Autoguiding - Forums

Topic starter

Jun 17, 2021

I have never really tried to autoguide since I can get up to 3 minutes -and sometimes 5minutes - without autoguiding. I'm wanting to learn this skill but so far success has eluded me. My autoguiding calibration runs often fail and when the succeed, the image shows badly trailed stars; worse than just not autoguiding at all. I'm sure this is all user induced but totally frustrating. I'm trying to use the SkyX-Pro direct guide feature and this is where I'm having problems. So a few questions are in order to find out what I'm doing wrong. I'm currently using a SkyWatcher Esprit 150ED (1050mm FL) with an Orion Short Tube 80 guide scope. Main imaging camera is a ZWO ASI2400MC-pro and the guide camera is a ZWO 183MC

1. What is the accepted technique for choosing what type of autoguiding is appropriate for a particular imaging setup, Off Axis or Guide scope?

2. Is there any accepted rule of thumb for choosing between OAG or Guide scope?

3. What Software programs are the most user friendly but still give excellent autoguiding results. I've heard of PhD but have not used it.

4. Are there any links to tutorials or any other methods or techniques that would help me to acheive success?

Any other information or ideas would be appreciated. Thanks in advance

Patrick G.

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Padraic Moran

Jun 17, 2021

OAGs are usually used for long FL scopes, and especially for SCTs where the mirror can move as the scope tracks.
Guide scopes are used for shorter FLs and where there's no danger of flexure between the imaging scope and the guide scope.

I don't believe there's any magic FL number that marks the cut-off between Long and Short, and the Esprit 150 would fall into that gray area in the middle, but I think most folk would approve of guiding with the ST80 on the E150. Just make sure the ST80 is bolted solidly to the Esprit and doesn't wobble.

Accepted wisdom is that mono cameras are better for guiding as they're more sensitive, but there's no reason why a colour camera won't work.

Phd2 is excellent, and is pretty easy to use. Not sure why your calibrations are failing; there's some very good documentation on the Phd2 website, especially the 'Best Practice' guide. I found that it took a few readings until I got my head around the concepts. Make sure your equipment profile is set up correctly especially the camera pixel size and the guide scope focal length. Other than that, they recommend not changing any of the default settings unless told to do so by the guiding assistant or calibration tools.

It would be good to know what mount you are using. There are a few gotchas with some mounts (settings that need changing) but I haven't had to do any of that with my HEQ5.

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Jesse Holland

Jun 17, 2021

Sounds like possibly some sort of setup error to me. Perhaps polar alignment error, or a setting somewhere that has the wrong hemisphere (north/south)?

Guiding in general is pretty plug and play - especially with PHD2. Like mentioned above, make sure your pixel specs and focal length are set up properly in PHD as well. There are a few in-depth tutorials about it on youtube - that's actually how I learned most of the process.

Concise

normmalin

Jun 17, 2021

Not sure if this will help, but I had all sorts of problems autoguiding through APT and my EQ6-R using a direct USB connection between the mount and the PC. Then I decided to try the most basic setup possible which was to use an ST-4 cable between the guide camera and the mount. So the guiding is happening strictly within PHD2 (via the usb connection from the PC to the guide camera) and not through any other interface along the way. Once I did that, everything worked using the default settings without issue.

The only other thought I have is that you should let PHD2 choose the reference star automatically – don't choose it yourself – the program knows what it is looking for and brightest is not necessarily the best.

Good luck!

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Kevin Morefield

IOTD Staff

Jun 17, 2021

An OAG is preferred regardless of the FL or any situation really unless Backfocus doesn’t allow it. That said, for large image scale setups, a guide scope will work as well.

If your mount allows use of direct guide that is the best option over pulse guide.

I found PHD to be the easiest to get going since it has a lot of Wizard like tools that work with defaults. It’s free so no reason not to try it. I don’t personally use it though because my automation program does work with it. I use TSX and Maxim and both work just as well as PHD, they are just less user friendly.

One other PHD advantage is easy multi-star guiding which can eliminate some of the seeing effects and improve your guide error.

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Patrick Graham

Topic starter

Jun 17, 2021

A lot of great help from all of you. For Padriac, I'm am using a Paramount MX+ with the TSX direct guide option. It's possible that the guide scope is ever so slighty moving as it is secured to dove tail clamps via Losmandy rings that use screws to adjust and secure the scope. I think I'll go with OAG and see if it improves.

Jesse, I believe my PA is spot on. The alignment report generated by my TP Point run shows Excellent alignment and I can go up to 2.5 to 3 minutes without trailing. I'll be going to PhD as well so thanks for the You Tube tutorial recommenations.

Norm and Kevin, Your concenus points to PHD as well so yes, no reason not to try it out. Free is good, too.
As far as the back focus distance, the BF for the main imaging camera is 98mm for the ED 150. If using OAG, should the BF be the same (98mm) or should the distance from the OAG mirror to the sensor equal the distance from the lens component of the fleld flattener to the OAG mirror?

Thanks for all the input and assistance. I'll report back on my success…..or failure!!

CS

Pat G

Ara Jerahian

Jun 18, 2021

Your BF, 98mm, should be the same for the guide cam and primary cam. So, 98mm from FF to guide cam sensor and 98mm from FF to primary cam sensor. These may vary slightly if your primary has a filter in the path.

Also, remember, with an OAG, you will need to disable guiding during any autofocus routine, and the guide cam will be out of focus too (unlike when using a guide scope).

CS,
Ara

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Padraic Moran

Jun 18, 2021 · Edited: Jun 18, 2021

Patrick Graham:
I'm am using a Paramount MX+

Hi Patrick, so no wonder you're getting good 5-minute subs unguided! You should have great success when you get Phd2 running properly.

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Bob Lockwood

Jun 18, 2021

Hi Patrick,

I have tried a half dozen or more guide scope setups making sure everything is mounted as solid as can be, but getting more then 5-10 minutes or so of good tracking was usually it. As soon as I went with an OAG setup, that all went away.

The small group I’m part of are all pretty much high-end users, we all use Astro-Physics mounts, we all use the Sky6 or SkyXpro, but we all use Maxlm dl for camera control and guiding. I know that there is a lot of good free software out there, but I do believe you get what you pay for. You have good scopes, good cameras and one of the best mounts made, you should be able to guide all night with no issues. If your scope and camera will clear the mount and tripod, you shouldn’t need to do a pier flip at all, at least you don’t with AP mounts. Imaging one object from evening to morning is common without ever doing a pier-flip. I know Maxlm is expensive, but it’s probably one of the best, if not the best acquisition/ guiding/ observatory control software out there.

OAG guiding is the best way to go, regardless. Try what you have first using an OAG setup if you can and see what happens, then go from there.

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Kevin Morefield

IOTD Staff

Jun 18, 2021

Patrick Graham:
A lot of great help from all of you. For Padriac, I'm am using a Paramount MX+ with the TSX direct guide option. It's possible that the guide scope is ever so slighty moving as it is secured to dove tail clamps via Losmandy rings that use screws to adjust and secure the scope. I think I'll go with OAG and see if it improves.

Jesse, I believe my PA is spot on. The alignment report generated by my TP Point run shows Excellent alignment and I can go up to 2.5 to 3 minutes without trailing. I'll be going to PhD as well so thanks for the You Tube tutorial recommenations.

Norm and Kevin, Your concenus points to PHD as well so yes, no reason not to try it out. Free is good, too.
As far as the back focus distance, the BF for the main imaging camera is 98mm for the ED 150. If using OAG, should the BF be the same (98mm) or should the distance from the OAG mirror to the sensor equal the distance from the lens component of the fleld flattener to the OAG mirror?

Thanks for all the input and assistance. I'll report back on my success.....or failure!!

CS

Pat G

If you are using an MX+ it should be quite easy to get TSX guiding going. You want to use Direct Guide. Set your aggressiveness at 5 to start, min move to .2" and max move to 2". These can all be adjusted later. The trickiest part really is during calibration. When calibrating, the software looks for the brightest star in the FOV. It then moves the scope 30" or whatever you specify, takes another image and measures the distance and direction of the move. If another, brighter star enters the FOV it will measure the move from the old star to the new star and things will fail. If that happens, move the mount a degree and try again till you get the calibration to stay on the same star through all four directional moves.

Once the calibration is done, you can't rotate the camera unless you are using an autorotator controlled by TSX. If TSX does the rotation it adjusts the calibration automatically. If you rotate the camera independently, the corrections will move the mount in the wrong direction.

I can't think of any other details that are critical. If for some reason you still can't get things working you might include screen shots of your calibration results and any screens that display the problem you are seeing.

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Patrick Graham

Topic starter

Jun 18, 2021

Thanks, Bob for the input. I still have a MaximDL license and had used it only for processing until I discovered Pixnsight. I'll go back and try it as well for autoguiding. So many options, I'll just have to experiment with each.

Kevin, I'll try the settings you suggest as well. The explanation of TSX acquiring a different bright star makes sense. I didn't know that could happen. Anyway, I'll keep at it until something works. Thanks for your input.

Clear Skies to all,

Pat

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Dale Penkala

Jun 18, 2021

I’m far from an expert on this but its been my experience using PHD2 that you don’t want to use PEC with it. I’ve found that PEC interferes with PHD2 and causes issues so leave PEC off if you give PHD2 a try. Keep in mind I’m using OnStep and SharpCap with my setup.

Dale

Patrick Graham

Topic starter

Jun 21, 2021

Update: It's strange that PHD could not distinguish between my ZWO guide camera and my ZWO imaging camera. In settings, it did not show a selection for choice of camera models. So, back to TSX. Instead of "direct guide" I was finally able to get a successful calibration and successful autoguiding using the ST-4 cable from camera to mount and using "relay" from the options menu on the autoguide tab. Autoguiding was accurate up to 10 minutes which is the best I've ever done. Thanks to everyone for all the assistance.

CS

Patrick

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Dale Penkala

Jun 21, 2021

Patrick Graham:
Update: It's strange that PHD could not distinguish between my ZWO guide camera and my ZWO imaging camera. In settings, it did not show a selection for choice of camera models. So, back to TSX. Instead of "direct guide" I was finally able to get a successful calibration and successful autoguiding using the ST-4 cable from camera to mount and using "relay" from the options menu on the autoguide tab. Autoguiding was accurate up to 10 minutes which is the best I've ever done. Thanks to everyone for all the assistance.

CS

Patrick

Hello Patrick,
Glad you were able to get your guiding working with your setup!
In PHD2 you setup your camera’s with the ASCOM camera 1 and camera 2 then it will distinguish the individual camera models. I had that problem at first as well using the ZWO drivers. Once I switched over to the ASCOM setup everything worked out like a charm.

Best of luck to you!

Dale

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Patrick Graham

Topic starter

Jun 21, 2021

I'm a big proponent of "if it works, don't fix it" but I'd like to get PHD to work since it has some features that TSX doesn't offer. I'll look for those ASCOM settings. Thanks, Dale.

Patrick

Dale Penkala

Jun 21, 2021

Patrick Graham:
I'm a big proponent of "if it works, don't fix it" but I'd like to get PHD to work since it has some features that TSX doesn't offer. I'll look for those ASCOM settings. Thanks, Dale.

Patrick

Welcome Patrick, yes I totally get that myself! My dad always said don’t kick a sleeping dog!

Best of luck!

Dale

Kevin Morefield

IOTD Staff

Jun 21, 2021

Patrick,

Glad to hear it is working for you! One thing though - Direct Guide should be more accurate than using the ST4 cable and is preferred with a high quality mount like the MX+. I'm curious, did you unplug the ST4 cable when you were trying Direct Guide? If not, you should try that.

Direct guide works by speeding up or slowing down the worm to make the adjustment. Using the ST4 cable will send "bumps" to the mount and is less refined.

Kevin

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Patrick Graham

Topic starter

Jun 21, 2021

Kevin, When attempting with direct guide, I had no ST-4 cable attached. So I don't know why the ST works and direct guide doesn't. I'll continue to troubleshoot it as I would like to use the feature for the reasons you stated. I've tried everything from the minimum recommended to ridiculously long calibration times and movements up to 50 arc-seconds. I'll go back and start with your recommendations again. Maybe I had something entered incorrectlly.

CS

Patrick G.