Rowan Belt Mod - help!

[Carina Lass]

Can you show a screen shot?

I'm sure there's a simple reason for your problem that you've overlooked.

Agression maybe. When I had a sloppy system I dropped mine to about 45% at one point.

Whilst I agree perfect balance should be fine, in reality there's things that can interfere.

Slop in the belt, if you haven't got it tight it'll bounce. If it is misaligned it may grind against the shoulder of the wheel.

[Thalestris24]

Hi Carina

I'm still adjusting and currently waiting to test again. Adjusted the DEC and RA worms earlier. The RA worm adjustment is a right pain - very small adjustment between it binding or ok. So I need to test that when I can see some stars. I'm pretty sure both belts are tensioned and fitted ok. I've tried various PHD settings and guide speeds but have not been able to get better than the +/- 4 arcsecs zig-zag on the graph. Next time I can do some testing I'll do a log with guiding off. I have to be patient and keep trying. PE will still be present  but I'm not bothered about that. I don't think I have any flex - nothing obvious, anyway. I suppose it's a process of elimination! Watch this space!

Louise

[wuthton]

Another thought is it might be worth a play with the guiding rates in eqmod, I've got mine set to 0.2 DEC and 0.3 RA.

[Tinker1947]

What you need is a star to track on a wall in your room so you can run tests in day light with the curtains closed, i seem to remember there is such a thing, but never heard of anybody using one and no makers name comes to mind....

[Thalestris24]

Another thought is it might be worth a play with the guiding rates in eqmod, I've got mine set to 0.2 DEC and 0.3 RA.

Hi

I've tried that but it didn't seem to make any difference, unfortunately. Mine is usually set to 0.3 but I've tried other values.

Louise

[Thalestris24]

What you need is a star to track on a wall in your room so you can run tests in day light with the curtains closed, i seem to remember there is such a thing, but never heard of anybody using one and no makers name comes to mind....

I've often thought an artificial trackable star would be very useful! As it stands, it looks like I'll have to wait until Sunday evening. Sigh.

Louise

[Tinker1947]

Make one Audruino stuff is cheap £8 for a Hobby UNO board, £4 for a stepper motor and driver, Tecnobots do belt drive gears and pulley's it won't have to be super accurate close to 15 degree's per hour along a wall won't be to hard, and there's plenty of people on here to help out......

http://arduino.cc/en/Main/Products

[wuthton]

Make one Audruino stuff is cheap £8 for a Hobby UNO board, £4 for a stepper motor and driver, Tecnobots do belt drive gears and pulley's it won't have to be super accurate close to 15 degree's per hour along a wall won't be to hard, and there's plenty of people on here to help out......

http://arduino.cc/en/Main/Products

Polar alignment would be fun though and the guiding would look awful if it's not reasonably close.

[Thalestris24]

Hi

It would have to be as precise as an actual star otherwise it wouldn't be of any use. Not sure about focusing on something so close either. I'll just wait for the real ones to come out - I've plenty of other things to do!

Louise

[Thalestris24]

Hi all

I was able to do some more testing the other night. Still no change, still giving about +/- 4 arcsecs of error just as it did before the belt mod. So that would seem to point to something else being the root cause. The errors seem to be around the same in RA and DEC and random. I'm wondering whether it might be the atmosphere which is light-polluted, and water-laden more often than not. lensman57 (A.G.) made the comment in the weather thread that it was like imaging through a 1970's soft-focus filter the other night! Mind you, I used to quite like 1970's soft focus images!

Anyway here are some sample images, screen capture, and guide logs:

4 x 180s of M3:

PHD2 Screen:

Guide Log:

A random star, HIP89827, 4 x 600s:

Guide Log:

There might be some clear skies tonight and I'm going to try running the heq5 with battery power - just to eliminate any problems that could be caused by using a switching PSU. If it's still the same I'll look at having just the finder guider on the mount to see how guiding proceeds with effectively no load on the mount. After that, ( and probably on another night) I'll look at putting the 150pds on the AVX so different mount altogether!

I've noticed that Singlin has been having similar problems albeit with a 10" Quattro on a Mesu... So keeping an eye on his thread in the imaging section.

If anyone has any other thoughts or suggestions, that would be good.

Cheers

Louise

[1parsec]

Hi Louise.

The RA and DEC error graphs look very similar which is a good clue to what's happening.

If it were drive related I'd expect the DEC to be much flatter than RA.

Your guide camera has a pixel scale of  4.5arcsec/pixel at 170mm focal length which means you are relying on the guide algorithm calculating the guide star centroid to sub pixel accuracy and I believe the error is coming from there.  ( The guide errors on the graphs are only +-1 pixel)

It might be electrical noise from your PSU so a test using a battery will be worth while.

Another test would be to set up a longer focal length guide scope ( say 500mm +) or put the guider on the main scope itself.

Set the guider to longish exposures ( 5 sec or more ) to keep seeing effects to a minimum

Guiding at a much longer focal length will spread the guidestar over more pixels and reduce the effect of noise from the centroid calculation.

Dave.

[Thalestris24]

Hi Dave

Thanks for the suggestions Unfortunately the heq5 wouldn't switch on with the battery . It wasn't fully charged though the AVX came on with it ok - must be a surge thing. I might splash out on one of the Maplin bench supplies, just to be sure. I thought guiding 750mm with a finder would be ok but maybe not with the local conditions. I could maybe put the ST80 on. I think I'll try the 150pds on the AVX just to eliminate the Heq5. I've tried with DEC guiding one way but ended up with odd-shaped stars. Oh well, will keep trying!

Cheers

Louise

Edit: of course, if I change the graph from arc secs to pixels then it doesn't look so bad!

[Carina Lass]

Gotta say your M3 is a little strangled by the fuzzies.

You should be getting much clearer images than that.

This is M79 which is about half the size of M3.

Done on an unmodified neq6. with 8" meade OTA.

You should be able to get a better shot than that.

Your PHD graph is a bit jagged. I'm sure there's something in there that's loose - though I can't tell what as I'm much of a novice at remote fault finding.

Keep at it, you'll kick yourself (and me probably) when you find it.

Pop a bit of extra weight on one side and see what happens.

Why is the DEC so jagged? it should hardly move.

Try turning it off in the brain area and see how much the star trails.

[Thalestris24]

Gotta say your M3 is a little strangled by the fuzzies.

You should be getting much clearer images than that.

This is M79 which is about half the size of M3.

Done on an unmodified neq6. with 8" meade OTA.

You should be able to get a better shot than that.

Your PHD graph is a bit jagged. I'm sure there's something in there that's loose - though I can't tell what as I'm much of a novice at remote fault finding.

Keep at it, you'll kick yourself (and me probably) when you find it.

Pop a bit of extra weight on one side and see what happens.

Why is the DEC so jagged? it should hardly move.

Try turning it off in the brain area and see how much the star trails.

m79 12 mins.jpg

Hiya

I don't think there's anything loose! I'm encumbered by heavy city lp and a hazy atmosphere. This is very limiting, unfortunately. The M3 above is only 4 x 180s - I'd need a much longer integration time to get any kind of decent image (I did some 600s subs earlier ). Tonight I'm currently guiding with a 60mm guidescope that has a slightly longer fl than the finder guider (240 vs 170mm) but it doesn't seem to be any better.

As I said before, I'll try swapping the scope over to the AVX just to rule out the mount. I'm commissioning a 130pds as well. Maybe the shorter fl will give a better result especially if I guide with the ST90.

No worries - I'll keep battling with it!

Louise

[Tinker1947]

My PHD graph is at the moment quite flat with a spiky bit at regular intervals, if the graph does get a bit ragged i disconnect EQMod and use the handset to do  a 2 star alignment with a Polar alignment run this a couple of times using different stars but in the same part of the sky i like to point the scope at, it does bring the PHD Graph back to being flat or very close to it, reading other posts over a long period of time( years)  99% of errors seem to revolve around the PA being out mostly by just a little bit.....

[Thalestris24]

Hi Tinker

I don't do star alignments and don't have Synscan. I use Astrotortilla instead. I took some 120s subs unguided last night. I haven't look closely yet but they seemed ok at the time. I might post some of last night's results later - after I get back from the dentist... Anyway, lots of things still to try!

Thanks for your input

Louise

[Tinker1947]

I check my stars in DSS, hover the mouse over a star and it gets magnified in the top left corner pixel count the same top to bottom and side to side i assume means round stars.....good luck with the dentist how its a cheap visit......

[Thalestris24]

I check my stars in DSS, hover the mouse over a star and it gets magnified in the top left corner pixel count the same top to bottom and side to side i assume means round stars.....good luck with the dentist how its a cheap visit......

I threw an all-nighter last night so have a lot of stuff to go through... It's unusual to get a whole 'clear' night so tried to make the best of it!

Dentist is the second part of a root canal treatment - ££...

Cheers

Louise

[Tinker1947]

All the weather apps said last night would be clear, so 15:30 i open the obby up set-up the newt/neq6, put the dob on its base collimated both scopes invited a SGL Member with some new EP's round, its dark enough to align using Venus and Jupiter, all done have a cuppa tea, it dark now fine tune the alignment on couple of  Stars, start  imagine run on M65, it clouds over friend turns up with his EP's and we are dodging clouds comparing his to my Pentax's....wasted night really could have watched the football live instead of later in the evening......

[Thalestris24]

All the weather apps said last night would be clear, so 15:30 i open the obby up set-up the newt/neq6, put the dob on its base collimated both scopes invited a SGL Member with some new EP's round, its dark enough to align using Venus and Jupiter, all done have a cuppa tea, it dark now fine tune the alignment on couple of  Stars, start  imagine run on M65, it clouds over friend turns up with his EP's and we are dodging clouds comparing his to my Pentax's....wasted night really could have watched the football live instead of later in the evening......

I know that feeling of frustration - I get it all the time!

[Thalestris24]

I did some more testing last night... I set my 60mm guide scope up with a x2 Barlow thus doubling its focal length. However, it made potential guide stars look like balls of cotton wool! Not necessarily nice round ones either... It was quite hazy, I think (can't always tell what with the lp...). Calibration was iffy and S/N low even with a relatively bright star. I figured at the time (but see below) that my fl was now just twice what it was i.e. 480 rather than 240mm. That should have given me an guide scope image scale of 1.61"/pixel. The guide graph was still zig-zaggy, and erratic and still +/- 4" but worse sometimes. I observed bigger spikes when the star went out of focus / became distorted because of the atmosphere:

This gave me an image like this one (single 600s sub of some stars in Hercules):

I did minimal processing and there seems to be some field rotation . Next time I'll check the PA first...

It occurred to me later that adding the Barlow could have done more than simply just doubling the fl. Measuring it, the apparent fl was now 278mm rather than 240mm, giving 556mm overall. That meant the guide scope was imaging at 1.39"/px. I think that's way below what's actually possible to resolve here. I also think that the only way I'm likely to get sharper stars will be to image at a shorter focal length. I've yet to try out my 130pds so when I do, that will give me something to compare. I might also cross check the 150pds mounted on the AVX. Need more clear nights!

If all else fails I might have to consider abandoning the 150pds in favour of a frac...

Louise

[1parsec]

Hi Louise,

If you could see the shape of the guide star changing due to the atmosphere then you must increase the guider exposure to smooth that out or you will 'chase the seeing'.

Try 2x or 3x longer guide exposure you were using and see what difference it makes.

It's good that the stars in the main image are nice and round. and that's what matters.

Dave.

[Thalestris24]

Hi Louise,

If you could see the shape of the guide star changing due to the atmosphere then you must increase the guider exposure to smooth that out or you will 'chase the seeing'.

Try 2x or 3x longer guide exposure you were using and see what difference it makes.

It's good that the stars in the main image are nice and round. and that's what matters.

Dave.

Hi Dave

I did try exposing at 4 or even 5 secs but still got distortions and it was hard to find guide stars I could expose for that long. I think the above example was quite a large magnitude star. Trouble is, PHD2 auto adjusts the display so only shows the brightest stars which can be too bright for guiding on. This wasn't a problem before with the larger fov. Maybe next time I'll try turning the camera gain down. I still think I'm going to continue being atmosphere limited with the guiding. The heavy lp means I need an awful lot of data to create an image of any DSO - it's one thing on top of another Round stars maybe, but they're big and soft!!

Actually, not so round, either! But that might have been to do with the PA being out...

Cheers

Louise

[wuthton]

I use auto select star in tools, it quite often picks one that I can't see on the screen.

[1parsec]

Maybe the finder just isn't up to the task.  A test with the guide camera on the main scope would show this one way or the other.

Dave.