStar 8 SE telescope because of the constant tracking. However, I do like the Zhumell Z10 Deluxe Dobsonian Ultimate because it will have a 10" mirror and is cheaper. I do not have a problem with spending some time searching the exact location of galaxies,planets ext as I do have Google sky map on my cell phone to at least point me in the right direction. I was just wondering how long such objects would stay in view after finding planets, galaxies, ext. Then I will decide whether constant tracking is for me.|||Get the 10". Yes, you will need to nudge the scope to counter act the earth's rotation, but the views are worth it. One thing that will help you located objects is to get a telrad.


http://www.backyard-astro.com/equipment/鈥?/a>





how long an image will stay in view is a function of your eyepieces field of view. The earth rotates at 15 degrees an hour. If your eyepiece has a field of view of 1 degree, the object will take about 4 minutes to cross from on side to the eyepiece to the other.





15/60 = 0.25 degrees per minute. 0.25 * 4 = 1 degree.


http://www.telescope.com/catalog/product鈥?/a>


http://www.astro.shoregalaxy.com/index_0鈥?/a>|||Tracking with a Dob becomes second nature to most people within about 5 minutes of using a Dob. The actual length of time an object stays in view depends on the magnification and field of view. It's about a minute at low power, perhaps 15 seconds at high power. Because there are no locks or slow motions, it becomes an almost continuous smooth action. I was highly dubious about Dobs after years of using motorized scopes, but found I adapted to it quickly, and actually converted one of my equatorially mounted telescopes to a Dob.|||On my XT10 the views are roughly:








25mm- Objects stay in view for about 30 seconds.








Alternatively if you use a higher magnification eyepiece, objects leave view Much faster.








9mm- 7-10 seconds.








These are just rough approximations. I will go out tonight and let you know more exact times then. (But I'm sure that there has to be a website that has the info).|||Hi. You do understand that the motion is related to Earth's motion and not the object. The amount of time an object stays in the field of view is determined by the magnification of the scope. It the field of view were, say, 30 minutes of arc then the object would take about a minute to traverse the field.|||The eye-piece in use determines the field of view, which


determines the time you ask for without a 'clock drive'.|||The time you can observe without nudging the Dob will depend on the eyepiece. A wide-field, low power ep will allow a few minutes of not nudging. As you increase the magnification.. your field of view quickly shrinks..! The NextStar 8 will make observing a joy. No need to keep nudging.. and you can easily locate many objects - quickly.





The main thing is - do yo have a quite dark sky where you will observe..? And do you ONLY want to look at/for the 'faint fuzzies'..? Or - if you have a sort of dark site..? And if you want to see really sharp %26amp; clear detail on the moon.. and quite a bit on the planets - the 8" NextStar will be your pick.





Either way, have fun..!!|||The amount of time a star, planet or other object will stay in view will depend on three factors:


1. The apparent field of view of your eyepiece


2. The focal lengths of your eyepiece and your telescope objective mirror. (this is two factors which determine your scope magnification. Divide the objective focal length by the eyepiece focal length to find magnification.





Now, divide the apparent field of view of the eyepiece by the magnification to find the true field of view.





Worst case, an object near the celestial equator, you can divide the true field of view by 15 degrees per hour by the true field of view (or 0.25 degrees per minute) to find the time. If you were looking at Polaris, you would find it nearly stays stationary, so multiply by the cosine of the declination of the object to find its own angular rate.





I built a 10" Dobsonian scope with an F4 (or 1000 mm focal length) mirror. My typical eyepiece has about a 60 degree apparent field of view. Say I use one with a 10 mm focal length -- 100 magnification (power). Then my true field of view is 0.6 degrees, a bit larger than the full moon.


If watching the moon when it is at the celestial equator, it will stay visible for at most two minutes -- and actually only part of the moon would be visible that long.





More magnification, faster apparent motion.





Now, fix this with an equatorial platform like I built, which rotates my telescope to compensate for the rotation of the Earth --- see below, follow the links to the pages about my equatorial platform.|||I have an Orion xt10 which is very similar and when I look at saturn at 400x it goes by in probably 4 seconds, but you can see awesome detail if you have very clear skies. At 200x it lasts at least 8 seconds and at 40x and 80x it barely moves. It's takes a few tries and sometimes a few minutes to find it at 400x though but it gets much easier after you get a method. Saturn is the only planet I have seen since I got my scope but I am definitely happy with the 10 inch reflector I have.