Guiding with Zenithstar 61 on Star Adventurer Pro

[MarkyB]

Hi All,

I have been able to buy my first scope, WO Z61ii (2020) to go on my Star Adventurer Pro (flattener on order), to couple to my Canon EOS (Baader modded 450D or unmodded 700D). My issue is that I can only get images as long as 40-45 seconds before star trailing appears. So I am looking for a guiding solution at the cheaper end of the scale due to budget constraints (sub £100 if possible). I know the solution won't be as great as a larger budget but I'd like to get some thoughts advice on what is possible. I could only just get the scope approved by the "in-house bank manager" so a mount upgrade is out of the question for now, but definitely on the cards.

Can I use a OAG? What OAG? Other budget constrained solutions?

This would also need to be weight conscious as I think I only have about 500g additional weight to play with.

I don't mind if the solution is a little Heath Robinson.

Thanks,

Mark

[rl]

I doubt if an Off-Axis-Guider is the solution; you will need an extra guide camera plus a PC to control it. And there will be spacing issues to worry about. The dedicated ZS61 flattener comes with the correct spacing as standard which tends to rule out an OAG unless it goes in front; this just changes one spacing issue for possibly an in-focus travel issue.

Is the real problem poor polar alignment or gear cutting errors? Having owned this rig myself I'd strongly suspect the former, especially at the rather short focal length in use. The flattener will reduce the focal length by 25% which makes trailing a bit better cosmetically. 

Are you using the polarscope for PA alignment?

The balance needs to be slightly heavy on one side just to take out any backlash in the gears.

Are you using a PC to work the camera or just using it native? I'd look at using the camera and main scope to set polar alignment with one of the plate-solving methods...some camera control programs come with this feature as standard. It's very effective. Sharp Cap Pro? It would keep both weight and budget down.

I found I could go for about 2 mins with most of the subs useable just by moderately careful alignment on the polarscope.

[TerryMcK]

Yes I agree it sounds like polar alignment is awry as that mount should be capable of decent-ish non trailed subs for longer than 45 seconds.

[TerryMcK]

One of the little 30mm ZWO guide scopes with a ZWO ASI120MM camera connected to the mount with an ST4 cable will work. Use PHD2 from a laptop and it should guide well. However that might exceed your budget.

 

EDIT - that combo is 560g

Edited August 13, 2020 by TerryMcK

[MarkyB]

Okay, that's something to think about. I do use a laptop for the imaging, Backyard EOS. Polar alignment is through the polar scope and, according to the reticule, I'm getting good at it, especially since I swapped my camera tripod for the proper Skywatcher one. I do check the alignment a few times during an hours session and Polaris is normally sitting nicely on the correct circle now. Although I will check the polar scope is not off slightly.

The mount was second hand and I have recently smoothed the the clutch plate as I had a sticky point when rotating (plus a couple of small debris dings to the surface).

I'll certainly check out the Sharp Cap Pro and learn about plate solving as this is not a process that I have used/needed to learn about so far.

I've been interested in astrophotography (static camera shots) for a few years now but only had a tracking mount since Christmas, so still very new to me.

[MarkyB]

I have just quickly checked the polar scope alignment (using a distant TV aerial) and it is a slightly off. Plus the wedge could also do with some attention/mod to tighten things up. I guess that's what the Summer months are for?