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FORUMS Photo Sharing & Visual Enjoyment Astronomy & Celestial
Thread started 03 Aug 2017 (Thursday) 23:12
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lenses for Astrophotography advice please

 
ctvu
Member
35 posts
Joined Apr 2014
Aug 03, 2017 23:12 |  #1

Hi All,
Hope I post right forum, if not admin please remove or move it.
I am looking for a lens for my Sony A7R II, I have done a lot of homework as well as read blogs (Ian Norman - Lonely Speck).
what I am thinking of is:
Zeiss Batis 18mm
Samyang/Rokinon 14mm, 24mm.
Samyang 14mm f2.4
or what else would you suggest?

Cheers,




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01Ryan10
Senior Member
Joined Aug 2012
OC, California
Aug 04, 2017 11:11 |  #2

I've used the following with my 6D:

Rokinon 24mm F/1.4 - I bought my first copy used, and it had some noticeable blur on the edges and corners. I wanted to love this lens, but sold it to my cousin for $300. He accepted the issue. I then bought a second copy from Amazon on "Prime" day for $415. This copy is the business. Unbelievable sharpness corner to corner. I guess I got lucky as Rokinon's are known for hit and miss quality.

Rokinon 14mm F/2.8 - I had one copy that was very sharp. I sold it thinking I would get a 16-35mm F/2.8 MKIII, but I decided not to get the 16-35mm. I am now sad I don't have it. I will buy another one early next year for MilkyWay panoramas.

50mm F/1.8 STM - I tried this lens for a few shots last weekend just to see what it would look like. The center was stunning. The 1/3 edges and corners were terrible. lol. Massive coma and swirling.

35mm F/2.0 IS - This lens was quite surprising. Most of the image was as good if not better than the Rokinon 24mm that I currently have. The corners have borderline too much coma. I'd say 85% of the frame is sharp and fantastic though.

16-35mm F/4 IS - Basically same as my 35mm F/2.0 IS. I used this on an iOptron Startracker Pro. Great images actually. I'll use it more.

85mm F/1.8 - lol...laughable MilkyWay size compared to horizon. The quality was like my 50mm. Kind of terrible. If I hook up to my iOptron, I'm sure I can stop down to F/5.6, and clean up the coma and quality of the image for some interesting MW perspectives.


Overall...My current Rokinon 24mm is a dream. Loved my Rokinon 14mm too. Going to repurchase.


Some other lenses to consider are the Sigma ART lenses. I've read that like my 35mm F/2, 85%-ish of the frame is spectacular. The corners have a little coma, but not too much.


http://RyanLunaPhotogr​aphy.com (external link)
IG: @01ryanluna10 (external link)

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MalVeauX
"Looks rough and well used"
MalVeauX's Avatar
Joined Feb 2013
Florida
Aug 04, 2017 11:40 |  #3

ctvu wrote in post #18418813 (external link)
Hi All,
Hope I post right forum, if not admin please remove or move it.
I am looking for a lens for my Sony A7R II, I have done a lot of homework as well as read blogs (Ian Norman - Lonely Speck).
what I am thinking of is:
Zeiss Batis 18mm
Samyang/Rokinon 14mm, 24mm.
Samyang 14mm f2.4
or what else would you suggest?

Cheers,

What do you want to photograph?

Widefield basically? Are you wanting to incorporate foreground & sky together in one shot? Or are you wanting to focus mainly on DSO?

I will recommend a tracker over any particular lens for astrophotography. It opens more doors in the long run. And is less than a "fast" lens that really isn't necessary at all.

If you want foreground & galaxy/widefield in one shot, get 14~16mm.
If you want mostly just the galaxy core/widefield and care about coma, get the Rok 24mm.

Very best,


My Flickr (external link) :: My Astrobin (external link)

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ctvu
THREAD ­ STARTER
Member
35 posts
Joined Apr 2014
Aug 05, 2017 10:07 |  #4

Thank you very much both.
Ryan, I have been using 16-35 F4, it is OK for start, but in corner I found stars start streak when >20s. I got Sony 55mm 1.8 but I could not get in focus, I shall try again next new moon.
MalVeaux,
For the start, I want foreground and sky, later may focus on DSO. Thanks for suggestion of tracker. In fact I have been doing homework on a tracker, as Ryan mentioned iOptron Skytracker Pro.
I am thinking of iOptron Skytracker Pro, Skyguider Pro, or Starwatcher Star adventure, since I am a newbie, any recommendations on them or something else?

Cheers




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MalVeauX
"Looks rough and well used"
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Joined Feb 2013
Florida
Post has been last edited 2 months ago by MalVeauX. 2 edits done in total.
Aug 05, 2017 10:54 |  #5

Heya,

All those trackers are fine in the $300 range. I would lean more towards the Star Adventurer myself due to what all else can be done with it long term. But its a tit for tat type thing. They're all pretty good for what they are and especially at the cost, it really does open doors. You have people that buy insanely high priced lenses for "aperture" only to find out they're still land locked to 30 seconds or less pretty much no matter what without a tracker. And a tracker removes all that cost (you don't need a $1k+ lens, a cheap $50 prime will do an amazing job on a tracker). Time is no longer a huge limit and you can expose for 4 minutes or more if you really want to, at lower ISO, and with smaller apertures (which is actually better anyways for star shape, coma, etc control).

Now that said, a tracker will be moving, so you cannot do a foreground and sky exposure in one exposure from the tracker for a long period of exposure time (in minutes) because the foreground will of course be a moving blur, while the sky is frozen in time. Those will be composites where you expose the foreground, then use the tracker and expose the sky and do a composite of the two.

Or, if you want to only do foreground+sky, you can do it with the widest FOV focal length you can get and no tracker to do it with one exposure and light paint the foreground.

++++++++++

I used the iOptron SkyTracker for a while, great little device.

IMAGE: https://farm8.staticflickr.com/7429/14076981462_358901f129_z.jpg
[IMAGE'S LINK: https://flic.kr/p/nrWd​9W] (external link)20140501_053133 (external link) by Martin Wise (external link), on Flickr

Here's a single 4 minute exposure at ISO 400 from that, no stacking, no extra stuff, just the glorious signal level you get from filling pixels with exposure time:

IMAGE: https://farm8.staticflickr.com/7368/13031754273_052f0b9929_z.jpg
[IMAGE'S LINK: https://flic.kr/p/kRz9​wv] (external link)DPP_0791 (external link) by Martin Wise (external link), on Flickr

Time is far more important than focal-ratio. That was with a 35mm F2. Looking back, I should have stopped it down to F4 actually to address the coma which can be seen around the edges (this is an uncropped frame). But the point was to see how accurate 35mm on APS-C would track for 4 minutes and those are pin-point stars. Realistically I should have done it at F2.8 and ISO 800 or F4 and ISO 1600 due to the read/write noise of the sensor tier (650D). These days I don't use anything less than ISO 800 and commonly use ISO 1600 for my DSO stuff with that sensor, even though I can expose for 10+ minutes no problem on my current tracker (HEQ5 or Orion Sirius), but I image at F6 these days with scopes rather than camera lenses anymore as my interest moved to specific DSO's.

Now to give you an example of why you cannot do a long exposure sky shot with a tracker, and incorporate the foreground, here's an example. The foreground was not cropped out to show how it will blurr from motion and you have to do a composite. If composites don't bother you, then you're fine. But some people don't want to fool with that and would rather get the exposure in one shot with a really wide lens, and that's fine. But just again to illustrate the point of needing to do a composite:

3 minutes of exposure time in a single image; foreground blurred of course due to the rotation.

IMAGE: https://farm3.staticflickr.com/2520/13007290245_4a24a20363_z.jpg
[IMAGE'S LINK: https://flic.kr/p/kPpL​dV] (external link)DPP_0776 (external link) by Martin Wise (external link), on Flickr

++++++++++++

And if you dive into the rabbit hole deeper, you end up really getting into zaney exposure times.

These days, I do it with a short telescope, dSLR, and a much beefier tracker:

IMAGE: https://farm1.staticflickr.com/584/33030734791_6f3873681f_z.jpg
[IMAGE'S LINK: https://flic.kr/p/SjP9​Fr] (external link)IMG_5106 (external link) by Martin Wise (external link), on Flickr

Here's 2 hours at 480mm F6 on an APS-C:

IMAGE: https://farm1.staticflickr.com/629/33104332301_b5fc062350_z.jpg
[IMAGE'S LINK: https://flic.kr/p/Srjm​E2] (external link)M42_02282017 (external link) by Martin Wise (external link), on Flickr

Very best,

My Flickr (external link) :: My Astrobin (external link)

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Kevin ­ B
Senior Member
289 posts
Joined Aug 2009
Albuquerque, NM
Aug 05, 2017 17:08 |  #6

Sigma has a new 14mm f/1.8 that was just released that pending reviews will be another alternative you may want to consider. Rokinon also has a relatively new 14mm f/2.4 that is supposed to be part of a premium line which should be better than the original 14mm f/2.8. At the end of the day, many people use the Rokinon 14mm f/2.8 very successfully and you can't beat the price.

Good luck!


GEAR: 5D Mark III, 7D, 24-105L, 16-35 F/4L, 50 f/1.4, 100-400L II, 100 f/2.8 macro, Zeiss 21mm f/2.8, 1.4X III

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ctvu
THREAD ­ STARTER
Member
35 posts
Joined Apr 2014
Aug 05, 2017 21:49 as a reply to MalVeauX's post |  #7

Hi Martin,
Your post really opens my eyes, deep information with illustrated WOW photos. Really appreciated your time and helpful information.
you mentioned

35mm on APS-C would track for 4 minutes and those are pin-point stars

that means you can track more than 2 mins (120 seconds) according to my research we could track 2 mins with roughly polar alignment, since I am living in South Hemisphere, not too sure we can do a proper polar alignment.
The last photo is really inspiring, definitely I shall dive in the deep rabbit hole and my bank account if my path is DSO.
Cheers




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ctvu
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Member
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Joined Apr 2014
Aug 05, 2017 22:01 as a reply to Kevin B's post |  #8

Hi Kevin,
Thanks for the post. I have read some reviews on the new Sigma 14mm f1.8, I'd keep it in mind for sure, and you are right about

many people use the Rokinon 14mm f/2.8 very successfully and you can't beat the price

The more I read, the more I lean forward to this lens. As Martin's post above, if I have a tracker, then the cheap lens would still do a good job i.e. pinpoint star image.
Cheers




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MalVeauX
"Looks rough and well used"
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Joined Feb 2013
Florida
Aug 06, 2017 04:46 |  #9

ctvu wrote in post #18420278 (external link)
Hi Martin,
Your post really opens my eyes, deep information with illustrated WOW photos. Really appreciated your time and helpful information.
you mentioned that means you can track more than 2 mins (120 seconds) according to my research we could track 2 mins with roughly polar alignment, since I am living in South Hemisphere, not too sure we can do a proper polar alignment.
The last photo is really inspiring, definitely I shall dive in the deep rabbit hole and my bank account if my path is DSO.
Cheers

I never polar aligned my skytracker, I just pointed it roughly north (as I'm in the Northern Hemisphere), dialed in my latitude, and at wider angles, this is suffucient for long exposures like 4 minutes (at the angle produced by APS-C & 35mm; for a longer focal length, significantly longer, more precise alignment would be important for long exposure). You don't need proper polar alignment. You really don't need polar alignment at all. You can just use the drift alignment method (google that). The tracker ends up being positioned so that it's aligned with the "pole" of the axis of the Earth's tilt. As long as you're close, it'll work at wider angles for a few minutes.

That above 4 minutes is with a dirty alignment, as in, no alignment, I just pointed it North, dialed in my 29 degree latitude and it exposed.

Now, on my larger setup, I do plate solving alignment, but that's a total different beast.

Very best,


My Flickr (external link) :: My Astrobin (external link)

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mizouse
Senior Member
Joined Jan 2007
Bay area, CA
Aug 06, 2017 21:31 as a reply to MalVeauX's post |  #10

Hmm.. i think a tracker is going to be next on my purchase list :lol:


Canon EOS-1D Mark II N | Sony Alpha NEX-6 | Canon EOS 5D | Canon EOS 6D | EF 70-200mm 1:2.8 L USM | EF 24-70mm 1:2.8 L USM | EF 17-40mm 1:4 L USM | EF 50mm 1:1.8 STM | EF 40mm 1:2.8 STM | EF 35mm 1:2 IS USM | EF 24-105mm 1:4 L IS USM | 580EX II

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ctvu
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Member
35 posts
Joined Apr 2014
Aug 07, 2017 01:25 |  #11

MalVeauX wrote in post #18420379 (external link)
I never polar aligned my skytracker, I just pointed it roughly north (as I'm in the Northern Hemisphere), dialed in my latitude, and at wider angles, this is suffucient for long exposures like 4 minutes (at the angle produced by APS-C & 35mm; for a longer focal length, significantly longer, more precise alignment would be important for long exposure). You don't need proper polar alignment. You really don't need polar alignment at all. You can just use the drift alignment method (google that). The tracker ends up being positioned so that it's aligned with the "pole" of the axis of the Earth's tilt. As long as you're close, it'll work at wider angles for a few minutes.

That above 4 minutes is with a dirty alignment, as in, no alignment, I just pointed it North, dialed in my 29 degree latitude and it exposed.

Thanks for the post...are you serious about not proper alignment but still achieve 4 mins? perhaps you are in Northern Hemisphere. Southern Hemisphere is different story if go over 2 mins.
Cheers




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ctvu
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Member
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Joined Apr 2014
Aug 07, 2017 01:28 as a reply to mizouse's post |  #12

I am planning to get one of them, but it is hard to pick which one iOptron Skyguider Pro or StarWatcher Star Adventure Astro Package?
Cheers




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MalVeauX
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Florida
Aug 07, 2017 08:59 |  #13

Heya,

Yes, quite serious. But again that is due to the angle produced at only 35mm. That would have not worked out at 4 minutes at a much longer focal length. You can get away with a lot more time with a wider focal length. Even in the Southern Hemisphere. If you're using wide angle, you may find you can get even more time. But really, 2 minutes is sufficient. You shouldn't look to use low ISO, I was just making a point. Ideally you should use the ISO that is best for your read/write of your sensor (Clark Vision can help you with that, google him up). It's probably going to be around ISO 800 or higher. So two minutes is going to be plenty. It's vastly superior to 30 seconds or less at much higher ISO's. Time is where you get the highest signal amount from.

I would go for the Star Adventurer if I were going that way again. It's easy to use, has options to grow into more (guider port, counter weight option, etc, in case you get into DSO more and want to go with longer focal length and longer exposure time). I'd get the Adventurer + Wedge as a start.

Very best,


My Flickr (external link) :: My Astrobin (external link)

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ctvu
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Joined Apr 2014
Aug 07, 2017 16:13 as a reply to MalVeauX's post |  #14

Thank you Martin very much for everything, honestly I have read and researched a lot online info, but your answers/posts are so much helpful to me personally.

Cheers,




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bvalente
Hatchling
4 posts
Joined Aug 2017
Aug 07, 2017 16:21 |  #15

ctvu wrote in post #18421001 (external link)
I am planning to get one of them, but it is hard to pick which one iOptron Skyguider Pro or StarWatcher Star Adventure Astro Package?
Cheers

I own them both, i'd say right now the ioptron skyguider pro has an edge. It almost looks like they have identical designs. Ioptron benefits are built-in battery, bettery polar alignment scope setup and illuminator (StarWatcher's almost seems like afterthought). otherwise they are nearly identical


Brian


Brian
brianvalentephotograph​y.com

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lenses for Astrophotography advice please
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