Nano tracker vs goto az/alt mount

[mislav]

what do you think-which is better for astroimaging? Where i can do longer quality exposures? (ofcourse with same gear-lets say 300mm lens)... I cant find calculator for max exposure- i am planing to image orion nebula (i am in Zagreb-46latitude), planing to image it with 150p telescope on az/alt goto mount...Also i have nanotracker and 300mm lens... what do you think where will i manage to have longer exposure, and where will i have better results???

[rickwayne]

Without any kind of tracker (e.g. with an alt/az mount), the rule of thumb is no longer than 500 / focal-length for full-frame cameras, and maybe 300 / focal-length for APS-C to avoid objectionable star trails. Before everyone jumps on me, these are GUIDELINES, and your tolerance for trailed stars in your images may be more or less than this. And of course it depends on declination, too, Polaris will be pretty tight at most exposures :-).

For example, if you're shooting APS-C with a 300mm lens without a tracker, you can't expose more than 1 second without trailing. Which means you're going to have to run a pretty high ISO, and then shoot gonzillions of sub-exposures and stack them to get rid of all the ugly noise. You'll also have to adjust where you're pointing periodically. That need not be every frame, stacking programs like Deep Sky Stacker and even Photoshop can align images that are displaced and rotated. But if nothing else, your target is going to eventually move right out of frame.

I'd never even heard of the Nano before your post -- thanks! It claims a weight limit of "< 5kg", which is hard to believe; my $1000 equatorial mount claims 12kg, and most astrophotographers use only half of their mount's rated weight. Still, it might work!

The challenge with Orion is getting enough photons to bring out the nebulosity without totally blowing out the Trapezium area, which is quite bright. (To say nothing of the stars themselves!) I have gotten reasonable results with as few as 10 149" ISO 400 exposures through a f/4.6 telescope (https://rickwayne.zenfolio.com/astrophotos/ea84bfd37); in really dark skies, I got not-too-bad with just half a dozen two-minute ISO 800 ones (https://rickwayne.zenfolio.com/astrophotos/eba9bb032). With the Nano, I'd go with a higher ISO and much shorter exposure, maybe even 30 seconds to start with, and take a LOAD of frames, stack them, see what you get.

And welcome!

[mislav]

5kg is overrated ofcourse...but 135mm and nex5 are going fine...i tought goto alt-az..I am not afraid of star trails, i am afraid of rotation.. Nanotracker is nice piece of equipment if you want to easy carry stuff.. I dont like polar aligning hole...But its ok for 50mm lens (i am all talking about apsc)..

[happy-kat]

Altaz tracking should give a range of 15-45 seconds using the 300mm lens, if you use the 50mm lens you'll have more space around the object to crop field rotation. 150p you have is much more prone to wind shake so exposure length might be much less. You already own the mount so why not just try it and see.