michael8554

1. Does your "long FL reflector" have enough focus range to accommodate an OAG ? 2. Focusing the guidecam can be fiddly, so I recommend one with a helical focuser for the guidecam. Again. if the OTA will focus with that extra image path length. 3. The prisms vary in size from 8x8mm to 12x12mm. The bigger prism gives a wider FOV, so more chance of getting a bright-enough guidestar. If the guidecam sensor is large enough to cover the prism size. Michael

Is it the OAG ? IIRC there are posts here and on other Forums to the effect that 2600's often have tilted sensors ? Michael

Uneven star images may be due to tilt rather than a faulty CC. Michael

Hi Bryan Seems to be all about the Flats, so can you post one ? Could be reflections. If the FR is first you get a wider choice of guide stars, can't you raise the prism to stop it shadowing the imaging camera ? (If the OAG is before the FR, do you have the full FL in the guide prog, just checking ?) Michael

Hi Peter I agree with Bryan, your guiding after the flip wasn't as good. Compare the guide statistics before and after the flip. Michael

Before moving to the target I focus my DSLR on a nearby bright star, using magnified LiveView, a Bahtinov Mask, and Bahtinov_Grabber software. Shouldn't you fix that first ? Michael

To expand on what Sam said: You might need to bin to double the guide image scale if it's low. Or to improve the sensitivity of a budget guidecam like your QHY5L II. Michael

Section 5.8 - User Defined Objects ? Michael

Hi David Depends whether it's a LX200 Classic or a LX200GPS/ACF. The LX200GPS with ASCOM and the ASCOM Meade Generic driver will work with PHD2, and so maybe with ASIAir, but at that long FL I'd recommend an Off Axis Guider. Which will require a sensitive mono guidecam, a budget ASI120M may not be sensitive enough. Michael

Hi Matt Question mark noted. You will need to post the PHD2 GuideLog so that the error message can be read. Michael

Did you understand my opinion on your guidescope focal length ? Did you understand my opinion on the cause of the drift over the 6 hours ? How did you Polar Align ? PHD2 saves a GuideLog for every session in the PHD folder. Look for the correct date in the filename. I've never had the exposure set to Auto. These are explained in the SharpCap documentation: Max Dither Step – this specifies the maximum distance that any dither movement can be, measured in guide camera pixels (i.e. pixels in PHD2, not in SharpCap). Note that MGEN does not take any notice of this setting, and that if Dither Only Guiding is selected then this setting is interpreted as the size of the dither movement step in arc-seconds. Settle Threshold – when the movement between two guide camera frames drops below this number of pixels then the dither is considered to have ‘settled’ – i.e. the mount movement is complete and images taken should no longer be blurred by movement. Only applies to PHD2 guiding. Minimum Settle Time – a dither will not be considered to be settled until this amount of time has elapsed after the end of the movement, even if the Settle Threshold is met before this time has elapsed. Only applies to PHD2 guiding. Maximum Settle Time – a dither will always be considered to be settled after this amount of time has elapsed, even if the settle threshold has not been met. Only applies to PHD2 guiding. Michael

What figure was that ? The drift sounds like the cumulative effects over 6 hours of a small PA error, plus a little due to Dither. The PHD2 setting is a multiplier of the setting in the software that is generating the Dither. So if you have a 12 pixel Dither in SharpCap, then a 0.1x setting in PHD2 will change that to a 1.2 pixel Dither. But why would you want to turn off Dither, it is usually beneficial to images ? I guide a 1280mm scope with a 200mm guidescope, 540mm sounds excessive to me. But depends on the image scales of the guidecam and image cam, let's see the GuideLog. Barlowing the guidescope raises the f/number by 2.5X, so now the guidecam will require much longer exposures. You should let PHD2 choose the stars, another sign that the high f/number is giving PHD2 a poor choice of stars . Michael

Hi Matt Rather unfair to say the problem was due to PHD2, when you went ahead with guiding instead of fixing the Calibration ? Were the trails in RA or Dec ? The Leo Triplet is at Dec 13, but M81 is at Dec 70, which might reduce the effects of the poor Cal. A good Cal is crucial to good guiding, so it's worth trying to understand the error message and correcting the issue. You wouldn't get the message when guiding, you might have if you started a fresh Cal. Michael

Hi Richard So your stack is without any registering, showing how the FOV has altered over the period of the session ? That's just due to a small PA error. So are the small trails in the sub due to guide error in RA or Dec, or poor Collimation ? Post the PHD2 guidelog. Michael

Some conflicting results in the GuideLog: Your second of thirteen Cals was proceeding well and Completed, but lost the star at the first East return step: Cal moved west past 25 on the display. However by Cal number 10 the West Calibration became extremely erratic , with RA moving all over the place, in tiny steps. Mostly clustered around only 5 on the scale: And by Cal number 13 the Cal was now more linear but never got past 3 on the scale. And so PHD2 gave up after 60 steps and posted the "Insufficient Movement" message: "I had all the necessary ASCOM drivers" I'm not familiar with the EQ GoTo mount, but perhaps it inly supports ST-4 Guiding ? Guidecam focus was awful HFD = 6.14 px You were Binning the guidecam, so the image scale was a bit extreme Pixel scale = 7.73 arc-sec/px, Binning = 2, "I have uninstalled and reinstalled PHD2" Uninstalling PHD2 looses all your Equipment Profiles and the Dark maps, which you will have to re-enter. You only need to run the Installer again, which overwrites the prog, but keeps the settings. But PHD2 isn't to blame here, the ST-4 connection seems to be very erratic, or you were altering something I'm not aware of. Michael

What mount ? ASCOM or ST-4 guiding ? The Calibration graph suggests that after completing the RA West/East steps, the North steps were in the RA direction. A faulty ST-4 connection that cleared after slewing to M81 ? Michael

Link doesn't work. If you track an object at 0.5x, then images will trail in RA. You should always track at 1x. Unless you mean GUIDING at 0.5x ? Michael

Need to see the GuideLog. "The C8 images (600s, M101) show small star trails (see pic). These become large when the images are stacked (see pic)." Which image is the stack ? The first image seems to have the largest trails ? Neither image shows the increase in quality you'd expect by stacking, are they actually both subs ? Stacking software will usually reject any subs with poor star shapes, so the stacking should fail if all the stars are elongated, or the stack image should have round stars. Which direction, RA or Dec, is the trailing in the 600s image ? Possibly Differential Flexture if the guiding is good - the guidecam has a large overhang, not threaded connections, and a hanging cable. Michael

Is the connection to the mount intermittent ? Is the mount connection showing without errors in Windows Device Manager ? When did PHD2 say that "pulse guiding had stopped", during Calibration, during guiding ? Michael

You have placed the ST102 with the focuser at mid point. And placed the front of the ASI 183MC about 482mm from the ST102 objective. There's probably a large gap between the camera and the end of the focuser. I don't have a ST102 or a ASI 183MC, so it's up to you to work out how to fill that gap. Michael;

Examine the belts for damage, if you fitted them. There are strategies for guiding with backlash. RA can be slightly unbalanced east heavy to take up the backlash. A PA Error will cause Dec to drift either north or south, gentle guiding in the opposite direction can keep Dec at one end of the backlash. If you get PHD2 to Calibrate, following the instructions to clear backlash first, you can run the PHD2 Guide Assistant for a worm period. That will show how the RA worm drive is behaving. Michael

Hi Daz The ST102 has 500mm FL, so the ASI183MC sensor has to be 500mm from the objective lenses. The ASI 183MC has 17.5mm Flange Distance. 500 - 17.5 = 482.5mm Take off the diagonal and put the focuser in mid range. Roughly measure 482mm from the scope objective. That's where the end of the camera's M42 flange needs to be. Measure from there back to the end of the focuser. That's how much spacer you need. Buy the nearest stock spacer, the focuser will take up the difference. Michael

Putting collimation to one side for the moment, look at the star shapes of an in-focus image. Progressively more teardrop-shaped stars toward the edges of the frame are a sign of coma, inherent in the basic SCT design. Michael

I'd say that's due to coma, which is not unusual for an uncorrected SCT. Michael

Yes I did notice that the ZWO ASI 224MC has a tiny 1/3" sensor, so maybe tilt won't be an issue. Michael