Sadr

[SkyHiker]

A full Moon target just to see how the guiding is working out. 42x60 s with recycled flats and biases. About 1" total RMS guiding. Edited in DSS.

[Graeme1858]

Looks like the guiding experiment was successful!

Nice colours and a hint of nebulosity too.

Regards

Graeme

[BABOafrica]

Yeah, seems like the guiding is pretty good.

BABO

[messier 111]

very nice , thx .

[yobbo89]

very nice, what is the run down on your current gear, i remember you got the new 10'' scope and you had some tracking problems on your mount ? what have you done to improve the results ?

[SkyHiker]

very nice, what is the run down on your current gear, i remember you got the new 10'' scope and you had some tracking problems on your mount ? what have you done to improve the results ?

Hi Rob, and thanks.

It's a 12" not a 10" GSO Newt astrograph that weighs 48 lbs (steel tube). I use it with a Paracorr II CC, autofocuser and QHY medium OAG with a ZWO ASI120MM mini. The CC raises the focal length from 1200 to 1380 mm. The mount is a modified G11S with an OnStep controller with TMC2130 drivers and 17HM15-0904S steppers (0.9 degrees). The high level control is done by Ekos on a Raspberry Pi 4B, an integrated package with planetarium control, plate solving, autoguiding, you name it. I added DIY spring loaded worms to the G11S to keep it from binding up during slewing. Plenty of DIY components to worry about but it's fun to build.

The mount works great for slewing but I can't get the RMS below 1". Last week I tried counterbalancing in RA, which cut the RA RMS in less than half but 1" total RMS is what I've been getting on most nights. I have been experimenting with several settings: PHD2 instead of Ekos, disabling the SLW by tightening the bottom screws, counterbalancing, different guide rates, control parameters and guiding exposure times, multi and single star guiding. None of this got me down to where I need to be. I am at 0.56" per pixel. At 1" RMS a point source becomes 2/0.56=3.6 pixels so no point in trying my ASI2600MM, pixel resolution wise. The Dawes limit is 0.39".

I have to say that the seeing may have been a problem with the heat wave of the last couple of weeks. But I still think there should have been nights where the guiding is better than what I get if everything works as expected. So maybe it does not. I am currently suspecting that the $12 steppers that I use with 64x microstepping are not up to the job. Microstepping is great, it avoids gear boxes but the torque also plummets with the increasing microstep multiplier. So maybe that's why I get the noise that I do. The guiding is simply all over the place. If I had to guess I need to get stronger steppers or the some that have built in encoders. I just would like to stay at 12V that I can supply simultaneously to OnStep.

It would be nice to have a setup where I can run the steppers during the daytime without load to see what the problem is. I've been thinking about building some rig with a laser that I can mount on the saddle that runs in the opposite direction then analyze the RMS in the daytime. The easy way out would be to get an AP mount, which I am seriously considering. I also need to get PI because I know it has tools to minimize the stars. But I would like to have better stars to begin with.

I'm following the discussions on the Losmandy board about SLW and RA and DEC axis needle bearings, and just started a thread on the OnStep board asking about the accuracy. The G11 can work great with proper settings, it is unknown how well OnStep compares with the Gemini controller. There are several success stories but no solid statistics. My goal is to solve it or get a different mount.

Here's another image I took last night, this time Deneb. I used a gain of 140 on my ASI2600MC, the one for Sadr was 210, about 40x60s.

[Ylem]

Looking good!!!

[yobbo89]

cheers for the info henk, a good read on your mount analyst, it would be handy if you had a second mount or knew someone near by to get some seeing/tracking info , both my mounts,one being slightly superior then the other ,on a bad night they both will track very poor with very close rms error to eachother, so it is easy to rule out hardware issues against the sky ..

you've tried adjusting the spring worm tention?, also agree that a stepper motor with a built in encorder would be better as even a stepper motor can give a bit of periodic error and the more load on the motor,the worse it is ..

[SkyHiker]

cheers for the info henk, a good read on your mount analyst, it would be handy if you had a second mount or knew someone near by to get some seeing/tracking info , both my mounts,one being slightly superior then the other ,on a bad night they both will track very poor with very close rms error to eachother, so it is easy to rule out hardware issues against the sky ..

Interesting idea. I have an AVX, heck I could compare them but there is the hassle of setting up both systems. About that daytime laser analysis, I could use the AVX with a mirror turning in the opposite direction.

you've tried adjusting the spring worm tention?

Yes

, also agree that a stepper motor with a built in encorder would be better as even a stepper motor can give a bit of periodic error and the more load on the motor,the worse it is ..

Actually it turns out its resolution is not good enough so it doesn't help much. OnStep users wrote a lot about this.

[ic_1101]

Nice capture!