michael8554

You should expect RA and Dec to drift during the Guide Assistant run, because guiding of both axis is turned off. The Dec drift is due to PA error, 5arcmins is fine, 5.1 has just gone over the PHD2 threshold of acceptable. RA drift is due to Periodic Error, every mount has some, even with PEC. A smooth line is good, variance would indicate the mount is wobbling on its own with the drives off. Michael

Given the amount of mirror flop in the average SCT, how consistent were the dot positions as you altered focus and then refocused ? Michael

Is that a single sub or a stack ? I see elongation in the same direction everywhere in your image. Guide Error ? Take a single short exposure to eliminate this, and stretch it to brighten the stars. Michael

You installed the ASCOM 6.5 Platform, but did you go on to install the ASCOM driver? From the Meade LPI-G "Quick Start Guide: "To install the ASCOM drivers, first install the "ASCOM Platform" by clicking on the "ASCOM Platform" button found on the CD-ROM startup screen and follow the on-screen instructions. After the ASCOM platform is installed, install the ASCOM Camera Drivers by clicking on the "ASCOM Camera Driver" button found on the CD-ROM startup screen. Follow the on-screen instructions to complete the installation" Michael

So why don't you try copying those SkyCapture > X64 > Meadecam files into Program Files (X86) > SharpCap 3.2 ? Michael

You might need to move the LPI-G ASCOM driver into one of the SharpCap folders - read the help files. Michael

Without even looking at your GuideLog, I know realise the huge blob in your Saturday image is not a globular cluster, but an out-of-focus star, and what I thought were the stars are hot pixels. So you have not "fixed the problem", the focus is still way out. Take off the guidecam and focus the sun onto a flat surface. Roughly measure from the back of the scope to that point. That's where the ZWO sensor has to be located, it's 8.5mm inside the front of the camera with no adapters mounted, Michael

I couldn't find redetails of a Skywatcher 0.9 Reducer, I could find a Skywatcher 0.9 Coma Corrector. To my eyes the bottom-half of the image isn't too bad, the top-half has noticeable Coma. Suggesting tilt - either through the connections to the focuser, or the sensor after the Mod. I believe that a Nikon with a T2-Adapter, and a Canon with a T2-Adapter, are both 55mm spacing from the T2 thread. So if the coma is fine with the Nikon, and if you are using the same connections, sounds like sensor tilt. But try with the CC unscrewed slightly, to give you a mm or so extra spacing. Michael

Post a jpg of a problem sub. Specify which OTA and CC. Michael

My take on the message was that this behaviour was while Tracking? Which makes Guiding difficult. Could be wrong...... Michael

The latest image that actually shows the elongation: Depending on which corner it's from, the camera could be too close, or too far away, from the FF. Or it could be guide errors if the whole frame is the same. Who knows. Michael

Found this on the PHD2 Help Forum. Although it relates to a CEM40EC, the problem is probably the same for the 60EC: "I struggled to guide a CEM40EC for quite a while before learning that iOptron EC mounts suffer from "sub-divisional error" on the encoders. In my CEM40EC, this resulted in the mount oscillating in RA with a 6-second period and a peak-to-peak amplitude of 0.6 arc seconds. There was no way to guide this out. The best I could do was use a long interval (3 or 6s) to try to average out the wobble so it didn't inject noise into the guiding. Eventually, I bought a CEM60 (no EC) and sold the CEM40EC to someone who was imaging at a larger scale." Michael

The image scale is 6.55"/pixel To dither the 100D by the commonly used 12 pixels, the mount needs to move 12 x 6.55 = 78.6 arcsecs. So does a pulse of 0.5ms, or 10, achieve that ? Michael

The info in your screen grab is limited. Despite a 3 second exposure, Signal to Noise SNR is only 4.0, the yellow figure in the toolbar indicates it's of concern to PHD2. If you move the blue slider to the left the display would show the stars better. And if you displayed the Star Profile (Tools - Star Profile) we could maybe tell if that's a hot pixel or not. (Though you are using the PHD2 Darks) "Cal" on the toolbar is red, indicating either that the Calibration failed, or maybe you haven't tried yet - you did press the green button to make PHD2 Cal, and then guide ? Post your PHD2 GuideLog, such as it is, so we can check your settings. Michael

Newer versions of the 4400 have a 1.25" focuser. Maybe the 0.965" part of your focuser unscrews, to reveal a 1.25" fitting ? An image would help. Michael

Which of those two images was that from, I still don't see it in the originals ? Square, but not elongated. Michael

PHD2 / Tools / Enable Server Michael

Yes, the RA and Dec lines should be at right angles, and the circles evenly spaced. The circles indicate the distance between PHD2 Calibration Steps. If the pixel size and focal length have been correctly entered, there should be about 12 circles. PHD2 will then know how far an X ms pulse moves your mount. The bunched-up red dots at the origin shows there is Dec Backlash, which you should manually clear before Calibration. There is a wealth of Help And How To guides available via the PHD2 Help menu, start with this: https://openphdguiding.org/phd2-best-practices/ Michael

The corner stars in the images you posted look fine to me Michael

The 1600MM sensor is over twice as large as the 178MM, so it's edges are much closer to the vignetted regions of the ED102. Michael

Hi Steve There are other examples of the RA problem. Here's part of your Calibration: Note how the RA steps (blue) are bunched together in pairs, instead of being evenly spaced like Dec. So there might be slight stiction that is taking two pulses to overcome. From other posts I've read it's likely your 120 sec problem is something in the belt drive. Try shifting the belt a couple of teeth on the cogs. Try swapping RA and Dec belts if they're the same. Look for signs of trying to jump while slowly slewing. Michael

My comments are based on my PHD2 experience, I'm assuming a good Cal with your software should look like this, with RA and Dec at 90 degrees: And the Dec Backlash causes the southward return from the northmost end of the Dec line to wander off like your S1 to S7, instead of retracing the green line to the origin. But again, your software may Calibrate differently. Michael

From what I've read, keeping the ISS in FOV is challenging, so the much larger FOV of the DSLR will help. Not sure you'll capture more than a dot the with the FL of the ED80, could be wrong. Michael

Try this OAG Calculator to match camera size to prism size: https://www.smallstarspot.com/oagcalc.html Michael

Hi Shimonu Here's from YOUR GuideLog: You never got a decent Calibration, so guiding was bound to be poor: Calibration guide speeds: RA = 1.6 a-s/s, Dec = 1.7 a-s/s Guide speeds need to be at least 7.5 a-s/s. So RA completed in 4 steps W1 to W4. PHD2 aims for 12 steps, your Guide software may be different. North took 3 steps N1 to N3, but the Return South path S1 to S7 should have ended back at the intersection of the axis at W1, and ideally taken 3 steps, not 7. This is an indication of rather large Dec Backlash,. So I'd concentrate on that rather than RA ! I'm afraid the Logs generated by your Guide Software are sparse on detail compared to PHD2. But it showed that you Calibrated at Dec = 40, it's best to Calibrate at Dec = 0. So concentrate on Dec Backlash and larger Guide Rates. Maybe get some good guiding by tweaking in PHD2, then reverse engineer it to work with your guide software 😆 ?? Michael