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PHD graph on HEQ5 help please

GrantEb

By GrantEb
in Imaging - Discussion

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GrantEb

GrantEb

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Hi All

Please could someone point me in the right direction.

I have drawn a graph which is as shown on EQMOD whilst guiding.

Am I right in saying the DEC looks OK, but the RA is being "over guided"? I have tried a few settings, but don't want to play to much, otherwise it may not work at all.

It's a HEQ5.

Many Thanks

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Euan

Euan

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The RA looks right, you would expect it to jump back and forward to try and maintain it's position

The DEC looks like it's not guiding at all, is it disabled in PHD (I can't remember where it is but someone will probably point it out)

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GrantEb

GrantEb

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Another thing, when the mount is tracking, without guiding input, it is quite silent, all you can here is a sort of high pitch sound.

But when autoguiding, during cal, you can here it "clicking", and when guiding, it makes the same sort of sound, doesn't sound very "smooth".

Is this normal?

cheers

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James

James

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My EQ6 clicks to but doesn't seem to be a problem. I can also smooth out the RA line by choosing a slightly longer exposure time, say 2-3 seconds and by deliberately unbalancing the scope (if scope is pointing east them move the weights out further a little, if pointing west then move the weights in a little).

James

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Merlin66

Merlin66

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I'd say it sounds pretty normal.

The PHD guiding just replicates the pressing of a guide button to cause the mount to move in the "correction" direction at the chosen guide rate. Every time it issues a "correction" signal, it's pressing a "virtual" button on the motherboard.

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chrisshillito

chrisshillito

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Hi All

Am I right in saying the DEC looks OK, but the RA is being "over guided"? I have tried a few settings, but don't want to play to much, otherwise it may not work at all.

It looks to me as though there is a constant drift in declination and as a consequence PHD is always issuing the same length guide pulse - hence the straight line. The RA axis is showing some over correction as the guiding pulse direction is frequently reversing.

Take a look at my EQASCOM guiding document, there is an explanation of how to interpret the pulseguide monitor displays on pages 6-8

Chris.

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GrantEb

GrantEb

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Thanks Chris. I see now that i can adjust the Width gain sliders once guiding, I will try this tonight. I thought this just adjusted the graph scale.

Would you say the dec is OK for now, and I should work on the RA, or both?

Many Thanks

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chrisshillito

chrisshillito

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There are two sliders associated with each graph. One adjusts the graph scale, the other, the gain slider, provides a dynamic overrides of the pulsewidth. Some guiding apps don't let you adjust their guiding parameters whilst guiding (PHD didn't used to, it may do nowadays) so this slider allows provides a driver base control over guiding "strength".

I'd say the DEC is fine - the constant level of drift that is being corrected for is probably due to a slight polar alignment error.

Chris.

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GrantEb

GrantEb

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So I tried last night, still no better after trying alsorts of settings. (5hrs)

Wondering about this though.

I started up EQmod. Used Stellarium to slew to Deneb. Loosened clutches and manually centred on Deneb. DID NOT SYNC ! Closed Stellarium

Then opened PHD, carried out cal, and guided. tried alsorts.

My question is, will not SYNCing, on one or more alignment stars affect PHD guiding the mount, or does it ignore the alignment SYNC's completely?

Thanks

Cheers

PS: Thanks Chris for yor help so far!

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Ant

Ant

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I'm no expert, but for me the RA graph is exactly how I have seen everyone's graph - some are smoother than yours but every graph I've seen goes up and down above and below the centre line.

The DEC graph looks completely wrong, again all the graphs I've seen the dec looks very similar to the RA graph.

Ant

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Ant

Ant

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PHD is independent of the synchronizing. The Star align process gives you better goto accuracy and is only used by the handset when gotoing or the planetarium software.

Phd doesn't give a monkeys about that - I only ever sync to one star close to the object that I'm going to image and my guiding is normally OKish...

Ant

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GrantEb

GrantEb

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Thanks for that - Ant

Merlin, I haven't tried manual controls, but last night found that the dec is guiding perfectly. My star trails are RA. Will all tried settings, it either over corrects or under corrects.

What I have noticed though, is that there is not much difference in the star trail length on either 2 min exposures, or 5 min exposures.

I have let it track for up to 30mins, it never looses the star, just "wobbles" in RA.

Cheers

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Whippy

Whippy

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Just looking at your sig, are trying to image with that 10" on a HEQ5? If that's the case then IMO you've got a far too big a scope on that mount. I'd also wager that you may well suffering from flexture too and that's what your problem is, not PHD.

Of course, if you're just using your Canon on it's own then ignore me :).

Tony..

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chrisshillito

chrisshillito

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The DEC graph looks completely wrong, again all the graphs I've seen the dec looks very similar to the RA graph.

Ant

Ant,

The graph that has been posted is that as displayed in EQASCOM (don't confuse it with PHDs error graph). The y axis shows the duration and direction of corrections being received, the x axis is simply each correction event (not time).

A straight line therefore tells us that EQASCOM has received successive corrections in the same direction and of the same duration (within the resolution of the graph scale). This doesn't imply anything bad, just that for PHD is successfully fighting against a constant rate of movement in DEC (most likely a component due to polar misalignment). If PHD weren't successfully correcting we would expect to see successively longer duration pulses logged.

Chris.

Chris.

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GrantEb

GrantEb

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I would tend to agree with you Whippy, I know the scope is to heavy for my mount, but I am determined to get it right.

I have tried guiding with just the 1000d and 200mm lense, and guidescope on mount, with exactly the same results. The wobbling stays there.

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Merlin66

Merlin66

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Yes, just connect the camera via the ST-4 ports and set up PHD to "see" the mount.

I'd still suggest using the PHD manual adjustments to see the corrections. It maybe that your duration and or guide rate setting are causing the concerns...

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