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01-13-2022, 02:41 PM   #1
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Need suggestion for reasonably priced Astro lens

I want to purchase a wide angle, something in the F1.8 range for Astro photography, but don't want to spend $700 on the Pentax 31mm.

Anyone have any suggestions for an older Pentax, or 3rd party lens that works well for Astro?

TIA!!

01-13-2022, 02:44 PM   #2
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I don’t own it myself but the 24mm F1.4 Samyang/Rokinon/Bower is highly regarded among astrophotographers.

Samyang 24mm F1.4 ED AS UMC Lens Reviews - Samyang Lenses - Pentax Lens Review Database
01-13-2022, 02:46 PM   #3
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QuoteOriginally posted by 87Duckfan Quote
I want to purchase a wide angle, something in the F1.8 range for Astro photography, but don't want to spend $700 on the Pentax 31mm.

Anyone have any suggestions for an older Pentax, or 3rd party lens that works well for Astro?

TIA!!
You should give a little more info for solid advice: What sensor format, what angle of view are you looking for? I'm using the 31Ltd on the K-1 occasionally for astro+landscape shorts, but it's anyway not an ideal lens for that. Most of the wide-angle Samyangs are fairly to very good for astro, so pick one that of interest to you and check for samples/comments on astro use.
01-13-2022, 02:51 PM   #4
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How wide? Recommended lenses for astro and planetary photography - PentaxForums.com

01-13-2022, 03:06 PM   #5
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Not sure i need ultra wide.

Thoughts on this lens:
Sigma 30mm F1.4 EX DC HSM
01-13-2022, 03:33 PM   #6
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According to at least one astro site the Rokinon 14 2.8 is the best astro lens.
01-13-2022, 03:35 PM   #7
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for "wdie" astro lenses I fairly recently go the old SMC K 35/2 and found it to be a really good astro lens and is really good at f/2.8. I also have the A 28/2.8 and K 30/2.8 both of which I haven't given a full proper test to but a first sniff seems to indicate they are pretty good once they get to f/4. Beyond that the question becomes what do you want to shoot as one starts possiably wandering into more exotic things like the Laowa 12mm f/2.8 Zero-D (great astro lens or at least for me it has been). For astro a 50mm on APS-C will fit the body and head or Orion in the frame so is really wide so shooting any of the pentax fast 50s from the S-M-C 50/1.4 Takumar on up at f/2.8 produces really good results, and even the fat 50 (A 50/1.2) does as well. With the Samyang/Rokinon ultrawide lenses they do have quality control issues so getting one that isn't decentered may take some effort and in astro decentering will show in spades.

01-13-2022, 04:32 PM   #8
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QuoteOriginally posted by MossyRocks Quote
With the Samyang/Rokinon ultrawide lenses they do have quality control issues so getting one that isn't decentered may take some effort and in astro decentering will show in spades.
I must have been very lucky. Both my 12mm/2.8 fisheye (bought new) and the 14mm/2.8 (used) perform perfectly well wide open, my old 8mm APS-C FE not so much though, but I never expected it to. The stereographic fisheye projection is actually very useful, both for panos and for only partially de-fished landscape+macro work, because it doesn't stretch stars in the edges as much as regular (rectilinear?) ultra-wide lenses do. That said, in general Samyang lenses are designed for low coma, for which you will need to stop down most older Pentax lenses quite a bit.
01-14-2022, 02:52 AM   #9
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Sounds like some pretty fast lenses. I always assumed that you didnít shoot wide open because you were using long exposures and/or stacking.
01-14-2022, 07:07 AM   #10
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You still do :-)
01-14-2022, 08:59 AM   #11
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QuoteOriginally posted by Lhorn Quote
Sounds like some pretty fast lenses. I always assumed that you didn’t shoot wide open because you were using long exposures and/or stacking.
For all my astro shots I still do as long of exposure as I can and also stack even using fast lenses. Stopping down for astro is not done for increased depth of field but to correct optical problems since from the lens's perspective is at infinity. I believe my last Milky Way shot was 30x20s at f/2.8 with my 12mm f/2.8 lens.

QuoteOriginally posted by JensE Quote
I must have been very lucky. Both my 12mm/2.8 fisheye (bought new) and the 14mm/2.8 (used) perform perfectly well wide open, my old 8mm APS-C FE not so much though, but I never expected it to.
That is great. I'm not sure how common it is but it happens common enough that I am aware of people having to return lenses to get a good copy. Since problems tend to get reported while cases where there aren't don't there is probably a fair amount of selection bias there however it doesn't seem to be a super rare problem. Decentering seems to be more of a problem with UWAs than other lenses and even the Laowa I have has had reports of decentering from the factory but that appears to be less common although some of that may be because the lens doesn't sell as many copies but I'm just guessing with that. The really nice thing about modern UWA lenses is that they have resolved most of the issues that old ones had so one can actually run the wide open unlike my old S-M-c 17/4 fisheye Takumar which only starts to get not awful for astro at f/8

The somewhat sad thing about astro shooting is that throwing gear at the problem very often is the right solution so it does become hard to not suggest getting a better lens, tracker, new body, etc. to get better results.
01-14-2022, 09:38 AM   #12
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QuoteOriginally posted by MossyRocks Quote
I'm not sure how common it is but it happens common enough that I am aware of people having to return lenses to get a good copy.
It's definitely advisable to obtain them from a reliable source with a robust return policy. For the used one, I knew good sample pictures, so that was a low-risk purchase.

For the use of the 12mm FE for astro-landscapes, I discussed the process in Fisheye Fever Club -- Flaunt your fisheye photos! - Page 252 - PentaxForums.com. I bought the lens prior to a trip to the north with the hope of capturing some northern light shots (got plenty). The interesting structures don't last very long, so a fast lens is key. But as you can see in Pentax DA 35mm f/2.4 on a k1? - Page 2 - PentaxForums.com, even a simple F50/1.7 has been used to a great effect, which takes me back to the thread subject: Depending on what you want to photograph, an FA35mm/2.0 may be all you need and is a very good lens to have on APS-C anyway. Even the derived DA35/2.4 will perform well and be a very inexpensive way to get going. After a while, you'd know whether your lust is after more light or wider angles first.

I really need to make an effort to get to some dark interesting places this winter, it feels like I haven't taken any astro shots in ages. Or at least get my (increasingly ineffective due to white light) light pollution filter out.


One lens which I did not find to perform very well for astro is the F28/2.8. It's a more complex design that the FA28/2.8, which uses an aspherical lens instead, and usually praised over the later lens for general photography. For astro shots however, I still had to stop it down to at least f/4 for an acceptable rendering of stars in the corners. Similarly, even the DFA15mm-30mm monster needs to be stopped down a bit, similarly the 31mm Ltd (to ~f/2.8). So the ability to use the samys wide open already is was definitely worth the potential hassle to hunt for a good one.

Last edited by JensE; 01-14-2022 at 09:44 AM.
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