First Light with the ST8

sheeny (Al) · #1 15-04-2010, 06:03 PM

I've finally processed it.

... and here it is warts and all.

This was captured with the ST8i, CFW8A and Olympus Zuiko 100mm f/2.8 lens at f/2.8 (

I can't remember now... maybe I stopped it down one stop?). This was captured at -10°C with the Custom Scientific clear filter, so there is no IR blocking, dark frame subtracted and no flat - single 10 minute exposure.

Focus was fiddly to say the least, even with a Bahtinov mask/racquet. I couldn't get clear diffraction spikes on screen, but I could get the distorted star shapes symmetrical as I adjusted focus, and I checked using the CCDOps focus tool. I'm not sure how much of the focus problem is IR and how much is just ordinary focusing on my part...

.

It is certainly different working with 16 bits, and not particularly easy with a lens and clear filter combo

. I'm tempted to take the lens off for a while and practice with the ED80 where I can at least attempt to find or set up a parfocal EP to aid focusing

. I might have to take the plunge and buy a new CS L filter so I get some IR blocking too...

Al.

rogerg (Roger) · #2 15-04-2010, 06:36 PM

Nice camera. I've long wanted to upgrade my ST7 to an ST8 or ST10.

I've found using focus masks in CCDSoft hasn't worked well for me, not quite sure why. Might be similarly tricky in CCDOps for whatever reason. I've only tried in CCDSoft with my DSLR, not ST7.

10 mins is pretty long for Eta, F/2.8 (or even slightly slower) & an ST8! I'm surprised it's not burnt out more than it is

multiweb (Marc) · #3 15-04-2010, 06:47 PM

Not bad Al. Try shorter exposures but loads of them and try on better focus with the bathinov. Then take it from there. You'll be surprised with what you can get.

sheeny (Al) · #4 15-04-2010, 07:37 PM

Quote:

Originally Posted by rogerg

Nice camera. I've long wanted to upgrade my ST7 to an ST8 or ST10.

I've found using focus masks in CCDSoft hasn't worked well for me, not quite sure why. Might be similarly tricky in CCDOps for whatever reason. I've only tried in CCDSoft with my DSLR, not ST7.

10 mins is pretty long for Eta, F/2.8 (or even slightly slower) & an ST8! I'm surprised it's not burnt out more than it is

It didn't saturate the raw file

. I clipped the top end a little bit trying to get some reasonable contrast and bring out some nebular detail. 16 bits of dynamic response is a new learning curve for me!

Quote:

Originally Posted by multiweb

Not bad Al. Try shorter exposures but loads of them and try on better focus with the bathinov. Then take it from there. You'll be surprised with what you can get.

I'll work on it.

Al.

Omaroo (Chris Malikoff) · #5 15-04-2010, 08:02 PM

Hi Al

Great to see the camera out in the dark again.

I had best success with the ST8, Bahtinov masks and camera lenses pointing at a medium star and exposing for around 10 seconds through a luminance filter. The spikes were very pronounced at that exposure. I used to run my favourite, a Nikkor 100mm f/2.5 on that camera at f/4 and f/5.6 for best results on Eta Carina.

Looking good - some experimentation, practice and you'll be flying.

sheeny (Al) · #6 15-04-2010, 08:26 PM

Quote:

Originally Posted by Omaroo

Hi Al

Great to see the camera out in the dark again.

I had best success with the ST8, Bahtinov masks and camera lenses pointing at a medium star and exposing for around 10 seconds through a luminance filter. The spikes were very pronounced at that exposure. I used to run my favourite, a Nikkor 100mm f/2.5 on that camera at f/4 and f/5.6 for best results on Eta Carina.

Looking good - some experimentation, practice and you'll be flying.

Onya Chris... I thought the L filter would be the go rather than clear with a lens / refractor.

I'll give those tips a try.

Al.

telecasterguru (Frank) · #7 15-04-2010, 08:32 PM

Al,

I can't believe how many stars there are in the field of view.

It is going to be awesome.

Frank

sheeny (Al) · #8 15-04-2010, 08:55 PM

Quote:

Originally Posted by telecasterguru

Al,

I can't believe how many stars there are in the field of view.

It is going to be awesome.

Frank

I think it has the potential to be awesome.

I have lots to learn though, which is good.

Al.

Peter Ward · #9 15-04-2010, 09:48 PM

Al....a fact 'oft lost on camera lenses is they are not APO objectives.

They are designed for non-point sources illuminated in daylight.

You will find by using a UV+IR block filter and 2-3 F-stops, some very tidy camera lens, wide-field results are possible...such as here...

http://www.atscope.com.au/widefield/m16m17hXp.jpg

Baader and others make UV/IR block filters & they are well worth including in your CCD imaging train.