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11-07-2010, 03:20 PM   #61
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QuoteOriginally posted by RipDaJacker Quote
The mount is motor driven on ra and dec axis, if you do a good polar aligment you can get a nice tracking time up to 3, 4 minutes without stelar drift. Once turned on, the ra axis motor starts compensating for the earth rotation. Guided means that u also mount a special camera or modded web camera on the telescope hooked to a pc and using software like iris or starry night i belive, will adjust mount errors keeping in track stars that you select. That way you can have bigger exposure times like 10 minutes or more on a fainth object like a galaxy or nebula.
Ok, I first thought it wasn't motorized at all. But anyhow, well done. It's a great picture.

11-07-2010, 08:07 PM   #62
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QuoteOriginally posted by RipDaJacker Quote
Im new into astrophoto,
RipDaJacker,

Stunning photo for anyone, let alone a beginner. You captured the faint wispy wings as well as the Trapezium stars. I would have said it could not be done with such short exposures.
11-08-2010, 04:48 AM   #63
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thanks everyone

QuoteOriginally posted by Ex Finn. Quote
That is a Stellar image. What scope did you use?.
I used a Skywatcher 200/1000

@LeoTaylor I know i was amazed myself by the good quality of the sky that night, the seeing was near perfect I cant wait to get back there this weekend if the weather allows me, im aiming for something a little harder, the horsehead nebula. I have done some tests that night and i managed to expose rosette near horsead very easy.
11-09-2010, 02:12 PM   #64
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QuoteOriginally posted by RipDaJacker Quote
Im new into astrophoto, 2 months sice i got my telescope... Now i have a big itch to replace my ol' trusty k10 with a k5, i cant imagine the stacked shots wiath a clean 3200, 6400 iso This is my best result yet, shot 2 days ago on a very clear type 2 sky. m42 Orion nebula, 200/1000mm telescope, EQ5 unguided mount. Iso bracketing and 60 frames stacked in deep sky stacker, 21 minues total exposure time.

Wow, fascinating shot

11-09-2010, 04:09 PM   #65
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K10D and Pentax DSLRs for astrophotography

The k10D is a great camera for astrophotography, and here's a few sample images:

Picasa Web Albums - Duncan Munro - astrophotos

My main camera is a D50 which has had the IR blocking filter removed, and I intend to have this done to my K10D as well, at some point in the future.



I have tested most Pentax DSLRs for astrophoto suitability and the K10D seemed best. The K100/110 had too much dark current. The K200D seemed to have more amp glow than the K10D. The K20D, K-X and K-7 will not allow the user to turn off dark frame subtraction (DFS) for exposures longer than 30sec. However the K-R and K-5 will allow the user to turn off DFS and appear to have very low dark current and little or no amp glow as well. The K-R might be the most cost effective DSLR for astro work.

A common misconception is that high ISOs are required for astroimaging and this is incorrect. Low noise 12bit CCD cameras like the K10D will generally perform better with lower ISOs and longer exposures. 14bit cameras like the K-5 will record more information at low ISO and longer exposure than at high ISO. The ISO setting does not change the camera's sensitivity but merely adjusts the amp gain by reading out the pixel electron well before it is full. A 14bit camera gains nothing by using high ISO and actually records less information than when used at low ISO because of the reduction in DR.

This is a K10D image of the Orion Nebula, 37mins at ISO100 @ 1700mm EFL with no dark frame subtraction:

11-09-2010, 05:09 PM   #66
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That is very nice Duncan.
11-09-2010, 05:23 PM   #67
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QuoteOriginally posted by duncan1 Quote
I have tested most Pentax DSLRs for astrophoto suitability and the K10D seemed best. The K100/110 had too much dark current. The K200D seemed to have more amp glow than the K10D. The K20D, K-X and K-7 will not allow the user to turn off dark frame subtraction (DFS) for exposures longer than 30sec. However the K-R and K-5 will allow the user to turn off DFS and appear to have very low dark current and little or no amp glow as well. The K-R might be the most cost effective DSLR for astro work.
Excellent work Duncan. Do you have any suggestions for a tracking mount?
11-09-2010, 05:29 PM   #68
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Those are some pretty great pictures Duncan. Do you know if it's possible to take good pictures of space without a telescope? Would it be worth it to buy an equitorial mount and try to take pictures with my K-x and a 55-300mm lens?

11-09-2010, 09:02 PM   #69
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A 300mm F4 lens+ DSLR and an inexpensive german equatorial mount (as shown earlier in the thread) makes a really great astrophoto setup. I try to avoid zooms because they tend to have more internal reflections and poorer edge correction compared to a fixed lens but that doesn't mean that yours won't work. One thing that hasn't been mentioned is the use of an autoguider which allows the mount to track accurately for very long (hours) periods of time and is essential to successfully utilize long exposures.
11-10-2010, 04:32 PM   #70
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High ISO or Low ISO?

QuoteOriginally posted by duncan1 Quote
The k10D is a great camera for astrophotography, and here's a few sample images:

.
.
.

A common misconception is that high ISOs are required for astroimaging and this is incorrect. Low noise 12bit CCD cameras like the K10D will generally perform better with lower ISOs and longer exposures. ......'

This is a K10D image of the Orion Nebula, 37mins at ISO100 @ 1700mm EFL with no dark frame subtraction:
Very fine overvew + picture, duncan1.

And no doubt that you are right in all aspects of your statements.

Just one comment, though, regarding ISO settings: UNLESS you have a very accurate equatorial tracker (and have aligned that accurately too) or the time and patience to do some serious guiding, you may have to - and can - get away with using higher ISO and shorter exposure times - thanks to the quality of contemporary APS-C and FF sensor technology. Results may not be the very best, but I am actually quite happy with the detail I can get using ISO 1600 under a very light polluted city sky.

Thus, I think that for beginners and not-so-diligent-astrophotographers like myself, it would still be good advice to start out trying the combination of high ISO and short exposure times. Proper alignment and/or guiding can be a pest for beginners that do not have the proper, advanced gear.



200 mm Tamron Model 04B: 8 s exposure at f/4 and ISO 1600 taken with Pentax K200D. Postprocessing in PhotoImpact.

Others have caught the reflexion nebulae in the Pleiades much, much better - but I got my own ! (Even on a rather hazy night with thin, annoying clouds here and there)


B.R. / Stone G.
11-14-2010, 03:43 AM   #71
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I am just getting started in Astrophotography and haven’t yet taken any pictures worth showing off. However I have just finished reading a book which I would recommend to anyone interested in astrophotography with a DSLR - "Digital SLR Astrophotography" by Michael Covington (I have no affiliation etc...). For details of the book and lots of useful links see here: Digital SLR Astrophotography .
In the book Covington shows that superb astro photos can be obtained with wide angle primes and no tracking at all – I have tried it and with a 28mm lens and 15sec exposures the stars barely streak at all. I don’t have a telescope worth putting my camera on but I intend to build a barn door tracker or similar for use with longer primes – my converted 36” reconnaissance lens (https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/64271-impossib...tml#post893159 ) should be a reasonable telescope substitute
A recommendation for those who suffer from light pollution: didymium glass filters (Hoya red intensifier) will block out the sodium D lines from street lights but will pass all of the main emission lines from nebulae etc. There are dedicated nebula filters which will block other light pollution as well but I suspect they will be a lot more expensive.
11-14-2010, 11:55 PM   #72
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Astrophotography is an immensely deep topic and it is probably a good idea to purchase a book on the subject, and/or spending a lot of time reading various websites devoted to the subject, before you make any purchases. This is a good website to get started on:

Andy's Shot Glass - Affordable Astronomy, astrophotography,ccd, Telescopes

start here:
http://www.andysshotglass.com/Astrophoto101.html
and here:
http://www.andysshotglass.com/ChoosingScope.html

cheers

Duncan

Last edited by duncan1; 11-15-2010 at 12:10 AM.
11-18-2010, 04:44 PM   #73
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do you think a k5 with a DA*300/4 and a pentax 1.7 adapter (+ an ok tracking pod) would be good for astropfotography?
11-18-2010, 05:15 PM   #74
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QuoteOriginally posted by dankoBanana Quote
do you think a k5 with a DA*300/4 and a pentax 1.7 adapter (+ an ok tracking pod) would be good for astropfotography?
I can't see why it would be bad. The primary lens is around 77mm, which in telescope terms is pretty decent for a refractor.

Here is an example of the DA* 300mm with a 1.5x kenko teleconverter:

The Moon | Flickr - Photo Sharing!
11-19-2010, 06:05 AM   #75
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K5 + DA*300 mm f/4 for astrophotography

QuoteOriginally posted by dankoBanana Quote
do you think a k5 with a DA*300/4 and a pentax 1.7 adapter (+ an ok tracking pod) would be good for astropfotography?
That sounds like a dream-combination to me! A quality prime lens will essentially always be better than a quality zoom when we talk about astrophotograhy - in particular, when you consider adding a telecoverter.

Just remember that while stars are point sources of light and record equally fast on your sensor with or without TC, you will need longer exposure times (by almost a factor of 3) for extended objects such as nebulae and galaxies to capture the same "amount" of light when you go from an f/4 to an f/7 system. So, do try also to use your lens w/o TC for such work.

For lunar work, a 500 mm focal length is a bit short to show much fine detail and for planetary work - forget it.

B.R. / Stone G.
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