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10-14-2011, 08:35 PM   #1
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Good Cheap Lens for Astrophotography

I'm looking for a lens in the 85-200mm range to use for astrophotography. I want it to be fast and sharp enough wide open with little coma or CA. I don't have any kind of tracking mount (yet) so I'm limited to 3-6 second exposure times, high iso and using deep sky stacker. I've tried my Sears 135mm f2.8 and I like it's speed but on brighter stars it adds streaks and coma. And I don't want to pay more than $100. Does such a lens exist? Also, example pictures would be nice. Here's what I got with my Sears 135mm f2.8: https://www.pentaxforums.com/forums/1670011-post104.html

Kevin

10-14-2011, 09:21 PM   #2
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Depending on the kind of objects you want to photograph it can be slow, but the FA 100-300mm f/4.5-5.6 covers a good range, has good sharpness wide open and along the zoom range, and most importantly: is very inexpensive. I have used it for hiking and moon shots, I'm not sure how well it would fare with faint objects, but maybe for tracking nebulae it would work.


IMGP2099 por hcarvalhoalves, no Flickr
10-15-2011, 08:08 AM   #3
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The Same Search

Hello Kevin,
Good luck with your search. I'm actually on the same path as you. I have the same exact sears lens and made some awesome shots with it already. I bought a Quantaray 70-300 1:4-5.6 for I think $100 off craigslist a while and just now started to realize what an awesome lens it is. I recently purchased the AstroTrac TT320X and it is AWESOME! I'm my very first night I made the photo attached. Its a single expose of 180 with no post-processing. After it was processed it looked even better, (however that photo is on my other computer). Tracking will make everything so much better. You can even start with a barn-door style tracker for dirt cheap and achieve some good photos. Good luck and keep in touch. I just joined this forum a couple weeks ago so I'm new here. Now I'm just waiting for the skies to clear to get back out there.
As far as cheap lenses go, try to find lenses that are "broken". I got a good lens for astrophotography for $25 because the aperture blades were stuck wide open, just where I want them. I do look every day though and sometimes ya just get lucky. Maybe you could share some tips and pointers? I'm currently stationed in Japan and I'm pretty sure I'm the only Marine that is into Astrophotography here. HA!

-Josh
Semper Fi!
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10-15-2011, 11:50 AM - 1 Like   #4
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Nice shot.

10-15-2011, 04:01 PM - 1 Like   #5
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Very nice shot.
10-15-2011, 06:25 PM   #6
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Thank you!

Thank you all so much. Here is the shot after I learned what a "flat" is and how they work. I did this in just a couple steps in Photoshop. I'm still learning the Deep Sky Stacker program so hopefully I'll get some stacked pictures up here soon. Also is a picture of the Andromeda Galaxy. That was a 123 second single exposure shot with a Sears 135mm f2.8 wide open. Of course after this shooting experience I learned that if you go a stop down or two you get sharper images. Just waiting for more clear skies.
I'm always open to constructive criticism so if you know some secrets, please share! Thanks again for the compliments. That really makes this hobby worth it. I LOVE seeing people's expressions when the see these photos. To be able to capture something that is 2.5 MILLION light years away. Incredible!

-Josh
Semper Fi!
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10-15-2011, 07:50 PM   #7
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QuoteOriginally posted by hcarvalhoalves Quote
Depending on the kind of objects you want to photograph it can be slow, but the FA 100-300mm f/4.5-5.6 covers a good range, has good sharpness wide open and along the zoom range, and most importantly: is very inexpensive. I have used it for hiking and moon shots, I'm not sure how well it would fare with faint objects, but maybe for tracking nebulae it would work.


IMGP2099 por hcarvalhoalves, no Flickr
I'm happy with the shots I've gotten of the moon with my Pentax 55-300mm lens. But then I got kind of bored of taking pictures of the moon, so now I'm trying to photograph nebulae.
10-15-2011, 07:55 PM   #8
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QuoteOriginally posted by GWARmachine Quote
Thank you all so much. Here is the shot after I learned what a "flat" is and how they work. I did this in just a couple steps in Photoshop. I'm still learning the Deep Sky Stacker program so hopefully I'll get some stacked pictures up here soon. Also is a picture of the Andromeda Galaxy. That was a 123 second single exposure shot with a Sears 135mm f2.8 wide open. Of course after this shooting experience I learned that if you go a stop down or two you get sharper images. Just waiting for more clear skies.
I'm always open to constructive criticism so if you know some secrets, please share! Thanks again for the compliments. That really makes this hobby worth it. I LOVE seeing people's expressions when the see these photos. To be able to capture something that is 2.5 MILLION light years away. Incredible!

-Josh
Semper Fi!
Wow that Astrotrac thing looks pretty good. Your pictures look a lot better than mine. What camera and what iso did you use? I found even if I use really high iso speeds I can make the sky darker and less noisy by moving the 'blacks' slider far to the right in photoshop. I never could figure out what a flat is.

10-16-2011, 02:27 AM   #9
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The K-5

Hello krp, and thank you. I use a K-5. I started out with the K-x and made some other awesome astrophotographs with it as well (and still do, I couldn't let it go. I usually try not to go above ISO 800. After I found out about "flats, darks, bias flats" and so on, I think I may try 1600 from time to time. I like 400 to 800 just cos of the less noise. I attached a link that I found just the other day. I followed the steps and thats how I made the Orion picture posted here darker. Also, if you're a windows user, a lot of people use Deep Sky Stacker which I am still learning about. It's free to download. As soon as I figure it out I'll definitely be adding those pictures as well.
I LOVE my AstroTrac. I had to save up a ton to get it but it was totally worth it. I would say I had to save up for the K-5 too but I thank Best Buy for their 18 month no interest financing offer. HA! I just couldn't wait any longer. Now I'm on the search for better quality lenses.
I'd just like to say thank you again to everyone for the communication and comments here. I'm stationed in Japan and there just aren't many Marines here that I can communicate with about this stuff. And of course the whole language barrier with the local nationals makes it even tougher. So thank you all.
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