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Benefits of Belt Mod


astrosathya

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Recently I had belt modded my HEQ5-PRO and last night i gave it a full run and i was absolutely stunned to say the least about the guiding results I achieved. I was left wondering if its even too good to be true! 
Below are Before and After images of guiding.

guiding on 30042020-2.JPG

afterbeltmod4.jpg

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You also seem to have changed guiding system?

In first image your guide resolution is 4.75"/px while in the second image 0.58"/px

I think that most of your improvement is from wrong numbers entered. Belt mod can't improve DEC performance as DEC is stationary and depends mostly on seeing. If you examine your numbers on the right - DEC did not change much - it is ~0.21-0.22 pixels in both cases - which is to be expected.

Your RA dropped from 0.16 pixels to 0.12 pixels and if we calculate with 4.75"/px guiding resolution - that is improvement from 0.76" to  0.57" - which is to be expected.

That second graph is not correct, points another clue - HEQ5 simply can't achieve precision of 0.14" RMS. This is territory of 6-10 times more expensive mounts. In best conditions, HEQ5 can go down to 0.5" or just a bit below, but seeing needs to be excellent and there must be no wind. Mount needs to be tuned and modified to achieve this.

 

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3 minutes ago, vlaiv said:

You also seem to have changed guiding system?

In first image your guide resolution is 4.75"/px while in the second image 0.58"/px

I think that most of your improvement is from wrong numbers entered. Belt mod can't improve DEC performance as DEC is stationary and depends mostly on seeing. If you examine your numbers on the right - DEC did not change much - it is ~0.21-0.22 pixels in both cases - which is to be expected.

Your RA dropped from 0.16 pixels to 0.12 pixels and if we calculate with 4.75"/px guiding resolution - that is improvement from 0.76" to  0.57" - which is to be expected.

That second graph is not correct, points another clue - HEQ5 simply can't achieve precision of 0.14" RMS. This is territory of 6-10 times more expensive mounts. In best conditions, HEQ5 can go down to 0.5" or just a bit below, but seeing needs to be excellent and there must be no wind. Mount needs to be tuned and modified to achieve this.

 

you're absolutely correct there. I just found out that the equipment profile selected was OAG (1350mm) while i was guiding with Finder Guider. My mistake.. :)

culprit.jpg

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A few pointers.

You are now having more issues with DEC axis than with RA. Try dealing with those - possibly balance issues and wind / shake. Make sure you remove all backlash, or at least as much as you can from the DEC axis.

Simple finder guider will not have enough precision to measure smaller RMS error. With 4.75"/px you can measure RMS down to about 0.7" in either axis.

I have modified my HEQ5 quite a bit (belt mod, changed bearings and tuned, berlebach planet tripod, changed clamps, ...) and this is the result:

Guiding.thumb.png.f13110f7e62aad10a1068ce64eb55b64.png

0.36" RMS - measured with 1600mm OAG at about 0.96"/px (3.75um pixel camera binned x2). Mind you this was particularly calm night. Regular values are around 0.5-0.6" RMS total.

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2 hours ago, vlaiv said:

Regular values are around 0.5-0.6" RMS total.

That is a commendable outcome for an HEQ5, especially 0.36" for one night. For comparison I have one that I use on my portable rig and get between 0.7" and 1.0" depending on the night but have not done any mods on it, and just polar align using EKos. The only adjustment I did was to tighten up the bolts as there was some play in the dec axis when it arrived.

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