DARV Problem

[Dannyefc87]

Hi, any help anyone can give is much appreciated.

Having major problems with drift alignment. Wasted two very clear nights trying to get it right and im no better off than when I started, if anything my alignment is even worse haha. Below is a series of images taken while trying to improve alignment. Started off by pointing towards a star low in the south.

Slewed to the west first IIRC then east 1 minute exposure 30 secs each direction. Cant make sense of this myself looks nothing like the images in tutorials for DARV.

Same again, had me even more befuddled haha. Give up on the south and decided to try and align altitude with something in the east.

So same again, 1 minute exposure, 30 secs slew to the north, 30 secs slew to the south. Figured this looked a bit more like in the tutorials but obviously alignment way out so I adjusted altitude bolts, up first to see what effect it had.

Didn't really seem to have any effect so I decided to decrease altitude on the next one and kept decreasing through the next 5 attempts and this is what I got.

Basically ended up adjusting altitude to way out of my location with no effect on the DARV even when making 10+ turns of the bolt so its left me a lil bit stumped to say the least. Any help is much appreciated.

[michael8554]

Hi Danny

According to the DARV instructions,  you had it spot on in your first two Az exposures - that is, your two lines are already superimposed !
I'm guessing you have a much shorter focal length than the author's 8" F6.3,  so you may need to expose for longer to show up any error.

For the Alt correction, you slew west and east again, not north and south!  Would have helped if that was mentioned in the instructions
That's why you have the chevrons, they're a mixture of your moves and the scope's RA drive.

Michael

[Dannyefc87]

1 hour ago, michael8554 said:

Hi Danny

According to the DARV instructions,  you had it spot on in your first two Az exposures - that is, your two lines are already superimposed !
I'm guessing you have a much shorter focal length than the author's 8" F6.3,  so you may need to expose for longer to show up any error.

For the Alt correction, you slew west and east again, not north and south!  Would have helped if that was mentioned in the instructions
That's why you have the chevrons, they're a mixture of your moves and the scope's RA drive.

Michael

Thx for the tip Michael, I had a feeling it must be something daft like that. I had another go at it just now came up with similar images to the first two after following your advice. Although I still doubt that I am actually aligned as I still can't even take a 30 sec sub without trails. I'm using a heq5 pro and equinox ed80 F6.5. I only roughly set alt and pointed towards north and got solid lines on both axis. Even tried a 60 sec slew in each direction and showing only one solid line still which is leaving me a bit perplexed.

[wxsatuser]

What you want to do is rough polar align first with you polar scope, this will get you near to start with.

Then for azimuth slew to a star thats about due south but not lowdown, the star should be on zero degrees DEC.
Here in the UK this star will be approximately 40degrees above the horizon.
Now set the slowest slew rate and press the West key, after about a minute stop.
After stopping, reverse by pressing the East key for another minute, you should be back roughly where you started.
You should now have a V shape or if your lucky two lines on top one and other.

For altitude find a star to the EAST thats on zero degrees DEC.
Most people cannot see a star near the horizon so pick a star thats still on zero DEC but higher up, this will push
the scope slightly south but don't worry about it.
Do exactly the same as for azimuth but this time adjust altitude bolts, DO NOT USE THE NORTH SOUTH KEYS.
This is why you got the L shape, only use the WEST EAST keys.
 

Here is one I did, think these were much longer exposures to get my obsy mount as accurate as possible.

[BargeGazer]

APT, excellent acquisition software, automates the DARV process thereby avoiding the need to remember N-S-E-W.  Just click the software button. 

 

David

[dph1nm]

One tip - don't use exactly the same exposure time for the East and West legs, and leave the telescope tracking for a few seconds at the end (and maybe shift it slightly in dec). That will make it much easier to see where each leg ends.

NigelM

[michael8554]

As I expected, a one minute exposure didn't show any divergence of the lines.

Try 2 or 3 minutes  in each direction, yes it may go off screen, but when it comes back on, the return track will be up or down from the out track.

As I think you have already realised, adjust the mount Az for the south star, and mount elevation for the east or west star, not the drive buttons. 

Nearly there

Michael

[Dannyefc87]

Been away for a few days, thx for the advice, hopefully it's clear tonight and i can give it another go