M51 - but is it any good?

[Parallax]

I can't make my mind up on this one. I suppose that for a webcam image I shouldn't expect too much.

12x30s, colour turned off, prime focus 8" newt, K3CCDTools, Registax, Gimp.

I'm sure that I don't need exposures as long as 30s - I need to do more experimenting.

Steve

[LaVey]

wow.. nice image for a webcam shot!!

[centroid]

That's not at all bad for a web-cam 'shot' Steve.

You say that you don't think you need exposures as long as 30 secs :?, my M51 was taken using 600 sec exposures, and its still 'noisy'. Albeit it was taken through hazy cloud and with a colour camera.

I realise that with the web-cam, amplifier 'glow' would become an issue with long exposures, but subtracting a 'dark frame' would help this situation.

While relatively short exposures will capture the bright core, they aren't sufficient enough for the 'dust' and detail in the 'arms'.

Try pushing the exposure time, and take 'dark frame'.

HTH

Dave

[gary1968]

Thats a great shot, I take it you use a modded web cam....

Gary

[geoff_k]

That is pretty good for a webcam. I tried M51 last year with my long exposure ATIK camera and got nothing as good as that.

I guess more and longer exposures would be need as its not the easiest object.

Geoff

[Sam]

That's a great shot! you must be very pleased.

[Parallax]

OK, so longer exposures it might have to be. The only(?) problem I have is tracking. As yet I don't have the capability for guiding, only RA tracking and the object 'moves about' during exposures - not so much drift, more like errors in the gears/motor (I think).

Nevertheless, I'll give it a go.

Steve

[centroid]

Sounds like Periodic Error (PE) in the mount Steve, and all mounts will have this problem to a particular degree.

Guiding is one way of 'ironing' these out of course, and some mounts like the LX200, have the ability to correct for PE.

However, depending on how good your Polar Alignment is, you should be able to achieve something between 60 and 90 secs, although this is dependent on the FOV, at which you are imaging. The wider the FOV, the more forgiving it is.

If you try 'pushing' the exposure, you'll soon find out how far you can take this, before star trailing starts to appear.

Dave

[RobH]

I'm sure that I don't need exposures as long as 30s

30 seconds is a pretty short exposure for DSO's Steve

If you get your periodic error sorted out, with a good polar alignment you should be able to get at leat 1 minute, which will go a lot deeper than 30 seconds.

Your signal to noise ratio will improve dramatically, even at 30 second exposures, if you get 50 or more of them. You already have 12, try adding a bunch more.

That said, it's a pretty good start...well done!

Cheers

Rob

[Parallax]

However, depending on how good your Polar Alignment is, you should be able to achieve something between 60 and 90 secs, although this is dependent on the FOV, at which you are imaging. The wider the FOV, the more forgiving it is.

Unfortunately that's another problem (opportunity) - FOV. I'm stuck with what I have. The webcam is only 640x480 and the scope is 200mm f5. A focal reducer would help I know but that would involve moving the primary mirror. Not a job I relish.

So, it's perfect polar alignment, perfect focus, good seeing, no clouds, no wind - see you in 2011 then

Steve

[Cloudwatcher]

So, it's perfect polar alignment, perfect focus, good seeing, no clouds, no wind - see you in 2011 then

Steve

Sounds optimistic to me!

Good image though.

Cheers

CW

[MikeD]

Very nice result.

Webcam,4.5" newt and 15 second exposure's is how I started out on DSO's (2004).

I remember taking 70 subs to pick the best 20 or so that had minimal trailing to stack.

Keep them comming.

Mike.