Beginner Q's - Sony A7Rii & Mounts

[aiiiidan]

Hello!

 

I'm new to the forum. I've moved (from London) to the countryside (Cotswolds) and can suddenly see the stars. 

 

I'd love to get a scope that is both good for visual and imagining. I've done tons of research and I'm pretty sure the Sky Watcher 130 PDS is the one for me because not only will myself and my wife and kids get a good look at the night sky, but also I want to potentially get into astrophotography (deep sky stuff) - which brings me to my two main questions -

 

- I already have a Sony A7Rii. Sounds like full frame isn't great for Astro. However, this camera has a cropped mode too. So I wonder if anyone have any experience using this for astro?

- For tracking, my budget (about £500 all-in) won't cover a HEQ5. Has anyone had good results with a EQ3 + a motor  ...and possible I'd need a polar scope too? It all adds up. Do I save up for a better mount?

 

Cheers!
Aidan

 

 

[Elp]

Hi, welcome to the SGL.

Have you got prior experience? If not a good quality refractor may be better, an aperture you can afford (Around 60mm start, 80mm seems to be a good medium, 100mm plus more pro). Good apochromatic and coated optics are preferred.

Full frame should be excellent for astro but I believe it depends on what scope you pair it with, having done prior research into the A7R I believe Sony's camera software also has an issue with "aggresive" clipping out of stars thinking that it's camera noise. The best thing you can do is try it, even on a standard photo tripod with less than 30s exposures you will probably find it is a very capable camera right from the get go.

Mount is possibly the most important part of your rig as the last thing you want when imaging is vibrations (vibrations are equally bad for viewing) or the mount not able to hold the telescope without it drifting in RA or declination under its own weight (or worse falling over), you need to estimate on how much your imaging setup is going to weigh and note the longer the focal length of the telescope/lens the better your tracking needs to be when imaging. HEQ5s are supposed to be good, people knock EQ3s but I had an EQ3-2 and it was a solid mount especially with the steel tripod.

Polar scope is useful, for better alignment you will have to learn drift alignment if you're going to image, if you want to go more advanced then utilising some form of computer setup goes into a whole other territory. For basic visual I just align with a compass to true north and set the altitude on the EQ wedge. Then with a goto mount like an AZ GTI alignment is easy and finding targets is relatively frustration free. Bare minimum you'll want a mount which allows some form of slow motion control which allows precise adjustment of view.

The best equipment to buy is the one you are going to use, personally I started with larger equipment and sold it on as it sat unused until I built up an established travel setup which I can take anywhere easily, now I use it whenever I can.

[aiiiidan]

Thank you for the reply!

All very informative, thank you so much. I agree with everything you said. I have experience with cameras and even film with motion control rigs. But no experience w/ astrophography. I think what you said is also quite right - buy something I'll actually want to get out and use. So I think I will get a decent refractor myself and family can use for viewing - no Go To mount or anything, but something sturdy like an EQ3-2. Then I can see if I enjoy it, and if I do I can start putting my camera on there and then open that can of worms! At least then I'll have a scope and mount that can be upgraded.

 

Thanks for your help. And yes, I must try just my Sony + my 85mm f1.4 on a tripod and see what I can snap. I think I have a fast 135mm knocking around too. I would assume anything over 30s exposure I would need to start tracking...

 

Cheers!
Aidan

[Elp]

I would heartily recommend the AZGTI, its not too much cost and fits a standard photo tripod although you are limited to 5kg payload. By default it operates in alt azimuth mode so is good to begin with for locating stuff (ie up is up, down is down, left is left, right is right). For photography it will need to be paired to a equatorial wedge and upgrading the firmware (easy process) of the AZGTI so it can operate in EQ mode so once polar aligned (drift aligning is better) it rotates in sync with the earth's rotation (or from the observer's perspective the starfield rotation). Alt az mode is okay for solar system imaging as you'd be taking very fast exposures.

Note polar alignment of the AZGTI is an issue as you cannot directly fit a polar scope pointing straight through with what would be the RA axis, you can roughly point your setup to polaris using a manual compass which has an East/west indicator to point to true north and setting the equatorial wedge to your latitude (52 degrees in most of the UK), then look through the telescope/finder/or take a dslr long exposure to see the effect of star trailing.

I recently sold my Star Adventurer because of frustrations with having to find or point to objects which the AZGTI goto alleviates once aligned, it's not totally accurate but I managed to photograph Andromeda the other day for around an hour total and it generally kept track though I had to adjust a few times between frames to centre it again, if I relied on visual I wouldnt of able to have done it as it couldn't be seen. It is controlled via WiFi with a phone app, the two axis can be unclamped so you can manually move, and the app has a database of targets pre loaded for it to automatically goto. This took a lot of frustration out for me, now I'm in the process of setting up autoguiding so I can do longer than minute exposures (havent cracked it yet).

As for your initial camera setup it depends on where in the sky you are pointing, ive found sometimes 30s is fine, other times up to 10 seconds the limit. A good target for this is the Orion nebula just offset from Orion's belt, it's a fairly bright target which visually is sometimes difficult to see, your camera however may pick it up in around a 5 second exposure, I was surprised to have imaged it from my heavily led light polluted garden as I couldn't see it but my camera saw it as if it were in plain view.

If you want a compact photo setup specifically with your camera I've found the Omegon LX mount excellent (its fully mechanical), you'll need a equatorial wedge to go with it but i found wide field I could do 1 minute exposures no issue, it also has a very basic polar "scope", more like a straw, to align it to polaris.

[aiiiidan]

Wow, thanks so much for all your advice! I need to digest some of that and defintiely do a bit of googling. I do like the look of the AXGTI and the fact it has its own Wifi etc...less wires I assume too. Thank you so much

 

Omegon LX looks great, didn't even know that thing existed! Fantastic.