Capturing Starlight

[SStanford]

Hi All,

For what has seemed like forever, the clouds finally parted late last night and the Orion constellation was very clear from my balcony.

I had a brief window of opportunity earlier this week and had difficulty focusing on stars at all using my DSLR (Canon 450D) and APT. 

Last night was a breakthrough; I was able to capture starlight in APT liveview and even bring the stars into (significantly better) focus!

I now face my next challenge; I am unable to focus sharply on any of the stars.  Using my telescopes focusing wheel I seem to get only blurry spots of light coming through, despite very carefully adjusting the wheel for quite some time.

At the risk of embarrassing myself, I've attached the images of Rigel and Betelgeuse I captured last night (on both long and short exposures, details of ISO and exposure are detailed in the image titles). This is as sharp as I can them.

Is there anyway I can fine tune the focus? I've seen AP videos on Youtube where jam jar lids have been glued to the focus wheel or motorized focusers attached. Are these gimmicky or do they make a significant difference?

I should mention that I don't yet have a tracking mount:  I've eyed the Skywatcher AZ-GTI wi-fi as good candidate for my first meaningful mount (with the EQ wedge coming shortly after).  Having emailed a number of retailers it seems these are in very short supply, here's hoping stock replenishes post-Christmas! I think this will let me get to grips with the equipment I have right now, definitely would like to get a sharper image, even if I'm only capturing star trails.  

to capture the images shown below I used:

 - Celestron 100AZ (100mm Aperture, 660mm focal length)

 - Canon 450d 

 - Barlow lens x2 (Celestron)

 - APT (connected DSLR directly to laptop via USB)

 - Stock Celestron Alt-Az Mount

All the best.

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[wimvb]

A bit late, but since you haven't got an answer on this question, here goes.

Your best, and cheapest investment in this hobby is a bahtinov mask. You put it in front of the telescope when focusing. The mask will produce diffraction spikes in an X pattern with an overlappin I. When the pattern is symmetrical (the I on top of the X), you have best focus. You can buy a mask from almost any astronomi retailer, or make your own.

https://www.firstlightoptics.com/offers/offer_starsharp-bahtinov-focus-masks_72309.html

[SStanford]

Thanks Wimvb, 

I invested in a bahtinov a few weeks ago; works a treat.