Quick guiding scope question for you veterans

[Catanonia]

As some of you may be aware, I have been having loads of guiding problems with my PL130m OpticStar guide camera.

I popped along to the shop today and explained my issues and had the camera tested and it appears to work fine. However I was told that I was trying expect to guide onto stars that are too faint. Mag 8 or greater where the limit of the CCD is mag 8.

Now I do this via a Skywatcher ED80 which is STATICALLY piggybacked onto the main ED120 imaging scope.

So i have 2 choices.

1. Increase my FOV by swapping out the ED80 or using a field reducer.

2. Moving the ED80 guide scope independantly of the imaging scope to find a brighter star.

When I get a bright star in the area of where I am imaging in the FOV of the ED80 everything works perfect. The problem is that not many of the areas I go to have stars bright enough below mag 8.

So how many of you actually have your guide scopes setup with guide rings that allow alignment with 3 screws as it seems this is what I need to do?

Find a guide star and not expect one to be in the FOV as the ones that are are too faint.

Where can I buy some cheap adjustable guide rings for an ED80 ?

Am I correct in my 2 options ?

[barkis]

Arthur (Millamber)was selling some rings cheap He may have sold them all, but you can ask him.

Most imagers have the guidescopes in rings.

Ron.

[jgs001]

I've only been using fixed rings till, Arthur posted his offer. He has a lot of rings that he is willing to make up, 10 was the minimum... his thread is in the Retailers offers, might be worth getting over there quick.

[Psychobilly]

Have guide rings but never had to offset the guidescope from the imaging scope.... buy a set of rings of Arthur... and ditch that so called guidecam...

Peter...

[kev 102 42]

Arthur is selling excellent guide rings for 30 bucks ,get yer self a pair before their sold out....................kev

[Catanonia]

cheers guys, added myself to the list for Arthur and sent him a PM

[RobH]

I used to use guide rings, but now don't due to occasional problems with flexure, even with them clamped down hard using molegrips.

I now have normal tuberings.

My guidecam is a Meade DSI pro mk1, and I never have any trouble at all finding a guidestar.

Get yourself a decent guidecam and your worries will be over

Cheers

Rob

[Whippy]

I don't use guide rings either when I'm guiding with either scope and my FLT98 would give a similar FOV like your ED80.

Have to say that if a camera's limit of sensitivity is magnitude 8, then that's not going to make a great guide cam regardless if you have guiderings or not. The naked eye (under perfect skies) can detect stars down to mag 6!

Tony..

[beamer3.6m]

Hi.

You could make your own guide rings very easily.

You can just drill 3 holes into a set of skywatcher scope rings which are larger than your scope. I would suggest the rings for the 130p would be ideal. then screw into them long screws and you are done.

Do think your cam needs to be more sensitive though have you thought about the qhy5.

[beamish]

I'm with Rob here-I have the possibility of independently moving the guide scope but prefer to have it static and co-aligned with the main scope. Get a proper guidecam and use the one you've got specifically for lunar imaging !

[minimalist]

I'm with Rob also, have my guidescope coaligned with the imaging scope and a dsi pro mk1 as the guidecam. With 1sec exposures I've never failed to find a guide star. My suggestions are similar:

1) get a more sensitive cam. Btw, when you mention mag 8 as the limit, is it an exposure issue? Usually, with longer exposures you can go pretty deep.

2) Guide rings. This will work, but if you don't take care of 1) then you may have to offset the guidescope so much on some targets due to lack of bright stars that you will suffer from field rotation.

3) Faster scope. I image at roughly three times the focal length of my guidescope with no issues. You can get a faster scope (like one of those nice 66mm jobbies) and still guide well I think.

[barkis]

TJ Uses an Off Axis Guider to good effect, and no flexure Issues.

No guide scope needed of course, but guide star choice may be limited around certain targets, but TJ himself would have to elaborate on that.

Ron.

[Catanonia]

I am going to try the trail versions of Maxim and AstroArt to see if they make a difference over PHD. Apparently they are more precise and give much better results.

If these do not work, then the cam goes back and I get a QHY5.

BTW : ScopeGuides on the way . Nice to have anyways and thanxs for the heads up. Just in the nick of time

Cat

[RobH]

PHD works perfectly for most who use it, and in a survey was found to be used by over 50% of imagers using guiding software.

I can happily guide for at least 30 minutes accurately with it, probably a lot more.

Where did you hear that it wasn't accurate?

I have heard that, with DSI's at least, where PHD will have no trouble finding a guide star, Maxim can sometimes struggle.

I have Maxim, and use it for all my data gathering, but haven't felt the need to change from PHD as it works perfectly, is really easy, and if it aint broke, don't fix it!

Cheers

Rob

[Catanonia]

PHD works perfectly for most who use it, and in a survey was found to be used by over 50% of imagers using guiding software.

I can happily guide for at least 30 minutes accurately with it, probably a lot more.

Where did you hear that it wasn't accurate?

I have heard that, with DSI's at least, where PHD will have no trouble finding a guide star, Maxim can sometimes struggle.

I have Maxim, and use it for all my data gathering, but haven't felt the need to change from PHD as it works perfectly, is really easy, and if it aint broke, don't fix it!

Cheers

Rob

good to know, well going to try out Astro and Maxim and see if any difference before I ditch the PL 130m. Both downloaded and installed now ready for a clear night.

[LaVey]

I just got the QHY5 and can rate it.. not had a problem getting a star on the two occasions I've had it out so far...

[RobH]

Good to hear LaVey

Is PHD working OK for you now?

Cheers

Rob

[Catanonia]

I think it is something to do with the binning mode support that AstroArt and MaximDL offer with the PL 130M driver that PHD does not offer as OpticStar did not write the driver for PHD as they did with the others.

That was from an email i recieved.

Hence this drastically reduces the sensitivity down by a possible factor of 16 with PHD with this CCD.

Will soon find out when get some clear skies.

Cat

[Beyond_Vision]

As Rob says changing the software won't make any difference. The camera is most likely the cause of your problems. A second hand Meade DSI camera would be better and would probably be cheaper than the PL130M and QHY5.

[ollypenrice]

If you grab yourself an Atik 16ic, new or used, and a fairly fast guidescope, you won't need to move your guidescope in rings. At least that has been my experience, though no doubt a bit of sky somewhere is waiting to get me! Guiding seems to be quite an issue so I prefer to make life easy for myself with a bit of overkill as far as the 16ic goes. Highly recommended.

Olly.

[roundycat]

I also use the 16IC (with Maxim) and find it excellent. As Olly says, go for the best solution and let others have the problems. I also believe that moving the guidescope in its rings will not cause field rotation. That is caused by poor polar alignment, nothing else.

Your original question said that someone in the shop told you that mag8 would be about the best the camera could manage. Did they suggest anything about varying the exposure length. Mag8 seems ridiculously bright. Exposures in the 4-6 second range should also ensure you are not chasing the seeing.

Dennis

[Catanonia]

I also use the 16IC (with Maxim) and find it excellent. As Olly says, go for the best solution and let others have the problems. I also believe that moving the guidescope in its rings will not cause field rotation. That is caused by poor polar alignment, nothing else.

Your original question said that someone in the shop told you that mag8 would be about the best the camera could manage. Did they suggest anything about varying the exposure length. Mag8 seems ridiculously bright. Exposures in the 4-6 second range should also ensure you are not chasing the seeing.

Dennis

What i got in an email.

For example if you use an 80mm aperture scope with the PL130M and PHD your guide scope will see/guide on up to 8th magnitude stars, a bit higher under good conditions.

If you use the same 80mm aperture scope with the PL130M and MaximDL or Astroart for example your guide scope will see/uide on up to 11th magnitude stars.

Apparently now it seems that PHD has a problem with this camera and I am guessing they knew about it all along. This is with exposure lengths of 4 seconds. There was another thread somewhere where someone actually measured the PL130M exposure time and it was nowhere near the claimed 10 seconds and hence the advice to use a max of 4 seconds.

If i knew that to make this camera work I would have to spend £100 on AstroArt or even more on Maxim, then I would not have taken it. If this is the case, as my tests might show next dark night, then I will let people know so they are not caught out as well.

Already spoken to another SGL member on the phone who has exactly the same problem as me.

I have agreed with them that the camera will be returned when I have a replacement sourced, in the meantime I will test this with Maxim and AstroArt to see what happens and hopefully help others.

[minimalist]

Ahh, I see, the binning mode would definitely help, but it would also cut your sensor resolution in half. That may or may not hurt your guiding.

Dennis, I could be wrong, but several threads I read mentioned that effect. Here's one such thread, makes sense to me but again, I could be wrong.

Telescope Reviews: Re: How Far "Off Axis" Can Your Guide Scope Be?

[roundycat]

with my Atik unbinned guiding is often a bit jumpy, as soon as I set it to x2 guiding improves. Possibly this is due to the centroiding algorithm having a better chance with a star that is effectively oversampled. Sometimes defocusing helps as well.

The argument about aligning main and guide scopes is, I think, only relevant in Dec. If you misalign in RA there is no problem. Hence you can swing the guide scope from side to side to search for a guide star but if it really is a problem finding one then a reducer is probably the best bet. In spite of having less than optimum polar alignment from time to time I have never seen field rotation. I rarely go for longer subs than 15m due to sat trails etc so this may be part of the reason. I think many people go for the longest sub they can get as a sort of 'macho' approach to imaging.

Time is not what you should be looking at but the background noise in the image and the degree to which the good signal is above the read noise. Once you have swamped the read noise you are good to start another sub exposure. More subs, provided you dither between exposures and use an outlier rejection method for combining, mean cleaner master channels.

Dennis

[MikeP]

If you do a search, you'll see I had problems with a PL130 too. The Opticstar people were very helpful and willingly refunded my money once I'd tried all avenues.

Sorry to say it but I agree with the others, get rid of the PL130.

I was able to borrow a DSI and it is so sensitive by comparison, that not only was there no problem in finding guide stars, pointing it at M31 (for fun) revealed dust lanes with hardly any exposure time at all. I now have a DSI.

Mike