Who needs astrotrac! (when you have an SE)

[Ags]

The attached blow-up of Procyon was shot at only 55mm focal length, but as you can see it is perfectly round. The exposure length was 4.5 minutes!

I didn't know my plucky little 4SE mount could do that. I also shot some stars up at around the declination of Casseiopeia and found tracking a bit harder there. But I still got roundish stars at 180 seconds - close enough to round to fix in GIMP.

It's not perfect - the mount is not consistent across exposures and some subs would have to be thrown away and this of course gets worse the longer the subs are but still - 4.5 minutes! Wow!

The major problem I have is polar aligning the SE. At the moment I just point the north leg at Polaris... The elevation scale on the mount is also a bit vague - it is only graduated to 5 degree accuracy and there is no clear point to read the scale against.

Any suggestions for what I can do with 4.5 minutes (!!!) given that I have a lot of LP and don't drive?

[Psychobilly]

While each sub may be acceptable you will get rotation between each frame as long as you keep your target centered in the frame and shoot a wider than "normal" you can crop off the edges...

[ollypenrice]

Good to see - but it is only 55mm....

Olly

[jgs001]

I guess you're using your built in wedge ?? If you can get a good enough polar alignment on it... then have a go at a wide field of Orion... If your PA isn't up to much, you may lose the corners due to field rotation anyway... but if you go a bit wider, you should have some room to spare... See if you can get M42/M43, Horsehead and Flame, Barnards Loop and the bit Neb around Meissa (can't remember what it's called )... I got all those with an unmodded camera using 5 minute subs at 50mm. You need about 3 hours worth of subs to bring them out.

[Ags]

It is only 55mm, but I presume I can count on half that at 100mm and so on...?

I should not get field rotation as I am more or less polar aligned and the subs would be of limited length, and DSS can rotate the subs during alignment.

[jgs001]

You might find you can manage more than half that at 100mm.. .it's in the realms of try it and see I'm afraid. As for field rotation, that's dependant on how good your polar alignment is, and how lone the exposures are... if you're not seeing it, then that's good.

[Psychobilly]

Does the controller software support all star wedge alignment... It does on the higher end mounts and I wondered if they have rippled it down to the SE?

Peter...

[Ags]

I think you mean the alignment method where the mount finishes by pointing the scope to where Polaris should be and then you wiggle the mount to center Polaris in the FOV? Yes my mount does do that, but it sounds a bit of a nightmare.

I only had a 55mm to try last night, but today my new 55-250 zoom arrived!

[Psychobilly]

Yep thats the one...

The latest version works with any star not just polaris so its handy if you cant see polaris...

Peter...

[Ags]

The latest version works with any star not just polaris so its handy if you cant see polaris...

Peter...

Pity - mine doesn't do that. The problem is I have only the camera mounted, no scope, so unless I center-spot the live view screen...