Comet C/2012 F6 (Lemmon)

[rat156]

Hi All,

From the usually cloudy Melbourne, a rare night of clarity.

I have finally got my new gear mostly sorted, just in time to try to capture comet Lemmon. Taken with an ASA N12, Sbig STT8300 combination. Over the past few nights I've been taking photos of this comet, but I keep getting trailing in RA, this is still present. I've worked out (after a few consultations with the internet) that guiding near the pole is not a simple task. Also I have shifted over to a Mac for telescope and camera control using The Sky X and the camera add-on, this has introduced a few complications (like timeouts for the CFW which stop the imaging sequence) and having to setup the colour series differently to drop the stars from the image.

Anyway, here's the picture, 30 mins Luminance (10 x 3 min), 10 each for RGB (10 x 1 min, binned 2x2). Processed in CCDStack2 and Photoshop.

Cheers
Stuart

P.S. Added an image with stars, you can see the guiding errors in this image.

[Astroman (Andrew Wall)]

Well Done Stuart, looks like it's in a difficult position for a little while. Glad to see you got some clear skies and were able to capture the comet. Hoping to do the same soon...

[tilbrook@rbe.ne (Justin Tilbrook)]

Good job Stuart!

Looks like you atruff time of it, tracking wise.

Cheers,

Justin.

[gregbradley]

Lovely lovely result. I really like that.

Gear issues are a regular thing, even with a "mature" setup. I can't believe how many times just using the same gear throws up something not working quite right.

Basically it seems to me computers don't like external devices that much and that interactions between computers and external devices is still quite crude despite all the versions of Windows/Macs over the years. Its fussy and drops out easily. I also find modern computers are easily stumped by interrupting a command. They really don't like that. They also often require an exact startup sequence.

Greg.

[Rigel003 (Graeme)]

Very nice image, Stuart. I can relate to the guiding issue near the pole. 2 nights ago, I found it impossible to use PHD. It wouldn't calibrate in the EW plane because the pulses it send to the mount wouldn't move the the scope sufficiently East and West. How did you align on the comet in CCDStack?

[orestis]

Nice shot Stuart,

How did you remove the stars?

Cheers
Orestis

[rat156]

Originally Posted by Rigel003

Very nice image, Stuart. I can relate to the guiding issue near the pole. 2 nights ago, I found it impossible to use PHD. It wouldn't calibrate in the EW plane because the pulses it send to the mount wouldn't move the the scope sufficiently East and West. How did you align on the comet in CCDStack?

Hi Rigel,

The trick to calibrating is to move a little away and calibrate there, then move back. TSX then adjusts the correction rate depending on the declination you're shooting at, even then it struggles. AO is the way to go here, but I haven't got the available back focus anymore.

Using CCDStack2 (which I had to upgrade last night) is to use Star Snap and simply chose one "star", the comet. The software then just shifts the image to align the comet. You have to manually move the comet so it nearly overlays, so it doesn't just pick a random star.

Cheers
Stuart

[rat156]

Originally Posted by orestis

Nice shot Stuart,

How did you remove the stars?

Cheers
Orestis

Hi Orestis,

The process starts with the data acquisition. I take the subs in the order LRGBLRGB etc. I also add a delay between each sub exposure. This means that for subsequent exposures for each filter the stars don't overlap, so when you combine them in CCDStack you can eliminate the stars using data rejection techniques.

Cheers
Stuart