Time for tracking ?

[Darawan]

I wanna know that how much time this tracker tracking sky , I wanna track milky way for about 4 minutes or more , can i Use this mount ?
ioptron skytracker :
https://www.ioptron.com/index.cfm?select=productdetails&phid=cffad01a-797c-4cf4-beb8-a64bc8e09b06

aad what about astrotrack mount ? Can I track object for 5 minutes or less ??

thank you ^_^ >

 

[Designer]

That sure looks like it would work.

If you are asking about "astroscan", that seems to be a brand name of a newtonian type of telescope, and I don't think they can include an equatorial amount and a motor.

So not the same thing, IMO.

 

[TCampbell]

I wanna know that how much time this tracker tracking sky , I wanna track milky way for about 4 minutes or more , can i Use this mount ?
ioptron skytracker :
https://www.ioptron.com/index.cfm?select=productdetails&phid=cffad01a-797c-4cf4-beb8-a64bc8e09b06

aad what about astrotrack mount ? Can I track object for 5 minutes or less ??

thank you ^_^ >

There are quite a few devices that can do this... I'll mention four different devices (and there are more).

Probably the best device I've come across so far (limiting to tracking mounts made specifically for cameras) is the Losmandy Starlapse. The device basically is the right-ascension drive from a Losmandy G8 mount except it's adapted to mount onto an ordinary camera tripod and allows you to put a camera on it. This is the most expensive tracking mount that I've seen (excluding mounts made for telescopes) as it's in the "more than $500" category.

Next in line is the AstroTrac -- it's also very high end, but you'll notice that it has a set of scissor-like arms ... one of which locks in place and the other has a screw-drive on it to keep that arm pushing away at a steady rate to track the motion of the sky. You can clearly see that this will run out of travel after a while and have to be moved... HOWEVER... that slim angle that you see is actually enough travel to take a 2 hour exposure (far more than you could ever possibly need.) The AstroTrac is also in the "more than $500" price category.

And then there are a few of these units in the "less than $500" price range. These include the iOptron SkyTracker and the Vixen Polarie Star Tracker. Both the iOptron and the Vixen look very much alike and work similarly.

Next question: How long can you track?

The answer really depends on how well you polar-aligned the device. The Earth is rotating on it's axis from west to east giving us the illusion that the sky is moving from east to west. Astrophotographers who are doing long exposures will tell it is NOT EASY to take long exposures. The mount needs an especially accurate polar alignment and that's not as easy as just pointing to roughly near the north star (Polaris) and going from there. The north star is technically 40 arc-minutes away from the celestial north pole (about 2/3rds of a degree). While that may not seem like much... the moon is only 1/2 degree in angular measurements from edge to edge. That means there is enough room to put a moon's width between Polaris and the celestial north pole and still have a bit of room to spare.

At wide angles you have a lot of "wiggle room" for accuracy. At very long focal lengths (e.g. suppose you decide to use a 600mm lens) any amount of error will be more noticeable and you can start to get elongated stars rather than pin-points if the mount wasn't precisely aligned to the celestial north pole.

ALL of these are made by companies well-known in astronomy circles. Losmandy and iOptron are telescope mount manufacturers and have solid reputations.

If you wanted to put a lot of weight on it (think big long telephoto lenses) then I'd probably go with the Losmandy mount. If you plan to use shorter/wider lenses (e.g. less overall camera weight) then I suspect any of them will give you very satisfactory performance -- but remember they MUST be aligned to the celestial pole accurately if you want long tracking times.)

 

[Darawan]

How I can Get Best polar alignment ?

 

[WayneF]

I wanna know that how much time this tracker tracking sky , I wanna track milky way for about 4 minutes or more , can i Use this mount ?
ioptron skytracker :
https://www.ioptron.com/index.cfm?select=productdetails&phid=cffad01a-797c-4cf4-beb8-a64bc8e09b06

aad what about astrotrack mount ? Can I track object for 5 minutes or less ??

thank you ^_^ >

$448 takes my breath away. You can build something for almost free.

Read some here first: build star tracker - Google Search

Here is a good link maybe not above : http://people.rit.edu/andpph/text-star-tracker.html

And there is much more, look around for it.

Tracking 5 or 10 minutes is easy with these (with a straight screw), but more advanced units use a curved rod which might track well for 30 minutes.

You turn this screw one turn per minute, or 1/4 turn every 15 seconds. Some add a one RPM motor, but for just a few times to use it, turning the screw manually seems no big deal.

 

[TCampbell]

How I can Get Best polar alignment ?

If you are using the iOptron device, then see page 9 of the instruction manual posted here: https://ioptron.com/images/up/SkyTracker_Manual.pdf

First... all of this assumes that the tripod is actually perfectly level. I hate the bubble levels built into many tripods. When I use a quality level and compare to the bubble level, I find the tiny little bubble levels can really be off by quite a bit. I carry a small 2-axis spirit level with me and ignore the ones built into the tripods (line up three identical tripods in a row and you probably won't get the same reading out of any two of the built-in bubble levels.)

Assuming the tripod is level... now it's time to do the precise pointing.

Notice they have an iPhone app (you could look this up yourself) to determine the position of Polaris relative to the north celestial pole. Through this particular reticle finder (because there are lots of variations on this) they have (a) a center point, (b) an inner ring, (c) an outer ring, and (d) they label the ring like the hours on a clock (12 hours) all going around the center. The inner ring is for use in the northern hemisphere to locate the north celestial pole (ignore the outer ring if you are in the northern hemisphere).

Polaris circles the north celestial pole (NCP) traveling around the path of that ring. You know the device needs to pointed somewhere around that ring... but don't know exactly where. The phone app provides that info for you.

They mark the ring with the hours (1-12) just like a clock (in reality astronomers use a 24 hour "sidereal" day, but they are simplifying this for you.)

On the screen of the phone (on page 9) they show that Polaris should be located at the 10:24 position and they also show a tiny green "+" mark at that point. The idea is that you would look through the polar finder scope (that small black tube on the corner of the SkyTracker) and position it so that Polaris is at that point. (Don't forget... tripod must first be level or all of this is meaningless.)

You know have a pretty good alignment. With big telescopes we fuss quite a bit more than that and perform a precise polar alignment using either drift alignment or other alignment software.

For short duration exposures with wide angle lenses you won't see much (if any) star trails caused by mis-alignment. The wider the angle of view of the lens and the shorter the exposure time, the less important it is to have a critically accurate polar alignment. This mostly becomes important when you either want long exposures or you want to use a fairly long telephoto lens to image deep sky objects in detail.

The alignment aids vary by scope but most of these things either include (or have an optional accessory) that helps you create a pretty good polar alignment.

 

[TCampbell]

I wanna know that how much time this tracker tracking sky , I wanna track milky way for about 4 minutes or more , can i Use this mount ?
ioptron skytracker :
https://www.ioptron.com/index.cfm?select=productdetails&phid=cffad01a-797c-4cf4-beb8-a64bc8e09b06

aad what about astrotrack mount ? Can I track object for 5 minutes or less ??

thank you ^_^ >

$448 takes my breath away. You can build something for almost free.

Read some here first: build star tracker - Google Search

Here is a good link maybe not above : How to make a "leaf" or "book" style star tracker mount

And there is much more, look around for it.

Tracking 5 or 10 minutes is easy with these (with a straight screw), but more advanced units use a curved rod which might track well for 30 minutes.

You turn this screw one turn per minute, or 1/4 turn every 15 seconds. Some add a one RPM motor, but for just a few times to use it, turning the screw manually seems no big deal.

Yep! These work too. If you look you can find write-ups on how to identify the native speed of a motor and/or modify a motor to get the speed you want. The hand-turned screw works well and I always emphasize that the narrower the angle of view (e.g. when using long lenses) and the longer the shot duration, then the more important it is to have precise tracking. But frankly with a very angle lens you can take an image for more than 30 seconds without any tracking at all and have absolutely no hint of star elongation (look up the "Rule of 600" which suggests that if you have a full-frame camera you can divide the focal length of the lens into 600... and that value is the number of seconds you can expose without any star trails showing up. If you have an APS-C camera just multiply the focal length of the lens by 1.5 or 1.6 (Nikon or Canon respectively) and use that value.)