ThriftyAnvil

Had clear skies last night so decided to have another attempt at the Orion nebula.

This is the result from 120 stacked frames, 30s exposures at 1600 ISO

Untracked with my Celestron C8 on a byers drive

Canon 450D unmodified

May try for some longer exposures on lower ISO tonight but unsure how long before I start to see trailing

5 hours ago, michael8554 said:

....This adapter gives the correct FR Back Focus with a Canon DSLR:

https://www.firstlightoptics.com/adapters/celestron-sct-t-adapter.html

Thanks for the support Michael,

That adapter is the same one I am using currently, I have had a brief look into field reducers but haven't gotten to the point that I'm 100% sure which one I need etc

I get a bit impatient and want to take the photos more than do the research, but i guess learning is half the fun!

5 hours ago, rickwayne said:

You can check your alignment with nothing more than your camera and the ability to slew slowly back and forth in RA. Basically you start an exposure, deliberately make a star trail by slewing during the exposure, and then slew back. If your PA is perfect the "out" and "back" trails coincide and you see only a single line. If not, then some DEC drift occurs -- remember this happens at right angles to the RA axis -- so the lines form a V, with the point of the V where you reversed direction.

Here's a detailed recipe, see Drift Alignment by Robert Vice (aka DARV).

Oh yeah, that seems "easy" enough

Ill probably spend the next clear night playing with alignment more than any imaging

Thanks for the tip

16 minutes ago, vlaiv said:

Ok, so I looked it up - and there is handy star that will put you in vicinity of SCP - close enough for good tracking.

Here is quote from wiki article:

Not sure what your mount is like - but there are two things that you need to do to get good enough polar alignment.

First is to make sure your polar scope is properly aligned (once you get polar scope onto any star - best use one close to pole as those don't move much - then if you rotate mount in RA manually - star should stay in center of the polar scope - if it's not align polar scope first - look up polar scope alignment / adjustment).

Then simply put cross of polar scope on BO Octantis and you are done (using alt / az controls at base of your EQ mount).

Excellent! A lot of good info there for me to try out some different things!

Now I just need to hope for some clear skies!

9 hours ago, vlaiv said:

....When you say "vertical" drift - what exactly do you mean? Vertical with respect to RA/DEC coordinate system or vertical with respect to the image above?

DEC drift (one in direction of DEC) - happens due to poor polar alignment....

Thank you for the welcome, and the detailed reply.

Based on your description I am having DEC drift, the target is moving from top to bottom along the center of the frame.

My tripod is level and my wedge is set at 46~ degrees which i believe is correct for my location, so am I right in thinking that it is my North South alignment that is wrong?

12 minutes ago, PeterCPC said:

As I understand it the byers drive will severely limit your exposure time. The main issue in your image to me is that it is out of focus.

I have been struggling a bit with the focusing, theres a lot of movement when I touch the dial, and the cameras LCD screen doesnt give me the best view

I will keep practicing when the weather permits

I appreciate the reply

Hi all,

New to astrophotography and have recently started imaging the Orion nebula (see attached photo)

My setup is Cannon 450D and a Celestron C8 super with byers drive for tracking.

The main issue I'm facing is "vertical drift" in my images/tracking which limits my exposure times to 30s at the very most and i cant for the life of me figure out which part of my alignment is causing this.

Any help or advice would be much appreciated