Mac + Skywatcher ST150 on EQ5: best solution to autoguide?

[rofus]

Hi all,

I'm upgrading to a ST150 from a ST102 (with 2" Semi Apo filter and 2" connections), on a Skywatcher EQ5 Deluxe Synscan Goto. I use a Nikon D90 at prime focus for astrophoto, obtaining usually up to 2 minutes non guided. I use a Mac (no Windows).

I'd like now to upgrade and try autoguiding with PHD. I have two questions:

1) Which webcam/ccd to use compatibile with Mac/PHD?

2) Considering also the mount and the telescope weight (10kg), what's the best solution for guiding?

      a) Finderscope 9x50

      Off Axis Guider

      c) William Optics Zenithstar 66 ED Pletzval as guide scope (isn't it too much for the mount I have?)

Any help about the best solution to start with would be appreciated, I'm obviously on a budget so I need to find a starting solution that will grant me maybe 4/5 minutes exposure, that considering short focal lenght of the ST150 (750mm) could be maybe achievable without too much fuss?

Thanks

[wuthton]

The ST150 is a lot of telescope for an Eq5. Would you not be better off with a good quality 80mm (ED80/Equinox 80) with your ZS66 piggybacked? This would be well within the capabilities of your mount.

[AstroGZ]

I would use the 9x50 finder method, should keep the weight down but still allow you to find plenty of guide stars. I have never used an OAG so can't comment! One of the most commonly used guide cameras is the QHY5, but I don't know if it is Mac compatible.

[rofus]

Reading around I understood that the ST150 is just about right on an EQ5 Deluxe, indeed it was sold also with that mount. I just tested it quickly and with the 2 inch diagonal and a heavy Baader ocular seems perfectly balanced in all directions after positioning correctly the tube and the one big weight at the end of his axe. The weigth of my D90 is even lighter than the one of the diagonal+baader, should be good. If anything it feels more 'robust' assembly.

Obviously in this situation I'd not add a piggyback guidescope, I'd rather guide with a finderscope. About the good ED80 I agree that would be an option, but I do mostly DSO (visual and imaging) and such aperture is not tradable with an 80 even if APO. When I bought the WO66 I was following a similar suggestion, but I ended up leaving the 66 taking dust or used as portable/holiday one, because compared with larger apertures (first a 150 reflector, then the ST102 refractor) it just cannot compare imho. I also noticed that an average ED can be compared to an achro with semi apo baader filter, even if not on big enlargements and very bright objects (not my interest anyway).

Now sky is again partially covered, hope it will clear up a bit for a quick alignment and more test and a proper first light

The QHY5 how does it get attached to the finderscope and most of all focused? Any clear instruction how to do that and where to find adapters/connectors?

Anyone using QHY5 on a Mac through Parallels Desktop?

Thanks for all your suggestions

[Earl]

Reading around I understood that the ST150 is just about right on an EQ5 Deluxe, indeed it was sold also with that mount. I just tested it quickly and with the 2 inch diagonal and a heavy Baader ocular seems perfectly balanced in all directions after positioning correctly the tube and the one big weight at the end of his axe. The weigth of my D90 is even lighter than the one of the diagonal+baader, should be good. If anything it feels more 'robust' assembly.

Obviously in this situation I'd not add a piggyback guidescope, I'd rather guide with a finderscope. About the good ED80 I agree that would be an option, but I do mostly DSO (visual and imaging) and such aperture is not tradable with an 80 even if APO. When I bought the WO66 I was following a similar suggestion, but I ended up leaving the 66 taking dust or used as portable/holiday one, because compared with larger apertures (first a 150 reflector, then the ST102 refractor) it just cannot compare imho. I also noticed that an average ED can be compared to an achro with semi apo baader filter, even if not on big enlargements and very bright objects (not my interest anyway).

Now sky is again partially covered, hope it will clear up a bit for a quick alignment and more test and a proper first light

The QHY5 how does it get attached to the finderscope and most of all focused? Any clear instruction how to do that and where to find adapters/connectors?

Anyone using QHY5 on a Mac through Parallels Desktop?

Thanks for all your suggestions

Its not about apature its all about F Ratio. faster the better. and quality colour correction

For DSO imaging the ED80 is superior in all ways.

The EQ5 is ok for visual with this scope, but i very much doubt it will deal with imaging even a heq5 would struggle.

[rofus]

Hi Earl,

thanks for your suggestion, yesterday in the end clouds did not clear so I was unable to do any test, it seems tonight or tomorrow might be better so I'll do some test comparing same mount/exposure times and will let you know

I choose this combination because at a starparty I've seen someone doing amazing stuff (good few minutes guided) with an EQ5 Deluxe like mine and a Startravel150..how was he doing that? What do you think? Now I'm getting curious!

I agree that focal ratio is very important for DSO, but given same exposure time I can collect much more details into 150cm than into 80cm? In particular if I don't have the money to spend into a setup that can give me longer (several minutes) exposures and I also want to have something visual (details I see into a 6inch are not the same of a 4 or 3 inch refractor)? Just sharing the thoughts I had.

I'll try it all and will let you know...as I said I already did it with my WO 66ED: many told me to image with that, I tried but using my EQ5 unguided (2 minutes max exp) I obtained much better results with the Startravel 120, with the only downside of more CA (if there are bright stars in the field) that I fix in post production and a Semi Apo filter.

Curious to know your opinions

[wuthton]

I used an EQ5 pro for years and firmly believe it's perfectly capable mount for guided imaging but I never used it with anything like the weight you've got.

My total scopes, cameras and cables was about 4kg.

If you could post some images of your guiding graph and processed images because I'm mighty intrigued on how far you can push it.

You'll need to spend some time getting your balance absolutely perfect.

[wuthton]

I agree that focal ratio is very important for DSO, but given same exposure time I can collect much more details into 150cm than into 80cm? In particular if I don't have the money to spend into a setup that can give me longer (several minutes) exposures and I also want to have something visual (details I see into a 6inch are not the same of a 4 or 3 inch refractor)? Just sharing the thoughts I had.

The f ratio is everything when it comes to exposure time. A "faster", lower f ratio scope will illuminate the chip quicker than a "slow" high f ratio telescope regardless of whether the aperture is 2 inch or 2 feet.

You need to have a read about arcseconds/pixel, it will improve your understanding of astrophotography no end.

[rofus]

I used an EQ5 pro for years and firmly believe it's perfectly capable mount for guided imaging but I never used it with anything like the weight you've got.

My total scopes, cameras and cables was about 4kg.

If you could post some images of your guiding graph and processed images because I'm mighty intrigued on how far you can push it.

You'll need to spend some time getting your balance absolutely perfect.

I never used it guided, only unguided, and with my Startravel102 + NikonD90 (with battery pack so overall more than 4kg) I obtain exposures up to 90 secs (30% not perfect due to a Periodic Error I can see), sometimes up to 120 depending on where is pointing at. On my gallery you see in my signature you have the results: nothing mind blowing, but anyway something I'm proud of and pleasant to the eyes I think.

Before thinking about guiding, I'll do the same test with my Startravel150 + NikonD90 (without battery pack ) to see, with same objects, how long I can expose unguided. I spent yesterday a good hour balancing the scope itself (considering it has a bigger weight on the front), and I discovered that the 2" diagonal + Baader Planetarium ocular has pretty much the same weight of my D90+acc. So putting them on, there's a nice counter balance for the scope front heavy lens. Now the thing is greatly balanced on all axes and positions. I achieved this just putting one 5kg counterweight almost at the end of the bar.

Obviously if it does not work I'll have to find another solution (exchanging the tube or the mount), but I've seen it working very well...that's why I'm puzzled

[rofus]

The f ratio is everything when it comes to exposure time. A "faster", lower f ratio scope will illuminate the chip quicker than a "slow" high f ratio telescope regardless of whether the aperture is 2 inch or 2 feet.

You need to have a read about arcseconds/pixel, it will improve your understanding of astrophotography no end.

Thanks, yes I think I read about it already in specific, but I'll refresh it. What I meant is something different, probably did not explain myself good enough

Absolutely a low f ratio is faster than an higher one no matter what the aperture is, I'm also a photographer so I know this well. What I said is that a f/5 80mm and a f/5 150mm are not the same thing, even if sharing same focal ratio.

I'm just curious now to test how much I can push that mount and if I can get the same unguided exposure times I got with my ST102. What do you think will be the main problem? The stability/rigidity (even if scope is well balanced), the motors, else?

[wuthton]

Thanks, yes I think I read about it already in specific, but I'll refresh it. What I meant is something different, probably did not explain myself good enough

Absolutely a low f ratio is faster than an higher one no matter what the aperture is, I'm also a photographer so I know this well. What I said is that a f/5 80mm and a f/5 150mm are not the same thing, even if sharing same focal ratio.

I'm just curious now to test how much I can push that mount and if I can get the same unguided exposure times I got with my ST102. What do you think will be the main problem? The stability/rigidity (even if scope is well balanced), the motors, else?

You will need to guide to get anything like a decent exposure time, don't bother with unguided.

To achieve good balance take the OTA off the mount and balance across a pencil with everything attached, guider, camera (in focus) and all cables trailing as they would when mounted. Mark the balance point on the plate. When mounting align the mark with the centre point on the mount.

I've never bothered myself but you may see benefits moving the balance slightly East heavy (1-2mm or so), move the balance back to East heavy after a flip.

Also on your RA axis, general opinion is you are better off having more weights, closer to the mount than having one dangling off the end of the bar.

Any level of breeze will effect your guiding much more than on a heavier mount.

[Earl]

The main issue will be mass,

The less mass on the mount the more accuratly it can guide. each mount as a ceiling which you genrally need to subtract a little off to, then sub length, capable of 5 mins minimum really, below that is target specific.

Some may get it to work, but will it work every clear night without fail and faffing, if the answer is no then its not up to the task really.

[wuthton]

Absolutely a low f ratio is faster than an higher one no matter what the aperture is, I'm also a photographer so I know this well. What I said is that a f/5 80mm and a f/5 150mm are not the same thing, even if sharing same focal ratio.

Regarding exposure time they are essentially identical but an 80mm apo will blow a 150 achro out of the water with image quality.

Two things dramatically effect exposure time (sub length) in astrophotography, f ratio and pixel size of the imaging chip.

[rofus]

The main issue will be mass,

The less mass on the mount the more accuratly it can guide. each mount as a ceiling which you genrally need to subtract a little off to, then sub length, capable of 5 mins minimum really, below that is target specific.

Some may get it to work, but will it work every clear night without fail and faffing, if the answer is no then its not up to the task really.

Thanks for all this useful info. What I remember from that Starparty is that the guy told me for a long Evostar 150 I could be in trouble with an EQ5 deluxe (with steel legs, well balanced and with all bolts well tighten up), but that with the much shorter Startravel (a tad lighter as well and obviously shorter focal lenght 750mm) it's more than enough if I don't add too much weight with a guide scope but guide through finderscope (so is basically a dlr and a qhy like cam for guiding).

I feel for me to arrive to 5 mins subs the road is still long and probably more into a more accurate polar alignment (I have a fixed leveled position where I put the mount everytime and I just check in the polar alignment scope that all is fine after setting it with the discs). Adding a guide through finderscope I might go to 2 or 3 minutes and for me would be already a very good setup to enjoy a bit more, before arriving to the limit of the mount/telescope and upgrade the mount, the scope and/or an imaging CCD.

I just found till now that experimenting my own way, with patience and a correct stacking/production procedure, I can achieve quite interesting results...with this bigger scope I just hope to be more satisfied visually speaking, and then to gather more light in terms of photography, and add a finderscope guide to check how much I can push this mount, that seems to me still underused for what it can do?

Surely I agree an ED optically would be better, and that an EQ6 as well would be better, I'm just not convinced yet I pushed my setup to its limits, even with the ST150 on top. I hope to be able to test it all soon and post some results!

And in the meantime I need to see how to attach a guide camera to the 9x50 finderscope...without spending too much just as a starting guiding system.

[rofus]

Hello,

yesterday despite the full moon and quite heavy gusts of wind, I was able to take out the new 150 refractor to do some tests. I added another 5kg counterweight moving both of them higher up the bar, balanced the scope with the camera (focused) and all stuff on it.

I did my generic polar alignment, meaning that I aligned and calibrated my polar scope once when I got the mount, and usually using the discs and PolarAlign app I see that Polaris circle in the polar scope is indeed where is supposed to be, and what I do (starting from the same position in my concrete platform in backgarden, I just fine adjust the alt/az bolts so that Polaris is in the exact center of the polar scope Polaris small circle. I know I should then use drift alignment to get more precise, but I want to go there once I get the most out of a good (but not 100% precise) alignment.

Like with the Starttravel 102mm, the 150mm produces 80% stable 1 minute frames non guided. It has to be considered that not only is heavier, but it also is 750mm focal while the 102 is 500mm, so I was quite satisfied. Like with the ST102, I can then stretch it up to 90 secs or even 120 secs, depending on position in the sky of the object, but then it produces 30% to 50% (at best) ok frames, while the others has to be trashed. I notice that when so the error is periodic, so I kinda know is a periodic error. 

I attach below a single shot of M13 did just after sunset and before full moon, between wind gusts etc. I'm very pleased because it's a HUGE improvement to my 102 in several terms: much more detail (bigger aperture and longer focal length), there's much less distortion/defocus effect on the edges of the image (on the ST102 I was able to use 40% of the picture center). I also use a permanent 2 inch Semi Apo filter that really makes a huge difference.

NOW THE REAL QUESTION: I think it's time for me to try autoguiding, and for my situation (and pocket) the Orion Autoguider full package:

http://www.amazon.co.uk/Orion-Magnificent-Mini-AutoGuider-Package/dp/B0069W17R8/ref=sr_1_2?ie=UTF8&qid=1407749104&sr=8-2&keywords=autoguider

That is because it included already everything I need (and I can sell the SW 9X50 finderscope): the finderscope with good brackets/support, adapter, camera (working on OSX), and it costs just £50 then the camera only. Reading online they say that once I get 1 minute of non guided images, then the alignments is 'good' to start guiding, maybe not for 10 minutes exposures but up to 4/5 minutes maybe, and that  would be anyway a 200% more than what I get now, and many say that system works quite well.

Any impression on this setup? It also does add virtually no more weight to my mount, that with the ST150 is already "just" within its limits for astrophotography.

[rofus]

Forgot the picture..

[rofus]

Received today the Orion Magnificent Mini AutoGuider Package...weather doesn't seem to be good till Sunday, but will try anyway setting it up/focusing/aligning it, then if I see any hope of at least some clear sky I'll try a polar alignment and some tests of guiding!

Will keep you updated here about any further test...looking forward also to try the drift polar alignment with PHD in the future!

[rofus]

Hi all,

yesterday incredibly there were about 2h of clear sky over Norwich, so I had the time to bring out everything, assemble, do a polar alignment, assemble the mini guiderscope and Orion Starshooter, connected with my Mac with PHD2 and the mount, focused, locked parafocal ring, fine focused with the front lens and locked it as well (took a while but was well worth!), calibrated and did some quick guiding tests (just 30 minutes or so total).

Brilliant, quick, simple, and is very practical! Will post few questions about guiding results with some questions in another dedicated topic, and will update here once I get results and a decision about the 150 achromat or buying an ED80

[rofus]

Ok, the Orion Magnificient Starshoot Autoguide package was the deal for me, solved a few problems related to mount firmware, settings, software, please follow all details here (I think could be useful to others):

http://stargazerslounge.com/topic/222939-sw-eq5-guide-erratic-behaviour-what-to-inspect-guidelog-attached/