How to steer a guidscope.

[SteveBz]

I finally got my guidescope running last night (cheap refractor, large guidescope rings and webcam).  Not perfectly, but definitely taking images and making navigation corrections.

My big question now is how to steer the guidescope from my laptop when the guide star is outside the field of view. Does anyone have servo motors on the guide-ring screws?  Or do I use a dove-tail plate with some sort of steering servo there instead?  Either way I'd need two or three motors and on the guidescope rings they would need to move in synchronisation, two or even three at a time.

Ideas please.

Steve.

[Guest Tuomo]

You really do not steer your guide scope. Never. You can try to align it to same target with you main scope using bright star. I center my imaging ota to bright star using DSLR live view and then adjust guide scope springs to center guide cam with laptop. Generally speaking your guide scope and imaging scope needs to be in the same area, not exactly at the same point.......

Its VERY much different matter if your guide cam is not sensitive enough for good guiding/spotting dim stars. Instead of thinking motors and stuff you should buy decent guide cam and solve your problems with one easy way.

[SteveBz]

1 hour ago, Tuomo said:

You really do not steer your guide scope. Never. You can try to align it to same target with you main scope using bright star. I center my imaging ota to bright star using DSLR live view and then adjust guide scope springs to center guide cam with laptop. Generally speaking your guide scope and imaging scope needs to be in the same area, not exactly at the same point.......

Its VERY much different matter if your guide cam is not sensitive enough for good guiding/spotting dim stars. Instead of thinking motors and stuff you should buy decent guide cam and solve your problems with one easy way.

OK.  Well that's probably where I am. Cheap cam.

So I'll make do for the time being and then upgrade the family when I get a chance.

Tx

Steve

[SteveBz]

2 hours ago, Tuomo said:

You really do not steer your guide scope. Never. You can try to align it to same target with you main scope using bright star. I center my imaging ota to bright star using DSLR live view and then adjust guide scope springs to center guide cam with laptop. Generally speaking your guide scope and imaging scope needs to be in the same area, not exactly at the same point.......

Its VERY much different matter if your guide cam is not sensitive enough for good guiding/spotting dim stars. Instead of thinking motors and stuff you should buy decent guide cam and solve your problems with one easy way.

Actually, now I think about it, I have a modded Philips cam.  It has larger pixels, but it's more sensitive than my current cam, so it might be an improvement, although a little heavy.

Steve

[Guest Tuomo]

50 minutes ago, SteveBz said:

Actually, now I think about it, I have a modded Philips cam.  It has larger pixels, but it's more sensitive than my current cam, so it might be an improvement, although a little heavy.

Steve

I can relate to you. I once tried to guide with Microsoft lifecam Studio. I could find brightest stars with it, but everytime I used it there was this "what if I cant find any guide stars.". Do like I did and save/throw some money for decent guide cam. QHY5-family is good enough. Your imagin nights will be MUCH easier. I promise you that. BTW what is the focal lenght of that guide scope? Seems like quite long? I mean, longer the FL, more sensitive your cam must be...or something like that. Think there is something between light gathering ability and FL.

[SteveBz]

1 minute ago, Tuomo said:

BTW what is the focal lenght of that guide scope? Seems like quite long? I mean, longer the FL, more sensitive your cam must be...or something like that. Think there is something between light gathering ability and FL.

It's about 300 mm.  The blurb says 250 mm but when you measure it it's longer.  That's a good point, though and I didn't think about it.  It's a 50 mm scope with about 300 fl, so f/6.  Should be "fast" enough.

So why do I have guide rings at all?  I really don't need them. Well maybe I do now, but with a better cam I shouldn't.

[Guest Tuomo]

Guide rings are nice, if you would use guide scope visually. Rule of a thumb: less moving parts the better. Any unwanted movement in guiding reflects to bad guiding.

[brantuk]

Here's a possible solution for manually acquiring a guide star. Though it's a tad expensive - Skywatcher do a cheaper one for just over £100:

https://www.firstlightoptics.com/adm-guider-mounting.html

http://www.rothervalleyoptics.co.uk/skywatcher-guidescope-mount.html

Worth bearing in mind that a guide scope benefits from having a wide fov. Hth

[SteveBz]

4 minutes ago, brantuk said:

Here's a possible solution for manually acquiring a guide star. Though it's a tad expensive - Skywatcher do a cheaper one for just over £100:

https://www.firstlightoptics.com/adm-guider-mounting.html

http://www.rothervalleyoptics.co.uk/skywatcher-guidescope-mount.html

Worth bearing in mind that a guide scope benefits from having a wide fov. Hth

Hi BrantUK,

Nice to hear from you.  What did you think of Tuomo's point that it's just better to have a more sensitive camera.  It strikes me that if we are going to have these lovely adjustable things, we have to be able to adjust them remotely. 

I saw AstroShed's video on them, and he loves them.  So really, I'm very open to the idea, but I really want a hands-off solution.

What do you think?

Steve.

[DaveS]

I really wouldn't use rings, just another point of flexure.

When I was guiding I used a Skywatcher ST80 (80mm f/5) and a QHY5-II on a dovetail bar. PHD2 never had any problems finding a guide star. As Olly has said, guide rings date from when cameras were very insensitive and had to be adjusted to find a star, or even beyond that when guiding was done by eye and cross-hairs (Thankfully before my time).

Now, of course I use a DDM60 mount which guides on its encoders and a sky model. Bliss!

[SteveBz]

2 minutes ago, DaveS said:

I really wouldn't use rings, just another point of flexure.

When I was guiding I used a Skywatcher ST80 (80mm f/5) and a QHY5-II on a dovetail bar. PHD2 never had any problems finding a guide star. As Olly has said, guide rings date from when cameras were very insensitive and had to be adjusted to find a star, or even beyond that when guiding was done by eye and cross-hairs (Thankfully before my time).

Now, of course I use a DDM60 mount which guides on its encoders and a sky model. Bliss!

Dave, what a very fine mount, but costs more than my last two cars combined.

So what you are saying, like Tuomo above, is buy a better camera and ditch the rings.

I have to say, if the "Better cam" model is right, then the ring model must be wrong.  Maybe I'll just mount the rings on top of of the guidescope as a decoration!

Is QHY5-II the standard for sensitivity/guiding?

Tx

Steve

[DaveS]

The QHY was a fairly cheap camera when I bought it, it was all I could afford at the time but it isn't very sensitive, probably about aveage. I think most people use one of the SX cameras, the Loadstar is pretty much favourite.

[SteveBz]

10 minutes ago, DaveS said:

The QHY was a fairly cheap camera when I bought it, it was all I could afford at the time but it isn't very sensitive, probably about aveage. I think most people use one of the SX cameras, the Loadstar is pretty much favourite.

Dave, as you can see from the photo, my cam is a little metal electronic eyepiece (it cost £22 on ebay).  But it's not very sensitive.  I could quite easily ramp up the gain and amend the software to subtract darks and biases.

Maybe this would make it more sensitive.  It's something I should try before troubling my bank manager any more: he gets quite stressed by the cost of Astro gear, and he'd have kittens if I told him I liked your DDM60

[brantuk]

Hi Steve - yep a more sensitive camera is always a good idea - helps a lot - mine is one of the original Lodestars. And like Olly I strap my guide scope (ST80) down to the dovetail or sbs bar with no adjustable parts - finding a guide star is rarely a problem.

I've tried guide rings and adjustable saddles and they are nearly always a flaff - but the new one from FLO looks a lot more solid which is the only reason I suggested it as an alternative. But I agree if it could be driven remotely it would be a nice touch. Ultimately a sensitive camera, a solid mounting, and a wide fov gives the least number of problems for us amateurs. Now observatory class gear - that might be a different matter entirely lol.