how do i get good focus?

[neil groves]

I just DSS'd  my subs and found they are out of focus, when I put the camera to the scope, I took a shot and found the camera wasn't lined up parallel in the eyepiece hole so I corrected this then tried to refocus, it is sooo difficult to see when the stars are sharp through the camera viewfinder, what is the best way to ensure sharpness please? I am using a Canon T3 at prime focus? is it necessary to take a shot and check it on the computer screen first before taking the subs?

Neil.

[Tinker1947]

Use one of these, they come in the right size for your scope......

http://www.firstlightoptics.com/bahtinov-focus-masks.html

[Huskvarna]

Hello!

Have checked the Bahtinov mask?

http://en.wikipedia.org/wiki/Bahtinov_mask

And

http://astrojargon.net/maskgenerator.aspx

If you manage to find a relative bright star and use the viewfinder max zoom you should be able to see the spikes and use them to focus.

Hooking up the camera with a usb cord to a laptop and using eosutility to see the live-view on the screen makes it of course easier to focus, but that requires a laptop...

[Owmuchonomy]

As above with the appropriate mask. However I believe a T3 is the same model as the 600D in the UK. This is what I have. I find I can manage without a mask. Slew to a bright star, centre it on the LCD screen in live view mode. Press the mag button (top right) twice to get 10x zoom. Focus on the star with the scope focusser. You now have focus so don't touch any more. Slew to your object and record your images. Check every so often.

[ronin]

Doubt FLO will ship to East Bay, try these similar but not a Bahtinov:

https://www.astronomics.com/telescope-focusing-masks_c424.aspx

Agena Astro have these:

http://agenaastro.com/catalogsearch/result/?q=bahtinov+mask

Description seems a little "short" as the specification for a Bahtinov is given by hte scope dia and focal length and there is not enough on the AA site. FLO I think custom cut each mask to the scope specifications.

Should mean you can make your own with good black card, scalpel and patience.

Optcorp do much the same as AA

http://www.optcorp.com/catalogsearch/result/?q=bahtinov+mask&order=relevance&dir=desc

[Alien 13]

It is possible to get perfect focus using liveview on x5 on the faintest star in the FOV by using the ISO setting until it is only just visible the focus will then be an on/off action so no need to faff around with a bat mask.

Alan

[neil groves]

As above with the appropriate mask. However I believe a T3 is the same model as the 600D in the UK. This is what I have. I find I can manage without a mask. Slew to a bright star, centre it on the LCD screen in live view mode. Press the mag button (top right) twice to get 10x zoom. Focus on the star with the scope focusser. You now have focus so don't touch any more. Slew to your object and record your images. Check every so often.

I have live view?.....I didn't know that

Neil.

[wxsatuser]

As above with the appropriate mask. However I believe a T3 is the same model as the 600D in the UK. This is what I have. I find I can manage without a mask. Slew to a bright star, centre it on the LCD screen in live view mode. Press the mag button (top right) twice to get 10x zoom. Focus on the star with the scope focusser. You now have focus so don't touch any more. Slew to your object and record your images. Check every so often.

A T3 is a 1100D.......a 600D is a T3i........one tiny letter big difference in camera.

[wxsatuser]

I have live view?.....I didn't know that

Neil.

Whichever camera you have, just press the Liveview button on the back.

It's normally the one that looks like a camera with a red dot.

When you press it in normal shooting modes the mirror will flip up and the lcd screen

will show the liveview. This button also controls video as well, in video modes.

You can zoom the view with the two buttons marked with the magnifying glass + and - .

You can take exposures while in Liveview, you won't here the mirror flip as it's already up.

[neil groves]

I better sleep during the day on Friday then, could be a long night ( dusk to dawn session) ha ha

Yes focusing is biggest issue right now, well....along with polar alignment, and ...ummm...getting to grips with post processing and ....ummm...IT AIN'T EASY DAMMIT  

Neil.

[Carina Lass]

To get great focus, you need to sleep well the night before and concentrate on the task in hand.

Also it may help to be in a quiet area with no distractions

lol ,sorry it takes me a while to settle...

a batinov mask is the only way I managed to get it truly correct.

I made my own an I get a nice pattern that gives me perfect results.

[neil groves]

omg Carina....where are you going with this lmao

Neil.

[neil groves]

ok now I need to go look up batinov masks

Neil.

[neil groves]

Amazon don't make one for the ED120.....dammit.

Neil.

[neil groves]

can someone tell me the correct one from amazon (that's where I shop)  for the skywatcher ED120 please?

they are expensive but probably worth it compared to a couple hours imaging with blurred results.

Neil.

[Steve Ward]

https://www.astronomics.com/focusing-aids_c270.aspx

[Tinker1947]

Here is a list shown in Amazon.com 

http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=Bahtinov+Mask&rh=i%3Aaps%2Ck%3ABahtinov+Mask

[neil groves]

Great Tinker, which one do I order for the 120mm? I think it's 4.7" and I don't see one for that diameter OTA?

Neil.

[neil groves]

ok so it looks like this one is the one right?

http://www.amazon.com/Farpoint-FP401-Bahtinov-Telescopes-Diameter/dp/B003T8FXXE/ref=sr_1_3?ie=UTF8&qid=1401297069&sr=8-3&keywords=Bahtinov+Mask

cheaper than I thought.

Neil.

[Tinker1947]

That's the right size,,,and cheap..

[happy-kat]

You can take exposures while in Liveview, you won't here the mirror flip as it's already up.

Unfortunately my t3 if I shoot in live view the mirror still bounces down and then up again. So potential is worse shake then just normal shoot.

[wxsatuser]

Unfortunately my t3 if I shoot in live view the mirror still bounces down and then up again. So potential is worse shake then just normal shoot.

I did'nt know that.......worth knowing.

I don't normally shoot in Liveview but on the odd occasion have forgotten it was on.

[Tinker1947]

My 600D the mirror stays up when in live-view if i take a shot....if i do a run of images it stays up all the time......