Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
09-08-2011, 12:08 PM   #1
Pentaxian




Join Date: Jan 2011
Location: New York
Posts: 3,012
Seeking astrophotography lens recommendations

I'm delving deeper into astrophotography and wondering which telephoto (135mm and longer) lenses to look for. I'd be piggybacking on an equatorial mount for stacked/long exposures of deep sky objects. I expect to buy used because new telephotos suitable for astrophotos tend to be pricy; I can buy telescopes for less money.

(This post arguably belongs in an astrophotography forum rather than PF. Replies there would mostly likely say that only Canon cameras can work.)

I know the basic criteria to look for: prime generally better than zoom; fast aperture; sharp; minimal CA (galaxies and nebulas don't really care, but nearby stars are sensitive to CA); multicoating. Having an an A setting on the aperture ring is irrelevant because I'll only be using Manual. Close focus performance and AF are also irrelevant because I'll always focus to infinity.

135/2.8, 200/2.8, or 300/4 are possibilities. Most lens reviews understandably concentrate on typical terrestrial usage, not photos of the night sky, so I can't learn too much from written reviews.For those of you with astro experience, what lenses in that range do you recommend, and what lenses should I avoid?

09-08-2011, 12:37 PM   #2
Pentaxian
littledrawe's Avatar

Join Date: Jan 2010
Location: Red Rock
Photos: Gallery | Albums
Posts: 2,434
QuoteOriginally posted by DeadJohn Quote
I can buy telescopes for less money.
from what I understand, there are some telescopes you can mount to your camera and perhaps get the results you want. There is a member here called "squier" I believe that knows quite a bit about it and there is a post in the beginners section where it is talked about.
09-08-2011, 12:39 PM   #3
Pentaxian
littledrawe's Avatar

Join Date: Jan 2010
Location: Red Rock
Photos: Gallery | Albums
Posts: 2,434
https://www.pentaxforums.com/forums/pentax-beginners-corner-q/92808-recommend...-wildlife.html

3rd or 4th page starts to get into it.
09-08-2011, 12:59 PM   #4
Veteran Member




Join Date: Jan 2011
Location: Minahasa, North Celebes (Sulawesi)
Photos: Albums
Posts: 585
I'm not really into shooting stars ..but few weeks ago, when the night sky is clear, I was tempted to point my camera up. Being with no specialized gear, I rely only to the camera's maximum 30 sec. exposure and a couple of primes.

I found that going beyond ISO 400 is a disaster, too many 'extra' stars added by the noise. Using my Takumar (Bayonet) 135/2.5 gave closer view, but forced me to go beyond ISO 400, the results aren't that sharp, yet plenty of noise. Using M 50/1.4 helped to clear up the noise, also a bump in sharpness. Tested using 50/2 I got better sharpness, but the noise returned. I got kind of challenged, so I bought M 50/1.7, thinking that the sharpness could have been more with this lens, while still can maintain speed. I also ordered a remote shutter, the one that can do bulb shots, hoping that I can use F numbers where my lens are the most sharp. Thinking also to get one of those 135 Taks, they are known to be sharp..but not on this month's paycheck.

The 50/1.7 arrived today, but the remote is still on the way. Well..It's raining outside anyway.. so much for an amateur stroll into deep space

09-08-2011, 01:16 PM   #5
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,814
I was in a discussion a few years ago about which 135mm was better. Someone pointed out that the SMC Pentax 135/3.5 (the K version) was better than the SMC Pentax-M 135/3.5 for astrophotography. They had links to photos that showed this. The K version is harder to find but you can use the Super-Multi-Coated Takumar instead. It's the same formula. Get one with the original hood, which is very deep.
09-08-2011, 01:56 PM   #6
Pentaxian




Join Date: Jan 2011
Location: New York
Posts: 3,012
Original Poster
QuoteOriginally posted by minahasa Quote
I'm not really into shooting stars ..but few weeks ago, when the night sky is clear, I was tempted to point my camera up. Being with no specialized gear, I rely only to the camera's maximum 30 sec. exposure and a couple of primes.

I found that going beyond ISO 400 is a disaster, too many 'extra' stars added by the noise. Using my Takumar (Bayonet) 135/2.5 gave closer view, but forced me to go beyond ISO 400, the results aren't that sharp, yet plenty of noise. Using M 50/1.4 helped to clear up the noise, also a bump in sharpness. Tested using 50/2 I got better sharpness, but the noise returned. I got kind of challenged, so I bought M 50/1.7, thinking that the sharpness could have been more with this lens, while still can maintain speed. I also ordered a remote shutter, the one that can do bulb shots, hoping that I can use F numbers where my lens are the most sharp. Thinking also to get one of those 135 Taks, they are known to be sharp..but not on this month's paycheck.

The 50/1.7 arrived today, but the remote is still on the way. Well..It's raining outside anyway.. so much for an amateur stroll into deep space
There's some free software that may be able to help you. Search the web for:

Deep Sky Stacker. You can take a stack of frames and process them into a higher-quality version. Stars and galaxies that are too dim to notice in an individual frame become much brighter in the final version.

Startrails. Less powerful than Deep Sky Stacker but easier to use.
09-08-2011, 02:26 PM   #7
Pentaxian




Join Date: Jan 2011
Location: New York
Posts: 3,012
Original Poster
QuoteOriginally posted by littledrawe Quote
from what I understand, there are some telescopes you can mount to your camera and perhaps get the results you want. There is a member here called "squier" I believe that knows quite a bit about it and there is a post in the beginners section where it is talked about.
Yes, DSLRs are pretty easy to mount in place of the eyepiece on most telescopes. My main telescope is 2000mm and too long for photos of many galaxies and nebulas. I plan to add a telescope between 450-600mm but I'm also looking for wider options. Under 300mm there are few telescopes and many lenses.

Here's a picture to give you an idea of what I want to do. Big scope up top, camera+telephoto on bottom. The photo happens to show an "autoguider" underneath but the same concept applies.

(Not my photo. Original found via images.google.com at http://www.cloudynights.com/ubbthreads/attachments/4035811-C6%20with%2050mm%20autoguider.jpg)
09-08-2011, 02:39 PM   #8
Pentaxian
Sagitta's Avatar

Join Date: Feb 2011
Location: Maine
Photos: Gallery
Posts: 2,912
Just as some examples, here are some wide night sky shots I've taken with the kit lens. I want to get into astrophotography myself, but haven't had the time/chance/gumption to go about getting the gear needed (mainly a decent tracking mount to go beyond minimal exposures). I have a 50mm f/1.7, but honestly haven;t had a great deal of luck getting decent shots with it (more me than the lens). The Sears also tends to get ca when shot wide open, which defeats the purpose of the 1.7 a bit since you have to drop it down a couple notches to get rid of it.

Kit 18-55 lens...
30 second exposure...



30 second exposure



1/2 second exposure




One last one at 30 seconds with the kit. You'll notice it blows the sky right out (though I believe we had a moon out that night which didn't help any)



09-08-2011, 03:16 PM   #9
Pentaxian
Bob from Aus's Avatar

Join Date: Jul 2011
Location: Australia
Photos: Gallery
Posts: 1,080
Wow some inspiring photos. I found my sigma 50-500 rather useless even with the moon.
09-08-2011, 06:23 PM   #10
Veteran Member
Raybo's Avatar

Join Date: Dec 2007
Posts: 871
Nice rig John!

Your image brings back memories of my "old" C8.
09-09-2011, 11:53 AM   #11
Site Supporter




Join Date: Oct 2009
Location: North
Photos: Gallery
Posts: 3,772
The Pentax Q seems to be generating some interest coupled with a K-mount adapter and a long lens.

Supposed to be shot with a SMC PENTAX FA 645 400mm f5.6


09-13-2011, 10:35 AM   #12
New Member
kitfoxdrvr's Avatar

Join Date: Feb 2011
Location: North Carolina/New York
Posts: 7
At that length of lens I would look for glass optimized for focus at infinity, ie a telescope. Look at Orion Telescope's line of Apo refractors. Very reasonably priced for what you get.
09-13-2011, 03:33 PM   #13
Site Supporter
Ex Finn.'s Avatar

Join Date: Nov 2007
Location: Southern Maryland.
Photos: Gallery | Albums
Posts: 6,052
+1 on Orion, the EON ED`s are pretty nice for not much money. Just not good for real wide-field.
09-14-2011, 09:45 AM   #14
New Member
kitfoxdrvr's Avatar

Join Date: Feb 2011
Location: North Carolina/New York
Posts: 7
QuoteOriginally posted by Ex Finn. Quote
+1 on Orion, the EON ED`s are pretty nice for not much money. Just not good for real wide-field.
Glad you posted. The OP needs to look at your gallery and see how nice that scope is. I would expect that same kind of result from the shorter scopes as well. Nice....
09-14-2011, 12:28 PM   #15
Veteran Member
Ben_Edict's Avatar

Join Date: Jul 2007
Location: SouthWest "Regio"
Photos: Albums
Posts: 3,303
QuoteOriginally posted by kitfoxdrvr Quote
Glad you posted. The OP needs to look at your gallery and see how nice that scope is. I would expect that same kind of result from the shorter scopes as well. Nice....
The OP was explicitly looking for shorter fl lenses, because he already has a nice C8 and paraphernalia. So a couple of concrete suggestions:

- 20/2.8 A or FA for extreme wide shots, you could also try the old 16/2.8 A fish-eye
- 24/2.0 FA, is nice if stopped a bit down (f/4- f/56)
- ofcourse the 35/2.0 FA, very sharp
- the 50/1.4 is good in most flavours, though I prefer the A and FA versions, step down to f/2.8 and you'll be happy
- something in the vicinity of 80-100mm is nice. The choices are many (85/2.0 M or the later, much more expensive 85/1.4 A or FA versions, but the 100/2.8 M is also considered nice, which I cannot confirm, as it is the only lens mentioned so far, I do not have). In this range, macro lenses are also a good choice, as they provide a flat field (either the Pentaxes or the Tamron 90/2,5 in one of its many incarnations)
- 135/2.5 K is a very sharp lens

CA and fringing only gets obvious beyond the 135mm limit (mostly). SO here more modern lenses with ED glass is surely of advantage. For istance the K 200/2.5 would be an astrophotographers dream and is plenty sharp - but it also shows noticeable CA, unless you stept down to f/4-5.6. If you can find a Voigtländer 180/4 close-focus (A-version), this is a dream (as would be the A or FA 200/4 Macro by Pentax)

So in the 200mm + department I would go for ED lenses like the 200/2.8 A and later or the 300/4 A and later. The long, fast Pentax lenses all perform admireably, but the Pentaxes (300/2.8 A/FA or 400/2.8 etc.) are all quite heavy and big and put considerable stress on your Celestron's mount.

If you can find the 400/5.6 A, this is a great lens, albeit a bit slow, but you can use it fully open with great results. And the peak of astrophotography with Pentax is the SDHF75 (0500/6.7) ED-Apo telescope. It is fairly small and superbely built and offers really great performance. Add a tc or (if you still can find one) a reducer and you're done. By the way: Lumicon makes a fine 2-inch reducer, which can be screwed into standard 2-inch eyepiece filter threads. It exhibits some distortion, but is otherwise optically quite good and would convert the Pentax 75 into something like a 350mm 4.7 Apo-lens.

Ben
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
aperture, focus, k-mount, lens, lenses, pentax lens, sky, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Recommendations for lens end cap for K mount lens? geekette Pentax DSLR Discussion 10 04-29-2011 05:48 AM
Seeking telephoto? lens advice thestampinglady Pentax SLR Lens Discussion 17 03-23-2011 07:39 AM
Seeking council for next lens mba1971 Troubleshooting and Beginner Help 7 05-07-2010 07:41 AM
Seeking wide-angle lens - Zoom or Prime? pentaman Pentax SLR Lens Discussion 20 11-12-2009 12:42 PM
Affordable lens for astrophotography jamesv93 Troubleshooting and Beginner Help 8 11-04-2009 05:31 PM



All times are GMT -7. The time now is 01:36 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top