almcl

I have something pretty similar on my images: Putting the figures for mine (49 pixels diameter, F 4.9 scope) into the Dust Donut Calculator here https://www.ccdware.com/resources/dust.cfm suggests that it is 1.08 mm from the sensor, which, I think, means it is resting on the Baader filter . Quick way to check if it's the camera or the scope would be to take an image and then rotate the camera through 90° and take a second one. If the mark is in the same place on the image, it's the camera. It should be possible to calibrate out with flats.

Frank There's a circuit diagram here : http://eq-mod.sourceforge.net/eqdirect2.htm that may do what you want. I tried their USB version and couldn't get it to work, possibly because of a faulty chip, you may have more luck?

I had to replace my QHY5Lii mono when the rear USB connection became intermittent and then failed completely. The very inflexible, heavy, supplied USB cable was probably the main culprit. I replaced it with an ASI 120 mini which seems to be just as sensitive, has a better USB connector/cable and, colour apart, is pretty much identical in appearance to the QHY item. It has proved more durable and has never failed to provide a selection of guide stars when used with an OAG.

While that's quite true, it may still be possible that the ripples on your star trails are in part caused by periodic error. There is almost always more than one component to PE and the periods are often not harmonic with each other. Here's the unguided appearance of my EQ5 (stepper motors rather than SW motors): It's not that regular, but it is largely down to 5 or 6 quite large but independent frequencies superimposing on each other, the largest being the worm period at 300 seconds: The good news is that with guiding, most of this can be smoothed out (it wasn't a night particularly good seeing so some of the short term random movements are still there):

Yes, a piece of aluminium plate off eBay (I think) and a spare Skywatcher small dovetail with some suitable bolts and countersunk set screws. Wasn't too expensive.

Although it is not stated here, the OP isn't guiding, just tracking, so yes, it does look like PE, but PHD2 isn't on the agenda just yet.

You've captured stars down to Magnitude 15, which is pretty good, and it seems quite close to focus as there are diffraction spikes on Phi Per (the brightest star). When stretched there's some nice colour in the stars, as well. Here's a quick stretch to show:

I think that should guide out reasonably well. BTW you have a PM.

Here's how I mount and guide my Canon + 200 mm lens on my EQ5 (ignore the stepper motors - my EQ5 was a manual at the beginning) The finderscope has an ASI 120 mini mono and regularly guides at around 1 arc sec

Not sure if this is relevant but are the guidescope focal length and guide camera pixel size entered correctly? Some have reported finding these changed for no readily identifiable reason. Can you post a guide log with one of these failed calibrations?

If only that were the case! My SW200P has had several cases of dew on the secondary and some of dew on the primary - this seems particularly the case when we have a clearance in the evening after a day of rain. The outside of the OTA is often running with water by the end of an imaging session. The angle of the target doesn't seem to make much difference. I now use a dew shield on the front end which has helped somewhat (it also improves stray light rejection) but on occasions have had to resort to a heat gun on low power to clear the mirrors. This approach carries a bit of a risk so if you discover you need to adopt it, take care!

Not necessarily so. If it's one of Juan Fieros's modifications it will still autofocus because Juan re-shims the sensor to achieve this. (Halfway down the page here: https://www.cheapastrophotography.com)

Can you take an image with your Bahtinov in place and in focus and post it here? A high ISO and sort duration shot will be fine. (If you enable the R+L in the Qlty box in APT you won't have to convert your raw files to jpg). I use the SW coma corrector with its associated 48mm adapter (takes all the guesswork out of getting the correct distance to sensor) on a Canon 700d (admittedly on a SW200P rather than a PDS) and find the Bahtinov works OK so this should be fixable.

You don't need a guide scope to platesolve. Just the main image from your imaging camera and APT can be asked to drive the scope to position of your first night's image. It will do this by solving an image, slewing to where it thinks the target is, taking another image and so on until it judges it is close enough. The tricky bit (for me) is getting the camera at just the same orientation as it was the night before so that the frames line up and don't require cropping once stacked. APT does report 'camera angle' but this isn't always reliable, I find.

Thanks for the warning, hamfisted is my middle name!

I'll certainly have a go at the connections, but wonder if it's actually further downstream than the plug. Perhaps I should look at the circuit board in the mount and check the cables there?

Julian They are a bit massive (7Mb for the debug file), but for the event in the last image above, move requests were small decimals (0.27, 0.16). Suddenly at 21.06.57 the RA move jumps an order of magnitude to 7.7 then in successive move requests it goes to 12, 22, 36, 22 before dropping back to smaller numbers and eventually to small decimals. From this, I don't think EQMOD lost contact with the mount but rather that the mount didn't respond for a while? There are no error messages that I can see so PHD2 seems to think all is well.

PHD log viewer (https://openphdguiding.org/phd2-log-viewer/) then right click the graph and select analyse selected , raw RA then the Frequency spectrum button. In log viewer they show normal(ish) guiding for extended periods then a sudden jump (as in image above) with corrections being issuedand either the star is lost (1st image) or dragged back (2nd image): The fact that the deviations show both above and below the line is puzzling me, too.

Thanks for the thoughts both! Yes, we are 'east heavy'. That's what it looks like to me, too. There's no regular pattern to it. Sometimes it will track for an hour or more with minimal error, and the absence of a pattern makes me think random electrical glitch rather than mechanical, but wondering how to narrow this down? There is a peak in the PEC at about 480 seconds, but it is fairly small, around 1.8" and PHD2 seems well able to deal with this:

My until-now reliable AZ EQ6gt mount has developed a trend just lately of going wrong in RA. Up to yesterday it has been occasional or very infrequent but last night it happened about 5 times. It seems that tracking either stops or speeds up. On the PHD2 screen the stars appear to race off along the RA axis and a 1.5 or 2 sec guiding exposure shows a streak rather than a dot. Of course, the imaging sub that is underway at the time is just a blur. I don't think PHD2 itself is to blame - it issues corrections immediately - but the mount doesn't respond or takes too long (traces below of two such events show that average oscillation prior to the event was around 0.6" or 0.8" but that when the problem occurs it got to 25" or even 50" deviation before it was corrected). So now I am wondering where the fault lies? Could it be the Lynx Astro EQdirect cable is failing in some way? Or the electronics in the mount itself, or possibly the RA tracking motor? The fact that the error appears exactly aligned with RA has put me off it being the camera and OAG moving in the focusser, although I guess it could be that? Any suggestions on how to narrow this down a bit before resorting to replacing bits in 'cheapest-first' order, or from anyone who has seen this sort of bevhaviour or may have solved it would be welcome?

It does look a bit like Periodic Error in the RA worm. Hard to say without a guiding trace (and IIUC you are just tracking, not guiding?) but when I imaged using my EQ5 and self added motors, this was a bit of an issue. I switched to guiding and then to stepper motors and that did reduce the error, enough that I still use the EQ5 when imaging with a 200mm lens, where its errors are small enough not to show.

The Guiding Assistant is on the Tools Menu. It needs to run for 2 minutes (more is better, but it can be stopped after 2 mins): To force the mount to calibrate, hold down the shift key while clicking the guiding icon:

After it has calibrated (and if you set up and take down your equipment each night you have to do this every time) run the guiding assistant. This will give some suggestions and, at least to start with, it's worth accepting these. Randomly changing settings is advised against by the current developers (https://groups.google.com/forum/#!forum/open-phd-guiding) as it often makes things worse.

I think it's more important that an object (star or something else in daytime) stays on the cross in the centre of the reticule when the RA axis is rotated. If it does, then adjusting the grub screws is going to mess up the polar scope's alignment. There's a video here about aligning the polar scope:

Alan I may have completely missed the point here, if so, my apologies in advance, but you have a camera that saves images as .fits files and you have Deep Sky Stacker, yes? Well, DSS will allow you to view the .fits files - click the drop down box next to the filename box in the load images window and select .fits. When you have loaded your .fits images into DSS, adjust the gamma slider (top right of the DSS display) then click on the first image and, once it has displayed, either remove it or click on to the next. In summary, DSS can display a wide variety of image formats and .fits should be no different.