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  #21  
Old 25-12-2018, 10:40 AM
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Astrofriend (Lars)
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I have written to Ivo who develop APT and ask if it's posiblie to override the need to switch the hardware button on the lens, man/auto focus. When usingis app Canon control I don't need to do that.
Lars
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  #22  
Old 03-06-2019, 04:04 AM
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Hi,
It ended with a Canon 300 mm f/4 lens. With that I don't have to struggle to find a field flattener and the Canon 6D + 300 mm lens weight in at 2.2 kg. Together with this:

http://www.astrofriend.eu/astronomy/...er-tripod.html

I have a real portable equipment. But I'm not sure if my Astro Adventurer could handle this but have read that others have this to work. With a low readout noise and many short exposures the chance increase that it will work.

Then buy tickets down to Rhodes:

http://www.astrofriend.eu/astronomy/...nomy-cafe.html

We have summer in Sweden now but I can do some test with Moon as test object.

I can use this lens to daytime photography too.

Lars
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  #23  
Old 04-06-2019, 01:41 PM
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Well there is only one answer to the thread title: RedCat 51 APO 250mm f/4.9 . I was using the lens that was regarded as the best at the time for either nikon or canon. The Redcat makes it look like a plastic kit lens. Super sharp and flat field. M48 threaded you just buy with whatever adapter you need to your camera body. Couple of samples on my astrobin page.

Last edited by sil; 04-06-2019 at 02:23 PM.
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  #24  
Old 05-06-2019, 08:00 PM
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Hi Steve,
That's a very interesting lens. Have you found some good reviews, where they compare it relative Canon or Nikon full frame lenses?

I couldn't find that kind of test.

/Lars
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  #25  
Old 05-06-2019, 08:12 PM
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I have the Redcat 51 also and agree its a top lens/mini telescope.

More astro oriented than DSLR lenses.

Greg.
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  #26  
Old 06-06-2019, 08:37 AM
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How much is the redcat?
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  #27  
Old 06-06-2019, 10:27 AM
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How much is the redcat?
$A1375 inc GST
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  #28  
Old 06-06-2019, 10:39 AM
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$A1375 inc GST
Thanks Peter
When they come onto the second hand market, budget is tight currently
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  #29  
Old 06-06-2019, 12:28 PM
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Have you found some good reviews, where they compare it relative Canon or Nikon full frame lenses?

Read my post again, I have been using a highly regarded (ie tested) lens for years and the redcat blows it away. I dont need to find reviews for you I own the lens and speaking from experience. I've never seen a lens ever that was so pin sharp corner to corner. At any price. Under any brand. Especially for its size too I dont see anyone approaching this quality anytime in the near future. Its a manual lens so it wont even be something the consumer brands will feel the need to compete against plus of course f4.9 consumers will claim is far too slow, etc plus their kit lens goes to 300mm, etc. Its a quality product, the numbers mean squat compared to the results.
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  #30  
Old 06-06-2019, 12:41 PM
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Not sure if it is the *best* lens available, but in my opinion, the best value for money in this focal length range is the Canon EF 200mm f2.8L II USM. Very light, extremely sharp, works well with a full-frame sensor, sells for a tad over $AUD900.
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  #31  
Old 02-09-2019, 09:54 AM
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First light with Canon 300 mm lens f/4.

At last we got some darkness so I could test my "new" Canon 300 mm f/4 lens. I used my Star Adventurer mount and didn't had very big expectations about the result. But it worked very well, this is nice, it's like a small telescope. Easy to bring with you on travel. No problem to adapt field flatter. Built in focus motor that I can remote control from my smartphone.

See here:
http://www.astrofriend.eu/astronomy/...31-galaxy.html

It was a lot of things that went wrong this night, but I got 44 minutes of exposures. Next time, better polar align and better focus.

At the bright stars there are some blue bleeding, I have seen that on other 300 mm lenses too. Maybe less when I focus it better.

/Lars
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  #32  
Old 02-09-2019, 04:20 PM
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Originally Posted by Astrofriend View Post
First light with Canon 300 mm lens f/4.

At last we got some darkness so I could test my "new" Canon 300 mm f/4 lens. I used my Star Adventurer mount and didn't had very big expectations about the result. But it worked very well, this is nice, it's like a small telescope. Easy to bring with you on travel. No problem to adapt field flatter. Built in focus motor that I can remote control from my smartphone.

See here:
http://www.astrofriend.eu/astronomy/...31-galaxy.html

It was a lot of things that went wrong this night, but I got 44 minutes of exposures. Next time, better polar align and better focus.

At the bright stars there are some blue bleeding, I have seen that on other 300 mm lenses too. Maybe less when I focus it better.

/Lars
Nice shot Lars. You can remove the blue halos using Lightroom or Photoshop Camera RAW filter. Both of these programs have sliders to remove chromatic aberration from the images and those blue halos will go. You have to be precise though on setting which colour you want removed otherwise it can weaken other star colours.

300mm F4 is a good formula. The other possibility is get stop down ring to screw onto your lens to reduce it down to say F5 or F5.6. Then these aberrations tend to disappear, stars will focus to finer points and less fuzzy.

I did this with my Pentax 645 F4 EDIF lens and it made the images better.
You are doing long exposures anyway so losing a stop of light is not that big a deal. F5.6 is still plenty fast.

300mm though is hard to locate objects you want to image though with a tracker. I piggyback my 250mm or 300mm on a scope on a nice mount that has accurate go-tos. I spent a fair bit of time trying to locate even bright objects without go-to and it wasn't a lot of fun!

Greg.

Greg.
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  #33  
Old 02-09-2019, 08:04 PM
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Thanks for the comments Greg !

I tried to stop down to 5.6 with the built in aperture, but gave uggly result with rays around bright stars. Much better with a rebuilt filter with a hole as you say. But for the moment I feel this is good enough and it will be a bit better when I'm more used with the lens.

I have a Red dot finder, Haven't used it much yet, but now there is a need of it. I mount it on the mount and then it's always there when I change lenses. One problem, I have built the tripod very low to have it more stable and more transportable. Then it's difficult to see through the finder. Maybe a 90 degree mirror can be applied.

I added a map with asteroides:
https://www.astroshop.eu/red-dot-pro...sonian/p,47445

Maybe there is one in the photo.

/Lars
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  #34  
Old 03-09-2019, 06:29 AM
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Thanks for the comments Greg !

I tried to stop down to 5.6 with the built in aperture, but gave uggly result with rays around bright stars. Much better with a rebuilt filter with a hole as you say. But for the moment I feel this is good enough and it will be a bit better when I'm more used with the lens.

I have a Red dot finder, Haven't used it much yet, but now there is a need of it. I mount it on the mount and then it's always there when I change lenses. One problem, I have built the tripod very low to have it more stable and more transportable. Then it's difficult to see through the finder. Maybe a 90 degree mirror can be applied.

I added a map with asteroides:
https://www.astroshop.eu/red-dot-pro...sonian/p,47445

Maybe there is one in the photo.

/Lars
Step down rings are cheap on ebay and screw on the end and are say 5mm wide ring. They stop the sun rays effect on bright stars.

Greg
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  #35  
Old 03-09-2019, 07:18 AM
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Hi Greg,
Now I under stand what you mean, I already have a set of 18 rings.

This was the link:
http://www.astrofriend.eu/astronomy/...31-galaxy.html

See the asteroid map.

Lars
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  #36  
Old 10-09-2019, 01:03 PM
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Well there is only one answer to the thread title: RedCat 51 APO 250mm f/4.9 . I was using the lens that was regarded as the best at the time for either nikon or canon. The Redcat makes it look like a plastic kit lens. Super sharp and flat field. M48 threaded you just buy with whatever adapter you need to your camera body. Couple of samples on my astrobin page.
As a footnote the RedCat Ver 1.5 is now out...it has few refinements and now allows precise squaring-on adjustments of the camera.

There is also a limited edition "SpaceCat" (same as V1.5) but with a Gun metal grey finish and a SpaceKitty logo and carry bag..Might even know a dealer who has them in stock for $1500 or so
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  #37  
Old 13-09-2019, 07:46 PM
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Hi,
The Redcat is very fine, but I think the Canon lens works better for me with its builtin focus motor. The aperture is 70 mm on Canon 300mm f/4 and 51 mm of the Redcat. But the quailty is better I understand, maybe something for the future.

The Petzval design, if it's so good, I don't think I see it on camera lenses, why?

/Lars
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  #38  
Old 13-09-2019, 09:41 PM
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..........
The Petzval design, if it's so good, I don't think I see it on camera lenses, why?

/Lars
Simple.

Not everyone is interested in taking photos always with an infinity focus...as telescopes are designed/optimised to do.

Camera lenses need to work well over a much wider focal range.
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  #39  
Old 13-09-2019, 10:14 PM
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Ah ... then I understand, didn't know Petzval had limitations in focus range.

Thanks a lot for the information Peter !

/Lars
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  #40  
Old 14-09-2019, 10:32 AM
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As a footnote the RedCat Ver 1.5 is now out...it has few refinements and now allows precise squaring-on adjustments of the camera.

There is also a limited edition "SpaceCat" (same as V1.5) but with a Gun metal grey finish and a SpaceKitty logo and carry bag..Might even know a dealer who has them in stock for $1500 or so

$1500?????? passss..........
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