25 replies to this topic

[Charlie Hein]

D.A.R.V (Drift Alignment by Robert Vice)

By Robert Vice

[Scott in NC]

Very nice! Thanks for sharing that information, Robert.

[highfnum]

nice i going to try it

[Takashi]

Really cool! Will try this as soon as possible.

[Littlegreenman]

I don't do astrophotography, so I don't need this level of alignment. But, I do appreciate clever thinking!

LGM

[Raginar]

Robert,

You mention that the corrections would be different for a GEM and I guess I don't understand why that is so. Can you clarify?

BTW this is probably the best example I've found. The pictures really clarified what I'm looking for from my image.

Chris

[Traveler]

Robert,

You mention that the corrections would be different for a GEM and I guess I don't understand why that is so. Can you clarify?

Chris

+1

[Doc Bob]

Thanks Robert,
I keep reading posts/articles referencing "drift alignment". I understand what it is but not having a GEM go-to mount, I havn't really paid any attention to technique. This does help lots! I eventually will go the rout of a GEM mount for my refractors.

Good viewing!
Bob

[Maverick199]

That is an excellent idea, thanks. Hope someone or I try this out with a GEM and report results. Only wish I had dark skies.

[Lightning]

Cannot for the life of me thinking why GEMs should be adjusted any differently to a fork. Perhaps he means the actual adjustment knobs will be in a different place? No idea.

[Raginar]

Lightning,

I can't think of why it would be different either; minus the actual motions of the GEM. But you should figure that out when your "V" is bigger or smaller based on how you move it.

This is the best example I've seen though. I'm really glad he put it together since i was hoping to learn this technique this year.

[hcsceo]

Man I wish I had read this before I started my imaging run tonight. I'm definitely going to give it a go. I've been using PHD but this looks much easier.

[Jerry Hubbell]

This method has been around for a long time. I first discovered it several years ago as described by Dr James Hall. For a thorough explanation see:

http://www.minorplan...aralignment.htm

I also describe this method in my book and provide a complete procedure also in chapter 12.

http://www.amazon.co...actical-Astr...

[Raginar]

Hey Jerry,

Your explanation is good too! Thank you for posting the follow-up information.

[Jerry Hubbell]

Thanks Chris,

I meant to post the link to the original source... Jim Hall
http://www.physiolog.../hall/polar.htm

[astrnmr]

Hey all, thanks for the comments. Sorry it has taken so long to respond. GEM mounts function slightly different in respects to the OTA positions as well as the need to "flip" the OTA direction once it is moves from East to West. When this occurs, your image is now reversed. Therefore, depending on whether or not you "flip" the OTA over, your adjustments may or may not change. A fork mounted scope never reverses the image while moving from E to W and eliminates the possibility of having to reverse your adjustments.

[Lightning]

Thanks Jerry, that makes sense!

[corduroy]

Hey all, do you think this method will work on a curved bolt barn door tracker like this? I believe the barn door tracker is rotating along the RA axis. I have my barn door mounted to a pan/tilt head on a a tripod so I can adjust the azimuth and altitude albeit not precisely.



The DARV instructions states to move the mount to the west and then to the east. Is moving W or E the same as rotating about the RA axis CW or CCW?

[Ernst Marais]

I am from the Southern hemisphere, so I take it I should point North in setting up?

[F.Meiresonne]

I don't quite understand it completely.

 

For the altitude one use thesame movement of the telescope , so moving it in RA again to the west? as for the azimuth?

 

And why a 6 mag star? Rather have a bright one to point the telescope and camera to

 

Then the issue remains on how to move the mount , confuses me al the time,the second exposure will make it better or worse but in the end this is a trial and error method , and those Always cost time...and you have to remember your previous steps. Really i have trouble with this...

[timshea]

D.A.R.V (Drift Alignment by Robert Vice)

By Robert Vice

Did this last night. Worked like a charm. Simple after a few tries. Thanks so much for posting - super helpful when Polaris isn’t in view. 

 

I did 180 second trails. 90 sec out & back. Maybe 3-4 passes on each axis, rechecking each once. You can get quite accurate alignment this way. 

 

I used the compass and (mostly) inclinometer apps on my mobile phone. First to set true north and level everything. Then to quantify my adjustments in response to the star trails.

Edited by timshea, 17 August 2020 - 08:50 PM.

[timshea]

I don't quite understand it completely.

 

For the altitude one use thesame movement of the telescope , so moving it in RA again to the west? as for the azimuth?

 

And why a 6 mag star? Rather have a bright one to point the telescope and camera to

 

Then the issue remains on how to move the mount , confuses me al the time,the second exposure will make it better or worse but in the end this is a trial and error method , and those Always cost time...and you have to remember your previous steps. Really i have trouble with this...

Once you try it, it becomes easier. Basically:

 

- Align mount as best you can manually. 

- Point the scope south (at 0 DEC). Move it east and west. Adjust mount until “V”s become flat lines.

- Point the scope east (at 0 DEC). Move it north and south. Adjust mount until “V”s become flat lines.

 

Star magnitude didn’t matter at all for me. All 500 stars in view made the same “V” shape.

[hatflyer]

D.A.R.V (Drift Alignment by Robert Vice)

By Robert Vice

I have only a DSLR, so I don't have an automated way to pan. Is panning by hand accurate enough? I guess as long as the other 2 axes are locked in it's fine? Actually, I cannot access declination of 0 (horizon). More like 15 or so. Would this still work?

Edited by hatflyer, 12 July 2022 - 09:38 AM.

[timshea]

You need to be able to take a 30 or 60 sec exposure while moving the mount, so doing it by hand might not work.

You can rough align with a compass and inclinometer.

[hatflyer]

Actually, I guess what really matters is the start and end points, right? I guess the lines add some clarity, but what matters is if your start and end points don't match, u have make adjustments.

I cannot get a star at the southern horizon, but only about 15 degrees above it. Will that still be useful?