first starfield

[muletopia (Chris)]

This is my first attempt at a star field, so I am looking for comments and advice on how to do better.

The field is somewhere near M47

Canon 60Da 26 exposures of 24 seconds at ISO 800
at prime focus of my Mewlon 210 on a HEQ5 pro mount guided with a ZWO asi 120mm on an Orion thin off axis guider.
5 darks were taken. The processing used the Canon raw recordings.
All processing in Nebulosity 3
The darks were stacked and the resulting "masterdark" subtracted from all the light exposures.
These records were graded by Nebulosity and the best 5 selected for use.
The 5 frames were normalised and debayered ,
stacked with translation and rotation selected
then stretched with the digital development tool.

Chris

[doppler (Rick)]

Your image looks sharp, well focused and guided, so a great start. Your Mewlon 210 is pretty slow at f11.5 ?, so a lot more exposure is needed, maybe iso 1600 and 120 sec subs. With good guiding it can be done, keep at it.

[PKay (Peter)]

It looks good Chris.

Sort of draws you in.

One day the colours will appear. Play around with stretching (developing, histogram transformation, DDP for Nebulosity I think).

Be mindful of overexposure (you lose colour).

Play around with the camera settings and learn.

I don't use Nebulosity, but this looks good: http://northlincsastro.org/images/A%...Nebulosity.pdf

Well done.

[muletopia (Chris)]

Thanks doppler and PKay, I played around and tried longer exposures at low ISO.
To hunt colours I went to the Jewel Box.
150 seconds at ISO 100 was the most promising I found.

Star shapes are becoming a problem even with off axis guiding.

Suggestions please.

Chris

Mewlon 210 Canon 60Da Orion thin off axis guider, HEQ5-Pro

[Imme (Jon)]

It appears to be more of a sensor tilt issue than a tracking issue when it comes to the star shape. Looks to me they are elongated on the right hand side of the pic but not the left......if it was tracking I’d expected star shapes across the field to be the same

Originally Posted by muletopia

Thanks doppler and PKay, I played around and tried longer exposures at low ISO.
To hunt colours I went to the Jewel Box.
150 seconds at ISO 100 was the most promising I found.

Star shapes are becoming a problem even with off axis guiding.

Suggestions please.

Chris

Mewlon 210 Canon 60Da Orion thin off axis guider, HEQ5-Pro

[doppler (Rick)]

Hi Chris, that's looking pretty good for 150 sec subs, but I think 100 iso is a bit low for your camera, 400 iso is probably as low as you need to go with a canon DSLR.

I'm not sure if you can get guiding perfect and consistent unless you have a permanent mount in an obs. The longer the focal length the more little things will start to affect guiding, you have to keep checking for any movement in your imaging train and tweaking the balance.

Balance is the biggest variable for me, some nights I get it all just right and the guiding is perfect and others it is all over the place. You have a pretty long focal length to tame but perseverance is the key, I have marks on my mount, counter weight shaft and ota so I can get consistent balance each time I set up.

Rick

[muletopia (Chris)]

Thanks Rick,

All is mounted on a permanent pier in my ob. The sus part is guiding the HEQ5-Pro
at that focal length. BUT I am about to go out and start work to set up a new mount which I collected yesterday.

Camera tilt.
The camera hangs out the back of the Orion thin off axis guider, it is far from rigid.
So some how that has to be fixed.

Chris