SkyWatcher on Saturn

matt · #1 05-03-2006, 03:04 PM

Here's another SkyWatcher 8" capture from last night. This time a Saturn image.

This one was done earlier than the Jupiter posted previously. Taken around 10-30 with the planet close to the meridian.

Same as usual: NexIamge and Powermate 2.5x, 10fps at 1/10th of a second. About 10% gain (due to atmospheric moisture), brightness around 50%.

About 700 frames in Registax, medium wavelets. Nothing else.

Seeing 4-5/10... transparency I'd guess about the same.

Robert_T · #2 05-03-2006, 05:18 PM

Hi Matt, nice shot, bands and cassini very clear. There is a touch of softness - how's your collimation on the skywatcher?

cheers,

matt · #3 05-03-2006, 05:28 PM

Rob

I thought collimation was good.

It star tested very nicely at 165x. Seeing wouldn't let me crank it any higher.

There was a lot of moisture around last night and the planet was not very stable on the laptop screen.

Reckon that might be the prob?

matt · #4 05-03-2006, 06:13 PM

OK

Now i'm officially depressed!

All the planetary images I've captured and processed using an 8"f5 newt and a 9.25 f10 SCT look "soft" in regard to focus.

I've performed all the usual tests (sight tube/cheshire, star tests etc) and still my images fail to reveal crisp detail.

Could it just be the seeing/transparency or are both scopes out of collimation?

Keep in mind I've only ever imaged during the warmer months and have yet to capture during those "special" pre-dawn hours.

asimov (John) · #5 05-03-2006, 07:28 PM

Put your mind at ease Matt...it's got to be the conditions if you receive the same problem in two different scopes surely..

matt · #6 05-03-2006, 07:40 PM

I hope so Asi.

I'm pretty sure the separation in blue and red I'm seeing on the laptop screen at planetary limb is due to atmospheric dispersion caused by moisture/humidity.

And that's not good for seeing or imaging.

But I'll always keep an eye on collimation. The thing is I reckon my collimation skills are at 85 to 90 percent. It's always that last 10 percent or so in our ability that makes the huge difference though, eh mate?

Robert_T · #7 05-03-2006, 08:15 PM

Hi Matt, if the image was swimming or bloating on the screen then seeing was poor and that's going to be the major cause of any softness. It seems seeing is about 80% of the job with all the other stuff we play with, collimation, focus etc the other 20%. Don't Panic, it'll all start coming together soon.

Have you got an electric focusser?

cheers,

matt · #8 05-03-2006, 08:27 PM

No Rob. No electric focuser. Which is another of those 5 percenters. Will definitely help with imaging. Along with a dew heater system, and a few other handy bits and pieces.

They're the next few projects which will help take the imaging along a step or two.

Robert_T · #9 05-03-2006, 08:56 PM

I went "cheap" as far as electric focussers go and got the meade version at $399AU. It did make a big difference (maybe 10%) in my case as I'm using fairly lightweight (read wobbly) mounts so hands off focussing is great,

cheers,

ving (David) · #10 06-03-2006, 11:36 AM

hmm... i didnt want to be the one to sugest this matt, but all your images as you have stated are a little soft... how is your eyesight? if you are focusing to your eyesight and your vission is other than 20/20 would it show up as being soft?

matt · #11 06-03-2006, 12:12 PM

Yeah. It crossed my mind too, Ving, but a few things then came to mind.

1) I only recently had to renew my driver's lic. here in the ACT and passed the eyetest with flying colours. Not sure how much of a guide that is, but has to be good enough surely?

2) So far I've always imaged with someone else there to verify focus on the screen.

I have noticed a small amount of loss of focus in my right eye, but that's only on distant objects and my short sight tests as excellent.

Maybe I need to get them tested by an optometrist but like I said, all the above suggest something else????

asimov (John) · #12 06-03-2006, 01:04 PM

My eyesights not the best either (being a welder for over 20 yrs) but I manage to get good focus (according to the guys in IIS) I've only got the standard cheese-grater focuser on the refractor..Admittedly, I have a radial arm on one focuser knob which makes life a hell of a lot easier.

Yes, I'm getting that red/blue separation on the screen too lately. From past experience when that happens, the final resultant image is usually not all that great.

matt · #13 06-03-2006, 01:34 PM

Thanks Asi ... that's sort of reassuring. Sort of....

I'm still going to go and have a proper check-up at the optometrist to find out exactly where the ol' eyesight's at. Not just for astro reasons but coz you should get 'em checked every cuppla years anyway.

It would be nice to eliminate that as the reason for my blurry images. I'm not sure that's the reason though. I don't need glasses for reading or watching tele, and even small print within a few feet I can read crystal clear.

I'm almost certain I've just had crap seeing/tranparency on the half dozen or so nights I've attempted to image? Surely that's a distinct possibility, along with the focuser and other handy gadgets which would make life easier. Has anyone heard of anyone having night after night after night of poor seeing when it comes to imaging?

That's actually an interesting question. I'll start a new thread.

But I think the coming months of cooler more stable nights and lower humidity will be the clincher.

And then there's collimation....