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04-23-2015, 10:14 AM   #796
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QuoteOriginally posted by JimmyDranox Quote
Nice.
QuoteOriginally posted by fs999 Quote
Superb !
QuoteOriginally posted by Ex Finn. Quote
Nice result.
thank you very much!

04-24-2015, 08:45 AM   #797
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QuoteOriginally posted by stanzhou Quote
if you calibrate polar alignment really perfect under windless night, it's capable of 300s of tracking at 200mm but normally I just expose 180s maximum for single frame.
polar alignment is kind of pain, I am not sure which version are you having.
I am having a astro version with L shape plate, polar light cannot fit into L-plate so I have to use my cellphone light to calibrate polar alignment.


Thank you for the Information. I was in my backyard yesterday to do a test. I will show the results - if it is worth it .


What I definitvely can say is that in comparison with the O-GPS it is so much more inconvenient work doing the polar alignement. I also use the L-plane and it really sucks that there is no light to support my weak eyes .


But once the setup is made and the machine is running in contiuous frame shooting mode it is a massive and comfortable benefit not having to stand aside and manually start each frame. O-GPS1 moves the sensor, not the camera, so it keeps you on the go frequently having to readjust the frame to keep the rotating stars within the picture.


In contrast once the Star Adventurer setup is propperly running with Long exposure triggered by triggertrap I can leave the scene, drink a glass or do else for a long time. So I did about 30 x 120 seconds yesterday without standing nearby.

I will work on the results this evening.......
04-24-2015, 02:38 PM - 1 Like   #798
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There it is: First Light on M51 for Pentax K5 and Starwatcher Star Adventurer!


20 x 118 seconds, 200mm/F4,5, ISO 800. 3 darks, 10 flats.


Stacking with DeepSkystacker with 3 x drizzle, then a bit of Lightroom 6.


I am convinced, have to practice for better polar alignment!


......and need a better method to get a sharp focus - vibrating 10x live screen magnification zoom is not enough for stars at 200 mm with later crop. I will try to grave a Bahtinov mask this weekend.



04-24-2015, 02:53 PM   #799
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Very impressive photograph for a 200 mm lens of M51. I don't understand by what you mean by this language: "20 x 118 seconds, ... 3 darks, 10 flats" in your description.



04-24-2015, 05:46 PM   #800
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QuoteOriginally posted by XLXW Quote
Very impressive photograph for a 200 mm lens of M51. I don't understand by what you mean by this language: "20 x 118 seconds, ... 3 darks, 10 flats" in your description.

20 "118 second" exposures, 3 "dark frame" exposures and 10 "flat frame" exposures.
The dark`s help subtracting sensor noise, flats have to do with vignetting of the telescope if I recall correctly.
04-24-2015, 05:49 PM   #801
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QuoteOriginally posted by Ex Finn. Quote
20 "118 second" exposures, 3 "dark frame" exposures and 10 "flat frame" exposures.
The dark`s help subtracting sensor noise, flats have to do with vignetting of the telescope if I recall correctly.
Thanks. I appreciate the help. I'm still on the learning curve about this stuff. The next time I'm out in the desert I'm going to try to attempt it through my C8.
04-24-2015, 05:50 PM   #802
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QuoteOriginally posted by Pete_XL Quote
There it is: First Light on M51 for Pentax K5 and Starwatcher Star Adventurer!


20 x 118 seconds, 200mm/F4,5, ISO 800. 3 darks, 10 flats.


Stacking with DeepSkystacker with 3 x drizzle, then a bit of Lightroom 6.


I am convinced, have to practice for better polar alignment!


......and need a better method to get a sharp focus - vibrating 10x live screen magnification zoom is not enough for stars at 200 mm with later crop. I will try to grave a Bahtinov mask this weekend.


Very nice result, thank you for sharing.
04-24-2015, 06:17 PM - 1 Like   #803
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here's an alternate take of something I posted last year:

Bird Rock & Milky Way

K5 & FA31 & O-GPS1, 7-frame pano.


Last edited by mikeSF; 04-25-2015 at 07:59 AM.
04-25-2015, 02:08 AM - 1 Like   #804
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QuoteOriginally posted by XLXW Quote
Very impressive photograph for a 200 mm lens of M51. I don't understand by what you mean by this language: "20 x 118 seconds, ... 3 darks, 10 flats" in your description.

Translation

- series of 20 pictures with exposure of 118 seconds each (called "lights").

"darks and flats" are correction frames that help to opitimise the results of the stacking process.

- 3 "darks" = 3 pictures with same parameters as the normal exposures (iso, aperture, exposure time etc.) at same temperature but with lens-cap on lens. Darks contain the sensor noise. They are later used to subtract noise from the "lights" when the pictures are stacked. If you use the built-in noise reduction for long exposure you do not need darks but each picture needs double time then. Better use darks that are conveniently shot at the end of the session while cleaning up the location.

- 10 "flats" = 10 pictures with same camera/lens combination that contain vignetting, stains, dust etc. of the optical system. I make my flats in cloudy daylight with white t-shirt over lens against the grey sky, focus set to infinity. Like the darks the flats are used during the stacking process. Aim is to neutralise vignetting and other imperfections that come from the lens and sensor.

A 4th type of correction frames, the bias frames records the noise that the sensor produces while reading outvthe data. I do not use bias frames bedaus in my opinion the bias must also be a part ofvthe noise in the darks.

By stacking lights, darks and flats the erratic noise ist reduced while the static signal (e.g. stars) is opitmised.

Try it, its quite easy, software is for free (e.g. DeepSkySacker) and results are dramatically improved, also in wide field astrophotography. There are same good tutorials on youtube.

---------- Post added 04-25-15 at 11:10 ----------

QuoteOriginally posted by mikeSF Quote
here's an alternate take of something I posted last year:

Bird Rock & Milky Way

K5 & FA31 & O-GPS1, 7-frame pano.
Phantastic!!!
04-25-2015, 11:26 AM   #805
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Thanks, Pete. It helps a lot. Here's a photo of the "lens" I intend to use for the astrophotography.

---------- Post added 04-25-15 at 11:28 AM ----------

QuoteOriginally posted by mikeSF Quote
here's an alternate take of something I posted last year:

Bird Rock & Milky Way

K5 & FA31 & O-GPS1, 7-frame pano.
Very nice image, Mike. Where was it taken?
Attached Images
 
04-25-2015, 12:25 PM   #806
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QuoteOriginally posted by XLXW Quote
...
Very nice image, Mike. Where was it taken?
thanks, this is natural bridges state beach in santa cruz, CA. the lights on the horizon are from Monterey, CA. Thanks to GPS, the exact location is embedded in the EXIF, viewable on the map if you click the pic to the flickr link.

QuoteOriginally posted by Pete_XL Quote
Translation

...

Phantastic!!!
thanks!
04-25-2015, 01:40 PM   #807
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I knew that I had seen that rock somewhere. Nice capture of the Milky Way. It's a really spectacular photograph. You should submit to "Astronomy" magazine and to "Sky and Telescope" magazine.
04-25-2015, 10:16 PM   #808
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I have the same shed.....too bad I do not have the same scope!!!
04-25-2015, 10:57 PM   #809
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The scope was built by Celestron in 1979-1980 for film astrophotography for a guy who worked for Eastman Kodak. His co-worker, a retiree from Eastman Kodak, who used to sell me Pentax camera stuff at the Torrance swapmeet got the telescope for me years ago from his astrophotographer friend who was likewise retired from Eastman Kodak. Celestron has twice offered to buy that telescope back from me when I have taken it in for cleaning. It is a marvelous instrument unlike any which are commercially built and sold today. I've actually seen the central star in M57 (The Ring Nebula in Lyra) on several occasions with that telescope and a Pentax 5 mm XW eyepiece. I didn't even know that it was difficult to see that particular star until I read in astronomy magazines about just how difficult it actually is to see that star. I've tried film astrophotography several times with it without much success -- usually black film when trying eyepiece projection photography with the camera mounted on an eyepiece. I'm going to try it with my Pentax digital camera the next time I get out to the desert to play with it. It's the main reasons why I've been asking for some "pointers" here on this astrophotography thread. I'm not much of a photographer and the learning curve is still pretty steep for me but I'll get there.
04-26-2015, 08:55 AM   #810
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nice! beyond me for sure....envy yer challenge, frustration and eventual satisfaction, good luck and happy shooting!
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