Max exposure unguided?

[Astronutjob]

Hello how long of an exposure do you think i could get unguided with out trailing using an heq5 pro and megrez which is 430mm FL, with a semi decent polar alignment?

[Sam]

I reckon you'd get 120-180 seconds if you alignment was spot on. You'd need to drift align to get it as good as possible which will help with the length of time you'd get before mount errors start leave star trails. You might get even longer depending how well built the mount is. There's someone on here with a high end mount who gets 10min exposures unguided so a lot of it is to do with the final finish of your mount. With my HEQ5 it was good for about 180 seconds until the very minor bumps and differences in the worm gear and teeth started to mess things up. Having a well balanced and exactly aligned system will go along way to giving the best chance of exposures over 120 seconds.

Sam

[dph1nm]

Depends what resolution you want to image at (i.e. what size are your pixels in arcsec). My HEQ5 averages about 4"/minute periodic error (depends where you are in the cycle of course).

NigelM

[jgs001]

I have managed, with my HEQ5, C80ED and 450d, 4 minutes, but only the once. I can manage 2 to 3 minutes consistently.

[Bizibilder]

I usually stop at 120secs on my HEQ5 + 200P - quite a heavy setup! If I go any longer the reject rate is worse in terms of "time" wasted.

[namreg]

The best I've managed with my EQ5 is 120 secs at 165mm. My polar alignment is as good as I can get it using the polar scope. Couldn't get on with drift alignment - OK in the south/meridian intersection but all over the shop in the east. Gave up in the end. As the PE is so bad I decided spending forever on drift alignment is probably a waste of time anyway. Oh for a decent mount!

[ollypenrice]

But even a decent mount needs guiding. The Takahashi EM200 with +/- 5 arcsecs needs autoguiding at anything remotely telescopic in focal length. It is just a fact of imaging life and with all the autoguiders out there that are not too expensive any more we are rather pampered as consumers, really. A guide scope can be any old junk, cobbled up to eliminate flexure. An ST80 £85 from FLO has to be a bargain.

Olly