Drift Alignment

[Kaliska]

Just wondered if anyone knows what might be happening here? I'm trying to get my scope as accurately polar aligned as I can and I've been trying out the DARV method.

The scope is currently pointed due south at near celestial equator and I'm pressing the North and South keys and getting closer to the solid line. Trouble is that the lines are quite wavy as you can see? Is this a potential mount issue?

 

[michael8554]

Haven't used DARV but I thought it used E and W buttons, not N and S?

The wavy bits are Dec wobble I'd guess.

Michael 

[symmetal]

I assume you mean you're using the East/West keys to generate the DARV trails. Is the scope balanced slightly camera heavy (or front heavy, either will do) to avoid the Dec axis 'floating' between gear teeth, which could be a reason for your Dec wavyness. It can also be helpful  to rotate the camera so that the East/West trails are horizontal on the image. APT has a built in DARV option which takes care of driving the mount E/W for a specified duration.

Alan

[Kaliska]

Sorry, yes, E/W keys. Shame SGP doesn't have a similar DARV option, that would be helpful.

Thanks for the replies guys.

[Thalestris24]

Hi

If you have a guidescope, use the PHD2 drift align tool - it makes life much easier!

Louise

[Kaliska]

2 hours ago, Thalestris24 said:

Hi

If you have a guidescope, use the PHD2 drift align tool - it makes life much easier!

Louise

Ah, I forgot about this tool. Think I've tried it before, but that was some time ago, with okish results. I've now got the mount on a pier, so I think I'll run this again. Thanks for the reminder ?

[ollypenrice]

On 08/09/2018 at 03:25, symmetal said:

It can also be helpful  to rotate the camera so that the East/West trails are horizontal on the image. APT has a built in DARV option which takes care of driving the mount E/W for a specified duration.

Alan

This will work unless the scope is pointing towards the zenith. At the zenith itself any fore-and-aft imbalance will reduce to zero.

Another way to avoid floating across the Dec backlash is to be slightly polar misaligned and to guide only in the one Dec direction needed to compensate for this.

Olly

[symmetal]

4 hours ago, ollypenrice said:

This will work unless the scope is pointing towards the zenith. At the zenith itself any fore-and-aft imbalance will reduce to zero.

Another way to avoid floating across the Dec backlash is to be slightly polar misaligned and to guide only in the one Dec direction needed to compensate for this.

Olly

You're right Olly. I forgot to mention that if I'm pointing near the zenith I hang a little weight off to one side to provide some added Dec imbalance.

I am slightly polar misaligned, more down to alignment lazyness rather than intention, which helps too until a dither in Dec happens which drives the scope across the backlash zone. It can take ages to settle as guiding may drive it several times back and forth over the backlash zone before settling. Having a Dec weight imbalance also helps reduce this settling time.

Alan