Seeing and high magnification turbulence

[kkara4]

Just trying to eliminate the possibility that my motors on my G11 are vibrating more than they should be:

We have very poor seeing at the moment, and when observing Saturn or Mars at about 450x, I find in addition to turbulence causing detail to be blurred randomly as areas of turbulence drift past, the planet seems to jump around slightly as well.

Is this normal to expect under poor seeing conditions, due to changes in refraction and the high magnfication?

It is barely noticeable at approx 120x.

Might try strapping the motors into the gearbox housings with some cable ties as well...

[rrussell1962]

Hi kkara4, I think x450 is pushing it a bit if you have the Celestron 9.25 as I recall. My experience with the Nexstar 8 is that anything over x30 per inch is pushing it except on very good nights, so say x300 max most nights for your OTA. Even with my Obsession 18" I am finding anything over x250 not much use at the moment. Happy to lend you different eyepieces to try out - my vixen LVW 8mm would be a nice high mag eyepiece for the 9.25. Also have a Celestron F6.3 focal reducer if you want to see how that goes. You are right about the seeing though! Can we catch up sometime - I have been experimenting with astrophotography (inspired by you!) and could do with talking to somebody who actually understands cameras and how the whole thing works. I will PM you when I get a chance.

Best wishes

Richard

[rrussell1962]

Not sure about the jumping around though. Backlash usually shows up with pointing problems in my limited experience. Could it be a gear slightly binding?

Richard

[AstralTraveller]

I don't know about the motors by direct experience. Have you tried turning off the tracking? Of course it will drift very fast but you might be able to decide whether the 'jumping' is still there. I also think 450x is pushing it too much optically.

[kkara4]

Good to hear from you again Richard!

Certainly is pushing it, but i find myself not caring when I look at Saturn about half the size of the full moon :lol::eyepop:.

You should definitely come over, perhaps next week, i will have the scope out next few nights but have a horde of people wanting to look through it already :lol:. I had to beat them back so that I have an hour of imaging time before bed!

no worries will await your PM :)

[kkara4]

What it could be is a combination of the greater weight now that I have the extra dovetail for guidescope, in combination with a 12v supply as opposed to 15v. 15v 90w meanwell power supply on its way and will arrive tomorrow, in combination with lazy eyeball balancing of the scope.

I will give a few things a whirl and try the turning off of tracking suggestion and see what happens!

as an experiment, I did try the camera in there at 200x ish equivalent, and on 5x crop there was still a bit of jumping around (again during very poor seeing).

[rrussell1962]

I recall, and I may be wrong, but do you have the Losmandy G11? If so I don't think weight will be an issue with a 9.25 tube. Aren't the Losmandy's rated somewhere near 25kg? Even for imaging, say 15kg. Might be a power supply issue though since you mentioned 12v. You could try a cheap jump starter from Supercheap, charge it to the max so it delivers around 14v for a short time and see how that works. I have one here that I use for the Nexstar 8SE with no problems. If you want to give that a go let me know and I will bung it on charge for a few hours and you can pick it up.

Richard

[kkara4]

thanks Richard, all good RE power supply, will arrive tomorrow anyway! Yep have the G11 and 9.25 OTA + losmandy dovetail + cge dovetail + orion ST80 + powermate + televue diagonal + nagler 22mm eyepiece. I agree weight is below 25kg pretty sure, way below.

psu definitely suspect, will see how she goes tomorrow with the 15v on there, because i dont recall a jumping issue with 16v when i did a small test a while back.

Also my power was a bit off, actually works out to 427x. Saturn did seem a touch blurry and harder to focus than when I used the 23mm axiom and 4x powermate to yield 408x, but that could well have been seeing, because I know for sure I had zero problems with sharpness when good bits of seeing appeared, could make out casini division and some cloud bands very clearly, and then returned to a blurry mess lol.

a bit like a lamborghini driving past, where you wish it parked right in front of you instead of zooming past and you only get a second to admire it :P.

Theoretical limit for 9.25 OTA is 9.25x50 = 462x, but of course seeing has to allow for that, I can understand that.

What I dont understand tho is why people say 450 is too much regardless, because i find myself :eyepop: when looking at saturn as compared to the nevertheless still beautiful view looking straight through the nagler 22mm!