Hey all, just looking for some advice!

[bedted (Tim)]

Hey there everyone, this seems to be a fantastic forum and I've already found some valuable information. I've been dabbling in astrophotography after my purchase of a 300mm lens and teleconverter a few months back.

I built a simple barn door mount and have managed to successfully track and stack 1 minute exposures at 35mm (full frame 5D). Turning by hand.

But not surprisingly the barn door mount doesn't work as well with the 300mm lens and TC (effective 420mm).

So now I'm considering where to head next.

I can either invest some time in motorising my current barn door mount, or purchase a ready made solution like the AstroTrac TT320X-AG.

The question is, at over 300mm focal length, exactly how difficult will it be to get acceptable tracking (>1 min subs) motorising the barn door mount?

[h0ughy (David)]

it all comes down to an accurate drift alignment and RA tracking.

[bedted (Tim)]

Also, if I was to head in the Astrotrac direction, and wanted to add auto-guiding -

Would the Orion mini 50mm guide scope plus StarShoot AutoGuider be acceptable?

Would this still function acceptably if I was to later change from my 300mm lens to a Black Diamond ED80 refractor?

My main desire is to shoot wide field DSO with pin point stars.

FWIW I understand the importance of a solid mount, and am prepared to spend time learning drift alignment.

[bedted (Tim)]

Originally Posted by h0ughy

it all comes down to an accurate drift alignment and RA tracking.

Thanks h0ughy, you must have posted just before my second post.

BTW, anyone know the best place to purchase the Astrotrac? Ebay?

[MrB (Simon)]

The barn door will work fine but if aligned well.
I made a barndoor about 15 years ago that worked quite well.
I also made a heavy duty wooden tripod which also had Altitude and Azimuth adjustment screws. With these it was pretty easy to align. I would use the hinge of the barndoor to sight along toward Octans.

My barndoor was purely hand cranked. I made the hand 'wheel' quite large, about 80mm diameter and on that I had a clock face with a bit of thin stiff wire as a marker.
I would watch an analogue clock and follow the second hand around on the clock face on my barndoor's handwheel. Was pretty easy to keep within a few seconds.
It worked very well but did get a bit tedious. Plans were to use a stepper motor but I ended up getting an EQ6.

I did post a photo of it around here once but now can't find it.

[bedted (Tim)]

haha Mr.B that's exactly what I've done so far. I've built a hefty wooden tripod and wooden alt-azimuth mount.

I'm finding though that at a long focal length, I'm introducing far too much movement when rotating by hand.

[MrB (Simon)]

The Astrotrac can be guided in RA only, so 420mm will need very good alignment. Drift aligning is tricky on the Astrotrac, but can be done.
The orion miniguider will be fine for widefield work, but there are better camera's than the StarShoot, even the QHY5 which is almost identical but could likely be sourced cheaper.

I'm finding though that at a long focal length, I'm introducing far too much movement when rotating by hand.

I had the same issue hence the same incentive to use a stepper, but as mentioned never happened.

[bedted (Tim)]

Very much appreciated Simon - that all makes sense. So much to think about and research. While trying to not spend too much money!

[MrB (Simon)]

Worth noting also that the Astrotrac(or any other tracker) will be no better than a barndoor if it's not rigidly mounted