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bokchoy ninja

What can I capture with a 180mm lens and DSLR?

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Hello, I'm eagerly getting into AP. I picked up a star adventurer, and plan to use it with my Nikon D7100 dslr along with a 14mm lens for wide angle shots and a 180mm FL lens for DSOs.

What I'm a bit unsure of is: my longest lens, the 180mm FL, is in reality not *that* long. I see a lot of people with dslr/lens setups using 600mm focal lengths, which to me seems a bit untenable with the SA due to weight and tracking accuracy limitations.

With my setup (and currently no autoguiding), what can I realistically aim to achieve in terms of objects imaged?

And what would be the "next step" in terms of getting even better images? Autoguiding? Longer lens? A lightweight refractor telescope mounted to the SA? New mount entirely (this would have to wait a while)?

Thanks for the help!

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A great deal, there are some very large DSOs up there. The shorter Samyang 135mm f2 has quite a following, there is a thread full of example images here. Most of the large targets are nebulae, is your camera modded?

Here's an example image at 135mm with a modded DSLR, with an Ha layer blended in which really helped with the fainter nebulosity.

1908082758_RosetteandConeHaRGB900.JPG.2034e5f0f5c7748732ac8bf5bf0d193a.JPG

Edited by Knight of Clear Skies
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That setup is fine to capture lots of stuff I wouldn't be to quick to start spending money until you've had a bit of practice with what you have.

The UK weather ( if you're in the UK) is the main constraint on imaging anything so no shortage of targets.

Dave

Edited by Davey-T
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8 minutes ago, Knight of Clear Skies said:

A great deal, there are some very large DSOs up there. The shorter Samyang 135mm f2 has quite a following, there is a thread full of example images here. Most of the large targets are nebulae, is your camera modded?

Here's an example image at 135mm with a modded DSLR, with an Ha layer blended in which really helped with the fainter nebulosity.

That's a fantastic photograph, thanks for the reply. Looks like I might be OK with the 180mm, then. Do you think I can get good results without guiding, on the SA? Or should I try to incorporate that into my workflow soon?

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1 minute ago, Davey-T said:

That setup is fine to capture lots of stuff I wouldn't be to quick to start spending money until you've had a bit of practice with what you have.

The UK weather ( if you're in the UK) is the main constraint on imaging anything SO no shortage of targets.

Dave

Right on, thanks for the reply. I'm in San Diego, so the only limitation is light pollution (spotted out a couple of dark areas that I can plan on visiting on the weekends, though). You don't think I need an autoguider for the star adventurer to get good results?

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As to a list of targets that you can get with a sub 200 mm focal length lens I would say all of them, the big gain with shorter focal lengths is that you get to see the relative positioning of separated objects...

Alan

Edited by Alien 13

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I've never bothered to guide my Star Adventurer it can manage a couple of minutes with a 300mm lens  and pretty much open ended with 24mm.

Dave

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36 minutes ago, Davey-T said:

I've never bothered to guide my Star Adventurer it can manage a couple of minutes with a 300mm lens  and pretty much open ended with 24mm.

Dave

That's pretty impressive!

Alright, now I'm pumped.

Within two hours from where I live, the best sky I can access is a Bortle 4. Is that dark enough to get good results?

Edited by bokchoy ninja

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Yes fine, the main problem with DSLRs is that the continuous shooting needed means that there is heat generated in the camera which becomes noise in the image, there are various ways to mitigate this such as pausing between shots to cool a bit and trying to take what are called dark frames to calibrate your images but don't get too hung up on the technical side of things just have a go and see what you can get.

Dave

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9 minutes ago, Davey-T said:

Yes fine, the main problem with DSLRs is that the continuous shooting needed means that there is heat generated in the camera which becomes noise in the image, there are various ways to mitigate this such as pausing between shots to cool a bit and trying to take what are called dark frames to calibrate your images but don't get too hung up on the technical side of things just have a go and see what you can get.

Dave

Cool, thanks for the advice. I'll be sure to include a pause between exposures. 

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7 hours ago, bokchoy ninja said:

That's a fantastic photograph, thanks for the reply. Looks like I might be OK with the 180mm, then. Do you think I can get good results without guiding, on the SA? Or should I try to incorporate that into my workflow soon?

Thanks. The image above was taken unguided, using 2 minute subs. However, it's about 3 hours of data at f2 (2h20m RGB and 45m Ha) with an (old) modded DSLR, and took quite a bit of processing to get to that point. If your camera isn't modded the Pleiades would be a great target at 180mm.

7 hours ago, Davey-T said:

Yes fine, the main problem with DSLRs is that the continuous shooting needed means that there is heat generated in the camera which becomes noise in the image, there are various ways to mitigate this such as pausing between shots to cool a bit and trying to take what are called dark frames to calibrate your images but don't get too hung up on the technical side of things just have a go and see what you can get.

Dave

I don't bother to take darks for my images, as I suspect that if the temperature profile doesn't match the lights it's likely to introduce noise rather than reduce it. I also don't cool the camera between subs, I just give it 5 seconds or so, I've very skeptical that doing so is worthwhile in most cases. However, I do take bias frames. As you say, it's best not to get too hung up on technicalities to begin with.

Imaging is something of a learning curve, I made quite a lot of mistakes when starting out but still got worthwhile results. 

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