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Is 480mm focal length to narrow for DSO?

Orion1

By Orion1
in Getting Started With Imaging

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John78

John78

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39 minutes ago, Orion1 said:

400mm seems to be a sweet spot with aps-c for the bigger objects I think.

Well yes and no, yes and maybe even a bit shorter for the large nebula - but - no because using a DSLR for nebula's is a challenging experience unless where you live is particularly dark.

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Orion1

Orion1

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20 minutes ago, John78 said:

Well yes and no, yes and maybe even a bit shorter for the large nebula - but - no because using a DSLR for nebula's is a challenging experience unless where you live is particularly dark.

What equipment do you use for astrophotography?

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geordie85

geordie85

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It all depends on what DSO's you'd like to image. If your going for planetary nebula such as the cats eye nebula then you'll want more focal length, as with most galaxies. 

If your wanting to image large nebula such as the north American nebula, the whole veil nebula and the likes, then you should be fine, but may still need to do a 2 panel mosaic to get some in their entirety. 

I like using this fov calculator 

https://www.blackwaterskies.co.uk/imaging-toolbox/

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ollypenrice

ollypenrice

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The universe doesn't give a damn about either our focal lengths or our chip sizes. If you have an idea about 'most DSOs' you have this idea because you are used to seeing certain popular targets in certain popular imaging system formats. One thing is certain: there are coherent structures out there which are far, far too big to be captured in any telescope in a single frame with any camera now available. 

Using our full frame cameras and 530mm focal length it would be easy to find plenty of targets needing 20 panel mosaics. There are big objects out there. And small ones!

Olly

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wimvb

wimvb

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Just as there is no single best daytime lens to capture "all" scenes, there is no single best focal length for astrophotography. Sure, large targets can benefit from a short focal length. But you can also go the other route, and isolate intricate details of large nebulae with a long focal length and/or a smaller sensor. This can give a new twist to common dso's.

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Orion1

Orion1

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I agree with you all. I’ve been using a 200mm lens for a while now for the biggest objects. I still like the sense of space around the objects, but I would like to get a bit closer for my next step up. I was set on 80/480 triplet but after toying with a FOV calculator I’m not so sure anymore...

I can tell you I’m definitely not ready to mosaic a nebula quite yet :)

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Orion1

Orion1

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1 hour ago, wimvb said:

Just as there is no single best daytime lens to capture "all" scenes, there is no single best focal length for astrophotography.

I know. But there a some lenses that are more allround than others like a 50mm.

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Orion1

Orion1

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2 hours ago, geordie85 said:

It all depends on what DSO's you'd like to image. If your going for planetary nebula such as the cats eye nebula then you'll want more focal length, as with most galaxies. 

If your wanting to image large nebula such as the north American nebula, the whole veil nebula and the likes, then you should be fine, but may still need to do a 2 panel mosaic to get some in their entirety. 

I like using this fov calculator 

https://www.blackwaterskies.co.uk/imaging-toolbox/

Thanks for the link. That FOV calculator is the best I've seen.

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wxsatuser

wxsatuser

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9 hours ago, Orion1 said:

I agree with you all. I’ve been using a 200mm lens for a while now for the biggest objects. I still like the sense of space around the objects, but I would like to get a bit closer for my next step up. I was set on 80/480 triplet but after toying with a FOV calculator I’m not so sure anymore...

I can tell you I’m definitely not ready to mosaic a nebula quite yet :)

Me neither, not enough time, to many clouds etc etc.

135mm on an APS-C sensor will cover a lot of large objects, many of the usual suspects plus a lot of Sharpless, LBN's and LDN's.
Plus there is one very affordable fast telephoto that will do the job with great efficiency, see my signature. :icon_biggrin:

It may not be everyone's cup of tea but if you have little time for whatever reason, this is the beast, especially for a quick fix. :icon_biggrin:

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Orion1

Orion1

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1 hour ago, wxsatuser said:

Me neither, not enough time, to many clouds etc etc.

135mm on an APS-C sensor will cover a lot of large objects, many of the usual suspects plus a lot of Sharpless, LBN's and LDN's.
Plus there is one very affordable fast telephoto that will do the job with great efficiency, see my signature. :icon_biggrin:

It may not be everyone's cup of tea but if you have little time for whatever reason, this is the beast, especially for a quick fix. :icon_biggrin:

The Samyang 135mm is a very sharp lens and is excellent for wide field dso. I’ve been climbing my way up from 18-55mm to 135mm and I’m now on a Canon 200mm f2.8 lens.

Telephoto lenses are good but the focuser is not very precise. I peronally need to use a bathinov mask to get the focus right.

I think I’ll stick with the 200mm for wide field and add a 80/480 triplet to get the smaller objects and get me closer to the big ones. I will also use it for visual.

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Pete Presland

Pete Presland

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11 hours ago, geordie85 said:

It all depends on what DSO's you'd like to image. If your going for planetary nebula such as the cats eye nebula then you'll want more focal length, as with most galaxies. 

If your wanting to image large nebula such as the north American nebula, the whole veil nebula and the likes, then you should be fine, but may still need to do a 2 panel mosaic to get some in their entirety. 

I like using this fov calculator 

https://www.blackwaterskies.co.uk/imaging-toolbox/

A very impressive website!

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Orion1

Orion1

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9 hours ago, geordie85 said:

I think so too, that's why I always use it. And you can pan around the sky to see what else is about.

This calculator helped me visualize the different focal lengths. I don’t think the 480mm is not that bad after all :) 

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wxsatuser

wxsatuser

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1 hour ago, Orion1 said:

The Samyang 135mm is a very sharp lens and is excellent for wide field dso. I’ve been climbing my way up from 18-55mm to 135mm and I’m now on a Canon 200mm f2.8 lens.

Telephoto lenses are good but the focuser is not very precise. I peronally need to use a bathinov mask to get the focus right.

I think I’ll stick with the 200mm for wide field and add a 80/480 triplet to get the smaller objects and get me closer to the big ones. I will also use it for visual.

The Canon lenses are reasonable but most don't come near the Samyang.
I have tried the 200mm f/2.8, only really very good stopped down and the 70-200mm f/2.8 IS II, good at 70mm but
at 200mm it's about the same as it's prime mate.

For precise focus a motor and software does the job.
My setup is just a Skywatcher focus motor, a small toothed pulley and a toothed belt around the lens focus ring.
Focus in Artemis Capture and can normally get near or under an FWHM of 2.


 

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