DSO questions.

[guiseppe]

So, I've made a few threads asking about motors, DSLR's and Barlows. Good news is, I got it to work (somewhat). The motor drives are working as they should, at least to my knowledge. I'm still getting trails on longer exposures, but I'm guessing that's down to me not polar aligning, wind and general "not quite sure about what I'm doing"-ness. Anyway, first question: How on earth am I supposed to focus on an object that I can't see? How do I know that I'm on target with my focus? I can't see it through the camera's live view mode. Second question: Does polar alignment need to be 100% perfect for longer exposures (I'm thinking 3-600 seconds). And if so, how do I accomplish that? Third question: I've looked in to getting a polarscope, but I can't figure out how to mount it to my... Mount. The counterweight bar is in the way. My mount is an EQ 3-2. 

And finally, here's what I took of the Orion nebula tonight. First time with motor drives. 30s exposure, ISO 800.

[Alien 13]

I am a bit supprised that you cannot see anything with the camera live view i can see lots of details and some of the fainter stars, when focussing make sure the ISO is set to its highest setting and shutter speed to 30 seconds this will give you a brighter image on the screen and zoom in onto a nearby star then focus (I find focussing easier if if you choose a faint star in the field of view). After focussing reset the camera ISO and shutter speed back the the required levels.

The mount counter weight bar needs to be unscrewed until the polarscope hole is visible then locked into position.

Polar alighnment is critical i normally set mine by using the hour angle in stellarium but "polar finder" gets you close.

With all of the above done you should be able to get subs of between 20-60 seconds but thats about the max you could do with your scope and conditions would have to be ideal with no wind etc.

Alan

[Astrosurf]

Have you tried a Bahtinov mask? I couldn't focus without it. FLO sell them. I focus on any bright star, zoom in to 10x on live view, and focus from there. As Alan said, I can't understand why you're not seeing stars. That camera is brilliant.

Have you tried drift alignment? I've not done it, but after some practice it's supposed not to be too onerous. It'll get your PA pretty accurate.

I can't help with the polarscope, sorry!

Never give up; never surrender!

Alexxx

[Physicist13]

Bahtinov is a v good suggestion!

Also focus on a nice bright star...the lock the focus and move to your target.

You can calc how accurate the polar align needs to be for any partic setup and req exposure time.

You are more likely to be limited in exp time by periodic error but it does depend on the mount.

Go with the longest exp that your setup will allow...ie whts the longest exp that any trailing is acceptable to you.

Then take as many exp at that exp time as possible,..calibrate and stack etc....

P

[guiseppe]

Somewhere in the back of my mind I knew about the settings for focusing with live view. I guess I was just so excited about finally getting everything up and running that it slipped my mind. And I'm also guessing that a properly balanced scope helps a lot, something I also neglected last night.

Thank you so much for your help.

[Astrosurf]

Let us know how you get on.

[Physicist13]

Liveview can be a bit of a pain I find. I usually set to highest ISO for this and this seems to kick the liveview into going! Then obv, reduce the ISO to the imaging level.

Be aware that if the focus is off a bit too much the star/s dont show at all on liveview...so I prefocus roughly on moon/Jupiter, anything obvious first by eye then goto liveview on v bright star..then Bahtinov if I cba.

P