davidgr1976

3 hours ago, alcol620 said:

Thanks for your help Robin

I had exactly the same problem as yours in the past (the same jumps). I discovered that the problem was the parallax portable pier I have on the grass ( filled with sand 80kg). With the berlebach tripod disappeared. Now i'm building a concrete pier and retire the portable pier.

14 minutes ago, rwg said:

This is a good question and one I don't yet fully understand. The plate solving to find the position of the pole is accurate - just tested with a star field from Stellarium with the equatorial grid still in place and you can see how well it does - SharpCap ignores the blue equatorial grid from stellarium easily and puts its own NCP (green) spot on in the right place.

If you test when you have finished polar aligning in SharpCap by turning the mount on the RA axis, you should see the stars in view rotate around the point marked as NCP - this confirms that you are correctly polar aligned as the center of rotation is matching the NCP.

So... what does that leave? The only thing I can think of is physical flexing of the tripod/mount/pier as the load moves from the 'home' position with scope up and weights down to whatever position you run a drift align from. To be honest, I'd have thought that this shouldn't happen if you are have properly balanced the mount payload, but I'm not 100% sure. If this is the problem then you'd expect to see less change with a lighter load on the mount.

Any further thoughts on this welcome!

cheers,

Robin

 

 

Hello,

I like very much this piece of software. I always have done PA with drift method since i didn't have polaris view, and I usually leave PA error in some arcsec (15-30").

Now i have moved to another house where I can see polaris but can't point to neither west or east at 10-20 degrees altitude in the backyard.

I was considering on buying polemaster but i discovered this.

I've been testing it. I get 20" error but when i check it with PHD2 the PA error after 10min is 4 arcmin... What could be the cause of this big difference with sharpcap?

Thank you!

I haven't thought about pier flexure.... This could be an isue due to the weight in 3 points on the grass (about 110kg?).

I am going to put under de bases some wooden parts to avoid pressure n the ground.

Thank you very much!.

Hello,

I like very much this piece of software. I always have done PA with drift method since i didn't have polaris view, and I usually leave PA error in some arcsec (15-30").

Now i have moved to another house where I can see polaris but can't point to neither west or east at 10-20 degrees altitude in the backyard.

I was considering on buying polemaster but i discovered this.

I've been testing it. I get 20" error but when i check it with PHD2 the PA error after 10min is 4 arcmin... What could be the cause of this big difference with sharpcap?

Thank you!

Interesting. Can you try less than 46mm to see if it shows a trend? 

ok, I will try: 34 mm and 17. (I can't other spacings because I don't have rings for other distances). 

I will tell you. But this days are cloudy in Madrid....

thank you!!

If the flattener is an skywatcher one, it should be around 55mm.  I that sub is around 46mm. I tried with 55 and 60mm and the result is similar or worse....

Here is a pic of M31 taken with a WO66 and 1100D with APC size sensor (no flattener)

Does it look like this?

I think i have a skywatcher flattener ( ibought it second hand with the zs66sd and i doesn't appear nothing except "field flattener").

Here I pic of 600" in h-alfa:

thank you!

Welcome back to the 66 fold Chris! Congratulations on your purchase. My 66D still doing good service, in fact I have just bought a Horizon Tripod for some quick grab and go with either of the two WOs.

Hello,

I'm going to re-open this thread.

I've been testing my ZS66SD with SBIG STF8300M and the stars in the corners are very very elongated.

I don't if this is because large chip, flattener, weight of the ccd, miscollimation..... what is your opinion since i can see you have experience with this scope?

thank you!