Jump to content

Banner.jpg.b89429c566825f6ab32bcafbada449c9.jpg

EQ6 belt drive modification


George

Recommended Posts

George,

The 12 pully that needs boring out to 5mm, when you drill it basically it removes all of the center section leaving just the main pully. My machinist was querying it but i told him just to bore it out any way.

I take it yours is fine like that?

Depending on how accurate his lathe is you should be left with 0.5 - 1mm of the insert which is steel I think.

As long as there's no runout when its on the stepper shaft you should be OK.....mine has the slightest of slight wobble :) Im on the lookout for a solid steel replacement which will be a doddle to bore.

First indications of my own conversion are looking very good, my PHD graphs were looking excellent compared to what I was getting but I didn't get enough data to run thru Pecprep.

I also spent a couple of hours on Sunday lapping the RA worm and wheel, I can turn the RA worm with 2 fingertips with the mount fully loaded......never been able todo that before :)

Link to comment
Share on other sites

I will see today if i have any insert left then. I have a feeling it may get completely bored out.

Lapping? Ha! I'm too lazy for that, i remember doing it at school 20 odd years ago but i don't have the stuff to do it.

When I took apart the RA i noticed i had bent the dust cover on one if the ra worm bearings, i suspect this may have been causing high freq noise. I would recommend anyone doing a strip down to get a replacement set of these bearings just in case ( they are cheap enough)

Link to comment
Share on other sites

When I took apart the RA i noticed i had bent the dust cover on one if the ra worm bearings, i suspect this may have been causing high freq noise. I would recommend anyone doing a strip down to get a replacement set of these bearings just in case ( they are cheap enough)

Its also worth noting that you don't actually need to strip the mount down to change the worm bearings - you can work them out for the outside so to speak :-)

Chris.

Link to comment
Share on other sites

Its up to you - you can either stick with the same ratio (if you can source the 47 toothed gear) or you can go for a 5:1 ratio

For a 5:1 ratio on an HEQ5 you would need to set EQMOD up with the following parameters:

Total Steps = 8640000

Worm Steps = 64000

Tracking offset = -28

For a 4:1 ratio on an HEQ5 you would need to set EQMOD up with:

Total Steps = 6912000

Worm Steps = 51200

Tracking offset = -211

However with the 4:1 ratio you would be operating a long way away from the original values the mount is designed around and you may find that the max slews at a much faster top rate (this isn't controlled by EQMOD - the mount makes its own mind up how fast to go when slewing to a target and of course it doens't know you've changed the gearing!)

[Edit] Just for completeness I'll give the HEQ5 6:1 values

Total Steps = 10368000

Worm Steps = 76800

Tracking offset = 80

Chris.

Chris, I've opted for the 5:1 ratio... but a tad confused

In Georges post above the two values for RA and DEC are different

eqmod.jpg

Is this the same on the HEQ5 or are both RA and DEC ratios 705:1 ?

Link to comment
Share on other sites

Well someone is conspiring to deny me getting data on the belt conversion, my PC decided my QHY5 guide camera didn't exist anymore and no amount of plugging/unplugging made the guider detectable :p . I ended up having to reflash the EPROM on the QHY5 to get it working again and yes it had clouded over in the meantime :(

No data tonight then :)

Edited by George
Link to comment
Share on other sites

Fantastic George! Can't wait to get mine back together and give it a go.

Yes get your finger out :)

Did a quick run of the PHD data thru Pecprep, full report in the morning.

Worm Period: 479 Secs

Steps/Period: 50133

Sample Count: 1742

Sample Int.: 0.99 Secs

Trend: Y = 0.0000X + -0.2

Peak PE+: 1.51 arcsecs

Peak PE-: -1.24 arcsecs

RMS PE: 0.42 arcsecs

MaxRate: 0.52 arcsec/S

MaxRate: 0.03 x sidereal

Av. PE+: 0.37 arcsecs

Av. PE-: -0.32 arcsecs

Max Delta+: 1.10 arcsecs

Max Delta-: -0.52 arcsecs

Av. Noise: 0.00 arcsecs

Link to comment
Share on other sites

Also looking at the above graph have you tried guiding the dec in only one direction? Made a hell of a difference on my system as eliminates over correction.

Someone mentioned it on SGL and i tried it last week and it worked well.

Link to comment
Share on other sites

I only had a small cloud free window tonight and I desperately wanted to grab some quick and dirty data, Ideally you should grab PHD data with guiding turned off but I wanted to compare old data with new data and as I had no unguided data I had to do a guided comparison, not ideal but.......

Also looking at the above graph have you tried guiding the dec in only one direction? Made a hell of a difference on my system as eliminates over correction.

Someone mentioned it on SGL and i tried it last week and it worked well.

Link to comment
Share on other sites

Ok here's the data I grabbed last night and below it the last data of a short session in August.

post-13224-133877682224_thumb.jpg

post-13224-133877682231_thumb.jpg

Im hoping Chris will pop in here and decipher it seeing as he wrote PECprep :(

To my untrained eye I'd say most of the errors I had are reduced by 50%, considering what the modification cost and the time involved I'd say it was more than worth doing.

If I could figure a way of including the logs in this post someone might be able to decipher them better :)

Edited by George
Link to comment
Share on other sites

I've just downloaded Chris's PEC application and dumped the PHD logs from previous guiding sessions (not had a chance to test since I re-meshed the gears). Not having a clue if this is right but this is what the application gives me... I assume by having small bumps in the graphs the mount is within tolerances ??

post-23388-133877682238_thumb.jpg

Link to comment
Share on other sites

Im hoping Chris will pop in here and decipher it seeing as he wrote PECprep :(

To my untrained eye I'd say most of the errors I had are reduced by 50%, considering what the modification cost and the time involved I'd say it was more than worth doing.

If I could figure a way of including the logs in this post someone might be able to decipher them better :)

Hi George,

I hope you'll understand that it is rather difficult to comment on the mounts performance by looking a guided data. All we can really comment on is the guiding performance which isn't necessarily the same thing at all. Also given the numerous variables in play that can affect guiding (including target location) this ends to make comparative analysis difficult.

For guiding performance we're obviously looking for a flat line response in the time domain. The flattter the trace the better so lower Peak values and lower RMS values indicate better guiding. For the frequency domain were really looking for a spectrum where all frequencies are present with equal magnitudes - i.e. no distinct peaks. If there are significant peaks and they coincide with the harmonics of know mechanical components guiding itself hasn't been as effective as one might have hoped. That said it could be that amplitude of the signals present falls within some guiding threshold. To invstigate thee apects you really need to go the the frequency spectrum tab and use the tools there to calculate the Peak to Peak amplitude in arcsecs being contributed by each identifiable component.

So..... looking at the images you have posted it would appear that the latest data shows a better response in the time domain - i.e. reduction in RMS and peak values. The frequency domain would appear to show so prominent peaks associated with the worm and its 2nd harmonic which indicates there is actually scope for better guiding performance.

When you get the opertunity try an capture 4 or 5 cycles of unguided data (the more data the better) you can do this in poor seeing conditions at twilight - just pic a bright star. We can filter out high frequency seeing fluctuations later in PECPrep. If you have a web cam use that and set the PHD exposure rate as fast as you can - the more data PECPrep has the better will be its analysis. With that data we should be able to get a real feel for the mechanical performance.

Oh and one more thing I should mention for the benefit of anyone new to loading PHD logs into PECPrep. Please make sure you enter the guide star declination, pixel size, focal length etc. correctly. If you don't then the amplitudes shown in PECPrep will be incorrectly scaled.

Chris.

Link to comment
Share on other sites

I've just downloaded Chris's PEC application and dumped the PHD logs from previous guiding sessions (not had a chance to test since I re-meshed the gears). Not having a clue if this is right but this is what the application gives me... I assume by having small bumps in the graphs the mount is within tolerances ??

Hi Malcolm,

What that is showing is that you have a significant periodicity in your guide data associated with your mount gear mesh period at around 13.6 seconds. Use to the tools on the frequency spectrum tab to confirm this. Now you've remeshed things I bet you've improved this somewhat.

As I said to George, to do mechanical analysis you 'll need to capture at least 5 cycles of unguided data (I realise this is 50 mins with an EQ5Pro!) - preferably at the highest rate you can.

Chris.

Edited by chrisshillito
Link to comment
Share on other sites

Chris, I'm going to ask a numpy question here. How to you obtain unguided data from PHD, and if it's unguided, does that mean I could simply let the mount run for an hour in the day time to get the data needed ?

Link to comment
Share on other sites

Chris, I'm going to ask a numpy question here. How to you obtain unguided data from PHD, and if it's unguided, does that mean I could simply let the mount run for an hour in the day time to get the data needed ?

Unguided means PHD will track and log the apparent movement of the guide star but it does not issue any guide corrections to the mount (the mount should of course be be tracking at sidereal). In PHD you will find a disable Guiding output check box. Uncheck this then start "guiding" and the star will wander around on screen as determined by the mounts periodic error and polar alignment error drifts.

It is important the you calibrate as normal so that PHD can measure the "camera angle" with respect to the RA/DEC axis - which PECPrep then reads from the log when making its calculations. Also becuse you need to keep the star in frame for around 50 minutes you probably want to get a decent polar alignment and/or choose an appropriate image scale (go to high and the star may wander out of frame).

You can't record the PE during the day as we need a star to follow - you can do it at dusk though when there isn't much else to see. PECPrep will filter out the effects of poor seeing, wind disturbances ad the like so you really don't need perfect conditions.

As an alternative to using PHD to record your PE you might ocnsider using perecorder (if you have a webcam) . With perecorder you don't need to make a note of the stars declination or enter pixels sizes and the like when importing the data into PECPrep as perecorder logs already ave their data in terms of arcsec movements in RA/DEC. Things are also a little easier if you want to create PEC curves (but that's another story).

Chris

Link to comment
Share on other sites

Thanks for the input Chris. I use a QHY5 with an ST80 for guiding, is the QHY5 supported by perecorder or is it just webcam only

Yes, perecorder is just webcam. Not a problem though PHD works fine for PE recording provide you tell PECPrep all appropriate details on log import. Note that you can use your main scope for this process to get higher resolution data. So longs as the star stays in frame over the capture period.

Chris.

Link to comment
Share on other sites

Chris, I've been running now for 40min through the ST80.... If I get chance I'll also try it with a webcam in the 200P for an hour and then post up the results later. I would apreciate your input which hopefully will confirm how well or poorly aligned my scope is, and how much PEC I now have after the re-build of the drive train

Link to comment
Share on other sites

Sorry to somewhat hijack George's thread, but it is kinda related :)

I've just spent this evening gathering data as follows:

1Hrs running PHD with the QHY5 connected to the ST80

1Hrs running PHD with an SPC900 through the 200P.

Target star was Altair

I've attached the log files which I would love to have analyzed (Chris if you have time I would welcome your comments). However, looking at the attached screen shot it's obvious that I have quite a few problems, unless I've some how entered the incorrect information when importing the file ?

post-23388-133877682779_thumb.jpg

ST80.txt

200p.txt

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.