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How to orientate your sketch?

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#1 Jef De Wit

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Posted 14 September 2012 - 02:28 AM

I like to ask your opinion about how to orientate sketches. Since a year I don't post my sketches (lunar and deepsky) done with a refractor like I see them at the EP, but mirror them digitally (to have the right orientation). But I don't turn my drawings with north up. So here are my two questions:

1) When you observe in a telescope with a mirrored immage, is it best to change your sketch to the right orientation?

2) Is it best to put north up, west right (or in the case of lunar sketching east right)?

#2 cildarith

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Posted 14 September 2012 - 09:35 AM

Actually, I don't think it is important at all as long as the orientation (whatever it is) is indicated on the sketch.

#3 Jim Nelson

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Posted 14 September 2012 - 01:33 PM

cildarith is right, but since "up" is meaningless with regards to outer space, I don't see that it matters which way is up. But mirror imaging is an optical artifact, that creates a "mirror isomer" (to borrow a chemistry term) of the real object, and therefore "should" be corrected. This is all personal gut reaction, mind you!

#4 Jef De Wit

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Posted 15 September 2012 - 08:09 AM

Eric and Jim, thanks for your post.

as long as the orientation (whatever it is) is indicated on the sketch

But doesn't north up makes it more easy to compare with other sketches and photographs (like DSS)?

#5 blb

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Posted 15 September 2012 - 09:42 AM

But doesn't north up makes it more easy to compare with other sketches and photographs (like DSS)?


Yes, but it is easier to rotate the sketch to compare my drawing to photographs than it is to rotate my clipboard while making my sketch so north is up. I always make my sketch and then let the target drift out of the field to determine west and then push toward north to determin that direction, which is 90 degrees off of west. I do not try to orient my paper to north and then sketch with the clipboard in a strange position. I find that it is easier to flip and or rotate pictuers in the computer for comparison anyway.

#6 Jef De Wit

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Posted 16 September 2012 - 02:04 AM

to rotate my clipboard while making my sketch so north is up

No, I don't worry about orientation while sketching. It's more easy to rotate them after scanning (with PS).

#7 Jeremy Perez

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Posted 16 September 2012 - 08:25 PM

I'm with Eric that marking a compass rose / cardinal points with the sketch is the main thing for viewers to orient themselves.

After scanning, I prefer to rotate my sketches so that north is up and west to the right. I do this mainly for consistency among my own drawings and to agree with imaging convention. It does make it easier for me to compare differences and similarities to what's been imaged. I think it's especially helpful for double star sketches to quickly compare and relate position angles.

I do agree with your point, Buddy--trying to draw North-Up at the scope would be an enormous pain :) But rotating/mirroring later can be pretty simple if one wants to do that.

#8 blb

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Posted 16 September 2012 - 08:41 PM

I use a sheet that I prepared for making my sketches that includes object data, location of observation, sky conditions, etc., so it would be difficult to rotate/mirror the sketch after scanning with all the information attached to it. Instead I mark west and north on the sketch for reference. When I look up something about the object on the webb and wont to compare it to my sketch, it is much easier to save the picture and rotate/mirror the image for comparison. It never occurred to me to rotate my sketch with all the data that would be lost.

#9 Jef De Wit

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Posted 17 September 2012 - 11:04 AM

Jeremy and Buddy, thanks for your opinion.

#10 Ernest_SPB

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Posted 19 September 2012 - 07:06 AM

Actually, I don't think it is important at all as long as the orientation (whatever it is) is indicated on the sketch.

I do not think so. When you just enjoy with a good picture - any of its orientation is one to you. But when you compare pictures of the same object from different sources some uniform standard in their orientation looks very important for you. It is quite hard to compare sketches with different orientation and even in mirror.

Therefore on paper I draw sketch in orientation that is more convenient in the drawing time, but then before publication I convert scan of the sketch to make north up and west right side. It is much quicker then to write the message.

#11 Jef De Wit

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Posted 19 September 2012 - 07:23 AM

@ Ernest
In your opinion should I rotate an asterisme so that the figure is best visible (instead of north up)?

#12 pdfermat

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Posted 19 September 2012 - 12:06 PM

I haven't recorded directions on my previous sketches, but I want to start. So, (while observing through a reflector) if I allow objects to drift through the field, the direction they are drifting is due west - correct? If so, would north then be 90 deg clockwise from west, or 90 counter-clockwise?

#13 Jeremy Perez

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Posted 19 September 2012 - 01:54 PM

Pat, you are correct that west is the direction of star drift.

The direction of North will depend on how many mirror reflections you have.

Odd number of reflections: North is clockwise from west.
Even number of reflections: North is counterclockwise from west.

You can double check by nudging the scope toward north--stars will enter from the north edge.

#14 Ernest_SPB

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Posted 20 September 2012 - 02:08 AM

In your opinion should I rotate an asterisme so that the figure is best visible (instead of north up)?

It depends...

Some asterismes (like Cr 399) require special orientation to make their names self explaining. In this case its better to publish sketch in this orientation with special note and/or index on the picture.

The exceptions could be fond not only in asterismes. See e.g. my Swan nebula sketch.

Posted Image

Swan figure looks not so obvious in the standard orientation. The same time on original sketch (before rotation) figure of the bird could be seen easily.

Posted Image

I believe it is better to keep for the nebula sketch original orientation, when figure of swan looks better.






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