The World of Astronomy

The Rosette Nebula in Monoceros 24-Nov-2020 using the Optolong L-eXtreme filter

2020-12-09T08:51:00.009-07:00

I've been having a "field day" with the recent Optolong L-eXtreme dual band filter. I had already owned the L-Pro and L-eNhance filters and am of course very pleased with them as well. An example comparison can be seen here.

But, the Rosette Nebula really shows off the L-eXtreme's capability and that can be seen below.

And a full resolution TIF verson can be found here.

Although I wouldn't give up my L-Pro and L-eNhance filters, I'm eXtremely pleased with this filter.

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Starizona SCT Reducer/Corrector II

2019-04-25T07:06:00.000-07:00

Yesterday (04/24/2019), I received and installed the new Starizona SCT Reducer/Corrector II.

https://starizona.com/store/starizona-sct-corrector-ii-0-63x-reducer-coma-corrector

Note the diagram showing spot sizes, under Performance.

I think this development is significant since up to know I was considering swapping my NexStar 8SE for an 8" EdgeHD, with the 0.7x reducer, all very pricey, as you know.

What Starizona's new reducer/corrector does is combine both features (reducer and corrector) into one product and I'm very pleased with the results.

Configuration details and sample images can be found here:

https://pbase.com/wjshaheen/configuration20190424__celestron_nexstar_8se_on_the_celestron_

Bill

/William Shaheen/

Superstition Mountain Astronomical League®

Comet 46P/Wirtanen 12-Dec-2018

2018-12-14T18:53:00.000-07:00

33 - 60 sec exposures, with a 30 sec interval, at ISO 1600.
16 bias frames applied.
Temp 45°F - 49°F.
Taken between 9:48pm and 10:42pm MST.
Nikon D7500; Sky-Watcher Esprit 120mm, f/7; Orion HDX110 mount.
Optolong L-Pro filter.

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

The Eskimo Nebula and Comet 38P/Stephan-Oterma 08-Nov-2018

2018-11-14T09:25:00.001-07:00

While imaging the Eskimo Nebula (NGC2392), I noticed a blurry object to the lower right. Turned out to be periodic comet 38P/Stephan-Oterma currently in the constellation Gemini. Magnitude 9.27.

Collected 16 frames, ISO800. Seeing was excellent at ~2 arc-seconds when starting at ~ 03:03am.

Coordinates (J2000) 07h 27m 33.4113s +20° 48' 34.070"

Sky-Watcher Esprit 120 (840mm) and Nikon D7500.

Meteor strike in next to last frame at 04h43m55s.

Also, below and to the left of the planetary nebula is magnitude 18.46 asteroid (45234) 1999 XA228.

20181108_NGC2392-Comet_38P-25pct.gif

(Click on the image for a larger version.)

And here is a single frame (cropped) to highlight the nebula itself.

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Comet 21P/Giacobini-Zinner and Companion Clusters 15-Sep-2018

2018-09-16T04:13:00.003-07:00

In the early morning of September 15, Comet 21P/Giacobini-Zinner could be seen cruising in front of open star cluster M35 in Gemini. To its lower right is another fine cluster, NGC 2158.

Here is one of the frames taken for the video.

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Atmospheric Dispersion Correction in Image Post Processing

2018-07-21T13:18:00.000-07:00

Atmospheric Dispersion Correction in Image Post Processing

The Earth's atmosphere refracts light of different wavelengths to a different degree, depending on an object's altitude above the horizon, hence declination dependent. I.e., the Earth's atmosphere acts as a prism.

Consequently, objects at the zenith will not have this effect, since the light from that position are perpendicular to the Earth's surface (and atmosphere) at that point.

This image shows the effect of atmospheric dispersion by the lower edge displaying a red tinge and the upper edge a bluish tinge.

The next 3 images show the individual frames after separating the channels using Michael Unsold's venerable ImagesPlus ( http://www.mlunsold.com/ ).

Red channel

Green channel

Blue channel

The image below is a GIF showing the vertical displacement between the individual RGB frames.

3 frame GIF

Finally, the result of aligning then recombining the individual frames, again, with ImagesPlus.

Result of colors split, aligned and recombined

With compliments to Mike.

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

M57 - The Ring Nebula 04-Jul-2018

2018-07-05T09:00:00.001-07:00

Seeing was reasonably good last night at ~2.47 arcseconds (as measured by image link).

Ambient temp 85°F. I believe it will take a cooled camera to eliminate the red streaking.

The images were taken when M57 was just about at the zenith - clearer, darker and no atmospheric color dispersion, as is encountered when imaging planets.

Tracking was excellent, between 0.44 and 0.50 arc-seconds.

Bill Shaheen

Superstition Mountain Astronomical League®

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Elements of Astrophotography - Calculating Image Scale/Field of View

2018-07-02T04:24:00.002-07:00

Elements of Astrophotography - Calculating Image Scale/Field of View

The general formula for determining the Field of View (FOV) for a light collecting area, whether at the pixel level or for the overall imaging area is:
206,265 x pixel (or sensor) size / focal length of the telescope (or lens).
(See Note 1 at bottom.)

For the purposes of our calculations, it is simpler to use 206.265 with the pixel size expressed in uM. For example, my Sky-Watcher Esprit 120 refractor has a focal length of 840mm and my Nikon D7500 has a pixel size of 4.2 uM.(See below for determining your camera's pixel size.)

Hence, the per pixel FOV (aka image scale) is 206.265 x 4.2) / 840mm = 1.03 arc-seconds, sometimes expressed as as/p (arc-seconds per pixel).
The above assumes square pixels, of course, which is usually the case these days.

At the chip level (or for non-square pixels), the horizontal (width) and vertical (height) fields of view need to be determined separately.
I.e., (206,265 x sensor array in mm (width or height) / FL) / 60.
E.g., the Nikon D7500 sensor array is 23.5mm (w) x 15.7mm (h).
(You may frequently see these terms interchanged - h x w.)

So, Horizontal FOV = ((206,265 x 23.5) / 840) / 60 = 96.175 arc-minutes.
(If you encounter an intermediate overflow error, use 206.265 and multiply the result by 1000, or get a new calculator.)

As an alternative, simply multiply the per-pixel FOV by the array size on each axis.

Solving for either FOV or image scale

Now, the question may be posed, what camera or telescope should I choose to achieve an image scale of, say, 1 arc-second? And, it's a great question, since you may want to design your imaging system to provide a particular per pixel image scale or an overall field of view.

In that case, you simply want to substitute your desired FOV (or image scale) in the above equations and solve for either pixel size (or sensor size) or image scale.

You need to choose one or the other. For example: Since as/p = (206,265 x uM) / FL, then (206,265 x uM) / image scale = FL.

Or, you may already, and typically do, have a particular telescope that you already own and want to identify a camera based on its pixel size, or close to it, in which case, (image scale x FL) / 206265 = uM.

In my case, I'll target an image scale of 0.8 as/p (as opposed to the above 1.03as/p). So, (0.8 as/p x 840) / 206.265 = 3.25um (which is a commonly available image scale).

Now let's look at arriving at an overall FOV (horizontally).
Horizontal FOV is ((206,265 x sensor width in mm) / FL) / 60 = Width FOV in arc-minutes. Note that this calculation is independent of the individual pixel size. The entire sensor is the image collecting area.
In other words, image scale in arc-seconds per pixel determines resolution, where as chip size determines overall field of view.

Again, we assume the FOV and solve for FL.
So, to repeat ((206,265 x sensor width in mm) / FL) / 60 = Width FOV.
sensor width in mm = (FOV (in arc-minutes) x FL x 60) / 206,265.

Example: (96 arc-min X 840FL X 60) / 206,265 = 23.45mm on the chip's horizontal side.

Calculating Pixel Size from camera specs

In some cases you may not know the camera's pixel scale, although that data can be had from the manufacturer's specifications, or from third party resources. But, just to illustrate, simply divide the chip's width in mm by the number of pixels along that axis. The D7500 has an array of 23.5mm x 15.7mm and the pixel count is 5600 x 3728. (In the days before square pixels, you had to make two calculations. Now, one is sufficient.)

So, 23.5mm / 5600 = 0.004196 mm per pixel, or, 4.196 uM per pixel.

Or, use a calculator

Of course, there are a number of calculators on the web that can do this for you. One such calculator that you can download is Ron Wodaski's CCD Calculator

http://www.newastro.com/book_new/camera_app.html .)

Another, on-line calculator is http://www.12dstring.me.uk/fovcalc.php .

Note 1
206265 is the number of arc-seconds in a radian. See: https://en.wikipedia.org/wiki/Minute_and_second_of_arc

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Elements of Astrophotography - Chip Size, Pixel Size, Dawes' Limit and the Nyquist Theorem - Obey

2018-06-18T13:33:00.000-07:00

Following a recent Friday morning meeting of the Superstition Mountain Astronomical League, a few of us convened for an impromptu astrophotography mini-clinic.

To recap, we demonstrated that chip size determines overall field of view (FOV) whereas pixel size determines resolution, in arc-seconds per pixel (as/p). We then showed how they are derived for various telescope/camera combinations.

Clarification

Following the meeting, I found I needed to make a distinction between the source signal resolution and the image capture resolution.

For example, my Sky-Watcher Esprit 120, with an aperture of 4.73 inches, produces, according to Dawes' limit, a maximum resolution of 4.56/4.73 = 0.96 arc-seconds per pixel (as/p).

What that 0.96 as/p represents is the maximum resolution produced by the optical system (again, according to Dawes) and hence becomes the maximum resolution that is available to the recording system (i.e., the chip) and projected onto the image sensor.

Now, shown below is the calculated image scale for the Nikon D5300 when coupled to the Sky-Watcher Esprit 120.

(Screen above produced from Ron Wodaski's CCD Calculator

http://www.newastro.com/book_new/camera_app.html .)

Now, you may notice that the calculated image scale is 0.94 as/p. Note also that Ron Wodaski's CCD Calculator, excellent as it may be, does not show Dawes' limit for the proposed telescope - just the final calculated image scale telescope/camera combination in question.

And, here is a sample photo taken with this configuration using the Nikon D5300 (IR filter removed).

In this photo, the image scale of 0.94 as/p is very close to the 0.96 as/p Dawes' limit for the telescope, the Esprit 120. In fact, when I upgraded from the Nikon D5300 to the D7500, I was pleased that the image scale (1.03 as/p due to slightly larger pixels) still matched so nicely. And, with our typical seeing of around 2 arc-seconds (on a good night), I should be happy.

But, here's the rub ....

Complication

While driving to the post office after the meeting, it occurred to me that another, important consideration needs to be taken into account when determining the components for your target image scale - the Nyquist sampling theorem, or simply the Nyquist theorem. Basically, the theorem states that to adequately convert an analog signal to digital (sampling), you need to sample at a frequency of at least twice the frequency of the source signal.

This is more commonly understood in the context of audio recordings but applies to other forms of signal as well.

So, either the 0.94 as/p for the D5300 (or the 1.03 as/p for the D7500, which we will see) should be sufficient to capture images when the seeing is, say, 2 arc-seconds, which is infrequent and why those scales work under most circumstances.

But, my aim has been to record at roughly 0.5 arc-seconds/pixel in order to take advantage of those rare times when the seeing is close 1.0 arc-seconds. Ok, probably won't happen but we may very occasionally experience 1.5 arc-second seeing.

And, by imaging at the tighter scale of 0.5 as/p, I would in effect be sampling at 4x the source signal, when we have 2 arc-second seeing.

Now, that 4x may amount to what's called oversampling and I have seen a recommendation of 3x in various astrophotography forums.

Enter the 8 inch

Now, lately I've been testing the Celestron NexStar 8SE, which yields a 0.43 as/p image scale (with my current camera, the D7500).

And that more than satisfies the Nyquist sampling requirement for 2 arc-second seeing. The trick is to autoguide the combination without having to resort an in-line off-axis-guider (OAG) and instead use a separate guide scope mounted piggy-back on the OTA.

I'm still working out the wrinkles in that configuration and am strongly considering the EdgeHD version with a 0.7x focal reducer which yields a more comfortable 0.61 as/p, as shown below, which would meet the Nyquist requirement at 1/3x 1.8 arc-second seeing. Close enough.

(Screen above produced from Ron Wodaski's CCD Calculator

http://www.newastro.com/book_new/camera_app.html .)

Now, I've also been considering the Celestron 9.25inch EdgeHD, along with 0.7x focal reducer. Coupled with the Nikon D7500's 4.22um pixel size, that combination would yield an image scale of 0.53 as/p. And Parijat would be so pleased. But, I'm also considering a future camera having smaller pixels and so will probably end up with the much less expensive 8 inch EdgeHD (and less expensive focal reducer).

For you own experimentation, here is a link to Ron Wodaski's CCD Calculator.

Stay tuned for a prequel on how to calculate image scale at the pixel or chip level.

William Shaheen

Superstition Mountain Astronomical League®
Gold Canyon, Arizona

http://supermtnastro.com/

June, 2018

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Jupiter with GRS 24-May-2018

2018-05-25T06:06:00.002-07:00

Jupiter - GRS Transiting at 9:23pm MST. (SkySafari)
North is up; East to the left.
Image capture at 9:27pm MST.
Temp 75°F at 10:45pm.

Celestron AVX mount; Celestron NexStar 8SE; Baader 2" Clicklock SCT adapter; Televue 2" ext tube;
No Barlow; Celestron NexImage 5 Planetary Imaging Camera. iCap 2.4 image capture, 640x480 unbinned capture; Capture image scale 0.23 arc-seconds/pixel.

Processed in RegiStax 6.1; Adjustments in ThumbsPlus 10; Resized to 50%.

Original video available on YouTube at https://youtu.be/yDx6WVlF9gY

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

M42 - The Orion Nebula in HDR 01-Oct-2017

2017-10-01T12:50:00.000-07:00

M42 - The Orion Nebula in HDR 01-Oct-2017

High Dynamic Range Orion Nebula at various exposures, HDR combined using Aurora HDR 2018

http://www.pbase.com/wjshaheen/image/166308209/large

Shot between 4:50 and 5:15am. The satellite tracks can be avoided by shooting earlier, or later, depending on the time of year. At the time the images were taken, M42 was in line with the satellites.

Kinda cool, actually.

The Power of Post Processing

2017-09-27T07:35:00.001-07:00

I've been toying with a variety of photo editing programs and in the following image, I really boosted the "clarity" (contrast) of an M31 image I recently posted, as seen here.

Admittedly a bit "grungy", or noisy if you prefer, but notice how much more detail is brought out around the galaxy's core, as well as the dust lanes.

The devil is in the details - and so are the data. :O)

(Adjusted in Topaz Studios /http://www.topazlabs.com/ )

A larger size of the above comparison can be seen here.

And here is a larger version of the new image.

What with Solar Minimum approaching ...

2017-09-03T08:53:00.000-07:00

This isn't supposed to be happening - a "plethora" of sunspots.

Screen on left side is from Spaceweather.com.

Solar image taken 03-Sep-2017.

Explore Scientific ES102ED FCD100 with ATR8 focal reducer.
Nikon D5300a

All post processing in ViewNX 2.
Cropped but not downsampled (no binning).

See also http://www.pbase.com/wjshaheen/image/166131800/large

Solar Eclipse 2017 - Eclipse Photos

2017-08-26T13:02:00.002-07:00

Solar Eclipse 2017 Eclipse Photos - from Hartsville, Wy.

See http://www.pbase.com/wjshaheen/solar_eclipse_2017_eclipse_photos for further details.


		Star chart generated by TheSky Astronomy Software (c) Software Bisque, Inc. All rights reserved.

Preparing for Solar Eclipse 2017 - White Balance Check

2017-07-24T13:17:00.001-07:00

All digital cameras contain an IR (Infrared) filter in front of the chip, be they CCD or CMOS. By having the IR filter removed, the naturally occurring infrared produced by vegetation emerges. (A custom white balance is required to restore the color balance of non-IR emitting objects, such as the rocks in the background. I'm still working on that.)
Some astronomical objects, such as emission nebulae, also emit Hydrogen Alpha (Ha) and an IR modified camera picks up that signal more so than a standard camera. The photo on the right shows what the plant should look like, appropriately named a Blue Agave. Tequila anyone?

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Preparing for Solar Eclipse 2017 - Sunspot AR2665

2017-07-22T05:29:00.003-07:00

While preparing for the upcoming August 21st solar eclipse, Sunspot AR2665 was captured with the Nikon 300mm f/4 ED IF and Sigma 1.4x tele extender. Taken 15-Jul-2017, zenith is up. Reduced to 50% (i.e., 2x2 bin).

DSC_0977-50pct-IPadj.JPG

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Saturn at Opposition 16-Jun-2017 (and maximum ring tilt)

2017-06-16T14:06:00.001-07:00

Taken @ 12:18:52pm MST on 16-Jun-2017 (0718UT on 16-Jun-2017).

Here is Saturn at Opposition 16-Jun-2017. For views of what Saturn has looked like over the course of the last 13 years, see http://www.pbase.com/wjshaheen/saturn_ring_tilt

Best 90 of 1800 frames (5%) taken with the Celestron NexImage5 planetary imaging camera, Celestron 1100 EdgeHD telescope, no barlow, no focal reducer, fl = 2800mm. Image scale 0.16 arc-secs/pixel. Video captured using iCap 2.4, processed in ImagesPlus6.5. Three passes unsharp mask, cropped and contrast boost in ThumbsPlus 10. North is up and east is to the left, as customary.

Original video available at https://youtu.be/QSgeqaykAgw

CVT_20170615_Saturn0005 00-17-07-GRADEAVG-Best5Per-2AP-TPadj-50pct.jpg

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Switching the C11HD to Visual - My Digital Finder

2017-06-12T13:30:00.000-07:00

AKA - What's that eyepiece doing in my telescope?

I haven't really enjoyed any visual observing for awhile (couple months) and wanted to catch Jupiter in the 11" EdgeHD. So, I came up with this project. Ordinarily it would be a simple matter of removing the imaging train and installing a diagonal and eyepieces. But, this turned into an expanded project.

For one thing, without the camera on the scope, I would be unable to perform image links when finding objects.

This project resolved that by replacing the finderscope on top of the C11HD with the autoguider (scope and camera) from the AVX platform (WFPIP).
So, I made that transfer yesterday, the 11th. (11-Jun-2017)

Below are my diary notes for the 12th.

06/12/2017
Had a very successful morning converting the C11HD to visual.

I wanted to use the SV50 guidescope with the QHY5L-II autoguider on the C11HD to be used as a finder by image linking in TSXPro.

Found I could easily perform an image link using the QHY5L-II/SV50 autoguider combination, along with the Orion 2x Shorty Barlow.
Image link stats indicated a scale of 3.60 as/p, with the camera binned in the ASCOM set-up.

Used Venus to align this "digital finder".

Later, played with using the SV50 guidescope with QHY5L-II autoguider to autoguide to test the ability to use as a separate autoguider and possibly eliminate the OAG.

That would be nice. But, that's another project for another day.

After aligning the "digital finder"* with the main scope using Venus, I was able to use TSXPro to locate the galaxy by image linking on the autoguider's image by taking an exposure in TSXPro using the autoguider camera (QHY5L-II).

*QHY5L-II/SV50 autoguider combination, along with the Orion 2x Shorty Barlow.
Image link stats indicated a scale of 3.60 as/p, with the camera binned in the ASCOM set-up.

M31 appearing in the PHD2 screen, using 0.5 sec exposures. The QHY5L-IIM was configured to bin 2x2 in the ASCOM setup, yielding a combined pixel size of 7.5um and an image scale of 3.60, with a 2x Barlow.

Plate solution (per TSXPro):
******** ASTROMETRIC SOLUTION RESULTS ********
Center RA (2000.0): 00h 41m 45.34s
Center Dec (2000.0): +40° 39' 29.8"
Scale: 3.60 arcseconds/pixel
Size (pixels): 640 x 480
Angular Size: 0° 38' 25" x 0° 28' 48"
Position Angle: 2° 31' from north through east
Mirror Image: No
RMS: 1.58 (X: 0.92 Y: 1.29)
Number of Stars Used in Solution: 7 (100%)
FWHM: 4.21 pixels, 15.16 arcseconds
***********************************************

Autoguiding with the "digital finder". (Taken 4:31am - getting light out.)

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NGC7331 - Season Finale

2017-06-05T05:56:00.000-07:00

Between the Moon setting so late in the morning, ~3am, and the Sun rising so early (astronomical sunrise 3:35am), there's not much time to grab many exposures. And next month's monsoon will pretty much dampen any chances of imaging. But, you know, you can always sneak in one last shot (image above).

A single 8-minute exposure @ ISO800. (The sky was much brighter than what you see here and so a needed contrast adjustment muddied the picture a little.)

So, this is probably it until the Fall, as far as imaging with the C11HD. By the way, the mount (Orion HDX110 has really smoothed out, probably due to the gears being run-in. Here's the autoguiding graph (image right).

Total error 0.44 arc-seconds, which accounts for the detail in the galaxy.

In the meantime, I'm working on my "WFPIP" (Wide Field Portable Imaging Platform) and hope to take it up to Happy Jack next month. It's the platform I used to take the recent images of M8 and M20, the latter of which was taken running the rig solely from a battery.

More to come,

William Shaheen
Gold Canyon, AZ

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

M20 - The Trifid Nebula 04-Jun-2017

2017-06-04T14:00:00.001-07:00

Single frame. 120s @ ISO800.
ES102ED FCD100 with the ATR8 yielding f/l=573mm @f/5.6, taken with the Nikon D5300a.

PREVIEW_20170604-02h51m16s899ms-TPadj2-IPadj.JPG

Saturation; Lightening and Contrast in ImagesPlus. Followed by color balance, ARL 5x5x5, contrast via micro curves, in IP.
One pass unsharp mask and resized to 50pct in TP.

Keywords:
120sec;ARL 5x5 5x;AS/P=1.44;Bias=9;bin-1x1;Celestron Advanced VX;Configuration-20170601;Cropped;Darks=0;Dithered not;ES102ED FCD100;f/5.6;FL=573;Flats=0;fr=Astro-Tech ATR8;IR-Mod;ISO=800;M020;n=1;Nikon D5300a;PBase;PREVIEW_20170604-02h51m16s899ms-TPadj2-IPadj;Resize=Not;Show;Slideshow Astro;Uploaded;

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M8 - Testing the Astro-Tech ATR8 focal reducer 03-Jun-2017 (contrast enhanced)

2017-06-04T13:58:00.000-07:00

Single frame. 300s @ ISO400.
ES102ED FCD100 with the ATR8 yielding f/l=573mm @f/5.6, taken with the Nikon D5300a.

Note tumbling satellite trail caught in upper right corner.

PREVIEW_20170603-02h48m09s778ms-TPadj.jpg

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M8 - The Lagoon Nebula with NGC6544 27-May-2017

2017-05-28T07:40:00.001-07:00

This is the UNreduced version (no focal reducer) using the ES 102ED FCD100 which incorporates Hoya glass.

Distance 4,100ly, in Sagittarius (per https://en.wikipedia.org/wiki/Lagoon_Nebula)

Telescope configuration: Explore Scientific ED102 FCD-100 Air-Spaced Triplet with no focal reducer (baseline for future comparisons (fl=714mm, f/7.0).
Camera: Nikon D5300a (IR-modified). Exposure data: 4 - 300 second exposures at IS400.

Image capture scale: 1.15 arc-seconds/pixel (i.e., un-binned). Field of view = 1° 55' 30" x 1° 17' 06". Image capture using TSXPro Camera Add On (Software Bisque) via BackyardNikon.

Mount: Celestron AVX German equatorial mount (HyperTuned by Deep Space Products), unguided.

Post processing: ImagesPlus 6.5: NEF conversion and calibration, alignment, stacking/combining using 0 dark frames, a 9 bias frame master and 0 flat frames, DDP; Hue, Saturation; Luminance (HSL) in ImagesPlus Image Processing 6.5.
One pass unsharp mask in ThumbsPlus.

No cropping; resized to 50pct. Final image scale/resolution 2.30 as/p.

20170527_M8_CombExcAvg-IPddphsl-TPadj.jpg

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

Sun Compass - How to do a daytime polar alignment

2017-05-25T05:11:00.000-07:00

One of the challenges of setting-up telescope equipment at a public star party is you need visible stars in order to polar align your telescope mount. But, it's just at that time that the visitors are curious and want to ask questions, God bless 'em.

So, for some time now, I've used the azimuth of the Sun (from the SkySafari Info screen below) to set-up my tripod before dark, or at any time of day, say for a solar observing event, such as an eclipse.

When the sun angle is 270° (Sun directly West), it's a piece of cake - arrange the two southward facing legs so that the shadows overlap. (See Morning Example, below.)

But, what do you do between Fall and Spring, when the Sun doesn't reach as far North as 270°? And, what if you want to set-up any other time of day? Maybe you waited too late and missed the 270° mark?

So, using the azimuth of the Sun reading, found in SkySafari, I used this contraption to line up it's shadow with the SS reading of 276° and 4 min.

Now, for this to work, one has to reverse the cardinal direction readings, since you want to point to where the Sun's shadow is coming from. Hence, 270° is on the right (east, as I'm looking at it). North is up.

Also note this is not affected by the Equation of Time since that is figured in with the SS azimuth reading.

So, all one has to do is set this sun compass under or near your tripod, orient the shadow to agree with SkySafari's listed azimuth of the Sun (or, whatever source you customarily use) and aim your third tripod leg to where North is indicated.

Now, we just need a Star Party.

Morning Example - taken when the Sun was at an azimuth of 75°.

Update: 01/29/2019
I've generated an actual compass diagram with increments to 1°. If everything looks reversed, remember - it's a sun SHADOW compass.

Feel free to download and print.

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

M8 - The Lagoon Nebula 23-May-2017

2017-05-25T04:26:00.000-07:00

Distance 4,100ly, in Sagittarius (per https://en.wikipedia.org/wiki/Lagoon_Nebula)

Telescope configuration: Explore Scientific ED102 FCD-100 Air-Spaced Triplet with the Explore Scientific 3" 0.7x focal reducer (fl=500mm, f/4.7).
Camera: Nikon D5300a (IR-modified). Exposure data: 10 - 30 second exposures at IS100.

Image capture scale: 1.63 arc-seconds/pixel (i.e., un-binned). Field of view (horizontal) = 158.9 arc-min. Image capture on-board camera controls with IR-remote.

Mount: Celestron AVX German equatorial mount (HyperTuned by Deep Space Products), unguided.

Post processing: ImagesPlus 6.5: NEF conversion and calibration, alignment, stacking/combining using 0 dark frames, a 9 bias frame master and 0 flat frames, Sigma Median Reject combined,
DDP, noise reduction in ImagesPlus Image Processing 6.5.
Adaptive Richardson-Lucey deconvolution (5x5 by 5 passes) in IP.

Cropped to final dimensions and resized to 50pct. Final image scale/resolution 3.26 as/p.

20170523_M8_CombSigMed-IPddp-IPadj2-NEBcrv-TPadj2-IPclr.jpg

For camera conversion services, i.e., having your DSLR "IR Modded" (IR filter removed), visit Life Pixel Camera Conversion Services here

The World of Astronomy

The Rosette Nebula in Monoceros 24-Nov-2020 using the Optolong L-eXtreme filter

Starizona SCT Reducer/Corrector II

Comet 46P/Wirtanen 12-Dec-2018

The Eskimo Nebula and Comet 38P/Stephan-Oterma 08-Nov-2018

Comet 21P/Giacobini-Zinner and Companion Clusters 15-Sep-2018

Atmospheric Dispersion Correction in Image Post Processing

M57 - The Ring Nebula 04-Jul-2018

Elements of Astrophotography - Calculating Image Scale/Field of View

Now, the question may be posed, what camera or telescope should I choose to achieve an image scale of, say, 1 arc-second? And, it's a great question, since you may want to design your imaging system to provide a particular per pixel image scale or an overall field of view.

Or, use a calculator

Elements of Astrophotography - Chip Size, Pixel Size, Dawes' Limit and the Nyquist Theorem - Obey

Jupiter with GRS 24-May-2018

M42 - The Orion Nebula in HDR 01-Oct-2017

The Power of Post Processing

What with Solar Minimum approaching ...

Solar Eclipse 2017 - Eclipse Photos

Preparing for Solar Eclipse 2017 - White Balance Check

Preparing for Solar Eclipse 2017 - Sunspot AR2665

Suggested Reading

Saturn at Opposition 16-Jun-2017 (and maximum ring tilt)

Switching the C11HD to Visual - My Digital Finder

NGC7331 - Season Finale

M20 - The Trifid Nebula 04-Jun-2017

M8 - Testing the Astro-Tech ATR8 focal reducer 03-Jun-2017 (contrast enhanced)

M8 - The Lagoon Nebula with NGC6544 27-May-2017

Sun Compass - How to do a daytime polar alignment

M8 - The Lagoon Nebula 23-May-2017