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Next step after a7R iv and SkyGuider Pro

Astrophotography Beginner Equipment
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#1 robert.ryan

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Posted 06 August 2022 - 05:34 PM

I am getting into DSO astrophotography, and heeded advice to not just spend a fortune in a whole new setup, but rather take baby steps, and use equipment I already have, and just see how it goes. So, I’ve paired my existing photography kit (e.g., Sony a7R iv, 200-600 f5.6-6.3) and only purchased iOptron SkyGuider Pro and Bahtinov. I can quibble about little things (very slight coma in corners of my lens at 600mm at f6.3, though not nearly as bad as my 70-200 lens; slight chromatic aberrations on the bright starts in corners; etc.), but artful cropping and post processing hides some of these sins. But overall, I’m super happy and learning a ton.

 

My question is, given that I’m most attracted to DSO/nebulae, what the next investment should be. I gather that people often next consider astromod of one’s DSLR/MILC camera, but that turns out to not be practical for the Sony a7R series. So, that having been said, I’m debating what is the best next investment would be. I’m debating between the following:

 

1. Add guiding to SkyGuider Pro for longer subs. I’ve been sticking to 30 second subs @ 600mm on my tracker, and I gather that auto-guiding will enable longer subs. (I confess to be skeptical given that it can only auto-guide for RA, but Peter Zelinka seems to suggest, https://youtu.be/4_F72Uf0yaU, that he went from 30 sec to 4-5 min subs @ 600mm with auto-guiding on star tracker.)

 

2. I could jump directly to proper mount, presumably enabling longer subs, too, and would be something I could use when I eventually upgrade my OTA.

 

3. I could upgrade to dedicated OSC camera (to pull in more UV for those emission nebulae). But if I do this first, I might have to stick with unguided star tracker (and short subs) for now.

 

I guess I’m leaning towards tackling these, in this order, over time (in order to reduce one-time expense as I’m getting into this), but would appreciate suggestions and/or practical experiences of others, if you think I should change the order or do something completely different.


Edited by robert.ryan, 06 August 2022 - 05:36 PM.


#2 cmanley134

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Posted 06 August 2022 - 06:05 PM

1. Autoguiding will yield a significant improvement in your potential exposure times, but I would encourage you to pay more attention to total integration time than the length of your individual subs. As long as you're able to hit a 1/4 to 1/3 histogram at a reasonable ISO that's fine. I would rank this as a lower priority.

 

2. Mount upgrades are always a good idea. People on here in particular will suggest that you do the mount before anything else. Not sure that I personally agree in this case, see suggested #4.

 

3. Dedicated astro cameras are great but your Sony is very capable. I would also rank this as a low priority in the immediate future.

 

4. From what you describe here I would start with optics, probably a Rokinon/Samyang 135mm f/2. Your kit lens is by far the biggest limitation of your current setup and zoom lenses in general are not recommended for AP. You could also look into a small refractor but that will probably require autoguiding as well, so it's a bigger investment. 


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#3 DeepSky Di

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Posted 06 August 2022 - 06:48 PM

I added a guiding system to my DSLR and Star Adventurer first, then got a goto mount, telescope and ASIAIR Pro and used the same guiding system with that. I have used the same guide camera with an OAG. 


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#4 robert.ryan

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Posted 06 August 2022 - 06:53 PM

1. Autoguiding will yield a significant improvement in your potential exposure times, but I would encourage you to pay more attention to total integration time than the length of your individual subs. As long as you're able to hit a 1/4 to 1/3 histogram at a reasonable ISO that's fine. I would rank this as a lower priority.

2. Mount upgrades are always a good idea. People on here in particular will suggest that you do the mount before anything else. Not sure that I personally agree in this case, see suggested #4.

3. Dedicated astro cameras are great but your Sony is very capable. I would also rank this as a low priority in the immediate future.

4. From what you describe here I would start with optics, probably a Rokinon/Samyang 135mm f/2. Your kit lens is by far the biggest limitation of your current setup and zoom lenses in general are not recommended for AP. You could also look into a small refractor but that will probably require autoguiding as well, so it's a bigger investment.

I’ve got 50 minutes of integration time. I was under the impression that longer subs would capture a lot more faint details. But it sound like you’re suggesting that the difference between many short subs and equivalent integration with longer subs is not going to make the difference that I had hoped it would.

Likewise, I was thinking that the elimination of the IR filter would help a lot, but I hear you saying that if you’ve got enough integration, it’s not as big of a deal as I thought it would be.

Re the glass, yeah, I agree. A refractor is where I want to go. But to get comparable focal length, that seems like means a mount (and possibly guiding, too). Seems to get expensive quickly…

But thanks for all of the feedback!

Edited by robert.ryan, 06 August 2022 - 07:31 PM.


#5 robert.ryan

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Posted 06 August 2022 - 08:39 PM

I added a guiding system to my DSLR and Star Adventurer first, then got a goto mount, telescope and ASIAIR Pro and used the same guiding system with that. I have used the same guide camera with an OAG. 

I’m leaning towards this. Minor investment, minor improvement, but can leverage it later.



#6 mehresman2

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Posted 07 August 2022 - 08:37 AM

This seems to be a question with no "right" answer. Conversely, I think that because all three of the things you mentioned will undoubtedly help your images there is also no "wrong" answer.

Because of this, I think that so long as you go quality, you won't regret whichever choice you make.


___

As for my opinion:


1. Autoguiding is great. It's relatively cheap and it's a immensely helpful skill that you'll use for a long time without the potential *need* for an upgrade. Even if you chose to "upgrade" and do OAG, you can still use the camera you purchased to do so. So, it's moderately future proof.

However, it should be noted, that if you re currently using an intervalometer to take subs, this will mean that you will need to start using a computer during your sessions, which, depending on your route, could also necessitate other purchases like a miniPC, Pi, or ASIAIR (though I''m not sure if this can control a DSLR).

2. I don't think that you've come anywhere near maxing out the potential of your mount, so why upgrade?

 

That said, I do seem to be in the minority here, because I love my star tracker. I love spending time outside at night (after a long day and the kids are in bed) trying to star hop to find some faint nebula; that's part of the joy I get from this hobby. If that's not you (and I know a lot of people don't like this struggle), perhaps the goto capabilities of a bigger mount is worth the expense of upgrade. But purely in terms of tracking performance, for 30 second frames on a DSLR, with a lens, and even accounting for the weight of auto guiding equipment your star tracker is more than capable of that task.

3. For me, moving from an unmodded Canon 450D to an ASI533mc-pro was the most significant single-day upgrade I've ever made.


I went from this:

52267370167_2b16044b14.jpg20220723-282_8hr_7min ps by matt e, on Flickr


to this:

52268351538_afb593d13f.jpgFinal_Starless_8.74hr_North_America (1 of 1) by matt e, on Flickr

For you, however, I don't know if the difference will be as stark. Your camera is much better than mine was (looking at astrobin, there are some really nice shots).

 

That said, you will certainly see an upgrade in noise reduction if you go cooled and start letting all that Ha in.

4. Cmanley134 brought up the point that you may want to consider upgrading lenses, I can vouch for the awesomeness of the Rokinon/Samyang 135mm. It's a great lens that seems built for astro. Plus, it's wide field will allow you to get longer subs (if you want) without trailing (I *can* get 4 minute subs on my Star Adventurer+ guiding. Though, with light pollution and star bloat, I usually stick to 2).

____

Again, I don't think there's a wrong choice here. Each of these requires a learning curve and each will certainly improve your images.


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#7 cmanley134

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Posted 07 August 2022 - 12:19 PM

I’ve got 50 minutes of integration time. I was under the impression that longer subs would capture a lot more faint details. But it sound like you’re suggesting that the difference between many short subs and equivalent integration with longer subs is not going to make the difference that I had hoped it would.

Likewise, I was thinking that the elimination of the IR filter would help a lot, but I hear you saying that if you’ve got enough integration, it’s not as big of a deal as I thought it would be.

Re the glass, yeah, I agree. A refractor is where I want to go. But to get comparable focal length, that seems like means a mount (and possibly guiding, too). Seems to get expensive quickly…

But thanks for all of the feedback!

50 minutes of integration time is really not a significant amount - try capturing at least 3-4x that on one target and see where that gets you before you consider a camera upgrade. Regarding subexposure times, there are arguments on both sides as to whether shorter or longer subs are better. The important thing to remember is that long subs do NOT guarantee more detail in the final image. People get obsessed with this when in reality you can produce an image of roughly equivalent quality with short subs.

As for the possibility of the refractor you should be good up to about a 70mm scope on the Star Adventurer/Skyguider Pro, assuming you have guiding. This would include a lot of popular options such as the Redcat 51, Astrotech AT60ED and others. You could go for the guiding setup first and then for a wide-field scope, but the Rokinon/Samyang will yield immense improvements in your image quality now with that fast focal ratio. Up to you as far as what you choose, just my 2 cents.


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