The ULTIMATELY adjustable guide scope

[ZeroID (Brent)]

As anyone who lives in large city knows LP is an issue. It becomes serious when you attempt to find a star to guide on and there is absolutely NOTHING near your target that the guide scope and camera can see. Therefore you need to be more flexible with guiding arrangements. I present to you all the ULTIMATE guide scope mount, an 80mm f5 on an AZ3 head. I should be able to guide off ANY star within a 90* angle from the target.
(Actually the mount head is quite light, hollow casting and the EQ6 is still well under loaded but at least I should be able to find something to guide on, somewhere. I hope ! )

[mental4astro (Alexander)]

Very creative Brent, Something along these lines I had a fleeting thought of as plausible at the last IIS when seeing the imaging fellows. But not being into photo, I never gave it much more thought than a fleeting one. Never mentioned it to anyone in case I was called a heretic for being a visual boy attempting to make a suggestion to the imaging ones... I'm glad though you've pulled it together, But to make use of an AZ3 head is a really good one, Excellent stuff,

[ZeroID (Brent)]

Thanks Alex, unfortunately even DIY seems to come packed with clouds so it remains untested so far. Tonight is looking promising, so far, fingers crossed.

[ZeroID (Brent)]

After managing to pick up my 'el cheapo' 450D last night I managed to give this a whirl. Not perfect but I can at least find stars to guide on with the SPC 900, they have to be visually discernible and as they get dimmer the camera has issues differentiating. I may try the C80A filter to see if it kills some BG LP. Got guiding working nicely with PHD2, Metaguide kept posting some sort of guiding error for which I couldn't find an explanation or solution. I suspect the SPC 900 may not be totally the best hardware for it. Once the Canon 450D is going I may switch the AS! 120 over to guiding for some situations.

And solved another PC problem with Stellarium constantly crashing. Downloaded the off line install for the latest DirectX update and installed it. No funny 'delta' stars and no crashing. Might be able to get it talking to the mount finally.

On my other Peltier project I had it down to -10* in an ambient of 14. Enough to be useful. Shame the 2/3 moon was filling the sky with photons but tried some Lunar imaging.

At least there were no clouds

[5ash (Philip)]

Hi Brent ,
How far off axis can you go to maintain accurate guiding of your subject without 100% accurate polar alignment , I wonder? Looks like a cheap alternative to SW & vixen al/az guid mounts.
Regards philip

[Geoff45 (Geoff)]

Originally Posted by 5ash

Hi Brent ,
How far off axis can you go to maintain accurate guiding of your subject without 100% accurate polar alignment , I wonder? Looks like a cheap alternative to SW & vixen al/az guid mounts.
Regards philip

You get field rotation about the guide star. How much (aka is it important) depends on the length of your subexposures, the accuracy of the polar alignment and the position in the sky of your image, so there is no quick answer.
Geoff

[ZeroID (Brent)]

Originally Posted by 5ash

Hi Brent ,
How far off axis can you go to maintain accurate guiding of your subject without 100% accurate polar alignment , I wonder? Looks like a cheap alternative to SW & vixen al/az guid mounts.
Regards philip

Don't know yet, only had one night of trials so far. My SCP alignment is pretty darn good, I'm can take 2-3 min exposures with no apparent movement and can see no drift even after 20-30 mins. (Although exposures are limited by LP to about 30 secs without filters).

Practically speaking the physical limtations of other hardware mounted etc limit it to 15* of depression and about 35* of elevation with maybe 90* Right AZ and 30 Left AZ movement.
In reality I'd be choosing guide stars in close proximity to the target but at least it gives me lots more options.

Biggest bugbear so far is in pointing west the controls are far away from my screen viewing position and there is some backlash in the wands and worms but it's not like it's critical positioning so the range and stability is excellent.

About to add a 450D and BYE into the mixture and get close to imaging automation almost.