Great Hercules Cluster - Help needed for beginner

[AlistairW]

Hello,

Had a go at the Great Hercules Cluster. This was ISO 800, 15 subs of 5 mins each + Darks + Bias. The stars appear bloated, is that simply focus ? - I was guiding with PHD, - but this is still all new to me. Still very happy with these initial attempts. But need help knowing where to look to improve.

Thanks

Alistair

[swag72]

Focus can make or break an image and you've not quite got it bang on in this one. How do you focus? I find that if you are not using an electronic focuser then a Bahtinov mask is excellent. I used to use mine in conjunction with Bahtinov grabber  - An insanely brilliant piece of free software that works every time. It will revolutionise the way that you focus and it will be perfect night after night

[AlistairW]

Hi,

I am still not having success with the Bhatinov at moment. I have both the grabber software and Backyoard EOS. I get as far as the attached picture below using LiveView, but I think this is where my problem is. How can I improve my technique ? I tried putting the grabber image area over this, but it seemed to jump around a lot, but did say it was within "Critial Focus" area. It all seems a bit blurry compared to the lovly stable Bhatinov images I see on this site.

Thanks

Alistair

[swag72]

How long are your exposures when you use the Bahtinov mask? I use 5s normally, but will up that to 7 or 8 if needed when I focus Ha on a slower scope.

[AlistairW]

Hi,

Ahh, maybe this is where I am going wrong. I am using the Live View. Should I be taking "still" images and looking at the results ?

Thanks

Alistair

[Stub Mandrel]

+1 for a Bahtinov Mask:

Your mileage may vary....

[glowingturnip]

exactly as Sara says - I use a bahtinov mask and take something like a 10s high iso exposure with APT, put the bahtinov grabber window over the top, and can get critical focus every time, usually within 3-4 tries

[AlistairW]

Think the bit i was missing was analysing still images - i have been trying to do it all real time through live view

Thanks

Alistair

[swag72]

Hi,

Ahh, maybe this is where I am going wrong. I am using the Live View. Should I be taking "still" images and looking at the results ?

Thanks

Alistair

No you should use live view, but loop at exposures of 5s as a minimum. Your system will dictate the idea exposure time in order to get the pattern strong enough for Grabber to pick up. Also, make sure that in grabber you have your settings right as this will impact upon where it thinks your critical focus point should be for example.

[AlistairW]

Understood. It's the looping of 5 second exposures I wasn't doing. Understand now - great - thanks.