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07-18-2013, 11:37 AM - 2 Likes   #631
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Eagle Nebula and region with Pentax K10D

It's been a while since I did a big astrophoto.

I'd wanted to revisit the idea of a large mosaic of some of the summer objects and had the chance to do this earlier in the month. Since I've managed to understand the amp glow situation with my K10D, doing a mosaic is no longer a forbidden project. Previously, the amp glow would make any stitching effort useless as there would be horrible lines. Also, I've learned a lot about doing plate solves in the field so that I can get accurate camera positions night after night.

Shot from home in a suburban location, the transparency varied over the nights, giving some uneven background to the mosaic. I had to reshoot some of the sequences on better nights to give good source material. Also, because I didn't plan how the frames would map on the sphere of the sky, there was a lot of wasted data because of a diagonal canvas.

The mosaic is assembled from 3 overlapping frames each with at least two nights dedicated to them. Total sum is 58 subs at 1200 seconds giving about 19 hours of integration.



Here's an annotated version.

Here is the link to full size on Astrobin (note that full size is 6016 x 2448)


Last edited by smigol; 07-18-2013 at 01:28 PM. Reason: fixed link
07-20-2013, 03:54 PM   #632
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Evening all.
Been having a go at moon shots and came up with this.
I edited it in camera, hence the colour of the moon.

1/320 f8. ISO 200.
K-5 and Sigma 170-500.

07-21-2013, 06:12 AM   #633
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QuoteOriginally posted by smigol Quote
It's been a while since I did a big astrophoto.

I'd wanted to revisit the idea of a large mosaic of some of the summer objects and had the chance to do this earlier in the month. Since I've managed to understand the amp glow situation with my K10D, doing a mosaic is no longer a forbidden project. Previously, the amp glow would make any stitching effort useless as there would be horrible lines. Also, I've learned a lot about doing plate solves in the field so that I can get accurate camera positions night after night.

Shot from home in a suburban location, the transparency varied over the nights, giving some uneven background to the mosaic. I had to reshoot some of the sequences on better nights to give good source material. Also, because I didn't plan how the frames would map on the sphere of the sky, there was a lot of wasted data because of a diagonal canvas.

The mosaic is assembled from 3 overlapping frames each with at least two nights dedicated to them. Total sum is 58 subs at 1200 seconds giving about 19 hours of integration.



Here's an annotated version.

Here is the link to full size on Astrobin (note that full size is 6016 x 2448)
That's amazing, so much detail and a wonderful composition!
07-21-2013, 03:58 PM   #634
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QuoteOriginally posted by smigol Quote
It's been a while since I did a big astrophoto.

Fantastic! Really great work!

08-04-2013, 12:46 PM   #635
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Star testing my smc Pentax DA* 200mm f/2.8 lens.

For me, end July means that I finally once again get an hour or two around midnight, with a sufficiently dark sky to make sense of renewed attempts into astrophotography. This year, I have been particularly imaptient in my wait because I got the DA 200 lens in April whre weather was cloudy most of the time and then came the white nights of northern summer.....

However, I did get a few images before summer and they all showed some annoying assymetry in the star images with the lens at full aperture such as this image of M57 taken in May clearly demonstrates:


Stack of 7 exposures at 15s, f/2.8, ISO800

The appearance of the stars is the same allover the frame and the halos are all pointin in the same direction so, it really cannot be coma. An UV-IR cutoff filter didn't help either so, the only remedy remaining that I could thing of was stopping down the lens. Amd here are then some results on M13 in Hercules taken on 31 July (where the sky was still rather bright, but good enough for testing). All images shown are stacks of 5 exposures of 20s duration at ISO 2000:



f/2.8


f/3.5


f/4.0


f/4.5

Well, well, I guess I have to accept that this lens works best when stopped down to f/4 or even f/4.5.

EDIT: I should add that pictures were taken with a Pentax K-5 and with the Pentax O-GPS1 Astrotracer for tracking.

Last edited by Stone G.; 08-04-2013 at 01:08 PM. Reason: Addendum
08-04-2013, 02:28 PM   #636
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Star testing my smc Pentax-DA* 200mm f/2.8 - Cntd.

During my lens tests, I also experimented a bit wih mixing apertures and iSO settings and here are some first results.

First a fairly easy target. Although situated in the bright eastern sky with a lttle town a mile away, the core of M31 in Andromeda has now become readily visible in my 10X50 finderscope:


7 images stacked. All 20s, f/4, ISO2000

Below M31, totally invisible in my finderscope, I managed to capture M33 in Triangulum just barely glowing more than the bright eastern midnight sky. Thus, it also took some more agressive post-processing to bring this feeble glow forward:


Stack of 10 exposures of 20s, f/2.8, ISO 2000 and 16 exposures of 20s, f/4 and ISO 3200

And finally, two nights later, the Milky Way band became faintly visible overhead:


Stack of 6 exposures of 20s, f/3.5, ISO 1600 and 6 exposures of 20s, f/3.5, ISO 3200.

Again, all images were taken with a K-5 and the Pentax O-GPS1 Astrotracer. Considering that the sky was by no means really dark, I think these results with my DA* 200mm f/2.8 lens are indeed quite encouraging. So, now I am longing for the dark, clear September nights.....
08-05-2013, 04:03 PM   #637
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Stone

Very nice work with these targets. I've seen those blue and red doughnuts before on unfocused stars. Aside from what you are already doing with the UV/IR cutoff filter and stopping down, there's not much more you can do to tighten the stars. I'd suggest a light pollution filter maybe but these are not inexpensive in sizes appropriate for camera lenses.

You might want to try colored gels (Wratten 72 29 comes to mind) for possible Ha work. It would help limit the passed wavelengths to give sharper stars. Might be worth a try when you've exhausted your other projects!

Edit: Wratten 29 is a deep red filter that should pass a fair amount of Ha while limiting the other frequencies to help produce tighter stars. The 72 filter is a Near IR filter which is not useful for astronomy.

Last edited by smigol; 08-12-2013 at 11:06 PM. Reason: changed filter number
08-06-2013, 03:20 PM   #638
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Heading out in 12 hours...wish me luck! Hoping to get some new shots and plenty of other light frames for stacking. Any recommendations? I'm in the northern hemisphere at 34 lat.

08-07-2013, 12:08 AM   #639
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QuoteOriginally posted by smigol Quote
---------Might be worth a try when you've exhausted your other projects!
Thank you smigol for encouraging comments and suggestions. Your idea of trying coloured gels is certainly also worth considering. Actually, I've made a primitive filter holder to fit into the rear tube of the DA*200mm (: where the special Pentax teleconverter protrusion would fit in) so, at least for testing, more affordable 1.25" filters can be used. Indeed, exhausting all possible projects with this lens will take a while!
08-10-2013, 04:33 PM - 2 Likes   #640
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M45

My latest image, been slow going as twilight lingers here for most of the night during the summer months.

Pentax K5 IIs
Orion 8" Newtonian
18 x 4 minute exposures @ ISO 400
Attached Images
 
08-10-2013, 07:14 PM   #641
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Nice one Dr
08-15-2013, 04:32 AM   #642
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QuoteOriginally posted by Dr_who Quote
My latest image, been slow going as twilight lingers here for most of the night during the summer months.
Marvellous Dr_who.

What is the f-ratio of your Newtonian?
08-15-2013, 04:58 AM   #643
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The Power of Stacking

With excuses to all of you, who do not need any lectures at all on the benefits of stacking.

Still.....

...when I am idle under my lightpolluted city skies, and waiting for darker skies anyway, I sometimes do silly things such as pointing my DA* 200 f/2.8 lens towards M51, just to see what I get.

Shooting along the well-lit main street over the centre of my town with some major shopping centres near the path:



And of course, the result is as I deserve and as I should expect:


K-5 + smc Pentax DA* 200mm f/2.8 @ f/4 - 20 second exposure at ISO 3200 - tracking by means of Pentax O-GPS1 unit.
100% non-resized crop of original, unprocessed image, (: JPEG straight out of the camera).

Indeed, the fact that M51 is at all, if ever so faintly, visible under these circumstances is a cadeau to the K-5 sensor and DA* 200 optics. But now stack just 10 of these images in DSS and you get this, really without any hard work - just a few, slight twists in curves and levels:


Stack of 10 exposures as above in DSS (with dark-, flat- and offset frames applied).

Of course, this could be MUCH better under a better sky. Still, it is a kind of revelation to me that stacking is indeed so efficient in respect of improving signal-to-noise ratio, even under lousy conditions.
08-15-2013, 07:59 AM   #644
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Nova in Delphinus August 2013

QuoteOriginally posted by Stone G. Quote
With excuses to all of you, who do not need any lectures at all on the benefits of stacking.

Still.....

...when I am idle under my lightpolluted city skies, and waiting for darker skies anyway, I sometimes do silly things such as pointing my DA* 200 f/2.8 lens towards M51, just to see what I get.

....[snip].... it is a kind of revelation to me that stacking is indeed so efficient in respect of improving signal-to-noise ratio, even under lousy conditions.
The waiting period between good skies and the new moon cycle are great chances to work out the kinks in a data capture process. Setup, adjustments, understanding how working in the field matters. It's a chance to perfect dew control systems and try out power supplies. Hone your understanding of tripods, polar alignment, and guiding. Knowing how focus changes with temperature and what the best point for each lens may be is something that can be done even when the moon is full.

I enjoy working on these projects at home because it means that I'll do a better job in the field. It's very frustrating to waste good, dark skies an hour or more away from home because I didn't test out software or methods previously.



On another note, because I already had the gear setup in the backyard, I was able to act fast and snag a few frames of the nova in Delphinus last night. Three frames at 1200 seconds at 100 ISO with the modified, cooled Pentax K10D.

Here is the view of this star that is surging in brightness (up from a mag 13 to currently about mag 6).




Annotated image shows how the star stands out in a rather unremarkable field. Note the planetary nebula in the upper right (NGC 6905). The Tyco catalog markers were rendered to Mag 10, showing that at least for this reference, the star was not noted.



Full size on Astrobin will allow pixelpeeping

Last edited by smigol; 08-15-2013 at 11:03 AM. Reason: Added nova picture
08-15-2013, 11:28 AM   #645
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QuoteOriginally posted by smigol Quote

.......On another note, because I already had the gear setup in the backyard, I was able to act fast and snag a few frames of the nova in Delphinus last night. Three frames at 1200 seconds at 100 ISO with the modified, cooled Pentax K10D.

Here is the view of this star that is surging in brightness (up from a mag 13 to currently about mag 6).

Annotated image shows how the star stands out in a rather unremarkable field. Note the planetary nebula in the upper right (NGC 6905). The Tyco catalog markers were rendered to Mag 10, showing that at least for this reference, the star was not noted.


Full size on Astrobin will allow pixelpeeping
Well, you certainly have your gear, alignment and guiding working. Congratulations on your capture - and what a beautiful planetary too!

But now back to:

QuoteOriginally posted by smigol Quote

- - - - -
I enjoy working on these projects at home because it means that I'll do a better job in the field. It's very frustrating to waste good, dark skies an hour or more away from home because I didn't test out software or methods previously.
I couldn't agree more - and you've said it better than I could.

As you say, training on polar alignment and guding can be done on any night where there are just a few stars in sight.

And most of my optical and mechanical "development" and test project have started on such nights with a remote, dimly lit church tower as "DSO" and outer staircase lamps on an office building as "stars" and "planets". At least for me, trying out new combinations of gear and optics first on stationary targets is the first step in getting the "feel" of and confidence in my partly homemade gear before I venture into the field.
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