michael8554

1) To avoid locking on a hot pixel try setting the HFD to 1.5 in the Brain button/Guiding tab, and untick Star Mass Detection. You say you are choosing good unsaturated stars, but you should allow PHD2 to select a star, it knows what's good for it ! Tools tab/auto select star 2) In the left-hand pane of the GA results is Drift-Limiting Exposure, which was 0.8 seconds. But then it also always says to use 1 to 3 second exposures too in the right-hand of the display ! 3) All I'm suggesting is to try a faster exposure, say 1.5 or 2 seconds, for 5 minutes without changing anything else, and see if it gives faster reactions to the excursions, and a smoother guiding graph as a result. If the graph starts to yoyo then reduce the Aggression until it settles. As I said, time to experiment a bit, but allow enough time for each new setting to stabilise. Did you try balancing to take up the Dec backlash ? Easing into my thoughts on your results, I didn't think your "poor" exposures were drifting that much, I'd be interested to see if others agree. What is your criteria? Is it the Score for each exposure in DSS ? Try stacking all your subs and comparing with your best stack, if you're unhappy then ignore me ! Michael

Before I reply fully, some questions for you, but I would say that you are at the stage of fine tuning your PHD2 settings. 1) I notice the 4 failed Calibrations before your final good one. Are you allowing PHD2 to autoselect a suitable star, or choosing your own? 2) The GA suggested 0.8 seconds exposure, which suggests very choppy Seeing, but you used 2.5 seconds - is your camera not sensitive enough to use faster exposures ? The GA is saying that to keep around the 0.10 Min Move, you needed fast corrections, and 2.5 seconds was too slow to catch the RA moves. 3) However I'd say 0.8 seconds is a bit excessive, but what are your guidestar exposures like at say 1.5 seconds ? Michael

With a very basic motor drive, speed would vary with voltage. A better designed drive would only rely on the supply voltage to power a circuit that self regulates the speed irrespective of the supply voltage . I don't know which you have. Michael

The Full-Frame camera may well be vignetted, but you can always crop, down to where you would probably crop with a APS-C. Yes EF lenses may well be expensive, but Chaz is hoping to use his EF-S lenses, so maybe Full-Frame is out. Michael

Canon 6D seconded - Low noise AP at ISO 1600, allegedly has better Ha response than most Canons, though I modded mine. Michael

10-99 Good Buddy..........

GA once only at the start of each night, Calibrate near each new object. Michael

Hi Sean My Hauwei phone ? No way Jose, of course I haven't got one, for obvious reasons 🙂. English humour at its worst. Unfortunately the North Korean missiles seem quite reliable. GA is a good starting point each evening, unticking the Check Backlash box once it's started will save a lot of time since you already know it's bad on your mount - down the road you might want to try adjusting your Dec worm ? You can set your mount's Backlash setting to zero during the day, look in your instruction manual first. Your missing files? Try the Windows search routine. Search for files created on the date in question, and for file types enter a * before .CR2 (eg *.CR2 ) which will find all CR2 files created that day, if CR2 is the format you saved them in. Not so much how your guidescope is attached to the imaging ota, more the way the guidescope is held in its mount with two screws, which if nylon or soft tipped, are going to move those microns I mentioned. My own finderscope is mounted the same way as your guidescope, and needs realigning every session, it's that imprecise. But it was just one item to tick off the list, if you find down the road that you're getting good guiding across the sky, then no problem. Michael

A lot to digest there Sean, but here goes: I don't have an explanation for the short period of drift after releasing any of the slew buttons - unless you have Backlash Compensation enabled on the mount, as mentioned before ? Trailing in Dec on your images when PA is good could be due to Dec Backlash, which can be minimised with one-direction PHD2 Dec guiding. Guiding Assistant gives a confirmation of your PA, and gives recommendations for PHD2 settings based on the Seeing for that session. In your Friday run it shows Dec heading off south due to your 8.1arcmin PA, that your RA PE has peaks of about 20arcsecs. Dec Backlash is 5,839 milliseconds, so the recommendation is Dec guiding in one direction. Also suggests a 1 second exposure, you used 3 seconds. As you gain confidence you will use GA less frequently. Guiding in one direction entails: Setting PA to be no better than about 4 arcmins, so that the mount gently drifts in one direction. Balance the scope to be slightly heavy in the opposite direction, which takes up the backlash. PHD2 will correct the gentle PA drift, and if the scope balance is right, it should not go out of balance in the opposite direction, which could take 5.839 seconds to correct ! Friday night, no drift after releasing slew buttons - let's hope you are now good to go for future sessions 😆 You deleted the M3 and M57 images and emptied the Recycle Bin ? I've used my Huawei phone to hack a North Korean nuke missile test, it's heading your way....... Your M51 image, composed of your good subs, is as good as I get in terms of star shape, but a jpeg of one of your 10% of poorer 3 minute subs, stretched if necessary, would have been more informative. Now to your guiding. There are many Dec excusions of up to +/- 5 arcsecs, which will give you Dec drift on some of your 3 minute subs. Try Dec guiding in one direction only ? I notice you are ST4 guiding. PHD2 can compensate for the different guide corrections needed for high and low Dec targets, if you have cabled to give RA and Dec positions to PHD2. You haven't, so in your case PHD2 recommends you do a Calibration for every different target, so that PHD2 can give correctly sized guide corrections for each target Dec. I can only see one Calibration, despite targeting three different objects at 47 Dec, 28 Dec, and 33 Dec ? Now a word about your guidescope. Your imaging scale is about 1 arcsec/pixel I would guess, and your guide image scale is 6.62 arcsecs/pixel, according to your PHD2 settings. That means if your guidecam shifted only 1 pixel (5.2um) due to a less than optimum mount, your images would move nearly 2 pixels on your T6i. Is your guidescope mounted rigidly enough not to move small fraction of the thickness of a hair under gravity as the mount tracks to different positions ? When you have experienced unwanted moves in you imaging, it's worth removing a possible source. Hence the concerns of some of us ! Michael

To me this means you are pressing the RA button ? If set to a very slow Slew Speed you might be able to move the mount (in Dec too) the tiny amount required to give a 12 pixel Dither to the dslr. This delay won't give you a dither for the reason I supplied. But If you are shooting untracked, then yes each exposure will be shifted due to the earth's rotation. You'd have to work out how long to pause to give the correct amount of pixel shift, and after a number of exposures field rotation would start to be a factor. Michael

DC is tracking but not guiding, so no RA dither unless his tracking rate is way out ..... Michael

Look forward to seeing the before and after images. So after centering the third alignment star, it continues drifting across the dslr screen. Is that in dec or ra, is it always in that direction, how long does it drift for ? Are the stars in your images drifting in the same direction, or is it different in each image ? Michael

To sum up: Your PA is good, and your guiding is good enough that stars shouldn't be drifting. I'm having trouble understanding what your problem looks like on images. Perhaps you could post a before and an after jpeg, same durations, from sessions before and after your problem arose ? Michael

Dither would do, it but I see you aren't guiding, which makes random 10 to 15 pixel moves difficult. Michael

Nice report almcl. I haven't spotted the statistics/drift box before in Log Viewer, I see it reports PA. Now you've suggested flexture, I see Sean has an Orion Deluxe Mini Guidescope, which has an absolutely awful finderscope type mount. Michael

Hi Sean Looked at 4 of your PHD2 logs, but I don't see any Guiding Assistant runs ? So no indication of the mount's behaviour when guiding is not running - so no PA, Backlash, or PE readings, so also no recommendations from PHD2 as to what settings to use for each night's Seeing conditions. But as you say your guiding looks okay, apart from some occasional large Dec excursions that overshoot on correction and take a while to settle - a sign of Dec Backlash. And most puzzling, some of the logs are showing the mount's RA and Dec position, some aren't. If PHD2 doesn't have that info then you must Calibrate close to where you're imaging, as guiding varies with Dec. Does your mount have Backlash Compensation ON - this attempts to take up the slack on GoTo's, so on manual moves can move the mount after you release the button ? This would be my guess as to the cause of the problem, not a guiding issue. PHD2 recommends to turn off Backlash Comp on the mount and use the PHD2 Backlash Comp, as calculated by the Guiding Assistant run !! Finally you are on an old release of PHD2, but I wouldn't change that until your current problems are sorted. Michael

Then you'll need to get your Dremel or needle files onto the adapter to open up the gaps the bayonets go into. Shouldn't affect the final locking of the lens once you can rotate it, and there's a locking ring too on the adapter. Try comparing the bayonets on your T adapter that will fit, with one of your lenses. Michael

Everyone on this site will tell you you're wasting your time imaging at 2800mm........... 🙂 Nice image. Michael

Are you talking about the star images on the PHD2 display ? IMO they never look as good as in say SharpCap, I would look at the PHD2 Star Profile - is it sharp, is HFD 3 to 4, is SN better than 20 ? Michael

What do you mean by too small ? Does the bayonet engage but you can't rotate to lock it ? If the bayonet won't engage remember that the 3 bayonets are different sizes , which is why the lenses and camera bodies have the white or red locating pips ? Michael

Tried the Stark Labs Yahoo Group ? Michael

I tried imaging last night. The Test setting was useful. I usually try a quick test of 60 secs at ISO 6400 to confirm framing, then extrapolate from the histogram the exposure at ISO 1600, then set camera to ISO 1600. Now I can swap between test and imaging sequence. The laptop crashed to blue screen when I tried to connect to the mount with ASCOM, when already connected to PHD2. Maybe no surprise with a alpha or beta release, so I'll leave it alone until a better release comes along. Michael

With the covers off, is it possible to disconnect the drive cable to the dec motor ? Then repeat your previous test that showed drift. With the ST4 cable off too. Michael

What figure does Guiding Assistant give for your Polar Alignment error ? If drifting up the screen is in Dec in your setup then this is possibly a sign of poor PA. Michael

Sorry Nigella, I see now you're not the software developer. So far I've tried running it with nothing connected. Some parts of the display are lost on my 1280 x 800 display, and no pan bars to reframe. The displayed latitude isn't what I entered. I didn't find a log file in C/astrozero to send on. Michael