Alt/Az unguided astrophotography with a IOptron MiniTower M13 on 08/09/2010 A work in progress....zoom in, you'll see why.
Piggybacked, no guiding, 20 exposures (45 sec @f/5.6 at 300mm on a Canon T2i), stacked with DeepSkyStacker. Cropped to about 1/4th size to reduce the size of the JPG (16mb uncropped) and increase the size of M13 in the frame..
By
zooming in, you'll see the coma in the stars. The picture was taken
wide open with a Canon 75-300mm zoom lens and pretty much convinced me
that piggybacking wasn't going to be a practical option for deep sky
work. I'm happy with the unguided tracking on the IOptron MiniTower
mount. The mount was in Alt/Az and even though M13 was high in the sky
field rotation doesn't look to be too much of a problem. So the Canon
lens looks to be the only downside. [ NOTE: Stopping the lens down does help, but reduces the light that strikes the sensor, which means longer exposures, that leads to field rotation, that leads to star streaks,which....grrrrrr!]
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| Time to experiment!
Back at the beginning of August I bought a cheap ($75) 90mm f/6.1 OTA from Sheldon on CloudyNights to use as a guide scope with a web cam. I thought what the heck...it couldn't be any worse than the Canon lens so I got a 2" prime focus t-mount for the Apogee Inc. --------------------->
Much to my surprise it produced this image of M8 taken on 8/27/2010 just
a few day past the full moon. The Canon lenses will now stay at home!
| | | | | | | | | M8
| | Data:
24 unguided subs of 45 seconds taken with a Canon T2i @ ISO 800, 550mm f.l., f/.6.1 saved a RAW file, contrast adjusted and converted to TIF with Canon's Digital Photo Pro, processed with DeepSkyStacker (DSS), and enhanced in PhotoShop. (additional contrast adjustment, saturation, sharpening, bit reduction, cropping)
Focusing was achieved with a home made Bhatinov mask.
Alignment?
- level the tripod
- level the MiniTower after mounting lens and camera
- rough align to north/south
- slew to Antares (if lucky it will be in the fov)
- center on Antares by turning mount alt/az
- slew to M8... done
As a newbie... I'm happy!
| | Additional notes:
I was actually shooting for 40 subs and then planning on having DSS reject the lowest quality 4 but the T2i battery died after 24 subs. Oh well...
I've also had problems getting a high enough score for DSS to recognize all my RAW subs so I do a bit of preprocessing with Canon's Digital Photo Pro and then save everything as TIFs. I adjust the white level, black level, and change to response to linear. DSS then recognizes hundreds of stars. The only downside is that the T2i's images are huge (18M) and the conversion take quite a while. The additional dark frames, flats, and bias files need to be converted too because for some reason the physical size of the RAWs and TIFs are slightly different.
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| | Images
| | Data, Notes and Comments
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M13
| | Data:
16 unguided subs of 30 seconds taken with a Canon
T2i @ ISO 800, 550mm f.l., f/.6.1 saved a RAW file, contrast adjusted
and converted to TIF with Canon's Digital Photo Pro, processed with
DeepSkyStacker (DSS), and enhanced in PhotoShop. (additional contrast
adjustment, saturation, sharpening, bit reduction, cropping) | |
Lagoon (M8) and Trifid (M20) Nebulas
| | Data:
60 unguided subs of 30 seconds taken with a Canon T2i @ ISO 800, 550mm f.l., f/6.1 taken on Ioptron MiniTower Alt/Az mount saved as RAW files, contrast adjusted and converted to TIF with Canon's Digital Photo Pro, processed with DeepSkyStacker LIVE, and enhanced in PhotoShop (additional contrast adjustment, saturation, bit reduction, rotation, and cropping).
| | M8, M20, and M21
| | Using the Canon 70-300mm at the maximum zoom and cropping to 1/4th the image gave this view of three Messier objects in the same frame.
The coma that I'd experienced earlier has been mostly removed.by stopping the lens down to f/8.
Data:
10 unguided subs of 45 subs taken with the T2i @ ISO 800, 300mm fl. The image was stacked and for the most part processed with DSS. PhotoShop was used to rotate a bad framing of the original, crop to a final size, reduce the pixel count, and save as a jpg.
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Milky Way in Early November
 North is to the left Jupiter is the bright object at the bottom of the frame. More people have commented about this image than all the rest combined. It is a gimmick picture using an uncommon lens.The fisheye also does distort horizontal/vertical lines so the stars are not necessarily where they would be on a star chart. If you need some hints about what is where in the picture scroll down to the bottom of the page for a copy with six constellations drawn in.
| | I've have a variety of lenses for Canon cameras one of which is a Peleng 8mm fisheye. I wondered what it would do on the night sky. I've tried to use it at Broemmelsiek, but there is too much light pollution over St. Louis in the east to give the lens a fair test. On 11/06/10 I made the trip out to Danville and captured the subs to make this image just after dark. The light around the horizon is reflecting off clouds.
I had originally intended to do a guided Alt/Az but there was significant field rotation with 30 second exposures because the camera was pointed straight up. Turning the mount off and not moving the camera during the exposure removed the field rotation. The focal length of the lens is short enough to eliminate star trails
Data:
20 tripod mounted subs of 30 seconds taken with a Canon T2i @ ISO 800, Peleng 8mm fisheye, F/4 saved as RAW files. The subs were stacked with DeepSkyStacker and enhanced in PhotoShop (slight cropping to remove rotation, contrast adjustment, burning the light areas of the horizon, saturation, bit reduction)
| | Cygnus
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One of the things I've wanted to do for a while is to shoot constellations via piggy back. I could mount the typical Canon 18-55mm zoom, but it is a bit slower than some of my old Canon FD lenses. Additionally with a zoom I have a tendency to frame, but ignore the focal length so I really don't have a clue as to real field of view. On 11/06/10 I explored Cygnus, Perseus, and Cassiopeia with a Canon FD 28mm f/3.5 lens.
Data:
All three are from 20 subs of 30 seconds taken with a Canon T2i taken at F/4 saved as RAW files and stacked with DSS. The images were enhanced with PhotoShop where the stick figures were added.
It was actually kind of fun doing the stick figures. Although I did have to turn down the contrast to be able to see the trees from the forest.
I think I'll try to add a few more constellations each month, all taken with the 28mm lens, and eventually turn everything into a separate page.
It might be a good idea to somehow highlight various deep sky objects (like the Double Cluster in the Perseus image) for future reference.
The images are hard to see here because of the white background. I have not yet determined how to change the page background to an image or black, so click on the pictures to see them at their best.
| | It seems that the Apogee is a bit to tele for some objects so I've cleaned up my 35 year old Vivitar 400mm f/6.3 FD Canon mount lens. It has a bit of coma wide open but stacking multiple images seems to remove the problem. Since it is an FD lens it does need a FD to EOS adapter to mount to my Canon T2i.
It has I believe a T4/TX mount adapter and can frequently found on EBay for less than $30. I actually have two and Jim Roe is using the other with the club's Canon T1i.
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M31, M32, M110
| | The seeing at Danville on 11/06/10 was excellent. After I took the subs for the full sky and constellations I kept shooting until all my batteries were dead. The last object was M31 and friends. By the time I started the subs the only batteries left were in the camera and drive. I attempted to frame M31 through the camera's viewfinder and on the LCD. The subs were taken using an Ebay wired remote timer.
Data:
Thirty one minutes subs were taken with a 35 year old Vivitar 400mm lens @ F/6.3 (wide open) using a FD-->EOS adapter on a Canon T2i. The subs were stacked with DSS and a very lightly processed with PhotoShop (very minor crop to square frame, auto contrast adjustment, and slight curve modification).
There is some coma but I like the results.
| | | | | Well good news and bad. I was determined to learn how to use the basic post-stacking options with DeepSkyStacker so I played with the Danville M31 stack. The only thing I did in PhotoShop was the crop to even up the frame and a slight darkening of the background. Everything else was done via DDS and I can say I finally know what the histogram should look like and what the various luminance tools do. I do like M110 in the picture.
The bad news... I didn't have M31 centered and it runs off the top of the picture AND there are some strange dark horizontal lines in the image. They may be remains of cleaning marks on the filter over the sensor?? If so, flats should remove the problem in the future. If not it is banding.
Over the top on processing...probably, but impressive.
| | M42
| | Before the batteries on the laptop died I took a number of sequences of M42 at different times. This image was made by combining 40 one minute exposures taken with the Vivitar 400mm lens using an Alt/Az mount.
Data:
Same as above with 40 subs. A bit heavier processing with PhotoShop to bring out detail in the fainter areas and preserve as much detail as possible in the light central areas.
I'll probably see if combining images from shorter exposures (15 sec subs and 30 sec subs) can improve the over exposed central core.
| | M42 with stacking
| | The results from PhotoShop combining the DSS 1 minute exposure image with the 15 second exposure image. The central core area of Trapezium is better, the stars are worse.
Interesting discoveries along the way...
- The combined TIFs are different sizes based on DSS "mosiac"
- The DSS TIFs are a bit rotated vs each other because of my Alt/Az mount. This causes stretched out stars in places.
- Combining multiple TIFs pushes the limits of my little netbook's memory and processor.
I need to play more to see if PhotoShop stacking is worth the effort. I should also try to do the combining with DSS;
| | | | | Data:
51 unguided subs of 50 seconds taken with a Canon T2i @ ISO 800, with a 550mm OTA @F/6.1 saved a RAW file, stacked with DeepSkyStacker (DSS), and enhanced in PhotoShop. (additional contrast adjustment, saturation, sharpening, bit reduction, cropping).
Hmmmm.... I cropped the image to 1/4 the original size using PhotoShop. The crop removed surrounding sky and enlarged the Dumbbell in the image on the left. In effect, the resulting image is I believe what would be photographed using an 1100mm F/6.1 system
| | M45
| | Twenty one minute exposures through the Vivitar 400mm lens wide open at F/6.3 from Danville on 11/6, stacked with DSS and processed with PhotoShop. I'm disappointed with the lack of nebulosity on such a dark night and under such good seeing conditions. More subs? I really can't expose each sub any longer because of field rotation.
After I learned more about the RGB and luminance tabs in DSS playing with M31, I went back and restacked the M45 subs. I'd seen pictures of the nebulosity in M45, but I had never been able to bring it out in a photograph or with &PhotoShop without killing the background. After a few minutes doing some post processing in DSS I got this. Really... the same picture, a bit more cropping, but really the same set of subs. The orientation of the star pattern is the same.
The key here was to bring what I'll call the mid-section of the HD curve (Ansel Adams Zone System reference) up through the middle of the histogram with the greatest possible slope. I also extended the highlight region as far up as I could. I actually tuned the nebulosity down a bit in PhotoShop because it emphasized the "black" banding lines.
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| After an almost 3 month weather related delay:
| | | | It has been a long, cloudy winter and I spent a good deal of time learning, reviewing, restacking, thought and practicing. While Alt/Az can give me results, I've pretty much decided to put my MiniTower on a wedge and head towards autoguiding using the SDC-435 and 1-2 minute exposures from Broemmelsiek. Along the way I had the IR filter in my older Canon XT (350D) removed and replaced with clear glass. I'll be using either a 1.25" Baader IR/UV or 58mm B&W IR filter for images now. The Baader will be used with the Apogee and C8.. The B&W with my Canon lenses. I've added a new laptop that runs circles around my netbook. I'll use the netbook in the field, but stack and process on the laptop. Two other Baader filters (Semi-APO to correct the color fringing on the Apogee and Light Pollution) and a focal reducer completed the additions. Eventually I'd like to use the club's C14 with the focal reducer and SDC-435 to do some planetary nebula work, but those results will be posted on my SDC-435 page.
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My first real night out that produced any results with the Canon XT was Feb 27-28 at Broemmelsiek. I was more in the mood to test the XT than play so while the MiniTower was on a wedge in EQ, I didn't try auto guiding. I took three sets of exposures and I'm pretty happy with the results you can see below:
| | Alnitak and Friends
| | Data (same for all three images)
60 unguided subs of 45 seconds taken with a Canon XT@ ISO 800, with a
550mm OTA @F/6.1 using Baader IR/UV and Baader Semi-APO filters, saved a RAW files, stacked with DeepSkyStacker (DSS),
and enhanced in PhotoShop. (additional contrast adjustment, saturation,
sharpening, bit reduction, cropping, and heavy use of Astronomy Tools actions).
| | M42 | | Data:
Same as above
To see how well the Baader Semi-APO filter works you might want to compare this image with the one of M8 above.
I'll be using the Semi-APO anytime I use the Apogee.
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| | Data:
Same as above
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Hints:
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