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HEQ5 Pulley Mod - PE Comparison


russellhq
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I bought a HEQ5 pulley kit from Earl on this forum a while ago and finally got a chance to try out the upgrade under the stars. The kit was originally bought from Belting Online;

http://www.beltingon...drive-kit-12097

Had a couple issues with the kit, first off the belts weren't included but Earl was very good and had a word with Belting and the new ones were on their way quite quickly. Also, one of the threaded holes for the grub screws (on the small pulley) wasn't threaded all the way through so couldn't get the grub screw to grip the shaft. As I felt 1 screw wasn't enough, I decided just to fix this myself (actually my dad did the fix!) and add a couple more holes.

The upgrade was pretty straight forward following Malc-c's guide, my only problem was the new position of the stepper mount was causing it to foul on the dec shaft. A quick file soon fixed that.

Well, onto the results. I first captured 5 cycles of PE prior to the mod and below is a screenshot from PECPrep with the auto filter applied:

PECPrep_Pre_mod.png

Next, i repeated the same with the pulley mod and here's the screenshot from PECPrep:

PECPrep_Post_mod.png

Now, I don't know what this all means but it does look like the pulleys have reduced the overall PE and also the rate of change of PE as well, which should make guiding easier.

Maybe someone more knowledgeable can cast an eye over the results and pass comment (Chris ;) )

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I'm no expert but looking at the data bottom left the RMS PE etc has been reduced a fair bit, sometimes as much as half. But the traces seem a lot smoother and regular too which should make for better correction. I'm sure Chris will jump in here soon

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I wasn't sure whether you should compare before or after applying the filtering. Not sure if it makes any difference?

The traces are a lot smoother, and looking at the frequency you can see the signal from the gear mesh period has obviously dissapeared:

Before:

PECPrep_Pre_mod_freq.png

After:

PECPrep_Post_mod_freq.png

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Hi

I just tried to auto guide my SW N200/1000 with a 9x50 barlowed finder on my just finished belt modded HEQ5. I'm using PHD Guiding. It was impressive. The RMS was 0.12 and the oscillation index in the magnitude of 0.30 ! The curves were almost flat.

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Well, I've just loaded up a log file from a guiding session in April this year, and this is the results based on the ST80 and QHY5

If I read this correct the RMS readings are quite good.... other than that I wouldn't have a clue how well the guiding was....

Interestingly it seems to suggest that the PA is out by several arc minutes....maybe I need to do some fine tuning of the mount

post-10726-0-11404800-1373124509_thumb.p

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The focal length for your st80 looks quite long, I thought it was 400mm? Also, I usually set the graph to show arcsec /min of the imager as I find it a more meaningful number. Did you also enter the declination of your target? I sometimes forget to update the Dec when I load a new log.

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The focal length for your st80 looks quite long, I thought it was 400mm? Also, I usually set the graph to show arcsec /min of the imager as I find it a more meaningful number. Did you also enter the declination of your target? I sometimes forget to update the Dec when I load a new log.

:mad: yup 400m, no idea where the 700mm came from

As for the dec of the guide star... no idea as it was so long ago I don't remember what the target was let alone the actual guide star was

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