michael8554

Your log file is incomplete, the Cal was at 22.47, your post only goes up to 21.20. Please don't cut and paste from the file, post the whole file as an attachment. Michael

PHD2 was probably guiding well after your recent tweeks, but the data on the quality of guiding, the graphs and tabular results, were wrong. So you see nice flat lines in your screen grabs, but the reality is different. The guiding probably won't be any better or worse with the focal length corrected, but you won't see nice flat graphs, you'll see what is actually happening. In fact it would probably be okay to carry on with your current Calibration and pixel graphs, no problem, but don't go showing anyone your amazing 0.15 arcsec guiding, cos it's not so ! Michael

Calibration has gone from one extreme to the other. If you have entered the correct guidecam pixel size, guidescope focal length, and have a guiderate of at least 0.50, the mount should Calibrate in about 12 steps. The last Cal was 34 steps in RA ! Post the Guidelog, this will show where it's going wrong. Michael

Excellent work on the backlash, I'm impressed. Looking at the Guidelog, every comment starts with "good". Good HFD = 3.09 Good PE Good backlash. However, to rain on your parade: You didn't enter the focal length of your guidescope, so the Cal and guiding figures are, well, not Calibrated. Explains why Cal has jumped up to 26 steps. So the guiding results of RA = 0.15 arcsecs, Dec = 0.10 arcsecs, are out of this world. If you use the Profile Wizard you can't miss any settings. Also in your screen grabs, the graphs are set in Settings to show pixels instead of arcsecs. You need to see arcsecs if you're aiming to tweek settings for the magic sub 1 arcsec guiding. Almost there though ! Michael

The typical backlash in either axis can't be felt by rocking, it's just to small to detect. In other words if you can feel it it's miles out ! Wrong way round - in your case the RA balance NEEDS to be slightly out so that the gears are always in mesh = no backlash. Yes a great improvement in Dec backlash. PHD2 will tell you about the Dec Backlash but that doesn't always mean you can't go ahead and guide. Once you have a good or acceptable Calibration you use it all the time. Michael

A 700D has a spring loaded sensor, and getting the sensor back in place without tilt is difficult. I suggest a 450D, 500D, or 550D, that have shimmed sensors. Michael

For visual use alignment to magnetic north should be more than good enough. For imaging the mount should be aligned to the axis of rotation of Earth, so align with the North Celestial Pole (NCP) aka true north. Magnetic North at Grimsby is about 30 arcmins out, good enough Polar Alignment for guided imaging would be 5 arcmins. Michael

Well RMS readings on your last two runs were 0.7 to 0.8 arcsecs - RA and Dec are similar, so you should have round stars. The star Mass and SNR were all over the place indicating poor seeing, so not bad for 1 second exposures that were probably "chasing the seeing" ?? The RA overshoot on the east return of Cal is back, maybe balance has changed, RA no longer always meshed ? 2 secs Dec backlash isn't so bad, does anyone get it perfect ? I'd leave it alone. I'd say you're nearly there. Michael

So you've no ideas as to why the guide rates are so different ? Michael

Yes, the psuedo JPGs that camera LCD's and PC's display have no real relationship to the actual Raw. Out of interest could you post one of your 2.5K Flats please ? Michael

Sorry, didn't spot you had PEC off for the test. Having seen the latest Cal I'm beginning to realise that RA rates must be correct - your Sidereal tracking test confirms that. RA true rate 1.367 at 13.5 setting Dec true rate 1.170 at 6.0 setting (could go up a bit, try 6.5 or 7 ?) So it's Dec that is the wrong rate - but GoTo's are correct ? Do they go through EQASCOM or by the mount's firmware ? I've found the lengthy 2011 discussion on doing the mod, I shall have to plough through it tomorrow. I did notice that early on the Tracking Offset (whatever that is) for 4:1 was -211, you have -189 ? Perhaps you could do me a short precis of how the ratios are worked out from the motor pulse rate onwards ? Michael

A quick report as I'm imaging. The change in RA and Dec Guide rates has given a good Cal, equal steps on both, none of those RA overshoot on the east return, but there's that Dec Backlash. Must be a reason why the drives are so different ? A 50% error can't be wrong size cogs. Was the mount behaving before the belt mod ? That's 6 secs to change Dec direction. If you can't improve that on the mount try PA to about 5 arcmins and guide in the direction that pulls the Dec back to a straight line, with Min Mo a bit more than usual. The Periodic Error on RA is about 50 arcsecs peak to peak, if the mount has PEC would be worth applying. But more anon Michael

Hi David, That's interesting, what ADU were the ones that worked ? Michael

Yes you can rotate the scope in the loosened securing rings to place the eyepiece in a comfortable position (tighten afterwards). Michael

Can I have them please, Co-Op hasn't had any for weeks.........? 🙂 (Sorry, dont think i'm breaking the virus guidelines ) Michael

If I've understood your question, once the payload is in orbit the individual starlinks are ejected like bullets from a gun, and appear as lines of 40 to 60 , until sent off to orbits that ensure there will be some in view wherever you are on earth. Michael

I can generalise: The longer the exposure the more noise The hotter the weather the more noise Most DSLR's, not all, higher the ISO, the more noise. So you should do tests on your camera to find the sweet spot of exposure and ISO. Dithering or Darks can reduce noise on the stacked results. Michael

After accepting the Guide Assistant recommendations and guiding for long enough to see how they work ! Michael

Yes I've noticed the predictions are a bit flakey. They may be above the horizon for quite a while, but not visible because they're not in sunlight all the time. At some point after launch they start to move out of line into their allotted orbits and orbital height, which can be N-S. E-W or anywhere in-between, so maybe that's the reason too. Michael

I've been searching for an image of the scope in a normal viewing position. Would you believe it, every image is of the scope in the "Weights Down" lineup position ? Keith, if the scope is balanced you should be able to release the clutches and twist the scope around on its pivots, to get the scope pointing where you want, with the viewing hole at a reasonable height. Michael

And why can't you see Polaris centred in the eyepiece I hear you say? Because Polaris is close to but not at the North Celestial Pole, it's nearly 1 degree away. So Polaris will be off-centre when viewed with a well PA'd mount Michael

And decent kit too, none of your EQ mount and Newtonian rubbish........... 🙂 Michael

No. Giving PHD2 the ability to make big corrections can quickly correct any large guide errors that come along. PHD2 will still be able to make small moves when needed. So more a case of Aggression and MinMo settings - after you've adjusted the RA worm. With those 2 arcsec spikes ?? The source of endless argument on this site ! Not necessary they say because the Alt and Az adjustments for PA take care of any error in level. But roughly level prevents Alt and Az adjustments interfering with each other. That's my opinion and I'm sticking to it...... Michael

Here's RA: I think I see the RA binding you mentioned. The red arrow points to the MinMo setting - I still haven't seen any sign of a Guide Assistant run, so you're guiding blind. Here's Dec: Same vertical axis scale as RA, guiding is twice as good, except for the big up then down episodes. Left to itself Dec would probably chug along at 0.5 arcsecs, which would be good in itself, but there's that MinMove again that sends it off northwards, Dec Backlash takes ages to clear, so it careers down south etc etc. Try a higher Dec MinMo. Michael

In Arcsecs/sec Michael