M82 with just a tri...
 
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M82 with just a tripod and a static dslr  

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 ah
(@ah_astro)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 3
April 14, 2021 20:04  

I don't know of other people use Pentax's astrotracker function (haven't seen anyone), but it's quite fun.
I made this image of M82 with a static mounted Pentax dslr on a tripod (nothing else). The camera calculates sensor translation and rotation based on build in gps and compass. I use an 'old' manual achromat lens (SMC-A 200/4) fitted with a baader contrast booster.

Seeing was 'so so'. Ursa Minor's dimmest star Eta Umi was just barely visible. Milky way was invisible (bortle scale6/7).

APP processed this stack of 47 lights, ISO 3200, f5.6, with 25 bias', 25 flats, 25 darks. Postprocessing done in affinity photo.

 

m82 RGB session 1 lpc cbg

 

m82 RGB session 1 lpc cbg detail

 


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3291
April 17, 2021 20:48  

Very interesting, didn't know about that indeed. What is the exposure limit etc, I guess still about 15 seconds per image?


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 ah
(@ah_astro)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 3
April 17, 2021 22:55  

For this example lights were taken with an exposure time of 20 seconds per image. Depending on quality of calibration (gps/compass), focal length and location of the subject, theoretical exposure times can go up to one and a half minute (200mm lens, limited by translation and rotation of the sensor). Practically, I never managed above 50" without ending up with unwanted trails. I am generally happy when I manage 20 or 30" exposure times. Other focal lengths will result in other exposure times.


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(@vincent-mod)
Universe Admin
Joined: 4 years ago
Posts: 3291
April 18, 2021 00:12  

That's certainly impressive for a non tracked setup, thanks, nice to know.


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