Advice on first tracker?

[mikeofthenorth]

Hello!

 

My hobby has been landscape and wide field astrophotography, but for years I’ve found myself drawn towards DSO, lunar, solar, etc - reading and day dreaming theoretical builds.  The impending total solar eclipse may be the last nudge I need to start down this path… and I was hoping to get a double check on what I am thinking about.

 

I’m considering buying a tracker for the eclipse, and to get something that I can build on to try out shooting objects this summer and see where that takes me.  Not a hard limit but looking in the $400-$1000 range, which I am hoping is enough to get something capable that I won’t regret, and could take me through the beginner stage.  I am not set on any particular set of objects, more want to do what I can with the camera and lenses I have already and go from there.

 

For relevant equipment, I have a Sony a7IV, Sigma 100-400, and Sony 200-600.  The A7IV + 200-600 tops out just over 6lbs so I’m thinking I want to aim for a stated weight capacity of 11lbs?

 

With two young kids my free time is thin, but I do make time.  I’m eager for any advantages I can get in streamlining setup and exposure - so I’d like to get a tracker that is compatible with the ASI Air.

 

I’m at the point where I’ve spent so much time reading and overthinking that I have totally confused myself.  The Sky Adventurer GTi caught my eye initially, but then I found criticism of its build quality.   I also saw well regarded options from iOptron, as well as the 2i and EQ3, but not having any hands-on experience yet I’m not sure what details matter to me and how to decide between them.  It there a consensus pick in the 11lb class?

 

Could I use a Benro FBAT24CVX25 tripod that I have already, or is it better to get the tripod that is made to go with?

 

Aside from a tracker, is there anything else I would need to be ready to make some attempts at astrophotography later this year?

 

Thank you in advance!

[Elp]

The SAGTI is the all in one replacement of the Azgti which many people, me included have been using for long exposure AP when it's converted to be used in equatorial mode.

The azgti transformed my AP, together with an Asiair. It's also enough for me to mount my 60mm refractor onto it. In alt-az default mode it's great for tracking the sun too with the appropriate solar filtering in place on the scope.

I don't think the in built tracking it too good though, not for AP. You need autoguiding really. So from the default azgti unit, you need to update the firmware on it (easy via WiFi) then you need:

An EQ wedge to angle the azgti to your pole star, an small dovetail to mount the unit onto the wedge, your computer controller (asiair or equivalent pc software), an eqdir or eqmod cable to connect the mount to the controller, a guide scope to "watch the stars", a guide camera to work with the guidescope, assorted cables and hardware to fix it all together.

Using another mount setup you'd still need the latter parts, though a beefier mount you can try using the in built mounts tracking once the mount is polar aligned, manually point your camera and start taking images.

The camera you've got is capable but I believe it's not the best for AP, Sony FF cameras have issues for AP imaging because of the way the sensor is put together and how it records data, the "star eater" issue isn't the only thing which is the main issue people highlight about Sony bodies. A default camera will be blind to hydrogen alpha emission too due to their in built IR filtering (as all daytime cameras have). It's not impossible, I tried my a7s with an Optolong lextreme filter and still managed to image hydrogen alpha gas.

I'd suggest you try it, you can image Orion (M42), Andromeda (M31) and Pleiades (M45) as well as open star clusters quite easily on a fixed tripod, you just need to keep the exposures short enough not to star trail and take hundreds to thousands of images then stack and post process them.

[mikeofthenorth]

Ah I forgot about the Az.  From looking at it in the past, I’d been somewhat confused how that mount works so thank you very much for breaking it down.  That helps it make much more sense!

So your suggestion would be the Az-GTi + S20530 EQ Base (plus the various parts and accessories you mentioned)?  I see there are Dec brackets and counter weights offered alongside the base, are those anything I'd need to worry about?

I was aware of the star eater issue, hoping it is something that I can get by with and if I get really hooked I would definitely invest in a dedicated astro camera and scope.  Until then, imaging those targets you mentioned would be quite an accomplishment within my current expectations.

It is a few steps down the line but is there a straightforward option for a guide scope and camera or is that an area to do more reading?

[GrumpiusMaximus]

I have an AZ-GTI an am branching out into astrophotography with it.  I picked mine up second-hand with the counterweight and counterweight bar, along with a better vixen dovetail clamp.  I had the EQ wedge for it (I also own a Star Adventurer, which I'm going to sell soon) but picked up another wedge from a member of this forum that's a homebrew design and much better than the Skywatcher one.

I'm using a Raspberry Pi 4 with Astroberry for control of the mount and camera (remotely logging in using a laptop) but there's no need for it really and you'll get away with an intervalometer with a DSLR.  The only tricky part is getting a polar alignment.  You'll either need to buy a bracket and polar scope or do the polar alignment in software with the camera attached to the scope.

I'm not guiding mine at the moment, which would make it much easier.  I haven't done much, only a couple of attempts so far and I've got a long way to go getting an accurate polar alignment.  An accurate polar alignment is an absolute must if you're just tracking - if you're guiding it's a bit less important but the better the alignment, the better the results either way.

Here's my setup as of yesterday:

The total equipment list here:

• Altair Starwave Ascent 70ED Telescope. (70mm at F6 - 420mm focal length)
• Altair Hypercam 183C (was gifted to me)
• AZ-GTI with counterweight and bar
• Second-hand homebrew EQ wedge
• Old Manfrotto aluminium tripod (second-hand eBay find)
• Talentcell 6000 mAh battery pack
• Lynx Astro FTDI EQDIR USB cable
• Lynx Astro Silicone Power Cable 2.1mm DC Jack to 2.1mm DC Jack
• USB A to USB C cable
• Raspberry Pi4 8GB
• Neewer generic spacing rings (you may not need these, depends on the scope and camera)
• Neewer generic vixen bar (again, not 100% necessary, depends on the scope)
• Golden Retriever x Labrador (4 1/2 years, moral support and assistance)

The Talentcell battery powers the AZ-GTI and the Raspberry Pi 4 (which subsequently powers the camera).  This is a complete grab-and-go, with no need for a mains power connection.  I have a dew heater too but that needs an additional power source as it pulls too much current to plug into the Pi.

The only additions I'd need to make for a 'full' setup is a guide camera and scope.  This setup can be converted to visual in under a minute by just removing the camera and cable and attaching a star diagonal.

For EQ mode with a setup like this, I'd definitely recommend a counterweight bar and weight.  It takes a significant amount of strain off the mount.  The better the balance, the better the tracking.

Edited January 27 by GrumpiusMaximus

[mikeofthenorth]

Thanks @GrumpiusMaximus - nice setup!  (In seeing your wedge, I saw something very similar-looking to that for sale on a website earlier yesterday and it is driving me nuts trying to find it again...I had no idea what I was looking at at the time so dismissed it)

Feeling more confident about being able to piece together a working rig.  What is the purpose of the spacing rings, how do they factor in?

lol with the golden retriever, I just have a cat who insists on getting in the way of everything.

 

[GrumpiusMaximus]

2 hours ago, mikeofthenorth said:

Thanks @GrumpiusMaximus - nice setup!  (In seeing your wedge, I saw something very similar-looking to that for sale on a website earlier yesterday and it is driving me nuts trying to find it again...I had no idea what I was looking at at the time so dismissed it)

Feeling more confident about being able to piece together a working rig.  What is the purpose of the spacing rings, how do they factor in?

lol with the golden retriever, I just have a cat who insists on getting in the way of everything.

The rings are there because to focus the camera, I need more travel than the built-in focuser can provide.  This isn't an issue with visual observing because the diagonal, etc. add to the length of the light path.  Without the diagonal, I need to add a bit more length into the light path to achieve focus.  If I had a field flattener, these may not be necessary.  This will depend on your scope, etc.

You'll need a wedge if you're going to do anything that needs tracking, as it's necessary to polar align.

I'm at the beginning of this hobby and I'm having issues getting my polar alignment routine to work in software.  I know what I need to do but there always seems to be a technical issue and I can't quite get it to work.  I've got plate solving working at least!

Really would recommend watching as many videos on the principles of astrophotography as possible, it'll really help if you understand why you're doing things!

[Elp]

The extension rings are there as described, to be able to get the camera sensor to the point of focus. With field flatteners this dimension is typically +55mm behind the field flattener, if you've got a refractor it'd be generally handy to have sets of spacer rings and fine spacer rings at hand. 

[mikeofthenorth]

@GrumpiusMaximus If you don't mind me asking, how long is your vixen bar in that photo?

[GrumpiusMaximus]

12 minutes ago, mikeofthenorth said:

@GrumpiusMaximus If you don't mind me asking, how long is your vixen bar in that photo?

300mm.  Annoyingly, the point of balance of that telescope is actually behind the foot that it came with when you add on a camera.  It's marginal even with a basic 1.25" diagonal and eyepiece...