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How do I do it - Sketching a simple open cluster

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#1 JakeSaloranta

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Posted 24 October 2009 - 10:12 AM

Open Cluster NGC 1664 in Auriga.

Step 1

Once you've located the object, enjoy the view and try to get an overall impression of the cluster. I also prefer to sketch the object so that north is up and east to the left. This is an easy thing to fix later on but I still try to rotate the field so that north is up if possible.

You can use low power to note any specific colors in stars, star chains and so forth.

In NGC 1664's case here are some features that I noticed @ 37x:

1.) Bright 8th magnitude star SE from the cluster.
2.) Five magnitude 10-11 stars in the cluster.
3.) Y-shape of the cluster, resembling that of IC 4665.
4.) Little asterism ~35' NE from the cluster.

#2 JakeSaloranta

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Posted 24 October 2009 - 10:16 AM

Step 2

Find a good magnification. Do not make the object fill the entire field - this (usually) greatly reduces the visual impressiveness of the cluster. Do not sketch the object to a too small field of view - this makes the object (of course) difficult to sketch. A good rule is not to let the object fill more than 1/3 of the field.

For NGC 1664 I selected 96x (31' field of view) on an 8" Orion DSE. This is a fairly good match with the 1/3 rule (cluster's size is roughly 10').

#3 JakeSaloranta

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Posted 24 October 2009 - 10:19 AM

Step 3

There are two ways to do the next step.

First way is to plot and sketch bright stars in the field to use them as reference points. This way you get the field stars and field pretty well cemented to the correct positions but might have some issues regarding the object itself (scale).

The second way is to start with the actual object (and in this case the cluster). I find this way the best for me, although plotting the field stars after the actual object might cause some problems (scale).

So get as comfortable as possible and start sketching. I personally use a chair, headlamp and a ruler while sketching. A ruler is especially helpful as you can use it to accurately mark star positions in a geometrical way.

Also round up the stars if possible.

After step 3, your sketch might look something like this:
Posted Image
Step 3 sketch - primary stars sketched

#4 JakeSaloranta

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Posted 24 October 2009 - 10:21 AM

Step 4

Now you should have a pretty basic outline of the cluster. If you're happy with the result you can move on to start sketching the field stars. If not, I suggest you start over or apply some fixes.

I personally do all of my sketches by combining the views with different magnifications. In this case, NGC 1664 can take magnification pretty well but the suburban sky cannot. I often double the magnification or use over 200x for the next step but on this night seeing wasn't too good so I used only 200x.

Anyway, at 200x you can see the fainter stars more clearly and can bring out few additional stars from the background. Sketching these stars will make the cluster appear richer and sometimes more... inviting. One can argue about the realism of combined sketching but if you're against it, you can always sketch the stars you can see with the primary magnification and leave it to that.

Now, since I do use at least two magnifications on an object when sketching, I've added all the faint stars I could spot @ 200x to the sketch and made sure all of the stars are round.

After step 4 the sketch looks like this:
Posted Image
Step 4 sketch - primary stars + secondary stars @ 200x

#5 JakeSaloranta

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Posted 24 October 2009 - 10:24 AM

Step 5

Next step is the step I find the most difficult. Sketching star clusters that contain geometrical patterns or even some sort of shapes (99% of all clusters do) is pretty easy. I personally try the sketch only the cluster and minimize the amount of extra field stars I have to sketch.

As you can see from the sketch above (step 4 sketch), this is how I visualize the cluster. It hardly is the exact same size that the true physical cluster is and surely is missing some true cluster members... but you can think of this as an artistic impression of NGC 1664.

But the next part is a critical one. You can sketch all the field stars if you want but in my opinion you just end up wasting a lot of time sketching all the stars you can see. How I do it varies depending on the night, my mood and patience.

For argument's sake, I've added more field stars than I usually do. I find it that too many field stars tend to steal away some of the actual cluster's beauty and impressiveness.

This is usually the time when I write down magnification, directions and all other info to the sketching form. After a few days I can hardly remember anything about a specific observing session so it is better to be safe than sorry with the little details.

After the final stage of sketching the sketch looks like this:
Posted Image
Step 5 - The final unscanned version

#6 JakeSaloranta

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Posted 24 October 2009 - 10:25 AM

Step 6

Time to scan the sketch with a scanner, crop it to 400x400. Here is what the unedited, scanned version looks like:
Posted Image
Step 6 - The final scanned version

#7 JakeSaloranta

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Posted 24 October 2009 - 10:26 AM

Step 7

All the sketch needs now is a light touch in Photoshop. Eraser tool takes care of all the excess material in the sketch and a little visit in the "Levels" menu takes care of all the possible color left from the scan and adds a bit contrast to the sketch.

I'm strongly against using any kind of digital editing (Photoshop stars / colors / nebulosity) so none is used.

Here is the final version:
Posted Image
Step 7 - The final sketch

#8 JakeSaloranta

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Posted 24 October 2009 - 10:26 AM

Acknowledgments

Sketching is very rarely this easy. A good sketcher requires endurance and strong will to stay outside for hours just to finish up few sketches. Your hard working sketcher can often be late from school/work, appears red eyed and dead tired in the morning.

Here are some of the typical things I've encountered during my over a decade long sketching career and these are just a few of the things a true sketcher has to endure during sketching:

* Temperatures below -20°C (-4°F)
* High humidity (sketching paper gets soaking wet)
* Stage 1-2 frostbite in your hands/feet
* Steady hands
* Chance of loosing your night's observations in a gust of wind/leaving them to your observing spot

#9 mapofthedead

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Posted 24 October 2009 - 11:26 AM

Very interesting in the fact you use an ink pen to "sketch", I have to say, through experience, pencils work better at -20°C than ink :)

Hands and fingers however, do not :(

#10 Waduino

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Posted 24 October 2009 - 12:17 PM

Thanks for posting this. And how long would you say it takes to sketch an open cluster, like the one used in the demo?
Wad.

#11 JakeSaloranta

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Posted 24 October 2009 - 01:13 PM

And how long would you say it takes to sketch an open cluster, like the one used in the demo?


I think it took me roughly 30-40 minutes to sketch this one. Very time consuming!

/Jake

#12 Jef De Wit

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Posted 24 October 2009 - 02:23 PM

Jake, reading your "way of working" was very interesting. I will think of your "1/3 rule" the next time I sketch a cluster. In the beginning I used more the "1/1 rule"... which gives terrible results. An example to illustrate: NGC 7243 (Caldwell 16). A cluster 30' large in a field of view of 37'!

Attached Files



#13 DNTash

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Posted 24 October 2009 - 11:49 PM

Thanks for posting your process -- very helpful for those of us just getting started with sketching. Where does one find the ready-made sketch pages with the circular field of view?

#14 JakeSaloranta

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Posted 25 October 2009 - 03:38 AM

Where does one find the ready-made sketch pages with the circular field of view?


I've used our deep sky-section's cardboard sketching template from 1998. I think we just got a new copy of these few months ago and there should be a bunch of them in English too. I'll see if somone has a pdf file.

Here's just a simple circle:
Posted Image

/Jake

#15 DNTash

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Posted 25 October 2009 - 04:20 AM

Thanks Jake, very nice of you! A .pdf in English would be great if you can find one -- love to see it. I'm curious as to what all the data points were on the sheet.

Dale

#16 JakeSaloranta

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Posted 25 October 2009 - 05:38 AM

Object
RA
Dec
Magnitude
Size
Epoch
Type (of object)

Sketch (date and time)

Observer
Observing place
Instrument
Magnification
Filter
Field of view
Limiting magnitude
Background brightness
Seeing
Visuality (of the object)
Height (of the object)
Weather

Description

---------------------

My personal html template looks something like this:

Instrument: N203/1200mm Orion DSE
Object: NGC 129 / Collinder 2
Obs. place: Kasiniemi, Padasjoki, Finland
Date: 23/24.3.2006, 16.53
Bortle class: 2 (typical truly dark site)
SQM-L reading: 21.82 (zenith)
NE lim. mag: 7.2 (SE - SAO 122725)
Background sky: 2 (M13 easy naked eye)
Seeing: 2 (slight undulation)
Transparency: 1-2 (stars bright near the horizon)
Sky conditions: Slight sky glow in the N (aurora?)
Weather: Good. -14°C, humidity 71%, N wind 3m/s.

Minimum aperture: <7x50 binocs
Visual impressiveness: 1 (excellent)

Description: bla bla bla.

/Jake

#17 DNTash

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Posted 25 October 2009 - 07:01 AM

Thank you for that list Jake. Much appreciated and helpful. I see now that your original sheet is in what I believe to be Finnish (?). Your personal template is quite thorough on the seeing conditions, which were superb in your example. That must be an incredible site in Finland -- cold, but incredible. My seeing conditions here in the city last night were light polluted, yet fairly good by local standards, but laughable by comparison to the site in your example. Not sure how I'd fill out your template.

Thanks again, and continued clear skies...

Dale

#18 JakeSaloranta

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Posted 25 October 2009 - 07:28 AM

Dale,

Yes the original sheet is in Finnish.

Regarding good seeing conditions in Finland - it happens very rarely. Dark skies but often sea level (bad) seeing.

/Jake

#19 markseibold

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Posted 25 October 2009 - 03:19 PM

Jake

Very nice tutorial :bow: :bow: :bow: I have never been able to bring myself to do just stars only. I will have to try it one day. I still have the Omega Centauri globular in my mind after seeing it in Fiji through a 10.1 Newtonian for several hours one night. As you mentioned cold temps, it was a balmy 80 degrees F at 2 AM in Fiji, so I had no excuse not to sketch; I even bought a pastel chalk or two while there; incidentally they are not impervious to temperature, just a little to humidity [especially the paper.]

I see you indicated two hours to for this sketch. Can you imagine the whole moon in 4 ~ 5 hours? :confused: It is an extremely fatiguing process to say the least.

I look forward to seeing your future observations and sketches,

Mark

www.markseibold.com
My CN Gallery

#20 kraterkid

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Posted 26 October 2009 - 07:45 AM

Super sketch and wonderful description of your technique Jake. I really like the sketch form, it is very easy to read and contains all the pertinent info I'd want, including the equipment, conditions and observation notes. Another fine tutorial for the Best of The Sketching Forum!

#21 FJA

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Posted 26 October 2009 - 02:03 PM

As someone who dislikes sketching open clusters, I found that useful Jake. You make some suggestions I would not have thought of, such as the use of a ruler.

One more thing: how do you get your stars so round? Mine are dreadful, they end up looking like commas sometimes!

#22 JakeSaloranta

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Posted 26 October 2009 - 02:17 PM

One more thing: how do you get your stars so round? Mine are dreadful, they end up looking like commas sometimes!


The very super secret method of round stars is: round them up inside. You never get them round enough in the dark and cold :)

It is also funny to look back in time and check out some old observations. It is funny how much more one can see with little practice and how drawing tecniques have improved over the years...

Here's an example of IC 342:

Posted Image
IC 342 with 3" refractor @ 32x

Posted Image
IC 342 with 4.7" refractor @ 60x

/Jake

#23 FJA

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Posted 26 October 2009 - 02:28 PM

Thanks Jake. Yeah, trying to get them round in the dark is a lost cause! I try and get my sketches right at the scope, but sometimes that isn't possible - what looks good under dim red light may look like a dog's dinner indoors under white light!

#24 CarlosEH

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Posted 28 October 2009 - 08:20 PM

Jake,

An excellent tutorial on how you produce an observation of an open star cluster. This tutorial will help many observers with their own observations. Thank you for sharing it with us all.

Carlos






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