vlaiv

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?

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.

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

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:

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.

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.

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.

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.

That is "perfectly normal" PEC curve. It's not going to be simple sine wave because you have at least couple of components added together.

Excellent!

Forgot to mention - best time to record PEC is full Moon

Depends. I was describing "old" manual way of creating PEC curve. I think that one offers more flexibility and allows you to see PE data and choose how to create PEC curve. You can do all sorts of analysis of mount behavior with PECPrep. For that one you need "clean star motion" data in PHD2 log, so no guide corrections, only star position. There is new way of doing pec in EQMod - autopec. This is when you just press record in EQMod control panel. For this to work you need your guiding turned on. EQMod can "listen" to guide pulses and based on that reconstruct PEC curve, but in order to do it, actual corrections need to be sent. This process is "automatic" and it does not allow you to either see the data nor to analyze it. http://eq-mod.sourceforge.net/docs/eqmod_vs-pec.pdf check page 9 - autopec for how to record with new/simple procedure

Guide output is option in PHD2 - there is check box (somewhere, I can't remember exactly, but I'll look it up on line now). Uncheck that particular checkbox and guide output will not be sent from PHD2 It's generally better to capture as much worm period cycles as you can - it's like stacking subs - more subs you stack - better the image. Each captured worm cycle will suffer all sorts of "noise" - wind, seeing, large period error (period of more than half hour or hour - which is not of particular concern, but you want to "cancel" it out with multiple worm cycles). I usually go for 8 - 10 cycles, I think I never had patience to do more than 10 cycles

I think it's worth doing. PEC works very well with guiding if you are using EQMod. There are couple of benefits of it. First is that you get a chance to understand how your mount behaves. When you load PHD2 log into PecPrep you have a chance to analyze mount behavior. One of more important things to note is after you generate PEC curve there is "residual" shown - note max RA change rate. It will be expressed in arc seconds per minute or per second. This will tell you maximum guide cycle that you can use. Longer guide cycles are something you want to use as it smooths out the seeing. In order to use longer guide cycles (like 5-6 or more seconds) you need smooth mount and you need your periodic error after correction not to change rapidly. If max RA rate is something like 0.06"/s - and you use 5 second guide cycle - at worst your drift between corrections will be 0.3". It will enable smoother guiding as well because there will be less corrections issued - and corrections are not ideal so you want as few corrections as possible to keep the mount on track.

Here is how I do it: Disable any PEC if you already have it loaded in EQMod (there are controls for PEC in one of the tabs). Fire up PHD2 and do calibration near equator. Disable guide output for PHD2 and start "guiding" session (mount won't be guided at this point because you disabled guide command output). Make sure you have logging enabled in PHD2. Do about 1 hour and 30 minutes of recording. HEQ5 has worm period of 638s and you want as much full periods as you can. If you want for example 8 full periods, that is going to be 1:25 or something like that. Make sure you record for at least 1 minute past complete cycle just to make sure you got it. While you are "guiding" at some point - press PEC timestamp button in EQMod. Once you are finished, just stop guiding and close PHD2. Next start PECPrep on same computer, load phd2 log and analyze PE curve. Choose only harmonics of Worm period in main window - generate PEC curve and save it. Load it into EQMod and make sure you have PEC gain set to 1. From that point on, it should be always loaded when you start EQMod - and default tracking rate should be Sidereal+PEC. That is it.

Don't think you need to be concerned with this - this is something that flats can easily remove. I've found similar thing with my ASI1600 - but not in form of vertical stripes - more like checkerboard pattern. Here is H alpha flat (not solar, but regular Ha filter for night time imaging): Pattern is readily shown, but it calibrates out with use of flats. I think such artifacts are consequence of manufacturing process - micro lenses or something else when creating sensor on silicon can lead to this. Even additional circuitary between pixels - maybe not each pixel is exactly the same size - some of them might have small part of pixel dedicated to integrated circuits for readout or amp stage.

I don't think you'll go wrong with this one: https://www.altairastro.com/Starwave-102ED-FPL53-Refractor.html I think it's the same optics as this: https://www.teleskop-express.de/shop/product_info.php/info/p9868_TS-Optics-PhotoLine-102mm-f-7-FPL-53-Doublet-Apo-with-2-5--Focuser.html Or this one: https://www.stellarvue.com/stellarvue-sv102-access-ed-apo-refractor-telescope/ Old FPL-51 version was also branded by Altair Astro, now only sold by TS as the scope you linked to in the first post. FPL-51 one shows CA on brighter targets, and I remember reading one review where it showed pinched optics. Here is review of it (AA version): https://www.altairastro.com/public/reviews/Starwave-102ED-Review-Sky-at-Night-Magazine-Issue-86-4_stars.pdf I think that new version with FPL-53 glass is better choice if you can afford it. I've been interested in that scope for quite some time now (waiting for funds to become available to get one for myself). According to reviews, optics on that model should be really good. I think that FPL-51 is still good scope for the money. 100ED will surely show better image, but 102 F/7 will be more portable, easier to mount and will have better focuser. It will also show wider view. I would call it a compromise. FPL-53 one I would not call compromise, I believe it will show the same quality image as 100ED with all mentioned advantages - wider field, shorter physical length and better focuser.