[Michael Piziak]

Well, not long ago I pointed my 55-300mm toward the brightest stars and you guys/gals helped me determine what was Jupiter/Saturn....

I recently started a thread on trying to determine all the fuss about the perhaps over hyped nifty fifty, and decided to put my only 50mm lens on my camera for a week or so and see what I can discover myself. It's the smc Asahi Pentax M-50mm Macro f4 lens.


Awaiting the moon to pop up tonight, I fired off a few shots of the night sky - shooting at the brightest star(s) which are probably planets.... Took the photos pointing southward - perhaps slightly south western in Eastern U.S. Sky...


1) Question 1: Any tips on ISO, shutter speed, and aperture? (I just realized I forgot to fiddle with the aperture at all and took all the shots at f4)....

2) Question2 : Is it possible for a very sharp 50mm lens to resolve, very distant objects in the night sky, almost as good as the Pentax 55-300mm lens? Especially when the 50mm is a sharp macro, like my lens is (my understanding is that macros are generally very sharp lens).

3) Question 3: Photo 4 is my first capture of Star Trails (at 30 seconds shutter speed). I need to read up on how to get a longer shutter speed than 30 seconds. Any quick tips on how this is done, throw the tips at me. I recall something about bulb mode, etc...


So, as I await the moon, any comments from astro photographer shooters of what I've captured here....

Click on any images 2 or 3 times to zoom in


Photo 1



Photo 2


Photo 3



Photo 4 - my first photo ever of Star Trails



Addendum: I have temporarily set permissions so anyone can download full file size images, so as to allow users to zoom in/download original files for maximum examination of photos...

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Last edited by Michael Piziak; 09-29-2021 at 09:49 PM.

[damianc]

A quick curves tweak of photo 2 shows the image is sharp across the field and there's little coma and CA. Some star trailing at 10 seconds which can be corrected with astrotracer or a telescope mount.
The image is under exposed, and using higher ISO (e.g 800) would allow you to capture more light and see more stars. Of course, this introduces more noise and the solution to that is stacking multiple images in software like Siril, or Deep Sky Stacker. I'd say F4 is good for this lens BTW

If you do follow up you do realise you're off down a very deep rabbit hole!

[steephill]

It is my understanding that increasing ISO does not allow you to capture more light, the amount of light you capture is entirely due to the combination of aperture and shutter speed.

[damianc]

Is the K-S2 iso invariant? You're right about no more light though, I should have probably phrased that better. Standard rule of thumb seems to be to get the histogram peak at about 25%-33%
One advantage of higher iso is that bad frames can be more easily spotted and eliminated from a stack

[UncleVanya]

I suggest reading on this site:
What ISO to use for astrophotography? – Professor Morison's Astronomy Digest

The basic article thrust is that iso invariant sensors can work well at low iso but there are specific optimizations for specific sensors you should look at.

[Bob 256]

There are different types of astrophotography which call for different lenses and different techniques. Usually the simplest and one for beginners is shooting star trails which can be accomplished with most any lens in the "normal" range (such as your 50mm) without a tracking mount. One just shoots a long exposure (bulb). To get best performance out of a lens, it's best to close it down a bit. Starting at f4 (your lens), that will limit the amount of light captured significantly so you probably should go wide open. Down the road, you might obtain a faster lens which will allow you to close it down and still have f2.8 or f4 and this will help with lens deficiencies. Wider lenses (lower than 50mm in FL) make great star trail photos also. Right now, that 50mm lens you have will work fine. It should do well in resolving stars for your present needs. (By the way, what camera are you using?)

When you want to go for objects in the sky like nebulae or planets, it's a whole different approach. You need tracked exposures to build up an image without the streaking you get with star trails. Some Pentax cameras have limited tracking (Astrotracer feature) but using a tracking mount can be even better. These are available from many astronomy outlets. They keep the camera pointed at the object you're trying to shoot for long periods of time (the downside is they can be difficult to set up correctly). At the same time, you will also need longer focal length lenses to zoom in on these objects. Your 55-300mm lens will most certainly work for many of these objects. Again, you have some competing requirements that have to be addressed. As you go to higher focal lengths, the tracking becomes more difficult and you will find it harder to get fast lenses you can afford (hence you compensate with longer exposures which require better tracking .................

That said, I would start as you have and get a feel for what exposures and camera settings are needed. Then I would probably go for a tracking mount. That's where it gets interesting because long exposures can reveal many things in the sky, even with 50mm lenses.

A lot can be done after a shot is taken (in post-processing) and that's a whole book in itself. Pace yourself and learn as you go and you'll find astrophotography is fun and rewarding.

https://products.bestreviews.com/best-star-tracker

[photoptimist]

50mm may be nifty for a lot of photography but it's an odd duck for astrophotography.

50 is too narrow for good shots of the Milky Way, meteor showers, and landscapes+starscapes. Those tend to need wider angle lenses somewhere in the range of 10mm to 20mm on APS-C. That said, a 50 could be used for landscape+starscape and Milky Way images by panoramic tiling but it takes a lot of careful work to get a good result.

50 is far far too wide for good shots of the moon, planets, galaxies, and nebulae. Those typically need serious telephoto lenses. For example, frame-filling shots of the moon needs a 1500mm lens on APS-C. Although nice shots of Andromeda galaxy can be done with lenses as short as 135mm, most shots of planets, galaxies, and nebulae rely much longer focal length lenses or telescopes.

50 can do fun star trail images. Putting the North Star in the frame creates a nice near-stationary pivot for the circling stars. Or, portrait-orientation shots with a horizon can get star trails rising/setting over the horizon landscape.

Otherwise, astrophotography typically requires expensive lenses (or telescopes) because astro needs lenses with the largest possible apertures AND the sharpest-possible edges and corners.

[MossyRocks]

1) Question 1: Any tips on ISO, shutter speed, and aperture? (I just realized I forgot to fiddle with the aperture at all and took all the shots at f4)....

Fairly high. Depending on what you are shooting and what tracking ability you have expect to run between ISO 800 and ISO 6400 dependent on shutter speed. For shutter speed you will be limited to your tracking ability, so if untracked use the rule of 200 which is 200/focal length gives you your shutter speed in seconds. So for a 50mm lens that would mean that you can get pretty good results with little to no trailing (location in the sky dependent) at 4 seconds. For aperture you want to run as open as you can. Without knowing your lens I don't know what that point is but for my 50mm lenses I get great results with my SMC A 50/1.2 at f/2 and with with my S-M-C 50/1.4 Takumar I get great results at f/2.8. You don't need to increase the f-stop to gain depth of field as everything in space is at infinity from your lens's perspective, yes eve the moon and even with the biggest lens you could hang the camera off. Getting proper infinity focus is key and there are focusing masks that can help you nail that every time.

If you have tracking ability then the exposure time can go way up. Off of my little equatorial I use 30s as I only have one intervaolmeter but a couple of other release cables so I just do 30s shots and set that thing and forget it for the evening. I also have the O-GPS1 and will use that on my K-3 with longer glass and there at 400mm I can usually get great 20s exposures of deep sky objects all night long every night I am out.

2) Question2 : Is it possible for a very sharp 50mm lens to resolve, very distant objects in the night sky, almost as good as the Pentax 55-300mm lens? Especially when the 50mm is a sharp macro, like my lens is (my understanding is that macros are generally very sharp lens).

Yes. For example here is a shot I did earlier this year using my K-3ii with the SMC A 50/1.2 and K-500 with the S-M-C 50/1.4 Takumar on the Cygnus region of the Milky Way showing the North Ameriacn Nebula and entire Veil Nebula. A 50mm on an APS-C camera will also frame up the parts of Orion with the most interesting features all at once like Barnard's loop, the Flame, Horse, Running Man, and Great Orion nebula along with the Witches Hat Nebula all at once. At 50mm Andromeda should show up clearly in your shots but will be small (about 6x the size in the night sky as the full moon) as well. With a 50mm lens expect to be shooting large things in the night sky so no Deep Sky Objects, but constellations, panos of the Milky Way, parts of the Milky Way, etc all work fine. Planets will be bright dots with bleed over into adjacent pixels as these really need long glass and by long glass I mean focal lengths measured in meters. I have recently shot some planets at 800mm and with some astro processing magic have some reasonable results but there is no replacement for focal length for shooting planets. Shooting the moon can be done but don't expect great results at 50mm but with a proper exposure you can get some detail, however longer is better and I did this recently with my 800mm setup and my K-3.

3) Question 3: Photo 4 is my first capture of Star Trails (at 30 seconds shutter speed). I need to read up on how to get a longer shutter speed than 30 seconds. Any quick tips on how this is done, throw the tips at me. I recall something about bulb mode, etc...

Use a really heavy ultra sturdy tripod. Once you have that then get an intervolmeter and either have the camera in bulb mode and let the intervolmeter hold the shutter open for as long as you want or have it shoot continuously. If doing the shoot continuously method then combine all the shots using your favorite image combining software (for this I use hugin_stacker) and have the blend mode set to brightest.

While photoptimist says that most astro glass is expensive it doesn't have to be but good astro glass is generally very good glass. One of the best starter lenses for astrophotography of the big deep sky objects is any of the Pentax 200mm F/4 lenses from the S-M-C Takumar forward and those can be found fairly regularly in the US in great shape for $50 to $70. I still use my old S-M-C 200/4 Tak but you don't have to take my word for it as others have gotten great results with other lenses using that optical formula. The lenses I use most for astro are:
Laowa 12mm f/2.8 Zero-D
SMC A 50/1.2
S-M-C 50/1.4 Tak
Samyang/Rokinon 135/2 UMC
S-M-C 200/4 Tak
Sigma 300/4 APO Tele Macro
SMC A* 400/2.8 ED [IF] (sometime with the 2X-L or 1.4X-L rear converters)
I recently acquired the SMC K 35/2 and SMC K 30.2.8 and only have tested the K 35/2 for astro and initial impressions look like it will be a great performer but I still need to test the K 30/2.8.


One other thing to keep in mind is that astro images are almost always stacked. Depending on what you are shooting and what OS you have for your computer there are very good free software options available. Deep Sky Stacker (DSS) has already been mentioned and I used that for a long time. There is also Sequator which has the option to freeze the ground and freeze the sky so I was able to stack to get this image last year. I also know some people use the software Siril for stacking but I haven't figured that one out yet. So those are the free options I know about but if you are willing to pay for software I like Astro Pixel Processor (APP) and another great pay option is Pixel Insight

[tuco]

Perhaps here is a tip on knowing what's up in the night sky so you don't have to guess what you're looking at so much. Look up your geographical latitude and longitude just for reference. Visit a webpage such as Sky And Telescope to get simple overview of what's up in the twilight sky for that week.

After watching the night sky for a season or so in Virginia, you might notice there is a 'belt' in the sky spanning above and below the Sun's path through the sky that day where you'll only see the planets. Watch long enough, for example, and might notice that Venus only appears either in the morning sky in the direction of sunrise or in evening sky in the direction of sunset. And sometimes not at all when it's too close to the Sun. So if you happen to find yourself looking, say, north and see a bright object in Virginia, you can rule out a planet.

[damianc]

Stellarium is a great piece of software for exploring the night sky from your location and planning imaging sessions

[MaineNative]

I normally do Milky Way astro photos, so I shoot with an ultra-wide Rokinon / Samyang 14 f2.8 on my K-1, K-5 or K-3iii. My Pentax DA 10-17 does okay too, but it is harder to focus.

For settings on my K-5, I use Astrotracer at f3.5, ISO 800-1600 for a 60-120 sec exposure. I get “blooming” of bright stars at f2.8, which is why I stop down to 3.5. If I want to shoot without Astrotracer, I go with ISO 1600 at 10-20 sec, but the image will need extra exposure added in post processing. For the K-3iii, it is safe to push the ISO to at least 3200. Although Astrotracer says it can do 4-5 minute exposures, you need to be really lucky calibrating. I can usually get decent results up to 2-3 minutes, and great results around 30-60 seconds.

For the moon, I use my longest lenses, like my DAL 55-300 or I have a k-mount 400mm spotter scope. I set the ISO at 400-800 with an exposure of 1/250 to 1/500 for the full moon, so no Astrotracer needed. I shot at f/8 to F/11. You want a pretty fast shutter speed because the full moon is very bright. I find a slightly under-exposed image shows more craters and detail.

If you want a picture of the landscape with a full moon, shoot the night *before* the full moon. There will still be some daylight as the moon rises so the landscape and moon exposure will match. The night of the full moon, the sun sets before the moon rises so it is tough to get both the moon and foreground exposures to agree.

[Michael Piziak]

Question: In my photo 1, is the bright star, is it the planet Saturn with its rings or Jupiter with its moons?

Here is a crop:

[photoptimist]

Question: In my photo 1, is the bright star, is it the planet Saturn with its rings or Jupiter with its moons?

Here is a crop:

I'd say Jupiter with moons.

P.S. Jupiter orbits at 5.2 AU from the sun, making it 27 times (about 5 stops) dimmer than Earth's sunny f/16 rule -- Jovy f/2.8? Saturn orbits at 9.5 AU from the sun, making it 90 times (about 6.5 stops) dimmer than Earth's sunny f/16 rule -- Saturnian f/1.7?

[MossyRocks]

Question: In my photo 1, is the bright star, is it the planet Saturn with its rings or Jupiter with its moons?

Here is a crop:

That would be Jupiter with it's moons with too long of an exposure so it shows training in the moons almost making them look like rings. Saturn's rings are large,close and would be continuous. Here is a shot I did at 800mm of Saturn to give an idea of what it looks like:

[Michael Piziak]

I'd say Jupiter with moons.

P.S. Jupiter orbits at 5.2 AU from the sun, making it 27 times (about 5 stops) dimmer than Earth's sunny f/16 rule -- Jovy f/2.8? Saturn orbits at 9.5 AU from the sun, making it 90 times (about 6.5 stops) dimmer than Earth's sunny f/16 rule -- Saturnian f/1.7?

Thank you very much photoptimist!

---------- Post added 10-02-21 at 02:53 PM ----------

That would be Jupiter with it's moons with too long of an exposure so it shows training in the moons almost making them look like rings. Saturn's rings are large,close and would be continuous. Here is a shot I did at 800mm of Saturn to give an idea of what it looks like:

Thank you, also, very much MossyRocks ! & thanx for the explanation and photo example - makes it very clear to me!