What's my weakest link for AP, any advice / suggestions?

[Trippelforge]

I just got my son into astronomy about a week ago and we have been sitting outside together nightly since. He is rabidly eating up everything in regards to AP, and now we have been battling side by side together. I bought a setup about a decade ago without much guidance or experience. Well outside of the fact that as my first scope nearly killed the hobby for me, as I had the notorious 127eq Power Seeker. O.o

Currently my setup isn't exactly high end, it's a step up from a department store, but I am running into some frustrating issues. Mostly due to tracking, and secondly a bit suspect of my DSLR. So I wanted to share my setup, and see if it's worth using say the scope and changing out the mount, perhaps getting a new DSLR etc. The problem is that I am on a budget so buying a completely new rig will be awhile down the road. 

Here is my setup;

Barska Magnus 80mm F/7 ED Triplet
Celestron CG-4
Celestron Dual Axis Motor Drive
Celestron RACI Illuminated 9x50 finderscope
Polar Finder Scope (can't remember what model)
Canon EOS Rebel T1i (500D)

What do you guys think would be the best thing to replace first? Thank you for the help!

Random photo of my setup

Edited October 5, 2022 by Trippelforge
added photo link

[doublevodka]

Nice scope you have there, was only reading about them yesterday strangely enough!

Bit hard to comment without a budget in mind, but the mount is always the main thing, any weakness there is going put you back, no matter how good the equipment on top of it is. If you like Celestron kit, then maybe have a read here - https://www.scopereviews.com/page3l.html

Plenty of people manage fine with DSLR's like that so my first recommendation would be mount, then cameras, then guiding equipment

[vlaiv]

Hi and welcome to SGL.

That is interesting looking scope. I'm surprised that it is F/7 triplet at 80mm.

Are you sure of those specs? If yes, then don't change the scope unless something is seriously wrong with it. It can serve you in wide field role for many years.

If it is doublet - then it will be fine for some time until you get some experience, but at some point you'll likely want to upgrade.

First and most important thing for AP setup is mount. That should be your number 1 priority for upgrade.

Ideally you'd want something like Heq5 (second hand if budget is tight) - or at least EQ5 with goto. Get the best mount that you can for your budget.

All the rest can be very cheap and you can use what you have. Next upgrade would be auto guiding. You'll need some sort of guide camera and guide scope. This can be rather inexpensive with a bit of DIY. People use modified web cameras (just removed front lens to expose sensor), mounted on finder scope instead of its eyepiece. There are adapters available to attach camera (via T2 thread) - or if you have access to 3d printer - that can solve a lot of things rather cheap (for example - you can make your own guide scope from a lens from old binoculars, some PVC pipe and few 3d printed parts).

So yes, that is order of upgrade:

first and most important - mount

second is to think about guiding that mount. Rest is fine for the time being.

Edited October 5, 2022 by vlaiv
missing letter ..

[Trippelforge]

48 minutes ago, doublevodka said:

Nice scope you have there, was only reading about them yesterday strangely enough!

Bit hard to comment without a budget in mind, but the mount is always the main thing, any weakness there is going put you back, no matter how good the equipment on top of it is. If you like Celestron kit, then maybe have a read here - https://www.scopereviews.com/page3l.html

Plenty of people manage fine with DSLR's like that so my first recommendation would be mount, then cameras, then guiding equipment

I was hearing a lot of good things about them when they were new. Cloudynights has a pretty long thread on the scope (although it's not really active now). The biggest issue I have had is the lack luster focuser, it's pretty bad. I am trying to figure out how to fix it / tweak it right now. I am obviously not an expert but the optics of it seems pretty solid.

 

47 minutes ago, vlaiv said:

Hi and welcome to SGL.

That is interesting looking scope. I'm surprised that it is F/7 triplet at 80mm.

Are you sure of those specs? If yes, then don't change the scope unless something is seriously wrong with it. It can serve you in wide field role for many years.

If it is doublet - then it will be fine for some time until you get some experience, but at some point you'll likely want to upgrade.

First and most important thing for AP setup is mount. That should be your number 1 priority for upgrade.

Ideally you'd want something like Heq5 (second hand if budget is tight) - or at least EQ5 with goto. Get the best mount that you can for your budget.

All the rest can be very cheap and you can use what you have. Next upgrade would be auto guiding. You'll need some sort of guide camera and guide scope. This can be rather inexpensive with a bit of DIY. People use modified web cameras (just removed front lens to expose sensor), mounted on finder scope instead of its eyepiece. There are adapters available to attach camera (via T2 thread) - or if you have access to 3d printer - that can solve a lot of things rather cheap (for example - you can make your own guide scope from a lens from old binoculars, some PVC pipe and few 3d printed parts).

So yes, that is order of upgrade:

first and most important - mount

second is to think about guiding that mount. Rest is fine for the time being.

It's a triplet, and is 560 x 80mm which I believe comes out to f/7. It was a steal years ago when released, I ran across a good amount of people on cloudynights that owned them. But I guess now almost a decade later, and due to being discontinued they aren't talked about much anymore. 

The mount suggestion makes a lot of sense, I suppose that can last me a very long time and I would need one anyways if I upgraded my scope. I am going to go look around for a EQ5 / Heq5 and see what kind of deal I can come find. How does the guiding scope differ from polar aligning in general?

Thanks for the help!

[vlaiv]

1 hour ago, Trippelforge said:

How does the guiding scope differ from polar aligning in general?

Polar alignment is procedure to align RA axis of the mount to rotation axis of the earth (both will then point near Polaris - tiny bit to the side to actual NCP - North celestial pole). After it is completed, mount should track properly if it is perfect.

However, no mount is perfect, and for that matter - pointing it near Polaris is not done perfectly either.

Small deviation in polar alignment causes small drift in DEC over time.

Since mounts are not perfect - in sense that mechanical components are not perfect circles as there are manufacturing tolerances and error - we get another kind of tracking error - mount periodic error. Even if you roughly polar align (within few arc minutes of NCP) - that error will be usually smaller than mount periodic error - which can be significant.

Both of these cause star trailing because both errors cause stars to drift from their original position over time. Polar alignment drift is in DEC axis, while periodic error is in RA axis and as name says - is close to periodic in nature.

Here is recording that shows both nicely:

In above gif - mount is actually tracking and motion that you see is solely due to error in tracking. Slow drift from right to left is due to small polar alignment error - it is very uniform and not large in magnitude (each individual frame of that animated gif is one minute long exposure). Jumping up and down is periodic error - you can see why we call it periodic - it sort of repeats time and again - almost the same each time (but not quite). This is because there are different gears in a mount and each of them is somehow elongated and sometimes trails and sometimes leads. When all those little errors combine - we get this kind of wavy motion.

Back to the guiding - guiding is solution to above problem.

With guiding - there is separate camera on separate scope (or OAG - off axis guider - special device with a little mirror that lets you attach second camera to main scope) that takes short exposure every few seconds and compares star positions to previously recorded stars. If it detects any sort of drift between two exposures (even sub pixel accuracy) - it will instruct mount to correct its position to compensate.

In order to do that you'd need:

1. guide scope (or OAG, but guide scope is simpler to begin with)
2. guide camera
3. computer that issues corrections to your mount.

All of that can be pricey, but it can also be made really cheap - depending on how you want to approach it and can you do a bit of DIY.

Probably cheapest option is to

a) use your finder scope as guide scope with simple adapter (unscrew finder eyepiece and put adapter for camera in its place)

b) use simple web camera as guide camera. There are several models that are suitable for this and it involves removing front lens of web camera and fashioning some sort of adapter to attach to guide scope. I once made such camera from Logitech C270 - although I did not use it as a guide camera - but rather planetary camera (guide camera and planetary camera are very similar in their specs). I used 32mm OD PVC pipe sanded down as nose piece

c) This tends to be most expensive part if you don't already own some sort of laptop - but old laptop, tablet or even single board computer liker raspberry pi can be used for this.

In any case - if you look at images of peoples imaging rigs - you will often notice small scope with camera attached - like this:

(this is very nice annotated image from Astrobackyard website).

You of course don't need all the gadgets shown in the image - however, note guide scope and guide camera being attached.

Youtube contains a lot of videos showing how to guide and what sort of setups people use, so it's worth exploring a bit as well.

[Trippelforge]

Wow that is a really amazing response, thank you so much for explaining everything to me!

Tucked away somewhere I actually have two webcams that I converted many years back. I don't know if they will fit my finder scope or not, I think I used film canasters or something so I guess I will need to come up with another way. The one thing I am not sure about is how the motors get controlled via this method? Perhaps my mount isn't capable due to it's basic operation? I currently do use a laptop to run Backyard EOS with it, I couldn't imagine doing imaging without it's focus feature. It would be very neat to have something like this in place, but again I am not sure if my motors would be compatible, unless there is some way around it's basic controller. 

Thanks again!

[vlaiv]

1 minute ago, Trippelforge said:

I think I used film canasters or something so I guess I will need to come up with another way.

That is another way to add 1.25" nosepiece, but in case of finder scope - that won't do as you need short adaptation.

Cameras are usually attached to finder scope with this kind of adapter:

https://www.firstlightoptics.com/adapters/astro-essentials-sky-watcher-9x50-finder-to-t-adapter.html

Or perhaps something like this:

https://www.firstlightoptics.com/adapters/astro-essentials-sky-watcher-9x50-finder-to-c-adapter.html

depending if camera has T2 thread or C thread connection.

But in your case - it has neither and you need to fashion something.

I'd look into one of following two ways - if you have access to 3d printer - then you are pretty much sorted - just print suitable adapter depending on your guide scope. If not - try to find plastic cover that will fit on finder tube nicely (similar to finder scope cover on front side). Then you can cut hole in center and glue it to web camera instead of film canister.

Before you glue it - just check if you can reach focus at infinity with it (finders can adjust focus with moving lens on its thread so you can do fine focus - just make sure you are in ballpark to be able to focus properly).

8 minutes ago, Trippelforge said:

Perhaps my mount isn't capable due to it's basic operation?

I'm not familiar with that particular Celestron motor upgrade - but I do know that Skywatcher has two different motor upgrades for its EQ3/EQ5 mounts - one with ST4 port and one without.

If there is port on your hand controller marked with AutoGuider - or ST4 - using RJ11 connector (analog phone connector - similar to RJ45 ethernet connector but using only 4 wires) then you can use ST4 protocol.

We now just need to figure out how to use ST4 protocol directly from laptop (guide cameras have ST4 port that you can use via their USB driver - computer connects to camera via USB and camera connects to mount via ST4).

Well, there is adapter:

https://telescopes.net/zwo-usb-st4-adapter.html

And maybe there is DIY solution as well for it.

But first check if your hand controller has ST4 port and can be guided. If not - not all is lost, but it will depend on how much DIY you want to do.

https://github.com/TCWORLD/AstroEQ

This is a way to make your own Arduino controller that will talk to stepper motors you already have (hopefully they are stepper motors). It will be able to connect to computer and then you can use all sorts of advanced features like plate solving, planetarium software to point your telescope to wanted target and so on...

Alternative is of course - mount upgrade.

[Trippelforge]

Thank you once again, the amount of information and help you have given me is amazing. I am for sure going to give it a shot, I mean what's the worst case scenario? I am going to upgrade my motor as well!