Lens for wide field astrophotography

[astrotripper]

Hi everyone,

I recently dipped my toes into astrophotography. I decided to start simple, with wide field shots using fixed tripod, and switching to tracked shots when I get a drive for my telescope. But after few tries with the tripod, it's now clear to me that I need a proper lens for that.

I've been browsing internet auctions for used lenses up to 35mm (and maybe something around 55mm), but there's a lot of that out there. I've been digging through them past few days and found this forum very useful to find info on some of my finds. But after all that, my head is spinning and I feel that I'm more stupid now than I was before all this. I could seriously use some advice from more experienced folks.

I use Sony A200 DSLR for shooting (it's not even mine, I just borrow it from my bro), but I'm planning to move to Pentax K-5 in the future (when I can afford it )

What I have

Sony's kit 18-70 lens
- useless, as far as I tested, it's not possible to get a really sharp image at infinity
- focusing it without a live view is a real pain
- and it folds slightly when pointed upward

Auto Revuenon 1.4/55
- completely useless wide open
- has to be stopped down to f/5.6 for acceptable results
- I found f/8 to be the best match for it
- 55 mm is a bit too much, can't use longer exposures, as star trailing becomes visible quite fast

Mir-1B 2.8/37
- not usable wide open
- it gives me strange "halos" around bright stars, that's ruining the photos, noticed too late, so I haven't had a chance to test what happens when stopping it down even more, I also have a second one, so I'll be checking it as well for comparison

Industar-50-2 3.5/50
- I have not tested it for astrophoto yet (clear skies are sparse around here at the moment)
- but 50 mm is a bit to much

What I need

- something in 28-35 mm range
- that will not ruin me, my budget is rather tight
- M42 mount preferred, as I plan to use those in the future with Pentax (with appropriate adapter of course), I guess M39 is ok too, since M39->M42 adapters are cheap
- reasonably bright, I don't expect cheap lens to perform well wide open, but something that needs to be stopped down to f/8 to be sharp does not cut it for me (I'm guessing I should be happy with something sharp in f/3 - f/4 range?)
- sharp at infinity
- chromatic aberrations under control (so it could be fixed when converting from RAW)
- vignetting is not a concern
- corner sharpness does not have to be perfect or even very good, as those parts of the photo do not end up in the final image (A200 has a serious amp glow issue at corners, so they're ruined anyway)

I would appreciate any pointers as to what to hunt for. Any advice will be appreciated.

Thanks in advance.

[simbon4o]

Wide angles are hard to be found with good quality from the years of M42 lenses. So it will be quite difficult to find a good one.
Pentax wides are not the best but M 28 3.5 and M 28 2.8 II are nice ones. The bad news is that they are K bayonet. The 3.5 version is very good at F11 even in extreme corners on APS-C 16Mpix matrix. The M 28 2.8 II or A 28 2.8(they share the same lenses) are good at wider apertures. Both can't compare with Nikkor 28 2.8 which is much better .
My point is that wide lenses are getting better in years and I think that it will be better if you start to save money for modern zoom like Tamron 17-50 2.8 instead of trying to find good budget fix focal length lens.

PS the good thing about pentax and shooting stars is that if you can afford the GPS module, your camera can trace stars by using the image stabilization module, so you can use tele lenses too.

[visualopsins]

Welcome astrotripper

Try fast 50mm or 55mm! Here is M42 SMC Takumar 50/1.4 & 55/1.8 examples: http://forum.mflenses.com/starfield-compare-m42-asahi-smc-takumar-1-4-50-and-1-8-55-t41437.html

[ForenSeil]

All 50mm lenses I tried for astro-photgraphy didn't work really nice wide open. Corner-performance was never good enough wide open and many were not usable wide open at all.
A nice idea would be the Sony SAL50F18 (AF) - should be optically much better than all your other lenses and is very affordable with vey good center perfomance already wide open, but corners would be also not perfect wide open (visible vignetting below F2.8, extreme corner becomes almost perfect @ F5.6) and precise MF is a bit tricky with this lens.

Pentacon Six or Kiev 88 lenses might be also a way to go - they should have perfect corner performance (they are made for 6x6cm film!) on APS-C and they should be very easy to adapt on Sony Alpha or any other DSLR mount. They are not very fast though.

PS: Only for reference, here's a Minolta MD 50/2 wide open for example

(comaparable very good CA control but slightly bad corners and visible vignetting wide open)

And a Samyang 8mm F2.8 wide open (imo good astro-performance!)

[hifisapi]

the smc pentax - k 35mm f3.5 is an outstanding optic that should work for you but its K mount not m42 and sells for about $125

[simbon4o]

The great ~50mm lens for astro is Noct Nikkor 58 1.2, this is a lens made for shooting wide open and one of the purposes is astro. But the price is WOOOW

[astrotripper]

My main gripe with Nikkor and Pentax bayonet lenses is the need for an expensive adapter with corrective lens for Sony Alpha. So it's not only pricey, I'm kinda worried about loss of quality because of this additional lens. I might consider investing in such an adapter for Pentax lenses, since I'm planning to go all Pentax in the future, but I'd have to have a good reason for that. The same goes for alpha mount lenses, only the problem will be after I switch to Pentax.

So Pentax suggestions are welcome, I'll probably be hunting for such lenses when switching to K-5. But right now, M42 is preferable.

As for ~50mm lenses, it'd be great if I could find something that works at around f/2.8, any suggestions?

As for <35mm, I probably don't need a perfect lens. I really just want something that's decently sharp at infinity at around f/4. The problem I have is that there's quite a lot of them on the market and I really don't know which ones are total crap.

Some examples of what's available in my price range:
- Pentacon 2.8/29
- Auto Pallas 2.8/28
- Coslinar 2.8/28
- Petri 2.8/28
- Pentor 2.8/28
- Pentacon 3.5/30
- Exaktar 2.8/35
- Fodor 3.5/35
- Porst Weitwinkel 2.8/35
- Beroflex 2.8/35
- Albinar 2.8/35
- Carenar 2.8/35

In the ~50mm department, there's plentiful of Helios lenses in all varieties, lots of Pentacons, quite a lot of "aus Jena" and Zeiss, and some Tessar lenses.

[ForenSeil]

Hmm the Jena T(essar) 50/2.8 might be a good choice then.
Only F2.8 but decent correction, comparable good flat field and low vignetting as far as I know

PS: Try to avoid Helios 44 for astro- or any other more technical work. It's a decent lens for general photographic use but it also has a curved sharpness field and vignetting etc. at wide apertures,


Maybe you should buy an Sony NEX Body instead of a Pentax DSLR
You would automatically get maaany more really good and very cheap choices at this range
For example Canon FD 28/2.8 SSC, Minolta MD 28/2.8, Konica Hexanon 28/2.8 and all their 35mm counterparts and maaany more.

[JohnBar]

I recommend a 35mm cinema lens, something like an ISCO red or blue star HD lens. These can be found quite cheap on ebay and you probably could mount it at infinity focus inside a M42 extension tube and held with a few tapped bolts

Key advantages are

- designed to be very sharp at f2.0 with minimal abberation
- designed for long throw distances (infinity focus)
- excellent corner to corner sharpness

a wide lens is not so important these days with panoramic stitching software

NB something like this would be perfect

http://www.ebay.com/itm/ISCO-RED-f-37-5mm-ULTRA-STAR-HD-PLUS-1-85-MC-2-1-Projection-Lens-/321084278943?pt=LH_DefaultDomain_0&hash=item4ac21d489f

[buerokratiehasser]

A200 shouldn't be a big problem resolution-wise. (even compared to sensia)

Maybe you need lenses that go "a bit over" infinity so you can actually hit infinity (with tolerances etc.), otherwise it's F11 time. I heard people even tinker with their matsumotovs to allow beyond-infinity focus.

Or try various m42 adaptors. the hama adaptor is known for allowing infinity but not really due to mechanical problem of half a millimeter or something.

Generally, the wider the lens, the higher the suck*price ratio. UWW lenses for SLR are seriously expensive and not very good in the corners. Maybe it would even yield better results to use a primitive fisheye and straighten in software.

[hifisapi]

[astrotripper]

[cooltouch]

The sharpest 50mm wide open I've ever used was an old Leitz M39 50mm f/3.5 collapsible Elmar. Used to be you could pick them up for cheap, not so much anymore. But the Russian knock-offs are very good from what I understand, plus they're cheap. So I would seriously consider one of them.

[Arkku]

While wider than specified, the Samyang 14mm f/2.8 is one of the sharpest lenses wide open, e.g., sharper in the corners than pretty much any 50mm (including Zeiss) at f/2.8 and very little coma (especially on APS-C). But needs live view to focus, infinity stop is not precise enough and very hard to see exact focus through a traditional viewfinder with a lens this wide…

[Aanything]

[sammo]

I recommend a Canon DSLR for astro work. They are widely accepted because their RAW files are really raw without any processing (at least some years ago it was so), which is important for more serious astro work. There are also filter modifications available for Canon cameras, so that the camera is able to detect the red colour of the nebulae.

About the lenses, it's different criteria for astro work then for daylight. Especially because there is no stray light present. I have an Admiral 28m f2.8, that is useful at 2.8, good at 4 and very sharp at 5.6 on APS-C. But for daylight photography is not really so good (too low contrast and flare, even if it's sharp).
One of the best lenses for wide astro is probably Nikkor AIS 50mm f1.2. Mine is acceptably sharp at f2.0 on APS-C camera, only two corners are not perfect (strangly, two are sharp - maybe there is a small issue with the adapter) and very very sharp at f2.8.
Here is a photo that I took with the Nikkor at f2, first the whole frame, then 100% center crop and 100% lower left corner (the least sharp part of the image). Some of the center sharpness was compromised for better corner sharpness, all is a lot better at f2.8. ..but, anyway this here is more than enough sharpness for a 60x40cm print.





And +1 for Samyang lenses for astro, I have no experience yet, but for what I read people are very satisfied with them. I read one guy's blog who exchanged his 24mm f1.4 L II for Samyang, the Samyang was waaay better for astro then the mighty L.

[ForenSeil]

[sammo]

Sorry, I did not know what's the situation now, that's why I wrote a few years ago.

[visualopsins]

Good to know that about earlier cameras -- thanks sammo

[cooltouch]

Hey Sammo, are those single exposures or are you doing some of the image stacking stuff that a lot of astrophotographers are doing nowadays? I ask because you got a lot of good color in those images. The reds and blues are coming through very nicely.

Also, in the first photo, that star cluster in the top right quadrant, that's the Pleiades, isn't it?

[sammo]

[s58y]

[astrotripper]

[sammo]

[s58y]