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Nov 07 Sketching Target

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#1 LivingNDixie


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Posted 29 October 2007 - 05:27 PM

NGC 7789 will be this November's sketching target. NGC 7789 is a beautifull open cluster in Cassiopeia. I have included a link to more information on the cluster here . The link includes RA Dec coordinates for y'all that use setting circles. This link link includes star chart for the starhoppers in the crowd!

Can't wait to see some sketches and remember to include:

- tips on how to observe that object, filters or other equipment used

- media tried and tested for your renderings

- mini tutorial with an explanation and or/photos on how you did created the observation sketch

- link to any reports involved with the target, after all, these are observation sketches and links to reports will help all of us learn the object better as well as learn what to look for and how to optimize your viewing/sketching session

- or finally, just the sketch itself so we can all see each other's works in progress

link to helpful information about previous targets

#2 WadeVC



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Posted 31 October 2007 - 03:43 PM

I decided to create a mini-tutorial that includes most of the major steps involved in digitizing this sketch. I will divide this post into my impressions of the object, the tutorial, and then my final sketch.

My impression:

I was not prepared for this stellar gem and all the stars that it contained. I started observing this object at around 2000 hours (8pm PDT) in hopes of getting to it before the Moon made its presence known. I just sat and peered at this OC for about 20 minutes before even putting pencil to paper. Just prior to starting my sketch, I thought maybe there was some gunk on my EP; but as I continued to look, it occurred to me that this “gunk” were actually some dark lanes criss-crossing through the heart of the cluster!
Man I love my 10” lawn-cannon!!

Just looking at this vast OC, I knew it was going to be a challenge to sketch this; so many stars, and I mean a LOT of stars, most of them extremely faint. There were so many stars in this cluster that it actually looked like a faint glow of pinpoints of light. Very impressive OC.


The original sketch took me almost 3 hours, and the digitized sketch about the same, possibly a little longer due to capturing screen shots so I could visually show the process to fellow sketchers here on the CN Forums. I started digitizing this sketch last night and finished this morning. The date reflects the dates from the original sketch to the finished digital sketch.

As with all my digital sketches, the first step is to scan my original sketch and adjust the levels so that I can see every star/nuance of the sketch on the computer. To avoid distractions, I crop the scanned image and remove any notes on the scanned image. I then open the appropriate template in PhotoShop and copy and paste the scanned sketch into the template. At this time I also created 3 separate layers: MS (Main Stars), BGS (BackGround Stars), Cluster (for the main star cluster).

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I then center the sketch within the template EP circle, and turn on (make viewable) my other layers. Making the other layers is optional, but I prefer it.

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Now I select the layer that contains the scanned image, and reverse it by reversing the Output Levels in the Levels dialog box as shown:

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Starting with the MS Layer (MainStars), I then select the paintbrush tool and start placing the bright(est) stars on this layer. I toggle the scanned image layer on and off to ensure that I have properly placed all stars as they appear in the scanned sketch. I adjust the brush sizes and opacity to match the stars of the scanned sketch.

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This same process is repeated with the BGS (BackGround Stars) layer, choosing differing brush sizes and opacities until the entire background stars are filled in.

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After I am satisfied with the placement of all the stars on both layers, I then select the Cluster layer. As in my original sketch, this rich cluster of stars actually looked like a very faint blur with a million pin-points of lights floating in it…this being the myriad of stars contained within of course. To try and reproduce this digitally, I selected the Lasso tool and made a free-form outline of the main cluster of stars.

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I then filled this outline with 100% white, and made a copy of this layer. The copied layer was moved below the original and the layer turned off for later use.

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Now, making sure the original Cluster layer is selected, I now apply a Gaussian Blur to the entire layer. As you will note, I basically “blew out” the image entirely using a very high blur setting. This was done to replicate a cloudy, near transparent glow to the region of the sketch.

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As you can see, the blurred layer is spread pretty well across the entire sketch area. We will fix that right now. Remember the copy of the Cluster layer that was made earlier and hidden from view…now it will be used to turn the above blurred layer into the shape more representative of the original sketch. With the blurred layer visible, I moved the mouse pointer to the hidden Cluster layer and pressed the Ctrl key; this allowed me to select the original shape of the hidden layer.

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Now, using the visible Cluster layer, I chose the Select, Feather function from the menu bar, setting the feather at a radius of 10. The feathering is done to prevent a “sharp” edge to the area(s) to be deleted. I then simultaneously pressed the Crtl + Shift + I keys on the keyboard. This reversed the selected area (as we don’t want to delete the selected area) but the surrounding area(s). A quick push of the Del (Delete) key removed the surrounding area(s) and we are now left with a shape more reminiscent of the original.


Now that the Cluster glow is back to its original shape, we now need to reduce the opacity in order to make it look like a faint background glow.


Now a new layer is created, making sure it is above the cluster layer. All the other layers with the exception of the Cluster layer are then turned off (made invisible). Selecting the smallest brush available, I proceed to fill in the area of the visible cluster layer with a 100% white with varying opacities until the entire area is filled in.
NOTE: Just like my original sketch, I knew there were just way too many faint stars to place exactly as they appeared in the EP. I simply placed many of these stars at random, making sure they didn’t become too crowded and that they were well-dispersed.
The dark lanes were also created by using the eraser tool.


Once I got the stars in the cluster placed to my satisfaction, I utilized many tools to give it the appearance that resembled the actual EP view. Among the tools & techniques used were:
Paintbrush tool
Clone tool
Blur tool
Eraser tool
Dodge & Burn tool
Gaussian Blur
PhotoFilter (Sepia 13%)
Noise (monochromatic)


Once I had everything looking the way I wanted. I proceeded to the next step. Referring to my notes, I added color to a few of the stars, ensuring that I colored the correct stars. In this case, I noted the orange stars and selected an orange color that looked realistic. Using the paintbrush tool, I selected a brush size slightly larger that the stars I wanted to add color to. Setting the mode to Hue, and the opacity at 2%, I click the mouse button until the color I want to portray is visible.
NOTE: I always use the feathered brush settings for the main stars. This gives the edges a slight halo, and allows any colors to “fade into” the star and not cover them up.

I then made a copy of the MS (MainStars) layer and placed it below the original MS layer. Now to add a little depth and “pop” to this layer. Making sure the MS Copy layer is selected, I used the Gaussian Blur filter with a setting of 0.75. This throws the copied stars out of focus and adds a gentle glow around the edges of the stars, and gives the stars some depth. The opacity of this layer is then reduced so that it is just barely discernable behind the MS layer.


Next I turn my attention to the BGS (BackGround Stars) layer. Using the Blur tool with a setting of 10%, I then soften any stars that appear too bright (artificial), allowing them to fade into the background and thus adding a little more depth to the overall sketch.


I then make all layers visible, and tweak the various layers as needed until I am satisfied. I then add the pertinent information such as the date, time, EP used, RA & Dec, Cardinal point(s), etc.

Below is the final digital sketch. I hope you like the sketch, and I hope you were able to pick up a tip or two…or at least found it interesting.

Final Sketch:


#3 CarlosEH



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Posted 01 November 2007 - 02:02 AM


I would like to thank you (as I am certain we all do on this forum) for this very informative and educational tutorial on how you processed your outstanding observation of the target of the month (NGC 7789). The steps are clearly delineated and well illustrated. I look forward to your future observations.


#4 pike_fly


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Posted 01 November 2007 - 06:37 PM

Excellent tutorial Wade. You now have me pondering converting my sketchbook to truly digital, rather than just a scanned, inverted library. Nice observation as well, very pretty.

#5 janehoustonjones


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Posted 03 November 2007 - 02:42 PM

NGC 7789 - a lovely naked-eye object, great in binos, spectacular low or high power telescopic object. I like this one, partly because Caroline Herschel discovered it. Actually it's my favorite open cluster.

To me, the dark lanes remind me of a flower opening to reveal the space between petals. I don't usually invert my sketches, but the dark lanes are more showy this way. The original is linked at bottom.

Sketched 10 years ago yesterday, November 2, 1997, Mount Tamalpais in Marin County, CA, the dark sky observing site of the San Francisco Amateur Astronomers. Telescope 12.5-inch f/5.75 Litebox reflector, 9mm Nagler for 202x. I sketch primarily using little 3.5 x 5-inch spiral-bound sketch notebooks, and Faber-Castell 9000 graphites.

- tips there are a dozen or so Caroline Herschel objects visible in the fall sky - it's a fun sketching, and observing project! Also two comets in the vicinity, 17P/Holmes and 8P/Tuttle near Polaris.

- media tried - inverted image - I don't do it often, but like it here.

- mini tutorial - I do almost all of my observing for the public these days, and sketching is hard to combine with that. Now I wait until all the guests are gone before attempting a sketch. But I never fail to pack a 3x5 spiral sketch pad, a skinny set of Faber-Castells, a gum eraser and a pencil sharpener in a small fanny pack. They I'm good to go, sketching wise. On the inside of the graphite pencil box, I have a yellow sticky note and each pencil is identified by writing the degree of hardness (F, 6B, etc.) on the sticky note with that particular pencil. Then a quick look at the sticky note will remind me what pencil sharpness will work for my sketch at that moment.

Original NGC 7789 sketch

An observing report from 2001

Attached Files

#6 CarlosEH



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Posted 03 November 2007 - 04:34 PM


An excellent observation of this spectacular open cluster in Cassiopeia. It must have been a sight in your 12.5" reflector. Thank you for sharing it with us all. I look forward to your future observations on this forum.


#7 Erix


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Posted 07 November 2007 - 10:50 PM

Both are excellent observations and sketches. Thanks for adding them.

Jane, it's good to have you join us! Welcome to CN.

Who's next for adding their target sketch/tips/and tutorials for this object?

#8 WadeVC



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Posted 09 November 2007 - 03:17 PM

Carlos, Lee & Erica, thank you for the kind words! :D

This tutorial was actually quite fun to do, and I may have to do more of them if it helps others here.

#9 stefanj


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Posted 24 November 2007 - 12:22 PM

I really wanted to give this a try- I'm pretty sure I had the right target last night (Of course the near full moon made ID next to impossible- but I knew I was close) However the Temp was only 19 degrees- and every time I took off my gloves my fingers just cramped up!!!! I guess I'll wait till spring gets here (or maybe January will bring a nice warm night of 2- it does happen once in a while)
Love the scetchs I've seen- AMAZING talents here!

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