My journey has began

Post by **Airconvent** » Sat Aug 13, 2011 11:10 pm

Good effort bro and from a first timer too! [smilie=crying2.gif]

cloud_cover · Post by **cloud_cover** » Sat Aug 13, 2011 11:28 pm

I have a spare Televue SCT to 2" adapter. PM sent

orly_andico · Post by **orly_andico** » Sun Aug 14, 2011 1:18 am

could still be some slop in the T-adapter.. i'd check that out first. i've never tried sticking a DSLR onto the back of my C9.25 (I'm not a glutton for punishment, imaging at such a long focal length is bound to be extremely challenging)

cloud_cover · Post by **cloud_cover** » Mon Aug 15, 2011 1:58 am

And there I am thinking of trying BOTH off-axis guiding and imaging with a 2000mm f/10 scope......

kaomoo · Post by **kaomoo** » Mon Aug 15, 2011 2:02 am

hi guys
opinion

i reshot the moon today... still feels the the relief is sharper on one side than the other side...

though i am starting to think it's not focus issue, but direction of shadow?

kaomoo · Post by **kaomoo** » Mon Aug 15, 2011 2:08 am

and yes, i think i need a micro focuser....

this is sweet.....

Gary · Post by **Gary** » Mon Aug 15, 2011 2:22 am

Or this:

http://www.jimsmobile.com/buy_motofocus.htm#Celestron

cloud_cover · Post by **cloud_cover** » Mon Aug 15, 2011 2:34 am

Focus is always an issue when taking pics - the problem is that the viewfinder on the DSLR is often not good enough for the low-light enviornment of astronomy.
One way is to boost the magnification of your liveview to max and judge from there.
Another way is to focus on a nearby bright star, then again magnify to max on liveview and focus until it is the smallest possible dot on your liveview. Then slew back to the moon
Taking things a step further, you can get a Hartmanns' or Bhatinov mask, use those as focusing aids (works only on bright stars), lock the focus then re-slew back to the moon.
Micro-focusers are nice but I've found that simply brushing the focuser with your fingers instead of gripping it often produces a good result when trying to fine-focus. Of course this requires a little bit of finger dexterity

kaomoo · Post by **kaomoo** » Mon Aug 15, 2011 2:34 pm

I need an opinion. I am checking out micro focuser.
Between a Williams Optic 2" DDG SCT Focuser and a Starlight feathertouch SCT microfocuser (they are going for nearly similar price), what would you go for?

orly_andico · Post by **orly_andico** » Mon Aug 15, 2011 2:53 pm

I'd go with the Williams.

Here's the thing - the Starlight focuser is basically a 10:1 reduction that goes onto your existing focus knob, which moves the mirror in and out. i.e. it adds a gear-down for fine focus but the focusing mechanism is still the same and you still have to deal with mirror flop.

mirror flop is quite large, you can drive Jupiter off the edge of a small (Toucam) imaging chip just with the flop.

whereas the Williams crayford is a completely separate focusing system that doesn't move the mirror at all, hence no flop. The only side-effect is that it reduces the back-focus quite a lot (since it is long) so you have to rack the built-in focuser in quite a bit which lengthens the focal ratio to around f/11 (from f/10).

Personally I went for the crayford (non DDG) because mirror flop at high mags drives me crazy.