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07-22-2018, 07:44 AM   #1
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Astrophotography recomendations?

Ayo!

I recently bought a pair of Adaptall lenses, along with a 2X teleconverter and some extensino tubes for close-up, and i'm kind of waiting for a clear night to test these lenses. I set myself a kind of benchmark with the moon as a reference, so that's my easiest way to see if the lens itself is okay or not, because even my glasses are in bad shape and maybe i can see non-existent defects somewhere on a more complex shot.

I was thinking about this and the astro topic came into my mind. What should i look in a lens if i want to try some astro?
At this moment i have a Tamron 70-210 Adaptall 2, a 28mm f/2.5 Adaptall 2, a 50mm f/2 SMC Pentax-A, and a 50-200 f/4.5-5.6 (if i remember correctly) SMC Pentax DA-L, along with a MARUMI 2X auto teleconverter.

I don't know if i can use them for good looking astro with a K-m (which i'm not very happy with its ISO performance, but taking in mind its 3200 ISO max, i don't really want to complain) so if someone more experienced than me can guide a little, I would appreciate it.

In a future i'm considering to get myself a K5, so it will be better with that one, but until that major inversion, i feel okay buying decent lenses

07-22-2018, 08:20 AM   #2
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3200 iso is about the most you'll want to use anyway but the K-5 is a great astro camera and the K-5IIs is even better if you can find one within your budget. I think you'll find that the 2x teleconverter with do more harm than good in terms of image quality and extension tubes do nothing for astro as you are working at infinity focus rather than close up. I would suggest that you join up with the Astrophotography group here on Pentax Forums. The folks there are knowledgable and helpful.
07-22-2018, 08:31 AM   #3
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QuoteOriginally posted by dakight Quote
3200 iso is about the most you'll want to use anyway but the K-5 is a great astro camera and the K-5IIs is even better if you can find one within your budget. I think you'll find that the 2x teleconverter with do more harm than good in terms of image quality and extension tubes do nothing for astro as you are working at infinity focus rather than close up. I would suggest that you join up with the Astrophotography group here on Pentax Forums. The folks there are knowledgable and helpful.
Yup, but as far as i can see, ISO 3200 in this camera is like 51200 on a K1, this one just keeps collecting noise at that ranges. The upper acceptable limit is 400 ISO and maybe 800 if i don't need pretty images, which is almost never because for that i use my phone. 1600 and 3200 is just useless.

How do i join a group?
07-22-2018, 04:44 PM   #4
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QuoteOriginally posted by CapitanXeon Quote
How do i join a group?
go to All Pentax User Groups - PentaxForums.com, in the field "Search Groups" type "Astrophotography", click on it and it will say "Join Group" in small caracters just above the group picture.

The K-5 has the astrotracer function if you have an O-GPS1 unit (250$ new), really great for astrophotography. I've tried many lenses for astrophoto, the best affordable lenses are the Samyang/Rokinon (16/2, 35/1.4, 85/1.4 and 135/2), but I've had lots of fun with M28/2.8 and the A50/1.4 is still one of my favorite for astronomy. I've had Tamron Adaptall-2 24/2.5 but corner sharpness just wasn't there.

Hope this helps!

07-23-2018, 06:18 AM   #5
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QuoteOriginally posted by SunValley Quote
go to All Pentax User Groups - PentaxForums.com, in the field "Search Groups" type "Astrophotography", click on it and it will say "Join Group" in small caracters just above the group picture.

The K-5 has the astrotracer function if you have an O-GPS1 unit (250$ new), really great for astrophotography. I've tried many lenses for astrophoto, the best affordable lenses are the Samyang/Rokinon (16/2, 35/1.4, 85/1.4 and 135/2), but I've had lots of fun with M28/2.8 and the A50/1.4 is still one of my favorite for astronomy. I've had Tamron Adaptall-2 24/2.5 but corner sharpness just wasn't there.

Hope this helps!
I tried yesterday the 50mm and while it turned out somewhat well, the noise coming from the camera (even at ISO 100) and some contaminating lights nearby, spoiled it completely.

I just joined the group, let's learn
07-23-2018, 07:14 AM - 2 Likes   #6
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If you really get into astrophotography, you'll find that wide-angle and narrow-angle astrophotography are different challenges, the former being much less demanding. The longer the focal length of the lens you use, the better your tracking needs to be, and to gather adequate light, low f stop (larger focal length) lenses cost more (teleconverters work against you because they multiply the focal length and the f-stop of the lens you're using - maybe ok for bright objects but not general astrophotography).

For narrow-field astrophotography, you might want to invest in a tracking mount that moves the camera and lens to stay "on target" (it will even help with wide-field time exposures). Astrotracer limits exposure time, whereas, with a tracking mount, long exposures can be had. You also eliminate the edge-of-field tracking errors with wide-field lenses. Just something to consider if you get serious and as you gain experience and want to push your ambitions further. In the meantime, good luck with your astro shooting - there's a lot up there to take in
07-23-2018, 10:48 AM   #7
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QuoteOriginally posted by Bob 256 Quote
If you really get into astrophotography, you'll find that wide-angle and narrow-angle astrophotography are different challenges, the former being much less demanding. The longer the focal length of the lens you use, the better your tracking needs to be, and to gather adequate light, low f stop (larger focal length) lenses cost more (teleconverters work against you because they multiply the focal length and the f-stop of the lens you're using - maybe ok for bright objects but not general astrophotography).

For narrow-field astrophotography, you might want to invest in a tracking mount that moves the camera and lens to stay "on target" (it will even help with wide-field time exposures). Astrotracer limits exposure time, whereas, with a tracking mount, long exposures can be had. You also eliminate the edge-of-field tracking errors with wide-field lenses. Just something to consider if you get serious and as you gain experience and want to push your ambitions further. In the meantime, good luck with your astro shooting - there's a lot up there to take in
I definetely thought about the astrotracer yesterday, since thanks about looking into what it is, i realizaed that my 30 sec exposures were blurry not because entirely my fault, instead because...the earth is moving.
07-23-2018, 05:20 PM   #8
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QuoteOriginally posted by CapitanXeon Quote
I definetely thought about the astrotracer yesterday, since thanks about looking into what it is, i realizaed that my 30 sec exposures were blurry not because entirely my fault, instead because...the earth is moving.
That's true. You have to be running pretty fast while you're taking that 30 second exposure to compensate (unless you're at the North or South pole)!!

07-23-2018, 11:28 PM   #9
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If you look at the articles&tutorials section under the main site there are tons of guides to astrophotography with Pentax gear. Here is a link to a gear guide. Astrophotography Part 2 of 6: Equipment Selection - Articles and Tips | PentaxForums.com

In short, the guide recommends fast primes and avoiding zoom lenses. You want the largest apertures possible for the best light collection, then you don't have to rely on raising your ISO as much.
07-24-2018, 01:26 PM   #10
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QuoteOriginally posted by catwalk Quote
If you look at the articles&tutorials section under the main site there are tons of guides to astrophotography with Pentax gear. Here is a link to a gear guide. Astrophotography Part 2 of 6: Equipment Selection - Articles and Tips | PentaxForums.com

In short, the guide recommends fast primes and avoiding zoom lenses. You want the largest apertures possible for the best light collection, then you don't have to rely on raising your ISO as much.
But inside of that fast primes (I have two not-that-fast primes) you need to stop them down a bit to have better sharpness right? I'll look into the guide anyways
07-24-2018, 06:00 PM   #11
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QuoteOriginally posted by CapitanXeon Quote
But inside of that fast primes (I have two not-that-fast primes) you need to stop them down a bit to have better sharpness right? I'll look into the guide anyways
With the astrotracer, integration time is limited compared to an equatorial mount, so I tend to use my Samyang 16/2 and 135/2 wide open. They exhibit little coma at f/2.0 so stopping down at f/2.8 would be a waste of photons for just a small gain in corner sharpness. My A50/1.4 is unusable at f/1.4 I have to stop down to f/2.2 or f/2.5 where it becomes tack sharp corner to corner. If you're going after a faint nebula (horsehead, elephant trunk, barnard's loop etc.) f/2.0 or wider is really helpful (that and a dark sky). Stars, general Milky Way, Orion, Andromeda are ok with f/2.8-f3.5.
08-01-2018, 01:37 PM   #12
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Hi, I'm just trying to get experience shooting the milky way and I just bougth Samyang 10mm f/2.8. I noticed that stars become having trails after 3 minutes using the O-GPS1 , not in the center but in the corners. I have read this post so I guess that the limit of astrotracer, compared to the equatorial mount, is just that.
In other world, and saying it in a question way, do you think the attached image will be with no trails using an equatorial mount?
This picture has been taken with K3, O-GPS1, Samyang,10mm f2.8, 100ISO f/8 190seconds, tripod of course
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08-01-2018, 03:26 PM   #13
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QuoteOriginally posted by mctaveck Quote
do you think the attached image will be with no trails using an equatorial mount?
Yes, I would think so. That's a problem with ultra wide angles and the astrotracer. Since the camera is not moving the stars change position relative to the camera line of sight and distortion will make the stars from the corner move at a different speed than those in the center.
08-25-2018, 06:37 AM   #14
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I had similar problem with 100 mm, but I'm beginner in this field.
08-25-2018, 10:59 AM - 3 Likes   #15
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Finally i got a clear, dark sky, and went to try. It turned out very well. I did one with trails and another without them, and i like both. I actually did more shots and so, but you know.





Just for being my first shots i'm very happy ♥
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