Another M42

[LightningNZ (Cam)]

This is almost 2 hours of exposure - but sadly it's mostly 30 second subs, with 12x 2-minute subs thrown in for good measure - taken over two nights from my Mag 4.somethingawful skies.

The first night had decent seeing and good focus. The 2nd night had better seeing but worse focus. Sadly the stars have suffered for it, but the nebula looks better for the extra photons.

Captured with my AT65EDQ and Canon 300D at a mix of ISO 200 and 400, on HEQ5 mounting - no guiding and only rudimentary polar alignment. Darks, flats and bias frames included.

Frames combined in DSS. All processing in Adobe Photoshop.

[cometcatcher (Kevin)]

That turned out pretty well. I see there's still a few old cameras still in use. May as well make good use of them.

[LightningNZ (Cam)]

Originally Posted by cometcatcher

That turned out pretty well. I see there's still a few old cameras still in use. May as well make good use of them.

It's such a pain to use now. Focusing without live-view, computer control or angled screen is horrific. As a result, the focus is off a bit in this image.

But thank you, I'm also fairly pleased with the result.

[cometcatcher (Kevin)]

Yeah I feel your pain. I recently got a full spectrum D70s. No liveview and the preview screen is tiny with low pixel density.

[raymo]

Very nice! I assume that it was taken at the prime focus of your 65mm
scope. Given that M42 is situated in a very unforgiving part of the sky,
as far as star trailing is concerned, I would love to know how you can get
2 min subs with little or no sign of trailing, with only rudimentary
alignment. With my 1000mm f/l f/5 scope at prime focus, and with
alignment within 1 degree in alt and az [which is obviously fairly
rudimentary]I can only get perfectly round stars up to about 10 secs.
I would like to be able to get somewhat longer subs without
having to obtain accurate PA.
raymo

[nebulosity. (Jo)]

Nice result Cam at least the 300D has good size pixels. With my 350D I plug it into an old trial version of nebulosity and get good focus that way.

Jo

[LightningNZ (Cam)]

Originally Posted by nebulosity.

Nice result Cam at least the 300D has good size pixels. With my 350D I plug it into an old trial version of nebulosity and get good focus that way.

Jo

Ah, if only you could do that with the 300D. Sadly, with no Live View capability that's just not possible. That "50" makes a big difference.

You're right though - it does have big pixels and is pretty darned sensitive.

It does have a fair bit of noise though and that ramps up big-time with temperature. I tried imaging at 30'C one night last summer and I basically just captured white 'heat fog' in my 30 second images.

[LightningNZ (Cam)]

Originally Posted by raymo

Very nice! I assume that it was taken at the prime focus of your 65mm
scope. Given that M42 is situated in a very unforgiving part of the sky,
as far as star trailing is concerned, I would love to know how you can get
2 min subs with little or no sign of trailing, with only rudimentary
alignment. With my 1000mm f/l f/5 scope at prime focus, and with
alignment within 1 degree in alt and az [which is obviously fairly
rudimentary]I can only get perfectly round stars up to about 10 secs.
I would like to be able to get somewhat longer subs without
having to obtain accurate PA.
raymo

Hey Raymo, yes I am imaging at prime focus, 422mm or some-such.

Well, if I'm imaging towards the north (my best skies, cough, mag 4, cough) I can't see south of the zenith because my house blocks the view.

But,

1) I know roughly my house's offset orientation from south. So I can plonk down my scope, set for my latitude, hope it's roughly flat on the bricks of patio and angle it towards south.

2) I take a 3 minute image and see if I'm getting much trailing then I give the polar axis a tweak east or west and try again. This image got one tweak towards the east and looked not too badly trailed after a 2-minute exposure so I went with it.

Done. Admittedly the HEQ-5 is a solid little mounting and tracks very well, but without guiding I'd have to properly drift align it if I wanted to go beyond 90 seconds with really round stars. And I'm *way* too lazy for that.

I'd say I hope that helps, but I doubt it does. With a 1000mm focal length you really will need reasonable polar alignment. What mounting are you using? Make sure it tracks well. I always make sure that the worm is driving properly after a few minutes to take out any backlash from having moved into place. Also make sure your setup is east heavy so that the worm is driving through its full rotation.

Good luck.

[raymo]

I use an HEQ5 too. It was just wishful thinking; I'm going to
have to continue getting pretty accurately aligned.
raymo