Guiding help

Hi John,

It looks like you have an Askar 120 on an EQ6 mount with external guide scope and camera. My guess is something was changed with guide settings rather than the new monochrome camera. Perhaps something is different from when you went from OAG back to the external guide scope. First thing is check all the settings to make sure they correspond to your current setup. The other obvious troubleshooting approach is to go back to the setup that worked previously and see if you still have the problem. My guess is you will, which will take you back to something having changed with the guide setup rather than new equipment.

Others will be asking for current guide settings and logs so you could probably prepare in anticipation. This is everyone’s nightmare and I’ll look forward to seeing how things go. Any problems I’ve had in the past have been user error.

Hi John

Do you have cooling on with your new camera when you see the problem? You might want to check if you are getting fan vibration on your new ZWO camera. Even new fans can cause serious vibrations—which your guiding cannot compensate for. Turn off cooling on the ZWO camera, which shuts off the fan, and see if the guide problem goes away. If this is the problem, the solution is to buy a silent fan to replace the ZWO fan. Details are here in a thread I started recently.

Rick

https://app.astrobin.com/forum/topic/203317/zwo-asi2600mc-pro/mysterious-star-trailing-solved-a-cautionary-tale-of-fan-vibration-with-a-fan-cooled-especially-zwo-camera?page=2#post-218369

Paul Larkin · Nov 28, 2025 at 07:43 AM

Hi, John.

A couple of thoughts that might help (or fuel some speculation and further discussion):

• If the guide camera is on a separate scope, I can’t see how the 2600MM can be a factor. Something else must have changed as well.

• PHD2 guiding can go wrong with incorrect parameters , such as focal length of scope used for guiding, camera pixel size etc. Been there done that. The wizard for setting up new profiles works well to sort this.

• …also, I have had previously good profiles not guide well and simply re-doing the wizard with the same gear and their parameteres got it working. Go figure.

• I do a guiding calibration ahead of every imaging run after I do framing, because any rotation in the guide camera will completely mess any previous calibration. This is primarily with an OAG, since rotating the imaging camera also rotates the guide camera. But any movement in a separate guide camera/scope setup will also require recalibration. Your comment about “…put it together and take it apart every night…” suggest that this may be a possible contributor to this, unless of course you are doing a PHD2 calibration each night as well.

• Mechanical factors, such as tripod stability (my EQ6R is rock solid, and I imagine yours is too); wind. A bit obvious but worth a mention.

• Someone else can help with a an explanation for the fact that one gets better/worse guiding when the target is closer to the poles (or closer to the equatorial plane). I can’t remember precisely whcih is better but I think this is another contributor to variability in guiding results.

I hope that helps a bit. No doubt others will chime in.

Chees.

Paul

I do recalibrate every session or whenever something changes, even a meridian flip because it get wonky if i dont. I guess the one thing i havent tried is creating a new wizard completely. Ive just been using the original one i made a couple years ago that had all the guiding inputs of my guide scope and camera. This i can hopefully do soon.

John Nelson · Nov 28, 2025, 03:56 PM

Rick Veregin · Nov 28, 2025 at 02:44 PM

Hi John

Do you have cooling on with your new camera when you see the problem? You might want to check if you are getting fan vibration on your new ZWO camera. Even new fans can cause serious vibrations—which your guiding cannot compensate for. Turn off cooling on the ZWO camera, which shuts off the fan, and see if the guide problem goes away. If this is the problem, the solution is to buy a silent fan to replace the ZWO fan. Details are here in a thread I started recently.

Rick

https://app.astrobin.com/forum/topic/203317/zwo-asi2600mc-pro/mysterious-star-trailing-solved-a-cautionary-tale-of-fan-vibration-with-a-fan-cooled-especially-zwo-camera?page=2#post-218369

This i havent tried yet. I can test it next time i go out but that would be extremely disappointing if thats the case. I dont really want to take the new camera apart and mess with it. I keep it cool at -10 degrees, and it never goes past like 30% power. Ill check any and see if it helps, if it does are there any other ways to fix it?

Fortunately, it is easy enough to do and the fan is cheap, just remove four screws on the backplate and the fan comes off with the back plate. You can try just replacing the screws that hold the fan with rubber posts if you don’t want to replace the fan, did not work for me, but worked for others. See the thread I mentioned for what has been tried and what worked. Getting ZWO to replace the fan may not work, I tried a new ZWO fan and it was just as bad. Unfortunately the ZWO fan runs even at 30%, or 20% or 10%. I was only cooling to 0C and it was cold outside, and I still had the issue. You won’t believe how quiet the camera is with a low vibration silent fan, compared to the ZWO.

All the best

Rick

lunohodov · Nov 28, 2025 at 06:05 PM

John,

Calibration is only necessary when specific factors change, such as guiding camera rotation. Don’t re-calibrate, use the Guiding Assistant (under Tools) to adjust the guiding parameters to the current conditions. Additionally, refer to the PHD2 Best Practices document for further insights.

I may be stating the obvious, but guiding cannot deteriorate without a valid reason. Consider what has changed in the system and eliminate the reasons systematically. Fan vibration, as Rick mentioned, can be problematic and is definitely worth investigating. However, examining the corrections graph, I’m skeptical about it—the RA oscillations are more pronounced. Perhaps you also changed the camera cables?

I hope you identify the culprit. Please keep us updated.

Clear skies.

I did in fact change the cables. I got shorter ones that dont sag off the side and they all plug in the the apertura armored power box. I believe that they are high quality cables but i could be wrong.

Hi, John.

I second Rick’s fan fix. I forgot (and therefore forgot to mention) that I had elongated stars in my images and after reading others’ experiences in Cloudy Nights, I replaced the fan in my 2600MM and my guiding and images magically improved. Thus, the introduction of the 2600MM could indeed be the problem.

I did some tests with the fan off and fan on all within a 30min or so window (so that the setup is pointing at the same angle - I chose Zenith to reduce the likelihood of other factors such as mirror flop - I had a Celestron EdgeHD 8” on my EQ6R.). I did each a couple of times and then checked images (elongated stars with fan on; round stars with fan off - examples below). This is what confirmed the fan hypothesis for me (it costs nothing but some time). I bought the Fractal 50mm fan from Amazon. Problem fixed. Some folks suggested putting in rubber bushes to dampen vibration, but this made no difference for me - just the fan change did it all. It’s easy to do.

Cheers.

Paul

300s Ha (Fan On)

📷 image.png

300s Ha (Fan Off)

📷 image.png

📷 M 42 HA 4 hours Combined-2.jpgIt is still too early to tell because the conditions yesterday were terrible, but I think I found the solution. I tried many things and monitored the camera’s fan vibrations, but the one that worked (I believe) was creating a new wizard entirely. I don’t understand why it worked so well because I didn’t change the previous one for almost two years. Even with last nights 25 mph gusts of winds, During the lulls the guiding stayed steady at .55 to .80. Which is great. I may fine tune a little more but I didn’t really see and outstanding errors in RA like I did the night before. Knock on wood that it stays this way. My only gripe was that the wind made it difficult to tell how consistent it was. Thank you all for your words of wisdom, and here is what I got with the new wizard.

Sorry I’m a little late to this conversation. I’m glad you got some things figured out, but I do believe your performance even still is quite lacking and could be alot better.

The one thing that stands out to me off the bat is you said you have an OAG but you chose to use the guide scope. Looking at your pixel scale in PHD2, I’m seeing you have a guide scale of around 3 arc seconds per pixel. Given your focal length, I’d say you’re not properly sampling for guiding. Sure, PHD2 can sample down into the fractions of pixels, but your guide scope is just too small to really sample that accuracy in the first place. I highly recommend getting that OAG installed and figuring things out. You will thank yourself later.

The things that I see that can easily be fixed and improved:

Based on the screenshot you sent above, your guiding is fighting periodic error. Without PEC trained on mount, the EQ6 has something like 16 arc seconds of periodic error. Training PEC will help bring that down drastically, which makes PHD2 work less.
Bring your update speeds up to 1 second, instead of the 2 second you are currently using. In my experience, 2 second updates are only for moments of poor seeing and really only if you have PEC trained. Reason being is 2 second updates cannot keep up with the periodic error of the mount, and it will drift quite a bit between updates.

Try using PPEC algo in PHD2. If you’re not planning on doing PEC training, PPEC will achieve the same thing, but utilizing software. Just make sure you manually set your worm period, PHD tends to not predict it accurately.



Another valid reason for getting rid of the guide scope in favor of the OAG is to rule out any flexure. Honestly, if you have the OAG, it seems silly to me not to run it. I’d really go back to it, if I were you. If you have any questions, feel free to ask. I’ve gotten pretty good at dialing in EQ6’s, I’ve helped alot of folks.


To give you an idea of what you’re missing out on… here’s my EQ6 running with an Esprit 150 on it. It’s running extremely well and certainly pushing it’s capacity.

📷 image-1.png

Brian Puhl · Nov 30, 2025 at 08:09 PM

Sorry I’m a little late to this conversation. I’m glad you got some things figured out, but I do believe your performance even still is quite lacking and could be alot better.

The one thing that stands out to me off the bat is you said you have an OAG but you chose to use the guide scope. Looking at your pixel scale in PHD2, I’m seeing you have a guide scale of around 3 arc seconds per pixel. Given your focal length, I’d say you’re not properly sampling for guiding. Sure, PHD2 can sample down into the fractions of pixels, but your guide scope is just too small to really sample that accuracy in the first place. I highly recommend getting that OAG installed and figuring things out. You will thank yourself later.

The things that I see that can easily be fixed and improved:

Based on the screenshot you sent above, your guiding is fighting periodic error. Without PEC trained on mount, the EQ6 has something like 16 arc seconds of periodic error. Training PEC will help bring that down drastically, which makes PHD2 work less.
Bring your update speeds up to 1 second, instead of the 2 second you are currently using. In my experience, 2 second updates are only for moments of poor seeing and really only if you have PEC trained. Reason being is 2 second updates cannot keep up with the periodic error of the mount, and it will drift quite a bit between updates.

Try using PPEC algo in PHD2. If you’re not planning on doing PEC training, PPEC will achieve the same thing, but utilizing software. Just make sure you manually set your worm period, PHD tends to not predict it accurately.



Another valid reason for getting rid of the guide scope in favor of the OAG is to rule out any flexure. Honestly, if you have the OAG, it seems silly to me not to run it. I’d really go back to it, if I were you. If you have any questions, feel free to ask. I’ve gotten pretty good at dialing in EQ6’s, I’ve helped alot of folks.


To give you an idea of what you’re missing out on… here’s my EQ6 running with an Esprit 150 on it. It’s running extremely well and certainly pushing it’s capacity.

📷 image-1.png

The reason i put it away was that the star would fly off the cross and phd2 would overcorrect drastically. I know its better but i just didnt want to mess with it and at least get some pictures sic e the camera was so new. Im past that point now so i will try again soon. Thanks for the info though, ill come back to this when i get the oag set up for real.

John Nelson · Dec 1, 2025, 01:51 AM

Brian Puhl · Nov 30, 2025 at 08:09 PM

Sorry I’m a little late to this conversation. I’m glad you got some things figured out, but I do believe your performance even still is quite lacking and could be alot better.

The one thing that stands out to me off the bat is you said you have an OAG but you chose to use the guide scope. Looking at your pixel scale in PHD2, I’m seeing you have a guide scale of around 3 arc seconds per pixel. Given your focal length, I’d say you’re not properly sampling for guiding. Sure, PHD2 can sample down into the fractions of pixels, but your guide scope is just too small to really sample that accuracy in the first place. I highly recommend getting that OAG installed and figuring things out. You will thank yourself later.

The things that I see that can easily be fixed and improved:

Based on the screenshot you sent above, your guiding is fighting periodic error. Without PEC trained on mount, the EQ6 has something like 16 arc seconds of periodic error. Training PEC will help bring that down drastically, which makes PHD2 work less.
Bring your update speeds up to 1 second, instead of the 2 second you are currently using. In my experience, 2 second updates are only for moments of poor seeing and really only if you have PEC trained. Reason being is 2 second updates cannot keep up with the periodic error of the mount, and it will drift quite a bit between updates.

Try using PPEC algo in PHD2. If you’re not planning on doing PEC training, PPEC will achieve the same thing, but utilizing software. Just make sure you manually set your worm period, PHD tends to not predict it accurately.



Another valid reason for getting rid of the guide scope in favor of the OAG is to rule out any flexure. Honestly, if you have the OAG, it seems silly to me not to run it. I’d really go back to it, if I were you. If you have any questions, feel free to ask. I’ve gotten pretty good at dialing in EQ6’s, I’ve helped alot of folks.


To give you an idea of what you’re missing out on… here’s my EQ6 running with an Esprit 150 on it. It’s running extremely well and certainly pushing it’s capacity.

📷 image-1.png

The reason i put it away was that the star would fly off the cross and phd2 would overcorrect drastically. I know its better but i just didnt want to mess with it and at least get some pictures sic e the camera was so new. Im past that point now so i will try again soon. Thanks for the info though, ill come back to this when i get the oag set up for real.

This is because you didnt have your focal lengths and step sizes set correctly. Just like you said above, you have to start from scratch, with a new wizard.

A couple of things that I see are:

1. You appear to be using single star guiding, instead of the later Multi Star guiding available in PHD2. Cuiv can explain it better than I. https://youtu.be/wDCEjwQNmTE?si=GMfaFE3l9yDhemC3

   I got to try Multi Star Guiding about a week before the release, and I’ve never looked back. Usually for me I get 9 stars in Multi Star window, I’ve seen where there are 12 available. But I’ve only seen 9 in mine. On occasion when clouds appear some of the guide stars will disappear, then reappear.

2. I use Sharp cap for Polar Aligning, have for years now. I use it alone and nothing else from Sharp Cap because it is worth the fees in itself, to me. I used to wonder about using my individual guiding scope by itself for my guiding. I finally gave it a try recently and found it reduced my PHD2 graph from 0.5-0.8 to typically 0.2-0.5. So, I’m sold on using my Svbony 106 guide scope 60mm, and ASI290MM camera as my guiding system for my equipment. It simply works better than using my Main Scope with PHD2.

   I’d recommend to anybody using a separate Guide Scope and Camera to at least try using them for Polar Aligning.

   Sometimes when doing maintenance on my mount, I might have to twiddle the gear lash a little to get it satisfactory (Best numbers). But too tight is detrimental as much as too loose (gear lash). So, when mine is running nice low numbers, I prefer to let it be. And even if it is waggling, I leave it alone. Seeing changes a lot, and it will affect your guiding. Once I’m on a target I tend to ignore my guiding and pay more attention to the images. If they look good, they usually will stack good.

3. The goal is to try and get the least deflection for whatever mount you are using. As far as the mechanics go, some of it is trial and error, error, error. A lot of tweak and try.

4. You might try reducing your RA and DEC aggression levels from 100 to say, try 70. But do one at a time, and watch your graph. You’re trying to tweak things in, not jump canyons. I’ve been using PHD since PHD1. And it was a nightmare figuring it out back then. But so was my equipment.

   You’ll get there, just keep swimming. <LINK<