focussing advice

[iantobach]

just starting out on ccd imaging- with DSI 2- on a a 10inch lx90- with a meade 3.3 focal reducer.

the problem i have is focussing- tried using a parfocal 32mm eyepiece- and have so far just about managed to get grainy images of a field whislt practicing during the day- but it takes hours of fiddling.

any tips of focussing??

and is there a more user friendly program that works with dsi 2- other than autostar suite??

thanks

[GordonCopestake]

GOTO a star nearby your target and use that for focusing then GOTO back to your target for the exposure. Or manufacture a hartmaan mask from card and use that to get a perfect focus. You can use parfocal rings to get an eyepiece exactly right, but you can't really do it in the day as it's hard to focus at infinity. No idea about DSI software sorry

[MikeD]

I find the best way is to use diffraction spikes generated by the secondary spider on my newt and a bright star. just focus until you get the sharpest diff spikes you can, job done.

I also use this method with my 80Ed refractor by adding a wire cross in front of the objective lens.

Hope this helps

[iantobach]

thanks guys- i`m going to try a hartmann mask- if the clouds ever clear!!

[Chubster]

Thats why I love this forum....So if I get a star in focus, then swing round to Saturn I do not need to touch the focus again, correct?

Chub

[GordonCopestake]

Correct, but make sure it's a close star or "things" can happen, like mirror flop, or any one of a million other things. Also even then seeing might thwart you!

[Chubster]

A "close" star And what is mirror flop again?

Chub

[Kai]

The way a Sct mirror is held there is a small amount of play in the focusser and as the scope moves the mirror "flops" on the thread on ther focusser so the image shifts.

Also if you hold your focusser at the end and "wiggle" it you will see the image shifting.

This is why i went to a Moonlite as it cuts down the image shift whilst i fine focus.

I could post some images i had of Saturn last year taken pre moonlite as a example but i wouldnt want to scare you :shock:

[anthony]

If you get a bit of fishing string you can tape it across the front of the lx90 making an equivalent of the crosshairs that Mike referred to. Easy and quick. You need to make sure that there is tension in the string to get a nice crisp set of spikes.

Anthony

[proflight2000]

so for instance, if I wanted to catch some images of the M64 (not the motorway chub) would the spike trick still work in relation to maybe something i can just about see when I then move to the M object?