vlaiv

2 minutes ago, Anthonyexmouth said:

Should the setting in PHD match this? 

Also, how do you estimate your "seeing" 

Sky looks crystal clear and cloudless. 

After you do your calibration and review calibration data - both DEC and RA measured guide speeds should be close to ones you set. PHD2 will report both of these values in "/s, but will indicate each, I can't remember now what is the label for them. Let me see if I can find it online. Here it is:

You don't set guide speed in PHD2 - it reads it off mount driver (EQMod in this case). If you review your mount calibration data - you will see both guide speed and Expected RA rate - which is just 15"/s times guide speed. You will also see RA and DEC rate - these two should be very close to Expected values.

I judge seeing in following ways - by eye - see if stars are twinkling. If there is no twinkle in almost any of the stars - seeing is probably great. You can also look at the star thru telescope and see what airy pattern of the star looks like. You don't have to look thru a telescope - you can use your camera - just get very bright star in FOV and do very short exposures and look at star shape change from one exposure to next. You can also judge seeing by FWHM of two second exposure. Two seconds is usually short enough so that your mount won't cause distortion of the star - just measure FWHM and you will get "relative" seeing that way - values that you can compare night to night.

Scope and Herschel wedge that you listed will work as white light solar scope - quite different thing to Lunt H-alpha solar scope.

If you are interested in very cheap white light solar - just get your self this:

https://www.teleskop-express.de/shop/product_info.php/info/p547_Baader-2459281---Astro-Solar-Safety-Film---visual-ND-5-0---200-mm-x-290-mm.html

If you still want to get Herschel wedge - it is better option, it will give you crispier views, but again - it is white light solar observing.

I'm using x0.4 or x0.3, but yes, change it down to at least x0.5.

When you do, you need to recalibrate PHD2

Looking at above graph, which is all over the place, I can't help but wonder if its really windy tonight, or seeing is particularly poor?

If none of above is out of usual, then you probably over did worm/worm gear adjustment - it's no longer smooth, or end floats, it can also cause jumpy movement.

As for PEC - do the same thing you did last time - go for quick recording, so leave the guide output and record via EQMod control panel. But I would do this last - once you are happy with smoothness of your mount. If you happen to open up mount again for another round of adjustment - you'll need to redo PEC - so save it for last.

24 minutes ago, Anthonyexmouth said:

Results after the belt mod and a first attempt at adjusting the RA worm gear

Backlash chart is closer to what it should be but its gone all jumpy. 

This doesn't look much better

Did you redo pec training, or at least disabled last one?

You stripped down your mount and there is no way that old PEC is in sync now. If you have not done so already - disable old PEC (and get new one when you get the time for it).

Above two items that I've pointed out are related.

Stock mount can have P2P Ra error as much as 40-50". This is "leading and trailing" error combined - meaning mount is a bit faster than it should be for some part of worm revolution and then it is slower than it should be for other part of worm revolution. This happens because mechanical parts are not perfect circles, but rather "egg shaped". In practice it means that if you leave your mount unguided, during the course of one worm cycle stars will drift in RA that much - P2P value. It also means that if you do one full worm period single exposure - star streaks will be that much arc seconds long.

With PEC applied this P2P error should be significantly reduced - order of 5" and that is because of fact that PEC is compensating for part of that "egginess", but it can't do it perfectly. You should also note that there won't be two exactly same worm periods with respect to star position deviation - P2P error will change from period to period and that is caused by longer wavelength errors of the mount - like RA gear being slightly out of shape. RA period is 24h so you won't be able to see that period unless you record for couple of days - which is not possible.

Rate of change is "slope" of PE curve and has direct impact on how "guidable" your mount is. It is usually reported as maximum rate of change - where the curve is the steepest. If you want to guide out all periodic changes in your mount - you should choose guide period such that it can guide out even when the position error is changing the fastest - to be able to react to that change.

P2P error is not very important in it self if slope of it is small - or rate of change is small - there is low speed change in star position - this guides out easily. Problem is of course that worm period is fixed, and higher P2P implies faster rate of change with even perfect sine wave, and period is never perfect sine wave as it consists of different harmonics. This is why you want both of these to be as small as possible.

Just for fun, why don't you try 5-6s exposures? It should really smooth seeing effects out. Maybe do comparison with Z-thingy algorithm, but we won't be able to tell the difference from guide graph - we would need to measure FWHM in corresponding subs to see real advantage of one over another.

Empty box did not happen unless there is a picture of empty box!

What's inside?

2 minutes ago, Anthonyexmouth said:

this is the graph after changing to .5x and recalibrating

 

I'm still confused - RA corrections now seem a bit larger, but still fairly small for some reason, and mount looks like not responding to guide commands (or it's responding but guide commands are so "small").

Here is a piece of mine guide graph - notice length of both blue and red correction bars:

Your red bars are of "normal" height, but blue seem so small in comparison.

At what DEC did you calibrate your mount, and do you have DEC compensation turned off by any chance?

Just now, Anthonyexmouth said:

Camera gain was set to 95. I am using the zwo driver. Would the ascom driver be better?

Only difference that I noticed is ability to use 16 bit (12bit in this case) capture with ASCOM driver. It makes my stars have significantly higher SNR - tens of times as much as with native - SNR of 200-300 is not uncommon vs 20-30 (max 50) with native.

1 minute ago, Anthonyexmouth said:

Just checked and I think I'd updated eqmod and it looks a little different to what I remember. 

Is it the ascom pulse guide settings? Ra and Dec were set to .9 so I've just changed the Ra to .5

Change both to x0.5 or x0.4 - you will need to recalibrate your PHD2 after that.

2 minutes ago, Anthonyexmouth said:

Do I increase the gain somewhere in phd2?

Pretty sure it's set to .5x but I'll check. 

Just ordered the belt mod, late night shopping is expensive,  so will that eliminate the meshing issue?

While I was at it I also ordered a baader click lock and Altair flattener/reducer

Belt mod will certainly remove gear meshing problem. Be careful to put enough tension on the belt. I had similar problem with belt because of low tension - it also did not mesh properly, and 13.8s was there, although smoother than yours - more sine like. After I adjusted tension - it went away.

Camera gain is under camera tab of advanced settings:

5 minutes ago, kens said:

I know how it works - I wrote it  It is a digital Bessel filter with a tuneable cutoff frequency.  Unlike the other algorithms it has flat response in the pass band and no nodes in the stop band and being a Bessel filter has linear phase response. The filter is fourth order so approximately 24dB per octave suppression above the cutoff.

It is the ability to tune the cutoff frequency as a function of exposure time that makes it useful. By allowing short exposure times you can reduce latency but still filter out the high frequency seeing-related deviations.

Ok, so it's not what I thought it is, and it indeed sounds interesting. I'll actually give it a go next time I'm out.

This basically means that it's working the best with rather short exposures - like 0.5s-1.0s?

How does it deal with wind - being sharp jump, I'm suspecting that frequency response will be spread out for such signal?

Your RA graph shows quite strong 13.8s period - and this is motor gear meshing period - it looks like motor gear on RA is not meshing properly. You can try to adjust this by changing how the motor is seated in housing.

Because of this, you need lower guide exposure 1s or 1.5s. What sort of gain are you using with your camera? Can you increase it? Maybe use ASCOM driver instead of native one in PHD2 and select 16 bit output and higher gain.

Also, your RA corrections are rather small - I can hardly see them on the graph. Not sure why is that. What guide rates do you use on your mount? x0.5 of sidereal or less (down to x0.3) should be good.

What does your guide graph look like now with PEC?

I marked out bad:

P2P error is large - you want that to be smaller - with guiding you want your p2p to be less than 2".

Second thing marked is max drift rate - you want it to be lower, so that drift limiting exposure is something like 8-10s. You want to guide at about half to full drift limited exposure. Meaning that your guide exposure should be anywhere from half to full max drift rate. Longer guide exposure helps with seeing, but you can't have it be larger than drift limited exposure (about half is max really when you have "smooth" mount).

Belt mod should sort both of these issues, and a bit of backlash as well.

I would say that such positive feedback has something to do with DEC aggressiveness being set to 100 and calibration.

If there is even small calibration error - and that would be perfectly normal, you can think of it as calibration SNR - there will always be some error due to measurement, and you set aggressiveness to 100 - you might actually give too much correction. Due to calibration error, PHD2 thinks that it needs to counter 0.2" with pulse correcting it by 0.5" - mount promptly responds and places star to 0.3" on the other side of graph - phd2 sees that, tries to correct with 0.7" pulse - which brings star back to first side of graph and position of 0.4" (0.3 - 0.7 = -0.4) and cycle continues with even wider oscillations.

This is why it is good to have aggressiveness lower than 100% - you will dampen down any sort of positive feedback that might arise from calibration error.

Combating star saturation is easy - just choose fainter star to guide with . There are other things that one can do - use lower gain (requires redo of darks), but also using ASCOM driver instead of native and going for 16 bit helps with this quite a bit, since there is larger dynamic range in guide images and stars won't saturate so easily. This last one also helps with SNR - which is good for star centroid precision.

3 minutes ago, kens said:

The Mesu could well benefit from the Z-filter algorithm with a shorter exposure time - especially if you are getting good enough guide images to saturate stars.

The exposure factor can be set so you don't chase the seeing.

I'm not sure that is the case - at least if I'm understanding what Z-filter algorithm does. It "learns" fast frequency periodic oscillations and adapts? Mesu does not have harmonics at all (or at least it should not have those), so I'm not sure if algorithm that looks for regularities would benefit it.

1 minute ago, Anthonyexmouth said:

How do you tell it's the Dec that got nudged?

Will the belt mod change the pec curve?

That's cause I'm certified pixel peeper

If you examine your image, you will see that almost all stars have small "ghost" image:

This happens when image is "displaced" for a few seconds and star ends up next to where it is supposed to be. If signature is really faint (like above) - that means it stayed very short time at that position. If signature is smeared - there were probably more than one "excursions", but clear ghost image is indicative of single one.

Direction of jolt is easy to find - just look which way RA and DEC go. With Orion's nebula, three stars in nebulosity are pretty much matched with direction of RA:

And if you look at ghost image, you'll notice it's perpendicular to it, and that would mean DEC.

If you do belt mod, your pec curve is going to change, no question about it. Both in shape, but also in "position" (you will remove step motor to fit belt). Btw, to keep PEC properly working, you need to always park your scope to home at end of session. You also should not use your scope with hand controller. If you change RA step motor "position" (or rather worm position in respect to what EQMod thinks it's home), you will need to redo PEC curve. There is option to "resync" PEC curve by shifting phase - but I don't think it can be done with any real success.

It also looks like you had a small jolt in DEC - probably wind.

4 minutes ago, Anthonyexmouth said:

Not sure if its really made a difference, but this 10 min sub looks better than any before it, but that might be the 1 ton of concrete in the pier that i never had before

I'm almost certain that much concrete won't hurt (unless dropped on someone)

Mesu should be "stiff" mount and it should benefit from 90 aggression.

Can I make few suggestions?

Star that you are guiding on is clipped - choose one that is not saturating.

Don't let that indicator turn to red.

By your SNR I suspect that you are using ASI174 with native drives? How about switching to ASCOM driver instead. Choose 16bit format. You'll need to redo your darks for that.

Lower min mo for both RA and DEC to 0.10. Switch DEC guide algorithm to hysteresis as well and use 90/10 for both. Experiment with 3,4 and 5s guide exposure lengths (I have sneaky suspicion that 5s will work the best ).

You mean aggression rather than hysteresis?

What mount is that? I see both mesu 200 and eq6 in your signature.

That's about it - it's now recorded and stored in EQMod - it will be applied each time you select Sidereal + PEC (and it will be selected by default unless you change it).

Approach that you used for recording is "automatic" - meaning EQMod records curve based on issued corrections and now knows how to "preempt" corrections by variable tracking speed - this will lessen the load on guider and enable you smoother guiding as well.