Guide scope for Skywatcher Explorer 200P

[Chickpea]

Hi,

I bought an Explorer 200P a few years ago, with an EQ5 GoTo mount and an ASI224 camera. I spent a small amount of time observing an imaging a range of planets, stars and DSOs. I feel that I got some descent stacks of Jupiter and also some DSOs (including the Whirlpool). 

Due to moving around I am only now at the point that I am setting up again, and would like to get back into observing and imaging.

Previously I used software which included SharpCap, and maybe others that I can't remember.

I have the mount set up now with the camera, and I also have an EQMOD cable arriving, which I intend to use with NINA and Stellarium, plus SharpCap for imaging.

One thing that I never had was a guidescope and I would like to look at adding one, and would appreciate any advice.

FLO currently have a bundle with an ST80 and an ASI120, which looks fine to my untrained eye, but with a little reading around on this forum, it seems that the ST80 is considered a bit too heavy for accurate guiding on an EQ5.

Any thoughts on that and any good alternatives for scopes and cameras would be much appreciated.

Budget wise, I am fairly flexible, and would rather spend a bit more to get a guidescope that will perform well, and would also future proof me if I moved to a better main scope in the future.

Edited April 14, 2023 by Chickpea

[michael8554]

1000mm focal length is in Off Axis Guider (OAG) territory.

Michael

[malc-c]

A 200P plus an ST80 on and EQ5.... that's pushing the loading capabilities of the EQ5.  I had the same combination in and HEQ5 and that was taking the HEQ5 to the acceptable loading for imaging.   I would suggest you look at converting the 9 x 50 finder into a guide scope, or possibly off axis guiding to keep the weight down.

[Chickpea]

Thanks to both of you.

Very interested to see the setup in your sig Malcolm, because I also have a 400D which a member of the family has started dabbling with taking wide astro shots on a static tripod (with the inevitable streaking).

I would really like to add the ability for them to use the EQ5 to facilitate their use of the 400D, but don't yet know where to start.

I have seen videos of people using an EvoGuide 50ED as a guidescope but also as a scope for DSLR captures, but jumping to the end of your observatory thread (which I am going to read in its entirety) I see that you have yours attached to the 200P. Does that need much modding to setup?

In the same pic, is the silver bit at the end of the finderscope the guide camera itself, or just a fitting? Are there any guides for the conversion?

Although I don't have a good location for an observatory (which would need to be slap bang in the middle of the lawn) I have been considering ditching the tripod, creating an anchor point in the lawn, and them having a column that can be quickly attached to the anchor point for quick setup. Do you have any pics that show the entirety of the base your HEQ5 is mounted to.

Sorry for all the questions Malcolm, but there is so much about your setup that I would love to replicate! 😁

[malc-c]

Don't worry about asking  questions, keep asking.

The 200P/EQ5 setup is ideal for visual, but at the limit for imaging IMO.  I started that way.  I soon found the visual observations of targets underwhelming from my location, so tried a friends 300D and was amazed at the results even from a town location.  But you really needed a windless night to get the best as the 200P acted like a sale in the slightest of breezes and the EQ5 just wasn't firm enough to reduce the movement.  Years ago when there was less choices of mounts we had the EQ3, EQ5, HEQ5 and EQ6.   Often the EQ3 would be used with a 150P, the EQ5 with the 200P, HEQ5 / EQ6 with the  300P.  But we would often suggest that for imaging you step them up, so that the 150P sits on the EQ5, the 200P on the HEQ5  and the 300P can stay on the EQ6 as that is a beast of a mount (before the days of the EQ8). 

You can use the 200P with the EQ5, but you just have to accept that there are limitations.  If you can come up with a wind brake to shield the scope from the wind then that will help, but ideally you also need to reduce the weight, which is typically 2/3 of the stated visual loading for the mount.  An ST 80 and guide camera is a fair bit of weight, which is why I removed and sold mine and then obtained the adapter ring to fit the QHY5 (the silver bit at the end of the finder)  to the finder scope.  It works, but the short focal length can cause the guiding software to have a hissy fit on some occasions.  The Evoguide and similar scopes are nice, but as you already have a similar sized aperture scope then why not use it.  The stars in the image my QHY5 produces are ideal for PHD2 to guide with.  If you want to use the ED as a secondary scope for wide field images then go for it, the ED optics will outperform the finder scope, and even the ST80.

The fitting of the guide camera to the finderscope requires an adapter ring that has a standard T or C thread on one side and the fine pitch thread of the tube of the finder.  These are around £30 Example here

The mount in my observatory is attached to a DIY pier made from 6" plastic drain pipe, sunk into a 1cu metre block of concrete with the pipe filled with rebar and more concrete.  The custom machined mounting plates were then dropped in place and aligned with a mark I made when the sun was at 12 noon GMT so the pin the HEQ5 uses for AZ polar alignment is on a N/S line.

Other examples of out door piers can be found on the forum.  Some used hollow building blocks as a base which is cheap and weather resistant.

If you have any more questions about my rig then just ask

 

 

[Chickpea]

Thank you Malcolm.

The info and the pics are very much appreciated.

With regards to the guiding I have looked at the option of converting the 9x50 finder and it looks straightforward. I am considering pairing an ASI120 mini with it.

The other thing that I have now been looking at is OAG, which is a completely new concept to me. There seem to be some very strong advocates for it, especially when the focal length gets to around 1000. As I have done no guiding before, I am wondering whether I should go straight to OAG.

I might be tempted to got the 9x50 guidescope route first, and maybe progress onto OAG, but it seems that the cameras which are good for guidescopes (such as the ASI120 mini) are not necessarily good for OAG. The best option for a camera that can be used with the 9x50 and also be a serviceable OAG camera seems to perhaps be the ASI 290 mini (~£300).

It does seem that a lot of people like the ASI 224 (which is what I have) for OAG, and if I went that way I could perhaps justify getting better camera (putting the £300 saved on not getting the ASI 290 towards it).

I am also questioning the mount now as getting an EQ5 feels that like was a bit of a false economy, if it is going to be problem for imaging with a 200P (even keeping the weight down with OAG).

I'm tempted to go for an HEQ5 (currently there is a bundle with a 200P-DS which seems good) or perhaps even an EQ6-R (which is expensive, but which would seem to be significant future proofing).

Thanks for the photos of the pier. What I really want to do is to lay the concrete base below the level of the lawn, and then have a column that can be bolted to the base, but easily removed and the base covered so that the lawn can be used by the kids. Your advice has been a great headstart and I will look at other designs, as you suggest, to get a feel for the range of structures people have successfully used.

Obviously you use a guidescope rather than OAG and I would be very interested to hear your thoughts on whether OAG is needed for my setup and whether I may as well just go for it, rather than trying a guidescope.

 

 

 

Edited April 17, 2023 by Chickpea

[malc-c]

I was considering OAG and found I would have  needed a very thin OAG to get focus on the D400.  At the time this was only available from Germany, and the cost of around £120 so I shelved the idea and converted the finder to a guider for £30.  OGA has the advantage of using the same optical path of the scope, and it's long focal length should in theory give better performance.  The downside is that it puts an obstruction in the optical path so you can get shadows or other artefacts in the images.

My advice would be to spend £30 and get the finder adapter and convert it to a guidescope.  Set the scope up on the EQ5, point it at a star close to the Celestial equator / Meridian intersection and let the computer run a guiding session.  You've not mentioned how you intend to control the scope, but I presume an EQDIR cable to a PC running EQMOD or Green Swamp Server, with a planetarium application such as Cartes du Ciel and PHD2 to handle the guiding ?  If that is the case then read up on using pulse guiding with those applications rather than on-camera.  Enable PHD2 log recording and then post up the log files if things don't go as expected.  If it performs well (ie the traces in PHD2 are as flat a trace as possible or the total errors are small then there would be no need (just yet) to look at upgrading the mount and optics.  I had a long thread that ran for almost a year where I tried to get rid of a rouge spike on bright stars.  In the end I replaced the stock secondary on my 200P with an Orion Optics secondary that had the same dimensions as the 200PDS and that worked really well, and saved me having to sell the 200P OTA and purchase the 200PDS OTA.

With regards to the base, yes having a foundation slightly below the level of the grass will help with mowing the lawn.  However, most who use a fixed outdoor setup tend to build a permanent pier with a head to accept the mount.  This is protected by using a thick plastic bag and rope when not in use.  Some even leave the mount attached and protect it with upturned plastic dustbins and bungy cords, up to a small tool shed that looks like a portaloo  that is rolled back, almost like a mini observatory.  If you are considering a removable plinth / pier then it has no advantage over using the stock tripod, and if using the tripod you could get away with three smaller concrete blocks/foundations placed where the feet of the tripod are placed.

So invest £30 in an adapter and see how your existing rig performs.  If you are happy with the guiding performance, or more importantly all the subs have nice sharp circular stars then there would be no need to look at upgrading the mount or the OTA, at least for now.  My HEQ5, ST80 and QHY5 were purchase second hand from an SGL member in Sunderland.  It resulted an a 480 mile round trip, but I got a great deal, and would advise looking at the classified section when you reach the criteria as savings can be made.

 

As you can see by the image above, I needed an extension bar to counterbalance the weight of the 200P, ST80, QHY5 and D400....

[Chickpea]

Thanks again for all of the support here.

There have not been a huge number of clear nights over the last few weeks, but there have been enough that I have managed to go from "spending all night trying to get a target in view, while PHD2 refuses to calibrate and APT refuses to plate solve, with intermittent equipment disconnects and tracking stops and dead DSLR batteries every half hour" to a point where, for the past couple of nights, I can now setup quickly, usually recalibrate PHD2 on the first attempt and use Goto++ in APT with few failures.

I am using my ZWO ASI 224MC attached to the SW 9x50 Finderscope for guiding and an unmodded Canon 400d for imaging, with an Explorer 200P on an EQ5 goto.

Following advice here I have decided to take the plunge and upgrade the mount. I decided on an EQ6R rather than an HEQ5 because it was only a couple of hundred extra and I suspect that I would have regretted not going that little bit further.

I do still want to look at some form of autofocusing, but the focusing tools in APT and SharpCap have really helped to increase the speed and accuracy of my manual focusing. I am also looking to understand more about the DSLR modding options that are available.

I also really have no idea what I am doing in DSS, and am currently just randomly picking options and sliding sliders until the image look better, so I have a lot of learning to do there.

Below is the best I have managed so far (15 x 5 minute lights + 3 darks).

I'm looking forward to learning a lot more and am very appreciative of all the advice,

 

 

 

 

[malc-c]

2 hours ago, Chickpea said:

Thanks again for all of the support here.

There have not been a huge number of clear nights over the last few weeks, but there have been enough that I have managed to go from "spending all night trying to get a target in view, while PHD2 refuses to calibrate and APT refuses to plate solve, with intermittent equipment disconnects and tracking stops and dead DSLR batteries every half hour" to a point where, for the past couple of nights, I can now setup quickly, usually recalibrate PHD2 on the first attempt and use Goto++ in APT with few failures.

Welcome to the world of imaging !! Glad you managed to resolve those issues and now have a quick workflow.

To be honest, I would be very happy with your first image, especially given the equipment and the steep learning curve you've been through.  I think you now realise just how faint a lot of these targets are, and how much data is needed for some targets.  I normally run a plan of 20 x 5min subs, 20 x 5min darks and then experiment with flats etc.  I'm guessing you are not using a coma corrector as some stars at the edges look a little elongated, where as central stars are nice and round?

Wow, upgrading to an EQ6... they should make a great difference, in both precision but also stability and very able to handle the weight of the scope and other equipment. 

 

[engstrom]

Sorry to resurrect an old thread. Long story, short; bought 200p DS and heq6 years ago to learn AP but life intruded and it’s mainly gathered dust. Now my 6yr old is gaining an interest in astronomy it’s time to dust it off.

Reading through this thread it seems maybe with the additional weight of my camera body (5dmkiii) OAG might be the way to go to trim the load as much as possible. Malcolm, you mentioned the need to get a thin OAG for the 200p but would this be less of an issue with the 200p DS and its modified tube for DSLRs?

Also am I asking for trouble using the 5dmkiii and its large sensor in an OAG setup possibly making positioning of the prism awkward? I do have a 450d (somewhere) but the 5d’s generally “better” sensor makes me eager to use it?

Or should I just bite the bullet and buy a dedicated (budget - lol) camera? Probably a colour model as adding a filter wheel would add more weight to a mount already reaching overload.

[malc-c]

It was several years ago when I was researching this and I can't recall if the need for a thin OAG was required for the 200P before or after I swapped out the mirror for one of the same dimensions as the DS.  But then again, I believe the secondary in a DS  is mounted slightly closer to the primary to take advantage of the size ?

Sorry I can't be much help here, memory isn't that good.

[Stefan73]

If you want to do astrophotography with a DLSR then you're probably best going for the thinnest OAG going.  Something like this: https://www.firstlightoptics.com/off-axis-guiders-oag/ts-off-axis-guider-tsoag9-length-only-9-mm.html

Even if your focus position is fine with a thicker OAG you might want to use a coma corrector in the future and those often have 55mm back spacing so you wouldn't have room for anything thicker in front of the DLSR.  

I've no experience with the 200PDS but the 130PDS was not usable without modification even with the above 9mm OAG as the focus tube was pretty much in as far as it would go to achieve focus and you just got pacman stars without cutting off a lot of the focus tube to stop it protruding.  Using a coma corrector too was fine though.

 

[Ouroboros]

43 minutes ago, Stefan73 said:

If you want to do astrophotography with a DLSR then you're probably best going for the thinnest OAG going.  Something like this: https://www.firstlightoptics.com/off-axis-guiders-oag/ts-off-axis-guider-tsoag9-length-only-9-mm.html

Even if your focus position is fine with a thicker OAG you might want to use a coma corrector in the future and those often have 55mm back spacing so you wouldn't have room for anything thicker in front of the DLSR.  

I've no experience with the 200PDS but the 130PDS was not usable without modification even with the above 9mm OAG as the focus tube was pretty much in as far as it would go to achieve focus and you just got pacman stars without cutting off a lot of the focus tube to stop it protruding.  Using a coma corrector too was fine though.

 

I agree. I wouldn’t use an OAG with my 200P for the reasons you point out. I have obtained adequate guiding with my 200P using a 9x50 finder guider - although perhaps one might expect slightly better results using a  longer focal length guide scope.

Something else you don’t often hear mentioned is how useful a finder guider (or separate guide scope) can be for  observing. If you set the finder guider as the main scope, and use plate solving, you can be sure that the weak fuzzy target is smack bang in the middle of the eyepiece - assuming that is you’ve aligned the guidescope and main scope to the same point. I don’t think you can do that with an OAG.